Development and Optimisation of a Hybrid Adsorption-Photocatalysis System for Pharmaceutical Micropollutant Removal from Hospital Wastewater in Ogun State

Hospital wastewater in Ogun State, South West Nigeria, contains a complex mixture of active pharmaceutical ingredients, disinfectants, and antibiotic-resistant organisms that pass through conventional treatment systems without adequate removal, threatening downstream water resources. This study develops and optimises a hybrid system combining activated carbon adsorption with zinc oxide photocatalysis for the simultaneous removal of ciprofloxacin, diclofenac, and amoxicillin from hospital effluent at a referral hospital in Sagamu. Activated carbon was prepared from coconut shell waste, and zinc oxide nanocomposites were synthesised by chemical precipitation and characterised by X-ray diffraction, BET analysis, and diffuse reflectance spectroscopy. The hybrid system was designed with an adsorption column upstream of a photocatalytic annular reactor with ultraviolet-A light irradiation. Central composite design was used to optimise ultraviolet irradiation time, initial pollutant concentration, photocatalyst loading, and activated carbon bed depth for combined pollutant removal. Under optimised conditions of 120-minute irradiation time and 1.2 g/L catalyst loading, combined removal of the three target compounds exceeded 94.8% in all cases. Degradation kinetics followed a pseudo-first-order model. Ecotoxicity testing using Artemia salina bioassay confirmed that treated effluent was non-toxic at the 95% confidence level. The system demonstrated stable performance over ten consecutive treatment cycles. The study presents a locally implementable advanced treatment solution for hospital wastewater in Nigeria with direct relevance to antibiotic resistance mitigation. Keywords: photocatalysis, adsorption, pharmaceutical micropollutants, hospital wastewater, Ogun State