Improve coagulation process to control the disinfection by-products in water treatment plant

Abstract EN

This paper describes a laboratory study comparing three coagulants (alum, ferric chloride, and ferric sulfate) to determine which coagulant would not only remove NOM but DBP precursors as well.

Experiments were conducted to compare the effectiveness of three coagulants in removing DBPs precursors from raw water samples.

The results show that the removal of total organic carbon (TOC) which is mean NOM here, was dependent on the coagulant type and was enhanced with increasing coagulant dose, but ferric chloride, and ferric sulfate have no further considerable effect in case of increasing to high levels.

For all the treated samples coagulation with ferric chloride proved to be more effective than alum and ferric sulfate at similar doses and the mean values of treatment efficiencies were 30 %, 37 %, and 45 % by ferric sulfate, alum, and ferric chloride respectively.

The range of TOC removal rates obtained using ferric sulfate (18-48 %), (14-50 %) for alum, and (21-59 %) for ferric chloride.

Ferric chloride was therefore considered the better chemical for enhancing the coagulation process.

Fair removals of turbidity were observed (86 %) for ferric chloride, (78 %) for alum, and 65 % for ferric sulfate.

Mean TOC removal using alum was determined to be 61 % and much more than results of water coagulation by ferric sulfate which was reported to be 53 % in experiments performed for treating Euphrates river water.

Among the Trihalomethanes compounds, chloroform was the common detected Trihalomethanes in the samples collected from Euphrates Riverwere generally below the guideline values, but some samples displayed levels which exceeded the level of WHO Standards for chlorinated compounds.

Based on preliminary jar test experiments, ferric chloride at concentrations of 20-30 mg / L was found as an efficient coagulant for disinfection by- products and turbidity reduction.