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As more and more water resource recovery facilities (WRRFs) design and operate new biogas utilization systems it becomes crucial to share the best operating practices for the cogeneration and gas treatment systems. The intent of implementing best operating practices is to (1) maximize the electrical and natural gas energy cost savings via increased engine output per unit of gas and engine uptime, (2) minimize operations and maintenance expenses that erode net energy cost savings, and (3) reduce biogas flaring.The objectives of this study are to:• Identify key maintenance activities that maximize engine availability and electrical production • Suggest operating strategies to maximize electrical savings • Share plant operator's perspective on key aspects of system design to help provide more operator-friendly designs • Consider staffing and training practices that contribute to operating success

Growing concern over the cost of power and long-term availability of limited fossil fuel resources for the production of electricity have caused electrical utilities and governments to promote "green" or renewable power. Solar, wind, geothermal, biomass, biogas, and low-impact hydroelectricity are current acceptable green-power sources.Digester gas is a renewable, green energy resource that has been used in wastewater treatment plant (WWTP) engines since the 1930s. In the 1980s, many WWTPs added cogeneration with rich-burn engines. In the 1980s and 1990s, utilities either converted their rich-burn engines to lean-burn engines or installed new lean-burn engines to meet air quality requirements.Because digester gas is of finite supply and is dependent on operating parameters such as sludge feed and volatile solids destruction, it is desirable for WWTPs to maximize the efficiency of electricity generation and beneficial reuse of otherwise wasted heat. Recently, a number of projects have used innovative cogeneration technologies, such as fuel cells, gas turbines, microturbines, and Stirling Cycle engines, to harness the energy of digester gas. In addition, advanced reciprocating engine systems (ARES) are currently being developed as another cogeneration technology under an initiative sponsored by the United States Department of Energy (USDOE) and U.S. National Laboratories with three reciprocating engine manufacturers.Columbus Water Works (CWW) is currently evaluating the use of ARES engines for combined heat and power (CHP) generation for its Class A biosolids process named Columbus Biosolids Flow-Through Thermophilic Treatment (CBFT 3 ) at the South Columbus Water Reclamation Facility (SCWRF) that currently treats an average flow between 30 and 35 million gallons per day (mgd). The use of ARES engines as part of the CBFT 3 project would represent one of the lowest capital cost, highest net efficiency CHP technologies. The project is expected to provide a payback between 4 to 7 years, with an even shorter payback period depending on the degree of federal funding secured and avoided capital offsets assumed.Other innovative features of the project include the addition of grease trap waste to the digestion process to increase gas and power production, digester gas pretreatment using multiple unit processes, and heat recovery systems. 3570 WEFTEC®.06

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