Remediation of Stormwater Pollutants by Porous Asphalt Pavement

Mitigating tire wear particles and tire additive chemicals in stormwater with permeable pavements

6PPD-quinone (6PPDQ) is a recently discovered chemical that is acutely toxic to coho salmon (Oncorhynchus kisutch) and can form via environmental exposure of 6PPD, a compound found extensively in tire wear particles (TWPs). TWPs deposited on roads are transported to aquatic ecosystems via stormwater, contributing to microplastic pollution and organic contaminant loads. However, little is known about the fate of TWPs and their leachable contaminants in these systems. We conducted three experiments at a high school in Tacoma, Washington, to quantify the treatment performance of permeable pavement (PP) formulations, a type of green stormwater infrastructure (GSI), for TWPs and ten tire-associated contaminants, including 6PPDQ. The PPs comprised concrete and asphalt, with and without cured carbon fibers, to improve the mechanical properties of PPs. Pavements were artificially dosed and had underdrains to capture effluent. Three experiments were conducted to evaluate PP mitigation of tire-associated pollution using cryomilled tire particles (cTPs). The 1st and 3rd experiments established a baseline for TWPs and contaminants and assessed the potential for continued pollutant release. During experiment 2, cTPs were applied to each pavement. Our results showed that the PPs attenuated >96 % of the deposited cTPs mass. An estimated 52-100 % of potentially leachable 6PPDQ was removed by the PP systems between the influent and effluent sampling stations. Background 6PPDQ concentrations in effluents ranged from 0 to 0.0029 μg/L. Effluent 6PPDQ concentrations were not explained by effluent TWP concentrations in experiments 1 or 2 but were significantly correlated in experiment 3, suggesting that leaching of 6PPDQ from TWPs retained in the pavement was minimal during a subsequent storm. Our results suggest that PPs may be an effective form of GSI for mitigating tire-associated stormwater pollution. The improved strength offered by cured carbon fiber-amended pavements extends PP deployment on high-traffic roadways where tire-associated pollution poses the greatest environmental risk.

Permeable pavements: A possible sink for tyre wear particles and other microplastics?

In this study, seven roads and parking lots were sampled by a road surface cleaning truck and approximately 100 kg of particulate material was collected per site. Thereafter, the samples were analysed for microplastics, including tyre wear particles. The analyses revealed that tyre wear constituted 0.09 % of the dry mass of the samples on average. Other plastic types were also identified in the samples, but at on average 49 times lower concentrations compared to tyre wear particles. Although the roads and parking lots were used for residential, industrial, and commercial purposes, no correlation between land use and the total concentrations of microplastics was identified. Of microplastics other than tyre wear particles, polypropylene constituted an important fraction in all samples, whereas other polymers were present at various degrees. The contents of heavy metals, sulphur, and total organic carbon were also measured in the samples, but no correlation between them and microplastics was determined. A back-of-the-envelope estimation indicated that the tyre wear material retained by permeable pavements constituted a non-negligible fraction of the total mass of microplastics released on roads and parking lots. Therefore, permeable pavements can serve as a tool for the management of this pollutant.

Performance synergism of pervious pavement on stormwater management and urban heat island mitigation: A review of its benefits, key parameters, and co-benefits approach

Pervious pavement system (PPS) is a suitable alternative technique for mitigating urban flooding and urban heat island (UHI) simultaneously. However, existing literature has revealed that PPSs cannot achieve the expected permeability and evaporation. To overcome this gap, this study presents an elaborate review of problems associated with PPSs and highlights its benefits to stormwater management and UHI mitigation. We determined key parameters of PPSs that could influence urban flooding and UHI mitigation, including hydrological properties, thermal physical properties, structure design, and clogging resistance. We identified the co-benefits approach of PPS towards performance synergism on stormwater management and UHI mitigation from quality controlled design and fabrication, periodic maintenance, and effective evaluation system based on practice environments. The results indicate that existing studies of PPSs primarily focus on permeability, while little emphasis is given to the evaporative cooling performance, leading to a biased development with a loss of test standards and regulations that cannot control the cooling potential of the system. The performance synergism of permeability and evaporative cooling in PPS should be studied further, while considering quality control of the materials and in-situ practice design. Parameter controls (with commonly used standards) during fabrication, periodic maintenance (during operation), and pre- and post-evaluation processes of PPSs should work collectively to achieve optimal benefits and reduced costs.

