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Renewable Energy Potential of Sewage in Zambia

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Document pages: 23 pages

Abstract: This study was aimed at investigating the renewable energy potential ofcom- munal and municipal wastewater through methane production in biogasdigesters and the use of the captured methane for energy production in biogas engines. It was conducted on biogas digestersreceiving and pre-treating communal and municipal wastewater in the Zambiancity of Livingstone. Wastewater inflow rates into biogas units including thewastewater turbidity, total dissolved solids (TDS), temperature, pH,conductivity and Chemical Oxygen Demand (COD) were measured during the study.And all the produced biogas was measured and combusted on-site during thecourse of the research. In order to know the methane content of the gas, the CO2 content in the biogas was measured with a CO2 indicator. The studyshowed that the predominant factor affecting the process of methane productionfrom wastewater to the greatest extent is the COD concentration of theinflowing wastewater and not the system hydraulic retention times (HRT’s). TheCOD treatment levels of the tested systems ranged between 27 and 86 percent andthe degree of breakdown primarily depended onthe COD concentration of the influent wastewater. On renewable energyfuel production, about 3.54 kilograms of COD in each system produced a kilogramof methane. Communal wastewater was able to produce an average of 600 grams ofmethane per cubic meter of wastewater treated whilst municipal wastewater withless COD concentration was only able to produce about 64.5 grams of methane percubic meter wastewater treated. With the use of a 45 kw Cummins 6 BT biogasengine, the respective wastewaters had potential to produce about 2.6 kWh and0.1 kWh of electric energy per cubic meter of wastewater treated at a levelizedcost of USD 9 cents per kilowatt-hour. Temperature also showed that it hassignificant effect on methane production as a degree temperature rise in theanaerobic system increased the methane production mass rate by 1.2 percent.

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