Nutrient removal using biosorption activated media: preliminary biogeochemical assessment of an innovative stormwater infiltration basin

Scientific Evidence behind the Ecosystem Services Provided by Sustainable Urban Drainage Systems

Urban green infrastructure such as sustainable urban drainage systems are potential providers of ecosystem services. This paper reviews the field studies that empirically verify the potential benefits of SUDS. The cultural, provisioning, supporting, and regulating ecosystem services investigated in real cases have been studied and classified according to climatology (except for the control of urban hydrology, which has been widely corroborated). Although successful cases of runoff decontamination are numerous, there is heterogeneity in the results of the systems beyond those associated with climatic differences. The other ecosystem services have not been as widely studied, giving very variable and even negative results in some cases such as climate change control (in some instances, these techniques can emit greenhouse gases). Installations in temperate climates are, by far, the most studied. These services derive from the biological processes developed in green infrastructure and they depend on climate, so it would be advisable to carry out specific studies that could serve as the basis for a design that optimizes potential ecosystem services, avoiding possible disservices.

Hydraulic and nutrient removal performance of vegetated filter strips with engineered infiltration media for treatment of roadway runoff

As a new strategy for treating excess nutrients in roadway runoff, a self-filtering roadway could be accomplished by including engineered infiltration media within a vegetated filter strip (VFS) located in the roadway shoulder. However, nutrient removal performance will depend on the design to effectively infiltrate roadway runoff and the capacity of subsurface media to sequester or remove nutrients from infiltrated runoff. The objective of this study is to test hydraulic and nutrient removal performance of a roadside VFS over varied rainfall-runoff event sizes and filter widths. Two identical 1:1 scale physical models of roadway shoulders and embankments, one containing engineered media (Treatment model) and the other without (Control model), were tested with simulated rainfall and runoff from 1- and 2-lane roadways. Overall, 32 paired hydraulic experiments and 28 paired nutrient removal experiments were completed to assess performance across frequent and extreme rainfall-runoff events. The results indicate that scalability of performance with filter width varied by parameter. Runoff generation scaled predictably with filter width, as runoff generated close to the pavement and total infiltration increased with filter length. A 6 m-wide VFS containing the engineered media infiltrated all rainfall-runoff except during the most extreme storm events (1-h storms of 76.2 mm and 50.8 mm), where respectively 35% and 22% of rainfall-runoff did not infiltrate and left the system as surface runoff. A majority of phosphorus was retained within a 1.5 m filter while nitrate removal was not observed until 6 m. The Treatment model strongly outperformed the Control model with respect to nitrate (arithmetic mean ± standard deviation of 94 ± 6% reduction vs. 23 ± 64% increase, p < .001) and total nitrogen removal (80 ± 5% vs. 38 ± 23% reduction, p < .001) due to higher rates of microbially-mediated denitrification in the Treatment model. The two models performed comparably with regard to phosphorus reduction (84 ± 9% vs. 82 ± 12% reduction). A minimum 6 m filter width is recommended to ensure sufficient infiltration of runoff and nitrogen removal. Results of this study address uncertainty regarding nutrient removal performance of VFS in urban runoff applications and highlight a potential strategy for standardizing VFS performance across varied soil properties by including engineered media within the filter.

How do urban rainfall-runoff pollution control technologies develop in China? A systematic review based on bibliometric analysis and literature summary

Rapid urbanization in China is driving the need of urban rainfall-runoff pollution control technologies due to adverse impacts on water environment. In this study, literature from China National Knowledge Infrastructure, Web of Science and Scopus in 1995/1/1-2019/5/15 are used to review research hotspots, development process and future directions of urban rainfall-runoff pollution control technologies in China and global world. Temporal evolution of publications showed that source reduction played better growing trend in urban rainfall-runoff pollution control field for both China and global world. Furthermore, with bibliometric tool, density visualization maps and co-occurrence network maps were created to identify research hotspots in China and global world. By comprehensively analyzing research hotspots above and development process from extracted literature, future directions of urban rainfall-runoff pollution control technologies were predicted. For model and strategy, both China and global world would concern on the accuracy of models to evaluate combination technologies. For source reduction, China would explore rainwater purification in sponge city, while global world would investigate match characteristics between specific regions and control technologies, combination between model and technologies, and improvement of pollutants removal. For process control, China would enhance ecological gutter inlet performance, whereas global world would concentrate on optimization of rainwater harvesting system. For post treatment, China would estimate modified hydrocylone and coagulation technology, and improve performance of filtration systems, riparian buffers and constructed wetlands, while global world would explore ecological and landscape function of constructed wetlands. Since China ranked first in producing Western publications and was the second most cited country for Western publications recently, China would significantly influence future development of urban rainfall-runoff pollution control technologies around the world. Meanwhile, some directions including infiltration basin and rainwater harvesting system were still shortcomings for China due to a late start of urban rainfall-runoff pollution control technologies in China.

