Plants used in constructed wetlands with horizontal subsurface flow: a review

Abstract

The presence of macrophytes is one of the most conspicuous features of wetlands and their presence distinguishes constructed wetlands from unplanted soil filters or lagoons. The macrophytes growing in constructed wetlands have several properties in relation to the treatment process that make them an essential component of the design. However, only several roles of macrophytes apply to constructed wetlands with horizontal subsurface flow (HF CWs). The plants used in HF CWs designed for wastewater treatment should therefore: (1) be tolerant of high organic and nutrient loadings, (2) have rich belowground organs (i.e. roots and rhizomes) in order to provide substrate for attached bacteria and oxygenation (even very limited) of areas adjacent to roots and rhizomes and (3) have high aboveground biomass for winter insulation in cold and temperate regions and for nutrient removal via harvesting. The comparison of treatment efficiency of vegetated HF CWs and unplanted filters is not unanimous but most studies have shown that systems with plants achieve higher treatment efficiency. The vegetation has mostly a positive effect, i.e. supports higher treatment efficiency, for organics and nutrients like nitrogen and phosphorus. By far the most frequently used plant around the globe is Phragmites australis (Common reed). Species of the genera Typha (latifolia, angustifolia, domingensis, orientalis and glauca) and Scirpus (e.g. lacustris, validus, californicus and acutus) spp. are other commonly used species. In many countries, and especially in the tropics and subtropics, local plants including ornamental species are used for HF CWs.

Removal of antibiotics and antibiotic resistance genes from domestic sewage by constructed wetlands: Effect of flow configuration and plant species

“…With regard to COD, TN and TOC, it was found that the CW1 (SF-CW) and CW6 (HSSF-CW without plants) performed worse than the other four CWs including two HSSF-CWs and two VSSF-CWs. Subsurface flow and planting were beneficial to the removal of nutrients, which is consistent to some previous studies (Brix, 1994;Lin et al, 2002b;Wen et al, 2010;Vymazal, 2011;Carvalho et al, 2014). For 8 detected antibiotics, CW4 and CW5 (HSSF-CWs with different plants) performed better than the other four CWs, with CW1 being the worst (Fig.…”

Constructed wetlands with light expanded clay aggregates for agricultural wastewater treatment

“…This contribution of plants is consistent with the effects on removal of other xenobiotics by other species in LECA beds (Dordio et al, 2009b(Dordio et al, , 2010. In addition to other more basic roles of plants in CW operation (Brix, 1997;Vymazal, 2011), these results demonstrate the potential for an equally important and active role played by the vegetation in the removal of specific organic pollutants such as MCPA, which enables the performance of planted systems to surpass that of a simpler LECA filter setup. Due to the moderate lipophilicity of MCPA, as expressed by its octanol-water partition coefficient (log K ow = 1.37-1.43 (Montgomery, 1993)), it is likely that plants have an active role in the removal of this compound through direct uptake.…”

Comparison of three plants in a surface flow constructed wetland treating eutrophic water in a Mediterranean climate

“…In CWs designed to treat eutrophic water, the main goal of vegetation is to reduce solar radiation, thus limiting phytoplankton growth and promoting its decomposition and sedimentation. Other important functions of vegetation in CWs are as follows: reduction of water current, mitigation of wind velocity, induction of sedimentation and prevention of sediment resuspension, active nutrient uptake and retention within the biomass, provision of surface for periphyton growth, and oxygen transport to sediment both during the active growth phase and through the death culms (Vymazal, 2011 ). The vegetation cover can also add aesthetic values contributing to the landscaper quality.…”