Background Wastewater is commonly known for its potential to create odor nuisances from a variety of sources, including odors escaping from sewer manholes, wastewater treatment facilities, and animal factory lagoons. Hydrogen sulfide (H2S), a gas detectable in very low concentrations and notable for both its toxicity and its ability to corrode various materials used in sewer and treatment plant construction, is a major source of odor in wastewater treatment systems. Traditional sanitary sewer design practice has not fully acknowledged the importance of corrosion and odor control, as evidenced by widespread occurrence of sulfide and odor control problems throughout the United States for sanitary sewers, serving both small and large tributary areas.
The EPA Needs Survey estimates the aggregate cost of major sewer rehabilitation to be US$3.2 billion. This doesn't include the cost for correcting infiltration/inflow problems, which involve major infrastructural repair or replacement of sanitary sewers, a significant part of which may be attributed to sulfide-induced deterioration. The same survey further estimates the construction costs for new collectors and interceptors through the year 2000 to be US$38.8 billion. These cost estimates reflect the importance of adequately considering sulfide control in the design of new sanitary sewer systems. Animal farmers have tried a variety of solutions to lagoon odor and continue to offer grants to universities to research solutions. Theory, Prediction and Measurement of Odor and Corrosion Evaluation of existing or potential odor or corrosion problems requires knowledge of the type of compounds likely to cause such problems and the mechanisms of their formation in wastewater systems. Hydrogen sulfide generation is inversely related to flow rate, so that waste streams with low flow rates are more likely to possess high levels of hydrogen sulfide. Where odor and/or corrosion problems exist, a monitoring program should be developed to characterize the severity of the problem. Such a program should involve careful evaluation of the data obtained from sample collection and analysis. Because collection of samples or inspection can be hazardous, plant operators and sewer workers must be familiar with the potential dangers of confined spaces in contact with wastewater, and must strictly observe appropriate safety practices, outlined later in this brochure. |
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