Characteristics of organics removal by PACT simultaneous adsorption and biodegradation

The use of powdered activated carbon treatment (PACT), based on simultaneous adsorption and biodegradation, is effective for treating organic toxic pollutants, present in industrial wastewaters. Removal of phenol and aniline from aqueous solutions by biological treatment alone, by adsorption on powdered activated carbon (PAC) alone and by simultaneous adsorption and biodegradation were compared. In the adsorption experiments, Langmuir adsorption isotherms were obtained, from which Q degrees, the limiting adsorption capacities, and b, the constant related to the energy of adsorption, were determined. Q degrees values of phenol and aniline were found to be similar, while the energy-related constant for aniline was five times higher than for phenol. Addition of mineral nutrients, needed for the biological treatment, and inactivated microbial cells increased the limiting adsorption capacities and significantly decreased the energy related constants. In biological treatment alone, kinetic studies showed that aniline was more resistant to biodegradation than phenol. In the simultaneous adsorption and biodegradation process, the PAC presence differently affected the biooxidation of phenol and aniline. While the PAC enhanced the microbial respiration in the phenol bioreactor, it significantly reduced the microbial respiration in the aniline bioreactor. Different organic removal mechanisms are suggested in PACT for phenol and aniline, due to their different energy of adsorption. The respirometric studies are recommended as an adequate tool for prediction of toxic organics removal capabilities from industrial wastewaters by PACT. (C) 1997 Elsevier Science Ltd.