Natural organic matter (NOM) removal from surface water by coagulation

Poly-aluminum-chloride-sulfate(PACS) with different SO4(2-)/Al3+ mole ratios and bacicity(y) of 2.0 was synthesized using AlCl3 x 6H2O, Al2 (SO4 )3 x 18H2O and Na2CO3 as raw materials. The effect of SO4(2-)/Al3+ ratio on the performance of PACS for removal of natural organic matter(NOM) with humic-rich actual water was examined. It was found that PACS with SO4(2-)/Al3+ mole ratio of 0.0664 achieved the best NOM removal results and was selected to investigate its performance in comparison with PAC, FeCl3 and alum (Al2 (SO4)3 x 18H2O). The experimental results showed that the optimum NOM removals were achieved at pH 5.0-8.2 and the dose of about 5.0 mg/L as Al both for the selected PACS and PAC, at pH 5.0-6.0 and the dose of about 7.0 mg/L as Fe for FeCl3, and at pH 5.0-7.0 and the dose of about 7.0 mg/L as Al for alum, respectively. At the optimum conditions, the selected PACS achieved the best NOM removal result, followed by PAC, FeCl3, and then alum. The concentration of residual aluminum in treated water by the selected PACS and PAC under the optimum coagulant conditions was approximately 115 microg/L, which can completely comply with the regulated limits.