Wastewater collection system odor and corrosion issues continue to grow in importance to
communities and to conveyance system owners and operators. Odor and corrosion prevention in
collection systems has been as much art as science. Common control methods are typically
selected based on field experience as opposed to a fundamental understanding of why and when
methods will be successful. Although much is known regarding the cause of odorous gases in the
collection system, the underlying science and mechanisms of odor generation, sewer ventilation,
odor characterization and monitoring, and corrosion mechanisms need further research. This
Water Environment Research Foundation (WERF) research project helps the industry transition
from “odor artists” to scientists and engineers, enabling designers to successfully prevent odor
and corrosion events through proper design and for operators to mitigate and prevent odor
excursions from existing systems.
Posted: May 3rd, 2011 | Filed under: Sanitary Sewer, Stormwater, Waste Water Treatment | Tags: Corrosion Prevention, Improved Customer Relations, Odor Characterization and Monitoring, Odor Prevention, Sewer Ventilation | No Comments »
City of Mesa
City of Mesa, Arizona
In 2001, a new three-barrel siphon was constructed under Arizona Highway 101 on the western
boundary of the City of Mesa. This area is at the intersection of a major east-west thoroughfare
and loop highway in an area of dense commercial development. The siphon handles an average
30 million gallons per day (MGD) through a 54-inch gravity interceptor. A 24-inch air jumper is
provided within the Baseline Road overpass structure. Shortly after commissioning the siphon,
strong odors and numerous complaints were received in the vicinity of the siphon. A packaged
biofilter was installed to treat odors extracted from the siphon tail box. Testing showed it
achieved greater than 98% hydrogen sulfide (H2S) removal. However, poor treatment of reduced
organic sulfur compounds caused continued odor complaints. A new multistage bioscrubberbiofilter
system with added airflow capacity was the best option for improved odor control, given
the extraordinarily high H2S concentrations of greater than 100 parts per million (ppm) in this
part of the interceptor system. The new, higher airflow system was installed on the head end of
the siphon to achieve improved fugitive emissions control in the upstream interceptors. The new
system design incorporated a new inorganic media biofilter, preceded by a bioscrubber, and
located on the upstream side of the siphon. Performance testing of the bioscrubber, operating at
seven second residence time and pH 2 circulating solution, indicated greater than eighty percent
removal efficiency for H2S. Removal of reduced organic sulfur compounds such as mercaptans,
was negligible in the bioscrubber because of the low operating pH, but over 90% effective in the
inorganic media biofilter. Overall H2S removal exceeded 99.9%.
This project included several notable design features, including a cover system for the abovegrade
biofilter, enabling the treated exhaust gases to be discharged through a stack or drawn
through third stage activated carbon treatment. This enables improved vertical plume dispersion
and greater dilution of treated exhaust gases, or polishing of the exhaust. The project achieved
several goals including achieving extremely high odor removal in a robust multistage treatment
system with minimum available space, and blending the architectural features of the system into
the immediate surrounding area.
Posted: May 3rd, 2011 | Filed under: Waste Water Treatment | Tags: Efficient Biological Treatment System with Minimal Space, Improved Customer Relations, Improved Odor Control, Improved Vertical Plume Dispersionm | 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 »
A roadmap to reduce biosolids cake odors was developed under the WERF Phase 3 Project 03-
CTS-9T entitled “Biosolids Processing Modifications for Cake Odor Reduction” encompasses
nine research agenda items developed from the results of Phase 2, which was completed under
WERF Project No. 00-HHE-5T (Adams et al, 2003). Phase 3 has been a 3-year project dedicated
to testing hypotheses in the laboratory as well as on pilot-scale and full-scale bases, to determine
the causes and biosolids odors and find ways to remediate them. The Phase 3 project has
concluded and the Final Report was published in late 2007.
Laboratory and full-scale investigations conducted in Phase 3 that helped develop a biosolids
cake odor reductions roadmap included:
1. The role of cations in odor production from anaerobically-digested biosolids
2. The effect of anaerobic digestion parameters such as mixing, detention time, temperature,
and phasing on cake odor production.
3. Effects of dewatering processes and their control parameters on cake odors
4. Effects of chemical addition on cake odors
Demonstration of promising research findings at full-scale biosolids digestion and dewatering
facilities were undertaken in Phase 3. The main goal of this last phase of the project was to
develop a biosolids cake odor reduction roadmap. This roadmap matches wastewater or
biosolids facilities that need to reduce biosolids odors with specific technology solutions,
potential changes in operational practices, and/or chemicals, or biological agents additions. Each
biosolids processing facility or wastewater treatment plant (WWTP) will need to determine their
own biosolids cake odor reduction goal, which is typically determined by either
reducing/eliminating surrounding site or application location odor complaints or set using odor
dispersion modeling to demonstrate that the odor threshold goal is met at the sites property line.
