Development of a new Poly Silicate Ferric coagulant and its application to coagulation-membrane filtration hybrid system in waste water treatment

Coagulation is one of the effective pretreatments in membrane filtration of waste waters to produce clean water. Using a suitable coagulant can mitigate membrane fouling, which is the major drawback of membrane filtration technology in wastewater treatment. Research in this area is currently being focused on development of improved coagulation reagents such as poly silicate ferric (PSiFe), which has high molecular weight and posses large number of positive surface charges and therefore expected to be very efficient as a coagulant at low dosages.. In this paper. PSiFe is prepared following two approaches: (a) Acidification of water glass solution using HCl followed by FeCl3 addition (old- PSiFe); (b) Acidification of water glass solution by passing it through an acidic ion exchange resin followed by fresh FeCl; addition under different Fe/Si molar ratios (new-PSiFe). These coagulants were characterised by X-ray diffraction and scanning electron microscopy . Coagulation jar test showed that Fe/Si ratio of 1 was the best in turbidity, total organic carbon and UV254 removals. A comparison of the effect of old-PSiFe, new-PSiFe, and FeCl3, in pre coagulation in a membrane filtration system showed that, Trans Membrane Pressure (TMP) drop (low fouling) as well TOC removal efficiency were superior when the newPSiFe was used compared to the other two coagulants.