TECHNOLOGICAL CHARACTERISTICS OF SEDIMENT AND FLOTATION SLUDGE FORMED DURING WASTEWATER TREATMENT OF HEAVY METALS

Abstract

Heavy metals, which are contained in the wastewater of industrial enterprises, represent a significant danger to the environment. They enter the hydro-ecological reservoir in two ways: with untreated / or insufficiently treated wastewater or migrate into water and soil from sediments obtained in the process of water treatment during storage. Significant environmental damage is exacerbated by the fact that heavy metals pollute reservoirs, which are sources of water supply. The only practical way to dispose of industrial wastewater sludge is its warehousing. Special landfills are needed for the burial of such sediments, which would exclude the release of heavy metal ions into the environment. However, due to the lack of such operating landfills, enterprises are forced to store sludge at their production sites. Storage of heavy metal deposits in the open space can lead to their gradual leaching and pollution of surface and underground waters. To solve this problem, two directions are used: processing of accumulated sediments of heavy metals with their further disposal and processing of sediments using technologies that eliminate or reduce the leaching of heavy metals. The technological characteristics of hydroxide sediments obtained in the process of purification by the settling method and sludges formed during lotation purification from suspension were studied. Studies have shown that the flotation method in the purification of wastewater from heavy metals has an advantage compared to traditional settling in terms of the characteristics of sludge and sediment – volume, specific resistance and humidity of the solid phase. Productivity of dewatering equipment for sludge is 4–6 times higher than for sludge. The degree of leaching of heavy metals such as copper (II), iron (III), chromium (III) and nickel (II) from the flotation sludge is significantly less than from the sediment obtained by reactive precipitation of heavy metals. The leaching rate of nickel ions is three orders of magnitude higher than that of iron and chromium ions, therefore, it is necessary to take special measures when disposing of such waste. The advantages of using the flotation method are shown, which makes it possible to obtain smaller volumes of solid waste, which are more resistant to leaching of heavy metals, which reduces their environmental hazard during storage and long-term storage.