Identifying and Controlling Odor in the Municipal Wastewater Environment Phase 2: Impacts of Inplant Parameters on Biosolids Odor Quality

Abstract

This project was undertaken in response to needs by the wastewater treatment industry to better understand the generation of odors from biosolids produced by wastewater treatment plants (WWTPs). Its primary objective is to begin to establish relationships between WWTP process parameters and biosolids odors, so that more effective techniques for minimizing biosolids odors can be developed. The project consisted of a detailed field study involving extensive sampling and analyses at 11 WWTPs across North America with capacities from 13 to 350 million gallons per day (mgd). Biosolids samples were collected from the WWTPs at a number of sampling points, which were chosen to represent a complete snapshot of biosolids generation and handling at each WWTP. The sampling points started with influent wastewater, proceeded through primary and secondary clarification, and continued through digestion, dewatering, and onsite storage of dewatered biosolids cake. Laboratory-scale anaerobic storage tests were conducted to simulate odor development of biosolids in storage, prior to their beneficial reuse or disposal. A battery of analyses were performed on the biosolids samples by the participating utility laboratories, commercial laboratories, and specialized university laboratories. The analytical data were evaluated and compared with process and operation parameters at each participating WWTP. Results indicate that the anaerobic digestion process, including its impacts on achieving stability and minimizing odors in the final biosolids product, are not yet completely understood. A significant finding was that biosolids odors after digestion and dewatering correlate with the amount of bioavailable protein in the biosolids. Possible causes for increased bioavailable protein and increased odor generation from dewatered biosolids begin with the primary and secondary sludge handling, mixing, and liquid storage steps, and continue through the anaerobic digestion process to post-digestion processes, such as dewatering, conveyance, and cake storage. A list of future research needs was also developed based on the study findings, centered on the need for more controlled experiments that can identify and quantify the impacts of different biosolids handling and stabilization processes on biosolids odor generation. ISBN: 9781780404110 (eBook)