Arsenic removal by ferric-chloride coagulation - effect of phosphate, bicarbonate and silicate

作者：Laky Dora^*; Licsko Istvan

来源：Water Science and Technology, 2011, 64(5): 1046-1055.

DOI：10.2166/wst.2011.419

• arsenic removal
• drinking water
• ferric-chloride coagulation
• jar-test
• phosphate
• regression analysis
• silicate

Jar tests with synthetic water were carried out in order to investigate the effect of phosphate, bicarbonate and silicate on arsenic removal efficiency by in-situ formed ferric hydroxide. Above 12 mg C/L inorganic carbon concentration, the adverse effect of bicarbonate was definite, and resulted in higher remaining arsenic concentration. At all pH values (7.5-7.8) and coagulant dosages (0.84-3.00 mg/L Fe) tested, the negative effect of phosphate on arsenic removal was also evident. In the presence of silicate small ferric-hydroxide colloids were formed, which were able to go through the 0.45 mu m pore-size membrane. Compared to silicate-free systems, 2.5-3.5 times higher coagulant dose was needed to achieve the target arsenic concentration in the presence of 14-23 mg/L Si. At higher pH values the adverse effect of silicate was even more significant. All data were merged and multiple linear regression analysis was carried out in order to build up a robust model to predict the residual arsenic concentration if the raw water contains 50-60 mu g/L initial arsenic concentration. The estimation was based on the following variables: PO(4)-P concentration, final pH, Si concentration, Fe(III) dose. The most important influencing factors proved to be the silicate concentration and applied coagulant dosage.

• 出版日期2011