wastewater treatment, reuse and discharge report 2006 · wastewater treatment, reuse and discharge...

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WASTEWATER TREATMENT,REUSE AND DISCHARGE REPORT 2006

wastewater treatment, reuse and discharge report 2006 1

Contents

From the Managing Director .................................................................................................................................................................................... 3

Introduction ................................................................................................................................................................................................................ 4

Section 1: Commitment to wastewater treatment, environmental protection and recycled water quality ............................................... 5

Section 2: Assessing the sewage treatment system .............................................................................................................................................6Why we treat sewage ................................................................................................................................................................................................................6How we treat sewage ................................................................................................................................................................................................................6How we assess the sewage treatment system .................................................................................................................................................................8Our major treatment facilities ................................................................................................................................................................................................8Sewage treatment plant capacity ....................................................................................................................................................................................... 10

Section 3: Proactive strategies for managing wastewater and controlling recycled water quality ..............................................................11Bulk and trade waste management .................................................................................................................................................................................... 11Infl ow and infi ltration management................................................................................................................................................................................... 11Sewer overfl ow management plan (abatement) ............................................................................................................................................................ 11Buffer zones ..................................................................................................................................................................................................................................12Darwin Sewerage Strategy......................................................................................................................................................................................................12Alice Springs Soil Aquifer Treatment ....................................................................................................................................................................................12Recycled water trials at Marrara ............................................................................................................................................................................................13

Section 4: Operational procedures and process control ......................................................................................................................................14Operational procedures ........................................................................................................................................................................................................... 14Operational monitoring and process control .................................................................................................................................................................. 14Audits and management practices ..................................................................................................................................................................................... 14

Section 5: Verifying wastewater and recycled water quality ............................................................................................................................. 15Wastewater quality monitoring program..........................................................................................................................................................................15Microbiological monitoring (assessment) .........................................................................................................................................................................15Physical and chemical monitoring (assessment) ........................................................................................................................................................... 18Waste discharge licence monitoring summary .............................................................................................................................................................. 19

Section 6: Incident reporting and response .......................................................................................................................................................... 21Background ...................................................................................................................................................................................................................................21Recorded incidents – sewerage systems ............................................................................................................................................................................21Recorded incidents – treatment system (facility) ............................................................................................................................................................21Recorded incidents – odour complaints .............................................................................................................................................................................24Recorded incidents – sewer overfl ows ...............................................................................................................................................................................24

Section 7: Employee awareness and training ...................................................................................................................................................... 25Awareness opportunities and strategies ..........................................................................................................................................................................25Training .........................................................................................................................................................................................................................................25

Section 8: Community engagement and awareness ......................................................................................................................................... 26Introduction ............................................................................................................................................................................................................................... 26Darwin Sewerage Strategy.................................................................................................................................................................................................... 26Water recycling in the Alice .................................................................................................................................................................................................. 26Darwin Harbour Regional Plan of Management ........................................................................................................................................................... 26Bird watching ............................................................................................................................................................................................................................. 26

Section 9: Supporting research and development ..............................................................................................................................................27Chemical sedimentation trials at Ludmilla Wastewater Treatment Plant ............................................................................................................27Hydrodynamic and dispersion modelling of municipal effl uent discharged into Darwin Harbour .............................................................27

power and water corporation2

Contents

Section 10: Documentation and reporting ........................................................................................................................................................... 28Wastewater quality database ...............................................................................................................................................................................................28Documentation ..........................................................................................................................................................................................................................28Reporting ......................................................................................................................................................................................................................................28

Section 11: Evaluation and audit ............................................................................................................................................................................. 28

Section 12: Review and continual improvement ................................................................................................................................................. 29Review .......................................................................................................................................................................................................................................... 29Improvement ............................................................................................................................................................................................................................. 29

References .................................................................................................................................................................................................................30

Appendices ................................................................................................................................................................................................................. 31

Appendix 1:Wastewater treatment performance (assessment) ........................................................................................................................ 31A1.1: Wastewater stabilisation pond (WSP) performance evaluation methodology ........................................................................................31A1.2: Monthly sewage infl ows (ML) for North Region (2005-2006) ......................................................................................................................32A1.3 Monthly sewage infl ows (ML) for South Region (2005-2006) ...................................................................................................................... 33A1.4: Design details for wastewater stabilisation ponds in North Region19 ........................................................................................................34A1.5: Design details for wastewater stabilisation ponds in South Region20 ........................................................................................................36A1.6: Sewage outfl ow (discharge) quality in North Region ....................................................................................................................................... 37A1.7: Sewage outfl ow (discharge) quality in South Region .......................................................................................................................................43A1.8: Performance assessment of wastewater stabilisation ponds against design criteria. .........................................................................45A1.9: Ludmilla Wastewater Treatment Plant performance ...................................................................................................................................... 46A1.10: Yulara Wastewater Treatment Plant performance ............................................................................................................................................47

Appendix 2: Wastewater Discharge Assessment ................................................................................................................................................48A2.1: Wastewater discharge licence evaluation and data presentation .............................................................................................................. 48A2.2: Mass loading discharge data for Berrimah, Katherine, Larrakeyah, Leanyer/Sanderson, Ludmilla and Palmerston Wastewater Treatment Plants ............................................................................................................................... 50A2.3: Discharge concentration and mass loading data for Alice Springs Wastewater Treatment Plant. .................................................. 53A2.4: Summary of the effl uent discharge performance and discharge compliance for Alice Springs ......................................................55A2.5: Comparative representation of discharge water quality. .............................................................................................................................. 56

Appendix 3: Recycled water .................................................................................................................................................................................... 76A3.1: Recycled water site description ................................................................................................................................................................................76A3.2: Recycled water quality assessment methodology and criteria .....................................................................................................................78A3.3: Extract from Guidelines for the use of reclaimed water applicable to uses practised in the Northern Territory ..........................79

Urban non-potable ................................................................................................................................................................................................................................................. 79Urban non-potable ................................................................................................................................................................................................................................................. 79Agricultural ................................................................................................................................................................................................................................................................ 79Agricultural ................................................................................................................................................................................................................................................................80Industrial ....................................................................................................................................................................................................................................................................80

A3.4: General guidelines for salinity of irrigation water............................................................................................................................................. 81A3.4: Recycled water usage (kL) ...........................................................................................................................................................................................82A3.5: Recycled water quality .................................................................................................................................................................................................83A3.6: Salinity classes of recycled water ............................................................................................................................................................................ 84

Appendix 4: Rainfall ................................................................................................................................................................................................. 85

List of fi gures ............................................................................................................................................................................................................86

List of tables ..............................................................................................................................................................................................................86

Abbreviation and defi nitions (glossary) ...............................................................................................................................................................86


I am pleased to introduce Power and Water’s 2006 Wastewater Treatment, Reuse and Discharge Report. This report summarises our performance and achievements in 2005-2006, evaluates our wastewater discharges and water recycling initiatives and assesses the quality of recycled water.

We are proud of our achievements to date, but we continue to improve the way we manage the wastewater generated by Territorians. Increasing environmental pressures mean we are continually challenged to meet more stringent environmental compliance. We have a responsibility to manage our water resources in a sustainable manner to ensure there is suffi cient water and its quality is protected.

While we are committed to conserving resources and protecting the environment through using recycled water, this can only occur if it is done in a safe manner. Protection of public health and safety is and must remain our fi rst priority.

Our trade waste management system ensures that industrial wastewater discharged to our sewers does not limit our opportunities for water recycling, or interfere with our treatment processes or cause environmental harm when we discharge to the environment.

New national guidelines for recycled water were released during the preparation of this report. The principles of these guidelines were considered when preparing this report.

I hope you fi nd this report of interest and value.

From the Managing Director

Kim WoodManaging Director


Every community in the Northern Territory generates sewage. It can come from people’s houses, institutions, commercial premises and industrial businesses and it includes human waste fl ushed down toilets, food scraps washed down sinks, and the water from washing machines, bathtubs, and businesses. Most of the sewage in the Northern Territory is generated by domestic properties. However an increasing amount of sewage is being generated by industry as a result of continued economic development in the Northern Territory. During the Wet Season, infi ltration of rainwater and groundwater increases the volume of sewage.

The sewerage system is part of the urban water cycle. Water is collected from the natural water cycle and used for drinking, cooking, and fl ushing away unwanted wastes. The resulting sewage is collected and treated before either being discharged back to the environment or being reused. At some places the water is allowed to evaporate into the atmosphere.

Power and Water Corporation plays an important role in the urban water cycle. We harvest unused water from the natural water cycle, distribute it to the community, collect the used water and ensure adequate treatment is applied before either returning the water to the natural water cycle or reusing it.

This report focuses on the sewage component of the urban water cycle. It also fulfi ls a requirement of our Waste Discharge Licences issued under the Northern Territory Water Act (2004) to prepare an annual report to present information about monitoring and compliance assessment related to environmental impacts that discharged wastewater may cause, and an assessment of water recycling schemes.

This report assesses the wastewater quality information from July 2005 to June 2006 and subsequently the information is assessed against the requirements of the licences at that time.

Introduction


Power and Water aims to provide a safe and reliable sewage collection network, operate effi cient treatment facilities, release environmentally sound discharges and operate sustainable recycled water systems. Our Customer Contract, our Wastewater Management Policy and our Reclaimed Water Policy outline this commitment. A copy of the Customer Contract is available at any Power and Water offi ce or atwww.powerwater.com.au. We place a high value on protecting and enhancing public health and the environment. Power and Water undertakes to:

• Provide wastewater services appropriate to the environment in which the community is located, to standards in accordance with parameters set by appropriate guidelines.

• Develop a wastewater monitoring program in accordance with the requirements of wastewater discharge licences, monitor the quality of wastewater in accordance with the agreed program, and report annually to the Environment Protection Agency (EPA) program.

• Implement and maintain a wastewater quality management system, consistent with the requirements of relevant national guidelines, to minimise risks to public health and the environment at all points along the collection chain from customer to the environment.

• Ensure that all managers, employees and contractors involved in the collection, treatment and disposal of wastewater understand and implement the wastewater management system.

• Provide a public annual report outlining trade waste management, wastewater treatment effi ciency, reclaimed water quality and wastewater discharge into the environment.

• Develop and maintain a wastewater incident and customer complaint register to benchmark performance and to help identify and resolve wastewater issues.

• Report pollution events associated with wastewater discharges to the environment to the EPA.

• Participate in cooperative research projects with external agencies to identify issues and research priorities for wastewater management in regional and rural areas.

• Annually assess performance with respect to this policy, review our practices in conjunction with the EPA and consult with the community on wastewater management issues requiring attention.

Power and Water promotes the safe, effi cient and environmentally sustainable use of reclaimed water through our Reclaimed Water Policy. Under this policy:• All reclaimed water proposals are subject to the approval of

the Chief Health Offi cer of the Department of Health and Community Services (DHCS).

• The level of treatment, reclaimed water quality and monitoring program will be in line with the National Water Quality Management Strategy Guidelines for Sewerage Systems – Use of Reclaimed Water (2000).

• In conjunction with DHCS, Power and Water will continue to monitor research into the health risks associated with the use of reclaimed water, in particular the results of research associated with unrestricted and indirect potable reuse.

• Direct potable use of reclaimed water is not considered.• Indirect potable use of reclaimed water is considered

possible in the longer term, particularly where water supplies are based on non-renewable, groundwater resources. Any proposal for aquifer storage and recoveryof reclaimed water will be developed in accordancewith the Guidelines on the Quality of Stormwater and Treated Wastewater for Injection into Aquifers for Storage and Reuse – Urban Water Research Association ofAustralian (1996).

• The community will be informed and supportive of any reclaimed water scheme.

• Preference will be given to developing reclaimed water systems that have the potential to result in new industries and jobs for the local community, followed by those that have social benefi ts such as irrigating sporting fi elds.

• Use of reclaimed water is an important component of the total water cycle and will be considered as part of the hydrological cycle.

• Reclaimed water applications may be considered, independently of commercial viability, where signifi cant health, social and environmental benefi ts can be realised through reducing effl uent discharges to the environment.

• Reducing per capita sewage fl ows and substituting reclaimed water for existing water supplies are integral to achieving sustainable water management.

• The supply of reclaimed water for irrigation purposes will require the Department of Planning and Infrastructure and the Department of Natural Resources, Environment and the Arts to approve a land and water management plan that addresses salinity, sodicity, nutrient management and product safety.

Section 1: Commitment to wastewater treatment, environmental protection and recycled water quality


• Implementation of reclaimed water projects will be individually assessed on a commercial basis.

• Preference will be given to customers who can provide an economically and environmentally sustainable demand and be willing to pay for the service.

• Reclaimed water will be supplied at a cost that refl ects the costs in supply. The greater the level of treatment above that required for safe discharge to the environment, the higher the cost of reclaimed water.

• Power and Water will continue to investigate commercial options to overcome constraints to market development of reclaimed water.

• Over time, all existing reclaimed water agreements will be standardised and made consistent with the requirements of the Water Supply and Sewerage Services Act (2000).

• A risk management strategy will be developed for Power and Water’s reclaimed water schemes incorporating product monitoring and quality assurance procedures, as well as monitoring customers’ compliance with reclaimed water controls in accordance with the National Water Quality Management Strategy Guidelines for Sewerage Systems – Use of Reclaimed Water (2000).

• Diversity of reclaimed water use will be pursued as an essential element of minimising commercial risk.

A number of government departments are closely involved with managing wastewater and reusing reclaimed water, working with Power and Water to protect the environment and public health:• DHCS has a key role in providing direction and safeguards

for wastewater quality for reclaimed water schemes as well as public health issues relating to environmental discharges.

• The Northern Territory Environment Protection Agency program grants and controls Waste Discharge Licences and has a role in bulk and trade waste disposal.

• The Department of Primary Industry, Fisheries and Mines provides laboratory analytical services for wastewater and reclaimed water testing in Darwin and Alice Springs.

Section 2: Assessing the sewage treatment system

Why we treat sewageThe purpose of treating sewage is to protect public health and the environment. This is carried out in a manner that fi ts with environmental, economical and social sustainability.

If the sewage is inadequately treated, it may contain:• Organic matter that decomposes, generating foul odours

and lowering the oxygen levels available to animals and plants living in the water

• Numerous pathogenic organisms that cause disease in humans and animals

• Nutrients that stimulate the growth of aquatic plants• Substances that are toxic to plants and creatures living in

the aquatic environment• Substances that restrict certain water recycling practices.The sewage treatment system consists of a collection network of pipes that separate the waste from its source to deliver the sewage to the treatment facility, after which it is either reused or discharged to the environment.

How we treat sewagePower and Water treats sewage throughout the Northern Territory using mostly pond treatment technology or waste stabilisation ponds (WSPs). These are open ponds that use a host of complex, diverse and interrelated natural biological processes to treat the sewage. A combination of aerobic and anaerobic bacteria purifi es the sewage. What sets WSPs apart from other treatment technologies is the involvement of algae that use photosynthesis to generate oxygen. Pond systems are more effi cient in the tropics than in temperate regions and are therefore ideally suited to the Northern Territory. Other treatment processes used in the NT include chemically assisted sedimentation (CAS), dissolved air fl otation (DAF), microfi ltration and activated sludge.

