Urban Runoff Research Articles

Nitrogen Removal Efficiencies from Road Runoff by Dry Grass Swales with a Shallow Substrate Layer

To investigate nitrogen removal efficiencies and mechanisms from road runoff by dry grass swales with a shallow substrate layer, we constructed six dry grass swale columns with different structures and media composition. In order to enhance the nitrogen removal efficiencies during the whole process, fermented woodchips were added into the substrate layer, and saturated zones were established. Semi-synthetic road runoff was used as the influent water. The influent and effluent quality were analyzed, and the change in volumetric water content and ORP of the media were monitored. The results showed significant nitrogen removal by these columns under unfavorable conditions. The range of the average removal rate of TN by the dry grass swales with saturated zones was 67%-78%. The nitrogen removal process mainly occurred during the wet period of the substrate layer. The saturated zones enhanced nitrogen removal efficiencies during the dry period, and also promoted the quick establishment of anoxic conditions in the substrate layer during the wet period. The water-holding transition layer with organic matter was effective at providing a carbon source for denitrification in the saturated zone, and for avoiding the leaching of pollutants caused by organic decomposition.

Assessing Hydrological Effects of Bioretention Cells for Urban Stormwater Runoff in Response to Climatic Changes

An investigation into the effectiveness of bioretention cells (BCs) under potential climatic changes was conducted using representative concentration pathways. A case study of Guangzhou showed changes in peak runoff in climate change scenarios, with obvious growth in RCP8.5 and slight growth in RCP2.6. The performance of BCs on multiple parameters, including reduction of runoff volume, peak runoff, and first flush, were examined in different design storms using a hydrology model (SWMM). The effectiveness of BCs varied non-linearly with scale. Their performance fell by varying amounts in the various scenarios. BCs could provide sufficient effects in response to short-return-period and short-duration storms, but the performance of BCs decreased with heavy storms, especially considering climate change. Hence, BCs cannot replace grey infrastructure but should be integrated with them. The method developed in this study could be useful in the planning and design of low impact development in view of future climate changes.

Effect of photocatalytic Fe2O3 nanoparticles on urban runoff pollutant removal by permeable concrete

Permeable pavements are an efficient urban runoff (UR) management solution that also improve water quality. In this work, a photocatalytic layer of Fe2O3 nanoparticles (NP) was incorporated into permeable concrete to evaluate its impact on the removal of several microbiological (Escherichia coli, Pseudomonas aeruginosa, Aeromonas hydrophila, and Enterococcus faecalis) and physicochemical (N-NH4+, N-NO3-, phenol, PO43−, Fe, Mn, and Pb) pollutants. First, permeable concrete samples were created with sufficient compressive strength and hydraulic conductivity for light traffic. The test samples were then coated with a mixture containing either 3% or 5% Fe2O3 NP by cement weight. Control samples were prepared without NP. Scanning electron microscopy, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy analyses showed that the nanoparticles remained unaltered on the concrete's surface. Synthetic URs simulating the microbiological or physicochemical composition of real UR were applied to the samples to evaluate their pollutant removal efficiencies. The depollution performances of the test (with 3% and 5% Fe2O3 NP) and control samples were statistically compared. The test samples (3% NP, 5% NP, and the controls) significantly modified (p < 0.05) most of the measured variables (i.e., the concentrations of E. coli, A. hydrophila, PO43−, Fe, Mn, and Pb) in the synthetic URs. Unexpectedly, the test samples (with 3% or 5% Fe2O3 NP) did not significantly remove (p > 0.05) some pollutants prone to oxidation, such as phenol or ammonium. However, the 5% NP sample significantly enhanced Mn removal. In general, the decontamination performances of the concrete samples with Fe2O3 NP were not influenced by the nanoparticles; thus, they did not appear to add value to the generated permeable concrete. Nevertheless, our results indicate the considerable benefits of implementing permeable concrete to improve the quality of UR.

Impact of Urban Stormwater Runoff on Cyanobacteria Dynamics in A Tropical Urban Lake

