Biphasic biomethanation of hemicellulose rich effluent

Abstract

In the dissolving pulp industry, a hemiceJluJose rich effluent (wood-hydrolysate) is the major source of environmental pollution Generally, a pretreatrnent in anaerobic lagoon is given in this effluent which results in the release of methane in the atmosphere. This work deals with the systematic study of the biphasic biomclhanation of wood-hydrolysate effluent to develop a practicable technology for the treatment of this effluent and generation of bioenergy. Wood-hydrolysate was found to contain 81,800, 39,300, 1070, 3492, 23250 mg/1 COD, hemicelluloses, glucose, xylose and Mgnin respectively. Firstly, monophasic reactors viz. upflow anaerobic sludge blanket (UASB), and anaerobic filter (AF) reactors were used to treat this effluent. UASB reactor could attain a maximum organic loading rate of I 1.6 g COD/l/d in 3 I I days with feed concentration of 11,5 g COD/l and hydraulic retention time of 0.94 day. Methane content in the biogas was 64-67% and COD reduction was 76%. For a relatively longer period of study, the AF reactor could sustain an organic loading of 14.7 g COD/l/d with a feed concentration of 14.6 g COD/1 and HRT of 0.97 day; specific methane yield of 4.53 I/I reactor volume/d with 64-66% methane and 82.9% COD reduction was observed. Efficiency of these two monophasic reactors was taken for comparison to show in the ultimate analysis, the advantages of the biphasic system Microbial flora from municipal solid waste for both the stages, acidogenesis and melhanogenesis, were acclimatized with the appropriate substrate. Suitable nutrients and pH (4.5-5.5) environs have been provided to promote the growth of active acidogenic microbial flora in the upflow acidogenic reactor, the simplest one. Two separate experimental runs were conducted for 163 and 331 days to study the acidogenic reactions of wood-hydrolysate.