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Aquifer Storage and
Recovery (ASR)
Design and operational experiences
for water storage through wells
Aquifer Storage and
Recovery (ASR)
Design and operational experiences
for water storage through wells
COLOPHON
Title
Aquifer Storage and Recovery (ASR). Design and operational experiences for water storage
through wells
Report number
PREPARED 2012.016
Deliverable number
Del. 5.2.2
Author(s)
Femke Rambags, MSc.
Dr. Klaasjan J. Raat
Koen G. Zuurbier, MSc.
Dr. Gerard A. van den Berg
Dr. Niels Hartog
Quality Assurance
Prof. Dr. Pieter J. Stuyfzand (KWR), Dr. Ing. Edvard Sivertsen (Sintef)
Cover figure
Koen G. Zuurbier MSc
Document history
Version Team member Status Date update Comments
V1 Femke Rambags Draft 07-Jan-2013
V2 Niels Hartog Draft 01-Mrt-2013
v3 Klaasjan Raat Final 18-Apr-2013
This report is: PU
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Preface
This document presents the opportunities that Aquifer storage and recovery
(ASR) projects may provide in urban, agricultural and industrial areas and is
intended to be used by urban water utilities (such as drinking water
companies), horticulture, industries and municipalities. At an introductory
level, this document summarizes the relevant information needed to consider
ASR projects. It introduces different ASR applications and two varieties on
the ASR concept (ASTR and ATR) . In addition, it presents showcases to
illustrate the diversity of methods that can be used. The report is built upon
(scientific) literature and operational experiences in the United States, the
Netherlands and Australia.
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Summary
Due to increasing climate variability and urbanization Europe is challenged with
obtaining a sustainable long term supply of fresh water. Larger fluctuations in
river discharge and salt water intrusion as a result of sea level rise have a direct
negative impact on the availability of fresh water for drinking water supply and
agriculture. At the same time larger seasonal variations in precipitation result in
an increased demand for fresh water during dry months. To ensure the
sustainable and sufficient supply of fresh water, an adequate and sustainable
adaptation strategy is required.
Temporal storage of water can help overcome this mismatch in water supply and
demand in time, allowing seasonally variable sources of water to be used as
reliable water supply. Therefore, one of the main concerns for the coming
decades is the provision of sufficient storage capacity to enhance the buffer
capacity of water supply systems. Aquifer storage and recovery (ASR) is often
cost–effective in comparison to aboveground alternatives that require the
construction of water treatment plants and surface reservoirs. In addition, there
may be insufficient space or desire for aboveground water storage, such as in
urban areas. In these cases, aquifer storage of water provides an attractive
alternative to increase storage capacity, as it results in a relatively very small
footprint aboveground.
ASR through wells is a specific type of technology for the infiltration of water
into aquifers, more generally known as managed aquifer recharge (MAR).
Recent technical advances and operational experiences have demonstrated that
the use of wells during ASR is a feasible and cost-effective method for recharging
aquifers, as confirmed by research pilots and operational plants worldwide.
Several relatively recent ASR concepts include aquifer storage transfer and
recovery (ASTR) and aquifer transfer recovery allow ASR to be applied for a
wider number of purposes under a wider range of conditions. The development
of these new techniques has led to improved ASR recoveries, satisfying water
demands. Recent developments in ASR techniques and applications demonstrate
that ASR is feasible in aquifers with very different settings, including conditions
that were previously deemed unsuitable. For example, ASR can be applied in
very thin aquifers and unconfined aquifers using horizontal wells. and in
brackish/saline aquifers using 'Multiple Partially Penetrating Wells' (MPPWs) or
separate wells that extract saline groundwater (Freshkeeper and Freshmaker
concepts).
Careful planning and design are essential to develop a successful ASR set-up.
Water availability, water demand and source water characteristics guide the
initial design and type of the ASR system to be constructed. The evaluation of
both hydrogeological aquifer properties and operational parameters is essential
to determine ASR feasibility and design criteria.
Future research and pilot projects are expected to increase application and
optimization of ASR. New developments will likely further enhance the number
of aquifer and water types suitable for ASR. Dissemination of knowledge of
existing and upcoming projects is required to facilitate project development and
risk assessment for new projects.
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Content
Preface 1
Summary 3
Content 5
1
Introduction 7
2
Aquifer storage and recovery: concepts and functions 9
2.1
What is ASR? 9
2.2
Reasons to implement an ASR system 9
2.3
ASR types using wells 10
3
Design of ASR systems 13
3.1
Defining recharge objectives 13
3.2
Water demand, availability and storage requirement 13
3.3
Hydrogeology 14
3.4
Selection of an ASR concept and preliminary design 15
3.5
Financial feasibility 17
3.6
Environmental feasibility 17
4
Operational experiences 19
4.1
Aquifer Storage and Recovery (ASR) 19
4.2
Aquifer Storage Transfer Recovery (ASTR) 21
4.3
Aquifer Transfer Recovery (ATR) 27
5
Conclusions 31
6
Literature 33
Appendices 35
I ASR in coastal aquifers for irrigation water supply (poster) 37
II Fresh maker and fresh keeper (poster) 39
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1 Introduction
Due to increasing climate variability and urbanization Europe is challenged
with obtaining a sustainable long term supply of fresh water. Larger
fluctuations in river discharge and salt water intrusion as a result of sea level
rise, land subsidence and a decrease in summer discharge by major rivers,
have a direct negative impact on the availability of fresh water for drinking
water supply and agriculture. At the same, prolonged droughts and increased
temperatures may result in an increased demand for fresh water (e.g.,
Intergovernmental Panel on Climate Change (IPCC) 2007; Schröter et al.
