Pollution control and by-product recovery in the New Zealand wool-scouring industry

Wool-scouring in New Zealand (N.Z.) is a conventional aqueous process. Such a process results in the production of a highly-polluting aqueous effluent. The population equivalent of a wool-scour which processes 1200 kilograms per hour of greasy wool and which operates continuously is about 10,000. The aqueous effluent which is produced by N.Z. wool-scouring is both difficult and costly to treat. The major pollutants in wool-scouring liquor are grease, dirt and suint. Wool grease can be recovered economically by use of centrifuges. However, not all of the wool grease can be recovered by this method. Suint, the water-soluble component of the fleece, contains potassium, and would have as a fertilizer. Recovery of suint is not economically feasible. The methods of treating wool-scouring effluent are reviewed. Some notable advances in wool-scouring technology have been made by N.Z. research organizations. The Wool Research Organization of N.Z. (W.R.O.N.Z.) have developed a scouring system which incorporates primary treatment. The Department of Scientific and Industrial Research (D.S.I.R.) have developed a secondary treatment process which recovers nearly all of the wool grease. The author was employed by W.R.O.N.Z., to assist with their programme of research and development on treatment of wool-scouring liquors. As part of this work, small-scale self-desludging centrifuges and an ultrafiltration pilot plant were tested. It was found that one of the small-scale centrifuges offered some advantages (and disadvantages) over the jet-discharge centrifuges which are usually used to recover wool grease on scouring liquor. Ultrafiltration was found to be a promising method of treating wool-scouring effluent. Ultrafiltration produces a sludge which contains grease and dirt, and a solution which contains suint. Sludge dewatering is a problem which requires solution. There is no "best method" of treating wool-scouring effluent. A range of treatments will be required, as effluent discharge requirements may be different for each wool-scour.