Long-term evaluation of adsorption capacity in a biological activated carbon fluidized bed reactor system

The adsorption capacity of biofilm coated activated carbon from a biologica l fluidized bed reactor which treated toluene contaminated water was determ ined systematically over an extended period of operation. The adsorption ca pacity of biocoated carbon remained at greater than 70% of initial levels d uring the first two months. After six months of operation, the remaining ca pacity was still approximately 40, 52 and 57% of the initial value for equi librium toluene concentrations of 0.1, 3 and 10 mg/L, respectively. If the adsorption removal mechanism is used to provide a buffer during the transie nt conditions, this remaining capacity may be sufficient without carbon rep lacement. There was no direct relation between the amount of biomass or the thickness of the biofilm on the carbon and the remaining adsorptive capaci ty. The loss of adsorption capacity over an extended period of operation ap pears to result directly from bioactivity, rather than from toluene loading . Bioregeneration of this long-term capacity loss. was not observed with co ntinued operation for 100 days after the toluene feed was stopped and the n utrient and oxygen supplies continued. (C) 1999 Elsevier Science Ltd. All r ights reserved.