Removal Efficiency of Bottom Ash and Sand Mixtures as Filter Layers for Fine Particulate Matter.

Permeable pavement is a technology that allows rainwater to infiltrate into the pavement. Permeable pavements not only help reduce surface runoff by allowing rainwater to infiltrate into the pavement, but also improve water quality with the filter layer that removes particulate matter pollutants. This study evaluated the particulate matter removal efficiency of bottom ash-sand mixtures as filter layers for removing fine (≤10 µm) or ultrafine (≤2.5 µm) particulate matter in the laboratory. Five filter media were tested: silica sand, bottom ash, and bottom ash-sand mixtures with 30:70, 50:50, and 70:30 ratios. The mixed filters exhibited more consistent and stable particulate matter removal efficiency over time than either the uniform sand or bottom ash filter. The 50:50 bottom ash-sand mixture demonstrated removal rates of 58.05% for 1.8 µm particles, 93.92% for 10 µm particles, and 92.45% for 60 µm particles. These findings highlight the potential of bottom ash-sand mixtures as effective filter media for removing PM10 road dust, although field validation with actual pavement systems is necessary.

Longitudinal Analysis of Urban Stormwater Microbiome and Resistome from Watersheds with and without Green Infrastructure using Long-Read Sequencing.

Since stormwater conveys a variety of contaminants into water bodies, green infrastructure (GI) is increasingly being adopted as an on-site treatment solution in addition to controlling peak flows. The purpose of this study was to identify differences in microbial water quality of stormwater in watersheds retrofitted with GI vs. those without GI. Considering stormwater is recently recognized as a contributor to the antibiotic resistance (AR) threat, another goal of this study was to characterize changes in the microbiome and collection of AR genes (resistome) of urban stormwater with season, rainfall characteristics, and fecal contamination. MinION long-read sequencing was used to analyze stormwater microbiome and resistome from watersheds with and without GI in Columbus, Ohio, United States, over 18 months. We characterized fecal contamination in stormwater via culturing Escherichia coli and with molecular microbial source tracking (MST) to identify sources of fecal contamination. Overall, season and storm event (rainfall) characteristics had the strongest relationships with changes in the stormwater microbiome and resistome. We found no significant differences in microbial water quality or the microbiome of stormwater in watersheds with and without GI implemented. However, there were differences between the communities of microorganisms hosting antibiotic resistance genes (ARGs) in stormwater from watersheds with and without GI, indicating the potential sensitivity of AR bacteria to treatment. Stormwater was contaminated with high concentrations of human-associated fecal bacterial genes, and the ARG host bacterial community had considerable similarities to human feces/wastewater. We also identified 15 potential pathogens hosting ARGs in these stormwater resistome, including vancomycin-resistant Enterococcus faecium (VRE) and multidrug-resistant Pseudomonas aeruginosa. In summary, urban stormwater is highly contaminated and has a great potential to spread AR and microbial hazards to nearby environments. This study presents the most comprehensive analysis of stormwater microbiome and resistome to date, which is crucial to understanding the potential microbial risk from this matrix. This information can be used to guide future public health policy, stormwater reuse programs, and urban runoff treatment initiatives.

Understanding the removal of heavy metals from stormwater runoff in permeable pavement system.

Understanding the removal of heavy metals (HMs) in permeable pavement systems is of great significance for controlling urban runoff pollution and optimizing structural design. However, few studies have systematically investigated the mechanism of permeable pavement systems in removing HMs from stormwater runoff. In this study, we adopted a hierarchical strategy to understand the efficiency of individual structural layers on HMs removal in a permeable interlocking concrete pavement (PICP) system. Experimental results illuminated that the surface layer exhibited the highest uptakes of HMs, which can remove up to 64 % of Pb2+, 50 % of Cu2+, 28 % of Cd2+ and 13 % of Zn2+. Meanwhile, as the rainfall return period increased, the removal rates of HMs in PICP was gradually decreased. In addition, batch experiments were conducted and the adsorption results were in accordance with the rainfall filtration experiments. More importantly, X-ray Photoelectron Spectroscopy (XPS) and leaching results were investigated to understand the HMs removal mechanism, which found that the ion exchange is the main mechanism in the surface layer to remove HMs, whereas the chemical adsorption play a crucial role in the base and sub-base layers. Overall, these findings provided new insights into the transport patterns of HMs in the internal structural layers of the PICP.

