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The Puget Sound Basin, US Pacific Northwest, is experiencing rapid population and urban growth. This growth adversely impacts local ecosystems, especially the spawning and rearing habitat for several salmonid species. Sustainable urban design strategies such as green stormwater infrastructure (GSI) are required in the region to manage stormwater onsite when new development occurs. However, the effectiveness of any GSI depends on its location relative to where stormwater is produced. This study aimed to develop a Geographic Information System (GIS)‐based framework for the optimal placement of GSI, specifically bioretention systems. We computed the Hydrologic Sensitivity Index (λHSI, indicating runoff generation potential at a landscape location) for the lower Puyallup River Watershed study area. The index and federal and state feasibility criteria were used to identify suitable sites for bioretention systems. The suitability of identified sites was verified through ground‐truthing, including soil sampling and infiltration testing. We found that 2.5% of the watershed area was suitable for bioretention, concentrated in the center and north of the study watershed. The method described in this study can be readily applied to watersheds for which spatial data (topography, soil, and land use) are available. We recommend choosing locations with high λHSI when resources are limited since these locations contribute most to runoff generation and urban flooding. [ABSTRACT FROM AUTHOR]

Increasing urbanization and the associated sealing of areas and the use of storm sewer systems for drainage not only increase the risk of flooding but also reduce water quality in streams into which stormwater is discharged. Green infrastructure (GI) measures are applied with the aim of managing this stormwater sustainably and reducing the associated risks. To this end, a quantitative–qualitative approach was developed to simulate GI—namely, rain gardens, bioretention cells, and vegetative bioswales—at the urban catchment scale. The findings highlight the potential of applying GI measures to managing stormwater more effectively in urban environments and mitigating its negative pollution-related impacts. For the housing estate analyzed, a simulated implementation of GI resulted in a reduction in pollution, measured as total nitrogen (N; 9–52%), nitrate-N (5–30%), total phosphorus (11–59%), chemical oxygen demand (8–46%), total suspended solids (13–73%), copper (12–64%), zinc (Zn; 16–87%), polycyclic aromatic hydrocarbons (16–91%), and the hydrocarbon oil index (HOI; 15–85%). Reducing the concentrations of pollutants minimizes the risk to human health determined via the HOI from a low-risk level to zero risk and reduces the ecological risk in terms of Zn pollution from a significant risk to a low risk of adverse effects. The modeling conducted clearly shows that the GI solutions implemented facilitated a quantitative reduction and a qualitative improvement in stormwater, which is crucial from an environmental perspective and ensures a sustainable approach to stormwater management. Lowering the levels of stormwater pollution through the implementation of GI will consequently lower the environmental burden of pollutants in urban areas. [ABSTRACT FROM AUTHOR]

The use of nature-based solutions (NBSs) for hazard mitigation is increasing. In this study, we review the use of NBSs for flood mitigation using a strengths, weaknesses, opportunities, and threats (SWOT) analysis framework for commonly used NBSs. Approaches reviewed include retention and detention systems, bioretention systems, landcover and soil management, river naturalisation and floodplain management, and constructed and natural wetlands. Existing tools for identification and quantification of direct benefits and co-benefits of NBSs are then reviewed. Finally, approaches to the modelling of NBSs are discussed, including the type of model and model parameterisation. After outlining knowledge gaps within the current literature and research, a roadmap for development, modelling, and implementation of NBSs is presented. [ABSTRACT FROM AUTHOR]

Urban nature-based solutions (NBSs) are widely implemented to collect, store, and infiltrate stormwater. This study addressed infiltration rate as a measure of the performance of bioretention solutions. Quick scan research was conducted, starting with mapping over 25 locations of implemented green infrastructure in Riga, Latvia. Basic information, such as location, characteristics, as well as photos and videos, has been uploaded to the open-source database ClimateScan. From this, eight bioswales installed in the period 2017–2022 were selected for hydraulic testing, measuring the infiltration capacity of bio-retention solutions. The results show a high temporal and spatial variation of infiltration rate for the bioswales, even those developed with similar designs: 0.1 to 7.7 m/d, mean 2.0 m/d, coefficient of variation 1.0. The infiltration capacity decreased after saturation: a 30% to 58% decrease in infiltration rate after refilling storage volume. The variation in infiltration rate as well as infiltration rate decrease on saturation is similar to other full-scale studies done internationally. The infiltration rate of most bioswales falls within the range specified by international guidelines, all swales empty within 48 h. Most bioswales empty several times within one day, questioning the effectiveness of water retention and water availability for dry periods. The results are of importance for stakeholders involved in the implementation of NBS and will be used to set up Latvian guidelines for design, construction, and maintenance. [ABSTRACT FROM AUTHOR]

Bioretention is a type of stormwater best management practice that can reduce stormwater runoff volume, and with appropriate design, simultaneously reduce nitrogen loads. To meet the water quality potential of bioretention systems, improved simulation models of the transport and transformations of nitrogen are needed. In this work, two versions of a three-nitrogen-pool (3P) model (3P-1 and 3P-m) are applied to simulate observed nitrogen transport through a field bioretention system. The 3P models provide predictions of net export of dissolved organic carbon, dissolved organic nitrogen, and inorganic nitrogen species. The 3P-m model has promising results: (1) relative to the Storm Water Management Model (SWMM), it reduced the prediction error of percent removal of total dissolved nitrogen by up to 10.6% and reduces the scaled root-mean square error of total dissolved nitrogen loads by up to 53.0%; (2) it successfully captured the correlation between impactful environmental factors and event mean concentrations of total dissolved nitrogen and nitrate nitrogen in underdrain effluent; (3) its predictions on denitrification showed good alignment with observed isotope results; and (4) it demonstrated higher stability in simulated time series among calibration results than 3P-1. The 3P-m is expected to assist the design of bioretention system and valve control strategies by providing more accurate predictions on nitrogen removal under the impacts of soil moisture content and temperature. Future research and collaboration opportunities are also proposed in this article. [ABSTRACT FROM AUTHOR]

Stormwater transports directly into rivers eroded soil, animal wastes, pesticides, fertilizers and other potential pollutants. Bioretention is often designed to capture and treat it using the natural properties of soil and plants. However, selection of appropriate media structure and plants need to be adequately studied. This study investigated the performance of bioretention system in removing stormwater pollutants using Dracaena, a local plant, also called Song of India Plants. Physical model of three Columns A, B and C were developed having five layered filter media of different configurations whose materials were analyzed to meet the design standards. The plants were introduced into Columns A and C leaving out B as control experiment. The quality parameters were determined before and after treatments at ages 10, 20, 30 and 40 days when Dracaena plants were introduced into bioretention models. The results showed that the bioretention model drastically improved stormwater quality by reducing values of electrical conductivity, total coliforms (TC), fecal coliforms (FC), total suspended solids (TSS) and biochemical oxygen demand (BOD) as compared to the tested raw stormwater samples. The filter media in both Columns A and C substantially reduced the pollutant levels to standard discharge limits for all parameters tested such as TSS, TC, FC, BOD and nitrates. BOD fell within the recommended standard after 20 days of treatment in Column C with considerable reduction in TC and FC by 68.9% and 75.4% respectively when compared to raw stormwater sample. However, Column C completely removed TC and FC at 40 days which are pathogen indicators in wastewater. This study would be useful to the stakeholders for sustainable stormwater treatment and management. [ABSTRACT FROM AUTHOR]

