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Reduction of fractionated dissolved organic matter and their trihalomethane formation potential with enhanced coagulation

Charongpun Musikavong^a,b,*, Kamonnawin Inthanuchit^a, Kanjanee Srimuang^a, Thunwadee Tachapattaworakul Suksaroj^c, Chaisri Suksaroj^a

 
ABSTRACT:     The trihalomethane formation potential (THMFP) of the raw water supply from the U-Tapao Canal, Songkhla, Thailand and the THMFP of the hydrophobic organic fraction (HPO) and hydrophilic organic fraction (HPI) of the raw water supply were determined. The canal has been contaminated with treated and untreated wastewater from communities, agricultural processes, and industrial activities. Water samples were collected 3 times from an intake point of the water treatment plant located downstream of the canal. We found an average dissolved organic carbon (DOC) of 7.4 mg/l and a THMFP of 630 µg/l in the raw water. We also found a DOC_HPO of 3.3 mg/l, a DOC_HPI of 3.7 mg/l, a THMFP_HPO of 281 µg/l, and a THMFP_HPI of 348 µg/l. Strong fluorescent peaks of tryptophan-like and humic and fulvic acid-like substances were detected in the raw water. The optimal condition of polyaluminium chloride (PACl) coagulation for removing dissolved organic matter was obtained at a PACl of 40 mg/l at pH 7. Under such conditions, it could reduce the average DOC to 55% and THMFP to 48%. The PACl coagulation reduced the fluorescent intensity of humic and fulvic acid-like substances more than tryptophan-like substances. The best reduction observed of DOC was 76% and THMFP was 83%; this was obtained by using a PACl of 40 mg/l with 1 mg/l of polymer and 80 mg/l of powder activated carbon. Under such conditions, there was consistent removal of an average DOC_HPO, DOC_HPI, THMFP_HPO, and THMFP_HPI by 85, 68, 81, and 79%, respectively. Such a condition was capable of reducing trihalomethanes to meet the World Health Organization standards.

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* Corresponding author, E-mail: mcharongpun@eng.psu.ac.th

Received 26 Jun 2012, Accepted 1 Oct 2012