Decreasing but still significant facilitation effect of cold-season macrophytes on wetlands purification function during cold winter

Abstract

To identify the facilitation effect of a cool-season aquatic macrophyte (FEam) for use in effluent purification via constructed floating wetlands (CFWs) and to determine the possible pathways used during a winter period with an average temperature of less than 5 °C, pilot-scale CFWs were planted with the cold-season macrophyte Oenanthe clecumbens and were operated as batch systems. Although some leaves withered, the roots retained relatively high levels of activity during the winter, which had average air and water temperatures of 3.63 and 5.04 °C, respectively. The N and P removal efficiencies in CFWs decreased significantly in winter relative to those in late autumn. The presence of cool-season plants resulted in significant improvements in N and P removal, with a FEam of 15.23–25.86% in winter. Microbial N removal accounted for 71.57% of the total N removed in winter, and the decrease in plant uptake was the dominant factor in the wintertime decrease in N removal relative to that in late autumn. These results demonstrate the importance of cold-season plants in CFWs for the treatment of secondary effluent during cold winters.

Assessment of Lake Water Quality and Eutrophication Risk in an Agricultural Irrigation Area: A Case Study of the Chagan Lake in Northeast China

“…Temperature is considered to be one of the primary factors determining the seasonal dynamics of eutrophication level [64]. It was pointed out that in winter, with decreasing temperatures, the dominance of the algae showed an obvious decrease.…”

Influent salinity affects substrate selection in surface flow constructed wetlands

“…Compared with widely used plant total nutrient solutions, such as Hoagland solution, the nutrient concentrations in most eutrophic water, including the in uent water in this study, are much lower than the demanded concentrations, which is probably the main reason why soil instead of water is the main source of nutrients for most rooted macrophytes (Jiang et al, 2008). Therefore, the nutrients enriched in soil by particle deposition, exchange adsorption of soil colloids and biological activity can greatly stimulate macrophyte growth and improve macrophyte resistance (Tadros et al, 2019;Zhao et al, 2018a;Zou et al, 2016). Second, compared with sand and gravel, soil can increase rhizosphere microbial abundance and thus bene t macrophyte growth because rhizosphere microorganisms stimulate the growth of macrophytes by providing nutrients and plant hormone secretion (Marschner et al, 2001;Vergani et al, 2017;Xu et al, 2009).…”

“…The in uence of in uent salinity on the performance variation between the SFCWs can be explained by the direct and indirect effects of the substrates. The direct effects of substrates include the supplying of attachment surface for bio lms and the adsorption of pollutants (Wang et al, 2020;Yan et al, 2017;Yang et al, 2018;Zou et al, 2016). The indirect effects of substrates mainly come from their in uence on macrophytes, which can affect the PF of SFCWs by direct absorption, supplying a bio lm attachment surface, functioning as a carbon source and ROL (Mei et al, 2014;Zhao et al, 2018a;Zhao et al, 2018b).…”

Plant Carbon Sources for Denitrification Enhancement and Its Mechanism in Constructed Wetlands: A Review

“…Bacterial communities participate in the biogeochemical cycles of the substrate, and their activities are crucial to energy flow and nutrient transformation in CWs [27]. Nitrogen removal is an essential process in CWs dominated by bacteria which carry out nitrification and denitrification through the enzymes encoded by functional genes [77]. Functional genes are often used as biomarkers due to their being highly related to the targeting microorganisms [78].…”