HOWIE can provide a combined system including ultrafiltration(UF), nanofiltration(NF), reverse osmosis(RO) and special membranes, NF is used to retain divalent and above ions and is often used in the salt separation process for the separation of sodium chloride and sulfate ‌. RO is suitable for desalination and concentration of high-salt wastewater. Combining processes according to different water conditions can significantly increase the water resource recovry and salt resource utilization, ‌ reduce investment, energy consumption and land space.