Chemical and physical property of rice straw waste and hospital sewage sludge in turned windrow aeration system

Abstract

Most sewage sludge from hospital wastewater treatment plants in Northern Thailand are also being to incinerator and agricultural fields. Land application of hospital sewage sludge has serious effects on environmental. The main goal of this investigation was to find the optimum quality ratio of co-composting with rice straw waste and hospital sewage sludge. The experiments were designed by varying the initial C/N ratio and moisture contents in the range of 25 to 45 and 30% to 70% by w/w., respectively. Composted materials from all treatments were sampled every week and their chemical properties analyzed. All experiments were setup using plastic bins in which air was continuously supplied and the room temperature was controlled at 30 °C. The results clearly showed that the pH and the volatile solid content of composted materials increased with increasing moisture content, whereas this tendency decreased with increasing composting period. The losses of Kjeldahl-N increased when the amounts of sludge in the mixtures increased. The highest C decomposition of 49% occurred in the system at a C/N ratio 35 and 60% of moisture content, with coincided with high-nitrogen content in this treatment. In addition, heavy metals and pathogens were lower concentrations than maximum allowable for final compost for USEPA standards. This demonstrates that co-composting produced from rice straw waste and hospital sewage sludge is feasible for use as soil amendments or fertilizers.