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UDC 628.161.3

Getmantsev S. V., Sychev A. V., Getmantsev V. S.

Prospects of coagulation water treatment

Summary

Despite the significant progress and increasing popularity of membrane water treatment methods chemical treatment keeps hol­ding tightly its position. One of the most important characteristics of coagulants based on polyaluminium chloride is the basicity. The basicity, all other conditions being equal, determines the dealkylation rate and pH of water subject to coagulation. The value of pH obtained after coagulant hydrolysis, in its turn, determines the zeta potential of colloids present in water and kinetic persistence of the colloid system. During coagulation each type of colloid water pollutants has corresponding optimal pH value. The development of the technology of polyaluminium chloride production from high-purity metallic aluminium by «Aurat» JSC resulted in market launch of EPOKHA™ coagulant trademark with 40–83% basicity. The use of EPOKHA™ provides for choosing an optimal modification of polyaluminium chloride for every customer and every climatic season. Another new product manufactured by «Aurat» OJSC under GranEKO™ trademark is crystalline aluminium chlorhydrate with 65–83% basicity. The concentration of active matter in such product is up to 50% as Al₂O₃. High basicity provides for using GranEKO™ for the clarification of water with low alkaline reserve eliminating the use of alkalizing agents. An important trend in developing chemical water treatment means is the development of composite chemicals combining inorganic coagulant and organic polyelectrolyte. New composite chemicals of ERCHV™ series present a combination of coagulant based on aluminium salt, polydiallyldimethylammonium chloride and modifying additives that provide for the synergetic effect and storage stability. The variety of characteristics of water subject to treatment and applied process flow schemes require an integrated approach to the problem of pH correction during coagulation by using coagulant with higher or lower basicity and changing the injection point.

Key words

coagulation , residual aluminium , aluminium sulphate , aluminium polyoxychloride , chemical water treatment methods , basicity