Color and suspended solid removal with a novel coagulation technology

Abstract

A novel coagulation technology using atomized molten slag with ferrous sulfate has been developed to treat a turbid and colored water or wastewater. The atomized molten slag is produced by atomizing the molten slag from the steel-making process. The atomized molten slag has magnetic iron oxide in its constituent molecules so that it is magnetized. In this novel coagulation technology, the atomized molten slag acts as nuclei for coagulation process and weighting agent for the resultant floc. In this study, this new coagulation technology was compared with metal hydroxide flocs such as FeCl3 and PAC in treating textile wastewater. A batch settling test was conducted to investigate the settling characteristic of sludge formed with the atomized molten slag. The settling velocity of sludge formed with the atomized molten slag is almost ten times greater than that of sludge formed with FeCl3 or PAC. The coagulation using the atomized molten slag showed a higher removal rate of color, suspended solid, TOC, COD, TKN and T-P. The atomized molten slag is capable of adsorbing organic substance, ammonia and phosphate. This characteristic leads to higher removal rate than FeCl3 or PAC. The gel permeation chromatography of the wastewater treated using the atomized molten slag illustrated that this novel coagulation technology is more efficient in removing the particles with low molecular weight. The removal rates of color, suspended solid, COD, TOC, ammonia and phosphorous increase with increasing amount of atomized molten slag addition. Even though the atomized molten slag was overdosed, restabilization of particles was not encountered.