Journal of
Environmental Chemistry and Ecotoxicology

  • Abbreviation: J. Environ. Chem. Ecotoxicol.
  • Language: English
  • ISSN: 2141-226X
  • DOI: 10.5897/JECE
  • Start Year: 2009
  • Published Articles: 197

Full Length Research Paper

The effect of water hardness on paint wastewater treatment by coagulation-flocculation

I. O. Ntwampe
  • I. O. Ntwampe
  • School of Chemical and Metallurgical Engineering, University of the Witwatersrand, Private Bag X3, Johannesburg, 2050, Republic of South Africa
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L. L. Jewell
  • L. L. Jewell
  • School of Chemical and Metallurgical Engineering, University of the Witwatersrand, Private Bag X3, Johannesburg, 2050, Republic of South Africa
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D. Hildebrandt
  • D. Hildebrandt
  • Centre of Material and Process Synthesis, University of the Witwatersrand, Private Bag X3, Johannesburg, 2050, Republic of South Africa
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D. Glasser
  • D. Glasser
  • Centre of Material and Process Synthesis, University of the Witwatersrand, Private Bag X3, Johannesburg, 2050, Republic of South Africa
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  •  Accepted: 10 January 2013
  •  Published: 31 March 2013

Abstract

 

A 169.2 g of paint was diluted in 1 L potable water. A 200 ml of the sample was poured into six 500 ml glass beakers and dosed with 0.043 M FeCl3, 0.043 M of Al2(SO4)3 or AlCl3, respectively employing varying dosing sequence and varying dosages before and after mixing in a jar test to determine turbidity removal efficiency. Samples were stirred at 250 rpm for 2 min and 100 rpm for 10 min, settled for 1 h after which the pH and turbidity were measured. In a second set of experiments, the samples were dosed with combined 0.043 M FeCl3 and 0.043 M Ca(OH)2 or 0.043 M Mg(OH)2. In a third set of experiments, the samples were dosed with 0.043 M FeCl3-Ca(OH)2 or 0.043 M FeCl3-Mg(OH)2 of synthetic polymers. The results from the first and the second sets of experiments showed that pH correlates with turbidity removal, dosing before or during mixing do not play a significant role in wastewater treatment. There is no correlation between pH and turbidity from the results in the third sets of experiments. It indicates that pH is not a direct indicator of turbidity in the treatment of more alkaline solution.

 

Key words: Paint, dosing, mixing, pH, turbidity, polymer.

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