Emission potential of volatile sulfur compounds (VSCs) and ammonia from sludge compost with different bio-stability under various oxygen levels

Abstract

Volatile sulfur compounds (VSCs) and ammonia from biowaste-derived residues is influenced by both the degree of bio-stability and atmosphere of oxygen level (i.e., either anaerobic, aerobic or anoxic conditions). By means of odor emission potential (OEP) test, present study directly examined how these two factors jointly affected the emissions of different odorous compounds from sludge compost. Results reveal that (1) the cumulative amount of ammonia and VSCs ranged from 0.08 to 0.38 mg/g-DM and 1.92 to 6.42 μg-S/g-DM, respectively. (2) High degree of bio-stability and oxygen level decreased the emission rates and cumulative amounts of ammonia, carbonyl sulfide, carbon disulfide, and especially methlymercaptan, who was even extinguished in the late stage. (3) Dimethyl sulfide and dimethyl disulfide showed no decline trend with increasing of bio-stability degree and oxygen level, suggesting their formation was mainly abiotic; cumulative amount of dimethyl disulfide was even higher under an atmosphere of high oxygen level. (4) Methlymercaptan was the dominant contributor to odor nuisance. The olfactory threshold of ammonia, dimethyl sulfide and dimethyl disulfide also exceeded their limited value. Hence, these odor compounds are priority when came to odor management of sludge compost. Overall, high stability degree and oxygen level alleviated the emission of ammonia, carbonyl sulfide, carbon disulfide and methlymercaptan, while the abatement of dimethyl sulfide and dimethyl disulfide should lie in controlling oxygen level in a certain range rather than extremely high oxygen level. Methlymercaptan can be regarded as an alternative indicator of the degree of bio-stability.