Pergamon PII: S0043-1354(96)00241-2 War. Res. Vol. 31, No. 1, pp. 170-178, 1997 Copyright © 1996Elsevier Science Ltd Printed in Great Britain.All rights reserved 0043-1354/97$17.00+ 0.00 TREATMENT OF WOOL SCOURING EFFLUENT USING ANAEROBIC BIOLOGICAL AND CHEMICAL FLOCCULATION T. I. MERCZ* and R. CORD-RUWISCH School of Biological and Environmental Sciences, Murdoch University, Murdoch, Western Australia 6150, Australia (First received January 1996; accepted in revised form July 1996) 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, efficientbiological 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 bioflocculatethe 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 tiocculant. 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 biologicaland chemicaltreatment of WSE is a promising alternative treatment systemcompared 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 Copyright © 1996 Elsevier Science Ltd Key words--anaerobic, bioflocculation, grease, wool scouring, wastewater, flocculation INTRODUCTION Wool scouring effluent (WSE) is derived from the washing of greasy wool in the presence of hot water and detergents. It is a highly polluting waste, with a BOD of up to 40,000 mg/L (McLachlan et al., 1980). The wastewater stream consists of wool scouring strongflow and more dilute rinsewater, typically made up of 3000-20,000 mg/L of wool grease (lanolin) in stable emulsion with 7000-16,000 mg/L of suint salts, and 10,000-30,000mg/L of dirt. Because of the extremely high organic load (60,000-120,000mg/L COD), traditional aerobic treatment (activated sludge) cannot be considered as a treatment option. It is considered not feasible to biologically degrade (oxidise to CO2) the main pollutants in WSE (wool grease). WSE is very difficult to degrade anaerobically, with very long residence times of > 30 days required (Issaac and Cord-Ruwisch, 1991). The spontaneous development of bacteria in WSE results in some destabilisation of WSE over time. This has been found for aerobic (Christoe et al., 1978) and *Author to whom all correspondence should be addressed [Fax: 61-9-310-7084; email: mercz@possum.murdoch. edu.au]. anaerobic conditions (Lapsirikul et al., 1994a, b). Therefore, this "natural" destabilisation of WSE can be exploited and included in future processing. Currently, the most widely practised treatment of WSE in Australia is lagooning, a system which is coming under increasing scrutiny due to the potential hazards to the environment, particularly when situated within urban areas. The current pressure for an acceptable treatment system due to stricter government legislature of wastewater disposal, demands further testing of the feasibility of other treatment methods for WSE. Other methods of treating WSE which have been investigated include aerobic and anaerobic biological treatment (Lund, 1971; Cail et al., 1986; Ollermann et al., 1992; Lapsirikul et al., 1994b), chemical flocculation (Christoe, 1977; McLachlan et al., 1980), physico-chemical (McCracken and Chaiken, 1978; Ang and Himawan, 1994), membrane separation (Bilstad et al., 1994) and biological-chemical systems (Christoe et al., 1978). Most of these treatment methods have yet to be sufficiently efficient or economical to be implemented industrially. Previous studies have shown that the main mechanism of grease removal from WSE under anaerobic biological treatment is grease biofloccula- 170