A review of sewage sludge treatment and management methods in wastewater treatment plants

The purpose of this paper was to review the methods of sewage sludge treatment and management in wastewater treatment plants with particular emphasis on constructed wetland systems as nature-based solutions (NBS).Sewage sludge management is one of the major challenges associated with wastewater treatment due to the high associated costs of sludge processing, transport, and disposal, as well as the increasing environmental requirements concerning its safe utilization and overall carbon footprint.This review presented the current state of knowledge on sewage sludge treatment and management, with particular emphasis on technologies suitable for small and decentralized wastewater treatment plants.Conventional methods, including thickening, mechanical dewatering, anaerobic and aerobic stabilization, composting, chemical stabilization, thermal drying, incineration, pyrolysis, and gasification, were discussed in terms of their technological characteristics, environmental impacts, energy requirements, and applicability.Attention was given to NBS, especially Sludge Treatment Reed Beds (STRB), which enable simultaneous dewatering, drying, and partial stabilization of sludge through filtration, gravity drainage, evapotranspiration, and biological processes.The literature indicated that STRB can significantly reduce sludge volume while requiring relatively low energy inputs and limited-to-zero chemical addition.These characteristics make this technology particularly promising for small and decentralized wastewater treatment plants, where conventional sludge treatment technologies are often economically and technically difficult to implement.The effectiveness of STRB depends mainly on the sludge loading rate, feeding frequency, resting periods, filter media properties, vegetation development, and climatic conditions.Despite their advantages, limitations related to land requirements, long treatment periods, seasonal variability, and the risk of clogging must be considered.The review highlighted the potential of STRB as a low-energy and environmentally sustainable approach to local sewage sludge management and identifieed the need for further research on design parameters adapted to temperate climates and decentralized wastewater treatment systems.