Biosolids odour emissions can affect the ability of wastewater utilities to implement beneficial biosolids processing and reuse programs. Communities often become more sensitised and vocal about biosolids issues, once they experience odours emanating from a nearby site. Odour impacts from biosolids, including potential human health effects, have been targeted recently by many national and local newspapers, citizens' groups, and regulatory agencies, who have raised significant concerns, ranging from viable disposal methods/sites to outright bans. Many national and local regulatory agencies in the United States are considering biosolids disposal bans in their communities because of misinformation, poor science, and citizen pressure, but primarily because of odour impact concerns. The wastewater industry has a relatively poor understanding of the operations and treatment parameters that influence biosolids odour emissions. Thus, wastewater treatment plants are often unable to control the odour quality of the biosolids that are delivered into communities. A research study to demonstrate the influence of anaerobic digestion, mechanical dewatering, and storage design and operating parameters on the odour quality of the final product was performed and is the subject of this paper. Established and new sampling and analytical methods were used to measure biosolids odour emissions from 11 test sites in North America. By determining the impacts of these control variables on biosolids odour quality, design and operations of anaerobic digestion systems might be enhanced. This paper also summarises a corollary study performed as part of the WERF research study that addresses the health effects of biosolids odours.
A study was performed to optimize the operation of a full-scale high solids centrifuge in terms of dewatering performance as well as the subsequent generation of odors from the biosolids cake. The results are presented in a two paper series, one dealing with the dewatering performance, and the second covering the impact on odors. This is the second paper in the series and will present how centrifuge polymer dose, polymer addition location, and torque affect the generation of odors. The concentration of odor causing compounds produced during cake storage increased as the polymer dose increased. The increased odorant production was attributed to greater amounts of bioavailable protein in the cake at the higher polymer doses, and this protein is the substrate for production of odorous compounds. Increased torque during centrifugation resulted in a proportional increase in odors during cake storage. In addition, changes in the polymer addition location affected the polymer dose. The further upstream of the centrifuge, the greater the polymer demand and subsequent odor generation. The findings are significant and show that the centrifuge torque and polymer dosage are critical control parameters and the centrifuge is a critical control point for biosolids product quality. The results of this study have led Western Lake Superior Sanitary District to develop a centrifuge operating strategy to produce a biosolids, lower in odor, to maintain a sustainable land application program.
For certain wastewater agencies, targeted research and development (R&D) on solids processing and biosolids management programs has proven to be critical to prove-out options and alternatives that appear to be better-suited to the agency's needs. These programs evolve for a variety of reasons and are often an outgrowth of previous trials and efforts by agencies, engineers, operators, academia, and technology and equipment companies. The work is often innovative in nature, since the utility is trying to develop a better result or improve on prior technology. Sometimes, significant and long-term R&D efforts have been required by an agency to overcome roadblocks or perceived process limitations. This paper presents discussion of three wastewater utilities in the US which conducted necessary R&D work to implement their solids processing and biosolids management programs. The paper concentrates on how and why the R&D work developed and the commonalities of that development, rather than on the specifics of the R&D activities, since other papers and information are available to describe the solids programs and the research work associated with these utilities.
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