Jay Witherspoon

Recent findings on biosolids cake odor reduction--results of WERF phase 3 biosolids odor research.

The Water Environment Research Foundation (WERF) has sponsored three phases of a long-term project entitled “Identifying and Controlling Odors in the Municipal Wastewater Environment.” The current (third) phase focuses on reduction of odors from dewatered biosolids cakes, and is entitled “Biosolids Processing Modifications for Cake Odor Reduction.” This phase encompasses nine research agenda items developed from the results of the prior phase of research (Phase 2), which was completed in December 2003 as WERF Report No. 00-HHE-5T and was entitled “Impacts of In-Plant Parameters on Biosolids Odor Quality.” The current phase (Phase 3) was a 2.5-year project, the first half of which was dedicated to testing several of the more promising hypotheses from Phase 2 in the laboratory to help determine the cause-effect relationships of odor generation from biosolids, and to develop odor reduction techniques. It is important to note that this research project covers the reduction or prevention of odorous emissions from dewatered biosolids cake, not odor control by means of containment or adsorption or absorption of malodorous emissions. In the remainder of the Phase 3 project, promising laboratory findings are being applied to biosolids handling processes at one or more wastewater treatment plants (WWTPs), with the goal of achieving significant cake odor reduction in a realistic, full-scale setting. The Phase 3 laboratory results were used to identify the relative effectiveness of methods for reducing biosolids cake odors, using techniques and measurements of biosolids cake odor production potential that have been developed by the WERF Project Team. Plans to demonstrate the most promising research findings at full-scale biosolids digestion and dewatering facilities constitute the final, fourth phase of the project. Contacts have been made with wastewater treatment facilities that have an interest or need to reduce their biosolids cake odors. The main goal of the next phase of the project will be to match wastewater or biosolids facilities that need to reduce biosolids odors with specific technologies, chemicals, or biological agents, in order to demonstrate the efficacy of promising laboratory findings full scale at a real WWTP.

Minimization of Odors and Corrosion in Collection Systems

Wastewater collection system odors and corrosion issues continue to grow in importance to the community and to system owners and operators. Odor and corrosion prevention in collection systems has historically been as much art as science. Common control methods are selected based on practical 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 WERF research activity helps odor-control specialists transition from “odor artists” to scientists and engineers, while also providing a useful tool both for designers to successfully prevent odor and corrosion events through proper design and for operators to mitigate and prevent odor excursions and corrosion impacts. This project transfers state-of-the-art technology and information gained from the literature survey to the collection system owner and designer on odor and corrosion assessment, measurement, characterization, monitoring, and prevention. The field studies identified in this Phase 1 effort will fill high-ranked knowledge needs. The resultant database and team-developed, web-based application tool will identify the best practices for the entire collection system and its associated facilities, infrastructure, equipment, and pipes. In addition, because odor problems are often measured subjectively by the number of public complaints, the final database and application tool will provide insights on how and why peer utilities responded and how effective their response was in solving the problem. Application tools geared for best practices related to odor and corrosion measurement, monitoring, and prevention save utility funds, allow easier asset management, and, in many cases, prevent significant environmental damage and human health impacts due to corrosion-related sewer overflows. Our proposed web-based application tool will be formed by practicing experts and utilities, “ground-truthed” by peers and others, and tested by our utility members before being offered to WERF members. This approach ensures an application tool that can be readily updated, is always current, and practically addresses any odor or corrosion-related issue. The researchers efforts to compile a current knowledge database includes information-sharing partnerships with municipal utilities, the academic community, and the profession, all on a global basis. Our team includes leading odor and corrosion control researchers in the academic, utility management, and consulting communities, and part of their role will be to provide exhaustive literature research efforts through catalogue reference, gray literature review, and Internet search mechanisms. WERF member utilities have participated in the database compilation efforts both by helping to define the database information needs, and by helping to access utility information from WERF member and nonmember utilities. A five-step approach is being used: A plain-English guide providing a useful and easily understandable overview about odor and corrosion in collection systems including how odor and corrosion compounds are formed and what to do to control them is provided as an introduction to this document. This Phase 1 report then summarizes the state of the art in knowledge related to odor and corrosion in collection systems. This highlights the latest knowledge reported in the literature. These efforts to compile the literature database have included information-sharing partnerships with municipal utilities, the academic community, and the profession, all on a global basis. Our team included leading odor and corrosion control researchers in the academic, utility management, and consulting communities, and part of their role was to provide exhaustive literature research efforts through catalogue reference, gray literature review, and Internet search mechanisms. In this way we have accessed a broad spectrum of global resources tapping into the knowledge and experience of both WERF member and nonmember utilities. This title belongs to WERF Research Report Series ISBN: 9781780403724 (eBook) ISBN: 9781843397915 (Print)

Characterization of natural ventilation in wastewater collection systems

The purpose of the study was to characterize natural ventilation in full-scale gravity collection system components while measuring other parameters related to ventilation. Experiments were completed at four different locations in the wastewater collection systems of Los Angeles County Sanitation Districts, Los Angeles, California, and the King County Wastewater Treatment District, Seattle, Washington. The subject components were concrete gravity pipes ranging in diameter from 0.8 to 2.4 m (33 to 96 in.). Air velocity was measured in each pipe using a carbon-monoxide pulse tracer method. Air velocity was measured entering or exiting the components at vents using a standpipe and hotwire anemometer arrangement. Ambient wind speed, temperature, and relative humidity; headspace temperature and relative humidity; and wastewater flow and temperature were measured. The field experiments resulted in a large database of measured ventilation and related parameters characterizing ventilation in full-scale gravity sewers. Measured ventilation rates ranged from 23 to 840 L/s. The experimental data was used to evaluate existing ventilation models. Three models that were based upon empirical extrapolation, computational fluid dynamics, and thermodynamics, respectively, were evaluated based on predictive accuracy compared to the measured data. Strengths and weaknesses in each model were found and these observations were used to propose a concept for an improved ventilation model.

Biosolids Processing Modifications for Cake Odor Reduction (Phase 3 of Identifying and Controlling the Municipal Wastewater Environment)

Phase 3 of the overall WERF project was developed to study eight Phase 2 hypotheses in more depth, beginning in the laboratory (bench-scale) studies and continuing on to targeted investigations where the WERF team manipulated plant parameters at full scale to identify the best means of reducing biosolids cake odors. The Phase 3 research specifically sought ways to enhance anaerobicly digested and dewatered biosolids to reduce the odor levels in the biosolids end product, thereby reducing negatively perceived impacts on the environment or to the public when beneficially used on land. The goal of the Phase 3 study was to provide a general application of findings to WERF subscribers who are seeking ways to reduce odors produced by anaerobicly-digested biosolids. The Phase 3 options summary present a general roadmap for wastewater treatment plant operators seeking to optimize biosolids processing and reduce biosolids cake odors. Biosolids cakes with minimal odors lead to better public acceptance near biosolids management sites and in neighborhoods adjacent to WWTPs. Reduced odors also could open the WWTP dewatered biosolids cake to other recycling or disposal opportunities that are currently not used due to odor and other concerns (including on-plant site composting or storage). Additionally, significant cost savings could be realized by not requiring extensive odor control or other expensive options for containment and management of biosolids. This title belongs to WERF Research Report Series ISBN: 9781780403694 (eBook) ISBN: 9781843397908 (Print)