Pretreatment of Locomotive Direct Drinking Water by Nanofiltration

With the development of high-speed railway, the technology of water supply and drinking water treatment needs to be improved urgently. Experiment study was conducted for drinking water treatment by nanofiltration with NaCl and MgSO₄ solutions to simulate water supply in locomotive. Two spiral-wound nanofiltration membranes (NF1 and NF2) were used to study the relationship between desalination rate and water production. The parameters such as conductivity, temperature and pressure on membrane performances were analyzed. The results indicated that the water production salinity of the two membranes were inversely proportional, when the conductivity is lower than 900 μs/cm, while the water production can be maintained at 40∼50GPD, the rejection of NaCl and MgSO₄ for NF2 were both greater than 95% under the test conditions, while NF1 for the rejection of NaCl was about 45%∼60% and of MgSO₄ more than 80%;The water production was proportional to temperature, and NF1 was slightly higher than NF2.At certain temperatures, the water production capacity of both membranes for NaCl was about 10∼15 GPD higher than MgSO₄.NF1 and NF2 on the removal of MgSO₄ was about 97%∼98%,while NaCl was 45%∼55% and 96%∼98% respectly;The production capacity and rejection of both membranes were proportional to the operating pressure.The rejection of NaCl was close to 70% for NF1 and 80% for NF2,while of MgSO₄ was more than 95.5% for NF1 and 97% for NF2.