Phosphorus and Heavy Metals Removal from Stormwater Runoff Using Granulated Industrial Waste for Retrofitting Catch Basins.

Phosphorus and heavy metals are washed off and transported with stormwater runoff to nearby surface water bodies resulting in environmental and human health risks. Catch basins remain one of the primary gateways through which stormwater runoff and pollutants from urban areas are transported. Retrofitting catch basins to enhance their phosphorus and heavy metal removal can be an effective approach. In this study, aluminum-based water treatment residual (WTR, a non-hazardous byproduct of the water treatment process) was granulated via a green method to serve as a sustainable filter material, called WTR granules, for enhancing the capabilities of catch basins to remove phosphorus and heavy metals. The WTR granules were field tested in a parking lot in Hoboken, New Jersey. Twelve storm events were monitored. The results showed that the WTR granules significantly (p < 0.05) reduced dissolved P, Cu, and Zn, as well as total P, Cu, Pb, and Zn concentrations in stormwater runoff without signs of disintegration. No flooding or water ponding was observed during the implementation. Results suggest the WTR granules are an inexpensive, green filter material that can be used for retrofitting catch basins to remove phosphorus and heavy metals effectively.

Temporal and spatial distribution of microplastics in green infrastructures: Rain gardens.

Rain gardens, a type of green infrastructure (GI), have been recognized for mitigating flooding and improving water quality from minor storms by trapping stormwater pollutants. Yet, the capability of these systems to retain microplastics (MPs) from stormwater, especially in size <125 µm, remains inadequately understood. This study investigated the spatial and temporal distributions of MPs in three rain gardens located in Newark, New Jersey, USA. The rain gardens have been in operation for ∼7 years and located in different land uses: low-density residential (Site 1), commercial (Site 2), and high-density residential (Site 3). The sediment samples were collected during May 2022, August 2022, and February 2023 at various soil depths and horizontal distances of rain gardens. The MPs were quantified and characterized using Fourier transform infrared (FTIR) spectrometer and a Raman microscope. The overall mean concentration varied between sampling sites, with 469 ± 89.8 pkg-1 in Site 1, 604 ± 91.4 pkg-1 in Site 2, and 997 ± 64.3 pkg-1 in Site 3, with Polypropylene as the dominant polymer, followed by nylon and polyethylene. In the vertical direction, larger MPs (250 µm-5 mm) were effectively retained within the top 5 cm and their concentration declined exponentially with the increasing depths. Small-sized MPs (1-250 µm) were prevalent at deeper depths (≥ 10 cm), and no MPs were found below 15 cm. In the horizontal direction, the highest MP concentration was observed near the stormwater inlet, and the concentration decreased away from the inlet. Over the nine-month period, a notable increase in concentration was observed at all sites. These findings contribute valuable knowledge towards developing effective measures for retaining MPs from stormwater and monitoring GIs in urban environments.

Repurposing spent biomass of vetiver grass used for stormwater treatment to generate biochar and ethanol.

Stormwater pollution is a key factor contributing to water quality degradation, posing substantial environmental and human health risks. Although stormwater retention ponds, also referred to as wet ponds, are commonly implemented to alleviate stormwater challenges by reducing peak flow and removing suspended solids, their effectiveness in removing heavy metals and nutrients is limited. This study evaluated the performance of floating treatment platforms (FTPs) featuring vetiver grass (Chrysopogon zizanioides), a non-invasive, nutrient- and metal-accumulating perennial grass, in removing heavy metals (Cu, Pb, and Zn) and nutrients (P and N) in stormwater retention ponds. Furthermore, the potential for utilizing the spent vetiver biomass for generating biochar and bioethanol was investigated. The study was conducted in a greenhouse setup under simulated wet and dry weather conditions using pond water collected from a retention pond in Stafford Township, New Jersey, USA. Two FTPs with vetiver (vegetated FTPs) were compared with two FTPs without vetiver (non-vegetated FTPs), which served as controls. Results showed that the removal of heavy metals and nutrients by the FTPs with vetiver was significantly higher (p < 0.05) than the FTPs without vetiver. Notably, vetiver showed resilience to stormwater pollutants and hydroponic conditions, displaying no visible stress symptoms. The biochar and bioethanol generated from the spent vetiver exhibited desirable yield and quality, without raising concerns regarding pollutant leaching, indicated by very low TCLP and SPLP concentrations. This study provides compelling evidence that the implementation of vetiver-based FTPs offers a cost-effective and environment-friendly solution for mitigating stormwater pollution in retention ponds. Furthermore, the utilization of vetiver biomass for biofuel and biochar production supports clean production and fostering circular economy efforts.

Green engineered mulch for phosphorus and metal removal from stormwater runoff in bioretention systems.

