Orange County Sanitation District (OCSD)
Orange County, California
This paper presents actions taken by the Orange County Sanitation District (OCSD) to
continually optimize its odor control program based upon liquid-phase dissolved sulfide
concentration, vapor phase hydrogen sulfide, vapor-phase odor and volatile organic compound
generation, and cost. Methods used to control costs include bulk chemical quality assurance and
quality control, market evaluations, flexible contracting techniques, price indexing, on-going
product comparison, and testing of new chemicals or chemical combinations. This paper will
present both the administrative measures and results of full-scale field tests.
Posted: May 20th, 2011 | Filed under: >1M, Stormwater, Waste Water Treatment | Tags: Cost Control, Increased Plant Efficiency, Optimized Odor Control Program, Reduced Odors, Treatment Optimization | No Comments »
Broomfield Wastewater Reclamation Facility
Wastewater treatment facilities in urban vicinities face the continuing challenge of reducing odor
emissions to maintain public favor. This is the case for the City and County (City) of
Broomfield Wastewater Reclamation Facility (WRF) located outside of Denver, Colorado. The
Broomfield WRF has recently undergone upgrades to proactively address odor issues but
occasionally receives odor complaints from neighboring residents. This paper presents the
findings from a thorough odor sampling campaign to evaluate odor generation and emissions at
the Broomfield WRF.
The Broomfield WRF was constructed in the 1950s in a rural area northwest of Denver. Today,
the WRF is surrounded by a large community of townhomes and houses bordering on the north
and west sides of the facility. Odor complaints are occasional and the City has implemented a
number of improvements to reduce odor emissions. The Broomfield WRF is a secondary
wastewater treatment plant that includes preliminary treatment, primary clarifiers, aeration
basins, secondary clarifiers, dissolved air flotation thickening (DAFT), anaerobic digesters,
solids handling, and ultraviolet (UV) disinfection. The facility underwent a plant-wide upgrade,
Phase 1 completed in 2005, which included the final phase of installing foul air treatment
including six odor control fans and a BIOREM biofilter. This recent study focused on
identifying emission sources at the plant and providing recommendations for the Phase 2
The odor study involved an intense liquid and gas sampling effort that included gaseous and
liquid phase sulfide, air pressure evaluations in rooms and covered tanks, Nasal Ranger® testing
of facility boundaries, and smoke testing of the existing biofilter which treats the foul air from
the process buildings. The main sources of odors were detected around the digesters, in the
digester gas, and in the centrate liquid stream and holding tank foul air. Gas from the digesters
measured around 2,000 ppm hydrogen sulfide (H2S) and the gas from the centrate holding tank
measured 100 ppm H2S. Also, the influent stream of the facility showed unusual daily spikes in
H2S gas and it is very possible that wastewater from one of the collection system lift stations is a
major contributor to the high influent sulfide in this stream. The biofilter had little odor and
appeared to effectively treat the facility’s foul air. However, during the smoke testing, there was
a noticeable separation of the smoke on the surface of the filter media although there are no
partitions to separate the air flow. The main recommendations from the odor study included the
• System Negative Pressures. Increase exhaust air flow from buildings and covered tanks
to ensure negative pressure and avoid fugitive emissions.
• Sulfide Spikes. Confirm that the cause of the afternoon sulfide spike at the influent
channel is an upstream pump station operation.
• Digesters. Consider ferric chloride addition to reduce sulfide concentration in the sludge
and consequently in the digester gas and in the dewatering centrate.
• Centrate Recycle. Consider rerouting centrate recycle stream to an aerobic zone of the
• Biofilter. Check air pressures and conduct smoke tests at least every year.
Overall, the study found that the facility has improved its odor emission with recent upgrades
and odors detected at the facility were minimal. The biofilter appears to be providing effective
treatment of the collected foul air. The proposed upgrades for Phase 2 are generally in line with
the findings from this study and will further improve odor control.
