Use of submerged microfiltration membranes for glass industry wastewater reclamation: pilot-scale testing and membrane cleaning

Pilot-scale microfiltration (MF) tests were carried out to investigate the feasibility of submerged MF systems for the reclamation and reuse of glass industry wastewater. To compare the effect of membrane modular types on flux, plate and tubular modules were immersed in a single reactor simultaneously and their performances were evaluated in terms of water quality and membrane permeability. The quality of treated water (membrane permeate) met the required water reuse standards with regard to turbidity and conductivity. When continuous and intermittent MF operations were conducted at a constant flux mode, the effectiveness of air scouring in controlling fouling was influenced by the module geometry and operating conditions. The plate module gave a better performance because air bubbles entered its feed side while dislodging the accumulated particles. To clean the fouled membranes, various methods using different chemicals such as acidic, caustic, hypochlorite, and chelating agents were compared in conjunction with or without ultrasound. It was found that sonication in a caustic solution achieved maximal flux recovery of more than 95%. This approach was further optimized to reduce the volume of the cleaning solution and the time for chemical rinsing. Based on cost analyses, it was demonstrated that MF systems for wastewater reclamation would have a reasonable payback time on investment should the current system be replaced by the proposed system.