PILOT-SCALE DISTILLERY SPENTWASH BIOMETHANATION

Mesophilic biomethanation of distillery spentwash has been investigated at a pilot scale with a diphasic anaerobic process. An operational strategy to suppress sulfide inhibition through pH control in the methane phase has also been validated. The acid phase has been operated on lime-neutralized spentwash at an organic loading rate of 30 kg COD/m3/day. Methane phase operation without solids recycling enabled 65% COD reduction and 0.3 m3 of biogas production with 60% methane per kilogram COD utilized at an organic loading rate of 3.25 kg COD/m3/day. The contact methane phase at 5 kg COD/m3/day and 27 day mean cell-residence time achieved 70% COD reduction and 0.3 m3 gas production with 70% methane per kilogram of COD utilized. An energy audit revealed over 13 times the energy production per unit energy consumed in the process. A mathematical model for the acid phase predicted volatile acid concentrations within 15% of experimental results. The methane phase model incorporated inhibition and was independent of growth or nongrowth associated phenomena. The model predicted effluent substrate concentrations and gas yields within 10% and 15% of experimental values in the methane phase, respectively.© ASCE.