The effect of a quinone-based redox mediator on the decolourisation of textile wastewaters: a comparative study between mesophilic (30°C) and thermophilic (55°C) anaerobic treatments by granular sludge

摘要

A comparative study between mesophilic (30°C) and thermophilic (55°C) anaerobic treatments by granular sludge was performed on the decolourisation of a reactive textile wastewater, both in presence and absence of the redox mediator anthraquinone-2-sulfonate (AQS). The investigations evidenced the advantage of colour removal at 55°C compared with 30°C. In the presence of anthraquinone-2,6-disulfonate (AQDS), the generation of the hydroquinone form AH_2QDS, i.e. the reduced form of AQDS, was greatly accelerated at 55°C compared in comparison with 30°C. Furthermore, no lag-phase was observed at 55°C. Based on the present results we postulate that the production/transfer of reducing equivalents is the process rate-limiting step, which was accelerated by the temperature increase. It is conclusively stated that 55°C is a much better temperature for colour removal than 30°C, which on the one hand can be attributed to the faster production/transfer of reducing equivalents, but also due to the decrease of activation energy requirements.