Integration of machine learning classifiers and higher order tensors for screening the optimal recipe of filter media in stormwater treatment

Filter media have oftentimes been used in fixed-bed column tests to examine their removal efficiencies for various pollutants, such as nutrients in stormwater runoff. With limited data sets from column studies, a response surface method (RSM), such as the Box-Behnken Design (BBD), and machine learning methods, can be used to transition from discrete mode assessment to continuous mode optimization, from which the key ingredients of filter media can be better synergized. In this study, similarly to drug discovery via chemometrics, RSM is used to generate meta-models and identify the optimum ratio between clay and iron-filings contents in Iron-filings-based Green Environmental Media (IFGEM) for nutrient removal in stormwater treatment. To achieve the continuous mode optimization, artificial neural network (ANN), deep belief network (DBN), and extreme learning machine (ELM) were selected as machine learning models to compare with BBD to explore the limited column data sets and improve the data science. While separate RSM can help realize the removal efficiencies of total nitrogen (TN), total phosphorus (TP), and ammonia based on varying ratios of clay and iron-filings contents in IFGEM, heterogeneous and inconsistent response surfaces generated from the four learners or classifiers (ANN, ELM, DBN, and BBD) complicate the selection of the final optimal recipe. The power of higher order singular value decomposition (HOSVD) helps synergize the optimal clay and iron filings matrixes of IFGEM in the context of continuous mode optimization via ANN, ELM, DBN, and BBD. With the aid of HOSVD, the optimal recipe for a holistic nutrient removal of TN, TP, and ammonia was determined to be 5% clay, 10% iron filings, 10% tire crumb, and 75% sand.

Mixed versus layered multi-media filter for simultaneous removal of nutrients and heavy metals from urban stormwater runoff

Beach closings are a growing concern in coastal regions because of serious public health and economic ramifications due to the presence of pollutants in stormwater runoff. An underground permeable filter system is proposed to treat such stormwater pollution. Selection of filter media that can treat multiple contaminants in stormwater runoff has been a challenging task. This paper investigates the effectiveness of mixed or layered filter media for the removal of mixed contaminants (nutrient and heavy metal) from synthetic stormwater. Sorption experiments were used to assess the ability of the combination of various materials (calcite, zeolite, sand, and iron filings) to remove nutrients and heavy metals. Based on the results of individual removal efficiency, four sets of combinations of media mixtures were prepared: three mixed media conditions and one layered media condition. Mixed media-1, containing higher ratio of calcite, zeolite, and iron filings, was found to achieve the highest removal efficiency of nitrate (96%), Cr (~ 99%), and Cu (~ 99%). Mixed media-2 removed Zn significantly with a removal efficiency higher than 99% due to the sorption capacity of iron filings and both mixed media-2 and 3 showed efficient removal of Ni (~ 94%) in effluent. Layered media was found to be most efficient in Cd removal (~ 99%). All mixture of materials showed more than 99% removal of total phosphorus and Pb. The sorption efficiency of the different mixtures showed that a combination of traditional (sand) and alternative materials (calcite, zeolite, and iron filings) can be used as an effective medium for the treatment of nutrient and heavy metal contaminants commonly found in stormwater.

Inorganic Nitrogen Production and Removal along the Sediment Gradient of a Stormwater Infiltration Basin

Stormwater infiltration basins (SIBs) are vegetated depressions that collect stormwater and allow it to infiltrate to underlying groundwater. Their pollutant removal efficiency is affected by the properties of the soils in which they are constructed. We assessed the soil nitrogen (N) cycle processes that produce and remove inorganic N in two urban SIBs, with the goal of further understanding the mechanisms that control N removal efficiency. We measured net N mineralization, nitrification, and potential denitrification in wet and dry seasons along a sedimentation gradient in two SIBs in the subtropical Tampa, Florida urban area. Net N mineralization was higher in the wet season than in the dry season; however, nitrification was higher in the dry season, providing a pool of highly mobile nitrate that would be susceptible to leaching during periodic dry season storms or with the onset of the following wet season. Denitrification decreased along the sediment gradient from the runoff inlet zone (up to 5.2 μg N/g h) to the outermost zone (up to 3.5 μg N/g h), providing significant spatial variation in inorganic N removal for the SIBs. Sediment accumulating around the inflow areas likely provided a carbon source, as well as maintained stable anaerobic conditions, which would enhance N removal.