Removal and fate of microplastics in permeable pavements: An experimental layer-by-layer analysis.

The increasing prevalence of microplastics (MP) in urban environments has raised concerns over their negative effects on ecosystems and human health. Stormwater runoff, and road dust and sediment, act as major vectors of these pollutants into natural water bodies. Sustainable urban drainage systems, such as permeable pavements, are considered as potential tools to retain particulate pollutants. This research evaluates at laboratory scale the efficiency of permeable interlocking concrete pavements (PICP) and porous concrete pavements (PCP) for controlling microplastics, including tire wear particles (TWP) which constitute a large fraction of microplastics in urban environments, simulating surface pollution accumulation and Mediterranean rainfall conditions. Microplastic levels in road dust and sediments and stormwater runoff inputs were 4762 ± 974 MP/kg (dry weight) and 23.90 ± 17.40 MP/L. In infiltrated effluents, microplastic levels ranged from 2.20 ± 0.61 to 5.17 ± 1.05 MP/L; while tire wear particle levels ranged between 0.28 ± 0.28 and 3.30 ± 0.89 TWP/L. Distribution of microplastics within the layers of PICP and PCP were also studied and quantified. Microplastics tend to accumulate on the pavements surface and in geotextile layers, allowing microplastic retention efficiencies from 89 % to 99.6 %. Small sized (< 0.1 mm) fragment shaped microplastics are the most common in effluent samples. The results indicate that permeable pavements are a powerful tool to capture microplastics and tire wear particles, especially by surface and geotextile layers. The study aims to shed light on the complex mobilisation mechanisms of microplastics, providing valuable insights for addressing the growing environmental concern of microplastic pollution in urban areas.

Simulation test of short-term and long-term clogging of permeable pavement.

Permeable pavement is superior in functions such as reducing noise, improving traffic safety, and protecting urban water environment. However, contaminants on the pavement due to spillage of transported goods, deposits from vehicle wear and tear, and natural settlement can cause the risk of blockage when these contaminants enter the interior of the permeable pavement. Timely maintenance of permeable performance can effectively solve the degradation of environmental performance of permeable pavement caused by clogging. Consequently, exploring permeable pavement clogging patterns can support determining the timing of maintenance. In this paper, simulation clogging material gradations were formulated based on actual road clogging conditions. According to the self-developed permeable pavement clogging simulator, the clogging behavior of permeable pavement was comprehensively explored, taking external conditions, mix proportion, structural combination, and long-term clogging conditions into consideration. Moreover, the effect of external conditions on the clogging pattern was simulated by varying the rainfall intensity and clogging particle size. Furthermore, the effects of gradation, void rate, nominal maximum particle size, and the overwater section on the clogging resistance were investigated. The clogging-sensitive particle size under different structures was determined. It is demonstrated that the water head height is the crucial factor on the clogging behavior. Greater rainfall intensity and water head height lead to more severe clogging. The increase of nominal maximum aggregate size is beneficial to the anti-clogging ability of permeable pavement. Also, the clogging material with small particle sizes is more likely to cause structural clogging. Finally, the evaluation index of clogging level was put forward, which divides the clogging level of permeable pavement into mild, moderate, and severe. The research can support the rationalization, intelligence, and convenience of permeable pavement maintenance timing decisions. Meanwhile, there is key significance to the promotion application and performance maintenance.

Field temperature performances of in-use permeable sidewalks and asphalt vehicle roads and the potential impacts on apparent temperature and land surface temperature.