The roadmap provides several approaches to meet any level of biosolids cake odor reduction
needed to meet reduction goals. Typically a combination of roadmap approaches, such as
technology, operational, and/or chemical strategies are needed to meet higher cake odor
reduction requirements. Whereas, for smaller cake odor reduction needs, only one or several
roadmap approaches are needed. All roadmap approaches are independently viable and have
shown cake odor reductions. Several WWTPs are currently looking at the roadmap concept to
meet needed biosolids cake odor reduction needs. WERF is considering adding another phase to
this project to roll-out and fine-tune the roadmap concept at a WWTP. To date, parts of the
roadmap have been used by WWTP to meet their biosolids cake odor reduction needs.
Posted: May 3rd, 2011 | Filed under: Uncategorized | Tags: Improved Customer Relations, Improved Plant Operations, Reduced Biosolids Cake 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 »
San Francisco Public Utilities Commission
San Francisco, California
When the City and County of San Francisco (City) first began its land application program in
Solano County in 2000, it was with an eye toward a sustainable future. Significant odors and
truck traffic were generated near a newly developed retirement community, and outraged citizens
were quick to complain about the land application practices to Solano County staff. By winter of
2002, it appeared that the practice of land application in Solano County was over. The San
Francisco Public Utilities Commission (SFPUC), along with its sister agency, the East Bay
Municipal Utilities District (EBMUD), moved swiftly to begin engaging with stakeholders. The
end result was a revised local ordinance that addressed public concerns associated with noise,
traffic, and odors, but allowed continued Class B land application. Since that time, the two
agencies have continued to engage with the community by participating in routine biosolids
stakeholders meetings and meeting annually with the Solano County Board of Supervisors. In
addition, San Francisco has taken a more proactive role in managing its biosolids. Initiatives
include enrollment in the National Biosolids Partnership’s Environmental Management System
program, inspections of land application sites, increased biosolids monitoring, and participation
in biosolids stakeholder group meetings. The Solano County ordinance that allows Class B land
application was recently extended for another five years, an achievement that would likely not
have been possible without the extensive outreach efforts of San Francisco and other Bay Area
Posted: May 3rd, 2011 | Filed under: >1M, Waste Water Treatment | Tags: Enhanced Interaction with Stakeholders, Improved Customer Relations, Improved Plant Sustainability, Plant Optimization | No Comments »
Recent introduction of more efficient dewatering devices that generate higher solids
concentrations in dewatered cake has been plagued with the non-desirable side effect of more
odorous dewatered biosolids. Previous research has shown that the production of volatile organic
sulfur compounds (VOSC’s) such as methanethiol (MT), dimethyl sulfide (DMS), and dimethyl
disulfide (DMDS) during dewatered biosolids storage is one of the major contributors to
nuisance odors from anaerobically digested and dewatered biosolids. This research also
indicated the importance of methanogens in the degradation of VOSC’s, in which VOSC’s
increase dramatically if methanogens are inhibited. In addition, methanogenic microorganisms
can degrade the VOSC’s, and they are the reason that VOSC concentrations begin to decrease
after reaching a peak that usually occurs at 7-14 days of cake storage. Research has shown that
odor reducing methanogens present in digested biosolids require time to re-acclimate in stored
biosolids cake after dewatering. Biological seeding of freshly dewatered biosolids with stored,
acclimated biosolids was hypothesized as a means of reducing VOSC’s and odors more rapidly
in biosolids cake than if the biosolids were stored without additives. A study was performed in
order to test this hypothesis. Results from this study showed significantly lower concentrations
(greater than 75% reduction of odorous compound concentrations) in as little as 3 days of
storage as compared to un-amended fresh biosolids cake, which required 10 days for
concentrations of MT and DMS to decline to similar levels.
Posted: May 3rd, 2011 | Filed under: Waste Water Treatment | Tags: Biosolids Cake Odor Reduction, Improved Customer Relations, Reduced Odors During Transport and Land Application, Reduced Volatile Organic Sulfur Compounds | No Comments »
Greenfield Water Reclamation Plant
A unique partnership of Owners, Engineers and Architects, and Contractors worked together for
the successful implementation of the Greenfield Water Reclamation Plant (GWRP) to meet
increased wastewater treatment capacity and reuse water supply requirements. The project team
faced several challenges ranging from local community integration, dramatic and on-going cost
escalations, and the need for a regional biosolids management solution. The project created an
architectural design that flawlessly blended the solids treatment facility with the surrounding
upscale residential community. Balancing the capital cost constraints with the functional needs
of the facility helped to keep the project within the Owner’s budgetary constraints. An
innovative project delivery method – Construction Manager at Risk (CMAR) – allowed the three
owners, the joint venture CMAR contractor, and the multiple architectural and engineering firms
to achieve a successful balance. The project achieved a regional biosolids management solution
by linking together the Mesa Southeast Water Reclamation Plant (SEWRP), a remote treatment
facility, and the GWRP using a solids pumping facility and a solids pipeline.
Posted: May 3rd, 2011 | Filed under: Waste Water Treatment, Water Treatment | Tags: Biosolids Management, Cost Savings, Energy Savings, Improved Customer Relations, Plant Optimization, Plant Sustainability | No Comments »