Energy Balances for Proposed Complete Full-Scale Anaerobic Wastewater Treatment Facilities

Organics in domestic wastewater contain more chemical energy than is required for treatment; however, current wastewater treatment approaches are energy intensive. The chemical energy in wastewater can be converted to methane-rich biogas through anaerobic bioreactor technologies. While recent research has examined anaerobic bioreactor configurations for domestic wastewater treatment, such as anaerobic membrane bioreactors (AnMBRs) or anaerobic sludge blanket bioreactors, none have conducted energy balances on proposed full-scale anaerobic wastewater treatment facilities (WWTFs; i.e., those that include all processes, such as preliminary treatment, sludge pumping, odor control, etc.). Using Monte Carlo simulation, we address this gap in the literature by examining whole-facility net energy balances for three potential anaerobic wastewater treatment configurations composed of anaerobic sludge blanket bioreactors (e.g., the upflow anaerobic sludge blanket, UASB), AnMBRs, and partial nitritation/anammox (PN/A) to a conventional WWTF designed for biological nutrient removal. For comparison, all energy values were normalized to treatment of 37,850 m(3) of wastewater per day to U.S. EPA secondary effluent standards and nitrogen removal to 1 mg & BULL;N/L. Results suggest that a configuration based on anaerobic sludge blankets and PN/A can achieve a net energy positive condition, generating 670 & PLUSMN; 3,580 kWh/day. AnMBR-based configurations currently do not achieve an energy-neutral condition; however, reduction in AnMBR energy requirements will bring AnMBR configurations closer to this goal. Our results suggest that full-scale WWTFs that leverage anaerobic technologies can become energy neutral or net energy positive even when all WWTF energy requirements are examined.