膜科学技術ジャーナル

概要

Treatment of Leather Industry Wastewater With Sequential Forward Osmosis (FO) and Reverse Osmosis (RO) Hybrid Processes and Recoveries

Delia Teresa Sponza

The leather industry wastewaters have high COD, turbidity, pH, conductivity, Total Solids (TS), Suspended Solids (SS), sulphate, chlorides, chromium and colour. A pre-filtration device was used with a 25-micron pore size cartridge before FO experiments. FO membrane had symmetric channels on both sides of the membrane was made from commercial Cellulose Triacetate (CTA). This allowed for both the feed and draw solutions to flow tangential to the membrane. The variation of increasing of water flux (5, 7, 9, 12, 15, 17, 18 and 20 L/m2h) on the draw solid concentrations and effects of operating times (30, 60, 80, 90 and 100 min) on the water flux were studied in FO membrane. The variation of recovery percentage versus time and the effects of flow rates (30-220 L/h) on the rejection efficiency and the removals of the pollutant removals (COD, turbidity, pH, conductivity, Total Solids (TS), Suspended Solids (SS), sulphate, chlorides, chromium and colour) were studied in FO. RO experiments were performed in a spiral wounded membrane. Effect of increasing pressures (4, 8, 16 and 20 bar) and operating times (10, 20, 30, 60, 80 and 100 min) on the permeate flux was studied at a temperature of 25 °C. A linear positive correlatıon between applied pressure and water flux was detected as the pressure was increased from 2 bar to 20 bar in FO. At higher draw solution at constant pressure, both rejection and water flux increased in FO. The recovery percentage both in distilled water and in leather industry versus operating time in FO. Flow rate flux decreased slightly throughout 60 min of operation, then it reached at a plateau at Jw values of 278 L/m2h and 265 L/m2h respectively. The maximum COD, turbidity, conductivity, TS, SS, sulphate, chloride and chromium and colour removals were 90%, 89%, 91%, 91%, 91%, 88%, 90%, 87% and 91%, respectively, in the permeate of the FO at 16 bar pressure while the removals of these parameters varied between 98% and 99% in RO at a transmembrane pressure of 20 bar. The high COD concentrations at 20 bar pressure did not decrease the permeate flux in RO. The permeate flux is not dependent on time. The highest permeate flux was detected as 781 and 760 after 30 min in distilled water and leather industry, respectively. The permeate of the RO meets wıth the dıscharge standards of water quality for irrigation water while 2380 g/l chromium, 1263 g/l gelatine, and 1134 g/l gelatine were recovered from the RO retentate/concentrate during the treatment of 1 m3 leather wastewater. The total cost assessment was calculated based on annualized investment and operational cost. In order to treat 10 m3 leather industry wastewater, the total cost was calculated as 1.01 USD. The revenue coming from the recoveries of merit materials was 88 USD during the treatment of the 10 m3 leather industry.