Loading, transport, and treatment of emerging chemical and biological contaminants of concern in stormwater

Stormwater is a largely uncontrolled source of pollution in rural and urban environments across the United States. Concern regarding the growing diversity and abundance of pollutants in stormwater, as well as their impacts on water quality, has grown significantly over the past several decades. In addition to conventional contaminants like nutrients and heavy metals, stormwater is a well-documented source of many contaminants of emerging concern, which can be toxic to both aquatic and terrestrial organisms and remain a barrier to maintaining high quality water resources. Chemical pollutants like pharmaceuticals and personal care products, industrial pollutants such as per- and polyfluoroalkyl substances, and tire wear particles in stormwater are of great concern due to their toxic, genotoxic, mutagenic and carcinogenic properties. Emerging microbial contaminants such as pathogens and antibiotic resistance genes also represent significant threats to environmental water quality and human health. Knowledge regarding the transport, behavior, and the remediation capacity of these pollutants in runoff is key for addressing these pollutants in situ and minimizing ecosystem perturbations. To this end, this review paper will analyze current understanding of these contaminants in stormwater runoff in terms of their transport, behavior, and bioremediation potential.

Urban stormwater characterization, control, and treatment

This review summarizes over 280 studies published in 2019 related to the characterization, control, and management of urban stormwater runoff. A summary of quantity and quality concerns is provided in the first section of the review, serving as the foundation for the following sections which focus on the control and treatment of stormwater runoff. Finally, the impact of stormwater control devices at the watershed scale is discussed. Each section provides a self-contained overview of the 2019 literature, common themes, and future work. Several themes emerged from the 2019 literature including exploration of substrate amendments for improved water quality effluent from stormwater controls, the continued study of the role of vegetation in green infrastructure practices, and a call to action for the development of new models which generate reliable, computationally efficient results under the physical, chemical, biological, and social complexity of stormwater management. PRACTITIONER POINTS: Over 280 studies were published in 2019 related to the characterization, control, and treatment of urban stormwater. Studies on bioretention and general stormwater characteristics represented the two most common subtopics in 2019. Trends in 2019 included novel substrate amendments, studies on the role of vegetation, and advancements in computational models.

Influence of filter layer positions and hydraulic retention time on removal of nitrogen and phosphorus by porous asphalt pavement

This study was aimed to investigate the removal processes of nitrogen (TN), NH₄ ⁺-N and phosphorus (TP) from surface runoff by performing experiments on the filter layers in porous asphalt pavement (PAP). Experiments were conducted to compare the differences of the filter layer placed at the top, the middle or the bottom of PAP. The effects of retention time on the removal of the pollutants and the adsorption capacity of PAP materials were also investigated. Results indicated that the filter layer placed under the bed course improved the removal rates of pollutants compared to the other two cases on the whole. The concentration of TP in the effluent decreased by 80% after the 48 h retention time. In conclusion, this study demonstrated that the positions of filter layers and the temporary retention time of surface runoff within the bed course of PAP were critical parameters for determining the removal processes of pollutants. Thus, a certain retention time for surface runoff in bed course is of great importance for PAP to serve as an effective low impact development technology for stormwater management.

Laboratory Evaluation of the Permeability Durability of Utilization of Oil Shale Waste as Fine Aggregate in Open Grade Friction Course in Seasonal Frozen Regions

Open graded friction course (OGFC), as a highly permeable mixture, has the characteristics of good friction and splash-and-spray reduction during rainstorms. The limitations of the use of such mixtures include the fact that they are affected by poor durability, including strength and permeability durability issues. In a previous study, oil shale waste, as a fine aggregate in the mixture (with a particle size less than 4.75 mm), could effectively improve the overall properties of OGFC, but the permeability durability was not clear. Thus, a comprehensive investigation of the permeability durability of oil shale waste as a fine aggregate is essential to achieving a better understanding in order to promote its engineering application. In this paper, the long-term permeability when using oil shale waste as a fine aggregate in OGFC was systematically investigated based on a self-developed laboratory physical clogging procedure. The test results illustrated the effectiveness of the utilization of oil shale waste as a fine aggregate in terms of permeability durability. A comprehensive index of the clogging coefficient containing mass, porosity and permeability coefficient was proposed based on gray relation entropy theory, the physical clogging model of COF-OGFC (OGFC containing oil shale waste filler) was established and the clogging speed of COF-OGFC was quantified based on the Mistcherlich growth model. The analysis showed that there is an essential difference in the clogging behavior of permeable pavement in the spring and summer. The maximum clogging degree of the permeable pavement in summer is about 40% higher than that in spring, while the clogging rate is much lower than in the spring, at only about 14%, which indicates that the clogging behavior of permeable asphalt pavement in spring is mostly in the rapid clogging mode, and that in summer is mostly in a slow deposition clogging mode. Moreover, the test results showed that the most important influences on the spring clogging behavior of COF-OGFC were the sandy clogging materials and particle sizes ranging from 150 μm to 1180 μm, which can be used to provide a reference for the design of anti-slip sand.