A novel method for sewage sludge composting using bamboo charcoal as a separating material.

Traditional composting processes must be conducted with a bulking agent to ensure adequate air space for aeration. The bulking agent and composting materials are always completely mixed. A novel layered structure was introduced in sewage sludge composting, in which no bulking agent was used and bamboo charcoal was used as a separating material. Three lab-scale composting reactors (A: sawdust and sludge; B: bamboo charcoal and sludge; and C: sawdust, bamboo charcoal, and sludge) were continuously operated for 29 days. Several physicochemical parameters were investigated to evaluate the feasibility of layered composting with bamboo charcoal. The results indicated that the maximum temperatures during the thermophilic stage in treatments A, B, and C were 51.4, 50.9, and 51 °C, respectively. Layered composting with bamboo charcoal decreased the pH of the thermophilic stage from 8.98 in A to 8.75 in C, and delayed the peaks by about 120 h. The degradation rates of dissolve organic carbon (DOC) and dissolved nitrogen (DN) were 75 and 71.5% in treatment B, respectively, which were significantly higher than those of control group A (60 and 59.1%, respectively). The total NH3 emissions of treatment C (2127.8 mg) were significantly lower than those of A (2522.8 mg). Our results suggested that layered composting using bamboo charcoal as a separating material could be an alternative strategy to the traditional composting method. Moreover, layered composting combined with sawdust could effectively reduce NH3 emissions and N loss.