Decentralized wastewater treatment is a potential solution to the economic and sustainability issues associated with current wastewater infrastructure requirements for rural and expanding urban settings. However, wastewater produced from small-scale operations (domestic, industrial, agricultural, defense, etc.) are often found to have higher pollution concentrations than municipal wastewater and is referred to as "blackwater" in the study. A baffled bioreactor (BBR) was employed to carry out blackwater treatment. The results of this study showed the removal of organic content and inorganic nitrogen was high in all of the feed amounts tested and increased corresponding to an increase in feed amount. Microbial diversity results supported that the feed amount was the most important factor in treatment performance. The microbial community was more diverse at higher feed amounts than lower feed amounts. A non-metric multidimensional scaling (NMDS) analysis revealed that higher feed amounts enriched Verrucomicrobiaceae, unclassified Sphingomonadales, unclassified Burkholderiales in the microbial community, and facilitated the removal of total solids, total nitrogen, and NO3-. The energy and exergy analyses showed the consumption of 5.02 Wh/L wastewater energy with a universal exergy efficiency of 61% at the feed amount of 3750 LPD. An economic analysis further delineated the treatment cost profiles of the decentralized unit under four different energy case scenarios of electricity from the grid, propane gas engine for remote rural communities, diesel engine (I) using standard U.S. market diesel fuel costs for remote rural communities and scientific research bases, and diesel engine (II) using the fully burdened cost of diesel fuel for military contingency bases and other extreme environmental scenarios.
Keywords: Baffled bioreactor; Blackwater; Economic analysis; Exergy; Mass and energy balance; Microbial community analysis; Small scale.
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