Advanced treated municipal wastewater is an important alternative water source for agricultural irrigation. However, the possible persistence of chemical and microbiological contaminants in these waters raise potential safety concerns with regard to reusing treated wastewater for food crop irrigation. Two low-cost and environmentally-friendly filter media, biochar (BC) and zero-valent iron (ZVI), have attracted great interest in terms of treating reused water. Here, we evaluated the efficacy of BC-, nanosilver-amended biochar- (Ag-BC) and ZVI-sand filters, in reducing contaminants of emerging concern (CECs),
The regenerative role of biofilm in the removal of pesticides from stormwater in biochar-amended biofilters
Low-impact, green infrastructure systems such as biofilters, particularly when amended with biochar, can help address chemical pollution conveyed via stormwater that is increasingly posing a threat to aquatic ecosystems and groundwater quality. Although removal of organic contaminants including pesticides by biochar-amended systems has been studied, the role of a biofouling layer on contaminant removal, biotransformation, and filter lifetime remains poorly understood. This study evaluated the removal of the pesticides atrazine, imidacloprid, and clothianidin in biologically active biochar-amended columns through complete exhaustion of contaminant removal capacity. The resultant data indicate that biological processes accounted for 20–36% of overall removal in the biochar-amended sand columns. In addition, a combined target and suspect screening approach using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QToF-MS) was employed to evaluate the potential transformation of these three pesticides and release of the transformation products (TPs). All TPs detected in the effluent remained below 2.5% of their respective parent influent concentrations for the duration of the experiment. Furthermore, at a biochar application rate of 0.5 wt%, the presence of an active biofilm prolonged the filter lifetime by 1.8–2.3 times compared to a fouled but inactive filter, where removal was presumably dominated by adsorption only. Scenario modelling estimates showed that biochar-amended biofilters could last at least 17 years before exceeding aquatic life threshold values at biochar-application rates as low as 1 wt% (5 vol%) in a representative case study. Results of this study provide novel insight on pesticide TP formation in biochar-amended biofilters and estimation of filter lifetimes.
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- Award ID(s):
- 1844720
- NSF-PAR ID:
- 10328623
- Date Published:
- Journal Name:
- Environmental Science: Water Research & Technology
- Volume:
- 8
- Issue:
- 5
- ISSN:
- 2053-1400
- Page Range / eLocation ID:
- 1092 to 1110
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Escherichia coli (E. coli) and total bacterial diversity from wastewater effluent. Six experiments were conducted with control quartz sand and sand columns containing BC, Ag-BC, ZVI, BC with ZVI, or Ag-BC with ZVI. After filtration, Ag-BC, ZVI, BC with ZVI and Ag-BC with ZVI demonstrated more than 90% (> 1 log) removal ofE. coli from wastewater samples, while BC, Ag-BC, BC with ZVI and Ag-BC with ZVI also demonstrated efficient removal of tested CECs. Lower bacterial diversity was also observed after filtration; however, differences were marginally significant. In addition, significantly (p < 0.05) higher bacterial diversity was observed in wastewater samples collected during warmer versus colder months. Leaching of silver ions occurred from Ag-BC columns; however, this was prevented through the addition of ZVI. In conclusion, our data suggest that the BC with ZVI and Ag-BC with ZVI sand filters, which demonstrated more than 99% removal of both CECs andE. coli without silver ion release, may be effective, low-cost options for decentralized treatment of reused wastewater.Graphical Abstract -
Urbanization poses increasing threats to aquatic ecosystems, including increased chemical loading. Of relatively recent concern is the potential of urban stormwater runoff to facilitate the spread of microplastics (MPs), including tire wear particles. Previous studies have demonstrated the effectiveness of bioretention treatment systems in treating runoff, thereby reducing chemical loading into surface waters and preventing acutely lethal and sublethal effects to aquatic organisms. In this study, we aimed to determine the effectiveness and longevity of bioretention soil media (BSM) at various infiltration depths, including the shallower depth currently required by the Washington Department of Ecology (18”). Experimental columns containing three different BSM depths were dosed with roadway runoff at an accelerated rate to simulate nine water years in approximately 30 calendar months. The chemical and biological effectiveness of the columns in treating runoff was assessed by analyzing influent/effluent chemistry and characterizing the health of juvenile coho salmon (Oncorhynchus kisutch). Bioretention treatment efficiently removed copper, zinc, total PAHs, and total suspended solids (> 70% removal). Influent stormwater runoff was acutely lethal to juvenile coho salmon (88, 90, 100, and 56.3% mortality in four exposures across the nine accelerated years). However, bioretention treatment was protective of coho, altogether preventing mortality for all treatment depths in three exposures and all but one depth in the last exposure, likely due to overflow when influent flow exceeded the ponding capacity of some of the columns. This study is ongoing and will continue to assess bioretention effectiveness through 10 accelerated years. Future research should consider the ability of bioretention systems to remove MPs and associated pollutants in runoff and explore the fate of MP-contaminant complexes in bioretention systems. Although contaminants themselves, MPs can also act as vectors of other contaminants of concern in aquatic ecosystems, including antibiotic resistance genes (ARGs). Contaminants co-occurring in runoff (e.g., heavy metals) can stimulate the selection or amplification of these ARGs. If left untreated, runoff carrying ARGs to surface waters could increase resistance in environmental bacteria and risks to human health.more » « less
