Effects of anaerobic digester solids retention time on odor emission and dewaterability of biosolids subjected to various shear intensities, polymer doses, and storage duration times

Abstract

Odor emitted during biosolids handling is a major issue for utilities and may pose a serious nuisance to surrounding communities. The purpose of this study is to assess the effects of solids retention times (SRTs) of mesophilic anaerobic digesters on the odor emission from biosolids dewatered under various shear intensities and polymer doses. It was found that the digester SRT varying from 15 to 50 days had a very limited effect on the odor precursor reduction in biosolids. Hence, no significant variance in odor emission was observed when SRT was evaluated alone. In contrast, the polymer dose and shear intensity used for dewatering showed more effects than SRT on odor emission and biosolids dewaterability. In general, biosolids dewatered at higher shear intensity tended to consume more polymers to achieve the desired cake dryness, and the peak odor emission was found to increase with both the shear intensity and the polymer dose likely due to the increased protein capture and exposure by the polymer and shear used for dewatering.