Comparative Assessment of Emerging Contaminants Loads in Urban and Rural Wastewater Effluents: A Review

Abstract

Emerging contaminants (ECs), encompassing pharmaceuticals, personal care products (PPCPs), endocrine-disrupting compounds (EDCs), per- and polyfluoroalkyl substances (PFAS), microplastics, and antibiotic resistance genes (ARGs), are increasingly detected in wastewater effluents worldwide. This systematic review provides a comparative assessment of EC loads in urban and rural wastewater systems, highlighting global patterns, regional disparities, and the specific context of Nigeria. Relevant peer-reviewed studies from 2021-2025 were synthesized to evaluate concentration ranges, treatment efficiency, and environmental implications. Results reveal that urban wastewater effluents generally exhibit higher EC loads, driven by higher population density, industrialization, and lifestyle-related chemical usage. However, rural effluents increasingly contribute non-negligible EC loads due to agricultural runoff, decentralized sanitation systems, and limited treatment infrastructure. The persistence of PFAS, hormones, and antibiotics underscores gaps in conventional treatment technologies, particularly in low- and middle-income countries. A synthesis from global to local scales demonstrates a clear gradient in data availability and monitoring sophistication, with Africa—especially Nigeria—representing a critical data-sparse region. Strengthening analytical capacity, promoting advanced oxidation and biological hybrid technologies, and integrating EC monitoring into national wastewater management policies are essential for sustainable control. This review provides a roadmap for comparative EC assessment, offering insights for future research, policy harmonization, and the protection of aquatic ecosystems in urban and rural contexts.