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Uranium (U) contamination of drinking water often affects communities with limited resources, presenting unique technology challenges for U 6+ treatment. Here, we develop a suite of chemically functionalized polymer (polyacrylonitrile; PAN) nanofibers for low pressure reactive filtration applications for U 6+ removal. Binding agents with either nitrogen-containing or phosphorous-based ( e.g. , phosphonic acid) functionalities were blended (at 1–3 wt%) into PAN sol gels used for electrospinning, yielding functionalized nanofiber mats. For comparison, we also functionalized PAN nanofibers with amidoxime (AO) moieties, a group well-recognized for its specificity in U 6+ uptake. For optimal N-based (Aliquat® 336 or Aq) and P-containing [hexadecylphosphonic acid (HPDA) and bis(2-ethylhexyl)phosphate (HDEHP)] binding agents, we then explored their use for U 6+ removal across a range of pH values (pH 2–7), U 6+ concentrations (up to 10 μM), and in flow through systems simulating point of use (POU) water treatment. As expected from the use of quaternary ammonium groups in ion exchange, Aq-containing materials appear to sequester U 6+ by electrostatic interactions; while uptake by these materials is limited, it is greatest at circumneutral pH where positively charged N groups bind negatively charged U 6+ complexes. In contrast, HDPA and HDEHP perform best at acidic pH representative of mine drainage, where surface complexation of the uranyl cation likely drives uptake. Complexation by AO exhibited the best performance across all pH values, although U 6+ uptake via surface precipitation may also occur near circumneutral pH values and at high (10 μM) dissolved U 6+ concentrations. In simulated POU treatment studies using a dead-end filtration system, we observed U removal in AO-PAN systems that is insensitive to common co-solutes in groundwater ( e.g. , hardness and alkalinity). While more research is needed, our results suggest that only 80 g (about 0.2 lbs.) of AO-PAN filter material would be needed to treat an individual's water supply (contaminated at ten-times the U.S. EPA maximum contaminant level for U) for one year.more » « less
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Laboratory based long-term batch incubation study was carried out to assess the methane (CH4) uptake or removal capacity in the landfill cover soil, biochar-amended cover soil, and methanotrophic-activated biochar-amended cover soil. The soil was amended with biochar or activated biochar in two proportions: 2% and 10% by weight. The results indicate that the methanotrophic-activated biochar-amended soil exhibited higher CH4 uptake and oxidation rates when compared to soil and biochar-amended soil. The 10% methanotrophic-activated biochar-amended soil showed the highest CH4 uptake with the CH4 oxidation rate of 518.6 µg CH4/g/day and the landfill cover soil showed the least uptake with the CH4 oxidation rate of 88 µg CH4/g/day. Overall, this study demonstrates that the biochar activated with methanotrophs expedited the CH4 uptake process when compared to non-activated biochar-amended soil that takes longer time for microbial colonization and acclimatization. Furthermore, column studies and field scale studies under dynamic environmental conditions are being undertaken to evaluate the maximum removal of CH4 under typical landfill conditions.more » « less
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null (Ed.)Biochar is a carbon-rich material prepared from the pyrolysis of biomass under various conditions. Recently, biochar drew great attention due to its promising potential in climate change mitigation, soil amendment, and environmental control. Obviously, biochar can be a beneficial soil amendment in several ways including preventing nutrients loss due to leaching, increasing N and P mineralization, and enabling the microbial mediation of N2O and CO2 emissions. However, there are also conflicting reports on biochar effects, such as water logging and weathering induced change of surface properties that ultimately affects microbial growth and soil fertility. Despite the voluminous reports on soil and biochar properties, few studies have systematically addressed the effects of biochar on the sequestration of carbon, nitrogen, and phosphorus in soils. Information on microbially-mediated transformation of carbon (C), nitrogen (N), and phosphorus (P) species in the soil environment remains relatively uncertain. A systematic documentation of how biochar influences the fate and transport of carbon, phosphorus, and nitrogen in soil is crucial to promoting biochar applications toward environmental sustainability. This report first provides an overview on the adsorption of carbon, phosphorus, and nitrogen species on biochar, particularly in soil systems. Then, the biochar-mediated transformation of organic species, and the transport of carbon, nitrogen, and phosphorus in soil systems are discussed. This review also reports on the weathering process of biochar and implications in the soil environment. Lastly, the current knowledge gaps and priority research directions for the biochar-amended systems in the future are assessed. This review focuses on literatures published in the past decade (2009–2021) on the adsorption, degradation, transport, weathering, and transformation of C, N, and P species in soil systems with respect to biochar applications.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d1ew00870f
