Efficiency of sequential UV/H2O2 and biofilm process for the treatment of secondary effluent

In response to the shortage of water resources, multiple processes have been applied to turn wastewater secondary effluent (SE) into potable water. However, trace organic contaminants (TOrCs) and high concentrations of organic matter contained in SE pose a significant challenge to the reclamation. In this manuscript, combined UV-based and biofilm processes were used to treat the SE spiked with ibuprofen (IBU) and clofibric acid (CA). The efficiency of these sequential treatments was characterized in terms of changes in dissolved organic carbon (DOC), absorbance at 254nm (A(254)), fluorescence excitation-emission matrix (FEEM), the concentration of IBU and CA, and molecular weight of SE. Parallel factor (PARAFAC) was applied as the analysis method for FEEM of the samples and two fluorescent components were successfully identified: humic-like substances (C1) and protein-like matter (C2). Large reductions in A(254), C1, C2, IBU, and CA were observed during the UV-based processes, especially with the addition of H2O2. Nearly 50% of A(254), 80% of the component C1 were decreased and almost complete removal of the component C2 and TOrCs was achieved by UV/2.0mM H2O2 after 90-min treatment. During the oxidation processes, the formation of lower molecular weight (LMW) compounds was detected, and the biodegradability of the organic matters was greatly increased. Although no significant DOC reduction was obtained in UV-based processes, an obvious further DOC reduction (3060%) ws chieved by biofilm tretment following UV-bsed processes, especilly fter UV/H2O2 tretments. In the mentime, lrge mounts of LMW were removed in the biofilm tretment process. This mnuscript provides n effective dvnced tretment of SE for the removl of DOC nd TOrCs, fcilitting the wstewter reclmtion.