Mechanism-Based and Biologically Active Filtration Technologies for Turbidity Control in Water Treatment and Reuse

Turbidity, a key indicator of water quality, arises from suspended and colloidal particles that reduce clarity, hinder disinfection, disrupt aquatic ecosystems, and undermine consumer confidence. With increasing pressures from global water pollution, effective turbidity control is critical for protecting public health, supporting industrial operations, and maintaining environmental sustainability. It is also essential for the stable performance of water treatment processes, including biologically mediated systems such as slow sand filtration. A wide range of treatment techniques, spanning conventional approaches to advanced emerging technologies, are available for turbidity removal; however, existing reviews often consider these methods in isolation, limiting comparative insight. This review presents a mechanism-based classification framework that integrates both traditional and modern approaches. Treatment methods are classified according to their underlying mechanisms, including particle destabilization, aggregation, and separation; adsorptive and transformation processes; and hybrid or assisted systems that combine multiple mechanisms. For each category, the review examines fundamental principles, operational mechanisms, turbidity removal efficiencies, advantages, and limitations, supported by relevant case studies. A comparative discussion highlights the strengths and constraints of different methods, providing a comprehensive reference to guide the selection and optimization of turbidity control strategies across diverse water matrices and treatment objectives.