Stormwater transports directly into rivers eroded soil, animal wastes, pesticides, fertilizers and other potential pollutants. Bioretention is often designed to capture and treat it using the natural properties of soil and plants. However, selection of appropriate media structure and plants need to be adequately studied. This study investigated the performance of bioretention system in removing stormwater pollutants using Dracaena, a local plant, also called Song of India Plants. Physical model of three Columns A, B and C were developed having five layered filter media of different configurations whose materials were analyzed to meet the design standards. The plants were introduced into Columns A and C leaving out B as control experiment. The quality parameters were determined before and after treatments at ages 10, 20, 30 and 40 days when Dracaena plants were introduced into bioretention models. The results showed that the bioretention model drastically improved stormwater quality by reducing values of Electrical Conductivity, Total Coliforms (TC), fecal Coliforms (FC), Total Suspended Solids (TSS) and Biochemical Oxygen Demand (BOD) as compared to the tested raw stormwater samples. The filter media in both Columns A and C substantially reduced the pollutant levels to standard discharge limits for all parameters tested such as TSS, TC, FC, BOD and nitrates. BOD fell within the recommended standard after 20 days of treatment in Column C with considerable reduction in TC and FC by 68.9 % and 75.4 % respectively when compared to raw stormwater sample. However, Column C completely removed TC and FC at 40 days which are pathogen indicators in wastewater. This study would be useful to the stakeholders for sustainable stormwater treatment and management.

Bioretention can be an efficient measure of stormwater treatment. The bioretention system has been globally adapted for controlling rainfall-runoff volume and removing pollutants. However, there is a lack of systematic analysis of some hydrological processes in the bioretention facility, such as the transportation of rainfall-runoff (event water) and soil water (pre-event water). This research uniquely applied stable isotope tracing to a bioretention system to investigate the transport of rainfall-runoff and the movement of soil water in a bioretention column. The stable isotope tracing method is helpful for determining the transport process of water and is expected to enhance our understanding of bioretention systems. The ratio of the event rainfall-runoff and the pre-event soil water in the bottom outflow of bioretention columns was calculated by the stable isotope bivariate mixing model based on the oxygen and hydrogen stable isotopic data from continuous testing in the discharge of bioretention column. The time-varying proportion of event water and pre-event water in the hydrographic curve reveals that the outflow process of soil water is divided into three stages. In the early stage, all the outflow was soil water, accounting for about 6–13% of the total outflow. In the middle stage, the proportion of soil water rapidly decreased from 100% to 20% within a few minutes. In the later stage, the soil water proportion decreased slowly from 20% to 0%. The outflow of soil water accounted for more than 36% of the total outflow and decreased with the extension of the drought period. Soil water is a critical part of the bottom outflow of bioretention columns, and the influence of soil water on the hydrological effect of bioretention columns cannot be ignored. [ABSTRACT FROM AUTHOR]

Bioretention systems are a low-impact development (LID) measure to effectively control stormwater runoff and reduce pollutant concentrations. In this paper, three groups of bioretention cells with different filling materials (1# bioretention soil media (BSM), 2# BSM + 5% biochar, and 3# BSM +5% biochar +biological filler) were constructed to analyze the pollutant removal characteristics and microbial action under different simulated rainfall conditions. Results showed that the overall pollutant removal capacity of systems 2# and 3# was higher than that of system 1#, with system 3# having the lowest effluent concentrations of 2.71 mg/L for total nitrogen (TN) and 64.3 mg/L for chemical oxygen demand (COD). The load reduction effect for heavy metals of the three systems was ranked as 2# > 1# > 3#, and average load reduction rates were 80.3, 75.1, and 84.8% for Cu, Pb, and Zn in 2#. Microbial community analysis indicated that Proteobacteria and Firmicutes were the absolute dominant bacteria of the three bioretention systems, and the dominant genera included Bacillus, Hyphomicrobium, Micrococcaceae, and Nitrospira. In addition, the total number of denitrifying functional bacteria genera in systems 2# and 3# was increased by 1.39 and 52.1% compared to system 1#. HIGHLIGHTS The bioretention system of composite filler coupled with the water storage area was constructed for advanced treatment of stormwater runoff.; The overall pollutant removal capacity of the modified bioretention systems 2# (BSM + 5%BC) and 3# (BSM + 5%BC + BM) was improved.; The total number of denitrifying functional bacteria genera in system 3# (BSM + 5%BC + BM) was increased by 52.1% compared to system 1# (BSM).;

The urban development increase in the built-up areas leads to more impervious areas with the consequence of larger runoff. Undeniably, this excess water has many benefits. Low-impact development (LID) is one of the innovations to conserve wasted runoff water. The two LID scenarios (water storage – WS; infiltration – I) under different rainfall depths (20, 25, 30, 35 mm) are assessed using Storm Water Management Model (SWMM) and analyzed based on their benefit–cost. This study aims to evaluate the hydrological performance and the benefit–cost ratio to identify the optimal LID design. The benefit calculation is not only projected by runoff reduction aspects, but also the other opportunities aspects. Based on the hydrological performance, scenario I shows a higher runoff reduction performance than scenario WS. Based on the benefits aspects studied, scenario I provides greater benefits with more cost than the WS scenario. Rainfall depth influenced the life cycle cost with 20-mm WS scenario experiencing faster payback period than other scenarios. HIGHLIGHTS Scenario infiltration excels in reducing runoff, particularly in low rainfall conditions.; Scenario water storage with 20-mm rainfall depth offers the best cost-effectiveness, but sensitivity to costs and discount rate emphasized.;

The effects of different soil properties on hydrology and nitrogen removal were studied in a simulated bioretention system. Soil capacity of permeability and water retention, changes in the soil environment, leachate concentrations at the surface and bottom layers, quantification of N removal from soil, microorganism and plant by 15N isotope tracer technique, and functional genes abundance at different depths were evaluated. The results showed that shallow root plants, soil compaction, and low organic matter content were not conducive to the infiltration of bioretention systems. In the 72 h experiment, compaction (especially surface compaction) and planting of herbaceous plants (Ophiopogon japonicus) were not beneficial to the removal of TN, TP, and COD. Adding an appropriate amount of organic matter also affects nitrogen and phosphorus removal. In the process of denitrification, the order of the ability to remove nitrogen is soil adsorption > microbial assimilation > plant uptake. The contribution of soil denitrification is affected by soil compaction, compaction location, plant species and organic matter content. The abundance of 16S rRNA, nitrifying, denitrifying and nrfA genes decreased with soil depth. More copies of genes in topsoil were thought to be due to sufficient nutrients, aerobic condition, anaerobic microsites and submerged state. Soil compaction, organic matter content and plant species affected nitrification, denitrification and DNRA gene characteristics. [ABSTRACT FROM AUTHOR]

