Effect of control parameters of biological wastewater treatment systems on biodegradable dissolved organic carbon in effluents

Abstract

In the last few years, biodegradable dissolved organic carbon (BDOC) methods have been studied and used for characterizing the quality of secondary treated wastewater from activated sludge (AS) process. However, BDOC removal efficiency through AS process treating actual wastewater has not been investigated. Furthermore, BDOC has never been applied to processes other than AS. In this study, two bench-scale AS and trickling filter (TF) processes and a full-scale rotating biological contactor (RBC) process experiments were conducted using actual primary wastewater to determine the effect of SRT and HLR on BDOC in the effluents. For the bench scale experiments, BDOC removal at different SRTs and HLRs was also determined. Effluent BDOCs were lower at higher SRTs and lower HLRs for the AS and TF processes, respectively. An excellent relationship between BDOC removal and SRT was obtained from the AS experiment. Secondary wastewater effluent from the full-scale RBC contained relatively high BDOC (2.8 and 1.5 times of BDOC in the effluents of AS and TF, respectively) of which 30 to 80% was biodegradable during the BDOC test. BDOC correlated well with dissolved organic carbon (DOC) and soluble biochemical oxygen demand at 5 days (SBOD5). However, a poor relationship was observed between BDOC and ultraviolet absorbance at 254 nm (UV254) of RBC effluent. SBOD5 and BDOC were analyzed simultaneously to compare the precision between the two methods. Results show that the BDOC method is substantially more precise than the SBOD5 method