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The 21st century water quality challenges for managed aquifer recharge: towards a risk-based regulatory approach



Sustained environmental and human health protection is threatened by ~350,000 chemicals available in global markets, plus new biological entities including coronaviruses. These water-quality hazards challenge the proponents of managed aquifer recharge (MAR) who seek to ensure the integrity of groundwater. A risk-based regulatory framework accounting for groundwater quality changes, adoption in subsurface attenuation zones, and use of advanced monitoring methods is required to support confidence in the sustainability of MAR.
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Hydrogeology Journal
The 21st century water quality challenges formanaged aquifer
recharge: towardsarisk‑based regulatory approach
YanZheng1 · JoanneVanderzalm2· NielsHartog3· EnriqueFernándezEscalante4· CatalinStefan5
Received: 27 February 2022 / Accepted: 11 September 2022
© The Author(s), under exclusive licence to International Association of Hydrogeologists 2022
Sustained environmental and human health protection is threatened by ~350,000 chemicals available in global markets, plus new bio-
logical entities including coronaviruses. These water-quality hazards challenge the proponents of managed aquifer recharge (MAR) who
seek to ensure the integrity of groundwater. A risk-based regulatory framework accounting for groundwater quality changes, adoption in
subsurface attenuation zones, and use of advanced monitoring methods is required to support confidence in the sustainability of MAR.
Keywords Water-resources management· Managed aquifer recharge (MAR)· Groundwater sustainability· Waterquality risks·
Attenuation zone
Managed aquifer recharge (MAR) is the purposeful recharge of
water to aquifers for subsequent recovery or environmental ben-
efit (IAH 2022). A rigorous environmental and social sustaina-
bility assessment of 28 schemes from 21 countries demonstrates
that MAR is a sustainable technology (Zheng etal. 2021). This
nature-based engineering approach is poised to play an increas-
ingly significant role in climate change adaptation through aug-
menting water supply and environmental flows, and recycling
treated wastewater. This essay calls upon hydrogeologists world-
wide to rise to the 21st-century water-quality challenges using
MAR, to maintain the integrity of groundwater resources and to
meet humanity’s demand for good quality freshwater.
Here it is argued that “novel entities” (NE), defined as “new
substances, new forms of existing substances and modified life
forms” (Steffen etal. 2015), need to be considered. These NEs
include “chemicals and other new types of engineered materials
or organisms not previously known to the Earth system as well
as naturally occurring elements (for example, heavy metals)
mobilized by anthropogenic activities” (Steffen etal. 2015).
Considering NEs means that proponents of MAR must go
beyond managing risks associated with known legacy pollutants,
such as hydrocarbons, pesticides, and disinfection by-products,
which can amount to several hundred regulated water quality
parameters (Escalante etal. 2020). It also requires addressing not
(yet) regulated, and sometimes novel (unknown) water quality
threats. Clearly, the capacity to manage current, emerging, and
unforeseen water quality risks is critical and relies upon chemical
and biological reactions to “purify” purposefully recharged water
within a subsurface attenuation zone, a concept originating in
Australia (Fig.1). To gain regulatory approval for this attenuation
zone, MAR practitioners have had to demonstrate, using
laboratory and field monitoring, the aquifer’s treatment capacity
and protection of the aquifer’s groundwater environmental values
beyond the attenuation zone. However, regulators may still be
inclined to regard the subsurface environment as “pristine”
and which should not be “disturbed” by any means. In reality,
the interaction of “unmanaged” recharge with a wide range of
anthropogenic activities has led to widespread groundwater
quality decline. This call to action begins with a historical
perspective on water quality issues frequently encountered
in MAR. Then, a resolution to tackle this challenge to ensure
sustained MAR implementation globally is discussed.