2005), resulting in a nett shortage of freshwater, even if yearly mean gross
precipitation tends to increase in some parts of Europe (KNMI 2008). An
adequate and sustainable adaptation strategy is required to ensure the
sustainable and sufficient supply of fresh water (European Environment
Agency, 2012). Temporal storage of water can help overcome the mismatch in
water supply and demand in time, allowing seasonally variable sources of
water to be used as reliable water supply. One of the main concerns for the
coming decades is, however, the storage capacity of water supply systems.
Storage of water: surface storage versus aquifer storage
Substantial amounts of water can either be stored aboveground or
underground in aquifers (aquifer storage). Surface storage in rivers, lakes or
ponds is widely applied and represents the majority of the installed global
storage capacity. Obviously, the amount of water that can be stored at the
surface depends on the dimensions of the basin, whereas subsurface storage
capacity is widely available. Therefore, aquifer storage is often cost–effective
as compared to aboveground alternatives that require the construction of
water treatment plants and surface reservoirs. In addition, there may be
insufficient space or desire for aboveground water storage, for instance in
urban areas. In these cases, aquifer storage provides an attractive alternative
to increase storage capacity, as it requires only a small footprint aboveground.
Aquifer storage and recovery through wells
The use of wells for aquifer storage and recovery (ASR, Figure 1) is a specific
approach for the infiltration of water into aquifers, which is more generally
known as managed aquifer recharge (MAR). While most aquifer recharge
still occurs through surface facilities like ponds and river channels, an
increasing amount of recharge occurs through wells. Recent technical
advances and operational experiences have demonstrated that ASR is a
feasible and cost effective method to recharge natural aquifers (Pyne, 2005;
Maliva and Missimer 2010). In this comprehensive guide the current
knowledge on ASR, as gained from research and operational experiences, is
collated. This overview is presenting the opportunities that ASR projects may
provide in urban areas, summarizing at an introductory level the relevant
information needed when considering an ASR project, introducing different
concepts of ASR and presenting showcases to illustrate the diversity of
methods that can be used for ASR. It is intended to be used by urban water
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utilities (such as drinking water companies), horticulture, industries and
municipalities.
Reading guide
In Chapter 2 different reasons for implementing an ASR system are
highlighted and different concepts of ASR are introduced. Subsequently the
relevant information needed to design an ASR system is summarized in
Chapter 3 at an introductory level, taking into account factors such as water
availability and demand, aquifer characteristics, costs and environmental
effects. To illustrate the diversity of methods that can be used for ASR, the
operational experiences are discussed and different showcases are presented
in Chapter 4. A short summary of the most important facts and suggestions
for dissemination of knowledge and ideas about expected developments and
possible future uses of ASR are presented in Chapter 5.
Figure 1: Example of an ASR application in Dutch Greenhouse areas. A surplus of
fresh roof water is injected and stored in a deeper confined aquifer. From this ASR
bubble, freshwater can be recovered in time of shortage.
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2 Aquifer storage and recovery: concepts
and functions
2.1 What is ASR?
In this document, aquifer storage and recovery (ASR) is defined as the storage
of water in a suitable aquifer through a well and the recovery of water using
the same well when needed to meet the demand of urban, agricultural,
ecosystem, industrial, recreational, emergency and other water uses. The
fundamental objective of an ASR system is to recover a high percentage of
injected water (i.e. to maximize the recovery efficiency) at a quality that is
(nearly) ready to be put to beneficial use.
Recent technical advances and operational experiences have increased ASR
performance, demonstrating that ASR is a feasible and cost-effective method
for freshwater supply.
2.2 Reasons to implement an ASR system
While there are numerous different reasons for implementing an ASR system,
most ASR applications are for seasonal and long-term, emergency storage of
water. Another common application of ASR is for improving the water
quality of the stored water. The most common reasons for implementing an
ASR are discussed below:
1. Securing and increasing water supplies:
Enhancing groundwater recharge and storage via ASR provides an important
potential source of water for urban and rural areas. We can distinguish three
types of storage:
• Emergency storage: The storage of water when available to provide an
emergency supply to meet demands when the primary source of
water is unavailable, due to accidental loss, contamination, a natural
disaster, maintenance activities or other unforeseen circumstances.
• Seasonal storage (or peak storage): This is the storage of water during the
wet season, when water is available or when water quality is good,
and recovery during the following dry season or other months when
water is needed.