Worldwide, eutrophication and cyanobacteria blooms in lakes and reservoirs are a great concern for water resources management. Coupling a catchment hydrological model and a lake model has been a strategy to assess the impact of land use, agricultural practices and climate change on water quality. However, research has mainly focused on large lakes, while urban reservoirs and their catchments, especially in tropical regions, are still poorly studied despite the wide range of ecosystem services they provide. An integrated modelling approach coupling the hydrological model Storm Water Management Model SWMM and the lake ecological model DYRESM-CAEDYM is proposed for Lake Pampulha (Brazil). Scenarios of increased imperviousness of the catchment and of reduction in the load of nutrients and total suspended solids (TSS) in dry weather inflow were simulated. Runoff water quality simulations presented a fair performance for TSS and ammonium (NH4+) while the dynamics of total phosphorus (TP) and nitrate (NO3−) were poorly captured. Phytoplankton dynamics in the lake were simulated with good accuracy (Normalized Mean Absolute Error, NMAE = 0.24 and r = 0.89 in calibration period; NMAE = 0.55 and r = 0.54 in validation period). The general trends of growth, decline and the magnitude of phytoplankton biomass were well represented most of the time. Scenario simulations suggest that TP reduction will decrease cyanobacteria biomass and delay its peaks as a consequence of orthophosphate (PO43−) concentration reduction in the lake surface layers. However, even decreasing TP load into Lake Pampulha by half would not be sufficient to achieve the water quality objective of a maximum concentration of 60 µg chla L−1. Increased imperviousness in the catchment will raise runoff volume, TSS, TP and NO3− loads into Lake Pampulha and promote greater cyanobacteria biomass, mainly in the beginning of the wet season, because of additional nutrient input from catchment runoff. Recovering Lake Pampulha water quality will require the improvement of the sanitation system. The lake water quality improvement will also require more sustainable and nature-based solutions for urban drainage in order to reduce non-point pollution through infiltration and retention of stormwater and to enhance natural processes, such as chemical sorption, biodegradation and phytoremediation. The integrated modelling approach here proposed can be applied for other urban reservoirs taking advantage of existing knowledge on Lake Pampulha.

Determination of Spatial and Temporal Variability of Soil Hydraulic Conductivity for Urban Runoff Modelling

Soil hydraulic conductivity has a direct influence on infiltration rate, which is of great importance for modelling and design of surface runoff and stormwater control measures. In this study, three measuring techniques for determination of soil hydraulic conductivity were compared in an urban catchment in Ljubljana, Slovenia. Double ring (DRI) and dual head infiltrometer (DHI) were applied to measure saturated hydraulic conductivity (Ks) and mini disk infiltrometer (MDI) was applied to measure unsaturated hydraulic conductivity (K), which was recalculated in Ks in order to compare the results. Results showed significant differences between investigated techniques, namely DHI showed 6.8 times higher values of Ks in comparison to DRI. On the other hand, Ks values obtained by MDI and DRI exhibited the lowest difference. MDI measurements in 12 locations of the small plot pointed to the spatial variability of K ranging between 73%–89% as well as to temporal variability within a single location of 27%–99%. Additionally, a reduction of K caused by the effect of drought-induced water repellency was observed. Moreover, results indicate that hydrological models could be enhanced using different scenarios by employing a range of K values based on soil conditions.

Kinetics and Isotherms Studies of the Adsorption of Hg(II) onto Iron Modified Montmorillonite/Polycaprolactone Nanofiber Membrane

Hg(II) ions from mining and urban runoffs can easily contaminate various water sources due to their high solubility in water. Due to its simplicity and viability, adsorption was utilized to treat Hg(II)-contaminated water. An adsorbent was fabricated by immobilizing Fe-modified montmorillonite particles in polycaprolactone through electrospinning. The SEM images of the fabricated membrane showed a nanofiber network with fiber diameter ranging from 96 nm to 569 nm and an average of 198 nm. The adsorption behavior of the fabricated membrane was investigated using kinetics and isotherm models. It was found that the adsorption of Hg(II) ions onto the membrane follows a pseudo-second order model and was best described by the Freundlich isotherm. The adsorption capacity was found to increase with increasing contact time and with increasing initial Hg(II) concentration, with the highest adsorption capacity of 14.25 mg/g. The sorption energy was calculated using the DubininKaganer-Radushkevich isotherm, which obtained a value of -2.68 kJmol−1 suggesting that the type of adsorption was physisorption.

Revisiting Two Robust Techniques for Contaminant Removal from Road Runoff

Treatment of road runoff is a requisite for any environmentally sound infrastructure design. However, investment and maintenance budget is often a limiting factor during the planning and the operation phase of such projects. In order to cost-efficiently decrease the loads of a wide range of contaminants that are usually present in road runoff (posing a long-term threat to the aquatic and soil environments), simple and robust techniques are sought for. The paper deals with the re-evaluation of two such processes, sedimentation and filtration, putting emphasis on using authentic runoff samples during the tests in order to properly characterize the performance of these easy-to-manage solutions in this specific field of application. The results presented in this paper are aimed to aid the proper design of low-cost, low-maintenance road runoff treatment facilities, serving with background information that can be used to ensure that the expectations for the degree of pollutant removal are surely met.

