engleski

RO/NF Treatment of Wastewater from Fertilize Factory - Removal of Fluoride and Phosphate

The fertilizer industry generates effluents with large amounts of fluoride and phosphate. The objective of this study was to investigate the feasibility of applying reverse osmosis (RO) and nanofiltration (NF) membrane separations to reduce fluoride load to less than 8 mg L-1 and phosphate load to less than 2 mg L-1. The porosity of separation membranes was determined indirectly by solute transport method determining pore size in the selective membrane layer. The membranes’ porosity characterization showed unimodal pore size distributions (PSDs) for RO membranes (LFC, ULP and XLE) and tight NF membrane (NF90) with most pores at the size of 0.70 nm and 0.82 nm respectively. Completely different PSD has the loose NF membrane, HL, which is bimodal with two clearly separated peaks. The present study indicated that the rejections of fluoride with RO membranes were higher than 80% (model waters) and higher than 96% (real wastewater), and with NF membranes higher than 40%. Rejections of phosphates were higher: > 95% (model waters) and > 97% (real wastewater). Membrane treatments showed very good efficacy for removal of fluoride and phosphate from fertilizer company wastewater and meet all MCLs according to Croatian law.

fertilizer wastewater; fluoride; phosphate; membranes; RO/NF treatment

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