Abstract
Growing concerns about urban runoff pollution and water scarcity caused by urbanization have prompted the application of bioretention facilities to manage urban stormwater. The purpose of this study was to evaluate the performance of proposed bioretention facilities regarding road runoff pollutant removal and the variation characteristics of the media physicochemical properties and microbial diversity in dry-cold regions. Two types of bioretention facilities were designed and then constructed in Tianjin Eco-city, China, on the basis of combined soil filter media screened by a laboratory-scale test with a modified bioretention facility (MBF) containing soil moisture conservation ropes. Redundancy analysis was performed to evaluate the relationships between the variation in media physicochemical properties and microbial communities. An increase in media moisture could promote an increase in the relative abundance of several dominant microbial communities. In the MBF, the relatively low nitrate-nitrogen (NO3-N) (0.75 mg/L) and total nitrogen (TN) (4.71 mg/L) effluent concentrations, as well as better removal efficiencies for TN and NO3-N in challenge tests, were mainly attributed to the greater relative abundance of Proteobacteria (25.2%) that are involved in the microbial nitrogen transformation process. The MBF also had greater media microbial richness (5253 operational taxonomic units) compared to the conventional bioretention facility and in situ saline soils. The results indicate that stormwater runoff treated by both bioretention facilities has potential use for daily greening and road spraying. The proposed design approach for bioretention facilities is applicable to LID practices and sustainable stormwater management in other urban regions.
Highlights
With rapid urbanization, there has been a significant increase in impermeable surface areas such as urban roads and roofs, resulting in an increase in surface runoff and leading to environmental problems such as runoff pollution and water environment deterioration [1]
The results indicated that the concentrations of chemical oxygen demand (COD), total nitrogen (TN), NH3 -N, and NO3 -N showed decreasing trends to varying extents, while total phosphorus (TP) and total suspended solids (TSS) showed fluctuating upward trends
Previous literature studies concluded that amendments in the filter media such as water treatment residual (WTR) and zeolite can help to remove TP and CODCr from the runoff [29,44]
Summary
There has been a significant increase in impermeable surface areas such as urban roads and roofs, resulting in an increase in surface runoff and leading to environmental problems such as runoff pollution and water environment deterioration [1]. It can be seen that the runoff indicators of total suspended solids (TSS), chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) for roads are worse than those for other land cover types. This is mainly due to frequent traffic activities, automobile exhaust emissions, tire wear, and the corrosion of components, which lead to the accumulation of a large number of pollutants such as suspended particulate matter, nutrients, and organic matter on road surfaces. The control of road runoff pollution is of great significance to urban runoff pollution control and ecological environmental protection
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