Bioretention systems use plants and soil media to treat pollutants in stormwater. Biochar can be an effective amendment to bioretention soil media for removing pollutants due to its adsorption properties. This study evaluates biochar as an amendment to bioretention soil media for the removal of contaminants in stormwater. Columns with varying ratios of biochar to bioretention soil media (0%, 25%, and 50% biochar) were tested to evaluate the removal efficiencies of copper, zinc, phosphorus, nitrogen, and microplastics from stormwater. Five trials were conducted with stormwater collected from parking lot runoff. Results show that the addition of biochar in bioretention systems improves the removal efficiency of zinc (average of 79% in columns with 50% biochar compared to 54% in columns without biochar) and copper (average of 73% in columns with 50% biochar compared to 25% in columns without biochar). Stormwater effluent from the biochar-amended columns also had significantly lower turbidity (21 NTU) than that of the control columns (58 NTU). Consistent leaching of nitrogen and phosphorus species was evident in the control as well as the biochar-amended columns, with average removal efficiencies of −1,114% for total nitrogen and −703% for total phosphorus. Microplastics were effectively removed by all columns, regardless of biochar amendment, with an average removal of 86%. This study indicates that biochar has the potential to reduce metal concentrations in stormwater when used as an amendment to bioretention systems but has a limited impact on nutrients and microplastics. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) present significant risks to human health owing to their carcinogenic, teratogenic, and mutagenic properties. The contamination of surface water with PAHs via runoff has become a prominent source of water pollution. While the capacity of bioretention systems to remove PAHs from runoff is recognized, the dynamics of PAH migration and degradation in these systems are not well-understood. This study aims to explain the migration and fate of PAHs in bioretention systems through a series of experiments and model simulations. This study constructed bioretention systems with three different media types and found that these systems achieved PAH load reductions exceeding 92%. Notably, naphthalene (NAP), fluoranthene (FLT), and pyrene (PYR) tended to accumulate in the media's upper layer, at depths of 10 to 40 cm. To further analyze the migration and fate of PAHs during multi-site rainfall events and across prolonged operation, we applied the HYDRUS-1D model under three distinct scenarios. The findings of this study indicated that NAP degraded in 40 d, whereas FLT and PYR showed incomplete degradation after 120 d. During continuous rainfall events, there was no clear pattern of PAH accumulation; however, FLT and PYR persisted in the bioretention systems. The combination of experimental and simulation findings highlights the inevitable accumulation of PAHs during extended use of bioretention systems. This research provides a theoretical basis for improving operational efficiency, advancing PAH degradation in bioretention systems, and reducing their toxicity. [ABSTRACT FROM AUTHOR]

Various factors, such as rainfall conditions, may influence nutrient removal by bioretention filters. The aim of this study was to evaluate how antecedent dry periods (ADP) affected the removal of nutrients by a laboratory-scale bioretention system. A bioretention filter system comprising columns with different media, treatment, and submerged zone combinations was set up. The treatments included 10% (v/v) water treatment residual to enhance the phosphorus (P) removal and 10% (v/v) zero-valent iron to enhance the nitrogen (N) removal. Semi-synthetic runoff was applied to explore how ADPs (from 1 to 10 days) affected the N and P removal. The denitrification efficiency was determined from the variations in the N concentrations in the submerged zone over 14 days. Without a submerged zone, the total nitrogen (TN) removal increased, the chemical oxygen demand (COD) removal decreased, and there was no clear trend for total phosphorus (TP), dissolved P, or particulate P as the duration of the ADP increased. When the bioretention filter had a submerged zone, the TN removal peaked at 82.64 ± 0.24% and 84.50 ± 0.28% for an ADP of 10 days. When zero-valent iron was added to a filter with a submerged zone, the denitrification improved significantly, and the TN removal reached 92.95 ± 1.50% and 92.16 ± 2.28% for an ADP of 5 days. The iron also significantly promoted the COD and TP removal efficiencies of the bioretention filter, but was not significantly related to the ADP. The TN and ammonia concentrations in a filter with a submerged zone decreased significantly in the first 3 days of the ADP, and then stabilized after 5 days. These results provide a reference for determining the effectiveness of a submerged zone in bioretention systems. [ABSTRACT FROM AUTHOR]

The use of nature-based solutions (NBSs) for hazard mitigation is increasing. In this study, we review the use of NBSs for flood mitigation using a strengths, weaknesses, opportunities, and threats (SWOT) analysis framework for commonly used NBSs. Approaches reviewed include retention and detention systems, bioretention systems, landcover and soil management, river naturalisation and floodplain management, and constructed and natural wetlands. Existing tools for identification and quantification of direct benefits and co-benefits of NBSs are then reviewed. Finally, approaches to the modelling of NBSs are discussed, including the type of model and model parameterisation. After outlining knowledge gaps within the current literature and research, a roadmap for development, modelling, and implementation of NBSs is presented.

Urban nature-based solutions (NBSs) are widely implemented to collect, store, and infiltrate stormwater. This study addressed infiltration rate as a measure of the performance of bioretention solutions. Quick scan research was conducted, starting with mapping over 25 locations of implemented green infrastructure in Riga, Latvia. Basic information, such as location, characteristics, as well as photos and videos, has been uploaded to the open-source database ClimateScan. From this, eight bioswales installed in the period 2017–2022 were selected for hydraulic testing, measuring the infiltration capacity of bio-retention solutions. The results show a high temporal and spatial variation of infiltration rate for the bioswales, even those developed with similar designs: 0.1 to 7.7 m/d, mean 2.0 m/d, coefficient of variation 1.0. The infiltration capacity decreased after saturation: a 30% to 58% decrease in infiltration rate after refilling storage volume. The variation in infiltration rate as well as infiltration rate decrease on saturation is similar to other full-scale studies done internationally. The infiltration rate of most bioswales falls within the range specified by international guidelines, all swales empty within 48 h. Most bioswales empty several times within one day, questioning the effectiveness of water retention and water availability for dry periods. The results are of importance for stakeholders involved in the implementation of NBS and will be used to set up Latvian guidelines for design, construction, and maintenance.

Bioretention practices have become a common way to protect natural waterways in urban and suburban landscapes across the United States. However, optimal design, implementation, operation, and maintenance are still in need of study. A field survey of 52 bioretention practices was conducted in Davidson County, Tennessee, to address research questions related to operation and maintenance. A suite of site conditions were documented, such as size, signs of erosion, and dominant surface cover. Samples were collected from the surface of the engineered media layer and analyzed for organic matter content and bulk density. Vegetation was described in terms of dominant species and canopy cover. On average, the organic matter content of media under plant‐based mulch cover was significantly greater than that under rock cover (p = 0.002). Bulk density of the surface media is strongly and inversely correlated to organic matter content; bulk density did not generally vary with bioretention area age and was highly variable within treatments. On average, the bulk density of the media under the plant‐based mulch cover was significantly less than that under the rock cover. Media under the composite treatments had similar bulk density to both the plant‐based mulch (p = 0.233) and the rock covers (p = 0.132). Plant canopy did not surpass 70% in practices with bulk density values above 1.55 g/cm3. These results suggest that consideration should be made regarding the tradeoffs between utilizing rock coverings and potential for plant establishment impacts. [ABSTRACT FROM AUTHOR]