This article is part of the topical collection “International Year of
* Yan Zheng
1 School ofEnvironmental Science andEngineering, Southern
University ofScience andTechnology, Shenzhen518055, China
2 CSIRO Land andWater, Waite Road, Urrbrae,
SouthAustralia5064, Australia
3 KWR Water Research Institute, Groningenhaven 7, 3433, PE,
Nieuwegein, theNetherlands
4 Grupo Tragsa, Maldonado 58, 28006Madrid, Spain
5 Research Group INOWAS, Technische Universität Dresden,
01062Dresden, Germany
Historical perspective
An account of 60 years of global progress of MAR estimated
that purposeful recharge has reached 10 km3/year, ~2.4% of
Hydrogeology Journal
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groundwater extraction in countries reporting MAR, or ~1.0%
of global groundwater extraction (Dillon etal. 2019). A global
inventory of MAR, including 1,136 pilot and full-scale MAR
schemes from 60 countries (Fig.2, Stefan and Ansems 2018)
found that the influent water source, the main objective of
the scheme, and the final use of recovered water were well
reported (96, 82 and 73% of the total number of cases, respec-
tively). Although a detailed assessment of water quality (over
100 considered) was available in less than 5% of cases, water
quality changes were mentioned in many papers, especially in
conference papers and specific technical reports.
The important role of water quality investigations in MAR
is illustrated by a search of the Science Citation Index (SCI)
Expanded database (period from year 1900 to 12 February
2022) using combined topics of MAR and artificial recharge
(AR, as it was widely used in the past), with and without ‘water
quality’ as a topic. Just above one-third of publications, or 118
out of 391 papers, included water quality, and this proportion
remained fairly constant through the years. This is consistent
with presentations made at recent International Symposiums
on Managed Aquifer Recharge (ISMAR, in 2016 and 2019)
where ~34% mentioned water quality (125 out of 371 papers).
Presenters at ISMAR conferences (many MAR practitioners
do not publish SCI papers) acknowledge that water quality is
one aspect to be considered during MAR planning, construc-
tion, and operation. Studies aimed at improving understanding
of processes regulating water quality and clogging, managing
potential degradation or enhancing treatment, are pursued with
vigor. Comprehensive laboratory and field-scale experiments
which provide sufficient data for reactive transport modelling
(e.g., (Prommer and Stuyfzand 2005)) have been invaluable in
elucidating the controlling processes and developing manage-
ment strategies as required. This advancement has led to a recent
focus on strategies to optimize water quality treatment, such as
through advanced pre-treatment or by a combination of MAR
types (Hellauer etal. 2018), incorporation of reactive barriers
(Valhondo etal. 2020), or manipulation of the subsurface redox
zones (Bartak etal. 2017).
Water quality investigations during MAR projects serve mul-
tiple aims. While monitoring for regulatory compliance is a basic
starting point, it is not sufficient to adequately manage water qual-
ity. Here inorganic arsenic is used to illustrate the importance
of having a good understanding of hydrogeochemical processes
and their potential impact on MAR operations, with the ability to
make prediction a plus. Arsenic is such a highly toxic chemical
that even the regulatory limit of 10 μg/L adopted by most coun-
tries is not entirely protective of public health. In Florida (USA),
injecting oxygenated Tampa City supply water into the Suwannee
Limestone of the Upper Floridan aquifer containing pyrite (Price
and Pichler 2006) resulted in pyrite-oxidation-driven arsenic
release, with recovered water arsenic concentrations frequently
exceeding 10 μg/L and rising to as high as 130 μg/L (Jones and
Pichler 2007). Recharging a reduced, As-rich coastal aquifer in
Khulna, Bangladesh, with pond water resulted in arsenic concen-
trations in recovered water of >100 μg/L (Sultana etal. 2015) and
was attributed to reductive dissolution of As-bearing Fe-oxyhy-
droxide. A recent critical review on mobilization of arsenic and
other naturally occurring contaminants during MAR (Fakhred-
dine etal. 2021) concludes that arsenic poses the most wide-
spread challenge at MAR sites due to its ubiquity in subsurface
sediments and toxicity at trace concentrations; other geogenic
contaminants of concern include iron, molybdenum, manganese,
chromium, and fluoride. Fortunately, the same review points out
many approaches to mitigate MAR-induced arsenic problems
in recovered water, but these need process understanding and
predictive capability to ensure such risks are managed appropri-
ately. A key step in prediction is an early stage hydrogeochemical
investigation to characterize the aquifer and source of water for
recharge for conceptual understanding of geochemical reactions
and their potential impact (or risk).