Improving Urban Runoff in Multi-Basin Hydrological Simulation by the HYPE Model Using EEA Urban Atlas: A Case Study in the Sege River Basin, Sweden

In this study, the high-resolution polygonal land cover data of EEA Urban Atlas was applied for land-use characterization in the dynamic multi-basin hydrological model, HYPE. The objective of the study was to compare this dedicated urban land cover data in semi-distributed hydrological modelling with the widely used but less detailed EEA CORINE. The model was set up for a basin including a small town named Svedala in southern Sweden. In order to verify the ability of the HYPE model to reproduce the observed flow rate, the simulated flow rate was evaluated based on river flow time series, statistical indicators and flow duration curves. Flow rate simulated by the model based on Urban Atlas generally agreed better with observations of summer storm events than the CORINE-based model, especially when the daily rainfall amount was 10 mm/day or more, or the flow exceedance probability was 0.02 to 0.5. It suggests that the added value of the Urban Atlas model is higher for heavy-to-medium storm events dominated by direct runoff. To conclude, the effectiveness of the proposed approach, which aims at improving the accuracy of hydrological simulations in urbanized basins, was supported.

Loads and Control Methods of Non-Point Source Pollution from Urban Runoff: A Case Study of Xiamen Island

Loads and Control Methods of Non-Point Source Pollution from Urban Runoff: A Case Study of Xiamen Island

Occurrence of phenolic derivatives in Buffalo River of Eastern Cape South Africa: Exposure risk evaluation

Phenolic derivatives are compounds used in the production of pesticides, pharmaceutical products and several other industrial applications. These compounds are discharged into freshwater from industrial effluents, domestic sewage, urban and agricultural run-offs which leads to pollution. Water at six sampling locations along the course of Buffalo River; namely Buffalo river estuary (BRE), Mdantsane (MSN), Zwelitsha (ZW), King William's Town (KWT), Izele Town (IZ) and Maden dam (MD) in the Eastern Cape Province, South Africa, were evaluated for phenolic contamination using eleven phenolic derivatives of United State Environmental Protection Agency (USEPA) priority pollutants. Samples were extracted using liquid-liquid extraction technique, derivatized with acetic anhydride and analyzed with gas chromatography mass spectrometry (GC-MS). The levels of the individual pollutants in the river water were higher in summer (< LOD to 12246 ng/L) than in autumn (< LOD to 713 ng/L). Their concentrations were found higher than the USEPA recommended limit (500 ng/L) in most of the sampling sites. The most prominent pollutant was 2-NP. However, the cancer risk assessment values and hazard quotient were below USEPA maximum limits of 10−6 and 1, respectively. Conclusively, the concentrations of these organic pollutants could be a threat to public health and should be managed to be below the recommended limit though the present levels are unlikely to cause cancer to both human and wildlife.

Study on the Control Performance of Rainwater Quality in the Ini-tial Stage of Urban Runoff by New Environmentally Friendly Rainwater Pass

In view of the current situation of gully in China, new type of environmentally-friendly gully with anti-mosquito and odor-reducing function has been developed. The control performance of new gully on the initial rainwater pollutants under the condition of different filter material ratio and filter bag thickness. The results show that the new environmentally-friendly gully has better removal effect of various pollutants in the initial rainwater under the condition of 1:3 filter material and 3cm filter bag. The removal rate of SS is over 80%, total nitrogen the removal rate is above 75%, and the removal rate of COD and total phosphorus is over 70%.

Accounting for the Spatio-Temporal Variability of Pollutant Processes in Stormwater TSS Modeling Based on Stochastic Approaches

Stormwater quality modeling remains one of the most challenging issues in urban hydrology today. The processes involved in contaminant generation and transport are very complex, with many associated uncertainties, including uncertainty arising from process variability. In this study, the spatio-temporal variability of build-up/wash-off processes in a heterogeneous urban catchment within the Parisian region is assessed based on three stochastic modeling approaches integrated into the physically based distributed hydrological model, the Urban Runoff Branching Structure (URBS) model. Results demonstrate that accounting for process variability at the scale of a hydrological element is important for analyzing the contamination recorded at the catchment outlet. The intra-event dynamics of total suspended solids (TSS) were most accurately selected for the stochastic exponential SWMM model, as this model succeeded not only in simulating the general trend of TSS concentrations fluctuations but also in replicating multiple peaks observed in pollutographs. The advantage of this approach is that it captures the stochastic nature of the processes with minimal prior knowledge and without extensive calibration, though further enhancement is necessary for it to become a useful tool to support decision making.

