Total phosphorus removal from Sewage in microbial electrochemically assisted septic tanks

Background: Subsurface sewage treatment systems (SSTS), commonly known as septic systems, typically consist of a septic tank and an absorption field (or drainfield or leachfield), to treat sewage from households. The septic tank as pretreatment step decreases total suspended solids (TSS), biochemical/chemical oxygen demands (BOD/COD), and pathogen levels from sewage influent, while the drainfield or soil absorption field captures nutrients (nitrogen and phosphorus) from the tank effluent so that the water leaving SSTS would have minimal environmental impact. By modifying the conventional septic tank through incorporating electrode materials to make use of microbial electrochemical process, this study assessed this novel design in terms of sewage treatment performance. Since phosphorus becomes increasingly threatening to water environment, it was the goal of this novel design to remove it from liquid phase and potentially capture it at electrode surface. Methods: The experiments were conducted with 1-L scale simulated septic tanks at four different applied voltage levels (0.50 V, 0.63 V, 0.75 V, and 0.88 V, selection based on previous preliminary results) with control of without applied voltage. Tanks were set up and operated at two temperatures (15 and 25 °C), a hydraulic retention time of 8.3 days, two cycles of feeding and withdrawal during each HRT. The treatment conditions of the reactors are listed in REF-Ref450506281 \h Table 1 08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000E0000005F005200650066003400350030003500300036003200380031000000. ANOVA and pairwise multiple comparisons based on Bonferroni test were conducted for water characteristics with OriginPro Version 8 at significance level of α=0.05.