Furthermore, risk-based management is essential for the
future of MAR (Imig etal. 2022), to ensure the protection of
public and environmental health, while also fully utilizing the
potential of MAR to provide natural treatment and facilitate recy-
cling and reuse (Fig.1). Increasing reliance on multiple source
Fig. 1 A schematic diagram illustrating how, with the example of an
infiltration pond, MAR has been used to purify purposefully recharged
water through a series of natural treatment processes occurring in the
unsaturated and saturated zones of an aquifer to facilitate the removal
of organic pollutants and pathogenic microbes. Here, it is recom-
mended that an attenuation zone (after NRMMC, EPHC, NHMRC
2009) is defined as an independent regulatory unit so that groundwater
quality beyond this zone is sustainably protected. Note that the diagram
is not to scale because the attenuation zone is usually confined beneath
the land owned by the MAR operator and normally <50–300 m
Fig. 2 Global inventory of MAR schemes presented as an online por-
tal with the database being continuously updated (IGRAC 2022)
Hydrogeology Journal
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waters (e.g., agricultural return flow, urban storm water, and
reclaimed water) also expands complexity in water-quality-risk
management and regulations for MAR, making the designation
of an attenuation zone in MAR regulation ever more relevant
(Fig.1). Such complex and uncertain risks can be dealt with
through decades of experience in water quality improvement and
management in MAR, furthered by targeted research—for exam-
ple, a study that evaluates the die-off of plant pathogenic bacteria
when stormwater is used to recharge a brackish anoxic aquifer in
the Netherlands can enhance confidence in the recovered water’s
intended use for irrigation (Eisfeld etal. 2021). Knowledge of
biodegradation of trace organic chemicals or contaminants of
concern has been advanced through the application of genomic
markers to infer the prevailing trophic state of microbial com-
munities in a MAR scheme, and subsequently, predict favorable
conditions for removal (Filter etal. 2021). While it is understood
that microbially mediated processes are an important control
on water quality, and in particular, water quality improvement,
approaches are required to assess aquifer microbial communi-
ties, their potential to augment treatment, response to changing
geochemical conditions, and ultimately the sustainability of treat-
ment. Leveraging the natural treatment capacity, where available,
allows for the design of a sustainable treatment train and avoids
overuse of energy-intensive engineered pretreatment without
overtreating water prior to MAR—for example, a current envi-
ronmental challenge is the widespread use and environmental
impact of perfluoroalkyl and polyfluoroalkyl substances (PFAS).
The fate of PFAS in MAR is uncertain and thus pretreatment or
posttreatment technologies may be required to manage this risk
(Page etal. 2019). Considering MAR as a step in a treatment train
enables one to manage the complex topic of water quality when
MAR alone cannot provide sufficient treatment, fate cannot be
predicted, or where water quality degradation may occur.
The natural treatment processes endowed by storage in the
aquifer are credited for helping the public to overcome the
“yuck factor” associated with recycling treated wastewater for
drinking water supply (Alley and Alley 2022). Faced with the
unknowns and uncertainties of regulated and unregulated water
quality threats, the assumption that storage time mitigates risk,
especially of pathogens, biodegradable organic matter, and trace
organic chemicals, is likely to hold (NRMMC, EPHC, NHMRC
2009), although more research is warranted to determine the
time scale and environmental conditions (Hübner etal. 2022)
for complete mineralization, including mostly unknown bio-
transformation byproducts (Ma etal. 2021). This should be of
interest to many water banking authorities such as those in the
western US states. The Kern Water Bank in the USA, initiated
in the early 1970s, recharged 1.13 billion m3 through 44 km2 of
recharge/spreading basins between 1995 and 2000 to alluvial
fan deposits of the Kern River. Meillier etal. (2008) used dis-
solved chlorofluorocarbons (CFC-11 and CFC-12) to estimate
groundwater ages of the target alluvial aquifer, finding that the
youngest apparent ages (younger than 1985) were found in the
shallow wells in the northern and central sections of the study
area where MAR is usually performed. The recovered water
here is suitable for irrigation but needs further treatment if used
for drinking. With the new analytical capability regarding con-
taminants of emerging concerns and microbial genomes, water
banking authorities, out of their fiduciary duty, can expand their
monitoring programs to track the recharged water as it “ages”
in the aquifer. For instance, it would be desirable to understand
the storage time required under particular redox conditions to
completely mineralize the myriad of trace organic contaminants.
