In many cases, components of industrial process wastewaters are non-readily biodegradable, but can be effectively removed from the wastewaters by means of adsorption processes to activated carbon (AC). However, the loading capacity of an AC filter is often low and the endurance of the adsorber packing is short. The loaded AC must eventually be thermally regenerated and/or deposited. The costs for spent AC regeneration and disposal are significant. Biological in situ regeneration of AC to prolong the endurance of the adsorber and to reduce operating expenses appears to be an interesting option. Combination of AC adsorption and biodegradation may provide additional advantages. For instance, the bulk liquid concentration of critical wastewater components is decreased by adsorption so that inhibitory effects on the bacteria are damped or may even disappear. Volatile organics may be kept available to the bacteria instead of being stripped. To investigate the potentials of this process concept, an experimental loop reactor system was designed consisting of an AC packing, and a membrane mass transfer module. The reactor system was operated as a Sequencing Batch Reactor (SBR). Mixtures of benzene/2-chlorophenol and trichloroethene/phenol were used to make up model wastewaters. The hydrodynamic conditions and the bio-regeneration strategy was systematically varied during the investigations. The results obtained show that the endurance of the AC can be prolonged by at least five times value of a merely physically operated adsorber. Benzene/2-chlorophenol could be biodegraded by almost 95 per cent during a 24 hour cycle. Of the trichloroethene added per cycle about 5 per cent was degraded. Consecutive process operation (loading of the AC followed by bio-regeneration) led to higher degradation rates than simultaneous operation (loading and regeneration at the same time).

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