crows nest and h ampton water tr eatment: from...

40th Annual Queensland Water Industry Operations Conference & Exhibition Page No. 42 Clive Berghofer Recreation Centre, USQ, Toowoomba, 17 to 18 June, 2015

CROWS NEST AND HAMPTON WATER TREATMENT: FROM RAGS TO RICHES

Paper Presented by:

Terry Heness

Author:

Terry Heness, Senior Operator,

Toowoomba Regional Council

40th Annual WIOA Queensland Water Industry Operations Conference and Exhibition

Clive Berghofer Recreation Centre, University of Southern Queensland, Toowoomba

16 to 18 June, 2015


CROWS NEST AND HAMPTON WATER TREATMENT: FROM RAGS TO RICHES

Terry Heness, Senior Operator, Toowoomba Regional Council ABSTRACT This paper will present the reasons why the Toowoomba Regional Council (TRC) built a new water treatment plant to supply the townships of Crows Nest and Hampton in the Northern districts of TRC, and highlight some of the short comings of the existing water treatment plants located at Crows Nest and Hampton. The paper will also cover some of the operational issues associated with the commissioning and proving of the new water treatment plant, including water quality results from this period and optimisation of a brand new water treatment plant with technologies and automation levels that some of the operations staff may not have previously been exposed to. 1.0 INTRODUCTION

The townships of Crows Nest and Hampton located North of Toowoomba both have Water Treatment Plants that were built in 2004 and 1996 respectively. Both plants are direct filtration, utilising pressure filters. Apart from coagulant and pre-chlorination dosing, these pressure filters were the only form of pre-treatment. There were no clarifiers or static mixers and the dosing injection points were located close to the filter intakes points. The raw water which is sourced from two of the three supply dams for Toowoomba Regional Council have historically had good water quality, but at times the Iron and Manganese quality would elevate to unmanageable levels due to quick filling events (2011) or in some cases annual dam turn over events.

Figure1: Crows Nest WTP Figure 2: Hampton WTP

As the supply dams historically have good water quality with turbidity below 10 NTU, Iron below 0.1 mg/L and Manganese below 0.05 mg/L, the water treatment plants at Crows Nest and Hampton generally provided good water quality to the consumers. In 2011 there was a major filling event of the 2 supply dams (from approx. 8% to 100% in a matter of days) which changed the thinking of how suitable these water treatment palnts were to supply potable water to consumers. The main issue was the inability of both water treatment plants to remove Iron and Manganese within the treatment process.


Figure 3: Graph Showing the Inability of the Hampton and Crows Nest WTP’s to Remove Manganese and Iron

The Manganese was the main issue as it would oxidise into a soluble solution and pass through the filter media (river sand and coal) ending up in the reticulation system. This became a public relations nightmare as there were many customer complaints (in the hundreds) and the reticulation mains were being flushed daily to try and remove the stained water from the system. Unfortunately, until the Manganese levels in the dams reduced, both water treatment plants were unable to cope with the loading and there was not a lot that the operations staff could do due to the design of both the water treatment plants.

Figure 4 & 5: What the Residents of Crows Nest and Hampton Saw During the Periods of High Manganese Levels in the Raw Water

2.0 DISCUSSION

In 2012, TRC commissioned a report on the viability of upgrading the two water treatment plants located at Hampton and Crows Nest. The report recommended that both plants be upgraded to include upflow clarifiers and new dosing systems. The report also noted a third option - to build a completely new water treatment plant


which would supply both towns. The new water treatment plant option would include a new supply main to the township of Hampton and connection to the existing supply main to Crows Nest. The option to build a new water treatment was adopted by council for the following reasons:

� Lower operating costs. � Lower maintenance costs. � A water treatment plant that would be suitable of for the next 20+ years.

The new water treatment plant would connect to existing Crows Nest supply main as the new water treatment plant was to be build beside existing raw water storage reservoirs located at Pechey approx. 4.8 km’s South East of Crows Nest and approx. 6.8 km’s North East of Hampton. A new supply main needed to be constructed to connect the township of Hampton to the new water treatment plant, this pipeline is approx. 6.8 km in length.

2.1 New Water Treatment Plant Design

The new Pechey water treatment plant was designed with the following characteristics: 1. Flat bottom upflow clarifier ((d)6m x (h)4m) 2. 2 x Gravity filters, media – river sand, DMI-65, filter coal. 3. UV disinfection system. 4. 144KL clear water contact tank. 5. Minimum flow rate 10 L/s (0.86 ML/d) 6. Maximum flow rate 25 L/s (2.16 ML/d) 7. Chlorine dosing facility (Pre and Post). 8. Coagulant dosing facility. 9. Powder Activated Carbon dosing facility. 10. Control room / laboratory. 11. Portable generator (160kVA) connection for control room. 12. Dedicated air supply system. 13. HMI interface to the PLC. 14. 100% reuse of backwash water and analyser feed waters, all backwash and analyser

feed water is returned to the raw water reservoirs via a waste water wet well.