In this study, lab-scale bioretention cells were designed for the investigation of antibiotic-resistant bacteria (ARB) outflow profiles at different depths, effects of adsorption and transmission, as well as modelling evaluation of ARB outflow risks using the common decay models (e.g., first-order decay models). ARB outflow was first found in the upper layers (after 100 days of the operation) with the lowest transmission frequencies of antibiotic resistance. Although the adsorption of ARB onto the substrate and its surface biofilms was effective with the maximum amount of ARB adsorbed (Qmax) reaching 108 CFU/g of the substrate and 107 CFU/g of biofilms, ARB outflow was detected in the bottom outlets after over 4 months of operation, reflecting that there was still a risk of antibiotic resistance through the treatment of bioretention cells. ARB outflow for both upper and middle outlets could be well described by third-order polynomial equations with correlation coefficients 0.9067 (p = 0.0002) and 0.9780 (p < 0.0001), respectively, where there were both positive and negative relationships between outflow ARB and inflow ARB, confirming the combined action of mechanisms blocking ARB outflow (e.g., substrate adsorption) and promoting ARB outflow (like transmission). These suggested two potential controlling approaches for ARB outflow from stormwater bioretention cells. HIGHLIGHTS Antibiotic-resistant bacteria (ARB) outflow appeared first in upper layers with the lowest transmission frequencies.; ARB adsorption by substrate and its surface biofilms was found to be effective.; Antibiotic resistance transmission was not the only decisive factor for ARB outflow.; ARB outflow could not be described by the conventional first-order kinetics.;

The urban heat island (UHI) problem is essential for urban living, significantly worldwide urban areas. The preliminary studies found that rising temperatures are proportional to the city’s density and affect human outdoor thermal comfort, which is related to the increasing demand for real estate development, such as the condominium projects located in the city. This research will identify the relationship between outdoor thermal comfort and the bioretention asset to support sustainable city development. Then, this result conducts the outdoor area design guideline for real estate development with nature-based solution responsibility by using bioretention based on the water-sensitive urban design concept. The results show that CASE-03: bioretention combined with large trees can provide additional outdoor thermal comfort during daytime. A preliminary study of the outdoor thermal impacts that affected outdoor thermal comfort and the results will be used as a sustainable guideline for landscape architecture practices in future developments in the city.

Low-Impact Developments (LIDs), like green roofs and bioretention cells, are vital for managing stormwater and reducing pollution. Amidst climate change, assessing both current and future LID systems is crucial. This study utilizes variably saturated flow modeling with the HYDRUS software (version 4.17) to analyze ten locations in Ontario, Canada, focusing on Toronto. Historical and projected climate data are used in flow modeling to assess long-term impacts. Future predicted storms, representing extreme precipitation events, derived from a regional climate model, were also used in the flow modeling. This enabled a comprehensive evaluation of LID performance under an evolving climate. A robust methodology is developed to analyze LID designs, exploring parameters like water inflow volumes, peak intensity, time delays, runoff dynamics, and ponding patterns. The findings indicate potential declines in LID performance attributed to rising water volumes, resulting in notable changes in infiltration for green roofs (100%) and bioretention facilities (50%) compared to historical conditions. Future climate predicted storms indicate reduced peak reductions and shorter time delays for green roofs, posing risks of flooding and erosion. Anticipated extreme precipitation is projected to increase ponding depths in bioretention facilities, resulting in untreated stormwater overflow and prolonged ponding times exceeding baseline conditions by up to 13 h at numerous Ontario locations.

Bioretention can be an efficient measure of stormwater treatment. The bioretention system has been globally adapted for controlling rainfall-runoff volume and removing pollutants. However, there is a lack of systematic analysis of some hydrological processes in the bioretention facility, such as the transportation of rainfall-runoff (event water) and soil water (pre-event water). This research uniquely applied stable isotope tracing to a bioretention system to investigate the transport of rainfall-runoff and the movement of soil water in a bioretention column. The stable isotope tracing method is helpful for determining the transport process of water and is expected to enhance our understanding of bioretention systems. The ratio of the event rainfall-runoff and the pre-event soil water in the bottom outflow of bioretention columns was calculated by the stable isotope bivariate mixing model based on the oxygen and hydrogen stable isotopic data from continuous testing in the discharge of bioretention column. The time-varying proportion of event water and pre-event water in the hydrographic curve reveals that the outflow process of soil water is divided into three stages. In the early stage, all the outflow was soil water, accounting for about 6–13% of the total outflow. In the middle stage, the proportion of soil water rapidly decreased from 100% to 20% within a few minutes. In the later stage, the soil water proportion decreased slowly from 20% to 0%. The outflow of soil water accounted for more than 36% of the total outflow and decreased with the extension of the drought period. Soil water is a critical part of the bottom outflow of bioretention columns, and the influence of soil water on the hydrological effect of bioretention columns cannot be ignored.

Low impact development (LID) is a sustainable land use and planning strategy that aims to minimize the environmental impacts of development. A community can enhance their water resources and create sustainable and resilient neighbourhoods. This approach has demonstrated success in managing stormwater and promoting water reuse globally, however, its suitability in developing countries like Indonesia remains uncertain and requires further investigation. The implementation of LID in developing countries may face several challenges including high density and complex drainage networks, combined sewer usage, clay soil type, irregular housing layouts, community socio-economic characteristics, affordability, cost, and the availability of regulations and policies. With proper planning and site-specific strategies, LID can be implemented effectively in Indonesia. Clear regulations, secured funding source and community-based LID are all essential for successful LID deployment. This paper can be used as a starting point for considering LID implementation in Indonesia and other countries with similar characteristics. HIGHLIGHTS The applicability of LID in developing countries like Indonesia remains uncertain and requires further investigation.; The implementation of LID in Indonesia faces several challenges including high-density and complex drainage networks, combined sewer usage, clayey soil type, irregular housing layouts, community socio-economic, affordability, and cost, coupled with the availability of regulations and policies.; With proper planning and site-specific strategies that address these challenges, LID can be implemented effectively in Indonesia.;

Low impact developments (LIDs) are control measures to restore the hydrologic regime and enhance stormwater quality. Due to LID's expensive capital and maintenance cost, the placement of LID controls in a watershed is an important planning task and still an open question in the specialized literature. This study proposes a simulation-optimization approach to place bioretention systems within a watershed to optimize their effectiveness. The Stormwater Management Model (SWMM) and the Non-dominated Sorting Genetic Algorithm III (NSGAIII) were coupled to identify the near-optimal locations of bioretentions for near-optimal quality and quantity controls, considering runoff volume, peak flow, total suspended solids, total nitrogen, and cost. Trade-offs were identified between cost versus other objective functions. The results suggest no specific spatial preference in placement of bioretentions under different rainfall regimes in watershed scale. However, in subcatchment scale, the near-optimal placement under single storm events is either maximum or none, while distributed under continuous simulation. [ABSTRACT FROM AUTHOR]

Bioretention facilities are one of the most widely used measures for urban stormwater control and utilization. In this study, the accumulation characteristics of polycyclic aromatic hydrocarbons (PAHs) in bioretention facilities and the effects of PAHs on the structure of microbial communities were explored by combining on-site monitoring and water distribution simulation experiments. The correlation between pollutant accumulation and dominant microorganisms in the bioretention systems was also clarified. The results showed that all 16 priority PAHs were detected in the bioretention facilities in the sponge city pilot area. The PAH concentrations in the soil during the non-rainy season were higher than those in the rainy season and medium- and high-ring PAHs dominated. PAHs in the study area were mainly derived from coal and biomass combustion. The potential carcinogenic risk of PAHs accumulated in the bioretention facilities in the study area was low. The microbial diversity during the non-rainy season was greater than that during the rainy season. Firmicutes, Bacteroidetes, Bacteroides, and Massilia were strongly correlated with naphthalene (NAP), pyrene (PYR), fluoranthene (FLT), and benzo[a]pyrene (BaP). According to the results of the small-scale water distribution test, the addition of PAHs had little effect on the decline in water quantity, and there was no significant regularity in the reduction of water quality including TP, NH4+-N, NO3—N, and TN. The addition of PAHs had a significant effect on the microbial community structure and an inhibitory effect on enzyme activity. [ABSTRACT FROM AUTHOR]

