Chair for Water Quality Control

The widespread application of nanofiltration (NF) and reverse osmosis (RO) membranes in wastewater reuse inevitably generates a concentrate stream. Due to high concentrations of phosphate and salts, disposal of membrane concentrates is a problem which seriously constrains the application of this technology, especially in inland applications. There is a need for technologies which facilitate an affordable and environmentally-safe disposal of membrane concentrates. The objectives of this study are to investigate appropriate treatment techniques to 1) increase the recovery of the membrane filtration to minimize the volume of the concentrate stream, and 2) decrease the nutrient load of the concentrate to enable discharge into surface water bodies. The results show that chemical precipitation by dosing of sodium hydroxide solution is rapid and removes more than 90 % of phosphate and calcium ions. By the removal of calcium ions, chemical precipitation can significantly reduce the scaling potential of NF and RO concentrates. This may allow for higher recoveries in the NF/RO process