Permeable pavements help reduce surface temperatures and have been widely implemented in urban areas. This study utilized an in-use permeable pavement sidewalk in front of a mass rapid transit station in the Taipei city center of Taiwan to determine the actual pavement surface temperature performance. A neighboring asphalt road and impervious pavement were also monitored. With a full year of continuous monitoring, the results showed that the temperature of permeable pavement was 3.7 °C lower than that of impervious pavement and 4.5 °C lower than that of asphalt pavement in the hot season. The frequent rainfall in spring resulted in the smallest temperature differences between the different pavement types. The cooling effects of permeable pavement differed at the different air temperatures. At air temperatures lower than 15 °C, the differences among pavement surface temperatures were noticeable. However, when the air temperature was higher than 35 °C, the surface temperature of permeable pavement was not different from that of impervious pavement and was greater than 55 °C. Field observations were carried out to determine the effects on the apparent temperature and the future surface temperature of climate change scenarios. The results showed that permeable pavement could reduce the average apparent temperature to near the air temperature, and asphalt pavement could increase the apparent temperature by 1.2 °C, assuming that the pavement temperature completely affects the air temperature. With the good prediction ability of the machine learning approach and 15 environmental factors, the preliminary prediction showed the projected surface temperature change in Taipei city in 2033. In the worst-case scenario, the average impervious pavement temperature is as high as 39.12 °C, whereas the average permeable pavement temperature is 32.50 °C.

Dataset on the assessment of pervious concrete containing palm oil kernel shell and seashell in heavy metal removal from stormwater.

The dataset currently available comprises data on the removal rates of heavy metals (Ba, Se, Cr, Fe, Cd, As, and Co) through the incorporation of seashells and palm oil kernel shells into pervious concrete for stormwater treatment. Stormwater runoff was collected from commercial areas in Taman University, Skudai, Johor, Malaysia. The stormwater samples underwent filtration and were preserved in high-density polyethylene (HDPE) bottles at a temperature of 4 °C for use as incoming water. The outgoing water, referred to as effluent, was obtained from tests performed on pervious concrete samples after a curing period of 28 days. The pervious concrete mixes were created with a water-to-binder ratio (w/b ratio) of 32% and a sand ratio of 10%. Three different levels of palm oil kernel shell and seashell content were used as coarse aggregate replacements: 0%, 25%, and 50%. Two single-size group were considered for both palm oil kernel shell and seashell: (6.3-9.5 mm) and (4.75-6.3 mm). Heavy metal analyses were conducted on the influent and effluent using a PerkinElmer ELAN 6100 Series Inductively Coupled Plasma- Mass Spectrometer (ICP-MS). The available datasets consist of both raw and analyzed data.

TSS Removal Efficiency and Permeability Degradation of Sand Filters in Permeable Pavement.

Permeable pavement is a highly effective technology in Low-Impact Development (LID) for managing stormwater runoff, which helps mitigate environmental impacts. Filters are essential components of permeable pavement systems as they prevent permeability reduction, remove pollutants, and enhance the system's overall efficiency. This research paper focuses on exploring the influence of three factors, including total suspended solids (TSS) particle size, TSS concentration, and hydraulic gradient, on the permeability degradation and TSS removal efficiency of sand filters. A series of tests were conducted using different values of these factors. The results demonstrate that these factors have an influence on permeability degradation and TSS removal efficiency (TRE). A larger TSS particle size results in higher permeability degradation and TRE than a smaller particle size. Higher TSS concentrations lead to higher permeability degradation and lower TRE. Additionally, smaller hydraulic gradients are associated with higher permeability degradation and TRE. However, the influence of TSS concentration and hydraulic gradient seems less significant than that of TSS particle size for the values of the factors considered in the tests. In summary, this study provides valuable insights into the effectiveness of sand filters in permeable pavement and identifies the main factors that influence permeability degradation and TRE.

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.

