Use of Field Olfactometry for Quantification of WWTP Dewatering Facility Odor Emissions

Abstract

An improved methodology for quantifying odor dilution-to-threshold (D/T) levels from environmental emission sources using field olfactometry has been developed, using multiple assessors. The method, pioneered at the Penn State Odor Assessment Laboratory for evaluation of manure odor emissions, is appropriate for high value decision making where documentation of existing malodor D/T levels and alternative mitigation measures are considered. This study describes application of the technique at the Philadelphia Biosolids Recycling Center (BRC) to benchmark odor emissions under current operating conditions, and identify perimeter locations especially vulnerable for off-site odor complaints. Nasal Ranger ® field olfactometer (FO) instruments were used to collect D/T observations at 13 inside-the-fence locations during four odor survey events in late July 2008. Quantitative FO measurements were complimented with odor quality observations: character, supra-threshold intensity, and hedonic tone. Subjective odor intensity and hedonic tone very highly correlated (r=0.99) with log 10 Best Estimate Threshold odor concentrations. The primary malodor source was determined to be the biosolids stockpile storage area. Less significant malodor sources included: the transport truck conveyorloading area, debris/ puddles along fence lines, and storm water collection/ detention facilities. Improved housekeeping and relocation of dewatered biosolids storage facilities were suggested to reduce the potential for off-site nuisance odor complaints.