UTILIZATION OF DRINKING WATER TREATMENT SLURRY TOPRODUCE ALUMINUM COAGULANTS

Abstract

Name: Mahmoud Mohamed Fouad Hussein Title of thesis: Utilization of drinking water treatment slurry to producealuminum coagulants. Degree: (M.Sc.) Master of environmental sciences thesis, department of environmental basic sciences,institute of environmental studies and research, Ain Shams University, 2016. In Egypt, water treatment industry consumes about 365,000 tons of aluminum sulfate asacoagulant and produces more than 100 million tons of semidried sludge per year.The common disposal system of alum sludge in Egypt is to discharge off into natural water bodies. The toxic nature of free and complexed aluminum species to aquatic life, stringent environmental regulations on disposal of alum sludge into water bodies and costs of chemicals used in water treatment process and sludge treatment led to evaluate coagulant recovery and subsequent reuse. The present work aimed at aluminum metal recovery from the sludge obtained from El-Sheikh Zayd water treatment plant (ESZ-WTP) by acidification to produce aluminum coagulants.Sludge from El-Sheikh Zayd lagoons using alum as coagulant was characterized. Sulfuric and hydrochloric acids were selected as the acidic leaching mediums and the effect of six variables were tested which are: acid concentration (N), sludge weight (g), acid / sludge ratio (g/g), mixing speed (RPM), mixing time (min) and temperature (°C)and the process efficiency was evaluated at different operating conditions. Then the optimum conditions were applied to get maximum recoveries for aluminum coagulants which were 94.2 % using sulfuric acid at acid concentration 1.5 N, sludge weight 5 g, mixing speed 60 RPM, temperature 60 °C and mixing time 40 minutes. Moreover, best aluminum recovery using hydrochloric acid was 82.4 % at acid concentration 2.0 N, sludge weight 5 g, mixing speed 80 RPM, temperature 40 °C and mixing time 40 min. a comparison was carried out between metals concentrations for the two recovered coagulants and the commercial one and no significant increase in any metal was obtained. Also waters treated with the recovered coagulants were similar in THMs and turbidity if compared to commercial coagulant.In addition, by applying sequential coagulant recovery THMs was within acceptable limits till the third time coagulant recovery. Keywords: Aluminum sludge, water treatment, aluminum sulfate, aluminum chloride, acidification,aluminum recovery, leachingand extraction.