The way forward
To enhance climate resilience and other social, economic, and
environmental benefits of groundwater through MAR, water
quality threats from novel entities need to be addressed to
maintain resource integrity. The aforementioned water qual-
ity challenges can be approached from a risk-based perspec-
tive grounded by precautionary principles, developed over time
through practice to solve clogging issues, and overcome eco-
nomic and policy barriers (Megdal etal. 2015). Strengthening
institutional capacity for regulatory frameworks for water alloca-
tion, permit granting and water quality protection are especially
relevant. It is important to balance the need to protect ground-
water quality integrity (ecocentrism ethic) and the desire to use
the natural treatment ability of the aquifer to improve water
quality (anthropocentrism ethic). It is worth noting that when
it comes to groundwater recharge laws in the United States, a
communitarian ethic has been suggested to underpin regulatory
processes (Owen 2021). Debate is encouraged on how to arrive
at a sensible regulatory framework for MAR to manage water
quality risks. Here, the perspective grounded in a communitarian
ethic and the precautionary principle provides a starting point.
The Australian risk-based approach to MAR (NRMMC,
EPHC, NHMRC 2009) is a model that sustainably protects
groundwater quality, accounting for water quality changes, both
improvements and deteriorations in the subsurface, and can be
expanded geographically because many countries use the highly
prescriptive approach of measuring compliance against uniform
water quality parameters. In Europe, both the development and
application of a legislative framework for MAR have varied
among different countries, with current legislation ranging from
strict and uniform water quality requirements to site-specific
risk-based evaluation in the Netherlands (similar to Australia). A
soon-to-be-effective European Union Directive 2020/741 has set
minimum requirements for water quality, as well as monitoring
and provisions on risk management applications for agricultural
use of reclaimed water. A risk-based directive specific for MAR
to further expand water reuse and recycling is a logical next step
for the EU and any designated regulatory entities to consider.
The way forward clearly depends on regulations that value
and enable the sustained use of natural treatment capacity pro-
vided by MAR, seamlessly integrated into a treatment train with
Hydrogeology Journal
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pretreatment or posttreatment technologies as required. Advanced
tools, including but not limited to real-time monitoring, data
assimilation, and reactive-transport modeling, are required to
predict the fate of chemicals and pathogens and to assess risks to
human health and aquifer integrity. Currently, the natural attenu-
ation or assimilatory capacity of aquifers has been relied upon for
the degradation of many organic pollutants. As such, one could
view this “attenuation zone” simultaneously as a subsurface natu-
ral treatment zone with a finite hydraulic retention time (Fig.1).
In addition to the determination of the hydraulic retention time,
the understanding of the fate of pathogenic organisms, includ-
ing attachment and inactivation and the variables that influence
these, is necessary. Surrogates that can be used for laboratory
and field verification, and genomic approaches for characterizing
the health of subsurface microbial communities, also provide a
broader perspective on the sustainability of microbial and trace
organic removal processes. The IAH-MAR Commission strives
to develop the body of scientific knowledge needed to have confi-
dence in enhancing the sustainable and beneficial use of aquifers
for humanity within the Earth’s safe operating space.
Acknowledgement We are grateful for the insightful comments pro-
vided by Dr. Peter Dillon and for discussions with Drs. John Cherry,
Bill Alley, Beth Parker, Junjiang Wang and Xiuyu Liang. Xiangshuan
Meng helped with drafting Fig.1.
