APPLICATION OF FORWARD OSMOSIS PROCESS FOR SECONDARY TREATED EFFLUENT OF PULP AND PAPER INDUSTRY

Abstract

Wastewater treatment via suitable routes is necessary to protect the environment and fill the freshwater shortage. An osmotic pressure-driven membrane separation process of forward osmosis (FO) has gained attention over conventional approaches as an alternative water treatment process. FO is a membrane separation technique that recovers water from feed solution (FS) across a semipermeable membrane using a concentrated draw solution (DS). The FS could be wastewater, sea/brackish water, or other contaminated water. The FO process has significant advantages as it operates with low hydrodynamic pressure, showing lower membrane fouling propensity. Hence, it helps for saving energy and reducing membrane replacement costs. A commonly used fertilizer such as urea in water can be used as a DS, and after the FO run, diluted DS may use as fertilizer. Thus, it can simultaneously generate freshwater for agricultural purposes from industrial wastewater. FO process using thin-film composite flat sheet membrane has been investigated for various labmade solutions and pulp & paper industrial effluent as feed solutions under varying DSs of 0.25, 0.5, 1, and 2 M urea solutions. Limited FO studies examined the long-term and repetitive runs using the same membrane to access the fouling, water, and solute flux behavior with real industrial wastewater as FS. The long-term experimental results prove the strong influences of DS concentration on specific energy consumption (SEC), fouling behavior, and water flux. Increasing the cross-flow rate from 0.33 to 1 L/min has a minor effect on water flux, but SEC increases significantly from 0.17 ± 0.01 kWh/m3 to 0.50 ± 0.03 kWh/m3. FO runs show that the overall water flux enhances due to higher osmotic pressure difference and lesser membrane fouling at higher DS concentrations using pulp & paper industrial secondary effluent as FS. This study demonstrates that a low-energy FO process can recover water from industrial wastewater while simultaneously producing a diluted fertilizer for fertigation.