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SEM images of biochar before and after the modification as BC-nZVI: (a) Sharp edges of biochar with high porosity; (b) Smooth surface of biochar with macropores; (c) Iron (nZVI) particles accumulated in the sharp edges in BC-nZVI; and (d) Iron (nZVI) particles distributed on the surface in BC-nZVI.
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This research investigated the removal of heavy metal ions (Cd, Cu, Pb, and Zn) and metalloid (As) common to stormwater runoff onto biochar-based media arranged in multiple configurations. Laboratory scale column experiments were conducted to quantify heavy metal removal efficiencies using sand, biochar, and nZVI-modified biochar (BC-nZVI) in four...
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... Numerous studies have been conducted to measure the adsorption capacities of different types of biochar, which were successful in removing contaminants commonly found in stormwater, such as ammonium ( NH + 4 59.6% [14], Copper (Cu) 58-95%, Zinc (Zn) 70% [15][16][17][18], Cadmium (Cd) 26-28%, Chromium (Cr) 18-22% [13], per-and polyfluoroalkyl substances (PFAS) > 96%, Antimony (Sb) 40%, and lead (Pb) 99% [19]. High specific surface area, porous structure, water retention capacity, and different functional groups of biochar collectively provide ample adsorption sites and enhance treatment efficiency for environmental remediation [20][21][22]. Pyrolysis temperature is another dominating factor that can modify the functional groups and porous structure, ash fraction, and carbon content of biochar. Increasing temperature during pyrolysis leads to higher SiO 2 concentration (ash content) and decreases biochar yield and carbon content, as well as the presence of functional groups. ...
Stormwater reuse plays a critical role under changing climates and increasing water demands. This study investigates the removal efficacy of lead (Pb²⁺) and ammonia (NH3) using sand and rice husk (RH) biochar for potential stormwater quality improvements and treatments. Column experiments combined with HYDRUS inverse modeling were conducted to optimize adsorption isotherms from breakthrough curves. Among linear and non-linear models, the Langmuir and Freundlich models performed better for sand and biochar, respectively. RH biochar showed much higher adsorption capacity of both Pb²⁺ (4.813 mg/g) and NH3 (6.188 mg/g). In contrast, sand showed a relatively limited adsorption capacity for Pb²⁺ (0.118 mg/g) and NH3 (0.104 mg/g). This can be contributed to higher pore size distribution, surface area, and the presence of different functional groups of biochar. The optimized adsorption coefficients and adsorption capacity parameters of sand and RH biochar by inverse modeling provided useful input for improving field designs. These findings will enhance the development of the best management practices (BMPs) for managing heavy metal and solute pollution in groundwater or stormwater low-impact development (LID) infrastructure systems.
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Bioretention systems use plants and soil media to treat pollutants in stormwater. Biochar can be an effective amendment to bioretention soil media for removing pollutants due to its adsorption properties. This study evaluates biochar as an amendment to bioretention soil media for the removal of contaminants in stormwater. Columns with varying ratios of biochar to bioretention soil media (0%, 25%, and 50% biochar) were tested to evaluate the removal efficiencies of copper, zinc, phosphorus, nitrogen, and microplastics from stormwater. Five trials were conducted with stormwater collected from parking lot runoff. Results show that the addition of biochar in bioretention systems improves the removal efficiency of zinc (average of 79% in columns with 50% biochar compared to 54% in columns without biochar) and copper (average of 73% in columns with 50% biochar compared to 25% in columns without biochar). Stormwater effluent from the biochar-amended columns also had significantly lower turbidity (21 NTU) than that of the control columns (58 NTU). Consistent leaching of nitrogen and phosphorus species was evident in the control as well as the biochar-amended columns, with average removal efficiencies of -1114% for total nitrogen and -703% for total phosphorus. Microplastics were effectively removed by all columns, regardless of biochar amendment, with an average removal of 86%. This study indicates that biochar has the potential to reduce metal concentrations in stormwater when used as an amendment to bioretention systems but has a limited impact on nutrients and microplastics.
