Characteristics of municipal solid waste and sewage sludge co-composting.

The purpose of this work is to study the characteristics of the co-composting of municipal solid waste (MSW) and sewage sludge (SS). Four main influencing factors (aeration pattern, proportion of MSW and SS, aeration rate and mature compost (MC) recycling) were systematically investigated through changes of temperature, oxygen consumption rate, organic matters, moisture content, carbon, nitrogen, carbon-to-nitrogen ratio, nitrogen loss, sulphur and hydrogen. We found that a continuous aeration pattern during composting was superior to an intermittent aeration pattern, since the latter delayed the composting process. A 3:1 (v:v) mixture of MSW and SS was most beneficial to composting. It maintained the highest temperature for the longest duration and achieved the fastest organic matter degradation and highest N content in the final composting product. A 0.5L/minkgVS aeration rate best ensured rapid initiation and maintained moderate moisture content for microorganisms. After the mature MC was recycled to the fresh materials as a bulking agent, the structure and moisture of the initial materials were improved. A higher proportion of MC resulted in quicker decrease of the temperature, oxygen consumption rate and moisture. Therefore a 3:1:1 (v:v:v) proportion of MSW: SS: MC is recommended.