Respirometric Evaluation of Toxicity of 2,4-Dichlorophenol Towards Activated Sludge and the Ability of Biomass Acclimation

In the present research, both direct and co-metabolic biodegradation of 2,4-dichlorophenol by mixed activated sludge cultures are investigated by performing respirometric experiments. Firstly, the biomass inhibition due to the toxic pollutant is studied by performing a respirometric toxicity detection experiment. A lag phase for the activity of the biomass showed up because of 2,4-dichlorophenol. The length of the lag phase increased by increasing the concentration of 2,4-dichlorophenol. At higher concentrations, the micro-organisms required more adaption time to the presence of the toxic pollutant. Remarkably, the biomass restored its activity partially. Furthermore, respirometric experiments are performed for several days to investigate biomass acclimation towards the repeated addition of 2,4-dichlorophenol. A significant decrease of the reaction time needed was obtained by biomass acclimation. Immediately after the second addition, an increase of the biomass activity combined with both COD and 2,4-dichlorophenol degradation were observed. The biomass was able to adapt and even to degrade the toxic pollutant. At the second addition, this acclimation period was not necessary.