performance evaluation of combined process of powdered activated carbon-activated sludge (pact) in textile dye removal

introduction: the powdered activated carbon treatment (pact) has been proposed as an alternative in wastewater treatment and wastewater biomass protection against toxic substances. this study aims to evaluate pact performance in treating dyes, acid orange, and remazol brilliant reactive blue. methods: this empirical- applied research was carried out in pilot scale in which different dye removal systems were tested: activated sludge, pac, and the combined activated carbon–biomass system. the degradability of selected dyes was evaluated through zahn-wellens method. also, tests continued by adding different concentrations of powdered activated carbon and its effect on activated sludge in different operating conditions was investigated. american dye manufacture institute (admi) method was utilized for determination of dye removal in samples. results: results revealed that dye removal in combined carbon–biomass system was faster and more efficient than activated sludge individually. so, in the wastewater with the dye concentration of 100 ppm, the dye removals through biological process alone were equal to 60% and 12.5 % for acidic and reactive dyes, respectively. the best pac efficiency in activated sludge process was obtained in 1500 mg/l pac concentration. hydraulic retention time (hrt) and the optimum temperature of dyes' removal were determined 28 hours and 30°c, orderly; in these conditions the dye removal efficiency of 98.18 % was obtained. also the dye removal using activated carbon–biomass system was adequately described by combining the kinetic equations. conclusion: pact could be considered as an acceptable and highly efficient method for removal of different dyes in textile industry.