Treatment of wool scouring effluent using anaerobic biological and chemical flocculation

Abstract

The most widely used treatment of wool scouring effluent (WSE) in Australia is lagooning (anaerobic and aerobic). As the pressure to devise a more environmentally acceptable treatment method increases there is a need to study alternative, efficient biological treatment systems for WSE. In this study, laboratory and pilot-scale anaerobic biological and chemical flocculation treatment processes were investigated for removing the pollutants (mainly wool grease) from WSE. Anaerobic biological treatment utilises the natural microbial flora to destabilise and bioflocculate the WSE resulting in the settling of wool grease from the bulk liquid. Batch trials showed a grease reduction by anaerobic bioflocculation of between 30% (pilot scale) and 50% (laboratory scale) over 8 days. However, the destabilisation of the wool grease emulsion after only 2–3 days resulted in a total grease reduction of >80% after addition of a polymeric flocculant. A laboratory anaerobic bioflocculation-chemical flocculation process gave promising results by removing >90% grease at hydraulic retention times of 1–2 days. In the pilot-scale the same process resulted in up to 80% grease removal efficiency. The results of this study indicate that anaerobic biological and chemical treatment of WSE is a promising alternative treatment system compared to other chemical or natural (lagooning) treatment systems. Our approach suggests adding a flocculant to aid the separation of biologically coagulated grease from the bulk liquid. A final low-level aerobic polishing step will be necessary to meet effluent disposal guidelines