Temperature and Wetland Plant Species Effects on Wastewater Treatment and Root Zone Oxidation

Abstract

Constructed wetlands are widely used for wastewater treatment, but there is little information on processes affecting their performance in cold climates, effects of plants on seasonal performance, or plant selection for cold regions. We evaluated the effects of three plant species on seasonal removal of dissolved organic matter (OM) (measured by chemical oxygen demand and dissolved organic carbon) and root zone oxidation status (measured by redox potential [Eh] and sulfate [SO4(2-)]) in subsurface-flow wetland (SSW) microcosms. A series of 20-d incubations of simulated wastewater was conducted during a 28-mo greenhouse study at temperatures from 4 to 24 degrees C. Presence and species of plants strongly affected seasonal differences in OM removal and root zone oxidation. All plants enhanced OM removal compared with unplanted controls, but plant effects and differences among species were much greater at 4 degrees C, during dormancy, than at 24 degrees C, during the growing season. Low temperatures were associated with decreased OM removal in unplanted controls and broadleaf cattail (Typha latifolia L.) microcosms and with increased removal in beaked sedge (Carex rostrata Stokes) and hardstem bulrush [Schoenoplectus acutus (Muhl. ex Bigelow) A. & D. Löve var. acutus] microcosms. Differences in OM removal corresponded to species' apparent abilities to increase root zone oxygen supply. Sedge and bulrush significantly raised Eh values and SO4(2-) concentrations, particularly at 4 degrees C. These results add to evidence that SSWs can be effective in cold climates and suggest that plant species selection may be especially important to optimizing SSW performance in cold climates.

Effect of Macrophyte Species on Subsurface Flow Wetland Performance in Cold Climate

“…The enhancement of species differentiation in winter is consistent with other studies (IWA, 2000;Allen et al, 2002). Because the aboveground portion of the biomass was harvested, the difference is at the root level, largely attributed to the root structure and biomass allocation.…”

“…Plant species does not make a difference in many studies (Bachand and Horne, 2000;Jing et al, 2002). Typha latifolia out-performed in some species comparison (Coleman et al, 2001), while in others its efficiency may decreased during winter (Allen et al, 2002). Typha angustifolia was very performant in our study.…”

“…Moreover, HSSFCW can be integrated in the landscape and create wildlife habitat (Kadlec and Knight, 1996). Most studies comparing planted versus non-planted system showed a significant positive effect of plants on nutrients removal (IWA, 2000;Allen et al, 2002.…”

Performance of tropical vertical subsurface flow constructed wetlands for leachate treatment at different hydraulic loading rates

“…The variation of the performance with the type of pre-treatment was reported by Wojciechowska et al, (2010). Although majority of previous studies had used domestic or municipal wastewater to investigate the role of the plant species in CWs (Allen et al, 2002), studies done on industrial wastewaters for example paper-mills (Abira et al, 2003), tannery (Calheiros, et al, 2007), and fish-farm (Naylor et al, 2003) and ground water (Lin et al, 2002) are also available. The effect of loading rates was the most common factor evaluated along with plant species (Brisson and Chazarenc, 2008).…”

Reduction of Heavy Metals from Waste Water by Wetland

“…Free water surface (FWS) wetlands (also known as surface flow wetlands) closely resemble natural wetlands in appearance because they contain aquatic plants that are rooted in a soil layer on the bottom of the wetland and water flows through the leaves and stems of plants (Carleton et al, 2011). Vegetated sub-merged bed (VSB) systems (also known as subsurface flow wetlands) do not resemble natural wetlands because they have no standing water (Allen et al, 2012). They contain a bed of media (such as crushed rock, small stones, gravel, sand or soil) which has been planted with aquatic plants.…”