Clogging mechanisms of constructed wetlands: A critical review

Clogging is a significant concern in the development of constructed wetlands (CWs). This review performs an in-depth analysis of the reasons, influencing factors and regularities of CW clogging and provides an important basis for treatments addressing clogging in CWs. The factors affecting CW clogging primarily include substrate porosity, hydraulic load, oxygen supply conditions, organic loading, water depth, and plants; among these factors, organic loading and substrate porosity have the most significant impact. The use of proper particle size, multilayer substrates and backwashing helps to slow CW clogging. Selecting aquatic plants with developed root systems and removing leaves and dead roots in a timely manner can significantly reduce CW clogging. The cost of earthworms used in CWs is significantly lower than that of substrate replacement and backwashing. To improve the comprehensive application effect of CWs, future research efforts should attempt to combine the findings of anti-clogging research and improve the purification effect of CWs. This review is of considerable significance for promoting the sustainable development of CWs. [Display omitted] •The organic load and porosity of the substrate have significant impact on CW clogging.•The selection of aquatic plants with developed root can be used to reduce CW clogging.•The earthworm culture to address CW clogging is less expensive than other methods.•The mechanism of clogging in CWs is reviewed to prevent CW clogging.