Treatment of a water treatment plant filter washing water using coagulant regenerated from the decanter sludge

Abstract

Due to the high generation of waste in water treatment plants, mainly from sludge generated in decanters and from filter washing water, this study aimed to evaluate the regeneration of sludge coagulant and subsequently its use in the washing water treatment by the processes of coagulation, flocculation and sedimentation. The regeneration of the coagulant was performed through the acidic route using the methodology described by Fulton (1974), varying the time of acidification. The washing water treatment was executed in Jar Test equipment, according to the methodology presented by Di Bernardo, Di Bernardo and Centurione Filho (2002), varying the coagulant concentrations and the coagulation pH. In the regeneration process, the aluminum concentration obtained was statistically equal in all acidification times adopted, showing that aluminum dissociation occurs in the first 10 minutes of the reaction, where an average concentration of 565.31 mgAl/L was obtained. In the washing water treatment, the best operational condition was when using a recovered coagulant dosage of 10 mgAl/L and coagulation pH 7, obtaining a removal >=80% of the solids, aluminum, iron, manganese, turbidity and color apparent, and about 99% of the evaluated faecal contamination indicators.