Comparative analysis on efficiency of reverse osmosis and alkaline precipitation to remove hazardous substances in a tanning wastewater

Reverse osmosis (RO) with polyamide membrane of spiral wound and precipitation with commercial sodium carbonate were studied to remove hazardous substances [chromium(III), sulfate, chloride and sodium] contained in a tanning wastewater. RO removed chromium(III) very efficiently (99.83%) and with lower but appreciable yields the other three constituents of liquid effluent. Major inconvenience of RO was fast decrease of permeate flux due to insufficient transmembrane pressure used. In turn, 99.71% of chromium(III) was separated with precipitation. Contents of sulfate, chloride and sodium remained without noticeable changes in filtrate liquid. Main physicochemical features of concentrate obtained at the end of RO and of precipitates produced for different reaction times were established.