Wastewater treatment as an energy production plant.

摘要

The objective of this research was to investigate the potential for net energy production at a Wastewater Treatment Plant (WWTP). Historically, wastewater treatment plants have been designed with the emphasis on process reliability and redundancy; efficient utilization of energy has not received equal consideration. With growing demands for energy and increased budgetary pressures in funding wastewater treatment plant costs, methods of reducing energy consumption and operating costs were explored in a new and novel direction pointed towards energy production rather than energy consumption.; To estimate the potential for net energy production, a quantitative analysis was performed using a mathematical model which integrates the various unit operations to evaluate the overall plant energy balance. Secondary treatment performance analysis is included to ensure that the energy evaluation is consistent with plant treatment needs. Secondary treatment performance was conducted for activated sludge, trickling filters and RBCs. The equations for the mathematical model were developed independently for each unit operation by writing mass balance equations around the process units. The process units evaluated included those for preliminary treatment, primary treatment, secondary treatment, disinfection, and sludge treatment.; Based on an analysis of both energy reduction and energy recovery methods, it was shown that net energy production at a secondary WWTP is possible utilizing technologies available today. Such technologies include those utilized for plant operations, as well as for energy recovery. The operation of fuel cells using digester gas represents one of the most significant new opportunities for energy recovery at wastewater facilities.; The analysis predicts that a trickling filter WWTP utilizing commercial phosphoric acid fuel cells to recover energy from digester gas can provide for facility energy needs and have both electrical and thermal energy available for export. The use of fuel cells at an activated sludge or RBC WWTP is projected to produce all of the plant's thermal energy requirements and a significant amount of the electrical energy needs. With continued fuel cell development, it is expected that the 21st century will see all types of wastewater treatments plants producing significant energy for export in addition to its primary function of wastewater treatment.