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How we assess the sewage treatment systemTo protect public health and the environment it is necessary to know:• The constituents of concern in the sewage• The impacts these constituents have when discharged to

the environment• The transformations and long-term fate of these

constituents in treatment processes• Treatment methods that can be used to remove or modify

the constituents found in sewage• Methods for benefi cial water recycling of the treated water.The physical, chemical and biological nature of the sewage is determined through Power and Water’s water quality monitoring program (Power and Water 2006b). Many of these measurements are interrelated. We assess process performance and reliability of each treatment facility using the knowledge gained from the water quality monitoring program and measured infl ows and outfl ows. This information is also essential in the design and operation of the treatment facilities. Finally an understanding of the treated water quality is essential to assess the degree of pollution or contamination.

Our major treatment facilities

Adelaide RiverSewage from the town of Adelaide River is treated in a three-pond system. Because of the small infl ow and the high evaporation there is little discharge. These ponds occasionally discharge only during high rainfall.

Alice SpringsSewage from Alice Springs is treated in four sets of ponds, each built at different times. The oldest system lies in the western end of the Commonage. Newer ponds were constructed progressively on the west side of the original pond site.

Effl uent is discharged through evaporation, irrigation at a tree farm and at Blatherskite Park. Excess effl uent overfl ows to Ilparpa Swamp. Overfl ow to Ilparpa Swamp will be signifi cantly reduced when the soil aquifer treatment and storage system is commissioned in late 2007.

BatchelorSewage from the town of Batchelor is treated in a four-pond system. Because of the storage capacity of the ponds and high evaporation rates, no discharge occurs to the environment.

BerrimahThe Berrimah WSPs are a small set of three ponds running in series. Domestic sewage from the suburb of Berrimah and industrial wastewater from the Darwin Business Park is treated here. Discharge is to an estuary.

BorroloolaSewage from the town of Borroloola is treated in a set of three ponds. The effl uent is used to irrigate pasture on site or is allowed to evaporate.

Humpty DooThe Humpty Doo WSPs treat sewage from Humpty Doo. The treated effl uent is sprayed to land near to the ponds.

KatherineSewage from Katherine is treated in a set of nine ponds. The treated water is discharged either to land through irrigation or to the Katherine River. No effl uent is discharged into the Katherine River during the Dry. Discharge to the river occurs only during the Wet Season when it can be mixed with fl oodwaters. The bacteriological quality of the treated water is excellent because the water can remain in the fi nal ponds for extended times. The capacity of these ponds to treat more sewage will be increased through future pond and irrigation extension schemes.


Kings CanyonA four-pond set of WSPs at Kings Canyon treat all the sewage from the Kings Canyon Resort and surrounding community. The treated water is used to irrigate a tree lot on the site. No effl uent is discharged outside the facility.

Leanyer SandersonThe Leanyer Sanderson WSPs are the largest set of ponds in the Northern Territory. They treat most of the sewage from the northern suburbs of Darwin. Two sets of fi ve ponds each operate in parallel. Some of the treated water is pumped to Northlakes where, after more advanced treatment, it is used to irrigate the Darwin Golf Course and the Marrara sporting ovals. The remaining treated water is discharge into the estuary of Buffalo Creek.

LudmillaLudmilla Wastewater Treatment Plant treats sewage coming from Nightcliff, Winnellie and most of the inner city. The treatment process includes grit removal and solids screening, chlorination, and chemical assisted sedimentation. A furnace incinerates the waste solids removed during the treatment process. The furnace also burns sewage gases to minimise odours. The treated water is discharged via a pipeline to Darwin Harbour.

LarrakeyahThe sewage from the CBD and the suburb of Larrakeyah is macerated; that is, larger solids are broken down, and discharged at a deepwater outfall into Darwin Harbour.

The Darwin Sewerage Strategy includes plans to decommission this outfall and transfer the sewage from this catchment to another treatment facility.

NorthlakesThe Northlakes Water Reclamation Plant takes water from the Leanyer Sanderson WSPs for further treatment by more advanced technologies. Chemicals are added to separate solids, mostly algae, from the water. Dissolved air is used to fl oat the solids to the surface of the water where they are removed. Micro-fi ltration then removes fi ne particles to produce water as clear as tap water. The water is used to irrigate the Darwin Golf Course and Marrara sporting ovals.

PalmerstonPalmerston WSPs treat all the sewage from the city of Palmerston. This site also receives some trade waste, mostly grease trap waste, and much of the septic tank waste from the rural and un-sewered areas. A set of fi ve ponds operating in series treats this waste before discharge to the estuary. An additional small pond was constructed to receive and pre-treat the trade waste before transfer to the main ponds.

Pine CreekSewage from Pine Creek is treated in a three-pond set. The water left over after evaporation is discharged only during high rainfall into the nearby creek.

Tennant CreekTennant Creek’s sewage is treated in a set of multiple ponds. All the water evaporates and consequently no effl uent is discharged from the site.

YularaThe Yulara activated sludge plant treats the sewage from the Ayers Rock Resort complex as well as the town. The plant uses mechanical aeration (activated sludge process) to degrade organic matter and to purify the sewage. Effl uent from this plant is polished in a set of ponds and is then used to irrigate an adjacent tree lot. No effl uent is discharged off the site.


f igure 2.1: hydraulic and organic loading of design capacity for wsps

Sewage treatment plant capacityThe treatment capacity of each facility is determined by comparing the actual measured infl ows against the design infl ow. The infl ow is assessed by organic strength (that is, the amount of organic material present in the sewage usually measured as the biochemical oxygen demand or BOD5) and the volume or hydraulic capacity.

The treatment capacity of the major WSPs is shown in Figure 2.1. An infl ow or organic load at 100 per cent signifi es a plant that is operating at or above its design capacity. Loading capacities for Ludmilla and Yulara treatment plants are not shown here. Their treatment capability is discussed in more detail in Appendices 1.6 and 1.7.

Figure 2.1 shows that the Humpty Doo ponds are not large enough to meet the minimum detention time of 20 days and are consequently hydraulically overloaded. Additional ponds are needed to allow the required retention time to reduce pathogens to an acceptable level. Power and Water is planning to build additional ponds at this site and is undertaking other measures to improve the performance of the ponds.

Kings Canyon WSPs are operating near their hydraulic and organic design capacities. Power and Water is planning to build additional ponds at this site as well.

Katherine, Leanyer and Sanderson WSPs are approaching the design capacity and will need upgrading if population projections predict signifi cant growth.

No data was available for Borroloola, Pine Creek, Adelaide River and Batchelor WSPs during this period because there were no fl ow instruments installed or instruments were faulty.

The fl ow meters at Tennant Creek WSPs were not read during this period. Work procedures have since been changed to incorporate meter readings.

More details on the performance of each treatment facility are provided in Appendix 1.

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Power and Water uses several strategies to minimise environmental damage and to protect public health. They include:• Managing bulk and trade waste to control what is put in

our sewers• Managing infl ow and infi ltration to control excess

sewer fl ows• Using overfl ow management plans to control where and

how sewer overfl ow may occur• Minimising the impacts of odours and aerosol

emission from treatment plants through buffer zones around facilities

• Implementing the Darwin Sewerage Strategy• Treating wastewater through the Alice Springs Soil Aquifer

Treatment initiative• Trialling recycled water management programs.

Bulk and trade waste managementPower and Water has entered into Bulk Wastewater Agreements with a number of Northern Territory waste management companies. Under the agreements, the companies collect wastes such as grease trap waste, septic tank waste and shipping wastewater for discharge to approved treatment plants across all regions of the Territory. This ensures they are disposed of correctly and not discharged untreated to the environment. The volume of waste received has doubled over the past two years. This indicates that the stringent maintenance procedures for businesses generating trade waste are working effectively.

Under the Trade Waste Management System (TWMS), over 600 compliant businesses have now been issued with a Trade Waste Discharge Permit. A further 100 businesses have completed applications to discharge trade waste to sewer. These businesses will be issued with permits when their trade waste discharge complies with the TWMS. Trade Waste Offi cers will continue to work with and assist all businesses to achieve compliance.

The permits specify the maintenance frequency for the businesses’ pre-treatment equipment. Recording procedures implemented under the Bulk Wastewater Agreements allow Power and Water to ensure maintenance is undertaken as specifi ed.

The discharge of food scraps and waste cooking oil to sewer is overloading pre-treatment equipment and placing an additional unacceptable load on the sewerage system. Power and Water will initiate an information campaign including

personal contact and brochures to try to reduce the volume of unapproved waste products discharged to sewer.

Power and Water has recently negotiated an agreement with a major customer to accept both bulk wastewater and trade waste from the new biodiesel plant at East Arm. The wastewater will be stringently monitored to ensure compliance with the discharge criteria in the agreement. This will ensure wastewater discharged to the environment complies with licence conditions.

Infl ow and infi ltration managementDuring heavy rainfall the volume of wastewater fl owing through the sewers can increase greatly.

Every year Power and Water runs an extensive advertising campaign to inform the public not to direct rainwater from downpipes or properties into overfl ow relief gullies. Because this can overload the sewerage system and cause overfl ows into other properties, we regularly undertake smoke testing to identify illegal connections.

Vegetation also has a strong impact on infl ow and infi ltration. Many exotic and native trees seek out the moisture in sewer pipes during the Dry Season. The roots can break pipe joints allowing infi ltration and causing blockages. Power and Water manages tree roots through herbicide and physical removal.

Sewer overfl ow management plan (abatement)Sewer blockages, sewer collapse, pump station failure or excessive infl ow and infi ltration cause overfl ows. Our ongoing sewer rehabilitation program spends around $2 million annually to ensure continued sewer integrity and to reduce stormwater and groundwater infi ltration. The program uses closed circuit TV to identify problem sewers and areas where repair is most needed.

Power and Water owns and operates about 60 per cent of the wastewater collection system. Because the remaining 40 per cent is within property boundaries, landowners are responsible for repairing and maintaining their sewer connections. This limits some of our ability to control infl ows. One component of our Trade Waste Management System is to reduce grease build-up (and thus blockages) and we try to manage trees and vegetation close to sewer pipes. Unfortunately, it is likely that sewer overfl ows will always occur at some time. We try to manage overfl ows so they occur where they will cause minimal impact, and we respond to any incident as quickly as we can.

Section 3: Proactive strategies for managing wastewater and controlling recycled water quality


Buffer zonesA buffer zone is an area of land around a sewage treatment facility, disposal or transfer facility such as a pumping station that remains free of development. Buffer zones are designated to:• Minimise nuisance odours and noise in built-up

residential areas• Minimise people’s exposure to wastewater aerosols

generated during irrigation• Reduce the visual impact on the environment• Protect Power and Water interests by restricting

development close to sewage facilities.

Buffer zones depend on the size and type of the facility.

Power and Water draft guidelines (Power and Water 2006c) stipulate the minimum buffer zones around sewage treatment works, areas of treated effl uent reuse and sewerage pumping stations in the Northern Territory.

Darwin Sewerage StrategyThe Darwin Sewerage Strategy was fi rst developed in 1994 focusing on the central Darwin area including the CBD, Parap, Fannie Bay, Ludmilla and Stuart Park areas. It aims to:• Operate a waste treatment and disposal network that

conforms to nationally accepted environmental standards and accepted best practice

• Increase sewer capacity to handle continued population and industrial growth

• Reduce system overfl ows during high rainfall• Reduce the impact of effl uent discharges to Darwin Harbour• Generate increased opportunities for effl uent reuse.

In 1994, the main feature of the strategy was to close the Larrakeyah outfall and to upgrade Ludmilla Wastewater Treatment Plant to treat the diverted sewage fl ows, with much of the treated effl uent used to irrigate open space in the inner city.

The strategy has progressively been implemented and is currently going through a major review. An estimated $14 million of capital works has been spent to upgrade the sewer reticulation system in the CBD, Frances Bay and Parap as well as progressive upgrade of Ludmilla Wastewater Treatment Plant to improve safety and reduce odours. The major works remaining to close down the Larrakeyah outfall include the fi nal diversion of the sewage from Larrakeyah to Ludmilla and upgrade of the treatment facility at Ludmilla. This work will require a minimum of fi ve years to complete.

Since development of the strategy over 10 years ago, several economic, environmental and engineering issues have been identifi ed, including:• The strategy did not establish a well-defi ned basis to

determine the quality or quantity of an acceptable discharge. In addition water quality objectives, associated with declared benefi cial uses, have not been set for Darwin Harbour.

• There were several technical, land administration issues and community objections associated with the proposed diversion tunnel.

• Identifi cation of poor foundation conditions at Ludmilla has escalated costs for new structures.

• Odours need to be captured at the Ludmilla facility so nearby residents do not object.

• The estimated cost of the project now exceeds two and half times the original estimates.

Due to these factors several alternative options are now being considered to manage the diverted sewage that will result from closing the Larrakeyah outfall.

Alice Springs Soil Aquifer TreatmentEffl uent regularly discharges from the Alice Springs WSPs into the Ilparpa Swamp, changing it from an ephemeral to a permanent water body. The nutrient rich effl uent has contributed to the growth of non-native grasses and reeds in the swamp, degrading the original Coolabah swamp, as well as providing a habitat for mosquitoes. Consequently, in late 2005, Power and Water implemented a pulse discharge regime to the swamp to disrupt the mosquitoes breeding cycle. Mosquito numbers have dropped dramatically and remain low.

To eliminate the dry weather effl uent discharges from the treatment ponds to the swamp, Power and Water will implement the soil aquifer treatment (SAT) scheme by December 2007. The scheme incorporates a dissolved air fl otation and fi ltration plant to further improve the quality of the water taken from the ponds, making it suitable for irrigation in horticulture. The reclaimed water will then be transported 8km via an existing pipeline for SAT at the Arid Zone Research Institute (AZRI). The water will be stored underground and subsequently used to irrigate fruits, vegetables, fl owers and ornamental plants.

Once the SAT is commissioned and fully operational, no discharge is expected except possibly during wet weather.

About half of the total fl ow into the treatment ponds is lost to seepage from the unlined treatment ponds and channels. This has created a groundwater mound that lies under the


sewage ponds and the irrigated tree plantation. The elevated groundwater levels have raised the water table in the swamp, compounding the effects of the surface discharge. Power and Water has developed a groundwater monitoring plan as required by Waste Discharge Licence to specifi cally determine the impact of the sewage treatment system and reuse activities on groundwater levels and quality.

Recycled water trials at MarraraPower and Water operates the Northlakes Water Reuse Scheme in Darwin to supply recycled water. The Marrara Sporting Complex was supplied with secondary treated effl uent from the Leanyer Sanderson Waste Stabilisation Ponds to irrigate sports fi elds. The Darwin Golf Course is irrigated with micro-fi ltered recycled water from the Northlakes Treatment Plant. In September 2005 Power and Water conducted a trial to determine if it was feasible to supply micro-fi ltered recycled water to both the Darwin Golf Course and the Marrara Sporting Complex. The trial found that:• The treatment plant does not have the capacity to supply

additional demand from Marrara• Water from the drinking water system is required to

supplement 28 per cent of the recycled water supply• The micro-fi ltered water costs $0.74/kL to deliver to Marrara,

similar to the cost of the drinking water supply.

