Disinfection by-product (DBP) and Its Precursors Reduction by PAC,Alum, PACl, and MIEX

摘要

Small drinking water systems using surface water sources will soon have to comply with the Stage I Disinfectants/Disinfection By-Products (D/DBP1) Rule (January 1st, 2004). Small systems have the most difficulty meeting federal compliance standards for drinking water,rnbecause the treatment technology that may be affordable to large-scale operations may not bernaffordable for small-scale operations. Therefore, solving small system compliance problemsrnare the most difficult problems in the water industry. The overall objective of this researchrnwas to study the treatment of a variety of Missouri surface waters using techniques applicablernto small systems such as powdered activated carbon (PAC), aluminum sulfate (alum),rnpolyaluminum chloride (PACl), and anion exchange resin (MIEX) for removal of NOM andrnminimization of DBPs by single and sequential treatments. This study demonstrated thatrnPAC treatment is unlikely to be a sole remedy to DBP problems because it cannot remove arnsufficient amount of NOM at reasonable doses (30 mg/L). MIEX treated water had thernhighest Ultraviolet absorbance (UVA) and Total trihalomethanes (TTHM) removal at 88 %rnand 86 %, respectively. For alum treatment, a minimum dose of 20 mg/L was required torndestabilize the particles, causing a decline in UVA254. Lower pH improved alum and PAClrnperformance. Sequential treatment clearly showed better UVA removal than single PAC orrnalum treatments. Sequential treatment for alum/PAC is at least 42 % to 47 % higher than PAC treatment alone and 6 % to 26 % higher than alum treatment alone, whereas sequential treatment for PACl/MIEX is at least 10 % to 26 % higher than PACl alone and 5 % to 33 % higher than MIEX alone. TTHM versus UVA and UFC chlorine dose (C24) correlation analysis showed that the UVA was better than C24 and DOC for predicting TTHM for most waters.