Posted: May 3rd, 2011 | Filed under: Waste Water Treatment | Tags: Effective Treatment of Odor Emissions, Improved Customer Service, Plant Improvement, Reduced Odors | No Comments »
Manteca Wastewater Quality Control Facility
City of Manteca, California
The Manteca Wastewater Quality Control Facility (WQCF) is a 6.5-million gallons per day (mgd) rated
activated sludge plant. The WQCF treats typical municipal wastewater generated in the City of Manteca,
California and the neighboring City of Lathrop. The plant also receives seasonal discharges from a local
food processor. Over the last few years, the Manteca WQCF underwent a $60-million expansion to increase
its capacity from 6.5 to 9.87 mgd. Part of this expansion included the construction of a new influent pump
station with two mechanical screens, and a new dewatering building with two centrifugal dewatering
systems. Because housing developments within the City of Manteca are encroaching upon the plant, and a
new regional softball complex was constructed nearby, an odor control system needed to be designed and
built during the plant expansion to ensure that potential odor complaints from neighbors would be
minimized. Foul air from the influent pump station and the dewatering building is conveyed through large
ducts into a new open bed lava rock-based biofilter near the influent pump station. The biofilter is
composed of five beds, including one used as standby. The four duty beds were designed to treat 33,000
cubic feet per minute of foul air. Approximately 2,100 cubic yards of lava rock were needed for the
biofilter. To the authors’ knowledge, this open bed lava rock biofilter is the first and largest full scale
biofilter of this type in the nation.
Posted: May 3rd, 2011 | Filed under: 50k-100k, Waste Water Treatment | Tags: Biofiltration, Reduced Odor Complaints, Reduced Odors, Signifcantly Reduced Maintenance Requirements | No Comments »
Solid Waste Authority of Palm Beach County
Palm Beach County, Florida
The Solid Waste Authority of Palm Beach County, Florida, operates an in-vessel composting
facility that processes 30 dry tons/day of dewatered biosolids combined with shredded yard
waste. The facility consists of 36 aerated agitated bays in three buildings supplied by
International Processes Systems (Now Siemens Water Technology). All exhaust air from the
buildings is treated in three 60,000 cfm biofilter cells. New biofilter cells were commissioned in
December 2002. Design and construction included some innovative features including: use of
locally available limestone for the support plenum, use of locally available finely ground bark
mulch in the media, a pre-humidification system with air-atomizing nozzles, clean-outs for every
perforated lateral, and a fast-track design-build method of delivery.
After start-up the well water used for humidification caused rapid scaling of the laterals, due to
the high mineral content and high evaporation efficiency. Pre-humidification was discontinued
while a water softening and deionization system was under consideration. Since then the filters
have been operated only with surface irrigation. The most recent rounds of performance testing
have indicated that surface irrigation, combined with rainfall, were sufficient to maintain optimal
moisture content throughout the full depth of media. Without pre-humidification, the irrigation
distribution pattern is critical.
The filters have been periodically tested for odor and ammonia removal, most recently in 2006
and scheduled again for 2007. The filter media in the different cells have been in continuous use
for 2.6 to 3.1 years. Typical inlet conditions were:
Temperature: dry-bulb range 96-105 deg. F. wet-bulb range 86-92 deg F.
Ammonia: 22 – 40 ppm
Hydrogen sulfide and methyl mercaptan: neglible or non-detect
Odor concentration: 1,500 – 2,400 D/T, using the prEN 13725 olfactometry standard.
The biofilters have consistently removed 100 % of ammonia and 93 – 98 % of odor with outlet
odor concentrations in the range of 66 to 86 D/T. Thus, the biofilter is showing highly effective
performance, despite the high temperature and moisture deficit in the inlet air. As a result, the
composting facility is no longer a significant source of off-site odors.
Ammonia is an alkaline gas and there little acid gas present. The media has a pH in the range of
4.8 – 6.8. The acidic pH indicates that alkalinity is being consumed as a result of nitrification. A
nitrogen mass balance indicated that the biofilters are operating in steady state rather than
accumulating nitrogen, and that nitrogen leaves the biofilters by way of leachate and
denitrification. Denitrification was demonstrated by the detection of nitrous oxide. Nitrous oxide
is of increasing interest due to its effect as a greenhouse gases.
Posted: May 3rd, 2011 | Filed under: Uncategorized | Tags: Biofiltration, Reduced Air Pollutants, Reduced Greenhouse Gas Emissions, Reduced Odors | 1 Comment »
In this paper, the results of the process of designing, installing and commissioning the
full-scale biofilter systems will be discussed. All of the biofilter system utilized an
inorganic synthetic media. The objective of this paper is to emphasize major pitfalls in
specifying full-scale biofilter systems, wherein the impact of inlet concentration on
treatment efficiency is often ignored, and simultaneous treatment requirements of exit
odor levels as well as treatment efficiencies for hydrogen sulfide and each of the major
reduced sulfur compounds are required to be met by the full-scale system. The major
differences between the performances of a biofilter, thermal oxidizer and chemical
treatment systems will be discussed, with special emphasis on correctly specifying
biofilter systems to meet the goals of odor control at a wastewater treatment plant.
