Membranes and Membrane Technologies | 2021
The Separation of Highly Mineralized Effluents Using Nanofiltration Membranes to Facilitate Their Further Utilization
Abstract
The problems of treatment of various mineralized effluents with the use of reverse osmosis and nanofiltration are considered. It is noted that concentrates from reverse osmosis plants, which have high concentrations of salts and organic substances and are difficult to utilize cause a serious environmental problem. It is proposed to use the separation of the concentrates to solutions containing their components depending on the value of their rejection using nanofiltration membranes. Thus, the concentrates from reverse osmosis plants after the treatment of wastewater, sludge water after dewatering of sludge, as well as concentrates from the municipal solid waste (MSW) landfill leachate treatment plants can be separated to solutions with a high concentration of organic substances and salines (containing ammonium salts), the volumes of which are 10–20-fold lower than the volumes of concentrates. It is demonstrated by way of example of the effluents from ion exchange softening plants, which are a mixture of sodium and calcium chlorides, how multicomponent solutions can be separated to highly concentrated solutions of sodium chloride and calcium chloride to reuse sodium chloride and purified water in production. A technology of separation of solutions is described, which utilizes the dilution of the concentrate with deionized water, which makes it possible to achieve the separation of the solutions to the components depending on their selectivity—the degree of their rejection by nanofiltration membranes.