The Persistence of Refractory Pharmaceuticals in Aquatic Systems and Their Environmental Impacts

Abstract

The persistence of pharmaceutical residues in aquatic environments has emerged as a pressing global concern, as conventional wastewater treatment plants were not designed to remove such micropollutants. This review investigates both the occurrence of refractory pharmaceutical compounds in wastewater and the treatment strategies available to mitigate their impacts. Four representative methods are examined: nanofiltration, microbial biodegradation, constructed wetlands, and titanium dioxide (TiO₂) photocatalysis. Nanofiltration membranes have demonstrated consistent removal efficiencies above 90% for a wide range of pharmaceuticals, yet they require high operational costs and generate concentrated waste streams. Microbial biodegradation provides an environmentally friendly option, but its effectiveness is highly sensitive to natural factors such as temperature, pH, and nutrient levels, resulting in fluctuating performance across seasons and locations. Constructed wetlands represent a cost-effective and sustainable solution, though their efficiency is limited for highly persistent pharmaceuticals. TiO₂ photocatalysis achieves high degradation rates by generating strong oxidizing radicals under UV excitation, but its application is hindered by light scattering, shielding effects, and interference from natural organic matter and inorganic ions. Overall, while each method shows promise and can achieve removal rates above 70% for certain compounds, significant challenges remain in ensuring stability, scalability, and cost-effectiveness. These findings highlight the urgent need for integrated, hybrid approaches and policy-driven frameworks to safeguard aquatic ecosystems from pharmaceutical contamination.