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

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 (BET10) odor concentrations found no statistical difference between the 3-d and 10-d treatments, but 50-d BET10 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.