Technical and environmental evaluation of an integrated scheme for the co-treatment of wastewater and domestic organic waste in small communities.

A technical and environmental evaluation of an innovative scheme for the co-treatment of domestic wastewater and domestic organic waste (DOW) was undertaken by coupling an upflow anaerobic sludge blanket (UASB), a sequencing batch reactor (SBR) and a fermentation reactor. Alternative treatment configurations were evaluated with different waste collection practices as well as various schemes for nitrogen and phosphorus removal. All treatment systems fulfilled the required quality of the treated effluent in terms of chemical oxygen demand (COD) and total suspended solids (TSS) concentrations. However, only the configurations performing the short-cut nitrification/denitrification with biological phosphorus removal met the specifications for water reuse. The environmental assessment included the analysis of impacts on climate change (CC), freshwater eutrophication (FE) and marine eutrophication (ME). A functional unit (FU) of 2000 people receiving treatment services was considered. The most relevant sources of environmental impacts were associated to the concentration of dissolved methane in the UASB effluent that is emitted to the atmosphere in the SBR process (accounting for 41% of impacts in CC), electricity consumption, mainly for aeration in the SBR (representing 14% of the impacts produced in CC), and the discharge of the treated effluent in receiving waters (contributing 98% and 57% of impacts in FE and ME, respectively). The scheme of separate waste collection together with biological nitrogen removal and phosphorus uptake via nitrite was identified as the best configuration, with good treated effluent quality and environmental impacts lower than those of the other examined configurations.