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HE OBJECTIVE of the present study is treatment of industrial wastewater that is artificially contaminated with a combination of soluble salts of Ni, Cu and Mn in the concentration of 10 mg/l each. The treatment is focused on employing chemical coagulants and coagulant aids for the removal and co-precipitation of heavy metals. Variable doses of the chemical coagulants at different pH were examined. The physical and chemical characteristics and the level of Cu, Ni and Mn in the industrial wastewater are given. When Sodium hydroxide was employed at pH 9.5, removal rate reached 97.5, 96.0 and 90.0% for Cu, Ni and Mn, respectively. On the other hand, the use of 50 mg/l ferric chloride in combination with sodium hydroxide at different pH was studied. At pH 12.0, all the studied metals were removed at the rate of 98%. When 70 mg/l alum was employed in combination with NaOH at different pH, results indicated that 100% of Cu, 100% of Ni and 84% of Mn were removed at pH 12.0. Further study was carried out using lime at different doses. At pH 11.0, the removal rate reached over 100% for Cu and Ni each and 93% for Mn. Limestone (CaCO3) at different doses was investigated. Using 1.0 g/1 limestone raised the pH from 2.0 to 5.85 and the removal of Cu, Ni and Mn reached 100, 90.2 and 75.1% respectively. By increasing the CaCO3 dose to 3.0 g/l, more than 100% of Cu and Ni each was achieved while Mn was removed at 90.6%. It was noticed that increasing the limestone dose up to 5.0 g/l did not increase the pH more than 8.0. This can be attributed mainly to the buffering system of limestone. It was concluded that the precipitation of metals is governed by the solubility product. Since all effluent guidelines require an effluent pH between 6 and 9, the use of carbonate treatment is, therefore, recommended because of its buffering capacity value which is around pH 7. Still CaO provides substantial precipitation efficiency and an economic mean of treatment. The disadvantage is the difficulty to control the pH of the liquid waste. However, this problem could be overcome by using acid to control the pH if needed.

Chemical Treatment for Removal of Heavy Metals from Industrial Wastewater