Prediction of rejection properties and performance of nanofiltration membranes based on scaling prognosis in drinking water treatment

Abstract

Reverse osmosis (RO) and nanofiltration (NF) are widespread for drinking water production from underground water sources; these techniques are used to reduce hardness, iron, fluoride, ammonium, strontium, nitrate, pesticides etc. At the same time, with high efficiency of removing iron, hardness, fluoride, ammonium from source water, nanofiltration membranes are much less exposed to the risk of calcium carbonate precipitation than the traditionally used low-pressure RO membranes. Usually it is important to predict the rejection properties of membranes not only at the launch time of RO/NF unit, but during all operation period and gradual membrane fouling/scaling. The article presents experimental data on determining membrane selectivity (nanofiltration membrane OPMN-K, Russia) for iron. fluoride and ammonium depending on the TDS, water hardness and the amount of calcium carbonate precipitate in the membrane module. Operational guidance has been developed that allow to determine the costs of chemicals for the operation of NF installations depending on the source water quality and membrane type. The above calculations show that the use of nanofiltration membranes instead of reverse osmosis can significantly reduce the cost of operating groundwater treatment facilities.