摘要
This study aimed to investigate the effects of humic acid （HA） on residual Al control in drinking water facilities that used orthophosphate addition. The results showed that adding orthophosphate was an effective method for residual Al control for the raw water without HA. When orthophosphate was added at 1.0 min before the addition ofpoly aluminum chloride （PAC1）, the concentrations of soluble aluminum （Sol-AI） and total aluminum （Tot-Al） residue were 0.08 and 0.086 mg. L J, respectively; both were reduced by 46% compared with the control experiment. The presence of HA would notably increase the residual Al concentration. For the raw water with 5 mg-L^-1 of HA, the concentrations of Sol-Al and Tot-Al increased from 0.136 and 0.174mg.L^-1 to 0.172 and 0.272 mg.L 1, respectively. For water with a HA concen- tration above 5 mg. L ^-1, orthophosphate was ineffective in the control of residual Al, though there were still parts of orthophosphate were removed in coagulation. The amounts of Al removal were positively correlated with the solids freshly formed in coagulation. Similar to the raw water without HA, the best AI control was obtained with orthophosphate salt added at 1.0 min before PAC1. HA concentrations in the raw water, solution pH, and the orthophosphate dosage suitable for residual Al control by orthopbosphate precipitation were also investigated.
This study aimed to investigate the effects of humic acid （HA） on residual Al control in drinking water facilities that used orthophosphate addition. The results showed that adding orthophosphate was an effective method for residual Al control for the raw water without HA. When orthophosphate was added at 1.0 min before the addition ofpoly aluminum chloride （PAC1）, the concentrations of soluble aluminum （Sol-AI） and total aluminum （Tot-Al） residue were 0.08 and 0.086 mg. L J, respectively; both were reduced by 46% compared with the control experiment. The presence of HA would notably increase the residual Al concentration. For the raw water with 5 mg-L^-1 of HA, the concentrations of Sol-Al and Tot-Al increased from 0.136 and 0.174mg.L^-1 to 0.172 and 0.272 mg.L 1, respectively. For water with a HA concen- tration above 5 mg. L ^-1, orthophosphate was ineffective in the control of residual Al, though there were still parts of orthophosphate were removed in coagulation. The amounts of Al removal were positively correlated with the solids freshly formed in coagulation. Similar to the raw water without HA, the best AI control was obtained with orthophosphate salt added at 1.0 min before PAC1. HA concentrations in the raw water, solution pH, and the orthophosphate dosage suitable for residual Al control by orthopbosphate precipitation were also investigated.
基金
This work was supported by Changjiang Scholars and Innovative Research Team in University （PCSIRT） （No. IRT0853）, the National Natural Science Foundation of China （Grant No. 21007050）, and the Natural Science Foundation of Shaanxi （No. 2009JQ7001 ）.