Funding A DANIDA Fellowship 17-M08-GEU is acknowledged for
partial support.
Alley WM, Alley R (2022) The water recycling revolution: tapping into
the future. Rowman and Littlefield, Lanham, MD
Bartak R, Macheleidt W, Grischek T (2017) Controlling the formation
of the reaction zone around an injection well during subsurface iron
removal. Water 9:87
Dillon P, Stuyfzand P, Grischek T, Lluria M, Pyne RDG, Jain RC, Bear
J, Schwarz J, Wang W, Fernandez E, Stefan C, Pettenati M, van der
Gun J, Sprenger C, Massmann G, Scanlon BR, Xanke J, Jokela P,
Zheng Y etal (2019) Sixty years of global progress in managed
aquifer recharge. Hydrogeol J 27:1–30
Eisfeld C, van der Wolf JM, van Breukelen BM, Medema G, Velstra J, Schi-
jven JF (2021) Die-off of plant pathogenic bacteria in tile drainage and
anoxic water from a managed aquifer recharge site. PLoS One 16:1–22
Escalante EF, Casas JDH, Medeiros AMV, Sauto JSS (2020) Regulations
and guidelines on water quality requirements for managed aquifer
recharge: international comparison. Acque Sotter J Groundw 9:2
Fakhreddine S, Prommer H, Scanlon BR, Ying SC, Nicot J-P (2021)
Mobilization of arsenic and other naturally occurring contaminants
during managed aquifer recharge: a critical review. Environ Sci
Technol 55:2208–2223
Filter J, Zhiteneva V, Vick C, Ruhl AS, Jekel M, Hübner U, Drewes JE
(2021) Varying attenuation of trace organic chemicals in natural
treatment systems: a review of key influential factors. Chemosphere
Hellauer K, Karakurt S, Sperlich A, Burke V, Massmann G, Hübner U,
Drewes JE (2018) Establishing sequential managed aquifer recharge
technology (SMART) for enhanced removal of trace organic chemi-
cals: experiences from field studies in Berlin, Germany. J Hydrol
Hübner U, Wurzbacher C, Helbling DE, Drewes JE (2022) Engineering of
managed aquifer recharge systems to optimize biotransformation of
trace organic chemicals. Curr Opin Environ Sci Health 27(C):100343
IAH (2022) IAH Commission on Managing Aquifer Recharge. Inter-
national Association of Hydrogeologists. https:// recha rge. iah. org.
Accessed Feb 2022
IGRAC (International Groundwater Resources Assessment Centre)
(2022) MAR portal. https:// ggis. un- igrac. org/ view/ marpo rtal.
Accessed 14 Feb 2022
Imig A, Szabó Z, Halytsia O, Vrachioli M, Kleinert V, Rein A (2022)
A review on risk assessment in managed aquifer recharge. Integr
Environ Assess Manag 00:1–17. https:// setac. onlin elibr ary. wiley.
com/ doi/ pdf/ 10. 1002/ ieam. 4584. Accessed Sept 2022
Jones GW, Pichler T (2007) Relationship between pyrite stability and
arsenic mobility during aquifer storage and recovery in southwest
central Florida. Environ Sci Technol 41:723–730
Ma Y, Modrzynski JJ, Yang Y, Aamand J, Zheng Y (2021) Redox-
dependent biotransformation of sulfonamide antibiotics exceeds
sorption and mineralization: evidence from incubation of sediments
from a reclaimed water-affected river. Water Res 205:117616
Megdal SB, Gerlak AK, Varady RG, Huang L (2015) Groundwater gov-
ernance in the United States: common priorities and challenges.
