Performance Evaluation of In-vessel System for Co-composting of Septage

The present study deals with the evaluation of in-vessel co-composting as a treatment option for septage management. Optimization of process parameters such as carbon: nitrogen (C/N) ratio, moisture content, pH, temperature and oxygen supply can accelerate the naturally occurring composting process. Since the C/N ratio of septage is <10, it needs to be composted with complementary waste having higher C/N. Hence, in this study, efforts were made to understand the compost dynamics of septage co-composting in a laboratory-scale in-vessel system. Co-composting of septage was done with mixed organic fraction which includes mainly paper waste, vegetable waste and food waste to increase the overall C/N ratio. The parameters such as pH, moisture content, temperature, carbon and nitrogen were monitored during the process. The results showed that the compost mixture has an initial C/N ratio of 20 and organic matter (OM) content of 83%. The OM content was reduced to 62% and C/N ratio to 11 after a composting operation of 20 days, which indicated the effective degradation of organic waste. Temperature above 55 °C for more than 5 days ensured significant pathogen inactivation during the composting process. Final compost quality indicated that it can be used as a fertilizer since it has enough organic and nutrient content for plants to grow.