Performance characterization of biological wastewater treatment systems using 5-day biodegradable dissolved organic carbon and ultraviolet absorbance at 254 nanometers

Abstract

Biodegradable dissolved organic carbon (BDOC) and ultraviolet absorbance at 254 nm (UV254) which have been widely used in the drinking water field were investigated for their applicabilities to be used as wastewater quality parameters and treatment efficiency indicators. Three bench-scale biological wastewater treatment processes, activated sludge (AS), trickling filter (TF) and rotating biological contactor (RBC), were fed with primary wastewater from fullscale municipal wastewater treatment plants. First, relatively low organic concentration primary wastewater was used as an influent for TF and RBC that were operated at three different hydraulic loading rates (HLR). The results indicated that effluent BDOC5 and its removal of TF and RBC were not much different across different HLRs but the trends were reasonable. The UV254 reslts indicated that TF and RBC removed minimal amount of UV absorbing constituents. When applying higher organic concentration primary treated wastewater fromanother treatment plant as an influent tothe three biological wastewater treatment systems, AS system was operated at five different solid retention times (SRT), while TF and RBC were operated at four different HLRs. For AS, higher SRTs slightly increased BDOC5 removal but has no effect on UV254 removal. For TF and RBC, the effluent BDOC5 and their removal results were very similar; the values increased with higher HLRs. The UV254 results showed that TF barely removed UV254 absorbing constituents. The applicabilities of BDOC5 and UV254 were supported by a fairly strong linear relationship between BDOC5 and UV254. BDOC5 can be used as an indicator of secondary wastewater quality and treatment process performance, while UV254 can be used only for characterizing quality of wastewater.