Power and Water is currently reviewing its options for supplying irrigation water to the Marrara Sports Complex without the need to top up the supply from the drinking water system. We are also reviewing our price for the supply of the recycled water.

essential services operators.


Section 4: Operational procedures and process control

Operational proceduresPower and Water continually develops and reviews standard operating procedures and guidelines so operators have the tools and knowledge they need to effectively run wastewater collection and treatment systems. Our standard operating procedures include:• Pollution event reporting and response• Wastewater quality sampling and testing• Wastewater stabilisation pond design and operation• Specifi c operating procedures for individual

treatment plants.

Power and Water is aiming to implement an integrated management system in line with the three recognised International and Australian Standards for Occupational Health and Safety Management Systems (AS/NZ 4801), Environmental Management Standards (AS/NZ 14000)7, and Quality of Products and Services (ISO 9000). It is designed to focus on the process of continuous improvement. During 2005-2006 we reviewed our procedures so that the format is compatible with requirements8.

Operational monitoring and process controlOur aim is to continually improve all aspects of treatment plant and collection system monitoring and process control. Many of the more complicated treatment systems have built-in process control systems that monitor and provide real-time feedback on chemical and hydraulic processes and provide alarms when necessary. In most cases this information is collected remotely so operators can assess the problem from a central location.

Power and Water has been developing sewerage system models throughout the Northern Territory to enhance planning and decision-making. Sound models are necessary to assess alternative strategies, for example how to divert fl ows away from the Larrakeyah outfall to the Ludmilla treatment plant in Darwin. Models are also used to assess the impact of new building developments on operating sewerage systems, and to determine if upgrades are required.

Audits and management practicesPower and Water supports the use of recycled water and takes its responsibility seriously when it comes to safety and customer compliance with any restrictions on its reuse. Power and Water undertakes system audits to ensure that the management of all reclaimed water schemes complies with specifi c requirements.

Power and Water has produced a customer information handout called Applying reclaimed water for irrigation schemes: Management and safeguards, which outlines the safeguards and controls that a customer must implement to prevent public exposure to pathogens (disease-causing microorganisms) and other contaminants. Controls include restricting public access, putting in place buffer distances, using a suitable irrigation method, ensuring properplumbing (using lilac coloured coded pipe for transporting recycled water) and putting up the appropriate signage(as shown below).

7 ISO 14001 specifi es the requirements for an Environmental Management System (EMS), providing a framework for an organisation to identify and manage the environmental impact of its activities, products and services, and to improve its environmental performance continually.

8 ISO 9001:2000 specifi es requirements for a quality management system for any organisation that needs to demonstrate its ability to consistently provide product that meets customer and applicable regulatory requirements and aims to enhance customer satisfaction. The standard is used for certifi cation/registration and contractual purposes by organisation seeking recognition of their quality management system.


Wastewater quality monitoring programPower and Water has developed a wastewater quality monitoring program (Power and Water 2006b) to verify the performance of current wastewater quality management strategies. The need for establishing a regular monitoring program is both regulatory and process driven and is based on:

• Guidelines for the Use of Reclaimed Water (National Water Quality Management Strategy 2000a)

• Waste Discharge Licences issued by the Department of Natural Resources, Environment and the Arts (EPA program) under the Water Act (2004)

• National Pollution Inventory reporting requirements• Power and Water’s treatment performance assessment

criteria (self assessment).The program is reviewed annually and revised as required.

Microbiological monitoring (assessment)Microbiological monitoring is undertaken to check for potential pathogenic or disease-causing organisms. It is recognised that the major risk to people using recycled water is infection from microorganisms. Sewage contains many potentially infectious microorganisms derived from humans.

The coliform group of microorganisms consists of several genera of bacteria found in the gut of animals. They are discharged in high numbers in human and animal faeces.

These coliforms are generally harmless. Because there are a lot more coliforms in human faeces than pathogens, they are useful as an indicator of faecal contamination in water. They are one of the best indicators of water treatment effi ciency and are consequently very useful for assessing the safety of recycled water.

Escherichia coli (or E.coli) is one of the main members of the faecal coliform group of bacteria living in the lower intestine of mammals. E.coli is more specifi c to human sources of contamination and is preferred when assessing faecal contamination.

E.coli is reported as colony forming units (cfu) per 100 mL of water.

The Guidelines for the Use of Reclaimed Water (National Water Quality Management Strategy 2000a) addresses how to recycle effl uent coming from municipal sewage treatment facilities. They outline the different applications of water recycling, the level of treatment required, the recycled water quality required for each application, the water monitoring that should be put in place and the safeguards and controls.

In 2005-2006, Power and Water provided about 1750 million litres of recycled water, or about 10.9 per cent of the effl uent generated at major sewage treatment facilities in the Northern Territory. Table 5.1 summarises where we supplied recycled water and how it was used.

Section 5: Verifying wastewater and recycled water quality

scheme application recycled water type9

volume

recycled (mL)

Northlakes Darwin Golf Course Municipal with uncontrolled public access 228

Marrara Marrara sports ovals Municipal with controlled public access 99

Humpty Doo Natural vegetation Agriculture: Non-food crops 36

Ludmilla In-plant processes Industrial: Open system with human contact possible <110

Pine Creek Sports oval & rail corridor Municipal with controlled public access 011

Katherine Cattle feedlot Agriculture food production pasture and fodderfor cattle.

153

Blatherskite Park Open space & sports ovals Municipal with controlled public access 1070

Alice Springs Tree lot Agriculture: Non-human food chain 150

Kings Canyon Tree lot Agriculture: Non-human food chain 7

Yulara Tree Lot Tree lot Agriculture: Non-human food chain 012

Table 5.1 Summary of recycled schemes in the Northern Territory

9 As described by the Guidelines for Reclaimed Water (National Water Quality Management Strategy 2000a)10 Only a small amount of water is now recycled in processes at Ludmilla treatment plant following discontinued use of the furnace to burn sludge.11 Scheme has been closed down12 Yulara scheme discontinued after fi re destroyed the tree lot.


f igure 5.1: median e.coli values in recycled water used with controlled public access

Appendix 3 provides more detail about each scheme in the Northern Territory.

Figures 5.1 and 5.2 show the median and 80th percentile of E.coli measured at all sites with controlled public access. Where the laboratory reported a value of <20 cfu/100mL, a value of one half the detection level was assumed as the shown value.

Because the water recycling facilities at Pine Creek need a signifi cant upgrade, no recycling is being undertaken until this occurs. However the water quality results are presented for reference purposes.

ccfu

/100

ml

f igure 5.2: 80th percentile e.coli in recycled water with controlled public access

ccfu

/100

ml


Except for the water being stored in the golf course pond at Northlakes, the recycled water used in applications with controlled public access is of acceptable quality. The water quality in the golf course is of marginal quality being at the guideline value. This water in the golf pond is further treated using dissolved air fl otation (DAF) and microfi ltration to produce water with very low E.coli levels. This water is used for irrigation and is shown as Darwin Northlakes (Filtered water).

Figures 5.3 and 5.4 show the median and 80th percentile of E.coli measured at water recycling sites where the water is used for non-human food chain agriculture irrigation.

f igure 5.3: median e.coli in recycled water used for non-human food crops

ccfu

/100

ml

f igure 5.4: 80th percentile e.coli in recycled water used for non-human food crops

ccfu

/100

ml


These fi gures show that the recycled water from Humpty Doo struggles to meet the guideline criterion for its intended use. Figure 2.1 shows that the ponds at Humpty Doo are hydraulically overloaded meaning that there is insuffi cient detention time in the ponds to effectively reduce the numbers of indicator organisms. Power and Water is currently undertaking investigations to improve the treatment. Options being considered include building additional ponds, and installing recirculation systems and aeration systems.

The previous report (Power and Water 2005) identifi ed that the recycled water used to irrigate the tree farm at Alice Springs was not complying with the Guidelines (National Water Quality Management Strategy 2000a). Modifi cations to operations of the facility seem to have improved the quality of the treated water.

The guidelines (National Water Quality Management Strategy 2000a) and the Department of Health and Community Services have recommended the frequency to monitor recycled water quality. Mostly suffi cient samples were collected (Table A3.5) but in some cases this target sampling frequency was not met. This was due to several reasons including:• No fl ows occur for some months in the Dry Season at

Humpty Doo• No samples were collected specifi cally from the recycled

scheme because the scheme was discontinued such as at Yulara and Pine Creek. However the water quality results from the treatment facilities are presented here for reference purposes

• Remote sites make it diffi cult at times to collect all samples and to send them to the laboratory in a timely fashion.

Physical and chemical monitoring (assessment)Various physical and chemical measurements are carried out on the wastewater, treated water and recycled water. These measurements are important because they provide an indication of the potential impact the wastewater may have on the environment through wastewater discharges. These measurements also allow us to predict and assess the effi ciency of the treatment processes as well as determining the impacts of recycled water on the health of plants and the structure of the soil.

Most physical and chemical measurements are recorded in milligrams per litre (mg/L).

The following sections provide a brief summary of the typical physical and chemical measurements that are carried out on the wastewater. Table 5.2 compares the typical composition of raw sewage in the Northern Territory with values reported in the literature.

Generally the sewage in the Northern Territory tends to be organically weaker than that reported in the literature. This is possibly due to several reasons including:

• Infi ltration of groundwater and stormwater into the sewer• People take more showers due to the warm climate. The

increased volume of shower wastewater contains less organic matter than toilet water

• Few trade waste generators such as food processors discharge their waste to the sewer.

Biochemical Oxygen Demand (BOD5)The BOD5 determination measures the amount of oxygen needed by bacteria to consume organic matter in the water over fi ve days. This test allows us to predict the organic waste loading to the treatment plant and to evaluate the BOD-removal effi ciency for such treatment systems.

NutrientsNutrients such as phosphorus and nitrogen are essential to the growth of all organisms, however excessive nutrients in natural waters may stimulate the excessive growth of photosynthetic plant and algae.

Phosphorus is usually measured as both the total and fi lterable (soluble) forms because the soluble form is most readily available to plants.

In wastewater the forms of nitrogen of greatest interest are nitrate, nitrite, ammonia and organic nitrogen. All these forms of nitrogen are biochemically interchangeable. During biological treatment processes ammonia and organic nitrogen are converted to nitrate and nitrite. These forms are readily available to plants. Biological sewage treatment processes, if the correct conditions are maintained, can convert the nitrate and nitrite to nitrogen gas, which is then lost to the atmosphere. Total Kjeldahl Nitrogen (TKN) is a measure of the ammonia and organic nitrogen. Organic nitrogen comes from proteins found in our food, which is the largest source of organic nitrogen.

Ammonia is very toxic to most aquatic animals.

Suspended solids (SS) and volatile suspended solids (VSS)Solids refer to matter suspended or dissolved in water or wastewater. The suspended solids are the portion of total solids retained by a fi lter. Volatile solids is the loss of weight when the suspended solids are ignited at 550°C. The determination of volatile solids is useful because it offers an approximation of the amount of organic matter present in the solid faction of sewage.

Algae are very common in waste stabilisation ponds and can contribute signifi cantly to the suspended solids.


Total dissolved solids (TDS)Total dissolved solids is a measure of the amount of dissolved matter in the water. The dissolved solids in sewage come from the water supply, chemicals used in the home such as detergents, food and industrial trade waste discharge to the sewer. TDS is useful for assessing if the quality of the sewage changes. It can also be used to estimate the amount of salts in the water and is helpful for assessing if the treated water will affect the structure of soils or plant growth when used for irrigation.

measurement median

(minimum-maximum)

literature

BOD5 (mg/L) 110 (21 –635) 200 – 350

SS (mg/L) 210 (26 – 1400) 200 – 350

Ammonia (mg/L N) 32 (10 – 69) 24 – 53

Organic nitrogen (mg/L N) 12 (2 – 33) 12 – 27

TKN (mg/L N) 44 (15 – 87) 35 – 75

Total phosphorus (mg/L P) 8.9 (2.3 – 22.6) 8 – 25

pH 7.3 (6.8 – 8.0) 6.8 - 7.6

E.coli (cfu/100mL) 1.1 x 107 >106

Table 5.2 Typical composition of domestic sewage in the Northern Territory compared to the literature13

Waste discharge licence monitoring summaryThe Environment Protection Agency program issues Waste Discharge Licences under the Water Act (2004), which requires Power and Water to measure the quantity and quality of discharges. Power and Water has seven discharges as outlined in Table 5.3. New discharge licences were issued in October 2006. This report assesses information from July 2005 to June 2006 and consequently the information presented is assessed against the requirements of the licences at that time.

The discharge licences require Power and Water to regularly measure the concentration of each of the previously discussed measurements and to estimate the total annual amount (or load) discharged to the water bodies in the Northern Territory. Table 5.3 summarises these discharges. Tables A2.2 and A2.3 provide monthly details.

In addition, the National Pollution Inventory (NPI) requires service facilities to report on the emission of certain substances to the environment. For sewage, NPI-listed substances include ammonia, total nitrogen and total phosphorus.

13 Metcalf & Eddy (2003)


Table 5.3: Annual environmental mass loading as required by Waste Discharge Licences

discharge location

waste

discharge

licence

number

suspended

solids

(tonnes)

volatile

suspended

solids

(tonnes)

ammonia

(tonnes)

total

kjeldahl

nitrogen

(tonnes)

total

phosphorus

(tonnes)

bod5

(tonnes)

Berrimah WDL 69 24.9 23.1 0.69 3.78 1.37 6.63

Katherine WDL 73 30.6 30.1 1.08 4.94 1.42 28.3

Larrakeyah WDL 70 275 253 36.5 57.6 12.1 191

Leanyer Sanderson WDL 72 717 599 12.2 78.8 42.6 241

Ludmilla WDL 71 482 332 87.6 122 28.1 287

Palmerston WDL 68 181 170 40.1 69.1 17.8 62.3

Alice SpringsEP7 outlet

WDL 139 36.3 33.3 0.56 4.77 1.44 15.8

Alice SpringsEP10 Outlet

WDL 139 96.3 83.4 0.37 9.59 2.18 20.9

Alice SpringsPonds B/C outlet

WDL 139 0.28 0.22 0.06 0.10 0.03 0.16


Section 6: Incident reporting and response

BackgroundPower and Water recognises it should respond rapidly and appropriately to pollution incidents or emergencies that can threaten public health or cause environmental harm.

A pollution incident is any event that causes or threatens to cause harm, adverse effect, or nuisance on the environment.

Following a pollution incident, Power and Water immediately ensures the area is made safe by controlling and containing the overfl ow, where it is practicable and safe to do so. Once the overfl ow is controlled, staff report the incident to Power and Water’s Environmental Service personnel. The report includes:

• The date, time, duration and volume of the overfl ow• The location of the incident• Reasons for the incident (if known)• Controlling actions undertaken• Personnel involved• Any other information that may be relevant.