• Long term storage (or water banking): Water banking is the long term
storage during wet years or when distribution facilities have spare
capacity, and recovery years later during extended droughts or when
facilities are inadequate to meet system demands.
2. Improving the quality of the stored water:
Water treatment capabilities of aquifers are substantial, particularly for
pathogen removal and reduction of the concentrations of disinfection by-
product (DBP’s).
ASR systems can therefore provide an inexpensive method
for meeting water quality standards.
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Other less common reasons for implementing aquifer recharge are:
• Improving groundwater quality,
• Preventing salt water from intruding into coastal aquifers,
• Management of undesired water (i.e. the reuse of effluents),
• Impeding land subsidence or to maintain or restore groundwater levels,
• Reducing evaporation losses of stored water.
2.3 ASR types using wells
Internationally there is a large and growing number of ASR application types,
using different types of well construction, target aquifers and water sources
to be stored. In this document a distinction is made between ASR sensu
stricto, and two varieties of this concept (based on Stuyfzand et al., 2012,
Figure 2):
• Aquifer storage and recovery (ASR): ASR is the ‘storage of water in
an aquifer through a well when water is available, and the recovery by
the same well during water demand’ (Pyne, 2005). The periods of
infiltration, storage and recovery are hereby typically separated. This
type of system is preferred when storage is the primary objective.
• Aquifer storage transfer and recovery (ASTR): ASTR is a system of
separate infiltration and extraction wells (“single purpose wells”),
with recovery immediately after or some time after infiltration is
stopped. The infiltration and recovery rates may differ (Stuyfzand et
al., 2012).
This type of system is preferred at sites where an ASR well will
experience problems with bubble drift as a result of regional flow.
Two separate wells for injection and recovery can also be preferred
when a partly continuous supply is required. Also, the use of separate
wells may be desirable to improve stored water quality by providing
additional residence time and to take advantage of self-purification
during transport in the aquifer.
• Aquifer transfer and recovery (ATR): ATR is a system of separate
infiltration and abstraction wells (‘single purpose wells’), with
simultaneous infiltration and recovery in which the infiltration and
recovery rates may differ.
This type of system is used when a continuous water supply is needed
and soil passage contributes to water quality improvements
(Stuyfzand et al., 2012).
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Figure 2 Schematic of the difference between ASR, ASTR and ATR in three aquifers
located underneath each other; 1=injection, 2=storage and 3=recovery during ASR
cycle 1, without regional flow, 4,5,6 = ditto during ASR cycle 2 with expanded
bubble; A, B, C = resp. injection, storage and recovery during an ASTR cycle, with
strong regional flow (From Stuyfzand et al., 2012).
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3 Design of ASR systems
There are many different factors that have to be taken into account when
designing an ASR system. At an introductory level, this chapter summarizes
the relevant elements that need to be taken into account to determine the
feasibility of an ASR project.
3.1 Defining recharge objectives
The design of an ASR system is initially driven by the objective of the system.
Therefore, the first step in designing an ASR system is to define the recharge
objectives (see paragraph 2.2 for recharge objectives). If there are multiple
objectives a distinction must be made between the primary objective of the
system and one or more secondary objectives. Although this may seem
obvious, it is important to carefully consider the different recharge objectives
and prioritize them because they largely dictate the requirements of the target
aquifer and water source.
3.2 Water demand, availability and storage requirement
In addition to the recharge objective(s), the design of an ASR system is driven
by the water demand and the availability of source water. These aspects
together define the storage requirement.
Water demand
Sufficient demand for the recovered water is a prerequisite for a successful
ASR system. One of the first steps in an ASR feasibility study is therefore to
evaluate the current and projected water demand. Ideally, daily water
demand data over a period of 10-15 years should be analyzed, including
averages, monthly variability, observed trends and expectations. These data
give insight into the volume of water required for recovery to meet system
demands and gives insights into the amount of idle supply, treatment and
transmission capacity required.
Water source for storage
For an ASR system to be feasible excess water needs to be available for
storage. Water from various sources, such as storm water, river water,
reclaimed water, mains water, desalinated seawater, rainwater or even
groundwater from other aquifers can be used for storage. For each potential
source water quantity, quality and associated variability should be carefully
evaluated in order to assess the suitability for ASR application. Similar to the
water demand, daily water supply data over a period of 10-15 years should
be analyzed, including average, monthly variability and trends, particularly
for temporally variable sources. Once recharge quality and quantity issues
have been addresses, it is possible to evaluate those times of the year when
recharge water is available in a useful quantity and with suitable quality.
Storage requirement
Based upon the variability in water demand, water supply and water quality
the amount of water that needs to be stored can be estimated (see example in
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Figure 3). Subsequently the rate at which the water must be recharged and
recovered during an operational cycle can be estimated. ASR systems are
sized with respect to injection and recovery rates and total recoverable
volume during an operational cycle; using the total recoverable volume and
rate of recharge and recovery the capacity of individual wells and the
required number of wells can be determined.