Evaluating the effect of seasonal temperature changes on the efficiency of a rhizofiltration system in nitrogen removal from urban runoff

The study presents an evaluation of nitrogen removal efficiency of a pilot-scale rhizofiltration system in Pretoria, South Africa. The rhizofiltration system was divided into two sections, one side planted with common reeds (Phragmites australis) and the other side was without plants kept as a control. The objective of the study was to evaluate the influence of seasonal temperature on the removal of nitrogen species from the simulated urban runoff using the rhizofiltration system. The final effluent from the filter was collected bimonthly at different sampling points for 10 months after an application time of 5 min and 25 min. Duplicate samples were taken to determine the concentrations of TKN (Total Kjeldahl nitrogen), ammonium, nitrate and chemical oxygen demand (COD) for the raw influent and final effluent from the rhizofiltration system. Temperature and pH were determined on-site. During the monitoring period, there was no significant difference in the inflow concentration of ammonium in colder and warmer months for both planted and control sides. Furthermore, the composition of the feed medium to the rhizofilter was kept the same in both cold and warm season and for both planted and control sides. The removal of ammonium in colder and warmer months was not significant in both systems. At an average temperature increase of 5.2 °C in the warmer months, the ammonium removal efficiency in the planted side increased by 7.5%, while for the control side the removal efficiency increased by 2.4%. The difference in removal was not significant between the averages of effluent ammonium after an application time of 25 min in colder versus warmer months for the planted and control sides of the system. Furthermore, an increased nitrification rate was more evident in the planted than in the control side, which was subsequently denitrified. It was observed that 60.4% of nitrate concentration was potentially removed in the planted side whereas 45.4% was potentially denitrified in the control side. These results suggest positive correlation between nitrate concentration and the potential for denitrification. The nitrate removal efficiency dropped to 32.2% for the planted site and to 26.1% for the control system in colder months. Temperature had an effect on nitrogen removal, since nitrogen removal efficiency decreased in colder months. Complete nitrogen removal could not be achieved under the operating conditions.

Adsorption thermodynamics and kinetics of Advanced Green Environmental Media (AGEM) for nutrient removal and recovery in agricultural discharge and stormwater runoff

Recycled materials were used in three types of green sorption media for nutrient removal and possible recovery in high nutrient-laden agricultural discharge and stormwater runoff. The three types of green sorption media included in this comparative study were two new aluminum-based green environmental media (AGEM) and one existing iron-filings based green environmental media (IFGEM). The corresponding adsorption isotherm, thermodynamics, and kinetics models were simulated based on isotherm studies to determine their removal efficiency and potential for recovery of nitrate, phosphate, and ammonia when used as a soil amendment in crop fields or in a filter for water treatment. AGEM-2 exhibited the shortest contact time required to achieve nutrient removal above 80% with an average of 7 h, followed by AGEM-1 and IFGEM with 10.6 and 28 h, respectively. Natural soil was included as a control and exhibited minimal nutrient removal. Ammonia, which may be recovered as fertilizer for drop fields in a soil-water-waste nexus, was generated by all three green sorption media mixes, therefore indicating their potential for use as soil amendments in agricultural and forested land after engineering filter applications. The kinetics analysis indicated that nitrate adsorption follows pseudo-first-order kinetics, while phosphate adsorption follows pseudo-second-order kinetics. The Gibbs free energy indicated that most of the adsorption reactions proceeded as exothermic. Lastly, a few equilibrium models, including the Langmuir, Freundlich, First Modified Langmuir, Temkin, Jovanovic, and Elovich models, were ranked and three were selected for use with IFGEM, AGEM-1, and AGEM-2, respectively, as below: (1) Langmuir, (2) Freundlich, and (3) First Modified Langmuir, according to three indices.

