Hybrid Nano-filtration and Micro-filtration Pilot Processes for the Removal of Chromium from Water

Heavy metal hexavalent chromium is known as a highly toxic compound and based on World Health Organization standards in concentrations greater than 50 micrograms per liter would lead to diseases such as allergic reactions, skin cancer, lung cancer, damage to the kidneys and liver, and also changes in the shape of the DNA genetic. The aim of this study was to evaluate the performance of the hybrid system of nano-filtration and micro-filtration processes to remove hexavalent chromium from water. Pilot implementation of 1 and 5 micron filters, sand filters, activated carbon filters, and NF (NF 90-400) was built. The effects of various parameters such as pH, pressure, concentration of chromium, concentration of sulfate and total dissolved solids (TDS) were studied on the removal of hexavalent chromium from drinking water. Pressure was changed from 0.1 to 0.4 MPa, pH was set in the range of 2 to10, the concentration of hexavalent chromium was in the range of 100 to 400 micrograms per liter and the concentration of sulfate oral solution was changed between 40 and 500 milligrams per liter. The results showed that the efficiency of chromium removal increased as pH was increased. The removal of chromium dropped when the pressure was increased from 0.1 to 0.4 MPa. In addition, a decreasing trend was observed in removal efficiency by increasing the concentration of chrome and sulfate. Optimal levels of hexavalent chromium concentration was 100 micrograms per liter. For pressure, pH, and sulfate concentration the optimal levels were 0.1 Mpa, 10 and 40 milligrams per liter, respectively. In general, pilot and experimental results showed that the system provided the ability to remove chromium in drinking water (tap water and distilled water) at a rate of 99%.