Home – Home – Jornals – Chemistry for Sustainable Development 2020 number 4

Complex coagulants comprise a developing and very promising area for the processes involved in the treatment of natural and waste waters. In spite of somewhat higher cost, complex coagulants are devoid of the disadvantages of many classic coagulants and demonstrate high efficiency in water purification from metals, fats, oil products and suspended matter; they also provide a substantial decrease in the concentrations of dissolved organic substances (chemical oxygen demand). The simplest method of manufacturing complex coagulants is the introduction of an additive composed of the products of hydrolysis of titanium-containing compounds into the classic reagents based on aluminium or iron salts. Soluble titanium salts or titanium dioxide may serve as the source of titanium compounds. The waste waters of dairy industry contain a large amount of dissolved organic substances and emulsified fat, so the purification of these waters is one of the most complicated problems. Trial coagulation treatment of model wastewater containing whey showed a high efficiency of complex titanium-containing reagents. Complex coagulants exceeded traditional reagents in efficiency by 10-15 % as average, and the rate of precipitate filtration was 1.2-1.5 times higher. The sediment had a looser structure, did not clog the pores of the filtering material, and readily gave moisture off. Tests of the best samples of complex reagents with the combined household and industrial waste waters of the dairy processing enterprises of the Moscow Region confirmed their high coagulation characteristics with respect to the most common pollutants, and the acceleration of sludge filtration processes will significantly reduce the capital costs of building local sewage treatment plants. The residual content of titanium ions in water, when using the entire line of modified coagulants, did not exceed the maximum permissible level for fishery water bodies.