The interaction of dissolved organic nitrogen removal and microbial abundance in iron-filings based green environmental media for stormwater treatment

Nonpoint sources pollution from agricultural crop fields and urbanized regions oftentimes have elevated concentrations of dissolved organic nitrogen (DON) in stormwater runoff, which are difficult for microbial communities to decompose. The impact of elevated DON can be circumvented through the use of green sorption media, such as Biosorption Activated Media (BAM) and Iron-Filing Green Environmental Media (IFGEM), which, as integral parts of microbial ecology, can contribute to the decomposition of DON. To compare the fate, transport, and transformation of DON in green sorption media relative to natural soil (control), a series of fixed-bed columns, which contain natural soil, BAM, and two types of IFGEM, respectively, were constructed to compare nutrient removal efficiency under three distinct stormwater influent conditions containing nitrogen and phosphorus. The interactions among six microbial species, including ammonia-oxidizing bacteria, nitrite-oxidizing bacteria, complete ammonia oxidation (comammox) bacteria, anaerobic ammonium oxidation (anammox) bacteria, dissimilatory nitrate reduction to ammonium bacteria, and iron-reducing bacteria, were further analyzed from microbial ecology perspectives to determine the DON impact on nutrient removal in BAM and IFGEM. Natural soil was only able to achieve adequate DON transformation at the influent condition of lower nutrient concentration. However, the two types of IFGEM showed satisfactory nutrient removals and achieved greater transformation of DON relative to BAM when treating stormwater in all three influent conditions.

Assessing Nutrient Removal in Stormwater Runoff for Urban Farming with Iron filings-based Green Environmental Media

Ensuring urban areas have access to clean drinking water, safe food supply, and uncontaminated water bodies is essential to the good health of millions of urban residents. This paper presents the functionality of Iron Filings-based Green Environmental Media (IFGEM) in terms of nutrient removal efficiencies to support water quality management and urban farming. IFGEM uses recycled materials such as tire crumb and iron filings to help remove nutrients with essential physicochemical properties. In this study, IFGEM were proven effective and sustainable through an isotherm study, a column study of reaction kinetics, and a microstructure examination under various inlet nutrient concentration levels. IFGEMs exhibited over 90% nitrate removal, as well as 50–70% total phosphorus removal, under most inlet conditions. These promising results make IFGEM suitable for treating stormwater runoff, wastewater effluent, and agricultural discharge via varying ex situ treatment units in flexible landscape environments. In addition, the byproduct of ammonia generation permits possible reuse of spent IFGEM as soil amendments in crop land, gardens and yards, and green roofs for urban farming. Findings may help secure urban food supply chains and harmonize nutrients, soil, water, and waste management in different urban environments.

Evaluation of green sorption media blanket filters for nitrogen removal in a stormwater retention basin at varying groundwater conditions in a karst environment

Removing excess nutrient from stormwater runoffs is necessary to protect the water quality of receiving water bodies such as rivers, lakes, springs, and groundwater aquifers. Silver Springs Springshed, located in the vicinity of Ocala, Florida, has received widespread attention from the local government and residents due to its long-term nutrient impact, which has resulted in eutrophication. Blanket filters containing Bio-sorption Activated Media (BAM) were implemented with different depths of the vadose zone in a stormwater retention basin. The design combined the interaction with groundwater as an innovative Best Management Practice can potentially boost the performance of nutrient removal. Selected storm runoffs were collected at multiple points that cover the runoff timeframe to determine the pollutant load. Infiltrating water samples were collected at various depths within BAM using lysimeters to validate the treatment effectiveness. Significant pollutant load reduction of nutrients was confirmed with highest 99% and 91% removal of nitrate and nitrite (NO_x) and total nitrogen (TN) at the deep blanket filter (with more groundwater intrusion impacts) due to more effective denitrification and longer contact time. Yet the highest pollutant load reduction of 93% and 84% removal of NO_x and TN was also observed at the shallow blanket filter (with less groundwater intrusion impacts). On the other hand, better pollutant load reduction of ammonia in the BAM layer was found at the shallow blanket filter presumably due to more available oxygen for nitrification.

The impact of media, plants and their interactions on bioretention performance: A review

Bioretention systems have gained considerable popularity as a more natural approach to stormwater management in urban environments. The choice of bioretention media is frequently cited as one of the critical design parameters with the ultimate impact on the performance of the system. The goal of this review is to highlight data that challenge the importance of media as being the dominant design parameter and argue that the long-term performance is shaped by the interactions between media and the living components of a bioretention system, especially vegetation. Some of the key interactions are related to the impact of plant roots on media pore structure, which has implications on infiltration, storage capacity, and treatment. Another relevant interaction pertains to evapotranspiration and the associated impacts on the water balance and the water quality performance of bioretention systems. The impacts of vegetation on the media are highlighted and actual, as well as potential, impacts of plant-media interactions on bioretention performance are presented.

