The anaerobic baffled reactor (ABR) has been implemented by the Bremen Overseas Research and Development Association (BORDA) as a standard secondary treatment component in decentralized wastewater treatment systems (DEWATS) that yields water suitable for non-potable uses. The ABR provides chemical oxygen demand (COD) removals on the order of 40% - 60%. Although BORDA has installed over 2500 ABR systems around the world, there is still much to be understood regarding the diurnal patterns in ABRs under real-world conditions, such as variable wastewater loadings and flow rates. The purpose of our research was to track the diurnal variability of wastewater characteristics in an ABR coupled to an anaerobic filter (AF), treating medium strength domestic wastewater for agricultural water reuse in an urban setting in Durban, South Africa. Multiple water quality parameters, including COD, dissolved organic carbon, and total dissolved nitrogen were measured in the first and last chambers of the ABR-AF system 3x per day. Tryptophan-like (TRP) fluorescence, which is known to be representative of biologically-labile organic constituents, and humic-like (CDOM) fluorescence intensities were recorded every 45 min using a submersible fluorometer. This study confirmed previous observations of significant relationships between TRP fluorescence and COD concentrations. COD concentrations measured at 9:30, 11:45, and 14:00 varied substantially, ranging from ~360 mg/L to 650 mg/L in the first chamber and from ~250 mg/L to 360 mg/L in the last chamber. Additional experiments using a bench-scale system revealed that periods of low or no flow led to much higher COD removal and preferential removal of the TRP fluorescent fraction. Results from the bench-scale ABR are being considered in the context of the real world system to evaluate how periods of low flow may influence the high variability in TRP fluorescence and COD concentrations that was observed in this study. Ultimately, a process-level understanding of the factors that influence in ABR performance under real-world conditions are important for promoting wide applications of DEWATS for domestic wastewater treatment and water reuse.

Diurnal variability in organic matter constituents in an anaerobic baffled reactor treating domestic wastewater for agricultural water reuse applications

255th National Meeting (2018)

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