3.3 Hydrogeology
All ASR projects require a thorough characterization of the hydrogeological
conditions in the vicinity of the project site. Careful evaluation of the
hydrogeology is required because the recovery efficiency (see paragraph 2.1
for recovery efficiency) is dependent on the specific hydrogeology at the site.
Some of the main aquifer characteristics that should be assessed are:
- lithology and structural elements (fractures, bedding, joints),
- thickness, depth and extent of the aquifer,
- thickness, depth and extent of surrounding aquitards (if any),
- water quality in the target aquifer,
- geochemical composition (reactivity) of the aquifer matrix,
- salinity and water quality of ambient groundwater, and
- regional groundwater flow.
The goal of this investigation is to identify positive attributes of the
underground, such as zones with high porosity and permeability that would
be favorable for a particular recharge method, as well as negative attributes
Figure 3 Analysis of water availability (in this case precipitation) and demand shows
that there are 150 days of surplus (200 mm) and 120 days of shortage (120 mm). The
storage requirement is the amount of shortage of water that occurs when demand is in
excess of temporal availability (From: Knowledge for Climate, 2012)
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such as the presence of impermeable layers or the presence of contaminants.
The thickness, depth and extent of the target aquifer must be analyzed to
assess if there is sufficient storage space. The salinity of the native water
should be determined as the recovery efficiency of the system can be affected
by upward bubble drift or mixing between the infiltrate and native saline
groundwater. Upward bubble drift is the phenomenon in which density
differences between saline and fresh water cause the lighter freshwater to
float up (Figure 4). This may increase the risk of premature saline water
extraction during recovery. Mixing between the infiltrate en native saline
groundwater may result that water quality threshold values be exceeded,
reducing the total amount of water that can be recovered. Regional
groundwater flow should be analyzed because it can result in unacceptable
movement of infiltrated water as a result of lateral bubble drift (Figure 4)
when using a single-well ASR system and other. Other ASR types may be
considered to deal with regional groundwaterflow effects (see paragraph 2.3
for varieties on the ASR concept).
3.4 Selection of an ASR concept and preliminary design
The selection of a suitableASR system follows after determining the ASR
aspects discussed in the previous paragraphs:
• the recharge objectives
Figure 4 Loss of fresh water during recovery due to lateral groundwater flow (“bubble
drift”, left) and buoyancy effects caused by differences in density between fresh and
salt water (right) (Zuurbier, 2012)
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• the water demand
• availability and storage requirement
• selection of a suitable aquifer.
As briefly discussed in Paragraph 2.3 there are various ASR types. Choosing
the appropriate type is not always straight-forward. The main considerations
in choosing a concept include:
• The objectives of the ASR system;
• The presence or absence of a regional groundwater flow.
A simplified schematic for selecting an appropriate ASR system is given
below, based on these main considerations (Figure 5)
.
After selection of an ASR system a preliminary design can be set up, which
contains a layout of the facilities and controls. There are many choices for the
design of an ASR facility. A design might consist of shallow or deep
infiltration wells, vertical or horizontal wells, wells that can both inject and
recover water, or a combination thereof. Also, pre- and post treatment
facilities and monitoring wells may have to be incorporated in the design.
To guide the project design through the next project phases several aspects
should be clearly defined during the preliminary design phase, such as:
• the structure of the recharge-recovery cycles
• the period for which water is stored before it is recovered
• how to meet the quality criteria for the recovered water, or in other
words, when to stop recovery as based on on-line quality monitoring.
Figure 5 Simplified diagram for the selection of a suitable ASR system
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3.5 Financial feasibility
One of the main criteria to consider ASR a valid option, is whether it provides
water storage at lower costs than other storage options. The financial
feasibility of an ASR system is dependent on the total costs of the system, the
available volume for storage and the recovery efficiency of the ASR plant.
There is no universal recovery efficiency standard for a successful ASR
system. If modest recovery efficiency still provides the needed water at a
competitive price the system can still be a success.
3.6 Environmental feasibility
The construction of an ASR system could result in negative environmental
effects such as undesired changes in groundwater level in the surroundings
of the system or undesired changes in the salt-fresh water interface, or even
undesired water quality changes (for instance arsenic) . Prior to construction
an impact assessment should be performed in order to quantify these effects
and to determine if additional measures should be taken to mitigate these
effects. An environmental impact assessment is often required in order to be
granted an operational permit.
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4 Operational experiences
There is a large number of ASR schemes operational world-wide with a
growing variety of types. In Chapter 2 the different ASR types (ASR, ASTR
and ATR) were already introduced. In Chapter 4 the operational experiences
with these different ASR systems are presented and discussed. For each ASR
type different showcases are presented, as summarized in Table 1, to
illustrate the diversity of methods, source waters, hydrogeological settings
and end-uses of recovered water.
For each concept, the main applications and
technical and operational issues are discussed.
ASR concept Showcase
1
The Peace River ASR wellfield, Florida, United
States. A large scale ASR wellfield constructed
to meet supply contracts in times of low river
discharge.