Groundwater 53:677–684
Meillier L, Loáiciga HA, Clark JF (2008) Groundwater dating and flow-
model calibration in the Kern Water Bank, California. J Hydrol Eng
NRMMC, EPHC, NHMRC (2009) Australian guidelines for water recy-
cling, managing health and environmental risks, vol 2c: managed
aquifer recharge. Natural Resource Management Ministerial Council,
EnvironmentProtection and Heritage Council, and the National Health
and Medical Research Council. https:// recha rge. iah. org/ files/ 2016/ 11/
Austr alian- MAR- Guide lines- 2009. pdf. Accessed 27 Feb2022
Owen D (2021) Law, land use, and groundwater recharge. Stanford Law
Rev 73:1163
Page D, Vanderzalm J, Kumar A, Cheng KY, Kaksonen AH, Simpson
S (2019) Risks of perfluoroalkyl and polyfluoroalkyl substances
(PFAS) for sustainable water recycling via aquifers. Water 11:1737
Price RE, Pichler T (2006) Abundance and mineralogical association of
arsenic in the Suwannee Limestone (Florida): implications for arse-
nic release during water–rock interaction. Chem Geol 228:44–56
Prommer H, Stuyfzand PJ (2005) Identification of temperature-dependent
water quality changes during a deep well injection experiment in a
pyritic aquifer. Environ Sci Technol 39:2200–2209
Stefan C, Ansems N (2018) Web-based global inventory of managed aqui-
fer recharge applications. Sustain Water Resour Manag 4:153–162
Steffen W, Richardson K, Rockström J, Cornell SE, Fetzer I, Bennett EM,
Biggs R, Carpenter SR, De Vries W, De Wit CA (2015) Planetary
boundaries: guiding human development on a changing planet. Sci-
ence 347:1259855
Sultana S, Ahmed KM, Mahtab-Ul-Alam SM, Hasan M, Tuinhof A, Ghosh
SK, Rahman MS, Ravenscroft P, Zheng Y (2015) Low-cost aquifer stor-
age and recovery: implications for improving drinking water access for
rural communities in coastal Bangladesh. J Hydrol Eng 20:B5014007
Valhondo C, Carrera J, Martínez-Landa L, Wang J, Amalfitano S, Levan-
tesi C, Diaz-Cruz MS (2020) Reactive barriers for renaturalization
of reclaimed water during soil aquifer treatment. Water 12:1012
Zheng Y, Ross A, Villholth KG, Dillon P (2021) Managing aquifer
recharge: a showcase for resilience and sustainability. UNESCO, Paris
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... For the sake of the sustainable development and utilization of groundwater resources, the MAR (managed aquifer recharge) technology system has been widely promoted and applied in recent years [1][2][3][4]. Artificial ecological water supplement for groundwater restoration in the North China Plain is an important practice of MAR technology at the watershed scale. ...
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Managed aquifer recharge (MAR) refers to a suite of methods that is increasingly being applied worldwide for sustainable groundwater management to tackle drinking or irrigation water shortage or to restore and maintain groundwater ecosystems. The potential for MAR is far from being exhausted, not only due to geological/hydrogeological conditions or technical and economic feasibility but also to its lack of acceptance by the public and policymakers. One approach to enable the safe and accepted use of MAR could be to provide a comprehensive risk management, including the identification, analysis and evaluation of potential risks related to MAR. Aims of this paper are to review current MAR risk assessment methodologies and guidelines and summarize possible hazards and related processes. It may help planners and operators select appropriate MAR risk assessment approaches and support the risk identification process. In addition to risk assessment (and subsequent risk treatment) related to the MAR implementation phase, this review also addresses risk assessment for MAR operation. We also highlight limitations and lessons learned from application and development of risk assessment methodologies. Moreover, developments are recommended in the area of MAR-related risk assessment methodologies and regulation. Depending on data availability, collected methodologies may be applicable for MAR sites worldwide. This article is protected by copyright. All rights reserved.© 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).
