Biological treatment and recycling of textile processing effluents
In the present work, a mixed culture of Pseudomonas spp. capable of decolourising a range of selected textile dyes was isolated and used to develop a continuous culture system for the treatment of textile dye effluents. The bioprocess was optimised using biomass growth supports. The presence of a carbon source such as soluble wheat starch (0.2 % w/v) in dye solution media and effluent samples enhanced decolourisation. A polymer support (polyurethane foam) was used for immobilisation of "the bacteria in the laboratory-scale bioreactor, and helped create an integrated anaerobic I aerobic condition within the foam matrix and promote degradation of azo dyes and organic compounds. The system showed high levels of decolourisation up to 98 0/0 over 12 days of continuous operation. However, toxicity levels of dye samples increased up to 65 % after anaerobic biotreatment, due to the formation of toxic aromatic amines. The continuous culture bioprocess was also combined with membrane filtration technology to improve effluent treatment. Oecolourised, filtered effluents showed great reduction in COO, BODs and toxicity levels, and were found suitable for re-use in ~yeing processes. Dyed cotton fabrics did not show any significant difference with those dyed using normal supply water. These studies show great potential for improvement of an existing industrial effluent treatment plant through the use of biomass growth supports and the combination of membrane technology. Considerable savings are foreseeable through the implementation of the process, provided effluent recycling within the textile factory is successful.