In order to verify the reliability of hydrologic regulation effect of HYDRUS-1D simulated bioretention facilities, the sensitivity of main parameters of the model was analyzed and screened by the modified Morris method through the physical model experiment, and the model parameters were calibrated by combining simulated and measured values. The results show that the output sensitive parameters of the total runoff, peak runoff and each reduction rate are different, which rainfall (q) are all highly sensitive parameters. The variation coefficient method was used to determine the comprehensive sensitivity degree of the parameters which main sensitive parameters include rainfall (q), aquifer height (H), as well as saturated water content ( θs ), saturated hydraulic conductivity (Ks ) and pore connectivity parameters ( n) of planting soil and filling layer. During the validation period, the maximum root mean square error (RMSE) of simulated and measured results is 0. 131, the relative error (RE) is lower than 6. 92%, and the Nash-Sutcliffe efficiency coefficient (NSE) and the coefficient of determination R 2 are both above 0. 9, indicating high matching degree and reliable simulation results. It providing theoretical support for improving the planning and design method of bioretention facilities by using HYDRAS-1D. [ABSTRACT FROM AUTHOR]

Microplastic removal from stormwater runoff from roads is necessary to reduce the effect of microplastic pollution in water bodies. Bioretention is a potential technology to remove microplastics in stormwater runoff from roads. A lab-scale experiment was conducted to determine the efficiency, effect on vegetation and discharge variation, and the kinetics of microplastic removal from stormwater runoff from roads using a bioretention cell. The experiment was done using an artificial sample based on visual characterization of stormwater runoff from highways, commercial, and residential roads. The vegetations that were examined were Vetivera sp. and Hibiscus sp. The operational discharge was varied based on rainfall intensity categories. The result showed that the removal efficiency was in the range of 92.4 to 99.3% with a mean of 97.2%. Statistical analysis (a = 5%) showed that variation in vegetation and discharge had no significant effect on microplastic removal using bioretention. The first-order kinetic analysis showed that the kinetic removal constant of the bioretention with Vetivera sp., bioretention with Hibiscus sp., and bioretention without vegetation was 0.0356, 0.034, and 0.0327, respectively. These results indicate that bioretention with Hibiscus sp. removed more microplastics at greater depths than with Vetivera sp. [ABSTRACT FROM AUTHOR]

This study using hexadecyl trimethyl ammonium bromide (HDTMA) modified zeolite as a component of bioretention substrate, to investigate the effect of HDTMA modification on the basic physical and hydraulic properties of substrate layer. Two different levels of HDTMA modified zeolite (ZHD10 and ZHD50) were mixed with a mixture consists of peat soil, river sand and compost (fixed volumetric proportion at 5:4:1) with varying volumetric percentage (25%, 50%, and 75%) to form substrate media. The modification only changes the physical properties of zeolite and media with zeolite slightly, while significant changes in surface hydrophobicity and hydraulic properties were observed. A distinct decline of saturated hydraulic conductivity ( K s ) values of zeolite can be observed after the modification, K s values drop 36.5% for ZHD10 and 55.1% for ZHD50. In contrast, K s values of substrate media using zeolite increase after the modification at the same volumetric ratio of zeolite. When 50% of zeolite (v/v%) was used in substrate, K s for natural zeolite, ZHD10 and ZHD50 was 0.024, 0.038 and 0.075 cm/s, respectively. Such alterations in K s are associated with the changes of surface hydrophobicity after the modification and ion exchange between modified zeolite and other materials after soaking into water. Changes in water retention characteristics (WRC) curves were in good accord with the variations in K s , and can be interpreted by the changed K s of tested materials. The orientations of HDTMA molecules loaded on zeolite surface were suggested to play crucial roles in altering the hydraulic properties of zeolite added substrate. [ABSTRACT FROM AUTHOR]

There has been a rapid development in studies of nature-based solutions (NbS) worldwide, which reveals the potential of this type of solution and the high level of interest in its implementation to improve the resilience of cities. Much relevant information and many important results are being published, and it is now possible to see their diverse benefits and complexity. Several authors highlight their role in urban areas not just in temperature control, but also in human health, ecosystem development and water management. However, in the current reality of cities, where water use is being (and will be) constantly challenged, analyzing NbS advantages for the urban water cycle is crucial. This study performed an intense review of the NbS literature from 2000 to 2021, to identify their contributions to the improvement of urban water cycle management and thus provide a solid information base for distinct entities (public institutions, private investors and the urban population in general) to disseminate, apply and justify their implementation. In general terms, the urban water cycle embraces not only the abstraction of water for urban consumption, but also its return to nature and all the stages in between, including water reuse and stormwater management. This review will highlight the important benefits that NbS in general, and green roofs in particular, provide to urban stormwater control, a key factor that contributes to urban sustainability and resilience in order to face future climate challenges. The novelty of the present review paper falls within the conclusions regarding the crucial role that NbS develop in urban water management and the main features that must be tested and technically enhanced to improve their functioning. [ABSTRACT FROM AUTHOR]

Bioswales are used to attenuate stormwater pollution, but their long-term sustainability regarding sequestered metals is relatively unknown, and a clear rationale for prioritizing soil management is lacking. Impervious areas draining into four 14-year-old suburban bioswales were delineated, for which surface soils (top 10 cm; 72 samples) were sampled; soils from 4 adjacent reference sites were also sampled. Total and water soluble metals (Cd, Cu, Pb, Zn) were quantified, and the relationships between metal concentrations and drainage area characteristics evaluated. Annual metal loads were estimated using regional runoff data to simulate current and future metal concentrations; risks to soil biota were assessed by comparing metal concentrations to ecological screening levels. The drainage areas' percent imperviousness (37-71%) and ratios of impervious drainage area to bioswale area (2.0-5.7) varied, owing to differing proportions of rooftops, paved surfaces, lawns, and natural soils. Total Cu and Zn ranged from 10.0 to 43.2 mg/kg dry soil, and 15.6 to 129.5 mg/kg dry soil, respectively. Across all bioswales, total Zn was positively correlated to percent impervious area (r = 0.32, p = 0.0073), the ratio of connected impervious drainage area to infiltration area (r = 0.32, p = 0.0073), and percent drainage area as paved surfaces (r = 0.46, p = 5.6 E-05), but negatively correlated to percent drainage area as lawns (r = -0.48; p = 2.4 E-05). Water soluble metal concentrations were orders of magnitude lower than total metals. Given annual metal loads (0.2-0.4 mg Cu/kg dry soil; 1.5-3.1 mg Zn/kg dry soil), replacing bioswale soils to constrain metal concentrations would be unnecessary for decades. Taken together, this study proposes a transferable approach of estimating, then verifying via sampling and analysis, bioswale soil metal concentrations, such that soil management decisions can be benchmarked to ecological screening levels.

