A Novel Process for the On-Site Preparation and Application of Polyferric Chloride (PFC) for Surface Water Treatment

Abstract

This is the first study to describe a novel, patented process for the on-site synthesis and subsequent direct utilisation of Polyferric Chloride (PFC) at low Fe concentration dosing, which aims to facilitate the potential replacement of Polyaluminium Chloride (PAC) during surface water treatment (e.g., from reservoirs) for drinking water production. For this purpose, the PFC was synthesised and subsequently used as a coagulant in simulated surface water samples under different synthesis and coagulation/flocculation conditions, namely for different pre-hydrolysed Fe concentrations, pre-hydrolysis pH, coagulation pH, and flocculation times. The effectiveness of PFC was examined mainly in terms of total organic carbon (TOC) removal and the residual Fe concentration. The obtained results showed that the pre-hydrolysed Fe concentration at 0.5 ± 0.25%, pre-hydrolysis at pH 2.5 ± 0.25, coagulation at pH 5.5–7.0 and a flocculation time of 5 min could result in the highest TOC removal (i.e., residual values < 0.60 mg/L) and the lowest residual Fe concentration (<5 μg Fe/L), which is acceptable for a water quality assessment. These values are also substantially lower when compared to the respective TOC and residual metal concentrations using PAC (usually, the relevant obtained values are around TOC > 1 mg/L and Al > 50 μg/L).