Figure 6: The new Pechey WTP 2.2 Construction, Commissioning and Proving

Construction of the new Pechey water treatment plant commenced in January 2014 and construction was completed in June 2014. The commissioning stage was completed in mid-July. During the commissioning stage, one


of the supply dams experienced a turn over event which elevated the raw water Manganese. The new Pechey water treatment plant handled these elevated levels of Manganese very well with no noticeable impact on treated water quality as would have been previously experienced with the two older water treatment plants.

TRC Northern operations staff commenced a two week proving period towards the end of July to collect independent data to validate the data collected by the construction company, this included operations staff familiarising themselves with the WTP and fine tuning the processes and chemical dosing.

Table 1: Results from Pechey Water Treatment Plant Proving Period

28-Jul-14

29-Jul-14

30-Jul-14

31-Jul-14

01-Aug-14

04-Aug-14

05-Aug-14

06-Aug-14

07-Aug-14

08-Aug-14

Raw water

Turbidity NTU 2.6 2.4 1.4 2 2 3.6 2.4 2 2.1 1.8 Apparent Colour HU 14 53 40 45 45 73 68 57 46 41

pH 7.4 7.3 7.4 7.5 7.5 7.3 7.4 7.3 7.3 7.3

Iron mg/L 0.11 0.08 0.05 0.06 0.04

Manganese mg/L 0.17 0.18 0.12 0.24 0.18 Aluminium mg/L 0.13 0.06 0.04 0.03

E. Coli CFU/100ml 0 0 0 9 Total Coliforms CFU/100ml 0 1 99 99 Total plate count CFU/ml 360 310 365 295

Final water

Turbidity NTU 0.2 0.2 0.1 0.2 0.1 0.2 0.3 0.2 0.1 0.2 Free chlorine residual mg/L 1.5 2.1 1.6 1.8 1.7 1.73 Apparent Colour HU 2 4 1 9 9 11 6 2 6 8

pH 7.8 7.6 7.6 7.6 7.6 7.6 7.6 7.5 7.5 7.5

Iron mg/L 0 0 0 0.01 0

Manganese mg/L 0 0.01 0.02 0 0 Aluminium mg/L 0.07 0.05 0.01 0.01

E. Coli CFU/100ml 0 0 0 0 Total Coliforms CFU/100ml 0 0 0 0 Total plate count CFU/ml 2 0 0 2

The results from the proving period confirmed that the Pechey water treatment plant could effectively remove Manganese and Iron from the raw water, the final water quality during this period was vastly improved upon once the operations staff had ironed out all the glitches and bugs and become comfortable operating the different process.


2.3 Challenges

One challenge was adapting to working at a fully automated water treatment plant as the old Crows Nest and Hampton water treatment plants were very basic and the only really changeable parameters were chemical dosing and backwash frequency. With so much automation, it was difficult to diagnose some faults (especially at 1am in the morning), but once the operations staff became more familiar with the controls and process, faults were much easier to diagnose. Most of the faults were teething issues with the PLC i.e. interlocks that could have been setup better, power brown outs that froze the PLC in its last state (HMI showing one thing and the water treatment plant doing something different). As the water treatment plant has two UV units, the design limited the plant to four starts a day per unit. Any more than 4 starts a day per unit and the UV disinfection train had to be shut down until the start of the next 24 hour period (midnight). This issue was rectified for the short term by automatically opening a solenoid valve upstream of the UV disinfection train when the water treatment plant stopped production. This allowed the service water pumps to constantly supply 2 L/s of water past the UV lamps, until flow control valves could be installed and commissioned at the reservoir at Hampton and the two reservoirs at Crows Nest. Until these flow control valves were installed and commissioned there was no real flow rate control on filling the reservoirs meaning the Pechey plant was doing up to 9 starts a day (or more) when the plant was designed for a maximum of four starts per day. The Powdered Activated Carbon (PAC) plant was not properly commissioned during the commissioning stage due to not having the vacuum loading system onsite. When the vacuum loading system was installed and commissioning began, it became clear that the PAC plant was not going to work as expected. The problems included not being able to maintain a constant level in the venturi due to varying pressure differences in the raw water main. This meant air was being introduced into the raw water supply stream and then causing the raw water pumps to shut down on a water void fault. Also, due to the pressure variations in the raw water supply main, the PAC plant was not able to fully inject the activated carbon solution into the raw water stream causing the venturi to overflow into an emergency storage tank fitted with level switches that call out the operator.

3.0 CONCLUSION

With the construction of the new Pechey water treatment plant, Toowoomba Regional Council is able to ensure a safe and clean water supply to the people of both Crows Nest and Hampton for the next 20+ years and two out dated and ineffective water treatment plants have been decommissioned. The operations staff can dedicate more time to one water treatment plant than they were able to previously with the two water treatment plants. There were other challenges with the new Peachey water treatment plant which consisted of identifying the Pechey water treatment plants idiocyncracies but once these were identified the operating challenges became less and less. Whilst the issues of the flow control valves at the reservoirs in Hampton and Crows Nest and the powder activated carbon plant were yet to be fully resolved at the time of writing this paper, the operations staff have managed to optimally run the Pechey water treatment plant while these two issues are being resolved. The Northern Districts operations staff feel more confident about the quality of potable water that is supplied to the consumers in both the townships of Crows Nest and Hampton during elevated Manganese and Iron events.

crows nest and h ampton water tr eatment: from...

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