Optimization Of Anaerobic Co-digestion Of Sewege Sludge And Brewery Yeast Waste

A batch anaerobic digestion experiment was carried out to determine the optimum methanernproduced from digestion of sewage sludge and brewery yeast waste in different mix, and thernfertilizer potential of the sludge after digestion.rnThe maximum methane production from anaerobic digestion of sewage sludge and brewery yeastrnwaste was assessed in batch tests using armfield glass made anaerobic digester in chemicalrnengineering laboratory. The volume of biogas produced and methane composition of differentrnmix of the feed stock were determined by water displacement and geotechnical land fill gasrnanalyzer model GA 45, respectively. It was observed that the independent variable – mix ratiornsignificantly affect (p-value 0.0027) the dependent variable – amount of methane produced sincernthe p-value is less than the chosen α-level usually 0.05. The calculated volume of methane in thernbiogas produced per gram COD removed were 0.218L, 0.103L, and 0.075L and per gram volatilernsolid removed were 0.271L, 0.172L and 0.136L for sewage sludge alone, 80:20% mix, andrn60:40% mix of sewage sludge to brewery yeast waste respectively. In general From the digestionrnof sewage sludge alone: 0.44 m3/d/m3 biogas with 57.75% methane was produced; 0.74 m3/d/m3,rnand 0.91 m3/d/m3 biogas with 19.84% and 19.34% methane produced from 80:20% mix andrn60:40% mix of sewage sludge to brewery yeast waste, respectively. The mix ratio significantlyrnaffects the biogas production (p-value 1.65*10-9). Totally 83,850 m3 CH4/year can be capturedrnand hence same amount of methane emission into the atmosphere is prevented from the sewagernsludge currently managed in Addis Ababa waste water treatment plant if anaerobic digester isrnused.rnWith regard to the fertilizer potential of the digestate; heavy metal content is not a limiting factorrnin the use of sewage sludge managed in Addis Ababa waste water treatment as a soil conditionerrnand fertilizer. Moreover, the nitrogen, phosphorus and potassium content of the sludge satisfyrnspecific plant uptake requirements in many land application systems. Sun drying on drying bedsrnafter anaerobically digested sludge is helpful in the viability of land application of treated sludgernby completely inactivating the pathogen and reducing the potential risk.rnKey words: Biogas, Methane, Organic fertilizer, Anaerobic digestion, Digester, Sewage sludge,rnBrewery yeast waste

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