Removal natural organic matter by coagulation-adsorption and evaluating the serial effect through a chlorine decay model

The removal of natural organic matter (NOM) by coagulation and adsorption on modified wheat straw (MWS) was investigated. Two types of inorganic polymer coagulants, polyferric chloride (PFC) and polyaluminum chloride (PAC), were used during experiments. The removal efficiency of NOM in terms of UV254, DOC and CODMn increased with the dosage of coagulants and adsorbent increasing. Combined coagulation and adsorption showed better UV254 and turbidity removal efficiency (61.8% and 95.8% respectively for PFC-MWS, and 61.5% and 94.2% respectively for PAC-MWS) than individual treatment. The effects of combination sequences on DOC fractionation and residual chlorine decay were analyzed and the chlorine data were fitted using a chlorine decay model. In general, the higher the molecular weight of NOM was, the better removal efficiency the combined treatment can achieve. MWS can enhance the removal of NOM with higher molecular weight. The disinfection by-products (DBPs) formation potential in the effluents from coagulation and subsequent adsorption was greater than that in the effluents from adsorption and subsequent coagulation.