Currently, one of the main environmental concerns is the toxicity caused by arsenic. Arsenic-polluted water can cause many human health problems including various cancerous diseases. In natural water, inorganic arsenic can be found in the forms of arsenite and arsenate, which have been found in several Iranian provinces – e.g., East Azerbaijan, Kurdistan, and the city of Bijar – in high concentrations. Modern nanofiltration (NF) technology enables a wide range of water resource pollutants to be controlled efficiently. In this study, in an attempt to enhance arsenic removal (both arsenite and arsenate) from drinking water using low pressure NF, operating conditions like arsenic concentration, the trans-membrane pressure applied, and a range of different temperatures have all been considered. The highest arsenate removal achieved was 94% with an initial concentration of 500 μg/L, at 7 bar pressure, and 28 °C. The highest arsenite removal was 90%, with an initial concentration of 100 μg/L, at 5 bar pressure, and also at 28 °C. Increasing the pressure had a positive effect on the removal of both species, however, increasing the temperature had negative impacts. It was always found that arsenate removal was better than arsenite removal.

It is a great advantage to reduce the energy requirement for the provision of consumable groundwater to an absolute minimum. Reverse osmosis (RO) and nanofiltration (NF) are two of the most commonly used technologies for desalination water to provide potable water with lowest energy consumption. However, there is still lack of a thorough comparison between these two methods providing the better option in different conditions. Therefore, in this paper, nitrate rejection and the effects of operation conditions on the performance of RO and NF systems are compared. Several wells in Zarch District, Iran, are polluted by nitrate and groundwater is a major drinking water source in the region. The aim of this research was to evaluate the efficiency of nitrate removal by two commercial membranes NF90 and BW30 (both Dow Filmtec) using natural water under different operating conditions. Experiments were conducted to assess the influence of temperature and pressure on nitrate removal by the membranes. The results indicated that BW30 (reverse osmosis) performs better removing nitrate than NF90 (Nano-filter). With a feed of 200 mg-NO3-.L-1 (as nitrate), only permeate from the BW30 membrane met the required quality standard for drinking purposes (50 mg-NO3-.L-1). When the feed concentration increased to 250 mg-NO3-.L-1 , both membranes failed to achieve the standard in the permeate. The membranes showed similar nitrate removal behaviour under different applied temperatures and pressures. It was concluded that the BW30 membrane can be used to produce drinking water in the study area with influent concentrations below 200 mg-NO3.L-1 .