Sources, removal performance, and ecological risks of organic UV filters in wastewater treatment plants on Hainan Island

Organic ultraviolet filters (OUVFs) are widely used in personal care products and are recognized as emerging contaminants. On tropical island such as Hainan Island, intensive tourism and high OUVFs usage amplify their environmental release. However, integrated information on their sources, removal performance, and ecological risks in tropical island wastewater treatment systems remains limited. Therefore, this study aims to elucidate the occurrence patterns, dominant source contributions, and removal efficiencies of OUVFs in wastewater treatment plants (WWTPs) with various treatment configurations on Hainan Island. The overall detection frequency of 14 target OUVFs across 21 influents was 53.1%, with total concentrations ranging from 21.2 to 303.6 ng/L. Benzophenone-3 and butyl methoxydibenzoylmethane (BMDBM) together accounted for 66.4% of total concentrations. Positive matrix factorization identified outdoor water recreation-related sunscreen use (48.1%), composite inputs from human metabolism and textile washing (38.1%), and daily personal care and cleaning product use (13.8%) as the three major source categories. While WWTPs integrating enhanced biological treatment and high-efficiency solid-liquid separation technologies could achieve near complete removal of OUVFs. The removal of individual OUVF was influenced by various water quality parameters and their physicochemical properties. Hydrophilic OUVFs such as benzophenone-4 are poorly removed with even negative removal, resulting in WWTPs effluents acting as a secondary OUVF source to the aquatic environment. While the environmental risk quotient assessment indicated low short-term ecological risks (RQ < 0.1), the Environmental Health Prioritization Index identified BMDBM as a high-priority compound requiring close attention. These findings provide insights relevant to wastewater management in tropical island regions experiencing similar tourism-related pressures and sensitive coastal environments.