Evaluating the suitability of synthetic organic polymers to replace iron salts in the purification of humic and sediment-rich runoff

Peat extraction runoff water requires chemical treatment to remove organic matter and phosphorus. In Finland, ferric sulphate (FS) is normally used as coagulant agent, but significant variations in runoff water quality and the lack of optimisation of process parameters has led to increased acidity, metal and sulphate concentrations in the purified water. The use of synthetic organic polymers as an alternative to the commonly applied metal salt coagulant is suggested to better cope with typical variations in runoff water quality. This study evaluated the suitability of two synthetic organic polymers (polyDADMAC and polyAmine) for the purification of humic and sediment-rich diffuse runoff by comparing their performance to the normally applied iron-based coagulant. FS was found to require up to fourfold higher dosages but achieved higher overall purification levels than the organic polymers. In particular, removal of organic matter was substantially higher when FS was used. Of the two synthetic organ...