Remediation/Treatment

Treatment of unhairing effluents by activated sludge system

  1. Najwa Mlaik1,*,
  2. Mbarka Gouider1,
  3. Jalel Bouzid1,
  4. Lassaad Belbahri2,
  5. Steve Woodward3,
  6. Tahar Mechichi1

Article first published online: 10 SEP 2010

DOI: 10.1002/ep.10484

Issue

Environmental Progress & Sustainable Energy

Environmental Progress & Sustainable Energy

Volume 30, Issue 3, pages 337–346, October 2011

Additional Information

How to Cite

Mlaik, N., Gouider, M., Bouzid, J., Belbahri, L., Woodward, S. and Mechichi, T. (2011), Treatment of unhairing effluents by activated sludge system. Environ. Prog. Sustainable Energy, 30: 337–346. doi: 10.1002/ep.10484

Author Information

  1. 1

    Ecole Nationale d'Ingénieurs de Sfax ENIS, Laboratoire Eau, Energie et Environnement, Route de Soukra BP W 3038, Sfax, Tunisia

  2. 2

    Laboratory of Applied Genetics, School of Engineering of Lullier, Jussy, Switzerland

  3. 3

    Department of Plant and Soil Science, University of Aberdeen, Institute of Biological and Environmental Sciences, Aberdeen AB24 3UU, Scotland, United Kingdom

*Ecole Nationale d'Ingénieurs de Sfax ENIS, Laboratoire Eau, Energie et Environnement, Route de Soukra BP W 3038, Sfax, Tunisia

Publication History

  1. Issue published online: 13 SEP 2011
  2. Article first published online: 10 SEP 2010

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Keywords:

  • unhairing effluent;
  • activated sludge system;
  • sulphide oxidation;
  • phytotoxicity;
  • germination index

Abstract

The unhairing step in leather manufacture generates a highly hazardous and alkaline wastewater. This article reports the evaluation of an activated sludge system for the treatment of unhairing wastewater and effluent detoxification, assessed by seed germination tests.

The activated sludge system reactor was fed for 112 days with diluted unhairing effluent; the operation strategy included increasing the organic loading rate (OLR) from 0.7 to 1.6 g chemical oxygen demand (COD) L−1 d−1. COD and suspended solids (SS) removal efficiencies were up to 85 and 80%, respectively, for an OLR lower than 1.4 g COD L−1 d−1.

Sulphide removal efficiency was ∼90%, as sulphide was oxidized to other species such as sulphate. The biological oxidation of thiosulphates into tetrathionates was also investigated.

The effect of untreated and treated unhairing wastewater on seed germination of maize, sorghum, and wheat was examined. Treatment decreased the phytotoxicity of the wastewater. Indeed, germination was inhibited when effluent dilution was lower than 90% of untreated wastewater, whereas a positive effect of treated wastewater was noticed.

Phytotoxicity assays showed that biological treatment of unhairing wastewater contributed to a decrease in toxicity of the effluent. © 2010 American Institute of Chemical Engineers Environ Prog, 2011

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