Mechanisms in anaerobic bioflocculation of wool scouring effluent

Abstract

The emulsified grease in wool scouring effluent (WSE) was demonstrably removed by bioflocculation under anaerobic conditions. The addition of anaerobic bacteria from biogas digestion to WSE resulted in grease reduction of 60–80% from the supernatant. Since no significant net grease (supernatant plus sludge) reduction was observed in this system, the grease emulsion from the liquid phase is simply settled by gravity into the sludge phase. However, sterilized sludge did not cause this effect, indicating that bacterial metabolic activity was responsible for the bioflocculation. It was also found that such microbes can successfully survive and multiply in WSE, as a result, the development of a continuous process is possible. The process required a short gentle mixing period of approx. 15 min enable the the sludge to completely contact with WSE, and a longer settling period of 2–4 days to provide an appropriate time for the microbes to destabilize wool grease emulsion and settle to the sludge phase.