... min, respectively, for Pb(II) removal, and 2107.92 and 1965.19 min, respectively, for Cd(II) removal. The lowest τ was shown by sand filters (38.07 and 60.49 min for Pb(II) and Cd(II) removal, respectively), indicating much quicker exhaustion of sand-filled filters as compared to BC-MPs filters (Hasan et al., 2021). The addition of either PE or NYL to sand and BCs resulted in substantial improvement in τ. ...
Extensive production and utilization of plastic products have resulted in the generation of microplastics (MPs), subsequently polluting the environment. The efficiency of biochars derived from jujube (Ziziphus jujube L.) biomass (300 °C and 700 °C) for nylon (NYL) and polyethylene (PE) removal from contaminated water was explored in fixed-bed column trials. The optimum pH for the removal of both MPs was found 7. Both of the produced biochars demonstrated >99% removal of the MPs, while the sand filter exhibited a maximum of 78% removal of MPs. BC700 showed 33-fold higher MPs retention, while BC300 exhibited 20-fold higher retention, as compared to sand filters, indicating the higher efficiency of biochar produced at higher pyrolysis temperature. Entrapment into the pores, entanglement with flaky structures of the biochars, and electrostatics interactions were the major mechanism for MPs retention in biochars. The efficiency of MPs-amended BCs was further explored for the removal of Pb(II) and Cd(II) in fixed-bed column trials. BC700 amended with PE and NYL exhibited the highest 50% breakthrough time (2114.23 and 2024.61 min, respectively, for Pb(II) removal and 2107.92 and 1965.19 min, respectively, for Cd(II) removal), as compared to sand filters (38.07 and 60.49 min for Pb(II) and Cd(II) removal, respectively). Thomas model predicted highest adsorption capacity was exhibited by BC700 amended with PE (584.34 and 552.80 mg g-1, for Pb(II) and Cd(II) removal, respectively), followed by BC700 amended with NYL (557.65 and 210.59 mg g-1 for Pb(II) and Cd(II) removal, respectively). Therefore, jujube waste-derived biochars could be used as efficient adsorbents to remove PE and NYL from contaminated water, while MPs-loaded biochars can further be utilized for higher adsorption of Pb(II) and Cd(II) from contaminated aqueous media. These findings suggest that biochar could be used as an efficient adsorbent to remove the co-existing MPs-metals ions from the environment on a sustainable basis.
... 11 Biochar has lately attracted attention as a universal material for environmental remediation due to its multiple benefits, and hence emphasis has been placed on using it in bioretention systems. [12][13][14] Several laboratory studies have recently been conducted to remove various contaminants (including biological pathogens) from stormwater using biochar in bioretention systems at varying ratios, such as nutrients, toxic metals, and E. coli. 13,15,16 Several reviews have been published related to stormwater management, with a main focus on pollutant sources of stormwater and their impacts on water quality. ...
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... Although no statistically significant differences were found between the steady-state and inhibition test periods, slightly lower removal efficiency after the inhibition test could suggest that metal removal was due to binding to the filter medium with a minor role of interactions with the active microbiota. Such high metal removal in biofilters has been reported before by Blecken et al. [49] for Cu (95.2 % ± 5.7) and Zn (97.4 % ± 1.7) and by Hasan et al. [50] for Cu and Zn (>95 %) in biocharbased biofilters have been reported to be efficient in the removal of [50]. ...
... Although no statistically significant differences were found between the steady-state and inhibition test periods, slightly lower removal efficiency after the inhibition test could suggest that metal removal was due to binding to the filter medium with a minor role of interactions with the active microbiota. Such high metal removal in biofilters has been reported before by Blecken et al. [49] for Cu (95.2 % ± 5.7) and Zn (97.4 % ± 1.7) and by Hasan et al. [50] for Cu and Zn (>95 %) in biocharbased biofilters have been reported to be efficient in the removal of [50]. ...
