Developments in new processes for colour removal from effluent

摘要

The majority of colour removal techniques work either by concentrating the colour into sludge or by the partial or complete breakdown of the dye molecule. In principle, decolorisation is achievable using oneor a combination of different methods depending on the wastewater characteristics. Each technique has a specific application as well as distinct advantages and disadvantages and has to be evaluated according to cost, application and performance in relation to the desired goal. With rapid changes in dyes and stricter consent limits, conventional coagulation/flocculation methods alone do not give completely satisfactory treatments, especially with highly soluble reactive dyes. Moreover, large quantities of sludge generation containing all the toxic compounds present in the effluent are likely to increase disposal costs substantially. Low cost bioadsorbents have been extensively investigated for the treatment of waste containing dyes as an alternative to high cost activated carbon. However specificity to remove certain contaminates, slow kinetics, regeneration and flow problems have limited the commercial success of these adsorbents at the industrial scale. Membrane systems provide a means to recover water and other auxiliaries for total treatment or stand-alone processes for scouring or dyebath liquor separation. The major limitations are the economic feasibility because of high costs and the treatment of concentrate streams, which are highly concentrated.