Phosphorus and metals in stormwater runoff are major causes of water quality degradation. Bioretention systems are increasingly implemented to improve stormwater quality and to better manage stormwater quantity. Many studies have focused on modifying the composition of the soil bed to improve pollutant removal. However, the pollutant removal performance of bioretention systems can diminish over time, such as when clogging of the media occurs. Sediment accumulation on the soil surface may inhibit infiltration into the soil bed, thus limiting pollutant removal. Soil replacement may be eventually required as pollutants accumulate in the soil. In this study, a green retrofit material, called green engineered mulch (GEM), was generated by coating regular wood mulch with aluminum-based water treatment residuals (WTR) via a simple and low-energy process (patent pending). The GEM was developed to serve as a green retrofit for bioretention systems to enhance the removal of phosphorus and metals from stormwater runoff. The GEM was placed in a rain garden in Secaucus, NJ, USA for 15 months, during which 12 storm events (ranging from 6.0 mm to 89.6 mm) were monitored. Runoff and infiltrate samples were analyzed for dissolved and total concentrations of phosphorus and metals, along with other key water quality parameters. The GEM significantly reduced (p < 0.05) the total concentrations of phosphorus and metals in stormwater infiltrate compared to the inlet, unlike the regular mulch. Minimal or no contact with the GEM resulted in no significant pollutant removal from surface runoff. No significant pollutant export from the GEM was observed. The spent GEM can be disposed of as non-hazardous waste in municipal landfills. This study demonstrates that the GEM is a safe and effective retrofit. Moreover, the GEM is a simple and economical retrofit solution that can be used in place of regular mulch in bioretention systems.

Characterizing microplastics in urban runoff: A multi-land use assessment with a focus on 1-125 µm size particles.

Urban areas play a significant role in generating microplastics (MPs) through increased vehicular and human activities, making urban runoff a key source of MP pollution in receiving waterways. The composition of MPs is anticipated to vary with land use; hence, identifying the hotspots of contamination within urban areas is imperative for the targeted interventions to reduce MPs at their sources. This study collected one-liter stormwater runoffs from three different land uses as sheet flow during two storm events to quantify the MPs and identify the polymers transported from land-based sources. The analytical method included a combination of Fourier transform infrared spectrometer, Raman microscope, and Nile red staining techniques. This study analyzed the broad spectrum of MPs, i.e., 1 µm-5 mm, and tire wear and bitumen particles, considered the two major research gaps in stormwater studies. The MP concentrations were 67.7 ± 11.3 pL-1in commercial, 23 ± 10.3 pL-1 in residential, and 168.7 ± 37.1 pL-1in highways. The trend of MP concentrations followed an order of highway > commercial > residential with an exclusive presence of polymethylmethacrylate and ethylene-vinyl acetate in highways; cellophane, methylcellulose, polystyrene, polyamide, and polytetrafluorethylene in commercial; and high-density polyethylene in residential areas. The dominant MP morphology consisted of fragments, accounting for 89 % of the identified MPs, followed by 10 % fibers and 1 % films. This study observed a prevalence of MPs sizes <125 µm constituting 49 % of the total composition. These findings underscore the vital role of land use patterns in shaping MP abundance and reinforce the urgency of implementing effective management strategies to mitigate MP pollution in stormwater runoff.

Health Risk Assessment of Exposure to Trace Elements from Drinking Black and Green Tea Marketed in Three Countries.

Although tea can be beneficial for our health, consuming excess trace elements in tea can be harmful. In this study, the carcinogenic and noncarcinogenic health risk for trace elements in tea influenced by the country of origin, tea type, and infusion process was assessed. Tea (Camellia sinensis) purchased from China, India, and the USA, including black and green tea, were analyzed for essential micronutrients (Cu, Se, and Zn) and nonessential trace elements (Ag, As, Ba, Cd, Cr, and Pb) in leaves and three types of infusions. The results showed that country of origin, tea type, and infusion process had a significant influence on the trace element contents in tea leaves and infusions, also on health risk. Country of origin had a significant influence on Ba, Cr, Pb, and Zn contents in tea leaves and on As, Ba, Cd, Cr, Pb, and Zn contents in tea infusions. Black tea had significantly higher (p < 0.05) Cr and Cu content in tea leaves than green tea, but only Cr content was significantly higher (p < 0.05) than that of green tea in tea infusion. The trace element contents were the highest in the first infusion and decreased as the number of infusion steps increased. The results showed that the consumption of tea infusion was not likely to cause noncarcinogenic risk. However, the carcinogenic risk for As was of concern. Our results indicate that avoiding drinking the first infusion can help to reduce both carcinogenic and noncarcinogenic health risks for trace elements.