Selection and optimization of the substrate in constructed wetland: A review

Constructed wetland system is an economic, efficient and environmentally friendly sewage treatment method based on adsorption and retention of pollutants by substrates, absorption by plants, and degradation by microorganisms and animals. As the largest component in the constructed wetland, substrate not only plays a huge role in the process of decontamination, but also is the hub of other components in the constructed wetland. Therefore, the selection of substrate should be paid special attention to. There are too many types of substrates. In current practical projects, certain substrate is often used directly through previous experience and personal subjective judgment, which is not targeted, resulting in poor treatment results. However, there is a lack of method for comprehensive evaluation and optimization of different types of substrates. This paper reviews the physical and chemical properties of varies constructed wetland substrates in recent years and their removal of major pollutants in sewage. The capacities for the removal of different pollutants by each substrate are evaluated. In view of the situation that it is difficult for a single substrate to achieve the ideal treatment effect, the commonly used optimization measures for constructed wetland substrates are further summarized, and suggestions for optimization methods (i.e., combination and modification) are put forward. This paper aims to make people pay more attention to the importance of substrate for treatment effect and constructed wetlands, and provides some references for how to reasonably select substrate and arrange substrate for different influent water quality. • The physical and chemical properties of varies CW substrates are reviewed. • The capacity for the removal of different pollutants by substrates is evaluated. • The common optimization measures of CW substrates are summarized. • This paper provides references for the selection and optimization of CW substrate.