The Environmental Services staff may also seek further information from other personnel and inspect the site to ensure any corrective or preventative action is implemented in a timely manner. Information about the incident is recorded in Power and Water’s incident database and a report provided to senior management.

Recorded incidents – sewerage systemsIn 2005-2006 only one environmental incident involving wastewater was referred to the Environment Protection Agency (EPA) program.

Recorded incidents – treatment system (facility)The infl ow to sewage treatment plants can vary considerably from the average dry weather infl ow to the peak wet weather infl ow. Typical infl ow during wet weather may be three to fi ve times the average fl ow. In Darwin the high intensity rainfall associated with the Wet Season may increase the fl ow tenfold. The reasons for the high fl ow and our management strategy to reduce it are outlined in Section 3.

During 2005-2006 no environmental incidents involving treatment systems in the major urban centres were referred to the EPA program. Waste stabilisation ponds are ideally suited to highly variable infl ow. Their large volume and long detention time can resist the shock loading during wet weather.

incident number date location description cause

1 8 March 2006 Coconut Grove Unknown volume of raw sewage

Pump and alarm failure

Table 6.1: Recorded incidents of sewerage overfl ows reported to EPA14 program.


The Ludmilla Wastewater Treatment Plant uses chemical assisted sedimentation (CAS) to treat the sewage. The effectiveness of this treatment process greatly depends on the concentration of the chemicals added to help settle out the solids in the sewage. If the fl ow increases greatly the concentration of the chemicals would be too low to be effective for settling the solids. Consequentially, the Ludmilla plant is less able to effectively treat the sewage when the infl ow varies greatly. Figure 6.1 shows the average daily fl ow pattern.

The capacity of the Ludmilla plant is about 10 000 kilolitres per day, however it can adequately treat infl ow up to about 30 000 kilolitres per day. During extreme rainfall, there are periods when the capacity is exceeded. During these times, it is necessary for fl ows to bypass the treatment process and discharge directly to Ludmilla Creek. When these events do occur, the untreated sewage is highly diluted by rainwater that has entered the sewage network. In 2005-2006 there were no recorded untreated discharges into Ludmilla Creek.

Apart from wet weather overfl ows, treated wastewater must sometimes be discharged into Ludmilla Creek rather than passing through the normal discharge at East Point. This occurs when infl ows are high, a pump breaks down or a pipe blocks. Figure 6.2 summarises these events.

f igure 6.1: daily inflow to ludmilla wastewater treatment plant

Daily

infl o

w vo

lum

e (kL

)


figure 6.2: treated overflows to ludmilla creek

The quality of this discharge is reported in Appendix A1.4. The following table summarises all discharges to Ludmilla Creek during 2005-2006.

description of

overf low

untreated

plant by-pass

treated plant

overf lows

untreated

plant by-pass

treated plant

overf lows

untreated

plant by-pass

treated plant

overf lows

Overfl ow events (days)

0 167 0 153 12 142

Discharge volume (kL)

0 579 526 0 182 526 2162 484 719

Table 6.3: Untreated and treated overfl ows to Ludmilla Creek

Treated plant overfl ows to Ludmilla Creek represented about 12.2 per cent of the total discharge from Ludmilla Wastewater Treatment Plant. Treated overfl ows of less than 100 kL contributed about 36 per cent (or 60) of the total number of treated overfl ow discharges but only contributed 0.3 per cent of the total treated overfl ow volume discharged and 45 per cent of treated overfl ows with fl ows between 100 to 5000 kL discharged 101,910 kL or 17.7 per cent of the total treated overfl ow discharged. However, 19 per cent or 31 of the treated overfl ows discharged 82 per cent or 475 852kL of the total overfl ow volume discharged. The high overfl ow events occurred during late January 2006 (seven events) and March-April 2006 (24 events) during high rainfall.

Daily

infl o

w vo

lum

e (kL

)


f igure 6.3: sewage odour complaints

in the darwin area 2005-2006

Recorded incidents – odour complaintsPower and Water received 28 odour complaints in the Darwin region in 2005-2006. The number of complaints by suburb is shown in Figure 6.4. Table 6.4 compares the number of odour complaints with previous years. Complaints are registered in a database and investigated. Common causes of odour complaints are grease and fat build-up in the sewer and septic or stagnant sewage as a result of a sewer blockage. These are normally corrected by high pressure cleaning of the sewer lines.

year 2006 2005 2004

Number of complaints 28 43 34

Table 6.4: Number of sewage odour complaints in Darwin area 2006 - 2004

Recorded incidents – sewer overfl owsFigure 6.4 shows the location of 44 sewerage overfl ows from manhole covers that private landowners reported to Power and Water. These overfl ows usually occur on private property and were caused by either excessive stormwater ingress or the main pipe being blocked.

f igure 6.4: sewage overflows reported

to power & water 2005-2006


Section 7: Employee awareness and training

Power and Water is committed to ensuring that all employees are appropriately trained and are aware of their responsibilities. In working with wastewater where the employee’s and the community’s health is at risk, there is no room for compromise.

Awareness opportunities and strategiesWe use several strategies to ensure staff appreciate and develop awareness of the way their duties impact on wastewater and recycled water quality. These strategies, which are also used to develop skills and knowledge, include:• Monthly section meetings• Periodic “toolbox” meetings of work groups• Rotation of staff to other sections and centres• Management feedback sessions• Support for further education of employees• Employee training programs derived from individual

development plans• Development and implementation of job models for

service workers.

TrainingSeveral operational activities may adversely affect sewage collection, transfer, treatment and discharge if not performed correctly. We continually review and update our procedures as new equipment or techniques develop. Safety training is a high priority and includes training in:• Handling dangerous goods and chemicals such as chlorine

and lime• Operating self-contained breathing apparatus• Entering confi ned spaces• Performing rescues from pump wells and trenches• First aid• Cardio-pulmonary resuscitation• Fire and emergency evacuation• Managing unauthorised access situations• Operating dangerous equipment in public places• Electrical isolation, tagging and lock out procedures• Two-way radio procedures.

Our staff or agents who sample wastewater in centres across the Northern Territory also require training to ensure successful sampling and testing. We have developed a booklet for all wastewater samplers and provide initial training and refresher courses. In smaller centres, the agents are often employed by the Local Government Community Council and are referred to as Essential Service Offi cers or ESOs.

Other broader skills training, such as the Public Sector Management Program, frontline management initiatives and service worker job model related training, is also important because it develops skills for effective management and completion of job responsibilities.


Section 8: Community engagement and awareness

IntroductionWe see community engagement and awareness of wastewater issues as a high priority. We would like the community to:• Understand issues associated with wastewater and

recycled water• Help us minimise impacts of wastewater discharge by

adhering to regulations associated with trade waste and stormwater discharge

• Improve their confi dence in how we treat and discharge wastewater and how we use recycled water

• Participate in decision making to develop strategies for managing sewage discharges and using recycled water.

Darwin Sewerage StrategyThe community is kept well informed of the progress of the Darwin Sewerage Strategy and seems to welcome progress to close the Larrakeyah outfall. The community seems also supportive of any water recycling initiatives associated with the Strategy. Power and Water continues to modify its communication plan as the Darwin Sewerage Strategy continues to be revised.

Water recycling in the AliceThe Water Reuse in the Alice scheme has been developed to enhance sewage treatment, discharge and water recycling opportunities to the township of Alice Springs. This project was developed from the community’s expectation that the treated sewage be put to the highest value use possible and not lost to evaporation or discharged to the Ilparpa Swamp (Power and Water 2006d). Consequently we had numerous public presentations and open days at key sites. We have actively encouraged and welcomed community involvement in the environmental approval process associated with this project and will continue to do so.

Darwin Harbour Regional Plan of ManagementWe participated extensively in the preparation of the Darwin Harbour Regional Plan of Management including providing public presentations. Power and Water fully supports the plan, in particular the intent to improve the understanding to the region’s environment and the protection and enhancement of freshwater, estuarine and marine water quality.

Successful strategies to reduce the impacts of sewage and stormwater on Darwin Harbour should focus on key contaminants and on priorities for management, which should be based on the measurement of the major infl ows. At the same time a successful strategy would value the community’s vision of their local environment.

Power and Water is developing fact sheets and kits to inform the wider community of issues affecting Darwin Harbour region and management measures to address issues.

This report, and the information in it, is part of Power and Water’s contribution to meet the challenges associated with understanding and delivering sustainable waste management around Darwin Harbour.

Bird watchingWe are proud to support public bird watching activities at the Leanyer and Alice Springs waste stabilisation ponds (WSPs). Several ornithology books note both sites for their diversity of bird life. At the Alice Springs WSPs, bird hides; interpretive signs and a purpose-built bird-nesting island have been constructed.


Section 9: Supporting research and development

We are involved in a number of research projects that aim to improve our management of wastewater and our recycled water quality. In some projects we carry out the research in-house; however, we mostly conduct the research in partnership with research organisations such as Charles Darwin University or Cooperative Research Centres such as the CRC for Water Quality and Treatment.

Chemical sedimentation trials at Ludmilla Wastewater Treatment PlantAs part of the Darwin Harbour Regional Plan of Management and the Darwin Sewerage Strategy, Power and Water has embarked on a plan to improve the quality of treated effl uent discharged by the Ludmilla Wastewater Treatment Plant into Darwin Harbour. Laboratory jar test studies have shown that ferric sulfate with an appropriate polymer can improve the settling of sewage solids at Ludmilla. The jar tests also provide information about the optimum conditions for full-scale plant trials. The jar tests show about a 90 per cent improvement in water quality, whereas the full-scale plant trials achieved about 50 –per cent improvement. Further trials will attempt to identify technical aspects that limited the effectiveness of ferric sulfate during the plant trials.

Hydrodynamic and dispersion modelling of municipal effl uent discharged into Darwin HarbourPower and Water currently treats Darwin’s sewage at fi ve treatment facilities, ranging from physical maceration treatment to biological treatment with waste stabilisation ponds . Treated effl uent is discharged into Darwin Harbour at fi ve points, under Waste Discharge Licences issued by the EPA program under section 74 of the Water Act (2004), as listed in Table 9.1.

treatment facility discharge point easting* northing*

Palmerston Waste Stabilisation Ponds Darwin Harbour 711190E 8616180N

Berrimah Waste Stabilisation Ponds Darwin Harbour 707640E 8621960N

Larrakeyah Macerator Darwin Harbour 698720E 8620860N

Ludmilla Wastewater Treatment Plant East Point 697998E 8628400N

Leanyer/Sanderson Waste Stabilisation Ponds Buffalo Creek 707475E 8632950N

Table 9.1: Summary of Waste Discharge Licences

Each licence requires monitoring of the water quality and volume discharged into Darwin Harbour. Furthermore, Power and Water is required to undertake a hydrodynamic and dispersion assessment of the effl uent in Darwin Harbour from each of the discharge points.

To address this need Power and Water engaged the Charles Darwin University to undertake hydrodynamic and dispersion modelling using the existing two-dimensional (depth average) RMA Darwin Harbour Hydrodynamic and Water Quality.

Using the water quality module associated with the hydrodynamic model, the model was used to investigate particulate dispersion, as well as changes in pollutant concentrations in Darwin Harbour. The study aimed to use the model to:1. Expand the current hydrodynamic model to include Buffalo

Creek and thus be able to assess the discharge from the Leanyer/Sanderson Waste Stabilisation Ponds

2. Establish the extent of dilution and dispersion of effl uent discharged from the fi ve discharge points under the full tidal range in the harbour during both Dry and Wet Season conditions and discharges

3. Predict pollutant concentrations in Darwin Harbour for current and future development scenarios from all discharge points

4. Assess the feasibility of timing the discharges to the tidal regime for Buffalo Creek and East Point to improve dispersion and dilution of the effl uent at the discharge point and beyond into the harbour.

The modelling showed that (Valentine et al 2006):

• The Ludmilla and Palmerston outfalls result in the greatest environmental concentration of pollutants with the largest area of impact. The areas of impact at both the Berrimah and Larrakeyah outfalls are very small.

• Environmental improvements in Buffalo Creek can only be achieved through either enhanced treatment or an alternative discharge location (for example, off Lee Point).

*AMG


Section 10: Documentation and reporting

Wastewater quality databaseRecording wastewater quality data and reporting treatment performance is an integral part of any wastewater quality management system.

Power and Water uses the Corporate Works Information Management System (WIMS) to enter, store, and retrieve wastewater quality data. WIMS automatically generates work orders so that all relevant sampling analyses are done through the year to comply with regulatory and operational requirements.

Work orders allow effi cient waste sampling scheduling by Power and Water employees, essential service operators and trained contractors, and tracking of sampling runs for audit purpose. Although the WIMS database is conforming to expectation, Power and Water is always looking for system improvements to help our data storage and analysis.

DocumentationAll our documents including this report and previous reports in this series, standard operating procedures, the Wastewater Monitoring Program (2005-2006), guideline documents and other reports commissioned by Power and Water are stored on an electronic database for easy retrieval. These documents are continually reviewed when new information becomes available.

ReportingThe WIMS database allows the reports required for regulatory compliance to be formulated effi ciently.

This document is a key component of our reporting obligation to the Department of Natural Resources, the Environment and the Arts (NRETA) and to the Department of Health and Community Services (DHCS) about sewage discharges and recycled water use. It also represents our commitment to public reporting and accountability.

Section 11: Evaluation and audit

Evaluating and auditing the sewage and recycled water quality management system is an important way to ensure the successful management and reuse of water. This report is an integral part of the review and evaluation process.

Audits assess if procedures and processes are in place to collect accurate water quality data and maintain appropriate management systems. As part of the audit process we have engaged independent external consultants to evaluate the Northlakes-Marrara water recycling scheme; the Alice Springs effl uent reuse and discharge scheme and the Yulara effl uent disposal scheme.


Section 12: Review and continual improvement

Power and Water is committed to the ongoing development and improvement of the wastewater management system and the safety of the recycled water supplies.

ReviewThis report is an important way to identify wastewater management issues and facilitate recycled water quality improvements.

ImprovementVarious wastewater management and recycled water quality improvement works have been identifi ed as part of the capital works program for the coming year. Table 12.1 provides a summary of planned wastewater improvement works.

location planned works

Adelaide River No major works planned.

Alice Springs Water in the Alice project ($10.4m) is planned including the construction of an effl uent transfer pipeline, treated effl uent storage tanks, dissolved air fl otation (DAF) treatment plant and Soil Aquifer Treatment (SAT). The DAF plant is due for completion in 2007.

Batchelor No major works planned.

Borroloola No major works planned.

Darwin Planned progressive upgrades to Ludmilla plant.Planned diversion of the Larrakeyah outfall.Undertake Stage 2 development of the East Arm wastewater treatment facility in response to current development and demand for treatment facilities in the Berrimah, Darwin Business Park and East Arm area ($1.6m)Upgrade of Humpty Doo ponds is planned for 2007.

Katherine Upgrade existing ponds to ensure compliance with existing Waste Discharge Licence ($0.2m).