Posted: May 3rd, 2011 | Filed under: Uncategorized | Tags: Improved Installation and Operation for Biofiltration, Increased Efficiency, Reduced Air Pollutants, Reduced Odors | No Comments »
Sausalito-Marin City Sanitary District
The 1.8 MGD (ADWF) Sausalito-Marin City Sanitary District (SMCSD) wastewater treatment
plant is situated on a small (approximately 2.5-acre), constrained site on the San Francisco Bay.
The plant has numerous odor sources that impact nearby residents and cause odor complaints.
Spray masking agents installed in 2003 and liquid phase treatment systems have been marginally
effective in controlling offsite odors. Customer surveys determined that odor control from the 50
year-old treatment plant was an important community goal and SMCSD Board of Directors
authorized funding and implementation of state of the art odor control measures.
An odor study was completed in 2004 that identified the major odor sources at the plant and
made recommendations for odor control improvements. The SMCSD initiated an odor control
improvements project immediately thereafter for addressing and controlling plant fugitive odor
emissions. The initial concept design phase selected biotechnology as the preferred odor control
technology based primarily on performance, safety, and ease of operation.
During the detailed design phase several significant challenges surfaced, including the extremely
limited footprint available at the site for new odor control facilities. This challenge was met by
selecting small footprint bioscrubbers that would be installed on the roof of an existing control
building. This decision triggered a seismic analysis of the existing control building (constructed
in 1981), since local seismic criteria had since changed significantly since it was constructed.
Structural roof improvements were implemented, coupled with the selection of multiple lightweight
bioscrubbers (to spread the load). Roof weight limitation, equipment comparative
performance assessment, and schedule issues drove the project to procure the bioscrubbers via a
sole-source arrangement. Ongoing plant improvements that were impacting detailed odor control
design had to be carefully coordinated.
Two major design changes produced a significant cost savings for the project. First, a decision
was made to reduce the primary clarifier cover to a launder-only cover. This accomplished a
desire of plant staff to minimize confined spaces (for ease of maintenance and renewal and
replacement efforts). In addition, there was an expected benefit that planned ferric chloride
addition to plant influent would have on both primary clarifier performance and reduction of
hydrogen sulfide (H2S) related odors. Second, the design team reversed the fixed film reactor air
flow (air flow was changed to a vertical downward direction)_in order to delete the requirement
for a fixed film reactor cover from the project (the downward flow pattern was expected to
reduce fugitive emissions from the open top). These cover cost savings alone were realized at
over $300,000 for the overall $1.5 million dollar project.
During the construction phase of this project additional challenges surfaced, including an
accelerated deteriorating vehicle access causeway that required the contractor to adjust
construction work approaches. In addition, due to limitations related to access at the plant, an
ocean barge and crane was used via San Francisco Bay to hoist the bioscrubber equipment onto
the roof of the existing control building. Finally, more stringent plant effluent permit
requirements imposed by the local water board required that treated plant effluent, designed to be
utilized for bioscrubber irrigation, be chlorinated to greater than 5 parts per million (ppm) Cl-, a
level exceeding that recommended by the bioscrubber manufacturer. This required that a
separate non-chlorinated pumped irrigation system (secondary effluent) be implemented as both
an irrigation and nutrient source.
The various challenges encountered during implementation of the odor control improvements at
the SMCSD were met with ingenuity, creativity and perseverance by both plant staff and the
engineering consultant. This allowed the project to move forward, meeting both schedule and
budget constraints, and accomplish the project goal of mitigating offsite odors while building
community trust and demonstrating that SMCSD is acting as a good neighbor.
Posted: May 3rd, 2011 | Filed under: <50K, Waste Water Treatment | Tags: Biotechnology, Cost Savings, Effectively Dealing with Odor Control Challenges, Improved Customer Relations, Reduced Hydrogen Sulfide, Reduced Odors | No Comments »
Pima County Regional Wastewater Reclamation Department
Pima County, Arizona
Pima County Regional Wastewater Reclamation Department (PCRWRD) manages a sewer
conveyance system that includes over 3,300 miles of sewer pipes, 66,000 manholes and 29 active
lift stations. PCRWRD operates two major wastewater treatment facilities within the Tucson
metropolitan area, the Roger Road Wastewater Treatment Plant (Roger Road) and the Ina Road
Water Pollution Control Facility (Ina Road). Odor abatement and control across the entire system
is a major issue facing the department as many odiferous compounds, primarily hydrogen
sulfide, are generated from the conveyance and treatment of sewage.
