Evaluating the photodegradation of Carbamazepine in a sequential batch photoreactor system: Impacts of effluent organic matter and inorganic ions

Removal of pharmaceutical Carbamazepine (CBZ) compound from municipal wastewater has become an issue from the human health and environmental risks point of view, due to its latent recalcitrance and toxicity properties. This study investigated the photodegradation performance of a sequential batch annular slurry photoreactor (SB-ASP) system for the removal of CBZ compound from secondary municipal wastewater. Two different immobilised TiO2 photocatalysts, namely anatase titanate nanofiber and mesoporous TiO2 impregnated kaolinite catalyst were applied in the SB-ASP system. Various modes of sequential batch reactor (SBR) cycles, presence of effluent organic matter (EOM) and inorganic ions, mainly nitrate and phosphate that could affect the photodegradation performance of the SB-ASP system were evaluated during the removal of CBZ. High performance size exclusion chromatography revealed that the photocatalytic reaction will preferentially compete and attack on high molecular weight EOM prior to the photodegradation of CBZ. The presence of inorganic ions was found to affect the surface fouling of immobilised photocatalysts used to a different extent, without completely retarding their photoactivity. This study also highlighted that the operation of SB-ASP system was useful to enhance the photodegradation of CBZ compound in a semi-continuous operation without constant catalyst replacement. It is foreseeable that the integration of SB-ASP system with biological treatment systems could provide an advanced treatment option for the recycling and reuse of municipal wastewater.

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► Sequential operation using TNC shows 70%, 27% and 11% COD reductions over 3 cycles.
► Higher AMW EOM peak >100 kDa was degraded to smaller AMW peaks of 750 and 1050 Da.
► Preferential attack on high AMW EOM leads to partial oxidation of CBZ.
► Lower photoactivity in TiO2–K was due to its lower TiO2 surface-coverage.
► Inorganic ions caused surface fouling of photocatalysts used to a different extent.