Photochemical treatment of an actual municipal wastewater by means of UV, potassium persulfate and iron

The photochemical treatment of an actual municipal wastewater (MWW) from wastewater treatment plant (WWTP) in Kazakhstan has been studied in the present work. The MWW has been taken after mechanical treatment stage and characterized. The photochemical treatment included the use of the photo-Fenton-like process in the batch photoreactor with a UV irradiation at 254 nm for 120 min. Experiments have been done without adjusting the initial pH of wastewater, which was around 7.7. Potassium persulfate (K2S2O8) was activated by means of UV and ferric ions, which led to generation of highly oxidative sulfate and peroxymonosulfate radicals. The concentration of Fe2+ ions ranged from 20 to 100 ppm, while the concentration of K2S2O8 was in between 5 and 25 mmol/L. 83% removal of total organic carbon (TOC) was achieved after 120 min of treatment using 15 mmol/L K2S2O8 and 20 ppm Fe2+, while 75% removal of total carbon (TC) was observed at 15 mmol/L K2S2O8 and 100 ppm Fe2+. As the carboxylic acids are common organic intermediates after photochemical treatment, the presence of formate and acetate anions in effluents were further detected on the ion chromatography.