2
A small scale ASR in a brackish aquifer using a
Multiple Partially Penetrating Well, Nootdorp,
the Netherlands.
4.1
Aquifer Storage
and Recharge
(ASR)
3
Freshmaker: ASR combined with extraction of
underlying brackish or saline groundwater,
Ovezande, the Netherlands.
4.2
Aquifer Storage
Transfer and
Recovery (ASTR)
4
ASTR for drinking water supply, combination
with reed-bed filtration, Salisbury, Australia.
4.3
Aquifer Transfer
Recovery (ATR)
5
ATR for treatment and as a buffer for drinking
water supply, North Holland, The Netherlands.
4.1 Aquifer Storage and Recovery (ASR)
As introduced in Chapter 2, Aquifer Storage and Recovery (ASR) is defined
as the ‘storage of water in an aquifer through a well when water is available,
and the recovery by the same well during water demand’ (Pyne, 2005).
Because wells are used for both infiltration and withdrawal they are referred
to as ‘dual purpose wells’.
How does it work?
Water is injected into an aquifer during wet periods, during periods of low
demand or when water quality is good. The injected water displaces the
naturally present water in the aquifer occupying a volume around the well
(Figure 6). Water is usually recovered during times of high water demand.
The periods of infiltration, storage and recovery are thus typically separated.
Table 1 Overview of showcases presented in Chapter 4
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Applications of ASR
Operational ASR systems are widely applied including countries such as
USA, Spain, Australia and the Netherlands. Most operational ASR systems
are for long-term or seasonal storage of water (Showcase 1 & 2). However an
increasing number of water managers is constructing ASR systems to ensure
reliability of supply during emergencies such as floods, contamination
incidents, pipeline breaks or to ensure supply during periods of maintenance.
Because of the wide range in applications there is also a wide range in size for
different ASR systems. ASR systems reported in literature range in scale from
single well systems for domestic or horticultural irrigation to ASR well fields
consisting of over 20 wells to meet water demand for urban areas or
industrial use (Showcase 4). Typical storage volumes for individual wells can
hereby range from 0.04 Mm
3
for a small ASR plant to 2 Mm
3
for a large plant
(Pyne, 2005). The largest ASR well fields in operation have design storage
volumes in excess of 4 Mm
3
,
enabling a seasonal water supply of 30 to 280
ML/d (Pyne, 2005).
Design issues
A fundamental objective of an ASR system is to recover a high percentage of
injected water at a quality that is ready to be put to beneficial use, i.e. to
maximize the recovery efficiency. The recovery efficiency of an ASR well is
dependent on the specific hydrogeology at the site and benefits from a low or
absent groundwater flow and low groundwater salinity. A low regional
groundwater flow prevents lateral bubble drift (Figure 4). The salinity of the
native water also impacts on the recovery efficiency of the system. Density
differences between saline and fresh water cause the lighter freshwater to
float up (upward bubble drift, Figure 4) increasing the risk of saline water
extraction during recovery. To maximize the recovery efficiency in situations
with upward bubble drift a technique has been developed which allows for
infiltration and extraction at different depth levels; the Multiple Partially
Penetrating Well (Showcase 2). Additionally, mixing between the infiltrate
Figure 6 Schematic representation of a basic ASR well (Pyne, 2005)
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and native saline groundwater may result in exceedance of the water quality
threshold values, reducing the total amount of water that can be recovered.
To maximize the recovery efficiency in brackish or saline aquifers different
techniques have been developed, such as the Freshmaker concept (Showcase
3). These techniques enable the expansion of (thin) freshwater lenses in
unconfined brackish or saline aquifers by combining artificial recharge with
interception of the underlying brackish water. The Freshmaker concept is
based on the Freshkeeper concept which prevents salinization of abstraction
wells by stabilizing the fresh-water interface through simultaneous
abstraction of the upper fresh and lower brackish groundwater (Appendix II).
The Freshmaker concept also allows for storage of fresh water in saline
unconfined aquifers. Most experience with ASR to date is with semi-confined
and confined aquifers in which the naturally present groundwater is
displaced in a lateral direction. Storage in unconfined aquifers can also be
feasible, but can be negatively impacted when the build-up of a mound in the
water table intersects either the ground surface or local drainage systems,
causing loss of the stored water due to surface drainage (Pyne, 2005). By
combining infiltration with extraction of native saline groundwater the
Freshmaker concept prevents the build-up of a groundwater mound.
Operational issues
One of the main problems in the operation of ASR systems is a decrease in the
capacity of the wells as a result of well clogging, especially when the
infiltration water contains significant concentrations of total suspended solids
in combination with a fine grained clastic aquifer. ASR wells are much less
susceptible to clogging than ATR and ASTR wells thanks to flow reversal.
Well clogging can be prevented by pretreatment of the infiltration water or by
frequent backflushing. A clogged well can be rehabilitated by physical
scrubbing, acidification, jetting and purging (Olsthoorn, 1982).
