Minimization of Odors and Related Corrosion in Collection Systems: A Summary of the Ongoing Water Environment Research Foundation Project 04-CTS-1

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.WERF selected a research team led by King County (Washington State) and CH2M HILL to perform WERF Project 04-CTS-1, “Minimization of Odors and Related Corrosion in Collection Systems.” This team consisted of a variety of consulting engineering firms, major research universities, and publicly owned treatment works (POTWs). The two-year project is divided into three phases: Phase 1, Literature Assessment; Phase 2, Research Agenda Implementation; and Phase 3, Practitioners Guide. The Phase 1 report was submitted during fall 2006. Phase 2 is currently underway.The objective of the Phase 1 report was to transfer state-of-the-art technology and information gained from the literature survey to collection system owners and designers on odor and corrosion assessment, measurement, characterization, monitoring, and prevention. The WERF research team pulled together existing collection system odor and corrosion knowledge seen in 17 research databases including information from 33 gray literature sources supplied by utilities, manufacturers, and vendors, and a total of 485 research papers screened from well over 3000 abstracts.Highlights from the Phase 1 report included the following:a “plain-English” guide that gives a useful and easily understandable overview of odor- and corrosion-mechanisms in collection systems, including how odor compounds form, how they are measured, and how they can be controlled.advances in identifying malodorous compounds emitted from sewers, biological mechanisms through which odorous and corrosive chemicals form in sewers, and emerging measurement methods.advances in emissions modeling of wastewater collection system odors and corrosion are highlighted. Six emissions models are reviewed and their strengths and weaknesses noted. Each is examined for how well it addresses the multiple biological, chemical, and physical mechanisms and processes that cause odors or corrosion in collection systems.The existing knowledge base related to sewer ventilation is summarized. The nature and extent of air exchange (ventilation) between the ambient atmosphere and headspace of sewers may be the most important variable affecting the generation and release of odorous and corrosive gases in gravity-flow sewers.State-of-the-art techniques are summarized regarding liquid-phase odor and corrosion control approaches including mechanisms; key equations, and how various chemical control methods are being used globally.Traditional and innovative gas-phase odor treatment approaches and equipment are summarized, with a focus on pump stations and other wastewater collection system locations or structures that could potentially emit odors into the surrounding atmosphere.Corrosion mechanisms that have been described in the literature only recently and measures to control such mechanisms. Three such measures include adding coatings, most frequently on the crown of the pipe; lining the pipe wall; and installing corrosion-resistant pipe material. The many methods currently available to repair, rehabilitate, and replace wastewater collection systems are examined. Each method's appropriate uses and limitations are discussed, and the suitability of a given technology for a specific project is provided.The WERF research team's literature search and evaluation also identified 13 significant gaps in research and knowledge and suggested research to be undertaken to fill each knowledge gap. These research gaps were reviewed with WERF leadership and a survey was completed with WERF subscribers resulting in selection of the top 4 high priority research gap areas to be evaluated in the next phases of this WERF study or as follow-up collaborative research. This paper describes the ongoing work to address the top tier research gaps.