A Study on the Behavior Evaluation and Control of Midge Larvae in the Filtration Process

Recently, midge larvae, which are indicators of aquatic environmental pollution, have been detected in tap water some areas, resulting controversy. Therefore, the objective this study is to analyze behavioural features larvae sand, GAC (granular activated carbon) and GAC/sand processes, mainly operated domestic purification plants, suggest effective operating methods for larval control. In study, a pilot-scale square column (W300×L300×H3500~5000 mm) was used filtration experiment with filter height 2.5 m as well field. The be treated sand filtered from plant G, Han River were injected periodically an estimated 40 50 days. As result, no during first five operational days 14 case GAC/sand. However, after backwashing, 9th day operation GAC, 15th laying under detection delayed by approximately 6 compared alone. Following examination distribution relation carbon layer operation, it found that distributed on 17% upper layer, 7% middle 19% lower 0.2% collection device. necessary shorten backwashing cycle initial stage introduction increase rate expansion quickly flush out larvae. results also confirmed when backwash speed 0.57 m/min or more, 30% rejection increased twice washing 0.45 m/min. Consequently, method functioning process control, filtration, difficult expand media, rinsing time, discard increasing shortening cycle.