The mechanism of coagulation with highly alkaline polyaluminum chlorides is well understood, but there is a lack of information on the effect of the presence of iron in these coagulants on the efficiency of purifying water with increased contents of natural organic matters among which humic substances are precursors of disinfection by-products. The dissolved forms of organic substances are the most problematic with regard to water treatment because major concern is the formation of disinfection by products resulting from reactions between dissolved organic matter fractions and disinfectants. The aim of this study was to evaluate the effectiveness of precursors of disinfection by-products removal using highly alkaline polyaluminium chlorides that had different alkalinity and iron content. In the water after the coagulation process a value of SUVA254 was calculated because this indicator correlates well with dissolved organic matter reactivity and disinfection by-products. The analysis of the obtained results showed that the effectiveness of dissolved organic matter removal was determined by the formation of colored iron-organic complexes.
Aluminium is one of the environmental factors that may have an impact on Alzheimer's and Parkinson's disease. Some epidemiological studies show a relationship between the concentration of aluminium in drinking water and the incidence of Alzheimer's disease. The article presents and discusses the results of research on the effect of the type and dose of non-prehydrolyzed aluminium coagulants on the concentration of residual aluminium in water intended for human consumption. Aluminium sulphate (VI) and sodium aluminate were tested as coagulants. Analysis of the obtained test results showed that lower concentrations of residual aluminium were found after coagulation with aluminium sulphate (VI), which is hydrolyzed acidally, lowering the pH of the water in the range of 7.47 to 7.12 providing good conditions for the formation of Al(OH)3. A less useful coagulant due to the concentration of residual aluminium was sodium aluminate, which undergoes basic hydrolysis creating conditions for the transition of Al(OH)3 into soluble Al(OH).
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