Characteristics of Phthalic Acid Esters Pollution in Urban Surface Runoff in Shanghai, China

Phthalic acid esters (PAEs) are still widely applied in China, and their pollution characteristics in urban surface runoff are important to receiving water protection. To evaluate the pollution characteristics of PAEs in urban runoff, six priority PAEs in road and roof runoff were monitored in nine storm events from June to September 2017 in Shanghai, China, and related rainwater samples were collected simultaneously. The average ∑6PAEs in urban road and roof runoff were 170.64 μg·L-1 and 40.92 μg·L-1, respectively, much higher than the values reported in Europe and Australia. Di-2-ethylhexyl phthalate (DEHP) was the dominating pollutant in both road and roof runoff. Significance analyses indicated there was no significant difference for low molecular weight(LMW)PAEs concentrations between road and roof runoff, whereas high molecular weight (HMW) PAEs concentrations in road runoff were significantly higher than those in roof runoff and rainwater (P<0.01), which implied that traffic was an important factor contributing to PAEs pollution in urban runoff. The pollutograph of PAEs, total suspended solids (TSS), and chemical oxygen demand (COD) concentrations vs rainfall duration for road runoff showed the same trend, and the first flush effect of PAEs was generally apparent. The influencing factors of PAEs in urban runoff were investigated. EMCs of PAEs in roof runoff were negatively correlated with rainfall intensity and positively correlated with TSS. EMCs of PAEs in road runoff were negatively correlated with rainfall volume and intensity and positively correlated with antecedent dry period, TSS, and COD. PAEs in surface runoff were significantly correlated with particulate matter. According to the criteria of the National Standard of Surface Water Quality of China, DEHP and DBP have limiting values of 8 μg·L-1 and 3 μg·L-1, respectively. The ratios of DEHP concentrations in road and roof runoff to the limiting values are 32 and 7, respectively. DBP concentrations were higher than the limiting value in most rainfall events for road runoff but lower than those for roof runoff. Without reasonable management measures, urban runoff could contaminate receiving water, especially drinking water sources.

A Comparison of Sources and Risk Assessment of Polycyclic Aromatic Hydrocarbons in Urban Stormwater Runoff from Ground and Highway Roads in Shanghai, China

Sixteen priority polycyclic aromatic hydrocarbon (PAH) concentrations in the runoffs of a ground road and elevated highway were monitored to analyze sources of PAH pollution between the two roads. The sources and potential toxicity effects of PAHs in the runoffs of the two kinds of road were evaluated. The arithmetic mean concentrations of a total of 16 PAHs in the runoffs of the ground road and elevated highway were respectively 1761 and 4153 ng/L. The individual PAH distributions had similar trends for the two kinds of road runoff, and BbF, FlA, Chy and BghiP were dominant PAHs. Coal/natural gas combustion, gasoline emission, diesel emission and oil leakage were identified as potential PAH sources for both road runoffs, but made different contributions. The potential toxicological effects of PAH sources in runoff were assessed by combining the total toxic BaP equivalent (TEQ) values with estimated source contributions. Results showed that (gasoline and diesel) vehicle emissions had the highest TEQ values, while coal/natural gas combustion and oil leakage had relatively low TEQ values. Reducing vehicle emissions is the most effective way to alleviate PAH toxic pollution in urban runoff, with road cleaning being another good choice.

Modelling of Grassed Road Divider as Bio-Retention System for Urban Road Drainage

An evaluation on the applicability of bio-retention system in grassed road divider under high rainfall of equatorial region was conducted by developing computer-aided stormwater models using USEPA SWMM 5.1. The models simulated road runoffs with and without bio-retention systems. A single unit of bio-retention system tested here was 3 m in width, 6 m in length with 150 mm of ponding depth and 600 mm of soil/storage depth. Results indicated that soil types of loamy sand, sandy loam and loam showed similar performance in reducing runoff. With installation of bio-retention system, road runoff could be reduced 40-50% when subjected to 60 minutes of 2-, 5- and 10-year ARI rain events. The results obtained from the simulation were encouraging that bio-retention system in grassed road divider could function to augment the existing urban road drainage.

Remote sensing application in monitoring change of river and coastlines of Morong, Bataan, Philippines

Remote sensing offers fast, cheap and reliable method in detecting river and coastal changes. In this study, satellite imageries of Morong river and coastlines from 2006 to 2016 were collected and analyzed to monitor changes. Field measurements were also done using South Total Station (NTS-362R6L) in 2016 for comparison and validation of data. Results showed that the river outlet and the riverbank increased in width size due to erosion brought about by torrential rains and urban run-offs. Coastlines near the river narrowed in size or shifted landward due to coastal erosion and sea level rise. An interview was conducted to locals residing nearby the river and coast where strong typhoons were reported which cause geophysical changes in the area. The residents also observed sea level rise, coastal and river erosion which caused narrowing of the coastlines and widening of the river, respectively. Records of high tides and low tides collected were projected in annual average levels per month. The average level of low tides increased per year which can be a result of sea level rise. The computed RMSE between field and remote sensing measurements ranged from 0.1m to 0.67m which indicated positional accuracy of Google Earth in the area.

