Integrated hydro-environmental impact assessment and alternative selection of low impact development practices in small urban catchments

A bioretention system is a low-impact and sustainable treatment facility for treating urban stormwater runoff. To meet or maintain a consistently satisfactory performance, especially in terms of increasing nitrogen removal efficiency, the introduction of a submerged (anoxic) zone (SZ) combined with a module-based carbon source (C) has been recommended. This study investigated the removal of nitrogen (N), phosphorus (P) and heavy metals with a retrofitted bioretention system. A significant (p < 0.05) removal enhancement of N as well as total phosphorus (TP) was observed, in the mesocosms with additions of exogenous carbon as opposed to those without such condition. However, even in the mesocosm with SZ alone (without exogenous C), TP removal showed significant enhancement. With regard to the effects of SZ depth on nutrient removal, the results showed that the removal of both N and P in module with a shallow SZ (200 mm) showed significant enhancement compared to that in module with a deep SZ (300 mm). Removal efficiencies greater than 93% were observed for all three heavy metals tested (Cu, Pb, and Zn) in all mesocosms, even in the bioretention module without an SZ or plants, and it indicated that adsorption by the filtration media itself is probably the most important removal mechanism. Only Cu (but not Pb or Zn) showed significantly enhanced removal in module with an SZ as compared to those without an SZ. Carbon source played a minor role in metal removal as no significant (p > 0.05) improvement was observed in module with C as compared to that without C. Based on these results, the incorporation of SZ with C in stormwater biofilters is recommended.of water irreversibly degraded [3,4]. Bioretention cells (BCs) integrated runoff retention areas, is a critical component of Low Impact Development (LID) practices receiving high attention as "green storm infrastructure" to manage storm runoff in a decentralized and source management approach [5,6]. BCs have gained popularity because of its design flexibility in terms of size and location, appealing landscape aesthetics, and hydrological performance for reduction of pollutants [7,8]. Previous studies have demonstrated that BCs implemented in relatively small catchments effectively improve both water quantity and quality in response to frequent storm events [9][10][11].In the vegetated filter media, pollutants from storm runoff can be removed through a variety of mechanisms, including physical, chemical and biological processes [12][13][14], and its quality is further enhanced by plant uptake and biological activities in the rhizosphere [15,16]. In recent years, research has shown that BCs can effectively improve water quantity and remove suspended solids [17,18], nutrients [19][20][21], and heavy metals [22,23]. However, it is difficult to meet or maintain a consistently satisfactory performance for reducing nitrogen due to a lack of effective denitrification [24,25].Since it is difficult to achieve consistent high nitrogen removal in standard stormwater bioretention s...

mentioning

confidence: 99%

Effect of a Submerged Zone and Carbon Source on Nutrient and Metal Removal for Stormwater by Bioretention Cells

Wang

Zhang

et al. 2018

“…These changes directly lead to changes in the previous infiltration processes, thereby altering the natural hydrological water cycle. The changes to the surface runoff characteristics of these areas include larger runoff volume, higher peak runoff, earlier peak runoff time, and poorer water quality [1][2][3][4]. Of these impacts, urban flood disasters have appeared more frequently, which increasingly threatens people's lives and health, resulting in huge economic losses.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Sponge City Construction for Reducing Directly Connected Impervious Areas on Hydrological Responses at the Urban Catchment Scale

Liang

Zhang

Xia

et al. 2020

Low-impact development (LID) has been widely used at both site-specific and local scales to try and mitigate the impact of urban stormwater runoff caused by increasing impervious urban areas. Recently, the concept of a “sponge city” was proposed by the Chinese government, which includes LID controls at the source, a pipe drainage system midway, and a drainage system for excess stormwater at the terminal. There is a need to evaluate the effectiveness of sponge city construction at the large urban catchment scale, particularly with different spatial distributions of LIDs that reduce directly connected impervious areas (DCIAs). In this paper, the performances of five design scenarios with different spatial distributions but same sizes of LID controls at the urban catchment scale were analyzed using a geographic information system (GIS) of the United States Environmental Systems Research Institute (ESRI)—based Storm Water Management Model (SWMM) of the United States Environmental Protection Agency (USEPA) and MIKE 11 of Danish Hydraulic Institute (DHI) in Xining City, China. Results confirmed the effectiveness of sponge city construction in reducing the urban stormwater runoff. The hydrological performance reduction was positively correlated and linearly dependent on DCIA reduction. Peak flow reduction was most sensitive to DCIA reduction, followed by runoff volume and peak time. As rainfall intensity increased, the hydrological performance was more sensitive to rainfall intensity than DCIA reduction. Results of this study provide new insights for stormwater managers to implement LID more effectively at the urban catchment scale.

“…To mitigate the negative impact of urbanization on regional hydrology and environment, different initiatives or plans have been made worldwide, such as Low Impact Development (LID) or Best Management Practices (BMP) in the US [1], Sponge City construction plan in China [2][3][4], and Sustainable Urban Drainage System (SUDS) and Green Infrastructure in UK [5,6]. These plans all include building 'Green Infrastructures', or GIs [7,8] to decentralize stormwater management.…”

Section: Introductionmentioning

confidence: 99%

“…However, city LPs vary considerably in land use, constructing GIs to reach the same storm runoff mitigation goal would result in different levels of difficulty in different LPs. Theoretically, it is possible to design GIs to make all LPs to meet the mitigation requirement [3,[21][22][23], but this may not be economically feasible. The sponge city construction guideline of China set lower standards for some LPs with GI construction difficulty [4]; such compromises, however, will have a negative effect on the overall compliance of building mitigation GIs.…”

Section: Introductionmentioning

confidence: 99%

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Achieving Urban Stormwater Mitigation Goals on Different Land Parcels with a Capacity Trading Approach

Jia

Tang

et al. 2019

Building Green Infrastructures (GIs) to reduce stormwater runoff has been recognized as an effective approach to mitigate the negative impact of urban sprawl. Due to the significant differences in urban land use, some Land Parcels (LPs) may have difficulty in building enough GIs to meet stormwater mitigation goals. In this paper, we proposed a Capacity Trading (CT) approach that allows some LPs to trade their extra runoff retention capacities with LPs that have building difficulties, so that they can jointly reach the overall mitigation goal together. The rationale behind CT is that, to avoid potential penalties, it may be more economical for some LPs to ‘buy’ credit rather than to ‘build’ GIs. A case study was used to demonstrate CT operations for two trading scales: (1) CT within neighboring LPs (i.e., CT-1), and (2) CT within 20 m-radius LPs (i.e., CT-2). A GI implementation baseline intensity was set up firstly by treating the whole study area as one entity to reach a specified stormwater runoff control target; individual LPs were then examined for their GI building capacities, which may be deficit or surplus against the target. Results showed that the number and area of deficit LPs were reduced significantly through either CT scales; the number of deficit LPs was reduced from 139 to 97 with CT-1 and 78 with CT-2, and the deficit area was reduced from 649 ha to 558 with CT-1 and 478 ha with CT-2, respectively. The proposed method assumes LPs as the basic planning unit and encourages some stakeholders to maximize their GI building potential to compensate for those with disadvantages. The economic incentives for conducting CT among different LPs in urban area can help achieve stormwater mitigation goals more economically and flexibly. Some coordination among LPs in GI implementation is necessary, which presents both opportunities and challenges for city management.