Comparative nitrogen removal via microbial ecology between soil and green sorption media in a rapid infiltration basin for co-disposal of stormwater and wastewater

In this study, a rapid infiltration basin (RIB) designed as green infrastructure for co-disposal of wastewater effluent and stormwater runoff was retrofitted for sustainable groundwater recharge after nitrogen removal. For comparison of nitrogen removal efficiency via different filtration media, the RIB was divided into two sub-basins for different filtration processes. One sub-basin was filled with a native sandy soil with about 2-4% clay (Control RIB), and the other sub-basin was modified with Biosorption Activated Media (BAM) (BAM RIB), for the enhancement of microbial nitrogen removal. The two sub-basins accept an equal amount of excess reclaimed wastewater in non-storm periods, and stormwater during periodic storm events. The infiltrate in both the BAM RIB and the Control RIB eventually reaches the Upper Floridan Aquifer. The seven microbial species involved in this microbial ecology study are nitrite oxidizing bacteria (NOB), ammonia oxidizing bacteria (AOB), anaerobic oxidation of ammonium (anammox) bacteria, complete ammonia oxidizer (Comammox) bacteria, denitrifiers, dissimilatory nitrate reduction to ammonium (DNRA) and ammonia-oxidizing archaea (AOA). The population dynamics study was conducted with the aid of the quantitative polymerase chain reaction (qPCR) for the quantification of the microbial gene population in support of microbial ecology discovery. The qPCR results demonstrated the competition effect between AOA, AOB, and Comammox, the inhibition effect between NOB and DNRA with the presence of anammox, and the complementary effect due to an abundance of NOB and AOB in the microbial ecology. Although, competition between denitrifiers and DNRA was expected to impact population dynamics, both microbial species were found to be the most predominant in both control and BAM RIBs. Research findings indicate that the use of BAM RIB achieves significantly efficient nitrogen removal driven by complementary effects in the microbial ecology.

Comparison of a modified and traditional rapid infiltration basin for treatment of nutrients in wastewater effluent

A traditional rapid infiltration basin (RIB) has been compared to a modified RIB constructed with manufactured biosorption-activated media (BAM) to evaluate nitrate removal from wastewater effluent. The RIBs are used for reclaimed and excess stormwater disposal. In this work, a mixture of clay, tire crumb, and sand (CTS) was selected to serve as the BAM material (Bold and Gold™ CTS media). Each RIB was constructed with two feet of either sand or BAM, covering more than 43,600 square feet of surface area. Over an eight-month period, loadings to the BAM RIB and traditional RIB each approximated 5.4 million gallons (MG) per acre. Water samples collected from lysimeters installed below the 2 foot of sand or BAM materials were analyzed for nutrients. Results suggest that under the conditions of the study BAM removed approximately 31% more nitrate-nitrites and total phosphorus than the traditional RIB. Additionally, BAM removed approximately 18% more total nitrogen than the traditional. PRACTITIONER POINTS: Biosorption-activated media (BAM) removed nitrate-nitrites from reclaimed water more effectively than sand in rapid infiltration basins. BAM could serve as an alternative media for nutrient removal from water prior to release to the environment. Total nitrogen removal was most influenced by NO_x removal, with a few removals influenced by TKN. Nutrients could not be effectively removed using BAM or sand from reclaimed water at threshold concentrations below two parts per million.

Fate and transport processes of nitrogen in biosorption activated media for stormwater treatment at varying field conditions of a roadside linear ditch

Roadside drainage networks can result in changes to watershed hydrology and water quality. By acting as hydrological links between urban development, agricultural fields, and natural streams, roadside ditches may be modified by filling in some green sorption media to control nitrogen pollution. Biosorption activated media (BAM), one of the green sorption media, are composed of sand, tire crumb, and clay, which can remove nitrogen from stormwater and groundwater through integrated hydrological, chemophysical, and microbial processes. The fate and transport processes of interest are complicated by internal microbial processes including ammonification, nitrification, denitrification, and dissimilatory nitrate reduction to ammonium (DNRA), each of which is controlled by different microbial species in addition to some varying field conditions. In this study, BAM was tested in a suite of columns to address site-specific physical, chemical and biological concerns driven by in situ traffic compaction, carbon availability, and animal impact (such as gopher turtles, moles, and ants) all of which impose different impacts on nitrogen fate and transport processes that may be signified by changing dissolved organic nitrogen species (DONs). The traffic compaction condition resulted in the most suitable hydraulic retention time in the hydrological process, which is beneficial for the assimilation of DONs in a long-term carbon rich environment due to biofilm expansion. Denitrifiers were the most predominant microbial population and the microbial species of DNRA were the second most predominant one in all three field conditions. However, the relationship of denitrifiers and DNRA in BAM can be shifted from commensalism to competition or even inhibition after carbon addition in microbial ecology.

