Anaerobic bioflocculation of wool scouring effluent: the influence of non-ionic surfactant on efficiency

Abstract

Wool scouring effluent (WSE) contains high concentrations of wool grease emulsified by non-ionic surfactants (nonylphenol polyethoxylates – NPEO). The short-term treatment (1-7 days) of this effluent with anaerobic bacteria resulted in partial grease flocculation. However the efficiency of this process varied largely (30% to 80%) with the source of wool scouring effluent used. The concentration of free surfactant, rather than total surfactant, was found to be the likely reason for the variation in efficiency. In order to elucidate the mechanisms of anaerobic biological flocculation a detailed surfactant analysis was performed. This revealed that anaerobic microbes (taken from sludge of a municipal wastewater treatment plant) had an ability to partially degrade NPEO by shortening the hydrophilic ethoxylate chain causing coagulation and subsequent flocculation of wool grease from the liquor.