Biohazardous Wastewater Treatment by Sequential Combination of Coagulation and Fenton Oxidation

Little attention has been paid to the fast-growing biohazardous wastewater (BHW) in recent years, even though it may pose severe biohazards and toxicity to the general public and environment. Two processes including Fenton oxidation (FO) and a sequential combination of coagulation/flocculation (CF) and FO were evaluated for treatment of actual BHW from biological and pathological laboratories in China. The [H2O2]/[Fe2+] molar ratio was controlled at 20 throughout all FO experiments. The FO performed noticeably well in reducing biohazards and toxicity with 6 g/l H2O2 at initial pH 3 for 24 h, but was unable to remove the organic contaminants efficiently. To reduce the organic load, CF was introduced as a pretreatment. When the CF and FO were operated in sequence, the dosage of H2O2 and its reaction time were significantly reduced to 3 g/l and 4 h at an initial pH of 3.5. Under these conditions, the total plate count (TPC), adenosine triphosphate (ATP), chemical oxygen demand (COD) and linear alkylbenzene sulfonates (LAS) decreased by 100, 100, 96, and 98%, respectively, indicating the biohazards and organic pollutants were significantly reduced. The toxicity indicated by the inhibition ratio of luminescence (IR) was also greatly eliminated (99% removal). This work demonstrates that a sequential combination of CF and FO offered a feasible alternative for treating real BHW by eliminating biohazards, toxicity and organic pollutants simultaneously and effectively. DOI: 10.1061/(ASCE)EE.1943-7870.0000465. (C) 2012 American Society of Civil Engineers.