Adsorption Treatment of Reverse-Osmosis Concentrate from Water-Treatment Units at Thermal Power Stations

Аннотация

Make-up water is treated at thermal power stations (TPS) with high-pressure or superhigh pressure boilers using membrane processes implemented in ultrafiltration, microfiltration, or reverse-osmosis (RO) units. Among the criteria of the efficiency of reverse osmosis units is the amount of highly mineralized effluents (or concentrate). At present, the RO concentrate is disposed of at TPSs by discharging it into an industrial sewage system in accordance with the applicable standards on the salt content limit of waste water, routing it into a district heating network, or returning it into recirculation water supply systems, decreasing as far as possible the volume of the discharged concentrate which is to be reused, for example, in regeneration of Na-cation exchangers installed upstream of the reverse-osmosis unit. The adsorption process is proposed for treatment of the reverse-osmosis concentrate using sludge from the makeup water treatment. The characteristics of carbonate sludge are presented. The regularities of adsorption of sulfate- and chloride-anions from the RO concentrate by carbonate sludge are described. An adsorption isotherm was obtained. The mechanism of adsorption on a sorption material is proposed. The effect of pH on adsorption of sulfate- and chloride-ions by a sorption material was investigated. A system is proposed for the treatment of the concentrate from the RO units at the Kazan Cogeneration Power Station TETs-2 to remove sulfate- and chloride anions using a three-stage adsorption method with a counter-current injection of the sorbent, namely, the carbonate sludge. The calculated values of the consumption of the sorption material required to achieve the desired residual concentration of sulfate- and chloride-anions in the treated water are presented. The economic effectiveness from implementation at the Kazan TETs-2 of the adsorption treatment of the RO concentrate by carbonate sludge to remove sulfate- and chloride-ions is estimated.