Decreasing the Level of Heavy Metals by Aerobic Treatment of Tannery Wastewater

Hussein I. Abdel-Shafy1, Werner Hegemann2, Harm Schenck2, and Andreas Wilke3

1 Water Research and Pollution Control Department, National Research Centre, Dokki, Cairo, Egypt
2 F.G. Siedlungswasserwirtschaft, Technische Universität Berlin, Berlin, Germany
3 F.G. Bioverfahrenstechnik, Technische Universität Berlin, Berlin, Germany

Corresponding author: Prof. Hussein I. Abdel-Shafy
    Water Research and Pollution Control Department
    National Research Centre
    Tahreer Street
    Dokki, Cairo, Egypt
    Telephone: +2012-4018017
    Fax number: +202-4029538
    E-mail address: husseinshafy@yahoo.com

Key words:
Tannery wastewater, heavy metals, aerobic treatment, adsorption, sludge

CEJOEM 2002, Vol.8. No.4.: 298–309

Abstract:
Tanning industry is one of the major consumers of water that discharge large amounts of highly polluting wastewater to the environment. Its treatment is, therefore, vital for the protection of the environment. The main problems encountered in a tannery are the strong variation of the flow, load and the high concentration of main pollutants. The biological systems cannot be applied in the same way as in the case of municipal effluents, since the main pollutants negatively affect the action of microorganisms. In the present study, the efficiency of an aerobic process for the treatment of tannery wastewater as well as the level of heavy metals throughout this process were investigated. The level of chromium in the produced sludge and the treated wastewater was evaluated. The adsorption isotherm of the “free metal sludge” for chromium was also studied. The study was carried out in a continuously controlled pilot plant system. The results obtained revealed that the aerobic treatment improved the chemical oxygen demands (COD) as organic load of the studied wastewater. The heavy metals were concentrated mostly in the sludge. Chromium was eliminated in the wastewater by 46.3%. The levels of the other metals were also reduced with a range of elimination from 19% for Zn to 58.3% for Mn. Nevertheless, the concentrations of Cr both in treated wastewater and sludge exceeded the permissible level. The Cr adsorption by sludge followed the Freundlich’s equation. It was, therefore, recommended that further treatment is required to decrease the Cr to the permissible level.

Received:  10 December 2002
Accepted:  28 March 2003
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