Chloramine and copper sulfate as control agents of planktonic larvae of Chironomus luridus in water supply systems

The latest approach to control of midge larvae in drinking-water supplies i s suppression of the planktonic Ist-stage larvae, by using 2 disinfectants, chloramine and copper sulfate. The median lethal concentration for 24-h ex posure of the Ist-stage larvae of Chironomus luridus to chloramine and copp er sulfate individually was 0.51 and 0.38 mg/liter, respectively. The incre ase of copper sulfate to 0.5 mg of copper per liter to water containing chl oramine (0.5 mg/liter) created a synergistic reaction that resulted in 96% (+/-8% SD) mortality of the planktonic larvae. This treatment may serve as an effective control of Ist-stage larvae in municipal drinking-water suppli es.