sustainable odour control in urban environments

ERG (Air Pollution Control) Ltd www.ergapc.co.uk

Sustainable Odour Control in Urban Sustainable Odour Control in Urban EnvironmentsEnvironments

James Scott-Bowden James Scott-Bowden MBA, BSc (Hons)MBA, BSc (Hons)

Managing Director, ERG (Air Pollution Control) LtdManaging Director, ERG (Air Pollution Control) Ltd

ERG (Air Pollution Control) Ltd www.ergapc.com2

IntroductionIntroduction

About ERGAbout ERG Leading specialist odour control and air pollution Leading specialist odour control and air pollution

control supplier control supplier Odour control systems - UK and Middle East waste water and Odour control systems - UK and Middle East waste water and

recycling industries recycling industries Air pollution control - wide range of global industriesAir pollution control - wide range of global industries

More than 30 years’ experience More than 30 years’ experience UK headquarters and Middle East based subsidiaryUK headquarters and Middle East based subsidiary Global network of V-texGlobal network of V-texTMTM technology licensees technology licensees Maintenance division supplying maintenance services Maintenance division supplying maintenance services

for odour control and air pollution control systems for odour control and air pollution control systems Consultancy services to assist clients with the Consultancy services to assist clients with the

specification of their air pollution or odour control specification of their air pollution or odour control requirements requirements


Trends in the municipal sectorTrends in the municipal sector

With increasing focus on sustainability, the municipal sector is increasingly locating With increasing focus on sustainability, the municipal sector is increasingly locating recycling and treatment facilities: recycling and treatment facilities:

in urban environments to be closer to their waste sources, and in urban environments to be closer to their waste sources, and housing facilities in enclosed buildingshousing facilities in enclosed buildings

Challenges for the odour control industry:Challenges for the odour control industry:

EfficiencyEfficiency – the need is for ever more efficient odour extraction technologies to minimise – the need is for ever more efficient odour extraction technologies to minimise any odour nuisance to their residential community neighbours any odour nuisance to their residential community neighbours

Carbon footprintCarbon footprint - cost pressures (and social responsibility) drive need for more energy - cost pressures (and social responsibility) drive need for more energy efficient odour control systems for reduced carbon footprintefficient odour control systems for reduced carbon footprint


Cost saving illustrationCost saving illustration

Example: a new sewage treatment works in a sensitive urban area for a town with a population of 250,000

Design guideline - the specified hourly air change rate is 3 times the internal volume of the enclosing structure, i.e 240,000m3/hr

the resulting odour control system consumes a staggering 1,200kW each hour

If, instead, an hourly air change rate of 1 is selected, the extracted overall volume would be 30% less and the power usage 25% less

At 9p per kW this is a running cost saving of £27/hr or £236,500/yr Over the 20 years design life this equates to a £5million saving

However odour control is often a highly political local issue, and specifiers are “encouraged” to be excessively conservative! Maintaining a low carbon footprint

can sometimes become secondary to eliminating odour complaints.


Municipal recycling example - Municipal recycling example - ManchesterManchester

Rochdale processes 750 tonnes of green waste together Rochdale processes 750 tonnes of green waste together and 50 tonnes of food waste per week, and converts this and 50 tonnes of food waste per week, and converts this into about 600 tonnes of top soil suitable for agricultural into about 600 tonnes of top soil suitable for agricultural use by employing a composting and maturation process use by employing a composting and maturation process which takes about 8 weeks.which takes about 8 weeks.

The Bredbury and Trafford Park facilities are The Bredbury and Trafford Park facilities are approximately twice as large as Rochdale.approximately twice as large as Rochdale.

Odour control system need to be designed such that operators can minimise Odour control system need to be designed such that operators can minimise the energy consumption whilst still providing maximum odour removal to the energy consumption whilst still providing maximum odour removal to avoid complaints.avoid complaints.