PCRWRD has initiated a System-wide Odor Control Planning effort to develop a holistic,
fiscally sound and implementable Plan to mitigate county wide odor problems. The planning
effort was structured to identify both near term and long term solutions for the odor emissions.
The near term solutions are those that can be readily implemented, either by staff or by Job Order
Contract. The near term solutions are intended to give maximum immediate relief from nuisance
odor emissions at minimum cost.
The long term solutions are those that require significant capital investment, integration and
coordination with other long term facility expansions or improvements and which require
significant design lead time and construction procurement activities.
The odor emissions from the Roger Road WWTP have lead to numerous odor complaints from
residents and businesses in the area surrounding the plant for quite some time. Due to the
severity of the nuisance odor emissions, PCRWRD determined that a “Quick Fix” for odor
emissions from the Roger Road WWTP was a must.
Therefore, early efforts in the System-wide Odor Control Plan focused on measures to identify
and mitigate the most sever sources of odor emissions from the Roger Road WWTP.
This paper will focus on aspects of developing a “Quick Fix” for Odor Control at the RR
WWTP, including the following:
● Development of baseline odor sources and emission characterizations
● Development of a “Quick Fix” odor control strategy and an implementation plan
● Cooperative effort between PCRWRD, Consultant Team and JOC Contractor to
implement the “Quick Fix” plan
● Results of the “Quick Fix” Odor Control at the PCRWRD Roger Road WWTP
Posted: May 3rd, 2011 | Filed under: 500K-1M, Waste Water Treatment | Tags: Improved Odor Control Plan, Maintaining Good Neighbor Relations, Reduced Hydrogen Sulfide, Reduced Odors | No Comments »
Sub-Regional Operating Group
Glendale, Mesa, Phoenix, Scottsdale, and Tempe, Arizona
The Sub-Regional Operating Group (SROG) is a five-city partnership formed to facilitate the
joint ownership and operation of a wastewater conveyance and treatment system in the Phoenix
metropolitan area. The cities of Glendale, Mesa, Phoenix, Scottsdale, and Tempe are party to
this partnership, which applies to a jointly owned regional wastewater treatment plant (WWTP)
and two major interceptors. These two interceptors, Salt River Outfall (SRO) and Southern
Avenue Interceptor (SAI), run parallel, east-west collecting wastewater to be ultimately
conveyed to the regional 91st Avenue WWTP, located in the southwest corner of the Phoenix
area. The SRO and SAI interceptors are each over 20 miles long with pipe sizes ranging from 48
to 90 inches in diameter. As a result of wastewater temperature, travel time, and development,
the numbers of odor complaints are rising from residents near the interceptors. SROG conducted
odor studies for both interceptors in the year 2003. The studies recommended implementation of
odor control facilities to exhaust and treat the headspace foul air at several locations along the
interceptors. Odor control measures are in the concept stage and have not yet been implemented.
In recent studies, between 2005 and 2007, SROG has identified hydraulic capacity limitations in
the SRO and SAI interceptors that may compromise their conveyance efficiency under both dryand
wet-weather conditions. A study is currently being conducted to identify regional
municipality specific solutions to manage the interceptor capacity issues. The solution is
anticipated to include a combination of measures aimed at reducing inflow and facilities that will
permit a controlled discharge of wastewater into the interceptors. As a result, a relatively steady
wastewater flow is expected to be achieved in the interceptors. This new flow regime and its
impact on pipe headspace air volume are discussed in the paper.
Wastewater flow variations in a sewer pipe go accompanied with fluctuations of the headspace
air volume. These volume fluctuations increase the potential for sewer headspace pressurization
during wastewater level rises, increasing the potential for odor release out of the interceptor
(sewer out-gassing). The paper concludes that wastewater and rainfall derived inflow and
infiltration (RDII) management programs, typically focused on optimizing the hydraulic capacity
of collection systems, should be expanded to include an assessment of their impact on odor
release potential along the collection system. Odor generation and headspace air transport
modeling should be run in parallel with the system hydraulic model so that appropriate decisions
can be made to solve sewer pipe flow capacity and odor release issues in a concerted effort.
