Natural organic matter removal from algal-rich water and disinfection by-products formation potential reduction by powdered activated carbon adsorption

Algal blooms intensified operational problems in water treatment due to the increases of taste- and odor-causing compounds and natural organic matter (NOM). Effects of powdered activated carbon (PAC) addition during algal blooms on NOM removal was investigated in this study using an algal-rich water. Water quality analyses including dissolved organic carbon (DOC), ultraviolet absorbance at 254 nm (UV254) and specific UV absorbance (SUVA) were performed to elucidate characteristics of NOM removal by PAC adsorption. Variations of MW distributions and emission/excitation matrix (EEM) spectra with increasing PAC dosages were also measured. In addition, formation potential (FP) of trihalomethanes (THMs), haloacetic acids (HAAs), and haloacetonitriles (HANs) was evaluated with increasing PAC dosage. The correlations between disinfection by-products formation potential (DBPFP) and water qualities such as DOC, UV254, SUVA, and EEM spectra were also investigated to identify factors associated with DBPFP. The PAC addition was effective to remove NOM, especially low molecular weights NOM and proteinaceous substances with weak aromatics. The PAC addition showed the consistent reduction of THMFPs, HAAFPs, and HANFPs with increasing PAC dosage while the greater reduction of HAN precursors was eminent compared to the other two FPs. The close correlations between UV254 and the three DBPFPs were obtained. The low molecular weight (i.e., 1-700 Da) NOM and three fluorescence spectra peaks, i.e., T-1, A and C peaks, also showed high correlation factors with the three DBPFPs. Those analyses with high correlations with DBPFPs would provide useful information to reduce DBPs during algal blooms.