Abstract
Wastewater treatment plant (WWTP) utilization of combined heat and power (CHP) systems allows for the efficient use of on-site biogas production, as well as increased annual savings in utility costs. In this paper, a review of biogas energy recovery options, CHP prime mover technologies, and the costs associated with biogas cleaning give a broad summary of the current state of CHP technology in WWTPs. Even though there are six different prime mover technologies, the main ones currently being implemented in WWTPs are micro turbines, fuel cells and reciprocating engines. Different prime movers offer varying efficiencies, installation costs, and biogas impurity (H2S, siloxanes, HCl) tolerances. To evaluate the long-term savings capabilities, a techno-economic assessment of a CHP installation at a case study WWTP shows the payback, annual savings, and initial costs associated with the installation of a CHP system. In this case, a study a payback of 5.7 years and a net present value of USD 709,000 can be achieved when the WWTP generates over 2,000,000 m3 of biogas per year and utilizes over 36,000 GJ of natural gas per year.
Highlights
Water and energy are inseparably connected and vital resources, as electricity generation requires large quantities of water while a significant amount of energy is required for both drinking water and wastewater services
Water operations typically consume a disproportionately large amount of energy in a community, which means significant environmental, economic and social benefits can result from more efficient operations in water treatment plants (WTPs) and wastewater treatment plants (WWTPs) [2]
This paper aims to assess the current state of the art in biogas-fueled cogeneration energy recovery to enhance understanding and uncover opportunities for implementing projects
Summary
Water and energy are inseparably connected and vital resources, as electricity generation requires large quantities of water while a significant amount of energy is required for both drinking water and wastewater services. This has been termed the water–energy nexus [1]. In the United States, municipal WTP and WWTPs collectively demand around 2–4% of the U.S. energy consumption, which represents around USD 4.7 billion annually [3,4]. Of the total energy needed for WWTPs utilizing conventional activated sludge process, about half is electrical energy for the aeration basins [5]. While only a portion of that energy can be recovered, it is possible and feasible for WWTPs to be net energy producers [7,8]
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