IMPACTS OF IN-PLANT OPERATIONAL PARAMETERS ON BIOSOLIDS ODOR QUALITY: PRELIMINARY RESULTS OF WERF PHASE 2 STUDY

CH2M HILL and the Sanitation Districts of Los Angeles County are co-principal investigators on a research project sponsored by the Water Environment Research Foundation (WERF), Identifying and Controlling the Municipal Wastewater Odor Environment. Phase 1 of the project concluded in early 2002 with the results and conclusions of an extensive literature search and a prioritized research agenda for further field investigations (publication of the Phase 1 report is expected in early 2003). Odors from anaerobically-digested biosolids ranked the highest in priority among all wastewater odor issues in a workshop held by the WERF Project Team and municipal representatives to present and discuss the findings of Phase 1 of the WERF Odor Study.Biosolids odor emissions can impact the ability of wastewater utilities to implement beneficial biosolids processing and reuse programs. Communities often become more sensitized and vocal about biosolids issues once they experience odors emanating from a nearby facility. Odor impacts from biosolids, including alleged human health effects, have been targeted recently by many national and local newspapers, citizens groups, and regulatory agencies.The research team for Phase 2 of the WERF Odor Study has collected field data and established some trends (as well as refuted other anecdotal trends) that examine the influence of anaerobic digestion system design and operating parameters on the odor quality of the final biosolids product. Anaerobic digestion is the most widely practiced biosolids stabilization process in the U.S. on a total, biosolids-weight basis, and thus was chosen as the focus of the WERF Phase 2 Biosolids Odor Study.The researchers attempted to correlate process conditions (storage, anaerobic digestion, and mechanical dewatering) and biosolids characteristics with odor emissions. Established and new sampling and analytical methods were used to measure odor precursors in the liquid and gaseous phases of the biosolids produced under a variety of process conditions at 11 wastewater treatment plants (WWTPs) in North America, ranging from 10 million gallons-per-day (mgd) to 350 mgd in wastewater treatment capacity.The WERF Project Team developed detailed testing protocols for the Phase 2 field study and completed its first trial of the testing protocol by conducting a full-scale sampling and analytical event at one of its largest testing sites in March 2002. The results of the full-scale testing event were used to review, refine and enhance the final testing protocols, which were presented to a workshop of participating agencies in late April 2002. The official sampling and analytical work at participating test sites was performed over the summer (May 22nd through August 23rd 2002), when biosolids odor problems are generally heightened due to the hotter temperatures.The WERF Project team gathered pertinent data from the treatment facilities and performed extensive odor analyses (both chemical and olfactory-based), then looked for trends and correlations between process conditions and odor-causing constituents. When fully analyzed and evaluated, the results are expected to provide a better understanding of the conditions that produce more odorous biosolids after anaerobic digestion. This understanding can be used to help our industry better manage the quality of biosolids and lessen its impact on surrounding communities.