Posted: May 3rd, 2011 | Filed under: >1M, Sanitary Sewer, Waste Water Treatment | Tags: Improved Air Quality, Improved Customer Relations, Maximize Collection System Performance, Reduced Odors | No Comments »
Palm Beach County Water Utilities Department
West Palm Beach, Florida
Palm Beach County Water Utilities Department (PBCWUD) wished to control odor emissions from the
Southern Region Water Reclamation Facility (SRWRF) in response to citizen concerns. The primary
goal of this project was to enhance community relations. The objectives were to determine the source(s)
of odor emissions that could affect the plant’s neighbors and develop cost-effective control methods for
The SRWRF is a 35 million gallons per day (MGD) facility (based on three month average daily flow)
treating an average of 24.3 MGD of wastewater from a large part of Palm Beach County. The treatment
processes include screening and grit removal, step-feed aeration and final clarification. The effluent is
then filtered, disinfected with chlorine and discharged to the reuse water system. Effluent not discharged
to the reuse water system is either used to sustain two wetlands adjacent to the plant site or is injected
into deep wells. Sludge is thickened, anaerobically digested and dewatered using belt filter presses. The
dewatered cake solids are used on farmland or placed in a landfill.
Odor control was already in place for the headworks and the solids handling facilities at the plant.
Treatment of the foul was provided by one two stage packed bed caustic scrubber systems at each
location. Sampling was conducted on potential odor sources at the plant. The odor samples were also
tested for specific odor-causing compounds. Modeling of the odor source information indicated that the
aeration basins were the most significant sources of off-site odors, followed by the headworks scrubber.
The aeration basins are operated in the step feed mode. Each of the four basins is divided into four
channels. The return activated sludge (RAS) is introduced at the head of the first pass of each basin.
Raw wastewater is currently fed at the head of each of the four passes in each basin.
Three general methods for controlling the odor were explored. These methods were:
1. Reducing the hydrogen sulfide loads by adding chemicals to the collection system to
reduce dissolved sulfide
2. Adjusting the operation of the plant to reduce odors
3. Capturing and treating malodorous air
The addition of chemicals to the collection system successfully reduced the dissolved sulfide entering
the plant, but no corresponding reduction in odor emissions was observed. Adjustments in the operation
of the plant were made and the impact on the odor emission rates was measured. Operational changes
evaluated include relocating the return sludge feed point from the first pass of an aeration basin to the
headworks channel and changing the operation of the aeration basins from step feed to plug flow.
Rerouting of the RAS proved to be inconclusive for reducing odor emissions from the aeration basins.
Converting the aeration basins from step feed to plug flow did reduce the overall odor emissions from
The remaining odor emissions from the aeration basins will be controlled by capturing and treating the
foul air. A phased plan that involves covering portions of the aeration basins and treating the foul air has
been developed in the event that the operational adjustments are unsuccessful in controlling odor
This paper will present the base odor emission data and the impact of chemical addition in the collection
system on the aeration basin odor emission rate as well as the results of the proposed operational
changes on the odor emission rate. The results of a life cycle cost analysis of the possible solutions will
also be presented.
Posted: May 3rd, 2011 | Filed under: 100K-500K, Waste Water Treatment | Tags: Captured and Treated Malodorous Air, Improved Customer Relations, Reduced Hydrogen Sulfide Loads, Reduced Odors | No Comments »
Polluted air streams nearly always contain a mixture of many compounds. These compounds are
usually different in, for example, water solubility and biodegradability, which result in important
consequences for its removal potential.
To remove all pollutants from an air stream using biotechnology, a mix of micro-organisms is
required. Micro-organisms differ from each other by their capacities to use energy, carbon and
nutrients sources. In addition, the optimal environmental conditions for the micro-organisms
required are unfortunately not the same for all micro-organisms.
Therefore, depending on the many compounds in the air stream, a mix of micro-organisms is
required and different environmental conditions for the micro-organisms result in a more
efficient biological air treatment system.
Multi-layered bioreactors can provide these different environmental conditions, which are
difficult to obtain and maintain in conventional biofilter systems. High odor removal efficiencies
(>98%) and low outlet odor concentrations (<1000 OU) have been obtained in full-scale
applications at a relatively small footprint. Reactor design, however, as well as operating strategy
is critical for success as outlined in this paper.
Posted: May 3rd, 2011 | Filed under: Waste Water Treatment | Tags: Improved Biological Air Treatment, Improved Customer Relations, Increased Odor Removal Efficiency, Low Operating Costs, Reduced Odors, Relatively Small Carbon Footprint | No Comments »