The treatment of wool scouring effluents in Australia, China and India

• Woolmark Company, Australia
• Ministry of Water Resources, China
• Ahmedabad Textile Industries Research Association, India

Wool production is considered to be 'environmentally-friendly', but the treatment of fibre involves scouring, resulting in potentially damaging effluent outputs. Greasy wool contains both natural contaminants (wax, dirt and suint) and pesticide residues. Scouring removes these residues to ensure wool is of high quality, but leaves effluent containing the removed contaminants. In China and India, both important markets for Australian wool, this effluent often results in environmental pollution as the watery effluent is discharged into surrounding areas. Strict environmental guidelines are now in place in all countries, with the viability of China's wool-processing industry under threat. Effluent is usually treated prior to release to recover contaminants, but the levels of effective recovery vary substantially.

This project aimed to improve wool scouring and the treatment of effluents to reduce environmental impacts of the wool processing industry in China and India.

The project teams came to Australia for training in laboratory techniques to analyse wool and liquid effluent samples. Data analysis and results evaluation were also included in the training, as was how to collect samples in wool mills. The teams learnt to compare the characteristics of Chinese and Australian wool, revealing differences in the removal of dirt and of colour after processing.
A major component of the project involved working with 14 mills (four in India, six in China and four in Australia). They represented all segments of the industry from commission scourers, commission combers and vertical mills. The teams carried out process audits at each of the mills. These involved the scouring process itself, contaminant recovery and wastewater treatment. In addition two series of comparative processing trials were carried out, in which the same wool was scoured at each of the participating mills before being made into top at CSIRO. Trials of blended greasy wool were also conducted at each participating mill.

The researchers produced a training manual to standardise procedures and methods of analysis between the collaborators in the three countries. The training of key staff from China and India was a successful transfer of knowledge that is now contributing to standardisation, monitoring, regulation and quality control.
Comparative studies of mills in China, India and Australia using operational and scouring audits, followed by process audits of twelve mills in the three countries, revealed impediments to maximum efficiency and the need to improve through changes in operations. The mill audits demonstrated that, in general, the quality of the scoured wool produced by the mills, especially those in China and India could be substantially improved. This was indicated by the poor processing performance of the scoured wool in terms of fibre wastage and fibre length in the top. In some cases comparatively small modifications to existing systems could have a strong impact on profitability.
The series of comparative scouring trials showed that the removal of wool wax was similar for a range of Australian and Chinese wools. However, the levels of residual dirt were higher on the Chinese wools, which were much more yellow. Generally the scours in China and India performed more poorly than the more modern scours in Australia in terms of resource usage (water and detergent), contaminant recovery (dirt and wool wax) and the extent of fibre entanglement.
The results have demonstrated outstanding prospects for improvements in both scouring and effluent treatment that will significantly reduce the cost of scouring and improve the quality of the scoured product. The efficiency of water usage can be increased and pollution of water courses greatly reduced for the benefit of communities where scours are located.
Many of the mills have changed their modes of operation as a result of the project. Another Chinese mill has scrapped its existing scouring lines and purchased more modern equipment from Australia. Another of the Chinese mills translated the entire ACIAR report into Chinese so that the staff could benefit from the study.
The cornerstone of CSIRO's approach to treating wool scouring effluents is a chemical flocculation process, Sirolan CF. A Sirolan CF pilot plant was operated at mills in Australia, India and China in order to demonstrate the effectiveness and simplicity of the technology under different operating conditions. The process performed well in all the trials. It removed virtually all of the wool wax and dirt from the effluents and more than 90 per cent of the organic load - the remaining organic matter coming from the water-soluble suint salts. As a result of these trials several of the mills have adopted the technology and several more have made enquiries about its installation.