Treatment Assessment of Road Runoff Water in Zones filled with ZVI, Activated Carbon and Mineral Materials

Reducing the discharge of contaminants present in runoff water is important for a clean environment. This paper analyses field test results of three pilot-scale horizontal runoff water treatment zones filled with mixtures of zero valent iron (ZVI), activated carbon (AC), silica spongolite (SS), zeolite (Z), and limestone (LS). The investigated systems were (S1) ZVI/AC/SS, (S2) ZVI/AC/Z and (S3) ZVI/AC/LS. The efficiency of the three systems in the removal of Cd, Cu, Ni, Pb, Zn, COD and ammonium ions from runoff water was compared and the factors (temperature, pH, redox potential, hydraulic conductivity) and relationships affecting treatment effectiveness were determined. A statistical analysis of effluent contaminant concentrations and physicochemical parameters of effluent solutions included descriptive statistics, analysis of variance (ANOVA), a multidimensional analysis using a Principal Component Analysis (PCA), a factor analysis (FA) and a cluster analysis (CA). The ANOVA and cluster analyses indicated similarities between systems containing SS and LS. As a consequence, using cheaper SS can reduce investment costs. In addition, there were no significant differences between the three systems regarding Cd and Ni removal, while Cu and Pb were removed to almost 100%. The results indicate that all the tested materials supported ZVI and AC in the removal of heavy metals in a similar way. However, runoff water was enriched with nitrogen oxides and sulfates while flowing through treatment zones with SS and LS. The enrichment increased with increasing temperature and redox potential. The conducted analyses indicate that the most suitable mixture is ZVI/AC/Z. It should be emphasized that the ongoing processes (precipitation and ZVI corrosion) reduced the hydraulic conductivity of the filters up to two orders of magnitude. Expansive iron corrosion was the most limiting factor in ZVI filtration systems. In the future, applications decreasing the percentage of ZVI in the mixture are suggested.

A Review of Nitrogen Removal for Urban Stormwater Runoff in Bioretention System

One of the best management practices (BMPs) for stormwater quality and quantity control is a bioretention system. The removal efficiency of different pollutants under this system is generally satisfactory, except for nitrogen which is deficient in certain bioretention systems. Nitrogen has a complex biogeochemical cycle, and thus the removal processes of nitrogen are typically slower than other pollutants. This study summarizes recent studies that have focused on nitrogen removal for urban stormwater runoff and discusses the latest advances in bioretention systems. The performance, influencing factors, and design enhancements are comprehensively reviewed in this paper. The review of current literature reveals that a bioretention system shows great promise due to its ability to remove nitrogen from stormwater runoff. Combining nitrification and denitrification zones with the addition of a carbon source and selecting different plant species promote nitrogen removal. Nevertheless, more studies on nitrogen transformations in a bioretention system and the relationships between different design factors need to be undertaken.

The Impact of Temperature on the Removal of Inorganic Contaminants Typical of Urban Stormwater

Appropriate management of urban stormwater requires consideration of both water quantity, resulting from flood control requirements, and water quality, being a consequence of contaminant distribution via runoff water. This article focuses on the impact of temperature on the efficiency of stormwater treatment processes in permeable infiltration systems. Studies of the removal capacity of activated carbon, diatomite, halloysite, limestone sand and zeolite for select heavy metals (Cu and Zn) and biogenes (NH4-N and PO4-P) were performed in batch conditions at 3, 6, 10, 15, 22, 30 and 40 °C at low initial concentrations, and maximum sorption capacities determined at 3, 10, 22 and 40 °C. A decrease in temperature to 3 °C reduced the maximum sorption capacities (Qmax) of the applied materials in the range of 10% for diatomite uptake of PO4-P, to 46% for halloysite uptake of Cu. Only the value of Qmax for halloysite, limestone sand and diatomite for NH4-N uptake decreased slightly with temperature increase. A positive correlation was also observed for the equilibrium sorption (Qe) of Cu and Zn for analyses performed at low concentrations (with the exception of Zn sorption on limestone sand). In turn, for biogenes a rising trend was observed only in the range of 3 °C to 22 °C, whereas further temperature increase caused a decrease of Qe. Temperature had the largest influence on the removal of copper and the smallest on the removal of phosphates. It was also observed that the impact of temperature on the process of phosphate removal on all materials and ammonium ions on all materials, with the exception of zeolite, was negligible.