Examples of this in practice are the new TEG Group Plc in-vessel composting Examples of this in practice are the new TEG Group Plc in-vessel composting facilities being built for the Greater Manchester Waste Disposal Authority (GMWDA) facilities being built for the Greater Manchester Waste Disposal Authority (GMWDA) at Rochdale, Bredbury and Trafford Parkat Rochdale, Bredbury and Trafford Park


Manchester example, Manchester example, cont’dcont’d

Peak extraction rates for the Rochdale plant are determined by need to prevent odour escape even when the vehicle access doors are open, giving an extraction rate of rate of 118,800m3/hr, ( 3.3 air changes per hr)

An additional challenge – water vapour fog. The waste gives off significant quantity of water vapour as the compost reaches 70oC during processing cycle, which condenses within the building forming a fog.

The extraction rate therefore has to also be able to clear the fog to improve visibility inside the building so that operators can work safely.

Solution Modulated air extraction rates – the odour control system is able to modulate the volume of extracted air to meet the requirements

at weekends and at night the extraction rate falls to 20% of the peak rate when the doors are closed during the working day the extraction is 50% of peak rate only when the doors are open or there is a need to clear the fog in the building do the fans ramp up to

peak extraction rate.


Manchester example, Manchester example, cont’dcont’d

This increased sophistication gives at least a 70% saving on the fan power consumption compared with the fans operating at full extraction continuously

Solution Modulated air extraction rates – the odour control system is able to modulate the volume of extracted air to meet the requirements

at weekends and at night the extraction rate falls to 20% of the peak rate when the doors are closed during the working day the extraction is 50% of peak rate only when the doors are open or there is a need to clear the fog in the building do the fans ramp up to

peak extraction rate.


Dispersion vs TreatmentDispersion vs Treatment

Most odours are not harmful, so atmospheric dispersion is an alternative Most odours are not harmful, so atmospheric dispersion is an alternative approach which minimises the carbon footprint of the odour control approach which minimises the carbon footprint of the odour control systemsystem

Sophisticated computer dispersion models are able to model the pattern Sophisticated computer dispersion models are able to model the pattern of odour dispersion over the locality, and predict the frequency with of odour dispersion over the locality, and predict the frequency with which specific locations will experience odour concentration above which specific locations will experience odour concentration above defined levelsdefined levels


Dispersion vs Treatment, Dispersion vs Treatment, cont’dcont’d

““Isopleths” or contour lines around the odour emission source Isopleths” or contour lines around the odour emission source represents a particular odour concentration, say 10ouE/m3 at the represents a particular odour concentration, say 10ouE/m3 at the 98%ile98%ile

This means that based on, say, 1 year’s worth of digital hourly This means that based on, say, 1 year’s worth of digital hourly recorded weather data, the isopleth indicates that for 98% of the time recorded weather data, the isopleth indicates that for 98% of the time the odour along this line will not exceed 10ouE/m3the odour along this line will not exceed 10ouE/m3


Dispersion vs Treatment, Dispersion vs Treatment, cont’dcont’d

Example: • Odour is generated from a single 10m stack with an outlet concentration of 1,000ouE/m3, • Under the Integrated Pollution Prevention Control (IPPC) H4 technical guidance note waste

water sewage works must adhere to a maximum odour limit of 1.5ouE/m3 at the 98%ile levels at locations of resident who might consider the odour a public nuisance and so complain

Dispersion is normally by-far the cheapest and lowest carbon footprint solution, instead of adding another stage of odour removal odour is simply dispersed by a taller stack

For one of the 3 Greater Manchester composting plants, the odour control stack is 37m high and the allowable odour concentration at the stack is 4,000ouE/m3

The stack might perhaps be considered a visual polluter but from the carbon footprint perspective it is a highly sustainable method of odour abatement

DispersionAlternatively to meet 1.5ouE/m3 in this example the stack height would be 26m.

Treatment

At the 10ouE/m3 isopleth line the odour has been diluted 100 times

In this hypothetical case 10ouE/m3 exceeds the required 1.5ouE/m3 level by a factor of ±7

Re-running the model indicates that a maximum odour level of 500ouE/m3 is required at the 10m stack outlet


Regenerable CarbonRegenerable Carbon

Activated carbon is ideally suited adsorbing the odour from environments of complex low solubility VOC based odour, and is able to achieve high removal efficiencies

This is the approach being used at the Greater Manchester composting sites

Benefits: the carbon is capable of being regenerated and reused up to 6 times before it is

considered spent and disposed of to landfill the physical footprint of the carbon unit is highly compact as a single annular carbon filter

3.6m diameter by 8m in height is able to treat about 80,000m3/hr of contaminated exhaust

the carbon needs only to be changed every 6 to 12 months.


