Biological activated carbon treatment of industrial wastewater in stirred tank reactors

The industrial effluent under investigation was the simulated aqueous discharge from a carpet printing plant in Northern Ireland, comprising of a ternary solution of acid dyes. This effluent was investigated using the biological activated carbon (BAC) process for colour removal in an aerobic stirred tank reactor configuration. The following systems were experimentally investigated: bacteria immobilised on granular activated carbon (GAC); bacteria immobilised on sand particles; GAC (with no biological activity) and free bacterial cells. The bacterium used in this study was Pseudomonas putida (NCIMB 9776) and the activated carbon was Filtrasorb 400. Ternary dye concentrations were determined by spectrophotometry. Results indicated that BAC system outperformed the combination conventional GAC and biological water treatment processes. For biodegradable anthraquinone dyes, this enhanced colour removal was due to higher dye utilisation rates caused by the increase in substrate concentration at the granule surface found in BAC systems. For non-biodegradable azo dyes, increased biosorption was found in BAC systems compared to conventional immobilised systems.