Comparative copper toxicity impact and enzymatic cascade effect on Biosorption Activated Media and woodchips for nutrient removal in stormwater treatment

Copper, a commonly occurring heavy metal in stormwater runoff, was tested for its inhibitory effects on key nitrogen cycle bacteria in Biosorption Activated Media (BAM) and woodchip. The information in this paper is used to show that copper can enhance the denitrification process through enzyme cascade reactions since nitrous reductase is the enzyme responsible for the last step of denitrification and is largely dependent on copper as its cofactor. However, media characteristics are critical for assessing multi-enzymatic cascade reactions from the microbial ecology point of view. Moreover, both media showed significant copper removal through various mechanisms at 30 cm depth. The bioactivity evaluation indicates that other bacteria (fermentative bacteria, etc.) can be largely depressed with the presence of copper, hence the biofilm structure would be more vulnerable under shearing effects, which may result in holistic depression on the microbial community.

The Impact of Carbon Source as Electron Donor on Composition and Concentration of Dissolved Organic Nitrogen in Biosorption-Activated Media for Stormwater and Groundwater Co-Treatment

Eutrophication has been a long-term issue in aquatic environments, where dissolved organic nitrogen (DON) recalcitrance is important. Bioavailable nitrogen qualification and quantification for effluents from stormwater and wastewater are always a challenge. The information in this study deepens the understanding of the interactions between carbon addition and DON decomposition through linear-ditch best management practices for stormwater and groundwater cotreatment. By running a laboratory-scale column study for nitrogen removal using green sorption media, the variation in composition and concentration of DON can be further linked to the population dynamics of microbial species that dominate the nitrification and denitrification processes. With the varying levels of influent total nitrogen concentration, the efficacy of nitrogen removal via biosorption activated media may be realized at the molecular level with ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry.

Predictors of Phosphorus Leaching from Bioretention Soil Media

The phosphorus saturation index (PSI) and P saturation ratio (PSR) were tested across a wide range of bioretention soil mixtures (BSMs) for their relationship to total and dissolved P in column leachate. The BSMs tested were made using different feedstocks including sand alone, food and yard waste compost, biosolids and yard compost, and high Fe biosolids. The PSI of the mixtures ranged from 0.23 ± 0.03 (biosolids and yard waste compost 15%, oyster shells 5%) to 1.26 ± 0.02 (biosolids and yard waste compost 80%). The PSR of the mixtures ranged from 0.05 ± 0 (100% sand) to 3.12 ± 0.12 (biosolids and yard waste compost 80%). A total of 12 storm events were staged using both synthetic rainwater (total P = 1.71 ± 0.3 mg L) and actual stormwater (total P = 0.08 ± 0.03 mg L). Excluding the sand-only mixture, all treatments were a source of P for the duration of the study. However both total and dissolved P concentrations decreased over time. Effluent concentrations of total P in the first event ranged from 0.59 to 75.55 mg L but decreased by the final event to between 0.15 and 10.73 mg L. The PSR was found to be a good predictor of P leaching from all BSMs with an of 0.73 for total mass of P leached across all leaching events. The PSI was a poor predictor ( < 0.3). The PSR also predicted total P in leachate for individual events more effectively than the PSI. Total P in the BSMs had no relationship to P in the leachate.

Screening the toxicity of phosphorous-removal adsorbents using a bioluminescence inhibition test

When found in excess, phosphorus (P) has been linked to surface water eutrophication. As a result, adsorbents are now used in P remediation efforts. However, possible secondary toxicological impacts on the use of new materials for P removal from surface water have not been reported. This study evaluated the toxicity of adsorbent materials used in the removal of P from surface water including: fly ash, bottom ash, alum sludge, a proprietary mix of adsorbents, and a proprietary engineered material. Toxicity screening was conducted by performing solid-liquid extractions (SLEs) followed by the bacterial bioluminescence inhibition test with a Microtox® M500. Of the materials tested, the samples extracted at lower pH levels demonstrated higher toxicity. The material exhibiting the most toxic response was the iron and aluminum oxide coated engineered material registering a 66-67% 15-min EC50 level for pH 4 and 5 SLEs, respectively. However, for SLEs prepared at pH 7, toxic effects were not detected for this engineered material. Fly ash and bottom ash demonstrated between 82 and 84% 15-min EC50 level, respectively, for pH 4 SLE conditions. Dried alum sludge and the proprietary mix of adsorbents were classified as having little to no toxicity.

