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A Comparison of Measures to Assess Sludge Stability after Anaerobic Digestion
The vector attractiveness (frequently associated with odors and unsightliness) of sludge is an important parameter in protecting public health and the public's acceptance of biosolids land application. Odor is a common complaint. Currently accepted methods for assessing vector attractiveness of anaerobically digested sludge are either highly variable, depending on the influent sludge characteristics, or require an exorbitant amount of time to complete. Therefore, a need exists to establish a more efficient and reliable method to assess the vector attractiveness of sludges treated by anaerobic digestion
The project, which is currently underway, takes advantage of a local wastewater treatment plant (WWTP) with a staged approach to anaerobic digestion (four anaerobic digesters in series). Samples of untreated (raw primary and waste activated) and digested sludges after digesters #1, 2, and 4 allow for the assessment of several different stages of vector attractiveness of the same sludge source. The most prevalent method for assessing vector attractiveness of anaerobically digested sludge (percent removal of volatile solids) is being tested against seven nonstandard methods: biochemical oxygen demand, peak oxygen uptake rate, total heterotroph and fecal coliform densities, fatty acid methyl ester profiles, and two redox dye assays (INT and CTC), which gauge metabolic activity. All sampling is being performed by EPA personnel, and laboratory analyses are performed in-house. Data collection is currently approaching the halfway mark. The findings of this project will be made public after statistical analysis of the data, by the end of 2007.
Contact: Bethany Acquisto (EIMS#117991)