Method for treating an effluent supersaturated with calcium carbonate in the presence of phosphonate precipitation-inhibiting products

A method of removing contaminant compounds from a feedwater in a membrane separation system while increasing water recovery rate, the method comprising:

• injecting a precipitation inhibitor reagent into the feedwater;
• directing the feedwater containing the contaminant compounds and the precipitation inhibitor reagent to a membrane separation unit and producing a permeate and a first concentrate supersaturated with the contaminant compounds and containing the precipitation inhibitor reagent;
• directing the first concentrate supersaturated with the contaminant compounds and containing the precipitation inhibitor reagent to a reactor containing suspended solids and having an integrated first solids-liquid separator, a mixing zone in the lower portion of the reactor, and a tranquilization structure in an upper portion of the reactor;
• maintaining a heavy suspended solids concentration of 20-800 g/L in the reactor for the purpose of facilitating the de-supersaturation of the contaminant compounds in the reactor;
• mixing the supersaturated contaminant compounds, the precipitation inhibitor reagent, and the suspended solids in the mixing zone of the reactor;
• wherein mixing the supersaturated contaminant compounds with the heavy concentration of suspended solids in the reactor gives rise to de-supersaturating the supersaturated contaminant compounds in the reactor by continuously precipitating in situ the supersaturated contaminant compounds;
• removing sludge from the reactor wherein the sludge comprises the precipitated contaminant compounds, precipitation inhibitor reagent, and some of the suspended solids;
• recovering from the reactor a treated supernatant substantially free of suspended solids;
• and
• enhancing the water recovery rate of the membrane system by continuously recycling the supernatant to the membrane separation unit, or continuously directing the treated supernatant to a second solids-liquid separator and producing a first filtrate substantially free of suspended solids and a second concentrate and recycling the first filtrate to the membrane separation unit.