In addition, problems related to adverse changes in water quality in the target
aquifer are possible, which would necessitate post-treatment of the recovered
water and thereby make ASR less cost-effective. For example, a Mn-increase
in recovered water of an ASR pilot in the Province of Limburg above the
drinking water standard of 0.05 mg/L was one of the reasons to skip ASR as a
viable option for optimizing drinking water supply (Antoniou et al. 2012).
4.2 Aquifer Storage Transfer Recovery (ASTR)
As introduced in Chapter 2, Aquifer Storage Transfer Recovery (ASTR) is a
system of separate infiltration and extraction wells (“single purpose wells”),
with recovery immediately or some time after infiltration is stopped. The flow
rate of infiltration and recovery may differ (Stuyfzand et al., 2012).
How does it work?
Water is injected into an aquifer using an injection well during wet periods,
during periods of low demand or when water quality is good. The injected
water displaces the naturally present water in the aquifer establishing a
volume around the well (Figure 10). Water is recovered immediately after or
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some time after infiltration is stopped using a recovery well. The periods of
infiltration, storage and recovery can thus be separate or simultaneous.
Showcase 1:
The Peace River ASR well field, Florida, United States (based on Eckman
et al., 2004)
In the Southeast, Southwest and Western states of the United States ASR has
become a prevalent tool for providing a reliable supply of water throughout
the year. The Peace River ASR well field is comprised of 21 ASR wells (in
2004) with a combined capacity of 68 ML/day. It was built as an expansion of
the Peace River Regional Water Supply Facility. The principal objective of the
ASR system is to provide seasonal storage. Long term storage is a secondary
objective.
The water supply facility relies on surface water from the Peace River, a
variable water source with flows ranging from billions of liters per day to
periods of almost no flow. During a period of approximately 9 months raw
water from the Peace River is pumped to a 2.5 billion-liter, off-stream, raw-
water reservoir (Figure 7). Raw water is subsequently pumped to the water-
treatment plant, where it is treated using a conventional coagulation process.
Following treatment, the water is pumped to clear-water storage. From the
clear water storage water is delivered to meet supply contracts. The surplus
treated water remaining after delivery of contract water is injected into the
ASR wells. The ASR wells are designed for injection and recovery rates of
about 3,8 ML/day per well. In the periods when the facility is unable to
divert enough water from the river to meet supply contracts, water is
recovered from the same wells and used for delivery.
Figure 7 Peace River Water Supply Facility layout (Eckman et al., 2004)
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Showcase 2:
ASR in a brackish aquifer for irrigation water supply, Nootdorp, the
Netherlands
In November 2011 a new type of small-scale ASR installation for irrigation
supply was installed at Nootdorp, the Netherlands. In this system roofwater
from a greenhouse is collected and stored in a brackish aquifer. To prevent
recovery of brackish water as a result of buoyancy effects in the denser
brackish groundwater, 'Multiple Partially Penetrating Wells' (MPPW) are
used.
How does it work?
Greenhouse roofwater is collected in a small tank, able to store 20 mm of
precipitation. When the water in this storage tank reaches a maximum set
level, the water is first treated by slow and rapid sand filtration. Subsequently
the water is pumped into a 3 m high PVC stand pipe which provides the
pressure required to inject the water into the target aquifer with a flow rate of
10-15 m
3
/h. Recovery starts when the water level in the irrigation water tank
drops beneath a minimum set level. In order to prevent recovery of brackish
water due to buoyancy effects or seepage and to increase the recovery
efficiency, water is infiltrated and recovered using a 'Multiple Partially
Penetrating Well' (MPPW). This MPPW consists of four risers with screens at
different depths. This allows for injection and recovery at different depths.
After an initial injection and recovery phase using all well screens, fresh
water is primarily injected deep into the aquifer, while recovery takes place at
the aquifer’s top.
Figure 8 Principle of MPPW: injection takes place in all 4 wells but at a higher rate
at the bottom of the aquifer, whereas recovery takes place only in the upper part of the
aquifer (Zuurbier et al., 2012).
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Show case 3:
Freshmaker field pilot in Ovezande (Zuid-Beverland, the Netherlands)
ASR in brackish and saline aquifers often experiences problems as a result of
buoyancy effects and mixing with brackish and saline groundwater. The
Freshmaker concept increases small natural fresh groundwater lenses by
combining the interception of underlying saltwater using horizontal
abstraction drains or wells, with artificial recharge of fresh water. The
horizontal drains make the technique feasible in thin aquifers, which is a
prerequisite in many of the world’s delta areas.
In March 2013 the ‘Freshmaker consortium’ consisting of Meeuwse Goes,
KWR Watercycle Research Institute and ZLTO started the first field pilot for
aquifer storage using the Freshmaker concept in Ovezande, the Netherlands.
Using this technique it is aimed to store a significant volume of freshwater in
the subsurface (5.000 to 8.000 m
3
) for irrigation supply.
In Ovezande freshwater is taken from a watercourse during the winter period
and infiltrated into the aquifer using a horizontal drain at 7 m below surface.
