Food waste decomposition in leachbed reactor: Role of neutralizing solutions on the leachate quality

The neutralization effects of 0.1 M NaHCO3, KPO4-buffer (pH 7.0) and sodium acetate (NaOAc) solutions (500 ml/kg food waste/day) on controlling the pH and leachate quality in an acidogenic reactor of food waste anaerobic digestion was investigated. pH of leachate from the reactor was low and ranged from 3.24 to 4.15. Although differences in chemical oxygen demand (COD) were observed, the cumulative COD yields were almost similar. Ammonia concentrations gradually decreased from 26 to 3 mg/l after 15 days. Acetic acid was the major fraction and the total VFAs decreased gradually for a week and increased thereafter, with a sharp increase in NaOAc treatment. VFAs yield and acetate/propionate ratio were the highest in NaOAc treatment, followed by NaHCO3 and KPO4 treatments. Volatile solids reduction was the lowest in NaOAc treatment (47.5%) and highest in NaHCO3 treatment (67.0%). With lower decomposition and higher yield of VFA and COD, NaOAc could be used as a neutralizing agent in acidogenic reactors to improve the efficiency of the acidogenesis process.