Relationships between trihalomethane formation potential and natural organic matter surrogates in raw water and coagulated water of shallow wells near a closed unsanitary solid waste dumping site

Abstract

Relationships between trihalomethane formation potential (THMFP) and natural organic matter (NOM) surrogates in raw water and coagulated water of shallow wells near a closed unsanitary solid waste dumping site at Mae-Hia District, Muang, Chiang Mai, Thailand were studied. Raw water samples from the observed wells near the area of dumping site named the observed wells near the area of dumping site named the observed well no. 1 and 3, and the observed wells in the area of dumping site named the observed well no.2 were collected once a month from September 2003 to January 2004 for THMFP, DOC, TOC, and UV-254 determination. The results shows that the average values of THMFP in raw water from the observed well no.1, 2 and 3 were 139.08+-32.68 microgram/L, 209.91+-26.26 microgram/L and 191.02+-38.89 microgram/L, respectively, which were higher than a maximum contaminant level (MCL) of THMs in drinking water of 80 microgram/L proposed by the USEPA. The mostTHMFP species of about 60% of THMFP was found in term of Chloroform in raw water from the observed wells, in addition, the THMFP species of approximately 23% and 15% of THMFP in forms of Dichlorobromoform and Dibromochloroform were determined, respectively, while very low concentration of Bromoform was detected. Regard to NOM surrogates parameters, it was found that the values of NOM surrogates in the raw water of the observed well no. 2 was higher than those of in the observed wells no 1 and 3. The average values of TOC of 2.58+-1.53 mg/L, 12.22+-5.37 mg/L and 3.03+-1.81 mg/L, whereas the average values of DOC of 1.78+-0.89 mg/L, 9.24+-6.09 mg/L and 2.57+-1.40 mg/L, and the average values of UV-254 of 0.25+-0.04, 15.65+-0.49 and 0.32+-0.06 were observed in the raw water from the observed wells no.1, 2 and 3, respectively. Based on, the matrix relationships among surrogates for NOM which established and according to the degree of correlations categorized by AWWA., it was demonstrated that the relationships between THMFP and TOC in raw water was classified as good correlations while, in coagulated water, the relationships between THMFP and chlorine demand, and that of THMFP and DOC, including and that of THMFP and UV-254 were also categorized as good correlations.