Energy management in submerged microfiltration systems by optimum control of aeration

Abstract

Although submerged microfiltration is widely used as a pretreatment process for surface water treatment and RO desalination, its high energy consumption is a major drawback compared to conventional pretreatment. Especially, aeration during filtration is an energy-intensive step in most submerged membrane systems, which explains more than 30% of total energy consumption. Nevertheless, it is difficult to reduce aeration since it may increase the rate of membrane fouling. This study focused on the development of energy management technology for submerged microfiltration systems by optimizing aeration rate. Fundamental principle underlying this technology is that the mode and intensity of aeration are automatically adjusted from the feedback of information on foulant concentration and fouling rate. A series of equations to control aeration was derived based on feed water quality and fouling index. Although this technique was originally developed for surface water treatment, same technique may be used for seawater filtration. Experiments were carried out in a pilot scale with the capacity of a 50 m 3/day plant using submerged microfilters (Cleanfil-S20, Kolon, Korea). A control algorithm was designed and tested on the pilot plant for optimizing aeration rate. Based on the experimental results, it is likely that the new aeration technique is more energy-efficient than other existing aeration methods (continuous or periodic aerations). Using this control algorithm, the energy consumption was reduced and the transmembrane pressure was maintained stable regardless of feed water turbidity.