Bowker & Associates, Inc.

Bowker & Associates, Inc. specializes in the assessment and control of odor emissions from waste handling facilities and industrial processes. Services include odor emission inventories, performance testing, evaluation and design of odor control systems, value engineering and independent peer reviews of odor control projects, and expert witness testimony.

Company details

477 Congress Street , Portland , ME 04101 USA

Locations Served

Business Type:
Engineering service provider
Industry Type:
Air and Climate - Air Pollution Treatment
Market Focus:
Globally (various continents)

For nearly 20 years, Bowker & Associates has provided its clients with effective odor control solutions for a variety of odor problems. Projects have included odor control at wastewater treatment plants, hydrogen sulfide corrosion control in sewers and sewage collection systems, odor mitigation at sanitary landfills, odor reduction at sludge and biosolids processing and disposal sites, and odor control for industrial processes. Bowker & Associates has also participated in multiple Value Engineering and Peer Review projects involving odor control.

Mr. Robert P.G. Bowker, P.E., has an extensive track record in the field of odor control engineering. He has over 30 years’ experience in the design and operation of wastewater facilities, and has specialized in controlling odors at waste handling facilities for the past 20 years. Mr. Bowker is considered an international expert in the control of odors and corrosion, and has co-authored numerous design manuals and papers on the subject.

Bowker & Associates is ready to meet your odor and corrosion control needs, whether it be a small sewage pumping station or a large wastewater treatment plant. When you need economical solutions to odor and corrosion problems call Bowker & Associates.


In March of 1997, a series of odor episodes prompted the City of New Bedford,
Massachusetts to study potential odor sources at the new 30 mgd wastewater treatment
plant. Bowker & Associates, Inc. was retained to conduct an independent assessment of odor emissions, to evaluate the adequacy of the design of odor control systems, and to make recommendations to control odors and reduce complaints.

A comprehensive series of odor emissions inventories led to the conclusion that the major sources of odor complaints were the solids handling scrubber, fugitive emissions from the solids handling building, and trucks hauling dewatered sludge.

Recommendations included reducing sludge inventories to control the generation of reduced sulfur compounds, improving scrubber monitoring and control systems, using fixed covers instead of fabric covers on sludge trucks, and minimizing fugitive emissions through better management and scheduling of dewatered sludge containers. A series of meetings were held with local residents that led to the formation of an odor control task force.


Bowker & Associates, Inc. worked closely with O’Brien & Gere Engineers to conduct a major study of sewer corrosion in the Henrico County wastewater collection system. The project involved an initial sampling and inspection program to identify significant odor and corrosion “hot-spots.” This was followed by more detailed sampling and both closed circuit TV and “sonic caliper” inspections to measure the extent of corrosion. Modeling was conducted to estimate corrosion rate and the useful life of the major sewers.

Recommendations included using a novel process involving upstream addition of iron salts to control hydrogen sulfide generation in the force mains, with downstream hydrogen peroxide addition to regenerate the iron. Measures for sewer rehabilitation and protection of concrete interceptors from further corrosion were also recommended.


Mr. Bowker was retained as an expert peer reviewer by Camp Dresser & McKee for the development of an odor control master plan for the 350 mgd Blue Plains WWTP serving Washington, DC. This comprehensive project involved liquid and air stream sampling, extensive odor dispersion modeling, and prioritization of odor sources based on an innovative economic analysis of unit costs for controlling the major sources. Mr. Bowker participated in three workshops with the Client at various stages of the project. A phased approach to controlling the priority odor sources was recommended.


Mr. Bowker was retained by Camp Dresser & McKee as an expert consultant for a comprehensive study of odors and corrosion in the Collier County, Florida sewer system. Due to the warm climate and flat terrain, the extensive force main system generates large quantities of hydrogen sulfide that causes odor complaints and sewer system corrosion.

A detailed sampling program was implemented involving measurement of dissolved sulfide, temperature, and pH of the wastewater, and measurement of H2S in the headspaces of sewers, manholes, and wet wells. The performance of existing odor treatment system was assessed by inlet and outlet measurements of hydrogen sulfide and odor concentration. Continuous H2S dataloggers were installed at multiple locations to measure diurnal variations in H2S concentrations.

The alternatives evaluation investigated chemical addition to the wastewater and collection/treatment of odorous air. A decision matrix was developed to assist the County in selecting the most cost-effective odor and corrosion control technique for the conditions encountered. Similarly, guidance was provided on the best techniques for rehabilitation of manholes and wet wells, and the most effective techniques for protecting against future corrosion.


Bowker & Associates was selected by the City of Los Angeles, the State of California, and the U.S. EPA to conduct an independent review of the City of Los Angeles’ sewer odor control program. This review was required as part of a Court-ordered settlement regarding odor emissions from the City’s sewer system.

The project involved multiple tasks, including a review of previous studies and on-going monitoring efforts, an assessment of existing and proposed odor control measures, an evaluation of odor complaint tracking and response procedures, and a comparison of the City’s sewer odor control program with those of other major cities.

Recommendations were prepared to improve odor monitoring and complaint tracking, enhance the chemical addition and air treatment programs, and improve the effectiveness of the Odor Advisory Board.


Bowker & Associates participated in two comprehensive assessments of odor emissions and their control at the 80 mgd Syracuse Metro WWTP. Detailed air and liquid stream sampling programs were implemented in 1992 and 2002 to characterize and rank the sources of odor emissions. In both projects, dispersion modeling was conducted to assist in prioritizing the sources based on downwind impacts. Major improvements resulting from the first study included optimization of upstream chemical addition programs, and collection and treatment of air from two headworks buildings, all open influent channels, and primary effluent weirs. The second project evaluated multiple odor control scenarios that addressed odors from the alkaline sludge stabilization system and the quiescent surface of the primary clarifiers.


In response to a lawsuit over odors and noise form a solid waste transfer station, Bowker & Associates and Webster Environmental Associates conducted a comprehensive assessment of emissions that included odorous air sampling, community odor surveys, and ambient noise surveys.

Dispersion modeling was conducted to verify existing odor impacts and evaluate various control scenarios. Recommendations included 1) capturing and treating air around the main doorway to prevent escape of fugitive odors, 2) installation of roof-mounted, high-velocity dispersion fans, and 3) installing engine mufflers and acoustical baffles.

Bowker & Associates, Inc. is an environmental engineering firm specializing in the control of odors from waste handling systems. Our knowledge of the design and operation of waste treatment processes and odor control systems offers significant advantages to our clients. We have successfully completed over 150 odor control projects throughout the United States, Canada, and abroad. Our clients include many major engineering firms such as CH2M-Hill, Camp Dresser & McKee, Metcalf & Eddy, Earth Tech, Blasland Bouck & Lee, Stearns & Wheler, and Stantec. Please see our:

Project list
Resume of Robert P.G. Bowker, P.E.

Bowker & Associates, Inc. has evaluated and designed many innovative approaches to odor control. These include construction of novel enclosures to contain odors from sludge dewatering systems, use of an existing sludge incinerator to oxidize odorous gases, implementation of economical biological systems to treat odors, and diffusion of odorous gases into activated sludge basins. In addition, the company has designed pure oxygen injection systems to prevent odorous compound generation in force mains. Bowker & Associates' commitment to providing high quality, responsive engineering services has given the company an excellent national reputation.