Production of Efficient Microbial Complex for Organic Fraction of Municipal Organic Solid Waste Pretreatment Upstream Anaerobic Digestion

Abstract

The aim of this present study is to select high performance microbial strains for organic municipal solid waste biological pretreatment. Waste samples were collected at three municipal waste pre-collection centers in the city of Ouagadougou. Standard isolation and characterization methods have been used for strains selection in different biotopes. Waste biodegradation tests were carried out in bottle (300 mL) with 120 mL of useful volume composed of the buffer (K 2 HPO 4 and NH Cl) and 2% of waste. Optimization tests of waste pretreatment were carried out in function of temperature and inoculum proportion (10 % and 25 %). The evolution of pH and total solid loss was monitored during fermentation. Sixteen (16) microbial strains were isolated from different matrices, including three (03) cellulolytic bacteria (CA1, CA2, CA3), three (03) Streptomyces sp (SS1, SS2, SS3), four (04) Bacillus sp (BS1, BS2, BDP, BAF), three (03) Yeasts (YBB, YDP, YEU) and three (03) molds (MS, MBB, MDP). The pH drops from 7 to 5.4 and persists until the 6 4 th day was followed by a gradual increase in pH to 9. Temperature rise at 37 °C allowed a sudden acidification from the 3 rd day (pH 5.6 at 30°C and pH 4.72 at 37°C) and increases to pH 10. The CA3-SS3-BDP-YBB consortium has been identified as the best combination for a pre-fermentation of municipal waste. The TS reduction on day 25 ranged from 9.9 g/L or 49.5% of TS removal for TNS, 6.7 g/L or 33.5 % for MDP, 9.3 g/L or 46.5% for SS3, 6.3 g/L or 31.5% for YDP, 8.7 g/L or 43.5% for CA3, 7 g/L or 35% for MBB and 4.8 g/L or 24% for YBB. The optimization allowed a reduction of the pretreatment time to 4 days, obtaining a biomass adapted to anaerobic digestion.