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Managed aquifer recharge (MAR) can provide irrigation water and overcome water scarcity in agriculture. Removal of potentially present plant pathogens during MAR is essential to prevent crop diseases. We studied the die-off of three plant pathogenic bacteria in water microcosms with natural or filtered tile drainage water (TDW) at 10 and 25°C and with natural anoxic aquifer water (AW) at 10°C from a MAR site. These bacteria were: Ralstonia solanacearum (bacterial wilt), and the soft rot Pectobacteriaceae (SRP) Dickeya solani and Pectobacterium carotovorum sp. carotovorum (soft rot, blackleg). They are present in surface waters and cause destructive crop diseases worldwide which have been linked to contaminated irrigation water. Nevertheless, little is known about the survival of the SRP in aqueous environments and no study has investigated the persistence of R. solanacearum under natural anoxic conditions. We found that all bacteria were undetectable in 0.1 mL samples within 19 days under oxic conditions in natural TDW at 10°C, using viable cell counting, corresponding to 3-log10 reduction by die-off. The SRP were no longer detected within 6 days at 25°C, whereas R. solanacearum was detectable for 25 days. Whereas in anoxic natural aquifer water at 10°C, the bacterial concentrations declined slower and the detection limit was reached within 56 days. Finally, we modelled the inactivation curves with a modified Weibull model that can simulate different curve shapes such as shoulder phenomena in the beginning and long tails reflecting persistent bacterial populations. The non-linear model was shown to be a reliable tool to predict the die-off of the analysed plant pathogenic bacteria, suggesting its further application to other pathogenic microorganisms in the context of microbial risk assessment.
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Managed aquifer recharge (MAR) is known to increase available water quantity and to improve water quality. However, its implementation is hindered by the concern of polluting aquifers, which might lead to onerous treatment and regulatory requirements for the source water. These requirements might make MAR unsustainable both economically and energetically. To address these concerns, we tested reactive barriers laid at the bottom of infiltration basins to enhance water quality improvement during soil passage. The goal of the barriers was to (1) provide a range of sorption sites to favor the retention of chemical contaminants and pathogens; (2) favor the development of a sequence of redox states to promote the degradation of the most recalcitrant chemical contaminants; and (3) promote the growth of plants both to reduce clogging, and to supply organic carbon and sorption sites. We summarized our experience to show that the barriers did enhance the removal of organic pollutants of concern (e.g., pharmaceuticals and personal care products). However, the barriers did not increase the removal of pathogens beyond traditional MAR systems. We reviewed the literature to suggest improvements on the design of the system to improve pathogen attenuation and to address antibiotic resistance gene transfer.
The book tells the history, science, and politics of water reuse in an engaging manner accessible to anyone interested in water, the environment, or public health.
Managed aquifer recharge (MAR) systems provide effective removal of many water contaminants including suspended solids, organic matter, pathogens, and numerous trace organic chemicals (TOrCs). TOrC removal is primarily driven by biotransformations performed by subsurface microbial communities. However, variable extents of TOrC biotransformation have been reported across MAR systems. This review discusses major parameters affecting the biotransformation of TOrCs and summarizes recent efforts to enhance its efficiency in MAR systems. Approaches to enhance biotransformation of TOrCs during MAR include optimization of environmental conditions (redox conditions, substrate availability), inoculation of specific TOrC degraders and stimulation of degrader activity by providing growth substrates or co-factors. While concepts to optimize environmental conditions have been tested at different scale, inoculation and biostimulation approaches were mostly tested as a means to remove contaminants in biologically active sand filters or for the remediation of contaminated groundwater. Their application in MAR systems needs further research.
Trace levels of sulfonamide antibiotics are ubiquitous in reclaimed water, yet environmental pathways to completely remove those chemicals are not well understood when such water is used to restore flows in dried rivers. This study investigated sulfonamide sorption-desorption, biodegradation, and mineralization processes with seven sediments from a reclaimed water-dominant river. Batch experiments were conducted under oxic and anoxic (nitrate-reducing) conditions, and each removal process of sulfamethazine, sulfadiazine, and sulfamethoxazole (SMX) was evaluated individually at environmentally relevant concentrations (≤ 10 μg/L). Over 28 days, 44 ± 32% of the sulfonamides were biodegraded, while the full mineralization to carbon dioxide was < 1%. Around 5% of sulfonamides was removed via sediment sorption, with a positive correlation with sediment organic contents. Detailed investigation of SMX biodegradation revealed that although its transformation appeared to be faster in anoxic than oxic tests by day 2, it reversed over 28 days with a longer apparent half-life in anoxic tests (69 ± 25 days) than that in oxic tests (12 ± 11 days). This is attributed to the formation of reversible metabolites at denitrifying conditions, such as DesAmino-SMX of which the production was affected by nitrite levels. Despite measurements of three frequently reported metabolites, > 70% biotransformation products remained unknown in this study. The findings highlight the persistency of sulfonamides and their derivatives, with research needed to further elucidate degradation mechanisms and to perform risk assessment of reclaimed water reuse.
