Introduction to Odour Control Technologies
Factors affecting technology selection and system cost
Richard Hanson MA MEng CEng MIChemE
Middle East Director, ERG (Air Pollution Control) Ltd
Yousif Al-Shafie BSc AMIChemE
Senior Proposals Engineer, ERG (Air Pollution Control) Ltd
ERG (Air Pollution Control) Ltd
www.ergapc.co.uk
Introduction


About ERG
 Specialist odour control system supplier
 30 years’ experience
 UK and Middle East
About this seminar
ERG (Air Pollution Control) Ltd
www.ergapc.com
Purpose of this technical seminar
… is to help
 end-users
 consultants
 main contractors
to know the right questions to ask when specifying and buying odour control
systems
ERG (Air Pollution Control) Ltd
www.ergapc.com
Plan for technical seminar
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Summary of types of odour control system
Advantages of each system and when to use each one
Factors affecting the cost of a system
Case studies and examples
Summary – selection matrix
ERG (Air Pollution Control) Ltd
www.ergapc.com
Odour Control Technologies

3 main technologies
 Chemical scrubbing
 Dry media (activated carbon)
 Biological scrubbing
ERG (Air Pollution Control) Ltd
www.ergapc.com
Technologies | Chemical Scrubbing
Treated air outlet
Dosing chemicals
Contaminated air inlet
Purge (blowdown)
Process water make-up
ERG (Air Pollution Control) Ltd
www.ergapc.com
Technologies | Chemical Scrubbing

Used for treating
 Air from complete sewage treatment plant – air flowrate ~5,000 to
>100,000 m3/hr
 Mixed odour air – H2S, mercaptans, NH3, VOCs
 High loadings from inlet works and sludge processing

Advantages
 High efficiency scrubbing – up to >99.95%
 Flexible – good turn-down on flowrate and inlet odour loading
 Dosing chemicals use optimised
 Suitable for carbon polishing
ERG (Air Pollution Control) Ltd
www.ergapc.com
Technologies | Chemical Scrubbing

Factors affecting system size
 Air flowrate  tower diameter
 Inlet contaminant loading  recirc pump size & chemical usage rate
 Removal efficiency  tower height
 Type of contaminant  number of scrubbers
ERG (Air Pollution Control) Ltd
www.ergapc.com
Chemical Scrubbing | Cost examples
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Example: Basic Scrubber
 Air flowrate = 25,000m3/hr
 Inlet H2S conc = 100ppm max & 20 ppm average
 99.5% removal efficiency, outlet <0.5ppm
 Duty/standby fans, recirculation pumps, and dosing pumps
 Local ductwork
 Instruments, panel and controls
 Chemical storage

Approx system cost = $250,000
ERG (Air Pollution Control) Ltd
www.ergapc.com
Chemical Scrubbing | Cost examples
Design and scope
Cost
Addition
Basic system (25,000m3/hr, H2S 100ppm max and 25ppm
average, 99.5% eff)
$250k
-
Inlet H2S conc 5x larger (500ppm max & 100 ppm
average)
+$80k
+32%
Up to ~25ppm inlet mercaptans and outlet <500 ouE/m3
+$30k
+12%
Additional acid scrubber for ammonia removal (100ppm
max & 20 ppm average)
+$130k
+52%
2x air flowrate (50,000m3/hr), same H2S mass (50ppm
max & 10ppm average)
+$110k
+44%
2x air flowrate (50,000m3/hr), same H2S conc (100ppm
max & 20ppm average)
+$160k
+64%
ERG (Air Pollution Control) Ltd
www.ergapc.com
Chemical Scrubbing | Operating Costs
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Basic system
 Power (fan + pump) = 40kW
 Chemicals
= 5 litre/hr 27% caustic solution
= 33 litre/hr 15% bleach solution
 Process water
= 600 litre/hr
 Effluent (to inlet PS) = 500 litre/hr
 Operation staff
= 0.5 days/week routine
= 2-3 days/year maintenance
ERG (Air Pollution Control) Ltd
www.ergapc.com
Technologies | Carbon Dry Media
Treated air outlet
> 4 months – carbon
spent
4 months – odour
breakthrough
3 months
2 months
1 month
Start – 0 months
Contaminated air inlet
ERG (Air Pollution Control) Ltd
www.ergapc.com
Technologies | Carbon Dry Media

Used for treating
 Small air flows from wet wells, pumping stations – flowrates approx 200 10,000m3/hr
 Passive (no fan) applications
 Polishing filter downstream of chemical and biological scrubbers, flowrate
up to >100,000m3/hr
ERG (Air Pollution Control) Ltd
www.ergapc.com
Technologies | Carbon Dry Media
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Advantages
 High efficiency odour control – low outlets
 Simple and cost effective
 Upgradeable for low outlet odour, <50 ouE/m3
 Regenerable carbon – low operating cost
ERG (Air Pollution Control) Ltd
www.ergapc.com
Technologies | Carbon Dry Media
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Factors affecting size
 Air flowrate  vessel diameter
 Inlet contaminant loading * required bed life  mass of carbon
 Type of contaminant  number of media beds
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Other considerations
 Performance at breakthrough
 Water provision and effluent disposal
ERG (Air Pollution Control) Ltd
www.ergapc.com
Carbon Filters | Cost examples
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Example: Basic Carbon Filter
 Air flowrate = 2,000m3/hr,
 Inlet H2S conc = 50ppm max & 10 ppm average
 99.5% removal efficiency, outlet <0.5ppm
 Water regenerable carbon with 12 month bed life
 Vessel and duty/standby fans
 Local ductwork
 Instruments, panel and controls

