Rapid anaerobic bioreduction of 2-chlorophenol from water using biofilms supported on graphene oxide layers

Chlorophenols are recognized as persistent environmental contaminants due to their toxicity and resistance to biodegradation. In particular, 2-chlorophenol (2-CP) is of concern because of its high aqueous solubility and tendency to accumulate in aquatic environments. This study proposed an anaerobic removal approach for 2-CP using a tubular ceramic-supported graphene oxide membrane (TCSGoM) bioreactor, which integrates separation and biological processes in a single operational unit. Anaerobic sludge was inoculated into the TCSGoM bioreactor to establish biofilm growth and was acclimated to 2-CP before evaluation under steady-state conditions with stepwise increases in 2-CP concentration. The system achieved 100% removal at feed concentrations up to 50 mg/L, with performance gradually declining at higher concentrations, reaching 24% removal at the tested maximum concentration of 80 mg/L. The results indicate that, during the start-up phase, initial 2-CP removal is primarily driven by adsorption onto the graphene oxide layer, while sustained removal over time is attributed to biofilm-mediated processes under quasi-steady-state operation. The dominant microbial populations were identified as Comamonas and Cupriavidus , both known for their capacity to degrade chlorinated phenolic compounds. Although high removal efficiencies were achieved, transformation products were not analyzed if any were present, which limits the confirmation of the degradation pathway and the extent of mineralization. The proposed system significantly reduces the acclimation period required for conventional anaerobic reactors and has the potential to reduce or even eliminate the need for post-treatment steps, demonstrating that it is an efficient and sustainable alternative for 2-CP removal compared to conventional methods.