Air blast cooler at RochdaleAir blast cooler at Rochdale

For Manchester, the hot wet extracted gas from the in-vessel composting area is cooled by a sub cooler direct contact scrubber to condense out up to 2m3/hr of water from the extracted exhaust and so protects the activated carbon from becoming saturated

The scrubber also washes out some of the soluble VOCs and so reduces the VOC loading onto the carbon


New lower carbon footprint New lower carbon footprint technologies technologies

HH22S adsorbing re-generable carbonS adsorbing re-generable carbon

ERG regularly installs re-generable carbon filters at waste water treatment works in the Middle East which adsorb H2S to 99% efficiency

The carbon can then be regenerated by rinsing in water washing away the leached dilute sulphuric acid back to the head of the works.

Thus the carbon can be used up to 6 times before replacement.

This re-generable technology is more complex than the straightforward caustic impregnated carbon widely in the UK which is sent to landfill once it is spent. It is likely to become more widely accepted in the coming years as landfill costs continue to escalate.


New lower carbon footprint New lower carbon footprint technologies, technologies, cont’dcont’d

Compact bio-logical filtersCompact bio-logical filtersLava rock bio-filters are able to sustain bio-media depths of up to 6m unlike wood-chip or similar bio-media which are only operate at up to 2m depth

Thus lava rock bio-filters are able to treat the same gas flow with 1/3 of the footprint while still achieving the same residence time for the gas.

Benefits

This technology has a low carbon footprint as it uses no chemicals, and its only waste is the sulphurous acid, which on a waste water works is simply returned to the head of the works

Until now, large gas flows have generally been treated by chemical scrubbing, but as the cost of chemicals rise biological systems are being preferred as both their carbon footprint and operating costs are so much cheaper



Recovery of NitrogenRecovery of Nitrogen

Benefits

As the cost of fertiliser continues to rise this option may well become attractive to waste water processors

This type of fertiliser production has a far lower carbon footprint than fertiliser generated using natural gas

Secondary waste water sludge processing, such as composting with wood chip and drying, can generate high levels of ammonia which can be converted to 30% ammonium sulphate solution by scrubbing with dilute sulphuric acid



Recovery of SulphurRecovery of SulphurAt present, most caustic bleach scrubbers are designed to convert H2S to sodium sulphate using 4 moles of bleach. An alternative stoichiometric path is to use 1 mole of bleach to form sulphur.

BenefitsThis approach uses ¼ of the bleach and so has a lower carbon footprintIt recovers sulphur which can be returned to soil

However this complicates the gas cleaning system which has to be able to operate the sulphur recovery stage by scrubbing with a slurry.



Recovery of EnergyRecovery of Energy

The composting of sewage sludge and municipal kerbside green waste generates considerable heat which could be recovered to supply hot water via heat pumps or other exchangers.

Where a local use for this hot water can be identified this significantly reduces the carbon footprint.



Integrated odour controlIntegrated odour control

Designers of odour control systems need to be constantly looking for integration opportunities so that the carbon footprint of the odour control plant can be minimised.

ERG for example has been able to use filtered final effluent (FFE) at a waste water works as the scrubbing liquor to scrub out ammonia given off from sludge stabilisation plants using lime and sludge dryers.

This alkali liquor is then directed to parts of the works where the effluent is acidic.

Benefit

Using filtered final effluent removes the need to treat the ammonia using expensive chemicals such as sulphuric acid to neutralise the ammonia.


ConclusionConclusion

Carbon footprint reduction ERG’s technology and design approach can achieve significant carbon footprint reductions at minimal additional cost.

Process integration and optimisation The Greater Manchester odour control plants, with the use of inverter driven fans properly integrated with the process they are supporting, together with the use of re-generable adsorbent media, show what can be achieved relatively simply.

Early involvement in process design The ERG approach to achieving sustainable odour control is to invest more effort into the initial stages of the design and to involve odour control suppliers earlier in the design process so that the overall optimum process plant which includes the integrated odour control, can be developed.

ERG (Air Pollution Control) Ltd www.ergapc.co.uk

www.ergapc.comwww.ergapc.com

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sustainable odour control in urban environments

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