Volatile sulfide compounds (VSCs) and ammonia emission characteristics and odor contribution in the process of municipal sludge composting

Abstract

Malodor is becoming the main secondary pollution in the municipal sewage sludge-composting process. Ammonia and volatile sulfide compounds (VSCs) are the representative odorants that generated and emitted during the composting process. The emission characteristics of ammonia and VSCs were studied at different workshops in a full-scale municipal sludge-composting plant in North People's Republic of China. Results show that ammonia was the most dominant odorant of all the workshops and relative high concentrations of VSCs were detected at sludge stacking yard and composting workshop. The odor pattern of VSCs at the composting workshop and stacking yard were different. The odor pollution occurred mainly in the first 15 days of the composting process, in which the odor contribution of ammonia increased with time and the VSCs contributed largely in the first 5 days. The cumulative release concentration of VSCs from compost materials was in the order of DMDS (dimethyl disulfide) > DMS (dimethyl sulfide) > CS2 > MT (methyl mercaptan), and the total VSCs release concentration was in the range of 50-3200 μg•m −3 . The production of ammonia correlated to the temperature and nitrogen content and state changes, however, the production of VSCs was more complicated due to the reaction and transformation of VSCs. Optimization of aerobic composting conditions and process parameters should be further studied to reduce the emission of odor gas from compost.Implications: Along with the widespread use of sludge aerobic composting in People's Republic of China, the malodor pollution during the composting treatment is becoming a serious environmental issue. The odor pollution occurred mainly in the first 15 days, and ammonia was the main odorant of all the workshops and need to be controlled. Relative high concentrations of VSCs were detected at sludge stacking yard and composting workshop, however, the odor impact of VSCs were different. The generation of VSCs is more complicated than ammonia due to the reaction and transformation of VSCs.

Reducing odor emissions from feces aerobic composting: additives

“…An alkaline environment can keep H 2 S mostly in the ionic forms, and can also absorb the generated H 2 S. 61 Lowering the pH of the compost will reduce NH 3 production, but will increase the VSCs emissions. 62,63 Gu et al also obtained similar results. After reducing the pH of compost, the cumulative NH 3 emissions and TN losses reduce by 47.80% and 44.23%, but the emissions of VSCs and TS losses increase.…”

“…44 In actual operation, due to the blowoff effect caused by aeration, it may cause an increase in the gas emissions from compost. 18,62 Some studies have conrmed this view that an increased aeration rate is responsible for an increase in the NH 3 emission. 56,57 In other words, increasing the aeration will increase the NH 3 emissions.…”

Residuals, sludge, and biosolids: Advancements in the field

“…The study found dimethyl disulfide (174.59 μg/kg) and dimethyl sulfide (71.64 μg/kg) emissions were lower than ammonia (6062.5 μg/kg), but had similar odor intensity (Han et al, 2019). Zhao, Yang, Zhang, Chang, and Wang (2019)found similar results, though clarified the timing of these emissions with the volatile sulfur compounds highest in the first five days and ammonia increasing with time.…”

Pretreatment and composting technology of agricultural organic waste for sustainable agricultural development

“…Liang et al confirmed that significant ammonia volatilization occurs at high pH by simulating the mechanism of NH 3 volatilization under composting conditions [ 162 ]. Zhao et al, on the other hand, found that lowering the pH of the compost would reduce NH 3 emissions [ 163 ]. Similar results were obtained by Gu et al Lowering the pH of the compost reduced the cumulative NH 3 emissions and TN losses by 47.80% and 44.23%, respectively [ 164 ].…”