Advancing sustainable wastewater treatment: elucidating tradeoffs among emerging resource recovery technologies through quantitative sustainable design

Anthropogenic activities are negatively impacting the environment through biodiversity loss, altering nutrient cycles, and increases in severe weather events. These impacts are subsequently hindering the ability of wastewater treatment plants (WWTPs) to protect human and environmental health. In addition, the field of wastewater engineering is facing several problems that must be addressed in the coming decades, such as aging infrastructure and stricter effluent discharge requirements. Wastewater treatment is currently primarily based on the cultivation of aerobic heterotrophs and though it provides a high-quality effluent, it is also energy intensive. High energy demand is costly both economically and environmentally. These problems underlie a need to re-envision WWTPs as a resource capable of nutrient and energy recovery while continuing to hold human and environmental health paramount. In order to compare possible approaches to solving the problems facing wastewater treatment, a critical review was conducted comparing several anaerobic and phototrophic technologies to determine their potential for energy positive domestic wastewater treatment. Phototropic processes were shown to be able to produce 280-400% greater energy than anaerobic processes producing methane (on a per m3 basis). However, phototrophic processes increase chemical oxygen demand (COD), so a downstream process is also necessary. Anaerobic membrane bioreactors (AnMBRs) were found to have the highest consistent COD removal (80-90%) of the anaerobic processes, but also had high energy consumption. Though they are a new technology, AnMBRs show promise for full-scale domestic wastewater treatment, but because there are many different designs available, research on the topic varies greatly. An in-depth examination of AnMBR designs was conducted utilizing quantitative sustainable design to elucidate configurations that limit economic or environmental impacts under the assumption that all designs treat wastewater to the same effluent quality. The results show that certain design decisions have a profound impact on the total net present cost and life cycle environmental impacts. Therefore, recommendations for future research are made that traverse the relative benefits and detriments of different AnMBR configurations