Urban stormwater management has become a major issue over the last decades for flood prevention as well as water resource preservation. The development of green infrastructures such as bioretention systems since the 1990s has often been reported as an effective means of runoff mitigation with subsequent conveyed pollutant capture. Nevertheless, climate change involving more frequent extreme weather events as well as the variety of emerging pollutants in urban runoff have put an increasing strain on bioretention processes. Within this context, this mini-review deals with the opportunity of upgrading vegetated bioretention systems with active control technology to enhance their pollutant treatment capacity through proper control of critical bioretention operational variables and relying on improved ecological functioning and resilience. It is envisioned that such nature-based solutions hybridized with real-time control technology would help to improve stormwater reuse for more sustainable urban water management within the nexus of water–energy–food and greenhouse gases in future cities. HIGHLIGHTS Needs to enhance the capacity of soluble pollutant retention by current bioretention cells.; Real-time control of bioretention cells as a promising way to improve biofiltration performances.; Real-time control of soil moisture level to foster ecological functioning, bioremediation and ecosystem resilience of bioretention cells.; Healthier actively controlled bioretention ecosystems as a way to increase stormwater reuse.;

Bioretention cells, or rain gardens, can effectively reduce many contaminants in polluted stormwater through phytoremediation and bioremediation. The vegetated soil structure develops bacterial communities both within the soil and around the vegetation roots that play a significant role in the bioremediative process. Prediction of a bioretention cell's performance and efficacy is essential to the design process, operation, and maintenance throughout the design life of the cell. One of the key hurdles to these important issues and, therefore, to appropriate designs, is the lack of effective and inexpensive devices for monitoring and quantitatively assessing this bioremediative process in the field. This research reviews the available technologies for biomass monitoring and assesses their potential for quantifying bioremediative processes in rain gardens. The methods are discussed based on accuracy and calibration requirements, potential for use in situ, in real-time, and for characterizing biofilm formation in media that undergoes large fluctuations in nutrient supply. The methods discussed are microscopical, piezoelectric, fiber-optic, thermometric, and electrochemical. Microscopical methods are precluded from field use but would be essential to the calibration and verification of any field-based sensor. Piezoelectric, fiber-optic, thermometric, and some of the electrochemical-based methods reviewed come with limitations by way of support mechanisms or insufficient detection limits. The impedance-based electrochemical method shows the most promise for applications in rain gardens, and it is supported by microscopical methods for calibration and validation. [ABSTRACT FROM AUTHOR]

Climate change represents a paramount challenge for humanity in the 21st century. Green infrastructure (GI), due to its myriad environmental and societal benefits, has emerged as an essential natural life support system and a pivotal strategy to combat climate change-induced risks. Consequently, GI has garnered considerable global interest. As of now, comprehensive and systematic environmental impact assessments of GI are underway worldwide. Nonetheless, there remains a conspicuous scarcity of life-cycle approaches to delineate the evolutionary trajectory of this domain. Employing three bibliometric software tools—the R language "Bibliometrix" package (version 4.0.1), CiteSpace (version 6.2.R2 Basic), and "VOSviewer" (version 1.6.18)—this study scrutinizes the progression of the GI paradigm until 2022. An exhaustive review of 1124 documents published on the Web of Science between 1995 and 2022 facilitates an overarching evaluation of GI, encompassing environmental, economic, and social facets from a life-cycle standpoint. The analysis results reveal that (1) the majority of current studies accentuate the economic and environmental efficacy of GI throughout its life cycle, with the social performance receiving comparatively less focus, potentially due to the difficulties in formulating a social life-cycle-assessment database; (2) contemporary research predominantly concentrates on the life-cycle carbon footprint of GI, warranting further exploration into its water and carbon footprints; and (3) multi-objective optimization emerges as a promising avenue for future GI investigations. This review thus furnishes a comprehensive understanding of the performance of GI from a life-cycle perspective. [ABSTRACT FROM AUTHOR]

In recent years, as a result of intensive urbanisation, a significant increase in the surface of impermeable areas has been observed, which results in changes in the hydrological cycle of catchments. In order to counteract these changes, low-impact development (LID) solutions are increasingly being implemented in urban catchments, including bioretention systems. Taking this into account, a new bioretention drainage channel (BRC) was designed, whose main task is retention, infiltration, and pre-treatment of rainwater. The pilot laboratory tests carried out on two BRC prototypes (K1 and K2) showed that the average rate of reduction of mineral-suspended solids from rainwater was 69% and 57%, respectively, for K1 and K2. Analysing the results of the research, it was found that the bioretention drainage channel is characterised by very high efficiency in removing petroleum hydrocarbons from rainwater, and the reduction rate of these pollutants for both the K1 and K2 channels was close to 100%. In turn, hydrodynamic studies carried out on the model of the urban catchment showed that the implementation of BRCs will reduce the peak runoff by more than 82%, and the maximum flow in the sewage network by 83%. [ABSTRACT FROM AUTHOR]

Bioretention is a typical low impact development (LID) practice that helps reduce peak urban stormwater runoff and runoff pollutant concentrations (e.g., heavy metals, suspended solids, organic pollutants), which has become an important part of urban stormwater management over the past 15 years. To understand the research hotspots and frontiers in the field of bioretention facility research and provide a reference for research into bioretention facilities, we conduct a statistical analysis of global bioretention literature published during 2007–2021 using the Web of Science core database and the data visualization and analysis software VOSviewer and HistCite. The number of published articles related to bioretention facilities shows a rising trend over the study period, with research from China contributing greatly to global research on bioretention facilities. However, the influence of articles needs to be increased. Recent studies mainly focus on the hydrologic effect and water purification effect of bioretention facilities and on the removal of nitrogen and phosphorus nutrients from runoff rainwater. Further studies should focus on the interaction of fillers, microorganisms, and plants in bioretention facilities and its impact on the migration, transformation, and concentrations of nitrogen and phosphorus; the purification effect and mechanism of specific emerging contaminants in runoff; the selection and configuration optimization of filler materials and plant species; and the optimization of the design parameters of the model for bioretention systems. [ABSTRACT FROM AUTHOR]

Non-point source pollution from rainwater runoff presents a serious challenge for urban water management in many cities undergoing urbanization and experiencing climate change. To alleviate water resource conflicts in Changsha, China, this study comprehensively evaluated the pollution characteristics and first flush effect (FFE) of runoff from asphalt roads and colored steel plate roofs under seven rainfall events in April–May 2022. The runoff was collected and purified using bioretention ponds. The results showed that the peak runoff pollutant concentrations occurred within the first 20 min of runoff generation and then decreased to relatively stable levels, with maximum total suspended solids (TSS) concentration and chemical oxygen demand (CODCr) reaching 873.5 and 207.32 mg/L, respectively, for road runoff and 162 and 73.31 mg/L for roof runoff, respectively. The main pollutants were TSS and CODCr, followed by ammonia nitrogen (NH4+-N), nitrate nitrogen (NO3−-N), total phosphorus (TP), and nitrite nitrogen (NO2−-N). Concentrations of pollutants and FFE for roof runoff were lower than those for road runoff. Road runoff had a more obvious FFE for TP and NH4+-N, whereas the roof runoff showed the presence of TP and NO3−−N. An important implication is that treating the first 30% of surface runoff from rainfall events with long antecedent dry days or high rainfall amounts is necessary to improve water quality before discharge or utilization. The study also found that road and roof runoff, after treatment with bioretention ponds, exhibit good water quality, thus, allowing their use as reclaimed water or for miscellaneous purposes in urban areas. Overall, this study provides useful information for designing management measures to mitigate runoff pollution and reuse in Changsha. [ABSTRACT FROM AUTHOR]

