THMs precursor removal by an integrated process of ozonation and biological granular activated carbon for typical Northern China water

The removal of trihalomethanes (THMs) precursor and natural organic matter (NOM) by an integrated process of ozonation and biological granular activated carbon filtration (BGAC) as a deep water treatment process was investigated in pilot-scale tests. A comparison is also made with granular activated carbon filtration (GAC). The characteristics of the THMs precursor and the THMs formation potential (THMFP) were investigated by resin adsorption and ultrafiltration. The results show that the integrated process of ozonation and BGAC (O3/BGAC) is obviously superior to GAC for the removal of the THMs precursor because a considerable synergetic effect occurs between the ozonation and the BGAC. Although ozonation can limitedly remove dissolved organic carbon (DOC), it can cut down the molecular weight of the NOM, change its polarity, decrease the THMFP, and obviously enhance the efficiency of the BGAC. The BGAC could efficiently remove the hydrophobic base (HoB), hydrophobic neutral (HoN), weakly hydrophobic acid (WHoA), and low molecular weight fraction DOC that was produced in the optimized ozonation process. However, the BGAC stage should be carefully controlled to avoid the leakage of microbes and/or the products of metabolism because it has a high risk for producing THMs in following chlorination process.