Kings Canyon No major works planned.

Pine Creek No major works planned.

Tennant Creek No major works planned.

Yulara Implement SAT to further treat existing sewerage plant effl uent at Yulara ($0.5m).

Table 12.1: Planned wastewater improvement works


References

Department of Natural Resources, Environment and the Arts. Water Act (As in for force at 14 January 2004).http://www.nt.gov.au/nreta/naturalresources/water/legislation/index.html

Metcalf and Eddy (2003) Wastewater Engineering, Treatment and Reuse. 4th Edition revised by George Tchobanoglous, Franklin L. Burton and H. David Stensel, McGraw-Hill series in civil and environmental engineering.

National Water Quality Management Strategy (2000a) Guidelines for sewerage systems – Use of reclaimed water. Agriculture and Resource Management Council of Australia and New Zealand (ARMCANZ), Australian and New Zealand Environment and Conservation Council (ANZECC) and National Health & Medical Research Council (NHMRC).

National Water Quality Management Strategy (2000b). Australian and New Zealand Guidelines for Fresh and Marine Water Quality, Volume 1, The Guidelines (Chapters 1-7). Australian and New Zealand Environment and Conservation Council (ANZECC) and Agriculture and Resource Management Council of Australia and New Zealand (ARMCANZ).

Power and Water (2003) Applying reclaimed water for irrigation schemes: Management and Safeguards Customer Information Handout.

Power and Water (2004a) Northern Territory communities and urban centres: Sewage pond data. Water Facilities.

Power and Water (2004b) Waste stabilisation ponds design manual. Water Facilities.

Power and Water (2005) Wastewater Treatment, Reuse and Discharge 2005.

Power and Water (2006a) Reclaimed water policy. Water Facilities.

Power and Water (2006b) Wastewater monitoring program 2005-2006. Water Facilities.

Power and Water (2006c) Guidelines for Buffer Zones – Sewage treatment, sludge management and effl uent reuse schemes. Water Facilities Draft.

Power and Water (2006d) Water Reuse in the Alice: Application for approval by the Department of Health and Community Services. Water Services.

Power and Water (2006e) Marrara Reuse Trial September to December 2005. Megan O’Mullane.

Power and Water (2006f) Future options for Northlakes Reuse Scheme Draft.

Valentine, Eric and Totterdale, Phil (2006) Darwin Harbour Effl uent Modelling: Report No.1. Charles Darwin University.


Appendices

Appendix 1:Wastewater treatment performance (assessment)A1.1: Wastewater stabilisation pond (WSP) performance evaluation methodologyAll WSPs have a design capacity based on:• Organic content of sewage measured as BOD5 mg/L• Retention time of the water in the ponds to allow treatment to occur;• Temperature.

Overloading of a WSP could result in:• Excessive odours being generated, especially in the primary or facultative pond;• Poor water quality discharged from the plant, in particular unacceptable levels of ammonia and microorganisms.Because WSPs have long retention times they are able to absorb large hydraulic shocks. Consequently the performance of WSPs is assessed over a long-term basis rather than on daily fl ows. The true concentration of raw sewage is diffi cult to determine due to its heterogenous nature (that is, the sewage contains many different particles of various sizes and composition). To assess the performance of the WSPs the following values have been selected based on historical data and local and expert knowledge:• The organic content of the raw sewage is assumed as 120 mg/L BOD5.• Calculations for hydraulic load are based on the 90th percentile of the average monthly fl ow for the arid region and the 90th

percentile for the dry months for the Top End. For the reporting period 2005-2006 Dry months for this report are considered as June to December 2005 and May and June 200615.

• Ideal hydraulic retention time, assuming no short-circuiting occurs in the ponds.

Under ideal conditions the hydraulic retention time should not vary signifi cantly throughout the year. However, in the Top End, because of increase fl ows due to infi ltration, illegal connections and rainfall patterns the hydraulic retention time can be greatly reduced during the Wet Season. Treatment effi ciency will decrease with these shorter retention times. In particular ammonia is not oxidised as effi ciently.

Assessment of WSP performance in the Top End (from Katherine northwards) is based on the Dry months recorded during the reporting period. However, during a wet year increased rainfall can signifi cantly reduce the retention time for much of the Dry Season. For this reason, the current loading on WSPs for the Top End is based on the fl ows from the high rainfall year of 2003-2004 or, if greater, the fl ows measured during the year of assessment.

Further details on operation and design of WSPs can be found in our Waste Stabilisation Pond Design Manual (Power and Water 2004b).

15 See Appendix 4 Figure A4: Monthly rainfall for 2002-2003 to 2005-2006 at Darwin Airport.


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dat

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dat

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dat

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dat

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dat

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ata

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dat

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thly

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all m

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aver

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16 N

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ay a

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A1.2

: Mon

thly

sew

age

infl o

ws (

ML)

for N

orth

Reg

ion

(200

5-20

06)


A1.3 Monthly sewage infl ows (ML) for South Region (2005-2006)

month alice springs kings canyon tennant creek yulara

Jul-05 205.6 10.4 14.4 21.6

Aug 05 212.5 8.2 10.3 21.8

Sep 05 233.9 6.4 13.8 21.8

Oct 05 243.3 7.0 12.7 21.8

Nov 05 225.2 7.6 15.8 20.7

Dec 05 253.6 5.6 19.5 21.2

Jan 06 236.6 6.4 37.2 22.0

Feb 06 235.2 5.5 28.6 20.0

Mar 06 251.1 6.0 27.2 21.8

Apr 06 219.5 2.3 28.3 21.3

May 06 226.4 2.2 28.1 19.7

Jun 06 217.9 2.4 26.7 20.9

Total ML/annum 2760.9 69.9 262.4 254.7

Monthly 90%ile (ML) 250.3 8.1 28.6 21.8

Daily average (ML) 7.56 0.19 0.72 0.70


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A1.6: Sewage outfl ow (discharge) quality in North Region

number of

samples

median average 90th percentile

Adelaide River outlet from pond 3 (SAd035)

pH 1 8.7 8.7

Suspended solids (mg/L) 1 113 113

TDS (mg/L) 1 563 563

Ammonia (mg/L) 1 <1 0.5

Total nitrogen (mg/L) 1 15.5 15.5

Total phosphorus (mg/L) 1 7 7

BOD5 (mg/L) 1 36 36

E.coli (cfu/100 mL) 1 <200 <200

Batchelor outlet from pond 3 (SBa025)

pH 1 7.7 7.7


TDS (mg/L) 1 350 350

Ammonia (mg/L) 1 4.0 4.0



BOD5 (mg/L) 1 60 60

E.coli (cfu/100 mL) 1 <2000 <2000

Berrimah outlet from pond 3 after weir (SBe100) Dry months

pH 8 9.4 9.2 9.5

Suspended solids (mg/L) 8 78 88 132

TDS (mg/L) 8 814 753 1081

Ammonia (mg/L) 8 1.5 3.6 7.2

Total nitrogen (mg/L) 8 13.5 16.3 24.9

Total phosphorus (mg/L) 8 6 7 8

BOD5 (mg/L) 8 16 22 41

E.coli (cfu/100 mL) 8 301 624 1460

Berrimah outlet from pond 3 after weir (SBe100) Wet months

pH 6 9.3 9.2 10.0


TDS (mg/L) 6 511 504 531

Ammonia (mg/L) 6 2.0 2.9 6.0



BOD5 (mg/L) 6 26 29 42

E.coli (cfu/100 mL) 4 52 636 1717


A1.6: Sewage outfl ow (discharge) quality in North region (continued)

number of

samples


Borroloola ponds outlet from pond 3 (SBo090)

pH 1 10.4 10.4


TDS (mg/L) 1 281 281

Ammonia (mg/L) 1 <1 <1



BOD5 (mg/L) 1 40 40

E.coli (cfu/100 mL) 1 <20 <20

Humpty Doo from irrigation wet well (SHD100)

pH 2 7.5 7.5


TDS (mg/L) 2 478 478

Ammonia (mg/L) 1 37.0 37.0



BOD5 (mg/L) 1 14 14

E.coli (cfu/100 mL) 4 37 055 39 778 56 533

Katherine pond E4 corner (SKa090)

pH 14 9.1 9.2 9.8


TDS (mg/L) 14 260 280 397

Ammonia (mg/L) 14 <1 1.0 1.7



BOD5 (mg/L) 14 40 37 51

E.coli (cfu/100 mL) 15 10 27 40

Larrakeyah after macerator (SLa010) Dry months

pH 7 7.6 7.6 7.9


TDS (mg/L) 7 392 378 421

Ammonia (mg/L) 7 35.0 33.3 46.2



BOD5 (mg/L) 7 119 164 288

E.coli (cfu/100 mL) 7 12 910 000 12 415 000 19 800 000



number of

samples


Larrakeyah after macerator (SLa010) Wet months

pH 3 7.2 7.3 7.8


TDS (mg/L) 3 331 338 358

Ammonia (mg/L) 3 30.0 26.7 34.0



BOD5 (mg/L) 3 112 124 152

E.coli (cfu/100 mL) 4 13 300 000 14 865 000 21 590 000

Leanyer outlet of pond over weir (SLe055) Dry months

pH 8 7.7 7.8 8.3


TDS (mg/L) 8 332 342 391

Ammonia (mg/L) 8 1.5 1.8 3.3



BOD5 (mg/L) 8 48 44 58

E.coli (cfu/100 mL) 7 300 3477 9580

Leanyer outlet of pond over weir (SLe055) Wet months

pH 3 8.4 8.4 9.0


TDS (mg/L) 3 334 314 351

Ammonia (mg/L) 3 3.0 4.3 7.0



BOD5 (mg/L) 3 36 31 36

E.coli (cfu/100 mL) 3 311 2067 4694

Leanyer/Sanderson discharge to Buffalo Creek (SLe100) Dry months

pH 8 7.8 7.9 8.3


TDS (mg/L) 8 377 1926 5745

Ammonia (mg/L) 8 1.5 1.9 3.6



BOD5 (mg/L) 8 45 44 54

E.coli (cfu/100 mL) 7 1300 1280 2200



number of

samples


Leanyer/Sanderson discharge to Buffalo Creek (SLe100) Wet months

pH 3 8.8 8.5 9.1


TDS (mg/L) 3 333 321 357

Ammonia (mg/L) 3 3.0 2.5 3.8



BOD5 (mg/L) 3 35 35 37

E.coli (cfu/100 mL) 4 963 1459 3175

Ludmilla Landside distribution manhole East Point (SLu100) Dry months

pH 6 7.8 7.9 8.3


TDS (mg/L) 6 644 663 738

Ammonia (mg/L) 6 28.5 28.2 29.5



BOD5 (mg/L) 6 87 94 122

E.coli (cfu/100 mL) 6 600 000 3 399 333 9 550 000

Ludmilla Landside distribution manhole East Point (SLu100) Wet months

pH 3 7.9 7.9 8.5


TDS (mg/L) 3 360 360 395

Ammonia (mg/L) 3 5.0 6.3 9.0



BOD5 (mg/L) 3 23 20 34

E.coli (cfu/100 mL) 3 <100 <100 <100

Northlakes/Marrara fi ltered effl uent from 1 ML clear tank (SNL020)

pH 10 6.4 6.3 7.6

Suspended solids (mg/L) 9 1 <1 1

TDS (mg/L) 10 381 373 448

Ammonia (mg/L) 10 1.0 1.6 3.1



BOD5 (mg/L) 10 <1 <1 1

E.coli (cfu/100 mL) 12 <20 <20 <20



number of

samples


Palmerston fi nal effl uent from pond 5 (SPa100) Dry months

pH 6 7.6 8.0 9.0


TDS (mg/L) 6 409 456 608

Ammonia (mg/L) 6 26.0 25.5 32.0



BOD5 (mg/L) 6 42 46 73

E.coli (cfu/100 mL) 6 900 833 1050

Palmerston fi nal effl uent from pond 5 (SPa100) Wet months

pH 4 7.7 7.7 8.0


TDS (mg/L) 4 250 249 275

Ammonia (mg/L) 4 15.5 14.8 17.0



BOD5 (mg/L) 4 19 19 22

E.coli (cfu/100 mL) 4 168 367 738

Pine Creek wet well to reuse (SPC050)

pH 11 9.1 9.2 9.8


TDS (mg/L) 11 282 278 396

Ammonia (mg/L) 11 1.0 1.3 2.0



BOD5 (mg/L) 11 28 33 56

E.coli (cfu/100 mL) 12 122 200 458

Sanderson outlet of pond over weir (SSa055) Dry months

pH 8 8.4 8.4 9.2


TDS (mg/L) 8 365 366 403

Ammonia (mg/L) 8 0.8 0.8 1.0



BOD5 (mg/L) 8 44 42 50

E.coli (cfu/100 mL) 7 1,210 1,354 2,844



number of

samples


Sanderson outlet of pond over weir (SSa055) Wet months

pH 4 8.9 8.6 9.3


TDS (mg/L) 4 348 367 447

Ammonia (mg/L) 4 2.0 3.4 7.2



BOD5 (mg/L) 4 28 27 31

E.coli (cfu/100 mL) 4 96 461 1181


A1.7: Sewage outfl ow (discharge) quality in South Region

number of

samples


Alice Springs ponds A Blatherskite Park outlet from EP1 (SAA040)

pH 14 9.2 9.1 9.6


TDS (mg/L) 13 1040 1050 1236

Ammonia (mg/L) 13 <1 <1 1.8


Total phosphorus (mg/L) 14 4.6 5.0 6.5

BOD5 (mg/L) 14 55 56 76

E.coli (cfu/100 mL) 48 125 1042 3050

Alice Springs ponds B Blatherskite Park outlet from EP2 (SAA045)

pH 14 8.7 8.5 9.0


TDS (mg/L) 13 958 968 1,040

Ammonia (mg/L) 13 2.0 2.7 6.0



BOD5 (mg/L) 13 47 52 94

E.coli (cfu/100 mL) 14 530 2124 7868

Alice Springs ponds A outlet EP7 to Ilparpa (SAA060)

pH 8 9.4 9.4 9.7


TDS (mg/L) 8 1190 1184 1462

Ammonia (mg/L) 8 <1 2.5 6.1



BOD5 (mg/L) 8 40 43 61

E.coli (cfu/100 mL) 33 500 4,095 10 120


pH 9 9.4 9.3 9.5


TDS (mg/L) 9 1520 1472 1556

Ammonia (mg/L) 9 <1 1.6 3.2



BOD5 (mg/L) 9 44 52 67

E.coli (cfu/100 mL) 35 140 322 960


A1.7: Sewage outfl ow (discharge) quality in South Region (continued)

number of

samples


Alice Springs ponds B/C combined outlet (SAB050)

pH 9 8.1 8.0 8.2


TDS (mg/L) 9 953 958 1024

Ammonia (mg/L) 9 8.0 9.9 15.2



BOD5 (mg/L) 9 62 80 121

E.coli (cfu/100 mL) 6 3,080 2209 3100

Kings Canyon outlet (SKK090)

pH No samples

Suspended solids (mg/L) No samples

TDS (mg/L) No samples

Ammonia (mg/L) No samples

Total nitrogen (mg/L) No samples

Total phosphorus (mg/L) No samples

BOD5 (mg/L) No samples

E.coli (cfu/100 mL) 9 115 625 1620


pH 1 9.0 9.0

Suspended solids (mg/L) No samples

TDS (mg/L) 1 1027 1027

Ammonia (mg/L) No samples

Total nitrogen (mg/L) No samples

Total phosphorus (mg/L) No samples

BOD5 (mg/L) No samples

E.coli (cfu/100 mL) No samples

Yulara outlet (SAA040)

pH 3 7.6 7.6 7.7


TDS (mg/L) 3 981 981 1012

Ammonia (mg/L) 3 3.0 5.7 10.2



BOD5 (mg/L) 3 4 22 48

E.coli (cfu/100 mL) 2 800 800 1440


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Ludmilla Wastewater Treatment Plant treats sewage coming from Nightcliff, Winnellie and most of the inner city. The treatment process includes grit removal and solids screening, chlorination, and chemical assisted sedimentation. The treated water is discharged to Darwin Harbour via a pipeline at East Point.