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Population growth and the associated increase in the use of Onsite Wastewater Treatment Systems (OWTS) in the Black Hills have been a reason for interest in nitrate contamination within the public water supply over the past few years. The main concern for the Black Hills is the presence of karst formation that all OWTS for wastewater travel faster, limiting the natural attenuation of wastewater contaminants. The treatment performance of common soils in the Black Hills and wood-based media was evaluated using soil column experiments and a numerical model, HYDRUS 2D. Nitrate treatment performances were evaluated using alluvial and cedar soils collected from the Black Hills, sand, woodchips (loose and dense), and biochar. This research investigated hydraulic and reaction parameters through a combination of experimental and inverse modeling approaches. A good agreement was obtained between the measured and model-predicted soil moisture content, with R² values ranging from 0.57 to 0.99. The model was calibrated using flow data and nitrate concentration data measured from leachate collected at the bottom of the experimental columns. Nitrate removal rates varied from 32.3% to 70%, with the highest removal rate in loose woodchips, followed by dense woodchip and biochar, and the lowest removal rate in alluvial materials. The biochar and loose woodchips removed an additional 20% compared to common soils, attributable to the enhanced denitrification rate due to higher water content and organic content. The use of woodchips and biochar should be implemented in OWTS, where there are known karst formations.
... Engineered media based on biochar (BC) offers desirable treatment functions in terms of porosity, cation exchange capacity, surface roughness, and surface functional groups. BC can remove complex contaminants in the subsurface treatment systems (Azeem et al., 2019;Hasan et al., 2021b;Tian et al., 2019). When functionalized with nanoscale metal or metal oxides, BC displays enhanced surface properties and higher GO treatment capacity (Hasan et al., 2020;Zhang et al., 2020). ...
Experimental data from fixed-bed column studies and a numerical model based on convection-dispersion equations were used to describe transport and retention of Graphene Oxide (GO) in sand, biochar (BC), and BC modified with nanoscale zero-valent iron (BC-nZVI). Three blocking functions, namely no blocking, site-blocking, and depth-dependent blocking, were used to analyze GO transport and retention behavior in each media as a function of Ionic Strength (IS). An inverse modeling approach was implemented to determine the attachment coefficient (Ka) and maximum solid-phase retention capacity (Smax). The Langmuirian attachment model with site-blocking function effectively described experimental GO breakthrough curves (R² ~ 0.70–0.99) compared to other models, indicating the importance of introducing a limit on the attachment capacity of the media. The Ka values for BC and BC-nZVI were significantly higher than sand, attributable to high porosity, roughness, and surface chemical properties. The models predicted an increasing trend in Ka (0.065 to 0.615 min⁻¹) in BC with increasing IS (0.1 to 10 mM), while Ka values decreased (2.26 to 0.349 min⁻¹) for BC-nZVI. A consistent increase in Smax was observed for both BC and BC-nZVI with increasing IS. Scenario analysis was conducted to further understand the effect of influent IS, GO concentration, and treatment depth. BC-nZVI exhibited a higher Ka and Smax and as a result, higher GO retention than BC at lower IS (0.1 and 1.0 mM). BC-nZVI had a relatively lower Ka (0.349 min⁻¹) at 10 mM IS, however, it outperformed BC when GO retention capacities are compared over a longer period attributable to a higher Smax (6.47). Complete GO breakthrough occurred in a 5 cm media after 350 and 465 days for BC and BC-nZVI, respectively at 10 mM IS and influent concentration of 0.1 mg·L⁻¹. GO breakthrough time increased with increasing treatment depth, however, the relation was non-linear.
Biochar from biomass and waste is a valuable component of various urban green infrastructures, including green roofs, permeable pavements, green walls, and green parking lots. Incorporating biochar into substrate mixtures...
