Sustainable Odour Control in Urban
Environments
James Scott-Bowden MBA, BSc (Hons)
Managing Director, ERG (Air Pollution Control) Ltd
ERG (Air Pollution Control) Ltd
www.ergapc.co.uk
Introduction

About ERG

Leading specialist odour control and air pollution
control supplier

Odour control systems - UK and Middle East waste water and
recycling industries

Air pollution control - wide range of global industries

More than 30 years’ experience

UK headquarters and Middle East based subsidiary

Global network of V-texTM technology licensees

Maintenance division supplying maintenance services
for odour control and air pollution control systems

Consultancy services to assist clients with the
specification of their air pollution or odour control
requirements
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Trends in the municipal sector
With increasing focus on sustainability, the municipal sector is increasingly locating
recycling and treatment facilities:
in urban environments to be closer to their waste sources, and
 housing facilities in enclosed buildings

Challenges for the odour control industry:
Efficiency – the need is for ever more efficient odour extraction technologies to
minimise any odour nuisance to their residential community neighbours
 Carbon footprint - cost pressures (and social responsibility) drive need for more energy
efficient odour control systems for reduced carbon footprint

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Cost 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.
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Municipal recycling example - Manchester
Odour control system need to be designed such that operators can minimise
the energy consumption whilst still providing maximum odour removal to
avoid complaints.
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)
at Rochdale, Bredbury and Trafford Park
ERG (Air Pollution Control) Ltd

Rochdale processes 750 tonnes of green waste together
and 50 tonnes of food waste per week, and converts this
into about 600 tonnes of top soil suitable for agricultural
use by employing a composting and maturation process
which takes about 8 weeks.

The Bredbury and Trafford Park facilities are
approximately twice as large as Rochdale.
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Manchester example, cont’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.
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Manchester example, cont’d
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.
This increased sophistication gives at least a 70% saving on the fan power consumption compared with the
fans operating at full extraction continuously
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Dispersion vs Treatment

Most odours are not harmful, so atmospheric dispersion is an alternative
approach which minimises the carbon footprint of the odour control
system
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Sophisticated computer dispersion models are able to model the pattern
of odour dispersion over the locality, and predict the frequency with which
specific locations will experience odour concentration above defined
levels
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Dispersion vs Treatment, cont’d

“Isopleths” or contour lines around the odour emission source
represents a particular odour concentration, say 10ouE/m3 at the
98%ile

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 the odour
along this line will not exceed 10ouE/m3
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Dispersion vs Treatment, cont’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
Treatment
At the 10ouE/m3 isopleth line the odour has been diluted 100
times
Dispersion
Alternatively to meet 1.5ouE/m3 in this example the
stack height would be 26m.
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
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
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Regenerable 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.
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Air blast cooler at Rochdale
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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
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New lower carbon footprint technologies
H2S 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.
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New lower carbon footprint technologies,
cont’d
Compact bio-logical filters
Lava 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
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New lower carbon footprint technologies,
cont’d
Recovery of Nitrogen
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
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
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New lower carbon footprint technologies,
cont’d
Recovery of Sulphur
At 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.
Benefits
This approach uses ¼ of the bleach and so has a lower carbon footprint
It 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.
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New lower carbon footprint technologies,
cont’d
Recovery 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.
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New lower carbon footprint technologies,
cont’d
Integrated 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.
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Conclusion
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.
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Thank you for your attention.
Any questions?
www.ergapc.com
ERG (Air Pollution Control) Ltd
www.ergapc.co.uk