Treatment of membrane concentrates: phosphate removal and reduction of scaling potential

摘要

The widespread application of nanofiltration (NF) and reverse osmosis (RO) membranes innwastewater reuse inevitably generates a concentrate stream. Due to high concentrations ofnphosphate and salts, disposal of membrane concentrates is a problem which seriously constrainsnthe application of this technology, especially in inland applications. There is a need forntechnologies which facilitate an affordable and environmentally-safe disposal of membranenconcentrates. The objectives of this study are to investigate appropriate treatment techniques ton(1) increase the recovery of the membrane filtration thus minimising the volume of thenconcentrate stream, and (2) increase the concentrate quality to enable discharge into surfacenwater bodies. The results show that both adsorption onto granular ferric hydroxide (GFH) andnchemical precipitation are generally effective for phosphate removal from NF concentrates.nChemical precipitation by dosing of sodium hydroxide solution is rapid and removes more thann90% of phosphate and calcium ions. By the removal of calcium ions, chemical precipitation cannsignificantly reduce the scaling potential of NF and RO concentrates. This may allow highernrecoveries in the NF/RO process.