Effect of operating parameters on removal of boron from wastewater containing high boron concentration by vacuum assisted air gap membrane distillation

In the present study, three different real wastewaters (containing high boron concentration between 2500–6200 mg/lt) were treated using the vacuum assisted air gap membrane distillation (VA-AGMD) system through the use of polypropylene with a pore size of 0.20 μm (PP 0.20), polypropylene with a pore size of 0.45 μm (PP 0.45), polytetrafluoroethylene with a pore size 0.20 μm (PTFE 0.20) and polytetrafluoroethylene with a pore size 0.45 μm (PTFE 0.45). The impact of variable parameters including vacuum pressure, boron concentration, membrane material and membrane pore size on the VA-AGMD system performance were examined. Firstly, experiments were conducted with saline water (%1 (w/v)) to stabilize the VA-AGMD. Experiments were then carried out with three different real wastewaters in the VA-AGMD system. To discover the impact of vacuum pressure on the VA-AGMD system, four different vacuum pressures (0.02, 0.04, 0.06 and 0.08 bar) were studied. Furthermore, to test the effect of both pore size and membrane material on the VA-AGMD system performance, PP 0.20, PP 0.45, PTFE 0.20 and PTFE 0.45 membranes were used. The results demonstrate that boron was removed above 99 % in all conditions for all wastewaters. As a result, when boron concentrations at feed wastewater and vacuum pressure were increased, permeate water fluxes increased for nearly all of the conditions. It was concluded that permeate water flux was enhanced with increasing pore size and the highest permeate water flux was obtained by using PP membranes for all wastewaters.