The control efficiency and mechanism of heavy metals by permeable pavement system in runoff based on enhanced infiltration materials.

As one of the commonly used stormwater management measures, permeable pavement system (PPS) played a prominent role in controlling runoff pollution and alleviating urban waterlogging. In this study, new enhanced infiltration materials (construction waste brick, coal gangue, activated carbon, multi-walled carbon nanotube, multi-layer graphene) were applied in PPS and the control efficiency and mechanism of typical heavy metals (HMs, Mn2+, Pb2+, Zn2+, Cu2+, Cd2+, Ni2+) was investigated in runoff. Furthermore, the influences of different rainfall intensities and antecedent dry periods on HMs removal by PPS were evaluated. The results showed that all PPS with enhanced infiltration materials have little leaching effect on HMs (＜3 µg/L). All the selected enhanced infiltration materials meet the requirements of PPS. The concentration of HMs in the effluent of PPS dropped sharply first, followed rebounded and then maintained at a stable range. Activated carbon PPS (AC), Multi-walled carbon nanotube PPS (MCN), and Multi-layer graphene PPS (MG) could significantly improve the control effect of PPS on nearly all selected HMs. The average removal rates of AC, MCN and MG for six HMs were 75.48%-99.35%, 81.30%-97.59%, and 73.03%-99.33%, respectively. Compared with Traditional PPS (TR), the effluent concentrations of HMs in construction waste brick PPS (CW) and coal gangue PPS (CG) were relatively higher and unstable. AC, CN and MG could adapt to different rainfall conditions and the maximum removal rates of most HMs exceed to 99%. With antecedent dry periods increased, the control effect of HMs was significantly improved. The influences of the antecedent drying period on HMs removal followed as: CW＞CG＞TR＞MG＞CN＞AC. This study provided novel methods to eliminating HMs in runoff and provides implications for the design of PPS.

Year-round monitoring of chloride releases from three zero-exfiltration permeable pavements and an asphalt parking lot.

Winter deicers, though essential for maintaining safe pavement conditions in winter, increase chloride (Cl-) concentrations in receiving water bodies above recommended environmental guidelines. Zero-exfiltration or lined permeable pavement is an important technological innovation for controlling particulate-bound pollutants at the source. As stormwater does not infiltrate into the ground, soluble pollutants like Cl- are ultimately discharged into receiving water bodies. Our aim was to examine Cl- concentrations in effluents from three zero-exfiltration permeable pavement cells (Permeable Interlocking Concrete Pavement (PICP), Pervious Concrete (PC), Porous Asphalt (PA)) and compare them with runoff from a Conventional Asphalt (ASH) cell. The study conducted at a parking lot in St. Catharines, Ontario, Canada, from January 2016 to May 2017 observed that the permeable pavements provided only temporary attenuation of Cl- during winter but exhibited a quick release during spring melt. Cl- concentrations and loadings were different for each permeable pavement system in terms of timing and magnitude. Cl- concentration in ASH runoff frequently had very high spikes (21,780 mg/L); however, the median winter Cl- concentration in ASH runoff was lower than Cl- levels in the permeable pavements' effluents and later declined drastically after spring melt, but in few instances, was above the chronic water quality guideline (120 mg/L). The average event mean concentration (EMC) of Cl- was 1600 and 120 mg/L in the permeable pavements' effluents during salting and non-salting season, respectively. In one year, each permeable pavement system released approximately 67-81 kg of Cl- with significant differences being observed in Cl- loads between the 2016 and 2017 seasons. Therefore, a multi-year data collection and monitoring plan captured the variability in winter conditions. The study provided insights into the behaviour, retention and release of Cl- from traditional and permeable hardscape surfaces and possible avenues for Cl- attenuation, source control and aquatic habitat conservation.

Seasonal variation in indicator organisms infiltrating from permeable pavement parking lots at the Edison Environmental Center, New Jersey.