Table A1.9.1 outlines the treatment performance of Ludmilla plant during both dry and wet months using measurements that best assess the environmental impact of the discharge. pH, suspended solids and total suspended solids (TDS) measure the physical characteristics of the water. Ammonia, total nitrogen and total phosphorus measure the amount of nutrients in the water that may promote the growth of nuisance algae. Ammonia is also a toxicant. The biochemical oxygen demand (BOD5) is a measure of how much oxygen the organic content of the water will consume. Escherichia coli (E.coli) indicate if harmful pathogens (disease-causing microorganisms) are possibly present.

Generally the sewage during the wet months is weaker than the sewage during the dry months. Consequently the

discharge is of a higher quality during wet months. However the performance of the treatment process is best assessed against the water treatment objectives and water quality targets proposed in Table A1.9.2. The proposed objectives and targets were developed from:

• A comparison of the technical details with a similar plant at Lower Molonglo Water Quality Control Centre in the ACT

• A review of other literature sources• Laboratory jar tests carried out to assess theoretical

treatment effi ciency.Generally the Ludmilla plant is operating at or above its designed capacity. During dry weather the plant operates at an average fl ow of 9.5 ML per day which is the designed dry weather capacity. Over the whole year the average fl ow is about 25 ML per day which includes wet weather fl ows. The treatment plant performance is diffi cult to optimise during wet weather because of highly variable infl ows.

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(Median values)

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dry

months

Inflow

wet

months

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dry

months

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wet

months

% removal

dry months

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pH 7.0 6.9 7.8 7.9 - -

Suspended solids (mg/L) 202 107 119 50 69 (27 – 91) 13 (0 – 55)

Total dissolved solids (mg/L TDS) 530 375 644 360 - -

Ammonia nitrogen (mg/L) 33.0 20.0 28.5 5.0 16 (0 –35) 63 (61 – 73)

Total nitrogen (mg/L) 44.5 28.0 38.0 11.0 20 (0 –40) 61 (55 – 61)

Total phosphorus (mg/L) 9.5 3.6 9.1 2.8 0 (0 – 36) 43 (26 – 50)

BOD5 (mg/L) 167 35 87 23 26 (0 –72) 34 (31 – 86)

E.coli (cfu/100mL) - - 600 000 <100 - -

Table A1.9.1 Treatment performance of Ludmilla Wastewater Treatment Plant for major pollution measures.

It is interesting to note that the plant achieves high removal of ammonia and total nitrogen during wet months. The chemically assisted sedimentation process is not expected to remove nitrogen compounds. High fl ows during the wet months mean that the fl ow through the plant is very turbulent. Possibly the ammonia is lost to the atmosphere as the sewage becomes aerated during the turbulent fl ow through the plant.

On the other hand, chemically assisted sedimentation is expected to remove most of the phosphorus. It is disappointing to note that very little phosphorus is removed.

To improve treatment performance at the Ludmilla plant, Power and Water has commenced trials to test various combinations of chemicals that will assist in removing various water pollutants from the sewage. In addition other engineering practices and processes are under investigation to upgrade the treatment plant to subsequently improve the treatment processes.

Finally, it should be noted that this assessment is based on a limited number of monthly samples. Subsequently the statistical analysis may not refl ect the true performance of the plant during all conditions.

A1.9: Ludmilla Wastewater Treatment Plant performance


A1.10: Yulara Wastewater Treatment Plant performance

Measurement % Removal objective22

Water quality target

pH - 6.5 – 8.0

Suspended solids 75 45

NH3 as N 30 23

Total Nitrogen (as N) 30 23

Total phosphorus as P 80 2

Organic carbon (as either BOD5 or COD) 60 65(COD target to be determined)

Turbidity 80 To be determined

Table A1.9.2: Proposed water treatment objectives and water quality targets for Ludmilla WWTP

22 Calculated as 90th percentiles of previous jar testing and other case studies (including Lower Molonglo) reported in the literature. The treatment objective was rounded to the nearest fi ve. The water quality target was rounded to the nearest digit.

23 National Water Quality Management Strategy (2000) Guidelines for sewerage systems – Use of reclaimed water. Agriculture and Resource Management Council of Australia and New Zealand (ARMCANZ), Australian and New Zealand Environment and Conservation Council (ANZECC) and National Health & Medical Research Council (NHMRC).

The Yulara sewage treatment plant uses mechanical aeration (activated sludge process) to degrade organic matter and to purify the water. Effl uent from this plant discharges into a set of ponds and is then used to irrigate an adjacent tree lot. No effl uent is discharged off the site.

The chemical quality of the water (pH 7.6, suspended solids 7 mg/L, BOD5 4 mg/L and ammonia 3.0 mg/L) indicates that the activated sludge plant in combination with the ponds is operating adequately.

Appendix A3.2 explains how the quality of recycled water is assessed using the Guidelines for Sewerage Systems Use of Reclaimed Water (2000)23. The treated sewage (800 cfu/100 mL E.coli median value) from Yulara would be considered suitable for low uses such as irrigation of tree lots with controlled public access.

Based on the guidelines, the treated water at Yulara with a TDS of 980 mg/L (median value) would be classed as a high salinity water that cannot be used on soils with restricted drainage. Even with adequate drainage special management for salinity control may be required and the salt tolerance of the plants to be irrigated must be considered.

Appendix A3 provides more information about the recycled water quality.


Appendix 2: Wastewater Discharge Assessment

A2.1: Wastewater discharge licence evaluation and data presentationDischarging wastewater to waterways in the Northern Territory is prohibited unless it is done in accordance with a licence issued under the Water Act (2004). The Controller of Water Resources has granted the following licences to Power and Water Corporation:

This Appendix 2 provides an assessment of the sewage treatment in regards to its discharge to waterways. In particular it provides information about the quality of the discharge and the expected monthly and annual mass loadings for suspended solids (SS), volatile suspended solids (VSS), total nitrogen (TN), total phosphorus (TP) and biochemical oxygen demand (BOD5) to the waterway. Data for pH and conductivity are also presented as requested. Because ammonia (NH3) is key environmental toxicant found in sewage discharges it has also been reported. This information is presented in spreadsheet and graphical formats.

All wastewater samples were collected as described by the Power and Water procedure for wastewater monitoring program 2005-2006. Microbiological and chemical analyses were carried out at the laboratories of the Department of Primary Industries, Fisheries and Mines (DPIFM).

Samples for determining metals in the discharge at Ludmilla and Larrakeyah were collected using an automatic sampler. Hourly samples were collected over 24 hours on 14 March 2006 from the Larrakeyah outfall and on the 13 December 2005 from the Ludmilla outlet. A proportion, based on the hourly fl ow rate over the daily fl ow, of each hourly sample was composited for analysis. Samples were analysed at the Northern Territory Environmental Laboratory (NTEL). The environmental loading for copper, zinc, cadmium, lead, nickel and iron were calculated from the measured concentration of each metal and the daily outfl ow and is reported in Table A2.5.1.

Because wet weather made accessing some sampling sites diffi cult and due to other operational diffi culties, some samples were not collected on all scheduled occasions. These are listed in Table A2.1.1

Where no chemical data was available, readings from previous and following months were averaged and used as an estimate for that month to calculate monthly loads.

Not all daily fl ow data is available for all sites and all months. Where daily fl ow data was not available, a median daily fl ow value was calculated for that month using available data and used to estimate a daily fl ow.

The waste discharge licence granted for the Alice Springs sewage treatment facility is a new format that differs from the previous licences granted to Power and Water. The management of the discharge is governed by:

• Discharge must not prejudice water quality objectives (WQO) outside of any agreed mixing zone when defi ned for the receiving waters

• Discharges must be reduced to the optimum extent by Best Practice Environmental Management (BPEM) in accordance with a hierarchy of waste management.

Location Licence number Expiry date

Berrimah WDL 69 31 July 2006

Katherine WDL 73 31 July 2006

Larrakeyah WDL 70 31 July 2006

Leanyer/Sanderson WDL 72 31 July 2006

Ludmilla WDL 71 31 July 2006

Palmerston WDL 68 31 July 2006

Alice Springs WDL 139 31 December 2007


The licence describes discharge limits based on up-to-date performance data and BPEM/SAT criteria. Previous licences did not prescribe discharge limits.

The licence also includes requirements to:

• Undertake adequate monitoring to ensure full compliance, to characterise the nature of contaminated discharge and ensure agreed WQOs are not prejudiced

• Manage off-site wastewater discharges and to assess aquatic ecological health in the receiving water body• Pro-actively implement BPEM with a focus on water recycling where possible• Carry out self auditing and reporting in line with industry best practice including incident reporting, event reporting as requested

by the controller, annual reporting and environmental management plan review.Alice Springs discharges have been assessed separately.

The waste discharge licence for the Katherine Waste Stabilisation Ponds specifi es that no discharge from the Katherine ponds shall occur while fl ow in the Katherine River is below a stage height of RL 3 m as measured at the hydrographic station GS 8140001. Then the discharge is only permitted if a minimum dilution rate of 1:2000 is maintained at the discharge point. Table A2.5.2 summarises this requirement for discharge and river fl ow.

Location Type of analysis Date

Berrimah ChemicalMicrobiological, chemical

January 2006May 2006

Katherine ChemicalMicrobiological, chemical

August 2005April 2006

Larrakeyah ChemicalMicrobiological, chemical

August 2005May 2006

Leanyer/Sanderson ChemicalMicrobiological, chemical

August 2005May 2006

Ludmilla ChemicalMicrobiological, chemical

August 2005May & June 2006

Palmerston Microbiological, chemical May 2006

Alice Springs

Blatherskite Park Pump Station wet well 1 from EP1. Chemical August 2005 - January 2006

Blatherskite Park Pump Station wet well 2 from EP2. Chemical, microbiological August 2005 - January 2006

Outlet EP7 to Ilparpa Chemical, microbiological August 2005 - January 2006

Outlet EP10 to Ilparpa MicrobiologicalChemical

January, March, April 2006August – December 2005

Outlet wet well ponds B/C MicrobiologicalChemical

March, April 2006August – December 2005

Table A2.1.1 Samples not collected


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: Mas

s loa

ding

disc

harg

e da

ta fo

r Ber

rimah

, Kat

herin

e, La

rrake

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Lean

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dmill

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d Pa

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ston

Was

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ater

Trea

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(cont

inue

d)


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ca

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SV

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NT

PB

OD

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on

du

ctiv

ity

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VS

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TN

TP

BO

D5

(kL)

(mg/

L)(m

g/L)

(mg/

L)(m

g/L)

(mg/

L)(m

g/L)

(μS/

CM)

(To

nn

e)

(To

nn

e)

(To

nn

e)

(To

nn

e)

(To

nn

e)

(To

nn

e)

Ludm

illa Ju

l 05

219

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Oct 0

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once

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r May

and

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(cont

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ata

for A

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wat

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cm)

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nn

e)

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nn

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tratio

n an

d m

ass l

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ly8

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g/L

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thly

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6.6

7.39

4.7

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8.3

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g/L

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thly

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300

500

812

427

430

499

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257

328

910

510

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mg/

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313

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g/L

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g/L

Mon

thly

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31

576

150

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solu

ble

mg/

LM

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471

441

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mg/

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175

132

01

145

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s NaC

lm

g/L

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thly

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51

813

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g so

lubl

em

g/L

Mon

thly

129

142

123

Km

g/L

Mon

thly

118

129

115

Nam

g/L

Mon

thly

119

01

327

116

8SO

4m

g/L

Mon

thly

189

114

21

78

A2.4

Sum

mar

y of t

he e

ffl ue

nt d

ischa

rge

perfo

rman

ce a

nd d

ischa

rge

com

plia

nce

for A

lice

Sprin

gs

24. S

ampl

es n

ot co

llect

ed in

suffi

cient

num

bers

bec

ause

(1) n

o fl o

ws

from

pon

ds d

urin

g so

me

mon

ths,

and

(2) l

icenc

e iss

ued

on 23

Dec

embe

r 200

5.25

. Val

ue ex

ceed

s qua

ntita

tive

disc

harg

e lim

it in

Was

te D

ischa

rge

Licen

ce 14

6.


A2.5: Comparative representation of discharge water quality. The following charts show the key water quality characteristics used to assess the wastewater discharge at the major wastewater treatment sites in the Northern Territory. These measurements include pH, BOD5 (biochemical oxygen demand), suspended solids (SS), total dissolved solids (TDS), ammonia (NH3), total nitrogen (TN), total phosphorus (TP), and Escherichia coli (E.coli).

Comments are made about each site as follows:

• Berrimah: The conductivity was reduced by about 40 per cent in November 2005 following work to reline the sewer going to Berrimah to prevent seawater intrusion. It is diffi cult to assess if the treatment has improved the quality of the discharge until more data is collected.

• Katherine: Due to the long retention times in the evaporation ponds very little water is discharged from this site. Consequently the annual load discharged is small.

• Larrakeyah: The level of treatment at this site is minimal, which is refl ected in the quality of the discharge. Unlike the other discharges, the quality of the discharge during the Dry Season does not differ greatly from the quality discharged during the Wet. The fl ow during the Wet only increases by about 30 per cent whereas the fl ow of the other discharges may increase three to fi ve times, signifi cantly altering the quality of the discharge. It seems that little infi ltration occurs in the localised catchment to Larrakeyah.

• Leanyer and Sanderson: The combined treated fl ow is discharged to Buffalo Creek. Some water is used at the Marrara and Northlakes reclaimed water schemes. Signifi cantly higher fl ows were recorded during wet months.

• Ludmilla: The chemically assisted treatment system is intended to remove particles from the sewage. Removal is varied throughout the year. Signifi cantly higher fl ows were recorded during wet months.

• Palmerston: The volume of discharge increased by about two to three times during the Wet.

• Alice Springs: The water quality is present at four discharge points including: Outlet from EP7 to Ilparpa, Outlet from EP10 to Ilparpa, Outlet from B/C ponds and the take off point to Blatherskite Park for reclaimed water.

