Use of Inventory Management to Mitigate Odor Emissions From Land-Applied Biosolids

Abstract

Short-term (<60-d) stockpile-curing of dewatered municipal wastewater biosolids has been suggested as a practice to reduce malodors during subsequent field application. Biosolids from the City of Philadelphia were evaluated following stockpile-curing for 3-d, 10-d, and 50-d. Each material was top-dressed on small grain stubble in 37-m diameter rings. Four trained odor assessors were positioned in the center of each odor ring and olfactory observations were performed at: pre-application (background); 45-60 min, 4-hrs, 10-hrs, and 20-hrs following field application. Comparison of 10-minute Best Estimate Dilution Threshold (BET 10 ) odor concentrations found no statistical difference between the 3-d and 10-d treatments, but 50-d BET 10 levels were statistically greater (α=0.05). Odor character, intensity, and hedonic-tone observations were similar and triangular forced-choice dynamic olfactometer testing of flux chamber whole-air samples revealed no statistical differences. Sensory odor quantification techniques employed to assess the total effect of field malodors showed remarkably consistent results. Analytical analyses were unsuccessful in identifying a single odorant in whole-air field samples. This study was not able to confirm that short-term biosolids stockpile curing produces a less odorous product for field application.

Biosolids and Sludge Management

“…They developed a model that found the food to microorganism ratio, sludge blanket depth, and sludge settled volume (60 min) were the dominant processes that impacted the formation of the VSC. Also using inventory management, Brandt et al (2009) used short-term (<60 days) stockpile curing as a process to reduce odors emitted from biosolids intended for field application. With the use of 10 minute Best Estimate Dilution Threshold (BET 10 ), there was not a statistically significant difference between the 3 and 10 day treatments, but the 50 day BET 10 odor level was significantly higher.…”