We conducted a column study to better understand the relative effects of plants, design elements, and operating conditions on pollutant removal in stormwater biofilters in southern California under local conditions. We planted five southern California native species (Baccharis pilularis, Carex praegracilis, Juncus patens, Leymus condensatus, and Muhlenbergia rigens) in experimental biofilter columns fitted with a saturated zone and evaluated pollutant removal during weekly dosing and following a 52-day dry period. Columns planted with C. praegracilis and J. patens were also evaluated under conditions of fortnightly dosing and without the presence of a saturated zone. During weekly dosing, planted columns had a total nitrogen removal efficiency of 46% on average whereas removal was 8% in unplanted columns. B. pilularis and M. rigens performed better than other species at nitrogen removal. The presence of a saturated zone improved nitrogen removal and metal removal, but only before the 52-day dry period. With a few exceptions, local best management practice effluent concentrations limits were exceeded but performed similarly to existing southern California biofilters. Nitrogen removal decreased slightly under a fortnightly dosing frequency, which better represented rainfall event frequency in Los Angeles when compared to weekly dosing.

Bioretention is commonly used for runoff pollution control. The first flush strength of pollutants can affect bioretention performance. To examine the influence of the first flush strength on bioretention performance, bioretention columns filled with garden soil as the main media were established. Activated carbon and water treatment residuals (WTR) were added and compared for their ability to enhance phosphorus removal. Waste edible fungus culture medium (WEFCM) as a carbon source was also explored. When WEFCM was used as a carbon source instead of wood chips, total nitrogen (TN) removal increased from 60.83 ± 21.22 to 62.21 ± 16.43%, but chemical oxygen demand (COD) leaching was observed. WTR was better able than activated carbon to enhance phosphorus removal (87.97 ± 8.87 vs. 81.66 ± 9.27%) without impacting TN removal. NH4+-N removal increased with increasing first flush strength, but there was no trend for suspended solids (SS), COD, TN, or total phosphorus. First leaching phenomenon in bioretention outflow was proposed in this study. A low first leaching was observed in the outflow when the inflow had a uniform pollutant mass (i.e., no first flush) because of media leaching. A weak first leaching outflow was observed for SS and COD when they were present at strong first flush inflow. HIGHLIGHTS Waste edible fungus culture medium can be used as a carbon source instead of wood chips.; Water treatment residuals enhanced P removal better than activated carbon at the same volume ratio.; NH4+-N removal increased with increasing first flush strength, but SS, COD, TN, and TP did not.; A strong SS and COD first flush inflow led to considerable first leaching mitigation effect in the outflow.;

【Objective】 Bioretention is a method to purify water, and the aim of this paper is to study its effect on stormwater runoff. 【Method】 We took stormwater runoff in Shijiazhuang city as an example, investigating the outflow characteristics of the bioretention system in response to two rainfall patterns, constant pattern and Chicago pattern using column experiment and HYDRUS model. From the simulated results, we analyzed and discussed the sensitivities of the runoff to soil hydraulic parameters, catchment area and thickness of the planting soil layer. We also developed a model to predict the influence of rainfalls with different return periods (N) on outflow. 【Result】 Compared to constant rainfall, the Chicago rainfall pattern delayed the emergence of outlet-outflow and prolonged the ponding duration on the soil surface. The hydraulic parameters to which the runoff was sensitive include saturated soil permeability Ks, saturated soil water content θs, and the empirical parameter α in the van Genuchten formula. An increase in Ks increased the maximum outlet-drainage rate and brought forward its arrival time. Increasing θs prolonged the latent time and reduced the outflow rate and ponding duration. Increasing the parameter α resulted in an increase in outflow. Doubling the catchment area ratio increased the maximum drainage rate, the peak-reduction rate and ponding duration by 13%, 33% and 300%, respectively, whereas reducing the latent time by 16%. Change in thickness of the planting soil layer did not show a significant effect on the outflow pattern. 【Conclusion】 The bioretention system is more permeable with more than 90% of rainwater flowing through the planting soil layer. When the return period of the rainfall is no more than 5 years, there is no overflow with the peak reduction rate being 40.6%~76.5%, the latent time > 1 h and ponding time < 2 h.

Bioretention is widely used in urban sustainable stormwater management; however, limited numerical research has been conducted on its performance in cold regions, particularly for winter snowmelt, spring runoff and summer large storms (>50 mm) for urban flood mitigation. In this study, HYDRUS 1D was used to explore these knowledge gaps. The model was comprehensively calibrated and validated against 2‐year hydrologic and water quality data of four bioretention columns with different designs under lab‐simulated cold region conditions. The Morris method was used to measure the sensitivity and interaction of the calibrated hydraulic parameters. The model revealed that the effective hydraulic conductivity (KS) values of the soil media were similar for winter snowmelt and spring runoff when the soil temperature was around −0.5°C. Preferential flow is likely to occur in soil media during winter or spring in cold regions. The summer modelling showed that bioretention could substantially reduce peak flow, ponding depth and duration for large storm events (even for a 1:100 local storm with 83.4 mm in 4 h). The water quality modelling confirmed experimental results that the bioretention effectively removed phosphate and ammonium but had leaching issues for chloride and nitrate. Finally, optimization and recommendations for bioretention columns were provided. [ABSTRACT FROM AUTHOR]

Bioretention cells (BRCs) are a promising low-impact development (LID) practice that are commonly used in urban settings to improve the water quality and mitigate the hydrological effects of stormwater runoff. BRCs have been the subject of extensive research in order to better comprehend their function and improve their effectiveness. However, BRC performance differs greatly among regions in terms of hydrologic performance and quality enhancement. Due to this variance in BRC effectiveness, the current study conducted a comprehensive systematic review to answer the question, "Are BRCs an effective LID method for urban catchment stormwater management?". This review study analyzed the effectiveness of BRCs in mitigating hydrologic impacts and enhancing the quality of stormwater runoff in urban catchments. A review of 114 field, laboratory, and modeling studies on BRCs found that the promising BRCs may be one of the most successful approaches to restore urban hydrology cycle and improve stormwater water quality. With further development of BRCs, their performance in terms of quantity and quality will become more reliable, helping to develop long-term solutions to stormwater urban drainage issues. At the end of this review, the knowledge gaps and future prospects for BRC research are presented. In addition to providing a foundational grasp of BRC, this review study outlines the key design recommendations for BRC implementation in order to address the issues raised by certain BRC design errors. [ABSTRACT FROM AUTHOR]

BRCs (bioretention cells), one of many low-impact development (LID) practices, are increasingly utilized to lessen the amount of runoff while simultaneously improving the runoff quality. Because the goal of BRCs and LID designs, in general, is to mimic or replicate the pre-development hydrology, it is critical to evaluate the hydrologic and ecologic performances of the BRC facility from the perspective of replicating the pre-development hydrology. The metrics developed in this study were intended to represent the hydrologic regime including the runoff volume control metrics, peak flow frequency exceedance curve, and flow duration curve. We also used a hydrological indicator of T0.5, the fraction of a multi-year period in which the flow exceeds the 0.5-year return period storm to represent the performances regarding downstream ecology. The indicators were compared to their pre-development values to determine how closely they reflected and replicated the pre-development state. A long-term stormwater management model (SWMM) model was developed to examine conditions before and after development and water movement in BRCs. When the BRCs facilities areas are 5% of the entire impervious study area, key findings show that: (1) BRCs have significant runoff volume control performances. (2) The peak flow frequency exceedance curve with BRCs could fully match the pre-development scenario for minor rainfall events compared to the 0.1-year storm. Flow duration curves with BRCs showed that, the frequency, magnitude, and duration of small flows that occurred for more than 90% of the total time closely matched those of pre-development hydrology. (3) T0.5 with BRCs showed significant improvement compared with the value of the area with no BRCs and was close to the pre-development T0.5. The findings presented in this study indicated the significant performance of BRCs in improving downstream ecology. [ABSTRACT FROM AUTHOR]