For completeness, Adelaide River, Batchelor, Borroloola, Humpty Doo, Northlakes/Marrara, Pine Creek and Yulara have also been included. These facilities do not usually discharge to a receiving waterbody. Tennant Creek has not been included as all the sewage evaporates in the ponds.

Where values for a characteristic are determined as less than the detection limit for the analytical method, the value is assumed to be equal to half the detection limit.


figure a.2.5.1: median pH of treatment plant outflow or discharge

pH

figure a.2.5.2: median suspended solids for treatment plant outflow or discharge

Susp

ende

d so

lids (

mg/

L)


figure a.2.5.3: median total dissolved solids for treatment plant outflow or discharge

TDS (

mg/

L)

figure a.2.5.4: median ammonium (nh3) at treatment plant outflow or discharge

NH 3 (m

g/L)


figure a.2.5.5: median total nitrogen for treatment plant outflow or discharge

TN (m

g/L)

figure a.2.5.6: median total phosphorus for treatment plant outflow or discharge

Tota

l P (m

g/L)


figure a.2.5.7: median bod5 for treatment plant outflow or discharge

BOD 5 (m

g/L)

figure a.2.5.8: median e.coli for treatment plant outflow or discharge

E.col

i (cf

u/10

0mL)


Figure A.2.5.9: Berrimah discharge water quality results - physico-chemical

Wat

er q

ualit

y mea

sure

- SS

, VSS

, BOD

5

Figure A.2.5.10: Berrimah discharge water quality - nutrients

Wat

er q

ualit

y mea

sure

- Co

nduc

tivity

Wat

er q

ualit

y mea

sure

(mg/

L)


figure a.2.5.11: berrimah discharge loading

Wat

er Q

ualit

y Mea

sure

figure a.2.5.12: katherine discharge water quality - physico-chemical

Wat

er q

ualit

y mea

sure

(SS,

VSS,

BOD 5)


figure a.2.5.13: katherine discharge water quality - nutrients

Wat

er q

ualit

y mea

sure

figure a.2.5.14: katherine discharge loadings

Wat

er q

ualit

y mea

sure


figure a.2.5.15: larrakeyah discharge water quality - physico-chemical

Wat

er Q

ualit

y Mea

sure

- SS

, VSS

, BOD

5

figure a.2.5.16: larrakeyah discharge water quality - nutrients

Wat

er q

ualit

y mea

sure

Wat

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ualit

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sure

- Co

nduc

tivity


figure a.2.5.17: larrakeyah discharge loadings

Wat

er q

ualit

y mea

sure

figure a.2.5.18: leanyer/sanderson discharge water quality - physico-chemical

Wat

er q

ualit

y mea

sure

- SS

, VSS

, BOD

5


figure a.2.5.19: leanyer sanderson discharge water quality - nutrients

Wat

er Q

ualit

y Mea

sure

figure a.2.5.20: leanyer/sanderson discharge loading

Wat

er q

ualit

y mea

sure


figure a.2.5.21: ludmilla discharge water quality - physico-chemical

Wat

er Q

ualit

y Mea

sure

- SS

, VSS

, BOD

5

figure a.2.5.22: ludmilla discharge water quality - nutrients

Wat

er q

ualit

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sure

Wat

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ualit

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sure

- Co

nduc

tivity


figure a.2.5.23: ludmilla discharge loading

Wat

er Q

ualit

y Mea

sure

figure a.2.5.24: palmerston discharge water quality - physico-chemical

Wat

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ualit

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- SS

, VSS

, BOD

5

Wat

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- Co

nduc

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figure a.2.5.25: palmerston discharge water quality - nutrients

Wat

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ualit

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sure

figure a.2.5.26: palmerston discharge loading

Wat

er q

ualit

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figure a.2.5.27: alice springs ep7 discharge water quality - physico-chemical

Wat

er Q

ualit

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sure

- SS

, VSS

, BOD

5

figure a.2.5.28: alice springs ep7 discharge water quality - nutrients

Wat

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Wat

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- Co

nduc

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figure a.2.5.29: alice springs ep7 discharge loading

Wat

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, VSS

, BOD

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Wat

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figure a.2.5.31: alice spring ep10 discharge water quality - nutrients

Wat

er Q

ualit

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sure

figure a.2.5.32: alice spring ep10 discharge loading

Wat

er Q

ualit

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sure


figure a.2.5.33: alice springs b/c ponds discharge water quality - physico-chemical


Wat

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Wat

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, VSS

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Wat

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figure a.2.5.35: alice springs b/c ponds discharge loadings

Wat

er Q

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sure

Metal Metal loading Larrakeyah outfall

(g/day)(14 March 2006)

Metal loading Ludmilla

outfall (g/day)(13 December 2005)

Copper (Cu) 1390 1060

Zinc (Zn) 385 735

Cadmium (Cd) 0.8 1.6

Lead (Pb) 11.6 24.5

Nickel (Ni) 15.4 294

Iron (Fe) 1890 7350

Table A2.5.1: Daily metal loadings of the discharge at Larrakeyah and Ludmilla outfalls


Date River Height (m) Allowable discharge

(L/s)Discharge flow at the

river (L/s)Calculated discharge

at the river (kL)

28 Dec 05 5.18 116 50 4320

29 Dec 05 6.15 147 150 12 960

30 Dec 05 3.55 75 59 5098

31 Dec 05 3.72 79 62 5357

01 Jan 06 8.10 228 99 8554

02 Jan 06 7.58 205 87 7517

03 Jan 06 4.26 91 82 7085

04 Jan 06 4.42 95 67 5789

20 Jan 06 4.39 95 77 6653

21 Jan 06 5.00 111 77 6653

22 Jan 06 7.37 195 77 6653

23 Jan 06 7.73 211 100 8640

24 Jan 06 7.60 205 92 7949

25 Jan 06 8.14 230 87 7517

26 Jan 06 7.46 199 82 7085

27 Jan 06 9.80 315 70 6048

28 Jan 06 7.75 212 60 5184

29 Jan 06 7.50 201 55 4752

14 Mar 06 7.48 200 180 15 552

15 Mar 06 8.35 240 175 15 120

16 Mar 06 8.72 259 170 14 688

17 Mar 06 9.18 282 170 14 688

18 Mar 06 10.85 373 170 14 688

19 Mar 06 11.12 389 180 15 552

20 Mar 06 10.50 353 180 15 552

21 Mar 06 14.82 718 65 5616

22 Mar 06 14.09 623 80 6912

28 Mar 06 5.46 124 75 6480

29 Mar 06 7.00 180 70 6048

Table A2.5.2: Katherine River discharge – Flow compliance with river height


Appendix 3: Recycled water

A3.1: Recycled water site description

Marrara Sports Complex and Northlakes Golf CourseThe Darwin Golf Club and the Marrara Sports complex both sourced treated effl uent from the golf course’s ornamental water feature (the pond at the centre of the course). Throughout 2005-2006 the pond stored treated effl uent from the Leanyer/Sanderson Waste Stabilisation Ponds. This water was supplied without further treatment to the following six customers at the Marrara Sports complex from July to October 2005:

• Australian Football League Northern Territory• Darwin Clay Shooters Club• Italian Club• Northern Territory Cricket Association• South Darwin Sporting League• Northern Territory Rugby Union

Customers can only use this recycled water supply from 11 pm to 5 am so that the watering does not occur during daylight when most people are about. In addition, prior to each irrigation cycle, the supply ring main is fl ushed to sewer with fresh recycled water to minimise the possible emission of odours.

The Northlakes Water Reclamation Plant (NWRP) at the Darwin Golf Course treats water from the golf course pond and provides high quality recycled water suitable for high contact uses such as urban residential garden watering and irrigation of open spaces and parks. The treatment processes include dissolved air fl otation (DAF), microfi ltration and disinfection with chlorine. The water is usually used to irrigate the Northlakes Golf Course. After October 2005, all customers at the Marrara Sports Complex use the highly treated water.

Yulara Wastewater Treatment PlantReclaimed water was once spray irrigated onto the tree lot adjacent to the plant. Due to fi re completely destroying the tree lot in early 2005 this recycled water use was discontinued. The previous practice of using reclaimed water for landscape irrigation at the Ayers Rock Resort has been replaced with non-potable ground water provided to the resort by Power and Water.

Ludmilla Wastewater Treatment PlantLudmilla Wastewater Treatment Plant uses reclaimed water for several plant processes including wash-down of sludge vacuum drying fi lters, spraying on reactors to control surface scum, furnace cooling and in grit classifi er to remove organics. Treated effl uent is fi ltered through a 400-micron fabric fi lter.

Humpty DooTreated water from the Humpty Doo wastewater stabilisation ponds is spray irrigated onto fenced bush land adjacent to the ponds. Power and Water is investigating ways to improve the water quality by upgrading the treatment. Aeration, recirculation and building additional secondary ponds are being considered.

Pine CreekReclaimed water from the wastewater stabilisation ponds is provided to the Pine Creek Council to irrigate the sports oval and rail corridor including the heritage area.

The rising main from the wastewater stabilisation ponds to the reclaimed water site is fi tted with a clean water fl ushing system, which effectively eliminates odours during irrigation. Backfl ow prevention devices and air gaps are used to protect the integrity of the drinking water supply.

The Pine Creek Recycled Water scheme has been discontinued due to diffi culties with maintenance.

KatherineThe Katherine wastewater stabilisation ponds provide reclaimed water for irrigation of cattle fodder. This reclaimed water is of a reasonable quality due to the extended retention time in the evaporation ponds. Power and Water is investigating alternative ways to use this water due to the uncertainty of this scheme continuing.

BorroloolaTreated water from Borroloola wastewater stabilisation ponds is spray irrigated onto adjacent bushland. The area is fully fenced to prevent any human contact.

Alice Springs Tree LotThe Alice Springs tree plantation of 25 ha of River Redgums was constructed in the mid-1970s by the then Conservation Commission of the Northern Territory to see if the treated water could be used to grow trees to be used as fi rewood. Because the plantation is on Power and Water land, public access is restricted. As alternative water recycling options come on line the use of the tree plantation will be phased out.

Alice Springs Blatherskite ParkThe effl uent irrigation system at Blatherskite Park commenced at about the same time as the tree plantation was established. Initially lucerne was grown but that was abandoned after a number of years. Today irrigation occurs on the sporting grounds, ovals and horse agistment areas in the park.


Power and Water has negotiated with the Alice Springs Town Council and the Blatherskite Park trustees about the management of this system to limit public contact with the reclaimed water. The trustees have undertaken to:

• Limit daytime watering hours where possible• Provide a schedule of events when public access will occur to restrict irrigation during these times.• Restrict access to the park by locking the entry gates after certain hours.• Improve signage on and around the site.These controls will signifi cantly improve the safety of the reuse system.

Kings Canyon tree farmAll treated effl uent generated by the resort is disposed to a nearby tree farm. The tree farm is fully fenced to restrict publicaccess. Firewood is collected from the tree farm for use in bush camping areas of the resort. Investigations are under way to expand the plantation.

scheme name

(water source)

level of treatment application location public access

Northlakes(Leanyer/Sanderson WSPs) Tertiary Municipal

DarwinGolf Course

Controlled/unrestricted

Marrara(Leanyer/Sanderson WSPs) Secondary Municipal

Marrara Sport Complex – sports ovals Controlled

Humpty Doo(Humpty Doo WSPs) Secondary Municipal Tree lot Controlled

Ludmilla(Ludmilla WWTP) Secondary Municipal

In-plantprocesses Restricted

Pine Creek26

(Pine Creek WSPs) Secondary MunicipalSports oval

& rail corridor Controlled

Katherine(Katherine WSPs) Secondary Agriculture Cattle feedlot Controlled

Blatherskite Park(Alice Springs WSPs) Secondary Municipal Open spaces Controlled

Alice Springs Tree Lot(Alice Springs WSPs) Secondary Agriculture Tree lot Restricted

Kings Canyon(Kings Canyon WSPs) Secondary Agriculture Tree lot Restricted

Yulara Tree Lot27

(Yulara WWTP) Secondary Agriculture Tree lot Restricted

Table A3.1 Summary of recycled water schemes in the Northern Territory.

26 Pine Creek scheme discontinued due to diffi culties with maintenance.27 Yulara scheme discontinued after fi re destroyed the tree lot.


A3.2: Recycled water quality assessment methodology and criteriaGuidelines for Sewerage Systems Use of Reclaimed Water (2000)28 provide advice on reclaimed water quality, level of treatment, safeguards and controls and monitoring. It recognises that the major risk with wastewater is human contact with the wastewater causing infection from viruses, bacteria, protozoa and helminth. It specifi es water quality in terms of surrogates to provide an assessment of an acceptable level of risk. The guidelines recommend thermotolerant coliforms as a general indicator of reclaimed water quality. This group of microorganisms, when found in sewage, consists chiefl y of Escherichia coli (E.coli), which is found in the gut of humans and other warm-blooded mammals. The presence of E.coli in water indicates that the water is probably contaminated by human waste meaning that human pathogens (disease-causing microorganisms) are possibly present. The guideline values for thermotolerant coliforms fall into four main categories:

Compliance is determined by comparing the median values (the “middle” number) with the recommended guideline criteria for that use of water. In addition, if 20 per cent of the results are greater than four times the median guideline level, there is cause for further investigation for underlying reason.

It should be stressed that the determination of compliance is a statistical one and that an analysis result of greater magnitude than the median guideline value should not be an immediate cause of concern. The assessment should be undertaken on a continual basis.

Under the guidelines, another important issue associated with the use of recycled water is the potential impact of the chemical quality of the water on plants and on the characteristics of the soil. Increased salt loads may reduce the yield potential of salt sensitive plants and the infi ltration rate of the water through the soil. For example, high salinity waters may require restricted drainage so that the water can be used on soils. Even with adequate drainage special management for salinity control may be required and thesalt tolerance of the plants to be irrigated might need tobe considered.

In addition the guidelines stipulate that suspended solids be measured as a critical control to ensure effective treatment. Suspended particulate matter may shelter disease-causing organisms present in the recycled water from the effects of disinfection. The treated water from a wastewater stabilisation pond will contain high numbers of algal cells, which contribute signifi cantly to the suspended solids of the water. The mechanisms for disinfection in ponds include the effects of sunlight, predation by other microorganisms, sedimentation and die-off. Consequently the ability of a pond to remove pathogens depends on the time the water spends in the pond rather than the action of a chemical disinfectant. On this basis, suspended solids are not reported for pond systems supplying recycled water.

reclaimed water use applications thermotolerant coliforms per 100mL (median value)

Non-human food chain <10 000

Low contact, eg. irrigation of open spaces with controlled access <1000

Medium contact, eg, drinking water for stock (except pigs) <100

High contact, eg. urban residential garden watering <10

28 National Water Quality Management Strategy (2000a).


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ontin

ued)


class comment electrical conductivity (μs/cm)

total dissolved solids

(mg/l)

1. Low-salinity water can be used with most crops on most soils and with all methods of water application with little likelihood that a salinity problem will develop. Some leaching is required, but this occurs under normal irrigation practices except in soil of extremely low permeability.