New Derivation Method of Region Specific Curve Number for Urban Runoff Prediction at Melana Watershed in Johor, Malaysia

The Soil Conservation Services (SCS) rainfall-runoff model has been incorporated into many types of software and adopted by Malaysian government agencies for design use. However, hydrologists argue the accuracy of the predicted runoff results from this model in recent decades. Malaysia does not have a regional specific curve numbers available for the use in rainfall-runoff modelling, and therefore SCS-CN practitioner has no option but to adopt its guideline and handbook values which are specific to US region. Unlike the conventional SCS-CN technique, the proposed calibration methodology in this paper discarded the use of CN as input to the SCS model, rearranged the model equation and derived statistically significant CN value(s) of a specific region through rainfall-runoff events directly through the use of inferential statistics. The SCS rainfall-runoff framework can now be calibrated quickly to address urban runoff prediction challenge under rapid land use and land cover or climate changes with the proposed methodology. Between July and October of 2004, the derived λ was 0.0005 while λ = 0.20 was found to be statistically insignificant at alpha = 0.01 level at Melana watershed in Johor, Malaysia. Optimum CN of 90.45 was derived to represent the rainfall-runoff characteristic of Melana watershed. Runoff prediction error was reduced by 90% and achieved the Nash-Sutcliffe (NS) index of 0.86. The new method can provide CN adjustment guidelines for SCS practitioners and any software which incorporated the model to predict urban runoff.

Clogging Impacts on Distribution Pipe Delivery of Street Runoff to an Infiltration Bed

The performance of flow through orifices on a perforated distribution pipe between periods with and without partial clogging (submersion of part of the distribution pipe) was compared. The distribution pipe receives runoff and delivers it to an underground infiltration bed. Clogging appeared in winter but was reduced in summer. Performance of flow delivery was found to be defined by the effective pipe length and the pressure head. ANCOVA (ANalysis of COVAriance) was used to examine the clogging effect with flow rate plotted against the effective pipe length times the square root of the mean pressure head, and found that it was significant during low or no rainfall. During larger storms, clogging had little effect on pipe performance. Clogging might be caused by leaves and other trash accumulating in the lower section of the pipe in winter and its effect was insignificant when the water level rose in the pipe, utilizing significantly more orifices on the distribution pipe. Larger storms might also move the debris, thus exposing the orifices. The current maintenance schedule was sufficient to keep the distribution pipe at a satisfactory performance even though partial clogging can exist.

Correction to: Influence of Biochar from Slow Pyrolysis on Dissolved Organic Carbon and Total Dissolved Nitrogen Levels of Urban Storm-Water Runoff

Biochar as a filtering media has been attracted increasing attention for applications in urban storm-water runoff (USWR) management. Up-flow percolation tests were conducted with pine bark (PB) and biochars from PB (BCPB) for evaluating changes in dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) concentrations varying with pyrolysis temperatures (i.e., 300, 450, and 700 °C) and types of USWR (i.e., roof and pathway USWR). The most suitable pyrolysis temperature for limiting DOC leaching from BCPB depends on the types of USWR. For all the adopted pyrolysis temperature, BCPB released cumulative amount of DOC up to 0.01% of the TC content in the up-flow percolation tests with pathway USWR. High-temperature (i.e., 700 °C) BCPB released lower cumulative amount of DOC (up to 0.02% of the TC content) compared to the low-temperature (< 450 °C) BCPB in the roof USWR up-flow percolation tests. As for BCPB effectiveness in carbon sequestration, the amount of carbon that is not retained in BCPB because of leaching (DOC less than 0.1% of the TC content) may be considered negligible. Of the tested BCPB, only high-temperature BCPB removed TDN for both the types of USWR with cumulative removed quantities up to 0.006 g/kg dry weight, thus representing a better option for reducing N loads to receiving water basins.

Influence of Biochar from Slow Pyrolysis on Dissolved Organic Carbon and Total Dissolved Nitrogen Levels of Urban Storm-Water Runoff

Influence of Biochar from Slow Pyrolysis on Dissolved Organic Carbon and Total Dissolved Nitrogen Levels of Urban Storm-Water Runoff