Approx system cost = $30,000
ERG (Air Pollution Control) Ltd
www.ergapc.com
Carbon Filters | Cost examples
Design and scope
Cost
Change
Basic system (2,000m3/hr, 10ppm H2S average, 12 months bed life)
$30k
-
2x bed life to 24 months
+$5k
+17%
1/2x bed life to 6 months
-$3k
-10%
Additional media for mercaptans removal to <50 ouE/m3
+$5k
+17%
Duty only fan (instead of duty/standby)
-$7k
-23%
2x air flowrate (4,000m3/hr), same H2S mass (5ppm average), 12
months bed life
+$5k
+17%
2x air flowrate (4,000m3/hr), same H2S conc (10ppm average), 12
months bed life
+$10k
+33%
ERG (Air Pollution Control) Ltd
www.ergapc.com
Carbon Filters | Operating costs
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Basic system
 Power (fan)
 No Chemicals
 Regeneration water
 Effluent (to inlet PS)
 Carbon replacement
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Operation staff
ERG (Air Pollution Control) Ltd
= 2kW
= 7 m3 per year
= 7 m3 per year
= 450 kg every 5 years
(carbon cost $2,200)
= <0.5 days/month routine
= 1-2 days/year maintenance
www.ergapc.com
Technologies | Bioscrubbing
Treated air outlet
Nutrient dosing
Contaminated air inlet
Purge (blowdown)
Final effluent make-up
ERG (Air Pollution Control) Ltd
www.ergapc.com
Technologies | Bioscrubbing

Used for treating
 Media air flowrate, up to ~10,000m3/hr
 High loadings from inlet works and sludge processing

Advantages
 Good efficiency scrubbing, up to 99%+
 No chemical storage & dosing required
 Suitable for carbon polishing
 Low operating and maintenance costs
ERG (Air Pollution Control) Ltd
www.ergapc.com
Technologies | Bioscrubbing
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Factors affecting size
 Air flowrate  tower diameter
 Inlet contaminant loading  purge rate
 Removal efficiency  tower height
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Other considerations
 Response to shock loads
 Operating temperature
ERG (Air Pollution Control) Ltd
www.ergapc.com
Bioscrubbing | Cost examples
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Example: Basic Bioscrubber
 Air flowrate = 2,000m3/hr
 Inlet H2S conc = 100ppm max & 20 ppm average
 99.5% removal efficiency, outlet <0.5ppm
 Duty/standby fans, recirculation pumps
 Local ductwork
 Instruments, panel and controls

Approx system cost = $80,000
ERG (Air Pollution Control) Ltd
www.ergapc.com
Bioscrubbing | Cost examples
Design and scope
Cost
Change
Basic system (2,000m3/hr, H2S 100ppm max & 20ppm average,
99.5% eff)
$80k
-
Inlet H2S conc 5x larger (500ppm max & 100 ppm average)
+$10k
+13%
2x air flowrate (4,000m3/hr), same H2S conc (20ppm average)
+$40k
+50%
ERG (Air Pollution Control) Ltd
www.ergapc.com
Bioscrubbing | Operating costs

Basic system
 Power (fan & pump)
 No Chemicals
 Final effluent
 Effluent (to inlet PS)
 Media replacement
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Operation staff
ERG (Air Pollution Control) Ltd
= 3kW
= 100 litre/hr
= 100 litre/hr
= 24 m3 every ~10 years
(media cost $8,000)
= <1 days/month routine
= 1-2 days/year maintenance
www.ergapc.com
Odour Control Selection Matrix
Design and scope
Chemical
scrubber
Regenerable
Carbon Filter
Bio-scrubber
Basic system cost
high
low
medium
Flexibility to varying inlet load
v good
v good
moderate
Design H2S removal efficiency
>99.95%
>99.9%
>99.5%
Suitable for carbon polish
yes
-
yes
Chemical storage and dosing
yes
no
no
medium
low
medium
medium,
continuous
low, annual
medium,
continuous
weekly
monthly
monthly
continuous
continuous to
breakthrough
continuous
Power usage
Water + effluent requirement
Routine checks
Operability
ERG (Air Pollution Control) Ltd
www.ergapc.com
Summary
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Select basic type of system based on required operability and budget
System size & cost based on air flowrate and average inlet H2S load –
consultant’s estimates
Add further stages of treatment for complex inlet odour and for very low
outlet concentrations
Involve ERG early in project scoping decisions
ERG (Air Pollution Control) Ltd
www.ergapc.com
www.ergapc.com
ERG (Air Pollution Control) Ltd
www.ergapc.co.uk