Enigma provides answer to scale problem

Carbonate-rich effluent from textile processing had been causing problems at Kedgwick's plant in Yorkshire, but scale formation is now being controlled by an electronic system

Kedgwick of Yorkshire is a denim conditioner for several makers of denim clothes. Conditioning involves stonewashing, dyeing and applying finishes to the fabric. The industrial processes almost all involve water and on entering the site the water is first treated in a softening plant. This helps to avoid scaling but problems then arise with the effluent that is produced.

The effluent is heavily contaminated with blue dye and pumice stone solids. At Kedgwick this effluent is chemically treated with lime and other compounds before it is passed to the on-site effluent treatment plant. This separates the blue dye from the wastewater. Because it contains large amounts of calcium hydroxide and carbonate the effluent can cause considerable amounts of fouling and scaling. The formation of hard scale was constricting pipework, scaling up pump impellers and the filter cloths of the effluent sludge filter press. Alban Timmons, chief engineer at Kedgwick said: “The problem had been dealt with in the past by jet cleaning of the pipes, manual descaling of the pumps two or three times a year – with a hammer and chisel – and regular replacement of the filter cloths.” Environmental Treatment Concepts (ETC) has now supplied Kedgwick with Enigma anti-scaling systems. The effluent composition and output varies widely throughout the year so it was difficult to assess the performance of the systems when initially installed. Timmons said: “Before we fitted the Enigma equipment we inserted a probe into the effluent pipework and it was left to scale up.” Scale build-up showed a fairly random pattern to begin with. But after about a month the hard scale on the cloths of the filter press began to come off in such quantities that it blocked up the drains. Timmons added: “Before the filter cloths were literally stiff as a board and when replaced they had to be cut off. But now they retain their flexibility and some permeability too.” Scaling has been much reduced, with only 3-4mm of scale forming on the pump impellers after a few months, whereas before the pumps could become solid with scale. Pipe scale used to reach 40-50mm/yr but this has been cut to 10-15mm/yr.

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