Inhibitory Effects of Appropriate Addition of Zero-Valent Iron on NH 3 and H 2 S Emissions during Sewage Sludge Composting

Large amounts of NH 3 and H 2 S are emitted during sewage sludge composting, resulting in odor pollution. This composting experiment was carried out using sewage sludge mixed with sawdust, and different amounts of zero-valent iron (ZVI) were added to investigate the effect on volatile gases, such as NH 3 and H 2 S, and to analyze the effect on the available sulfur, total sulfur, moisture content, and germination index of the compost. The results showed that the addition of ZVI during the composting process had noticeable effects on the emission of NH 3 and H 2 S. ZVI could also increase the heating rate and peak temperature of the pile, reduce the available sulfur loss, and promote the dewatering and decomposition of the compost pile. The addition of 3% ZVI had the best effect on NH 3 emissions; it reduced the peak concentration of NH 3 release during composting by 21.0% compared to the blank group. However, the addition of 2% ZVI was the most effective for H 2 S emissions; it reduced the peak release concentration of H 2 S by 20.0%. A higher addition of ZVI was more effective in reducing the moisture content and increasing the germination index of the compost.