To prevent upward bubble drift, the saltwater underlying the freshwater lens
is intercepted at approximately 16 m depth using a second horizontal drain.
The extracted saltwater is discharged to brackish surface water, at sufficient
distance from the freshwater intake. During the following dry season the
freshwater is recovered making extra water available for crop irrigation.
Figure 9 Schematic side view of the Freshmaker concept
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Applications of ASTR
ASTR system can be used for the same applications as ASR (e.g. seasonal,
long-term or emergency storage, for the reuse of effluents). However, the use
of separate wells for injection and recovery in ASTR may improve the system
performances (i.e. greater recovery efficiencies). Better system performances
can for instance be obtained at sites where an ASR well will experience
problems with bubble drift as a result of regional flow (for an explanation on
bubble drift see Fig.4). Two separate wells for injection and recovery can also
be preferred when a (partly) continuous supply is required. Additionally the
use of separate wells may be desirable to improve stored water quality by
providing additional residence time and to take advantage of an aquifer’s
natural self-purification.
Design issues
The success of an installed ASTR system is mainly dependent on the aquifer
characteristics and the water quality of the infiltration water. Both operational
experiences and research show that the elimination of pathogenic
microorganisms through natural filtering by the aquifer requires a certain
transport distance and residence time in the aquifer. Hydrological
calculations should be made to provide insight in the travel times of
infiltrating water.
When fresh water is infiltrated into a brackish or saline aquifer the density
differences between saline and fresh water causes the lighter freshwater to
float up (upward bubble drift, see Figure 4). In an ASR system this can lead to
a decreased recovery efficiency. In such situations the recovery efficiency of
an ASTR system can be maximized by injecting and extracting fresh water at
different depths in the aquifer.
Operational issues
One of the main challenges in the operation of ASTR systems is a decrease in
the capacity of the wells as a result of well clogging. Well clogging can be
prevented by pretreatment of the infiltration water or by frequent
backflushing. A clogged well can be rehabilitated by physical scrubbing,
acidification, jetting and purging (Olsthoorn, 1982)..
Figure 10 Schematic representation of an ASTR system (Adapted from Page et al., 2011)
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Show case 4
ASTR for water treatment (combined with reed-bed filtration), a project by
CSIRO in Salisbury, Australia (based on Page et al., 2010, Chapter 8)
Construction of the Aquifer Storage, Transfer and Recovery (ASTR) system in
Salisbury started in 2005 and was completed in 2008. The ASTR project was
developed to gain understanding of the recoverability of recharged water and
the water quality improvements of harvested, injected and recovered storm
water in order to develop management strategies for reliable, sustainable
production of water of potable quality sourced from storm water.
The storm water harvesting system consists of a weir which diverts water into
an in-stream basin which serves as an initial settling basin for the storm water
(see Figure 11). From the in-stream basin, water is pumped at 3 ML/hour to
the 48 ML holding storage until capacity of the holding storage is reached.
Water in the holding storage then flows by gravity into the cleansing reedbed.
The capacity of the reedbed is approximately 25 ML, and it has a surface area
of 2 ha. Water is pumped from the reedbed outlet to two storage tanks, and
from there it is pumped to the ASTR well field. The ASTR system comprises
four injection wells surrounding two recovery wells with 50 m inter-well
spacing. The well configuration was designed to produce a mean residence
time in the aquifer of 6 months. Water is recovered from the ASTR well field
back into two storage tanks, from where it enters the distribution pipeline
and is pumped to end-users.
The project has demonstrated that recovered water at the ASTR site generally
meets the Australian Water Recycling Guidelines without further treatment.
However, further research is needed to test the robustness of the concept, to
explore options for harvesting and use of storm water and to assess impacts
of its use on water distribution systems.
Figure 11 Schematic representation of the ASTR scheme in Salisbury, Australia
(From: Swierc et al., 2005).
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4.3 Aquifer Transfer Recovery (ATR)
As introduced in Chapter 2, Aquifer Transfer Recovery (ATR) is a system of
separate infiltration and abstraction wells
(‘single purpose wells’), with
simultaneous infiltration and recovery in
which the infiltration and recovery rates
may differ (Figure 12). This type of
system is preferred when a continuous
water supply is needed and aquifer
passage contributes to water quality
improvement of the infiltrate (Stuyzand
et al., 2012).
How does it work?
Water is injected into an aquifer,
displacing the naturally present water in
the aquifer.
The water flows through the aquifer
towards the abstraction well(s) (Figure 12).
Applications
The principal reasons for ATR applications are disinfection and leveling of
the water quality of the infiltrated water by aquifer passage, together with the
creation of a buffer to overcome short periods of water scarcity. Research at
an ATR site in the Netherlands (Showcase 5) has shown that extraction of
water can be continued for a period of at least one month when the
infiltration, for example in the case of an emergency, is discontinued. A
review by Stuyfzand et al. (2012) shows that ATR systems in the Netherlands
range from small scale systems with 4 injection wells to large scale systems
consisting of 20 injection wells with recovery wells on both sides of the
injection wells. The infiltration capacity of two currently active ATR systems
in the Netherlands ranges from 4 to 5.5 Mm
3
per year (Stuyzand et al., 2012).
