With growing water scarcity as a leading challenge for sustainable development, decentralized wastewater treatment and recycling strategies are emerging as viable solutions to address the water needs of a significant portion of the population. Unlike centralized wastewater treatment facilities, decentralized systems, especially those incorporating the source separation of wastewater, offer cost-effective and efficient ways to treat wastewater.This study first conducted a comprehensive life cycle impact assessment and techno-economic analysis to compare five treatment scenarios for two types of source-separated wastewater: blackwater (from toilets and kitchens) and greywater (from showers and laundry). These scenarios utilized different combinations of three scalable technologies: activated sludge, anaerobic digestion (AD), and membrane filtration. Activated sludge was employed to treat source-separated wastewater, while anaerobic digestion processes sludge into biogas for energy generation. Membrane filtration, including ultrafiltration and reverse osmosis, further purified the treated wastewater for discharge or recycling. The study revealed that using activated sludge and membrane filtration to treat blackwater and greywater separately, followed by anaerobic digestion to reduce the sludge and generate methane energy, offered superior environmental and techno-economic performance among the evaluated scenarios. The study highlighted the importance of biological treatments in removing pharmaceutical and personal care products (PPCPs) from wastewater, thus reducing their environmental impact. A baffled bioreactor (BBR) was utilized for blackwater treatment, showing high removal rates of organic content and inorganic nitrogen, which increased with higher feed amounts. The microbial diversity within the BBR system was also greater at higher feed amounts, facilitating the removal of total solids, total nitrogen, and nitrates. An economic analysis examined the treatment costs under different energy scenarios, including electricity from the grid, propane gas engines for remote communities, and diesel engines for military and extreme environments. Greywater, which can be separated from blackwater due to its lower contaminant concentration, is an excellent candidate for recycling. To optimize greywater treatment, the study evaluated three ultrafiltration membranes: Pittsburgh Plate Glass (PPG), Polyvinylidene Fluoride (PVDF), and Polyethersulfone (PES), using greywater from showers, laundry, and a combination of both as feed water. The PPG membrane demonstrated the fastest flux and least fouling across all water types, while PVDF and PES were more efficient at nutrient removal. The study concluded that a multiple objective optimization (MOO) approach is effective for selecting membranes and designing treatment processes tailored to different greywater sources. Addressing the inherent trade-offs in wastewater treatment of balancing water quality, energy consumption, and cost, the study employed a MOO approach to optimize treatment combinations. The system studied included electrocoagulation (EC) for blackwater treatment, AD for food waste and EC sludge, electrodialysis (ED) for final water treatment, and electricity generation from biogas and photovoltaic (PV) solar energy. The combination of PV, AD, EC, and ED achieved the best performance in terms of water quality, meeting EPA discharge standards, and demonstrated a low global warming potential (GWP) and high energy output. The Pareto frontier analysis highlighted AD+EC+ED and PV+AD+EC+ED as the preferred treatment combinations, prioritizing water quality and overall environmental performance. This integrated approach to decentralized wastewater treatment and recycling not only addresses water scarcity but also offers sustainable and economically viable solutions for various applications, from domestic to industrial and agricultural settings.
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