Coagulation – one of the most common methods of sewage treatment. Essentially, the method of coagulation is in the interaction of pollutants in waste water with mineral coagulants. As coagulants often using ferric chloride, which is a result of hydrolysis forms a slightly soluble iron hydroxide Fe (OH) 3. During the formation of the hydroxide trapped inorganic and organic impurities to form a loose flakes, which can be easily removed from the treated effluent. The resulting flakes are the size of 0,5-3,0 mm and a density of 1001-1100 g / l have a very large surface area with good sorption activity. In the process of their formation and sedimentation structures include particulate matter (silt, plankton cells, large organisms, plant remains, etc.), colloidal particles and the portion of the ion contaminants that are associated on the surface of these particles. High hydroxide floc settling velocity determines the advantage of ferric chloride to aluminum sulfate. The deposition of sludge with ferric chloride is faster and deeper, in addition, ferric chloride positive effect on the biodegradation of sludge.
The overwhelming amount of ferric chloride produced is used for treatment of industrial and sewage. Consumption of ferric chloride is 30 g per cu. meter of wastewater. Chemical waste water treatment reduces the content of insoluble impurities of up to 95% and soluble up to 25%. During wastewater treatment microorganisms and toxic compounds contained in the water, destroyed by hypochlorite sodium. Sodium hypochlorite can be used for the treatment of waste water containing ammonium salts, phenolic compounds and mercury. The degree of purification reaches 99.9%. As a result of investigations into the effectiveness of Food disinfectant sodium hypochlorite has been rated as the most effective and economical product.