Study on Optimal Controlling Strategy of Backwashing Process in Biological Aerated Filter

Abstract

Basing on comprehensive analysis of the existing backwashing modes of Biological Aerated Filter (BAF), air and water combined backwashing was taken as the most efficient and economic mode for BAF backwashing in this study to ensure operating stability and backwashing effect. Then the relevant parameters, involved in air flushing, air and water combined washing and water rinsing, were optimized reasonably. In this paper, the optimal backwashing control strategy was recommended as follows: air backwashing 3 minutes with air backwashing intensity of 10 L/m2·s,secondly, air and water combined backwashing 3 minutes with both air and water backwashing intensity of 10 L/m2·s,at last,water rinsing for 9 minutes with water rinsing intensity of 10 L/m2·s. To discuss the influence of backwashing process on treatment efficiency of BAF, the changes of headloss and contaminants concentration of BAF before and after backwashing was also investigated in this study. The experimental results revealed that under the optimal backwashing control strategy the water flux could be recovered soon after backwashing. Although the contaminants concentration in initial filtrated water increased slightly, the treatment efficiency of BAF reactors could be back to normal in 2 hours.