Four types of permeable pavements were monitored at the Edison Environmental Center in Edison, New Jersey, for three water quality indicator organisms consisting of fecal coliform, enterococci, and Escherichia coli. This study expands a previously published result based on less than a year of available data. The current study reflects nearly 5 years of data collection with efforts focusing on collection of data in all four seasons to analyze seasonal effects and to understand the effects of pH on infiltrate concentrations. All three indicators were detected in infiltrates from all four permeable surfaces and as well as asphalt and roof runoff. Seasonally, the infiltrate during winter had fewer detections and lower enumerations and was most often significantly different than surface infiltrate and runoff for the other seasons. More significant concentration reductions were observed in summer and fall, and the lowest reduction was observed in winter. Pervious Asphalt treatment removed the most microorganisms for all three indicator organisms. A permeable interlocking concrete pavement (PICP) that was a replacement for pervious concrete during the study performed better than the original PICP most likely due to smaller gap spacing (8 mm compared to 12.7 mm) and correspondingly smaller specified surface aggregate compared to the original PICP. Percent concentration removal reductions based on geometric means were 89% or greater for PC, PA, and PICP for fecal coliform; 75% or better for PC, PA and PICP for E. coli; and 95% or greater for PC and PA for enterococci, while there were no annual removals for enterococci for original or new PICP nor removals for E. coli for original PICP and minimal removal for fecal coliform for original PICP. The major sources of fecal indicators in the stormwater runoff were most likely from the feces of deer, geese, and other wild animals. PRACTITIONER POINTS: The infiltrate during winter had fewer detections and lower enumerations and was most often significantly different than surface infiltrate and runoff for the other seasons. More significant concentration reductions were observed in summer and fall, and the lowest reduction was observed in winter. Pervious Asphalt treatment removed the most microorganisms for all three indicator organisms.

Nature-based solutions for securing contributions of water, food, and energy in an urban environment.

There is growing awareness that nature-based solutions (NBS) prevent negative effects and secure ecosystem services. However, the potential of NBS to provide intended benefits has not been rigorously assessed. Water, food, and energy (WFE) are essential for human well-being. This study highlights the importance of NBS in terms of water, food, and energy. A set of on-site NBS that includes permeable pavements, plant microbial fuel cells, bio-filtration basins, and rain gardens is used to determine the contribution of NBS to the environmental and economic development of urban environments. The results of this study show that NBSs benefit an urban environment in terms of water treatment, stormwater retention, food production and energy generation, carbon sequestration, pollination, sedimentation retention, and cultural services dimension. This research highlights an urgent need for the integration of water, food, and energy plans to ensure that NBSs contribute to the environment and for the conservation of ecosystem services.

The influence of evaporation from porous concrete on air temperature and humidity.

Porous concrete is increasingly being used as a more sustainable surfacing alternative to asphalt and other impermeable materials. This is because, not only does it provide source control of stormwater, but it also has the potential to help mitigate the urban heat island effect through the process of evaporative cooling. This experimental investigation examines how evaporation from these systems is affected by the availability of water within the porous concrete and the influence this has on the surrounding environment, particularly in terms of air temperature and humidity. The effect of a dual layer porous concrete on evaporation rates is also assessed, which is important because the dual layer system is a relatively new development that is now being used in many parts of the world. It was found that both evaporation rate and evaporative cooling were strongly influenced by water availability near the upper surface of the porous concrete and under these conditions significant air temperature reductions can be achieved. It was also found that having a dual layered porous concrete system did not have a considerable effect on evaporation rates in this study, probably because of the relatively large thickness of the upper layer.

Predicting location and evaluating progression of clogging in a permeable pavement parking lot.