Population growth and climate variability highlight the need to enhance freshwater security and diversify water supplies. Subsurface storage of water in depleted aquifers is increasingly used globally to alleviate disparities in water supply and demand often caused by climate extremes including floods and droughts. Managed aquifer recharge (MAR) stores excess water supplies during wet periods via infiltration into shallow underlying aquifers or direct injection into deep aquifers for recovery during dry seasons. Additionally, MAR can be designed to improve recharge water quality, particularly in the case of soil aquifer treatment and riverbank filtration. While there are many potential benefits to MAR, introduction of recharge water can alter the native geochemical and hydrological conditions in the receiving aquifer, potentially mobilizing toxic, naturally occurring (geogenic) contaminants from sediments into groundwater where they pose a much larger threat to human and ecosystem health. On the basis of the present literature, arsenic poses the most widespread challenge at MAR sites due to its ubiquity in subsurface sediments and toxicity at trace concentrations. Other geogenic contaminants of concern include fluoride, molybdenum, manganese, and iron. Water quality degradation threatens the viability of some MAR projects with several sites abandoning operations due to arsenic or other contaminant mobilization. Here, we provide a critical review of studies that have uncovered the geochemical and hydrological mechanisms controlling mobilization of arsenic and other geogenic contaminants at MAR sites worldwide, including both infiltration and injection sites. These mechanisms were evaluated based on site-specific characteristics, including hydrological setting, native aquifer geochemistry, and operational site parameters (e.g., source of recharge water and recharge/recovery cycling). Observed mechanisms of geogenic contaminant mobilization during MAR via injection include shifting redox conditions and, to a lesser extent, pH-promoted desorption, mineral solubility, and competitive ligand exchange. The relative importance of these mechanisms depends on various site-specific, operational parameters, including pretreatment of injection water and duration of injection, storage, and recovery phases. This critical review synthesizes findings across case studies in various geochemical, hydrological, and operational settings to better understand controls on arsenic and other geogenic contaminant mobilization and inform the planning and design of future MAR projects to protect groundwater quality. This critical review concludes with an evaluation of proposed management strategies for geogenic contaminants and identification of knowledge gaps regarding fate and transport of geogenic contaminants during MAR.
The removal of trace organic chemicals (TOrCs) from treated wastewater and impacted surface water through managed aquifer recharge (MAR) has been extensively studied under a variety of water quality and operating conditions and at various experimental scales. The primary mechanism thought to dictate removal over the long term is biodegradation by microorganisms present in the system. This review of removal percentages observed in biologically active filtration systems reported in the peer-reviewed literature may serve as the basis to identify future indicators for persistence, as well as variable and efficient removal in MAR systems. A noticeable variation in reported removal percentages (standard deviation above 30%) was observed for 24 of the 49 most commonly studied TOrCs. Such variations suggest a rather inconsistent capacity of biologically active filter systems to remove these TOrCs. Therefore, operational parameters such as the change in dissolved organic carbon (ΔDOC) during treatment, hydraulic retention time (HRT), filter material, and redox conditions were correlated to the associated TOrC removal percentages to determine whether a data-based relationship could be elucidated. Interestingly, 11 out of the 24 compounds demonstrated increased removal with increasing ΔDOC concentrations. Furthermore, 10 compounds exhibited a positive correlation with HRT. Based on the evaluated data, a minimum HRT of 0.5-1 day is recommended for removal of most compounds.