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Dyeing wastewaters and residual size are textile factory waste streams that can be treated anaerobically. For successful anaerobic treatment of dyeing effluents, a co-substrate has to be added because of their low concentration of easily biodegradable compounds. Starch-based size contains easily biodegradable material, but is too concentrated to be treated without difficulties. Although residual size makes up only a small volume, when mixed with the other textile wastewater streams it has a considerable impact on the overall organic load. Many textile dyes can pass through a conventional aerobic treatment plant without being degraded. Anaerobic pre-treatment of the dyeing wastewaters before discharge to the aerobic plant can solve this problem, as many dyestuffs are partly degradable under anaerobic conditions, rendering aerobically degradable products. In this study, the possibility of using waste size as a co-substrate for the anaerobic pre-treatment of dyeing wastewaters was investigated. It was found that waste size was applicable as co-substrate for the decolourisation of the two textile dyeing wastewaters studied. Adding a redox mediator could enhance decolourisation rates for both wastewaters.

In the textile industry, many different processes are used and almost all of them generate wastewater. The effluents resulting from these processes differ greatly in composition, due to differences in processes, used fabrics and machinery. Textile wastewater is usually treated as a mixed stream. For water and chemicals reuse purposes however, it is preferable to keep process streams apart and treat them separately. Characterisation of textile industry effluents is of great importance for the separate treatment of process streams. This literature review provides an overview of what is known about the wastewater of the separate processes, and the methods used for characterisation of these streams.

When aerobic bacteria receive a biodegradable material such as wastewater, then respiration changes from endogenous to exogenous. The reverse occurs when biodegradation is complete. When using respirometry a respirogram is recorded showing those changes in respiration, and for an expert it is not difficult to point the moments at which they occur. The area corresponding to the exogenous respiration phase is a measure of the easily biodegradable fraction of material, also called the short-term BOD or B0D51. That value, in combination with a value for COD, can be used to determine the treatability of wastewater. Respirometry can also be applied on-line, e.g. for on-line monitoring of wastewater. However, automatic detection of the end-point of exogenous respiration is difficult. The first step towards on-line monitoring of wastewater treatability is to make automatic detection of this end-point possible. In this study the use of a neural network for detection of this end-point was investigated. Results are promising; after training the neural network is able to detect the correct end-point in the majority of the studied cases. [ABSTRACT FROM AUTHOR]