Design issues
The success of an installed ATR system is mainly dependent on the aquifer
characteristics and the quality of the infiltration water. To eliminate
pathogenic microorganisms a certain transport distance and residence time in
the aquifer is required. In sandy aquifers a travel time of 60 to 100 days is
generally considered sufficient to remove viruses and bacteria by aquifer
passage and to safeguard microbiological safety of the water (Van der Wielen
et al., 2008). Hydrological calculations should be made to provide insight in
the travel times of infiltrating water.
Figure 12 Schematic representation of
an ATR system with two abstraction
wells (adapted from: Peters et al., 1998)
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Showcase 5
Deep infiltration Watervlak (DWAT), the Netherlands
The Provincial Water Authority of North Holland (PWN) started with the ATR
project DWAT in 1990. In a review by Stuyfzand et al. (2012) a short description of
this system is given.
The objectives of the DWAT system (Figure 12) were storage of water, disinfection,
attenuation of the water quality fluctuations in the infiltration water and to meet the
drinking water demand. The DWAT system is still operational, although with
reduced efficiency. The well field in the coastal dune area consists of 20 infiltration
wells with screens at 60-90 m below land surface. The system has a total infiltration
capacity of 5.5 Mm
3
per year (600 m
3
per hour). The maximum realized infiltration
is, however, 4.9 Mm
3
per year. Recovery takes place using 12 pumping wells with
screen at 55-80 m below land surface. The total withdrawal capacity of the system is
540 m
3
per hour. During normal conditions the DWAT system is in constant
operation with a production of approximately 510 m
3
per hour. On an annual basis
this amounts to 4.5 Mm
3
. Less water is abstracted than infiltrated (10% less) to
prevent the upconing of saline or brackish water and to allow for extraction in
periods when infiltration is discontinued (for example, in the case of an emergency).
Research has shown that when infiltration stops, water extraction can be continued
for a period of at least one month without extracting saline groundwater (Rolf et al.,
2010 and Stuyfzand et al., 2012).
Clogging is prevented by reversing infiltration and
recovery on a daily basis for about twenty minutes.
Figure 13 Left: Planar view of ATR well field Watervlak (DWAT). The 20 red triangles are
infiltration wells, blue dots are the 12 extraction wells.
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Operational issues
In the Netherlands several deep infiltration ATR pilots have been conducted
since the 1930’s. These initial pilots were without success due to severe
clogging of the wells. Only after numerous studies in the 70’s and 80’s did
drinking water companies dare to integrate ATR production with existing
techniques. An important ATR site is the one called “Watervlak” which was
installed by the Provincial Water Authority of North Holland (PWN,
Showcase 5). The key factor for this decision was the success in preventing
well clogging by advanced pre-treatment of the infiltration water in
combination with high-frequent backpumping. The pretreatment consisted of
subsequently settling, aeration, coagulation, rapid sand filtration and
activated carbon filtration.
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5 Conclusions
Research pilots and operational experiences have shown that ASR is a
feasible and cost effective method for freshwater supply. There are a large
number and growing variety of techniques that can be used for ASR. The
development of these new techniques has led to improved ASR performance
and demonstrate that recharge, storage and recovery by wells is feasible in
aquifers that were previously deemed unsuitable such as thin aquifers,
brackish or saline aquifers, and unconfined aquifers. Thus, it is proved that
ASR is feasible in a large variety of different settings.
Careful planning is essential to develop a successful ASR system. Recharge
objectives, water demand and source water characteristics guide the design
and type of ASR system to be constructed. Hydrogeological characterization
and operational parameters are essential to determine the feasibility of the
project and the design criteria. Also environmental effects and financial
feasibility must be considered.
Future research and pilot projects are expected to increase and optimize the
application of ASR. New developments will likely further extend the types of
aquifers and water types that can be used. Dissemination of knowledge of
existing and upcoming projects is essential as it will facilitate project
development and risk assessment for new projects. Within the EU FP7 project
DEMEAU, the integration of information on many different examples of
operational aspects of managed aquifer recharge systems, including ASR
plants, is currently prepared for dissemination.
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Appendices
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I
ASR in coastal aquifers for irrigation water supply
(poster)
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II
Fresh maker and fresh keeper (poster)
Intergovernmental Panel on Climate Change (IPCC) (2007) Climate Change
2007 - The Physical Science Basis In: Solomon S, D. Qin, M. Manning,
Z. Chen, M. Marquis, K.B. Averyt,M. Tignor, H.L. Miller (ed)
Contribution of Working Group I to the Fourth Assessment Report of
the IPCC, New York, USA, pp. 996.
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http://www.knmi.nl/klimaatscenarios/effecten/index.html. Cited
14-4-2011
Schröter D, Cramer W, Leemans R, Prentice IC, Araújo MB, Arnell NW,
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