Wood Ash Control of Odor from Biosolids Application

Abstract

AbstractOdor emissions from land application of biosolids have become a concern for biosolids managers. Chemical odorant emissions from biosolids were identified using gas chromatography‐mass spectrometry and included dimethyl disulfide (DMDS), dimethyl sulfide (DMS), carbon disulfide (CS2), ammonia (NH3), trimethyl amine (TMA), and acetone. Odor unit measurements (odor intensity as perceived by people) were then related to chemical odorant concentrations. Odor unit emissions were positively correlated with DMDS emissions. To control biosolids odor, wood ash containing 87, 32, 27, 5.4, and 0.24% carbon was incorporated with biosolids (1:1 dry weight ratio). The wood ash possessed surface areas of 520, 85, 74, 25, and 2.1 m2 g−1, respectively. Ash additions reduced odor unit and emissions of DMDS, DMS, and CS2 when compared with the biosolids control, depending upon ash C content and surface area. Although ash additions reduced emissions of acetone, TMA, and sometimes NH3, reduction was not consistently significant. Using the SCREEN3 dispersion model (USEPA, 1995a), maximum DMDS and NH3 concentrations at a 21 Mg ha−1 biosolids application (dry weight) were estimated to be 8.9 and 6.8 times above published human detection limits, respectively, while maximum CS2, DMS, acetone, and TMA concentrations were predicted to be 0.013, 0.017, 0.026, and 0.45 times below published human detection limits, respectively. Incorporation of high carbon wood ash with biosolids eliminated DMDS odor, while wood ash did not significantly reduce the NH3 odor.