Electricity from wastewater treatment plants

Abstract

Wastewater treatment plants that are located in high places can provide opportunities for generating sustainable energy, by installing hydroturbines at inlet and exit pipesof wastewater treatment plants, as well as exploiting the sludge resulting from the treatment process as a source for generating biogas, which can be used to generate electric power. Then the treated water is used to irrigate ornamental trees in the roads, gardens and forests, as well as the residues of the fermentation process are used as organic fertilizer and to improve the quality of agricultural soil. In this research, a hybrid system consisting of a hydroelectric station and an electric generator working on biogas was proposed at the wastewater treatment plant in Gharyan. This is because the city is distinguished by its high location, about 713 m above sea level. The obtained results showed that the proposed hybrid renewable energy system will provide the wastewater treatment plant an electric power of 490 kW, which is sufficient to cover 87.5% of the plant’s electrical energy consumption. 
The amount of treated water was about 13,000 m3/day, and the amount of organic fertilizer was about 17 tons/day. The investment value was estimated at about $1,478,000, and the leveized cost of energy LCOE was estimated at about 2.88 ¢/kWh. The annual net profit from the proposed system is estimated at $307,765/year, and the payback time money at 3.44 years. The proposed system will prevent the release of an annual amount of CO₂ gas estimated at 1,886 tons.