Biological treatment of a bagasse-based soda bleach plant effluent with coriolus versicolor

The effect of rainbow fungus (Coriolus versicolor) on the properties of paper mill bleaching effluent containing chlorinated compounds was investigated. Initially, the independent effect of operating variables including time, temperature, pH, and biomass on color reduction were investigated keeping constant the other variables in the optimum growth conditions of fungi given in literature. The highest color reductions were observed at the treatment time of 6 days (58%), pH of 3 (48%), biomass dose of 9 g/l (59%) and temperature of 35°C (48%) respectively. To study the interactive effect of variables on the color reduction of effluent, and to find the best treatment levels leading to the highest color reduction, two optimum levels of each treatment were selected and tested. It was observed that rainbow fungus had the highest effect on color reduction (66%) in the temperature, treatment time, biomass dose, and pH of 35°C, 6 days, 9 g/l, and 3 respectively. In this condition, COD and BOD of effluent were decreased by 45% and 53%, respectively. It was found that Coriolus versicolor efficiently reduced the various poisonous compounds of chlorophenols, chloroguaiacols, and chlorocatechols present in Pars paper mill bleaching plant effluent to the level less than their lethal concentration (96LC50) in most cases. Globally, it can be concluded that rainbow fungus can efficiently reduce the undesirable physico-chemical properties of bleaching effluent of bagasse soda pulp.