METHOD FOR TREATING HIGH CONCENTRATION WASTEWATER SUCH AS RO BRINE

摘要

High strength industrial water, including reverse osmosis brine, is treated with a nanofiltration (NF) membrane unit. In one system and process, NF retentate is recirculated to the NF unit through a softener. Feedwater may also flow to the NF unit through the softener. Sodium carbonate is added to the softener to form calcium carbonate precipitates which are removed from the softener effluent by a microfiltration membrane. The hardness of water flowing to the NF unit is reduced only as much as required to avoid scaling in the NF unit. In another system and process, an aqueous solution comprising sulfate is added to feedwater flowing to an NF unit. Sulfate may also be added to wastewater fed to the first system and process.