Nature-based sludge treatment systems: A review of constructed wetlands for sludge management

Constructed wetlands (CWs) have been well recognised as a nature-based solution for wastewater treatment. Sludge Treatment Reed Beds (STRBs), or reed-based sludge drying beds, also referred to as the Sludge Treatment Wetland (STW), have become a sustainable and cost-effective solution for sludge treatment, offering advantages in dewatering, stabilization, and pollutant removal. This review systematically explores the updated development and application of CWs for sludge treatment, with a focus on the underlying principles, system structure, and typical operation processes. The concept and function of STRBs are elaborated, highlighting the key roles of substrate composition, plants and microbial communities. Particular attention has been given to the integration of auxiliary technologies, such as earthworm-assisted treatment and bioelectrochemical systems, which have shown significant potential in enhancing sludge mineralization and facilitating the degradation of recalcitrant organic compounds. • Nature-based treatment systems provide an effective approach for sustainable sludge management. • STRBs deliver high efficiency in dewatering, stabilization, and pollutant removal. • Treatment efficiency and filtrate quality are strongly influenced by loading rate, resting period, and vegetation. • Incorporating earthworms and microbial electrochemical systems enhance sludge mineralization and nutrient recovery. • Optimizing system configuration and operational strategy is essential for improving performance and scalability.