0 - 280 0 - 175

2. Medium-salinity water can be used if moderate leaching occurs. Plants with medium salt tolerance can be grown, usually without special measures for salinity control. Sprinkler irrigation with the more-saline waters in this group may cause leaf scorch on salt-sensitive crops, especially at high temperatures in the daytime and with low application rates.

280 - 800 175 - 500

3. High-salinity water cannot be used on soils with restricted drainage. Even with adequate drainage, special management for salinity control may be required and the salt tolerance of the plants to be irrigated must be considered.

800 – 2300 500 – 1500

4. Very high-salinity water is not suitable for irrigation water under ordinary conditions. For use, soils must be permeable, drainage adequate, water must be applied in excess to provide considerable leaching and salt-tolerant crops should be selected.

2300 – 5500 1500 – 3500

5. Extremely high-salinity water may be used on permeable, well-drained soils under good management, especially in relation to leaching and for salt-tolerant crops, or occasional emergency use.

>5500 >3500

A3.4: General guidelines for salinity of irrigation water36

36 Table 4 National Water Quality Management Strategy (2000a) taken from National Water Quality Management Strategy (2000b) Australian Water Quality Guidelines for Fresh and Marine Waters.


mo

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530

086

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211

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1676

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14 36

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43 8

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0531

410

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7251

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4 74

0

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522

101

16 9

420

1487

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8923

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590

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515

997

11 61

90

2566

00

248

664

11 73

480

710

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251

6666

025

610

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57 0

8435

50117

485

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0666

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2207

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: Rec

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Sum

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in th

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ther

n Te

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5-20

06:

Volu

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effl u

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ater

: 1.7

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Perc

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37 N

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one

thou

sand

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s (kL

).


A3.5: Recycled water qualityTable A3.5 reports the median values for E.coli against the guideline criteria as discussed in Appendices A3.2 and A3.3. Table A3.6 defi nes the salinity class for the water comparing electrical conductivity and total dissolved solids (TDS) against guideline recommendations (Appendix A3.4) for the managing salinity impacts on soils and plants.

Except at Humpty Doo, the recycled water is of a bacteriological quality suitable for its intended use. The quality of the water in the golf course pond is marginal for its intended use; however, this water is now further treated using the dissolved air fl otation and microfi ltration treatment system. At Humpty Doo, Power and Water is planning to build additional ponds to increase retention time in the ponds so that pathogen levels are decreased.

The recycled waters used in the Darwin, Humpty Doo, Katherine and Pine Creek schemes are classifi ed as Class 2 for salinity of irrigation water. This medium-salinity water should only be used on soils in which moderate leaching occurs and irrigated on plants with medium salt tolerance. Application rates may need to be low.

The recycled waters used in the Yulara and Alice Springs schemes are classifi ed as Class 3 for salinity of irrigation water. This high-salinity water should be only used on soils with adequate drainage and the salinity tolerance of the plants to be irrigated must be considered.

location sampling frequency E.coli (cfu/100mL)

Median 80th Percentile

Actual Scheduled44 Guideline Measured value

Guideline value

Measured value

Guideline value45

Darwin (Marrara) 046 Not defi ned Monthly No value 10 No value 40

Darwin Northlakes (Golf course pond)47

12 Monthly Monthly 1040 1000 4600 4000

Darwin Northlakes (Filtered water)

12 Monthly Monthly <2048 10 <20 40

Humpty Doo 449 2-Monthly Monthly 37 000 10 000 52 000 40 000

Ludmilla 0 Not defi ned Weekly No data 1000 No data No data

Pine Creek 12 Monthly Monthly 120 1000 410 4000

Katherine 15 Monthly Monthly 10 1000 36 4000

Yulara Tree Farm 050 Monthly Monthly No results 10 000 No result 40 000

Kings Canyon 99 Monthly Monthly 140 10 000 860 40 000

Alice Springs (Blatherskite Park)

48 Weekly Monthly 130 1000 1800 4000

Alice Springs(Tree Farm)

4 Weekly Monthly 1900 10 000 3100 40 000

Table A3.5 Monitoring and microbiological quality for recycled water in Northern Territory

Water recycling was not undertaken at Pine Creek and Yulara in 2005-2006; however, the water quality results are reported here for reference purposes.

44 As scheduled in Power and Water (2006) Wastewater monitoring program 2005-2006. Water Facilities.45 If 20 per cent of the results are greater than four times the median guideline level, there is cause for further investigation for underlying reason (National

Water Quality Management Strategy 2000).46 No samples collected from the Marrara system because the water supplied during 2005-2006 was a blend of fi ltered water from Northlakes treatment plant

and Darwin tap water.47 Samples collected from pond at Darwin Golf Course.48 E.coli values reported by the laboratory as <20 cfu/100mL.49 No fl ow occurs for many months during the Dry.50 Water recycling onto Yulara Tree Farm discontinued after fi re had destroyed the trees in early 2005.


location scheme electrical

conductivity (μs/cm)total dissolved

solids (mg/L)

salinity class51

Darwin Marrara No data52 No data Not determined

Darwin Northlakes(Golf course pond)

540 380 2

Darwin Northlakes(Filtered water)

600 380 2

Humpty Doo Tree lot 760 480 2

Pine Creek 450 280 2

Katherine 420 260 2

Yulara Tree Farm54 1550 980 3

Kings Canyon No data No data Not determined

Alice Springs Blatherskite Park 1600 1040 3

Alice Springs Tree Farm 1510 950 3

A3.6: Salinity classes of recycled water.

51 Appendix A3.4 extract from Table 4 National Water Quality Management Strategy (2000a) taken from National Water Quality Management Strategy (2000b) Australian Water Quality Guidelines for Fresh and Marine Waters.

52 No samples collected from the Marrara system because the water supplied during 2005-2006 was a blend of fi ltered water from Northlakes treatment plant and Darwin tap water.

53 Samples collected from pond at Darwin Golf Course.54 Water recycling onto Yulara Tree Farm discontinued after fi re had destroyed the trees in early 2005.


Appendix 4: Rainfall

figure a.4: monthly rainfall for 2002-2003 to 2005-2006 at darwin airport

Rain

fall

(mm

)

Month


List of fi gures

figure description page

Figure 2.1: Hydraulic and organic loading of design capacity for WSPs. 10

Figure 5.1: Median E.coli values in recycled water used with controlled public access. 16

Figure 5.2: 80th percentile E.coli in recycled water with controlled public access. 16

Figure 5.3: Median E.coli values in recycled water used for non-human food crops. 17

Figure 5.4: 80th percentile E.coli in recycled water used for non-human food crops. 17

Figure 6.1: Daily infl ow to Ludmilla Wastewater Treatment Plant 22

Figure 6.2: Treated overfl ows to Ludmilla Creek. 23

Figure 6.3: Sewage odour complaints in the Darwin area 2005-2006 24

Figure 6.4: Sewage overfl ows reported to Power and Water 2005-2006 24

Figure A.2.5.1 Median pH of treatment plant outfl ow or discharge. 57

Figure A.2.5.2 Median suspended solids for treatment plant outfl ow or discharge 57

Figure A.2.5.3 Median Total Dissolve Solids for treatment plant outfl ow or discharge 58

Figure A.2.5.4 Median ammonium (NH3) at treatment plant outfl ow or discharge 58

Figure A.2.5.5 Median total nitrogen for treatment plant outfl ow or discharge 59

Figure A.2.5.6 Median total phosphorus for treatment plant outfl ow or discharge 59

Figure A.2.5.7 Median BOD5 for treatment plant outfl ow or discharge 60

Figure A.2.5.8 Median E.coli for treatment plant outfl ow or discharge 60

Figure A.2.5.9 Berrimah discharge water quality results – Physio-chemical 61

Figure A.2.5.10 Berrimah discharge water quality results – Nutrients 61

Figure A.2.5.11 Berrimah discharge loading 62

Figure A.2.5.12 Katherine discharge water quality results – Physio-chemical 62

Figure A.2.5.13 Katherine discharge water quality results – Nutrients 63

Figure A.2.5.14 Katherine discharge loading 63

Figure A.2.5.15 Larrakeyah discharge water quality results – Physio-chemical 64

Figure A.2.5.16 Larrakeyah discharge water quality results – Nutrients 64

Figure A.2.5.17 Larrakeyah discharge loading 65

Figure A.2.5.18 Leanyer/Sanderson discharge water quality results – Physio-chemical 65

Figure A.2.5.19 Leanyer/Sanderson discharge water quality results – Nutrients 66

Figure A.2.5.20 Leanyer/Sanderson discharge loading 66


Figure A.2.5.21 Ludmilla discharge water quality results – Physio-chemical 67

Figure A.2.5.22 Ludmilla discharge water quality results – Nutrients 67

Figure A.2.5.23 Ludmilla discharge loading 68

Figure A.2.5.24 Palmerston discharge water quality results – Physio-chemical 68

Figure A.2.5.25 Palmerston discharge water quality results – Nutrients 69

Figure A.2.5.26 Palmerston discharge loading 69

Figure A.2.5.27 Alice Springs EP7 discharge water quality results – Physio-chemical 70

Figure A.2.5.28 Alice Springs EP7 discharge water quality results – Nutrients 70

Figure A.2.5.29 Alice Springs EP7 discharge loading 71

Figure A.2.5.30 Alice Springs EP10 discharge water quality results – Physio-chemical 71

Figure A.2.5.31 Alice Springs EP10 discharge water quality results – Nutrients 72

Figure A.2.5.32 Alice Springs EP10 discharge loading 72

Figure A.2.5.33 Alice Springs B/C ponds discharge water quality results – Physio-chemical 73

Figure A.2.5.34 Alice Springs B/C ponds discharge water quality results – Nutrients 73

Figure A.2.5.35 Alice Springs B/C ponds discharge loading 74

Figure A.4 Monthly rainfall for 2002-2003 to 2005-2006 at Darwin Airport 85


List of tables

table description page

Table 2.1 Types of treatment processes and discharge techniques used in the Northern Territory. 7

Table 5.1 Summary of recycled water schemes in the Northern Territory. 15

Table 5.2 Typical composition of domestic sewage in the Northern Territory compared to the literature. 19

Table 5.3 Annual environmental mass loadings as required by Waste Discharge Licences. 20

Table 6.1 Recorded incidents of sewage overfl ows reported to EPA program. 21

Table 6.3 Untreated and treated overfl ows to Ludmilla Creek. 23

Table 6.4 Number of sewage odour complaints in Darwin area 2006-2004. 24

Table 9.1 Summary of Waste Discharge Licences. 27

Table 12.1 Planned wastewater improvement works. 29

Table A1.9.1 Treatment performance of Ludmilla Wastewater Treatment Plant for major pollution measures. 46

Table A1.9.2 Proposed water treatment objectives and water quality targets for Ludmilla WWTP. 47

Table A2.1.1 Samples not collected 49

Table A2.5.1 Daily metal loadings of the discharge at Larrakeyah and Ludmilla outfalls. 74

Table A2.5.2 Katherine River discharge – Flow compliance with river height. 75

Table A3.1 Summary of recycled water schemes in the Northern Territory. 77

Table A3.5 Monitoring and microbiological quality for recycled water in the Northern Territory. 83


Abbreviation and defi nitions (glossary)

algae Simple aquatic plants that are often microscopic.

ADWF Average Dry Weather Flow

BOD5 Biochemical oxygen demand measured over 5 days at 20 ˚C. A measure of the organic strength of the sewage.

bulk waste Trade waste that is delivered by truck.

CAS Chemically assisted sedimentation – a water treatment process.

cfu Colony forming units – One bacterium will form one colony on agar growth media.

Conductivity A measure of the ability of water to carry an electric current.

DAF Dissolved air fl otation – a water treatment process.

Discharge loading The total mass of a suspended or dissolved constituent in a sewage discharge measure over one year, expressed in units of tonnes per year. It is calculated by multiplying the determine concentration value by the associated outfl ow volume.

E.coli Escherichia coli – a strain of bacterium commonly found in the gut of warm blooded animals and used to indicate the degree of faecal contamination.

EP Equivalent population.

EPA Environmental Protection Agency.

kL Kilolitres – one thousand litres.

m Cubic metre – one cubic metre contains one thousand litres of water.

mg/L Milligrams per litre – a measure of the concentration of a substance in water.

Median The middle value in a distribution, above and below which lie an equal number of values.

Microfi ltration An advanced water treatment process using special membranes.

ML Megalitres – one million litres.

ND No data.

NPI National Pollution Inventory

NTEL Northern Territory Environmental Laboratory.

Nutrients Nitrogen and phosphorus which promote the growth of plants.

NRETA Department of Natural Resources, Environment and Arts.

Organic nitrogen Organic bound nitrogen that includes such natural materials as proteins, and peptides, nucleic acids and urea, and numerous synthetic organic materials.

Percentile Order statistics providing a way of estimating proportions of the data that should fall below a given value or percentile.

Pathogens Disease causing organisms.

3


PDWF Peak dry weather fl ow.

pH A measure of the acidity of the water on a scale of 0 to 14 with 0 being very acidic, 7 being neutral and 14 being very alkaline.

PWWF Peak wet weather fl ow.

Recycled water Sewage that is treated and used for benefi cial purposes.

SAR Sodium adsorption ratio is used to predict the potential for sodium to accumulate in the soil

SAT Soil aquifer treatment.

SCADA System control and data acquisition.

Sewer Part of the sewerage system that carries the sewage, usually a system of pipes.

SS Suspended solids – a measure of the portion of particular matter in the water that does not pass through a fi lter.

TDS Total Dissolved Solids – a measure of the portion of dissolved substances in water that passes through a fi lter.

TKN Total Kjeldahl Nitrogen – Analytical technique for determining the total amount of ammonia and organic nitrogen in the water.

Trade waste Industrial or non-domestic wastewater generated by industry.

VSS Volatile suspended solids – a measure of the amount of suspended solids lost during ignition.

WDL Waste discharge licence

WIMS Works Information Management System.

WSP Waste stabilisation pond

WWTP Wastewater treatment plant.

Abbreviation and defi nitions (glossary) - continued.

PalmerstonPalm PlazaUniversity AvenueGPO Box 1921Darwin NT 0801

Telephone (08) 8999 3620Facsimilie (08) 8932 6592

Alice SpringsGreatorex BuildingCnr Bath and Parsons StreetsPO Box 1521Alice Springs NT 0871

Telephone (08) 8951 5408Facsimile (08) 8951 5418

KatherineNT Government CentreFirst StreetPO Box 1045Katherine NT 0851


Tennant CreekNT Government CentrePeko RoadPO Box 505Tennant Creek NT 0861


Head Offi ce2nd Level, Mitchell Centre55 Mitchell Street, Darwin NT 0800GPO Box 1921, Darwin NT 0801Customer Service Offi ceGround Floor, Mitchell Centre, DarwinMonday – Friday (except public holidays) 8.00am – 4.30pmSaturday 9.00am – 12.00pmCall 1800 245 092ABN 15 947 352 360www.powerwater.com.au

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