Investigating the Removal of Residual Iron From Water Through Coagulation by Means of Phosphate Compounds Publisher



Dehghani MH^{1, 2, 3} ; Ghanbari R² Show Affiliations
Source: Desalination and Water Treatment Published:2017

Abstract

The removal of residual iron in conventional and enhanced coagulation process by use of phosphate compounds was investigated. Jar test was performed on sequences of rapid mixing, slow mixing and sedimentation. Addition of phosphate compounds was accomplished during rapid mixing. Phosphate compounds were added to the jars in concentrations of 0.5, 1, 1.5, 2, 2.5, 3 and 3.5 mg L–1. Dosage of ferric chloride in conventional coagulation test was 10 mg L–1, and the experiments took place in different temperatures (35°C, 22°C and 5°C) and pHs (8.5, 7.5, 6.5 and 5.5). Dosages of ferric chloride were 20, 30, 40 and 50 mg L–1 in enhanced coagulation tests, which applied in two pHs (5.5 and neutral pH of water). The results obtained showed that concentrations of residual iron in pH of 5.5, 6.5, 7.5 and 8.5 were 0.32, 0.15, 0.08 and 0.22 mg L–1, respectively. Maximum removal of iron was 0.27 mg L–1, which took place in pH 5.5. Maximum and minimum concentrations of residual phosphate were detected at pHs of 8.5 and 5.5, respectively. Concentration of iron reached its maximum (0.18 mg L–1) in coagulant dosage of 40 mg L–1. Maximum removal of iron in this stage (0.1 mg L–1) happened in coagulant dosages of 30 and 40 mg L–1. Residual iron concentrations in enhanced coagulation at pH of 5.5 were 0.31, 0.72, 0.93, 1.2 and 1.68 mg L–1, which took place in coagulant dosages of 10, 20, 30, 40 and 50 mg L–1, respectively. Maximum removal of residual iron was 0.35 mg L–1, which happened in coagulant dosages of 50 mg L–1. © 2017 Desalination Publications. All rights reserved.