In 2009, a permeable pavement research and demonstration site was constructed at the Edison Environmental Center, Edison, NJ. Infiltration testing of three original permeable parking rows through August 2012 indicated that clogging occurred along the upgradient edge of these pavements from runoff that drained from adjacent impermeable driving lanes. A subsequent infiltration testing data collection effort from April 2017 through March 2020 focused on permeable interlocking concrete pavers (PICP) that replaces one of the original permeable surfaces. While the original infiltration study through 2012 used random locations throughout the permeable parking rows, the newer study targeted upgradient edge to identify where clogging would occur. Testing locations along the upgradient edge were selected based on a high-resolution survey (HRS) of the parking lot performed in December 2014. The HRS identified three low spots along the upgradient edge that eventually clogged in the new PICP infiltration study. The HRS may assist with maintenance routines. The newer study also supports the conclusion of the earlier study with regards to truncating the infiltration testing method, particularly for maintenance assessments.

Assessing maintenance techniques and in-situ pavement conditions to restore hydraulic function of permeable interlocking concrete pavements.

Permeable pavements are increasingly implemented to mitigate the negative hydrologic outcomes associated with impervious surfaces. However, the hydraulic function of permeable pavements is hindered by clogging in their joint openings, and systematic maintenance is needed to ensure hydraulic functionality throughout the design lifespan of these systems. To quantify the effectiveness of various maintenance measures, surface infiltration rates (SIRs) were measured before and after five different maintenance techniques were applied to five permeable interlocking concrete pavements (PICPs) in central Ohio, USA. Three maintenance techniques, the Municipal Cleaning Vehicle (MCV), the Rejuvenater, and a pressure washer and the Rejuvenater performed in series, significantly improved median SIRs from 16 to 26, 5 to 106, and 11 to 37 mm/min, respectively. However, pressure washing alone resulted in no significant difference to PICP SIR (median SIRs increased from 8 to 20 mm/min). Regenerative air street sweeping significantly worsened SIRs when performed during wet weather (median SIRs decreased from 19 to 4 mm/min) but had no significant impact on SIRs during dry weather (median SIRs decreased from 21 to 18 mm/min). This work captured the maintenance effectiveness of two techniques for the first or second time, namely the Rejuvenater and MCV, to investigate their use as a suitable maintenance technique. Further, the maintenance techniques were tested on multiple PICPs, thus the effect of in-situ pavement conditions had on hydraulic improvement via maintenance could be addressed. Differences in general upkeep, traffic, and runoff routed to a PICP affected the depth of clogging below the pavement surface, which forestalled hydraulic improvement. Though shown to improve the SIR of PICP systems, results indicate that the maintenance techniques were not capable of restoring pavement hydraulics to initial conditions. These results demonstrate the need for regular, routine maintenance and topping up of joint aggregate before clogging migrates deeper into the pavement profile.

A Three-Dimensional Microstructure Reconstruction Framework for Permeable Pavement Analysis Based on 3D-IWGAN with Enhanced Gradient Penalty.

Owing to the increasing use of permeable pavement, there is a growing need for studies that can improve its design and durability. One of the most important factors that can reduce the functionality of permeable pavement is the clogging issue. Field experiments for investigating the clogging potential are relatively expensive owing to the high-cost testing equipment and materials. Moreover, a lot of time is required for conducting real physical experiments to obtain physical properties for permeable pavement. In this paper, to overcome these limitations, we propose a three-dimensional microstructure reconstruction framework based on 3D-IDWGAN with an enhanced gradient penalty, which is an image-based computational system for clogging analysis in permeable pavement. Our proposed system first takes a two-dimensional image as an input and extracts latent features from the 2D image. Then, it generates a 3D microstructure image through the generative adversarial network part of our model with the enhanced gradient penalty. For checking the effectiveness of our system, we utilize the reconstructed 3D image combined with the numerical method for pavement microstructure analysis. Our results show improvements in the three-dimensional image generation of the microstructure, compared with other generative adversarial network methods, and the values of physical properties extracted from our model are similar to those obtained via real pavement samples.

Improved approach for evaluating saturated surface infiltration capacity of interlocking-block permeable pavements.

