Seasonal hydrological and water quality performance of individual and in-series stormwater infrastructures as treatment trains in cold climate

The performance of stormwater treatment trains and of their individual green infrastructure was evaluated near Montreal, Canada. Three treatment trains were studied: Train 1 – five bioretention cells in series with a wet retention pond; Train 2 – an infiltration trench in series with a dry detention pond and Train 3 – Train 2 in series with a wet retention pond. A total of 47 rain events were monitored to quantity the hydrological performance, while water quality samples were taken during 24 rainfall events. During the summer, the bioretention cells led to a reduction in runoff volumes varying from 8 to 100%. Overall, the three studied treatment trains and all of the individual infrastructures, except for the dry pond, provided reductions in the mean concentrations of total suspended solids, chemical oxygen demand, total nitrogen and total phosphorous. Results also showed that the use of a train of stormwater infrastructures can be more effective to reach Quebec's legislated targets than single infrastructures to remove those four contaminants, but only if the infrastructures are sequenced properly. Indeed, the addition of a dry basin at the end of Train 2 reduced the removal efficiency of the four studied contaminants.

Impact of Green Roofs and Vertical Greenery Systems on Surface Runoff Quality

Green roofs (GRs) and vertical greenery systems (VGSs) can contribute certain pollutants to stormwater runoff, affecting the quality of the receiving waters. The objective of this review paper is to discuss the potential impact of these systems on the quality of urban runoff. In the green building systems section, a series of materials used in greenery systems and their specific application are presented and environmentally relevant substances that could be leached out from these materials are identified as potential pollutants. After the identification of environmentally relevant pollutants that have already been measured in urban runoff and originate from these systems, an assessment of their pathways, fate, and impact in the aquatic environment is performed. Since GRs and VGSs are already considered to be solutions for stormwater quantity and quality management in urban areas, recommendations for mitigating their environmental impact through runoff are needed. It can be concluded that special focus should be placed on measures that target the pollution source, such as optimizing GR and VGS construction practices and materials used, as well as establishing appropriate decentralized stormwater treatment measures. Both of these approaches will help to reduce or even entirely avoid the emission of relevant pollutants into the aquatic environment.

Enhancing nitrate and phosphorus removal from stormwater in fold-flow bioretention system with saturated zones

The traditional bioretention systems possess a remarkably low nitrogen and phosphorus removal effect. The removal rate fluctuates greatly, and even appears as negative removal of nitrogen and phosphorus. The four simulated bioretention experimental columns with different bilayer media, packing composition and structure were constructed. Based on the traditional fillers, the modified composite fillers with hydroxy-aluminum and modified vermiculite sludge particle (HAVSP) were added. The traditional filler (C1) and the modified composite filler (C2) were added respectively, moreover the saturated zones were set up to enhance the effect of nitrogen and phosphorus removal. Removal of nutrients from experimental columns by simulated runoff efficiency was evaluated and compared. In addition, the effect of media depth on phosphorus retention and denitrifying enzyme activity in bioretention columns was also evaluated. The experimental column #2 filled with C2 had the optimum removal effect on total phosphorus (93.70%), however, the removal effect of total phosphorus by filling C1 experimental columns was insufficient (57.36%). Designed to remove nitrate (NO3−-N) and total nitrogen (TN), the experimental column #4 showed the best performance (83.54% and 92.15%, respectively). In this study, we propose a fold-flow bioretention system by filling HAVSP in combination with saturated zones. The runoff water quality can be effectively improved, and a new bioretention cell configuration can be provided for efficient stormwater treatment.

Seal Tightly and Store in a Cool Dry Place: Exploring Soil Phosphorus Storage in a Subtropical Treatment Wetland.

Oligotrophic wetlands of the Everglades are often the final recipients of nutrients from adjacent ecosystems and tend to accumulate phosphorus (P) in their soils. Understanding P source and sink dynamics in wetlands are critical for managing wetland ecosystems and protecting downstream resources. In this study, soil P storage capacity (SPSC) was evaluated within two treatment flow-ways of the Everglades Stormwater Treatment Areas (STAs). This study hypothesized that SPSC will vary between flow-ways, soil depth, and spatially along the inflow-to-outflow gradient. The P storage capacity in the STAs depend on the proportion of iron, aluminum, calcium, and magnesium (Fe, Al, Ca, and Mg, respectively) to P with floc and recently accreted soils (RAS) being associated more with Ca and Mg and pre-STA soils being associated more with Fe and Al. Phosphorus loss, as indicated from SPSC values would vary between systems and soil depths suggesting a variable condition of P sink and source within and along flow-ways. This result, while limited, demonstrates the applicability of SPSC to wetlands systems and provides information that will aid operational or management decisions associated with improving P retention of the Everglades STAs.

Urban Green Space Arrangement for an Optimal Landscape Planning Strategy for Runoff Reduction

Increased impervious surfaces due to urbanization have reduced evaporation and infiltration into the soil compared with existing natural water cycle systems, which causes various problems, such as urban floods, landslides, and deterioration of water quality. To effectively solve the urban water cycle issue, green infrastructure using urban green space has emerged to reduce runoff and increase evaporation. It has the advantage of restoring the water cycle system of urban areas by complementing the failure of conventional stormwater treatment systems. However, urban areas under high-density development have limited green space for stormwater treatment. Hence, it is necessary to efficiently utilize street trees and small green spaces to improve the urban water cycle through green space. In this study, we simulated different green space distribution scenarios in the virtual domain to find the optimal strategy of green space planning. Compared to clustered scenarios, dispersed green space distribution scenarios and placing green space downstream were more effective in reducing the runoff amount. The paper provides insights into the considerations for determining green space spatial plan and zoning regulations for stormwater treatment by green infrastructure.