Rotary Drum Composting of Mixed Organic Waste based on Different C/N Ratios

Effects of the carbon to nitrogen (C/N ratio) on the composting of organic waste were examined by measuring changes in temperature, pH, EC, moisture content, TOC, total nitrogen, total phosphorus, VFAs, coliforms, BOD, COD. Time courses of the above values differed substantially between two experimental runs of different C/N ratio: 22 (Run A) and 30 (Run B). It was observed that time courses for getting matured compost were quite different in both cases. Run B containing larger amount of food and vegetable waste showed a slower rise in temperature, lower maximum temperature and shorter thermophilic phase than Run A. On the other hand, it also resulted in higher increase in pH, higher content of moisture, ammonical nitrogen and total organic carbon throughout the composting period. Since, the evolution of ammonical nitrogen is associated with the degradation of proteins. Run A showed 0.82 g/kg increase of total phosphorus compare to 0.57 g/kg in Run B. Biological parameters including COD (454 mg/l), BOD (107 mg/l), fecal coliform (5 × 102 bacteria/g), fecal streptococci (5 ×103 bacteria/g) observed in Run A while COD (538 mg/l), BOD (342 mg/l), fecal coliform (9.3 × 106 bacteria/g), fecal streptococci (4.3 × 105 bacteria/g) observed in Run B, indicated that Run A achieved maturity after 20 days of composting. Run B showed a relatively higher BOD/COD ratio and coliforms, indicating its immature nature with more than 4 % of total nitrogen due to larger amount of food and vegetable waste. Therefore, to obtain the matured compost in a rotary drum at an initial C/N of 22 required 20 days compare to an initial C/N of 30