Different infiltration tests of permeable pavements provide different measurements of the infiltration capacity. These measurements often do not represent the fundamental flow properties, and hence cannot be directly compared. This presents an undesirable obstacle to the sharing of experience and to obtaining a better understanding of the infiltration performances of different permeable pavements. This problem is especially acute in the case of interlocking-block permeable pavements (IBPPs), owing to the presence of joints and the different sizes, shapes, and laying patterns of paving blocks. To overcome this problem, the present study proposed a new approach for evaluating the infiltration capacity of an IBPP while retaining the same measuring devices in use today. This approach makes use of a finite-volume computational fluid dynamic method to develop a simulation model for an infiltration test. Once calibrated to define the hydraulic parameters of the IBPP being tested, the model can be applied to calculate the saturated infiltration capacity of the IBPP under actual rainfall conditions. The model also permits the calculation of a conventional infiltration capacity measurement, such as the average infiltration rate in mm/h as measured by a particular infiltration test, or the time required to drain the tested water depth. Thus, the proposed approach provides a meaningful common basis for comparing the infiltration capacities of different permeable pavements, including porous asphalt, pervious concrete, and IBPPs.

Prediction Models Based on Regression and Artificial Neural Network for Moduli of Layers Constituted by Open-Graded Aggregates.

The impermeable cover in urban area has been growing due to rapid urbanization, which prevents stormwater from being naturally infiltrated into the ground. There is a higher chance of flooding in urban area covered with conventional concretes and asphalts. The permeable pavement is one of Low-Impact Development (LID) technologies that can reduce surface runoff and water pollution by allowing stormwater into pavement systems. Unlike traditional pavements, permeable pavement bases employ open-graded aggregates (OGAs) with highly uniform particle sizes. There is very little information on the engineering properties of compacted OGAs. In this study, the moduli of open-graded aggregates under various compaction energies are investigated based on the Plate Load Test (PLT) and Light-Weight Deflectometer (LWD). Artificial Neural Network (ANN) and Linear Regression (LR) models are employed for estimation of the moduli of the aggregates based on the material type and level of compaction. Overall, the moduli from PLT and LWD steeply increase until the number of roller passes reaches 4, and they gradually increase until the number of roller passes becomes 8. A set of simple linear equations are proposed to evaluate the moduli of open-graded aggregates from PLT and LWD based on the material type and the number of roller passes.

Performance of permeable pavement systems on stormwater permeability and pollutant removal.

Permeable pavement is an effective means for stormwater runoff control and pollutant removal. However, relatively few studies have examined the characteristics of permeable brick and corresponding permeable pavement system (PPS). In this work, the permeable pavement systems consisted of surface permeable brick layer (concrete or ceramic) with structural layer (including a cement mortar layer, a permeable concrete layer, and a gravel layers) were selected as typical cases to assess their permeability and runoff pollutant removal performance by laboratory experiments. The results indicated that PPS had obvious outflow hysteresis effect. The PPS with ceramic brick layer reached the saturation flow rate earlier and showed larger outflow rate than that with concrete brick layer. Both types of PPSs had a relatively high efficiency (83.8-95.2%) in removing suspended solids (SS) in stormwater runoff mainly due to the interception and filtration of the surface brick layer, whereas the structural layer of the PPS played a vital role in the removal of total phosphorus (TP). The percentage of total nitrogen (TN) removal efficiency via ceramic brick layer accounted for via corresponding PPS was obviously larger than that of concrete brick layer. The PPS also displayed a certain chemical oxygen demand (COD) removal ability: around 14.0-27.0% for concrete type and 20.9-28.9% for ceramic type. Subsequently, a multi-objective evaluation model was implemented based on the analytic hierarchy process (AHP) method to identify the optimal scheme in relation to four indices: permeability, environmental benefit, compressive strength, and comprehensive economic cost. The results showed, insofar, the ceramic PPS is preferred with a better economic performance. Our study attempts to select optimal designs of PPS and provides insight into the permeable capacity and the efficiency of pollutant removal in PPS.