Meta-Analysis of Global Water Contaminants and Chemical Treatment Techniques

Ensuring global access to safe water remains a critical challenge due to the persistent occurrence of organic, inorganic, biological, and emerging contaminants. This meta-analysis systematically reviews major classes of pollutants—including pesticides, pharmaceuticals, heavy metals, pathogens, and microplastics—while evaluating the effectiveness of chemical treatment techniques designed for their removal. Treatment by conventional processes, including coagulation–flocculation, oxidation, adsorption, ion exchange, is described in function to operation principle, efficiency, and limitation. By comparison, considering the complementary advantages of different water treatment methods on dealing with different types of contaminants at different basic strengths, it also highlighted the major limitations of the water treatment including generation of byproducts, regeneration of the adsorbents, and energy and/or operational costs. Special attention is given to emerging compounds that, in many cases, escape from elimination in conventional systems—emphasizing the relevance of AOPs, engineered adsorbents, and electrochemical methods. New trends and developments, including solar-driven AOPs, biochar/bio-based AOPs and novel electrode materials, have made impressive progress in addressing emerging contaminants and trace pollutants. In the future, these new strategies will be combined with state-of-the-art chemical methodologies and the development of environmentally benign, and user-friendly, modular systems. Addressing these challenges requires intensive interdisciplinary work between scientists, engineers, and policy makers to develop environmentally and economically sustainable water treatment technologies that can adapt to evolving contamination challenges.