DRAG REDUCTION BY A CHEMICAL ADDITIVE IN SANITARY SEWERS

An experimental setup has been tested for the reduction of drag in san itary sewers using a new chemical called GEM. The study was carried ou t for different sizes (15 cm, 20 cm, and 25 cm diameter) of concrete s ewers. The effect of sewer size and solvent concentration on drag redu ction were investigated, and it was found that appreciable and measura ble drag reduction was obtained at very low chemical concentrations. T he optimum concentration was found to be 20 ppm for the 15 cm and 20 c m diameter sewers, resulting in 30% and 33% drag reduction, respective ly. A maximum drag reduction of 41% corresponding to 30% increase in t he sewer capacity was obtained in the 25 cm diameter sewer at a concen tration of 40 ppm.