Bioregeneration of granular activated carbon loaded with phenolic compounds: effects of biological and physico-chemical factors

Bioregeneration is a process of restoring the adsorptive capacity of the spent adsorbents through microbial action. In this study, the effects of acclimated biomass concentration, biomass acclimation concentration, dosage of granular activated carbon (GAC) and type of GAC on the bioregeneration efficiency (BE) of GAC loaded with phenol and p-nitrophenol (PNP), respectively, were investigated. The quantification was conducted by monitoring the time courses of adsorbed substrate amount during bioregeneration under the sequential adsorption and biodegradation approach. The mean BEs of phenol- and PNP-loaded GAC were found to be 78 ± 2 and 77 ± 1%, respectively. The results revealed that increasing acclimated biomass concentration and adsorbent dosage did not have an observable effect on the BEs of phenol- and PNP-loaded GAC. Additionally, the BEs were found to be almost the same for the bioregeneration of phenol-loaded GAC using biomass acclimated to 350 and 600 mg/L of phenol, respectively. The BEs of phenol-loaded GAC 830 (thermal-activated) and GAC 1240+ (thermal- and acid-activated) did not show any observable difference, but the BE of PNP-loaded GAC 1240+ was found to be greater than that of PNP-loaded GAC 830 indicating that the improvement of BE of spent GAC through further chemical activation was dependent on the type of adsorbate.