Intimately Coupling Photocatalytic Optical Fibers and Biofilm for Rapid and Sustainable Degradation of 4-Chlorophenol

Abstract The need for wastewater treatment is progressively rising as the release of copious amounts of industrial wastewater is increasing. Likewise, there is an urgent requirement for renewable energy sources because of the growing energy demand and depletion of fossil fuels. The use of microalgae to convert toxic phenolic wastewater to lipid-enriched biofuel has recently been proposed. Here, we report a new strategy for coupling N-doped TiO2-coated photocatalytic optical fibers and a microalgal biofilm to degrade 4-chlorophenol (4-CP) and produce biomass. In the combined photocatalysis and biodegradation system, the photocatalytic products were directly biodegraded by the heterotroph-enriched (Salinarimonas and Pseudomonas) biofilm, promoting biomass production; O2 produced by the phototrophs (Scenedesmus obliquus) promoted the generation of hydroxyl free radicals using N-doped TiO2. Thus, the combined photocatalysis and biodegradation system rapidly and sustainably degraded 4-CP while maintaining the growth of the microalgal biomass. The 4-CP removal, dechlorination, and biofilm growth rates reached ~78 µM/h, ~41 µM/h, and 1.8 g/h/m2, respectively. Overall, we present a useful synergy between an optical catalyst and a bioreactor that has implications for both wastewater remediation and sustainable microalgal biomass production.