Bioretention systems are among the most popular stormwater best management practices (BMPs) for urban runoff treatment. Studies on plant performance using bioretention systems have been conducted, especially in developed countries with a temperate climate, such as the USA and Australia. However, these results might not be applicable in developing countries with tropical climates due to the different rainfall regimes and the strength of runoff pollutants. Thus, this study focuses on the performance of tropical plants in treating urban runoff polluted with greywater using a bioretention system. Ten different tropical plant species were triplicated and planted in 30 mesocosms with two control mesocosms without vegetation. One-way ANOVA was used to analyze the performance of plants, which were then ranked based on their performance in removing pollutants using the total score obtained for each water quality test. Results showed that vetiver topped the table with 86.4% of total nitrogen (TN) removal, 93.5% of total phosphorus (TP) removal, 89.8% of biological oxygen demand (BOD) removal, 90% of total suspended solids (TSS) removal, and 92.5% of chemical oxygen demand (COD) removal followed by blue porterweed, Hibiscus, golden trumpet, and tall sedge which can be recommended to be employed in future bioretention studies. [ABSTRACT FROM AUTHOR]

Stormwater mitigation efficiency of bioretention systems relies for a large part on their capacity to infiltrate rapidly received runoff. Within this context, the primary aim of this literature review was to clarify the vegetation influences on bioretention media hydraulic conductivity, with the ultimate goal of improving guidance on plant choice for system durability. A thorough synthesis of studies dealing with the comparison of plant species, functional types, or traits on infiltration-related processes in biofilters was achieved. Overall, results converged to a positive impact of plants on water infiltration and percolation, either under greenhouse or field conditions. In most cases, vegetation selection had a determining role in maintaining initial media infiltration rates, with in terms of improvement: turfgrass < prairie grass < shrubs < trees. Wind-induced movements of rigid foliage or stems are believed to avoid complete surface clogging. Species with thick, rhizomatous or fleshy (with maximum root diameter near the centimeter range), and tap or deep root systems could be preferred to maximize infiltration rates in permeable bioretention media. In fine-textured soils, higher specific root length, root length density, or mass density could also enhance infiltration. Root mass densities (0.1–2.2 kg.m3) were positively linked with infiltration rates in unlined systems while roots around 1 mm diameter would favor macropore-related preferential flows and increased hydraulic conductivity. Finally, implementation of high-diversity plant communities would ensure the presence of a more functionally rich vegetation community with species possessing adequate physiological adaptations (including root system architecture) to local environmental conditions for perennial cover and proper bioretention hydrological functioning. [ABSTRACT FROM AUTHOR]

Recently, biochar with persistent free radicals has widely been applied to the removal of nutrient in bioretention cells. However, there is a lack of information on hydrogen peroxide (H2O2) levels in biochar-based bioretention cells with three environmental conditions and its potential risks. In this study, batch experiments were used to investigate H2O2 levels in biochar-based bioretention cells with different weight ratios of sand to biochar (S/B), hydraulic loading rate (HLR) and antecedent dry period (ADP). Potential risks of H2O2 on dominant community were also explored. Results showed that H2O2 levels in bioretention cells with 9:1, 8:2 and 7:3 of S/B were significantly high with the range from 0.024 to 0.044 mmol/L, and the production decreased with the increasing contents of biochar. Furthermore, H2O2 levels in three different heights of substrate layers and the bottom outlet enhanced with the rise of HLR, where the amplification of H2O2 in the middle layer was the largest, reaching 438.5% (ratio of H2O2 level at 2.0 m3/m2/d of HLR to the one at 0.4 m3/m2/d of HLR). In contrast, the long ADP was unfavorable to H2O2 levels in biochar-based bioretention cells. The production of H2O2 resulted in the change of dominant microflora (Bacteroidetes and Firmicutes), and the dosage of biochar could be the key. Altering these mentioned factors to achieve the regulation of microbial community structure in bioretention cells with biochar could be one of the promising approaches for the improvement of biological degradation function. [ABSTRACT FROM AUTHOR]

Exfiltration type bioretention can collect rainwater runoff to recharge groundwater, but the water diffusion in the in-situ soil can have an impact on the foundation of adjacent structures (such as roads). Generally, the existing studies are primarily focused on the exfiltration of bioretention as an index of runoff control or the water balance. However, research is lacking on the diffusion characteristics of soil water content in different in-situ soils. Therefore, in this study, the VADOSE/W model was used to simulate the water transport process of bioretention ponds and in-situ soils, under long-term rainfall. The water diffusion characteristics of four in-situ soils were studied: silt loam (SL), loam (L), sandy clay loam (SCL), and sandy loam (SaL). The results showed that under 12 rainfall events, with a monthly maximum rainfall of 268 mm in the study area, for four in-situ soil types, the bioretention pond's bottom exfiltration volume per unit area reached 3.93-7.91 times that of the lateral. The order of bottom exfiltration volume was SaL>SCL>L>SL. Over time, the in-situ soil water content fluctuated with rainfall events. The order water content was usually SL>L>SCL>SaL, and the water diffused into the in-situ soil was distributed in a symmetrical arc along the horizontal direction. After rainfall events, at depths of 1, 3 and 5 m, for SL, L, SCL, and SaL soils, the lateral water diffusion ranges were ~1.25-1.47 m, ~1.23-1.45 m, ~1.22-1.77 m, and ~1.46-1.60 m, respectively. With a continuous supply of water, the horizontal diffusion distance of each in-situ soil tended to be the same, although the water diffusion range of SCL was relatively larger. Therefore, when an exfiltration type bioretention area is designed, the distance between the bioretention edge and the adjacent structures should be longmore than 2 m to avoid nearby structural foundations being negatively affected by water seepage over a long period of time. [ABSTRACT FROM AUTHOR]

Retrofitting urban watersheds with wireless sensing and control technologies will enable the next generation of autonomous water systems. While many studies have highlighted the benefits of real-time controlled gray infrastructure, few have evaluated real-time controlled green infrastructure. Motivated by a controlled bioretention site where phosphorus is a major runoff pollutant, phosphorus removal was simulated over a range of influent concentrations and storm conditions for three scenarios: a passive, uncontrolled bioretention cell (baseline), a real-time controlled cell (autonomous upgrade), and a cell with soil amendments (passive upgrade). Results suggest the autonomous upgrade matched the pollutant treatment performance of the baseline scenario in half the spatial footprint. The autonomous upgrade also matched the performance of the passive upgrade; suggesting real-time control may provide a 'digital' alternative to existing, passive upgrades. These findings may help site- and cost-constrained stormwater managers meet their water quality goals. [ABSTRACT FROM AUTHOR]