A novel process using enhanced acidification and a UASB reactor for biomethanation of vegetable market waste

The processing of solid vegetable market waste was attempted in a two-stage digester. Initially, for the hydrolysis and acidification of waste, enhanced extraction process was carried out by continuous sprinkling of water over the bed of waste in a mild steel 100 1 solid bed digester. The leachate obtained after completion of acidification phase was further treated in 24.6 1 UASB reactor for biogas production. The effect of waste-liquid ratio, dilution and sprinkling rate on the digestion of waste were studied. A high strength leachate, with a COD of 25,298 mg l(-1) and total volatile fatty acids concentration of 11.3 g l(-1), was obtained as a result of hydrolysis and acidification in a very short retention time of 40 h. The COD reduction of 94% was achieved during UASB reactor operation at organic loading rate of 19.6 kg COD m day(-3). A minimum hydraulic retention time of 16 h was achieved.