Thickening activated sludge from effluent treatment plants - by dense media sedimentation in the presence of heavy particles

摘要

The concn. of sludge, discharged from a biological effluent purifin. plant is increased by allowing the flocs of such sludge to settle in a reservoir in the presence of heavy particles introduced into the liq., then supplying the settled material to =1 hydro-cyclone in which the sludge flocs are sepd. from the heavy particles which are recycled to the reservoir. System provides a simple technique for thickening sludges which settle only with difficulty and/or very slowly, enabling a concentrate to be obtd. suitable for e.g. centrifuging. The heavy particles pref. have a high specific gravity relative to the sludge flocs and a particle size of 10-100 mu, and may consist of magnetite, ferrosilicon, suitable types of sand or loess. The concn. of heavy particles used to entrain the sludge is pref. 25 g/1.