Enhancing the start-up of a UASB reactor treating domestic wastewater by adding a water extract of Moringa oleifera seeds

Water extract of Moringa oleifera seeds (WEMOS) was used to enhance the sta rt-up of a self-inoculated upflow anaerobic sludge blanket (UASB) reactor t reating raw domestic wastewater. Two reactors labelled control (RC) and WEM OS addition (RM) were started without special inoculum. Both reactors were fed continuously for 22 weeks with domestic wastewater containing an averag e total chemical oxygen demand (COD) of 320 mg O-2/l and suspended solid (S S) of 165 mg/l. The reactors operated during the entire experimental period at 29 degreesC and at a hydraulic retention time (HRT) of 4 h. The RM reac tor received 2 mi WEMOS per litre of influent. WEMOS solution was prepared on the basis of 2.5% (w/v) ground M. oleifera seeds in water. The results o f 22 weeks' operation showed an improvement in the performance of the RM co mpared to that of the RC. The dosage of WEMOS in the feed (1) shortened the biological start-up period by 20%, (2) increased acidogenic and methanogen ic activity by a factor 2.4 and 2.2 respectively, (3) increased the specifi c biogas production by a factor of 1.6, (4) favoured fast growth of the slu dge bed, and (5) allowed the aggregation of coccoid bacteria and growth of microbial nuclei, which are precursors of anaerobic granulation.