Effect of a New Bulking Agent on Sewage Sludge Composting

To improve bulking agent (BA) reusability and reduce bulking agent costs, a new bulking agent was developed using straw and methylene diphenyl diisocyanate. The objective of this study was to investigate the effect of the new bulking agent on sewage sludge composting. The results showed that the new bulking agent has high recovery ratio when used in sewage sludge composting, and can improve the composting process. Decreasing the mass ratio of sewage sludge to bulking agent from 3:1 to 2.5:1 in compost pile improved the rate of temperature increase, increased the maximum temperature, shortened the thermophilic stage of the composting process, and achieved an even temperature distribution during the initial heating phase. The recovery ratios for the bulking agent with mass ratios of 3:1 and 2.5:1 were 94.7% and 92.2%, respectively. The recovery and reuse of this new bulking agent could significantly reduce the cost of bulking agents in the composting of sewage sludge, and the appropriate mass ratio of sewage sludge to bulking agent is 2.5:1.