Removal of dissolved organic matter via a combination of UV/persulfate oxidation and biological activated carbon (BAC) process

The combination process of UV/peroxydisulfate (UV/PDS) oxidation and BAC (UV/PDS-BAC) is examined as an advanced treatment for conventional drinking water treatment through a continuous flow experimental apparatus with actual sand filter effluent as feed water. The effect of three key parameters (UV dosage, PDS dosage, and water temperature) on dissolved organic matter (DOM) is evaluated via long-term monitoring data. The removal behavior of DOM in the UV/PDS-BAC process is also compared with that in the O3-BAC process. Further, this study delves into the mechanisms behind the enhanced DOM removal achieved by UV/PDS-BAC. The achieved results reveal that impressive removal rates of 42.1 % for total organic carbon (TOC) and 62.9 % for UV254 could be achieved in the presence of specific conditions: a UV input of 200 mJ/cm2 and a PDS dosage of 0.5 mM. The efficiency of DOM removal by UV/PDS-BAC exhibits a positive correlation with the UV dosage ranging from 50 to 200 mJ/cm2, and the water temperature in the range of 4–30 ℃. While increasing the PDS dosage from 0.01 to 0.5 mM results in improved DOM removal, any further increase yields reduced removal efficiency. In comparison, subjected to similar operating conditions, UV/PDS-BAC outperforms O3-BAC in removing DOM. The superior DOM removal achieved by the UV/PDS-BAC process can be essentially attributed to several factors: firstly, it exhibits excellent mineralization capacity for low molecular weight organics (<1 kDa) and leads to increased biodegradable fraction of organics by oxidatively degrading DOM with a molecular weight >3 kDa. Secondly, the appropriate exposure of activated carbon pores is chiefly maintained by suitably controlling the biomass. Lastly, the enhanced biodegradability of BAC influent stimulated the growth of bacteria proficient in degrading DOM.