การบำบัดสารตั้งต้นของสาร เอ็น-ไนโตรโซไดเมทิลเอมีนในน้ำดิบประปาจากคลองอู่ตะเภา

Abstract

The aim of this research is to study the reduction of dissolved organic nitrogen (DON), dissolved organic carbon (DOC) and precursors to nitrogenous disinfection by-products (N-DBPs) including dimethylamine (DMA), diethylamine (DEA), dibutylamine (DBA), and aniline in raw water from water treatment plant in the U-Tapao canal, Hat Yai, Songkhla, Thailand. A polyaluminium chloride (PACI) coagulation, PACI coagulation with powder activated carbon (PAC), PACI coagulation with PAC followed by nanofiltration (NF) and reverse osmosis (RO) membranes were used for conducting the experiments. Water samples were collected three times. Raw water from the second and third samplings were used for the experiments of organic matter reduction. DOC, DON, and trihalomethane formation potential (THMFP) of raw water from the second and third samplings were 5.3 and 4.6 mg/L, 0.62 and 0.18 mg-N/L, and 486 and 384 ugL, respectively. N-nitrosodimethylamine (NDMA) formation potential of raw water and NDMA in water supply were not detected at detection limit of quantity at 237 ng/L. DMA, DEA, DBA, and aniline were not detected in raw water at the second and third samplings. DMA, DEA, DBA, and aniline of 5 ug/L were added into raw water and coagulated water for conducting the experiments of organic matter reduction. On average, the PACI of 40 mg/L at pH 7 reduced DOC and THMFP by 22 and 37 %, respectively but reduced DON in raw water of the second sampling by 48 %. The PACI of 40 mg/L at pH 7 reduced DMA, DEA, DBA and aniline by 33, 28, 16, and 32 %, respectively. The PACI 40 mg/L combined with PAC 20 mg/L at pH 7 reduced DOC and THMFP of raw water by 27 and 88%, respectively but reduced DON in raw water of the second sampling by 52 %. The PACI 40 mg/L at pH 7 combined with NF reduced DOC, DON, THMFP by 74, 39, and 86 %, respectively and reduced DMA, DEA, DBA, and aniline by 31, 51, 92 and 77%, respectively. The PACI 40 mg/L at pH 7 combined with RO reduced DOC DON and THMFP by 80, 50, and 90 %, respectively, and reduced DMA, DEA, DBA, and aniline by 33, 94, 97 and 87%, respectively. The PACI coagulation with PAC slightly increased DON reduction. The PACI coagulation combined with RO provided the better reduction of DOC, DON, DMA, DEA, DBA, and aniline in comparison to the PACI coagulation combined with NF.