Optimization of Biogas Utilization at the Durham Advanced Wastewater Treatment Facility, Clean Water Services, Tigard, OR

Clean Water Services recently constructed a new brown grease receiving facility to accept brown grease collected in their service district to augment digestion of municipal solids at the Durham Advanced Wastewater Treatment Facility. Also constructed was a new cogeneration facility to utilize the increased biogas production. Clean Water Service seeks to optimize payback on the investment in these new facilities and therefore wants to achieve maximum value on operation of the new cogeneration engines and existing boilers on biogas, and natural gas as required, to meet the plant’s process and space heating demands.To achieve maximum value, Clean Water Services needed a tool to allow operations staff to make informed decisions on how best to operate the cogeneration engines and hot water boiler, taking into account seasonal changes in plant solids loadings, biogas production rates, and plant process and space heating demands. A model was developed to estimate the daily operating cost (or credit) of different configurations (combinations) of operating the cogeneration engines and hot water boilers. The model user adjusts parameters such as biogas production and other seasonal changes. The model produces a graph of the operating cost (or credit) of the available operating configurations against a range of ambient temperatures. The user can then select the operating configuration that provides the highest estimated operating credit.