Stormwater Bioretention Systems: Testing the Phosphorus Saturation Index and Compost Feedstocks as Predictive Tools for System Performance

A replicated column trial was conducted to evaluate the potential for the phosphorus saturation index (PSI) to predict P movement in bioretention soil mixtures (BSMs). The impact of compost feedstock on BSM performance was also evaluated. Three composts (biosolids/yard, yard/food waste, and manure/sawdust) were each brought to PSI values of 0.1, 0.5, and 1.0 through the addition of Fe-based water treatment residuals (WTRs) to lower the PSI and P salts to increase the PSI. A synthetic stormwater solution was used for 12 leaching events. The PSI predicted total and dissolved P concentrations in column leachate. All composts removed P at PSI 0.1. All composts were a source of P for the higher PSI values tested, with P concentrations in the leachate decreasing over time. Ammonia and nitrate from all treatments decreased over time, with all treatments showing effective N removal. Copper removal (total and dissolved) was >90% for all treatments, with the highest removal observed at PSI 0.1 for all composts. Zinc removal (total) was also greatest in the 0.1 PSI for all composts. At PSI 0.5 and 1.0, the biosolids/yard compost was less effective than the other materials at removing Zn, with a removal efficiency of approximately 50%. Infiltration rates were similar across all treatments and ranged from 0.44 ± 0.1 cm min in the manure/sawdust at PSI 0.1 to 3.8 ± 2.8 cm min in the food/yard at PSI 1.0. Plant growth in the manure/sawdust compost was reduced in comparison to the other composts tested across all PSI levels. The results of this study indicate that the PSI may be an effective tool for predicting P movement in bioretention systems. Compost feedstock does not indicate the ability of composts to filter contaminants filtration, with all composts tested showing high contaminant removal.

A review of ion and metal pollutants in urban green water infrastructures

In urban environments, the breakdown of chemicals and pollutants, especially ions and metal compounds, can be favoured by green water infrastructures (GWIs). The overall aim of this review is to set the basis to model GWIs using deterministic approaches in contrast to empirical ones. If a better picture of chemicals and pollutant input and an improved understanding of hydrological and biogeochemical processes affecting these pollutants were known, GWIs could be designed to efficiently retain these pollutants for site-specific meteorological patterns and pollutant load. To this end, we surveyed the existing literature to retrieve a comprehensive dataset of anions and cations, and alkaline and transition metal pollutants incoming to urban environments. Based on this survey, we assessed the pollution load and ecological risk indexes for metals. The existing literature was then surveyed to review the metal retention efficiency of GWIs, and possible biogeochemical processes related to inorganic metal compounds were proposed that could be integrated in biogeochemical models of GWIs.

System dynamics modeling of nitrogen removal in a stormwater infiltration basin with biosorption-activated media

Stormwater infiltration basins, one of the typical stormwater best management practices, are commonly constructed for surface water pollution control, flood mitigation, and groundwater restoration in rural or residential areas. These basins have soils with better infiltration capacity than the native soil; however, the ever-increasing contribution of nutrients to groundwater from stormwater due to urban expansion makes existing infiltration basins unable to meet groundwater quality criteria related to environmental sustainability and public health. This issue requires retrofitting current infiltration basins for flood control as well as nutrient control before the stormwater enters the groundwater. An existing stormwater infiltration basin in north-central Florida was selected, retrofitted, and monitored to identify subsurface physiochemical and biological processes during 2007-2010 to investigate nutrient control processes. This implementation in the nexus of contaminant hydrology and ecological engineering adopted amended soil layers packed with biosorption activated media (BAM; tire crumb, silt, clay, and sand) to perform nutrient removal in a partitioned forebay using a berm. This study presents an infiltration basin-nitrogen removal (IBNR) model, a system dynamics model that simulates nitrogen cycling in this BAM-based stormwater infiltration basin with respect to changing hydrologic conditions and varying dissolved nitrogen concentrations. Modeling outputs of IBNR indicate that denitrification is the biogeochemical indicator in the BAM layer that accounted for a loss of about one third of the total dissolved nitrogen mass input.