Enhancement of hydrolysis and acidification of solid organic wastenext term by a rotational drum fermentation system with methanogenic leachate recirculation
A cascade process of a rotational drum fermentation system with leachate recirculation from a methanogenic to the acidogenic reactorwas constructed to enhance the hydrolysis and acidification of solid organic waste. Using fresh soybean meal as substrates, two processconfigurations, Cascade process 1 and 2, without and with leachate recirculation, respectively were employed to perform the experimentalestimation under mesophilic condition and a total HRT of 20 days. An apparent first-order hydrolysis rate constant of 9.0 x 10-3/dfor Cascade process 1 at pH 4.5-4.6, and 15.8 x 10-3/d for Cascade process 2 at pH 4.6-5.2 were obtained. The apparent VS degradationratios ranged from 16.5% to 21.1% and total VA (as acetic acid) from 14.5 to 16.7 g/L. Occupying ratios for ionized VA decreased from40.5% to 35.3% for Cascade process 1 and increased to 68.5% for Cascade process 2. However, occupying ratios of acetic acid decreasedfrom 96.1% to 94.3% for Cascade process 1 and to 72.6% for Cascade process 2, whereas propionic acid and butyric acid ratios increasedin acidogenesis of Cascade process 2. The leachate recirculation promoted hydrolysis of substrate in Cascade process 2, where apparenthydrolysis rate constant and VS degradation ratio were higher than that of Cascade process 1
