The invention relates to sewage treatment, and more particularly to a system for treating reverse-osmosis concentrated water with permanent hardness. The system includes a first crystallization unit, a first reverse osmosis unit, a second crystallization unit, a lime softening unit and a second reverse osmosis unit, which are connected in sequence. The system of the invention is able to eliminate the permanent hardness and the temporary hardness of the concentrated brine, and the hardness can be reduced to equal to or less than 50 mg/L.

Lithium brine is treated with a multiple pass nanofiltration (NF) membrane system. Sulfate is added to permeate from an upstream pass before it flows through a downstream pass. Optionally the sulfate may be added to the permeate by dosing it with sulfuric acid or a slat such as sodium sulfate. The softened brine may then be processed further, for example by a combination of solvent extraction, electrolysis, crystallization and drying, to produce a lithium hydroxide product that can be used to make batteries.

An aqueous solution flows through a desalination system that separates the aqueous solution into purified water and concentrated brine. The concentrated brine is directed into an electrodialysis system that includes an anode and a cathode and at least two monovalent selective ion exchange membranes between the anode and the cathode. At least one of the monovalent selective ion exchange membranes separates at least one diluate channel from at least one concentrate channel in the electrodialysis system, and this membrane selectively allows at least one monovalent ion to pass through the membrane while blocking or inhibiting the transport therethrough of multi-valent ions. The concentrated brine flows through at least the concentrate channel while a voltage is applied to the anode and cathode; and additional aqueous solution flows through the diluate channel.

A method of treating mining effluents containing at least one of nitrogen or cyanide species, the method comprising injecting ozone in the mining effluent in successive treatments performed at different pH. Also, a method of treating mining effluents with bromide and ozone. Also, a method of treating mining effluents containing cyanates with ozone at a relatively low pH.

According to some embodiments, a system for desalination of a liquid comprises at least one primary treatment process, at least one secondary treatment process, wherein the at least one secondary treatment process comprises at least one reactor, and at least one tertiary treatment process, wherein the at least one primary treatment process is configured to adjust a pH of the liquid to target pH level and to add at least one chemical additive to the liquid, wherein the at least one reactor is configured to heat the liquid to a temperature of at least 350 F. and to supply a pressure to the liquid to maintain the liquid in a liquid state, and wherein the dissolved salt of the liquid is configured to react with at least a portion of the at least one chemical additive to form an insoluble product within the at least one reactor.

A method of treating a metal carbonate salt includes hydrolyzing a metal halide salt to form a hydrohalic acid and a hydroxide salt of the metal in the metal halide salt. The metal includes an alkaline earth metal or an alkali metal. The method includes reacting the hydrohalic acid with the metal carbonate salt, wherein the metal carbonate salt is a carbonate salt of the alkaline earth metal or alkali metal, to form CO.sub.2 and the metal halide salt. At least some of the metal halide salt formed from the reacting of the hydrohalic acid with the metal carbonate salt is recycled as at least some of the metal halide salt in the hydrolyzing of the metal halide salt to form the hydrohalic acid and the hydroxide salt.

A method of treating a metal carbonate salt includes hydrolyzing a metal halide salt to form a hydrohalic acid and a hydroxide salt of the metal in the metal halide salt. The metal includes an alkaline earth metal or an alkali metal. The method includes reacting the hydrohalic acid with the metal carbonate salt, wherein the metal carbonate salt is a carbonate salt of the alkaline earth metal or alkali metal, to form CO.sub.2 and the metal halide salt. At least some of the metal halide salt formed from the reacting of the hydrohalic acid with the metal carbonate salt is recycled as at least some of the metal halide salt in the hydrolyzing of the metal halide salt to form the hydrohalic acid and the hydroxide salt.

A system and method for increasing total dissolved solids (TDS) concentration and pH of water is provided herein. The water is processed using a variety of filtration and purification methods, including carbon filtration, water softening, reverse osmosis, and electrodeionization. After filtration and purification, the water is pumped into a mineral infusion chamber, including a plurality of bioceramic components. At least one TDS sensor monitors the TDS concentration of the water stream, and a flow rate out of the mineral infusion chamber is controlled by a flow control valve based on sensor data produced by the at least one TDS sensor.

As pellets grow from seed/sand in a fluidized bed pellent reactor, the weight of the reactor is measured and the density of the contents of the reactor is calculated, and the input flow of untreated water, water treatment chemical, and seed/sand are adjusted to provide improved removal of water hardness while reducing fine particulates in the outflow of softened water from the reactor.

Per- and polyfluoroalkyl substances (PFAS) are destroyed by oxidation in supercritical conditions. PFAS in water is concentrated in a reverse osmosis step and salt from the resulting solution is removed in supercritical conditions prior to destruction of PFAS in supercritical conditions.