MANAGEMENTREVIEW
background
Within the EU a policy against acidification is implemented. One of the expected benefits of this
policy is a better (ground)water quality as compared to the situation without such a policy. In this
study a method is elaborated and proposed to calculate the resulting benefits of a better
(ground)water quality to the drinking water sector.
Reduced deposition rates of acids and nitrogen may yield three benefits to the drinking water
sector, particularly:
- The avoided costs for additional steps in the treatment of groundwater. These costs consist of
both capital investments in the drinking water treatment plant (DWTP) and operational costs.
- A longer lifetime for the drinking water infrastructure (wells, pumps, feeder pipes, DWTP,
distribution pipes, etc.) due to less corrosion, which reduces capitall losses.
- Lower or avoided maintenance costs for pumping wells.
The policy against acidification could thus prevent or at least reduce various increases in the
costs of drinking water production, transportation and distribution. This will particularly be the
case in those well fields that are vulnerable to the effects of acidification and eutrophication.
The scope of this project is to describe a method, applicable within the whole EU and easy to
implement, which yields a quantification of: (a) the effects of governmental actions against
atmospheric acidification, on the quality of groundwater; (b) the time scale within which these
effects are realised; and (c) the economical benefits for a well field and its drinking water
treatment plant.
With ‘describing a method’ we intend: to indicate how the method does work (on the basis of
which principles and which assumptions), which data-input is needed and which output is to be
generated by the method. Full elaboration of the method into a computer code should be the
scope of a next project. The governmental actions against air pollution addressed here, include
only those actions which reduce the atmospheric deposition of acidifying and eutrophying
compounds.
vulnerable well fields regarding effects on groundwater due to atmospheric deposition
In this study the focus is directed on well fields that are vulnerable to the effects of atmospheric
deposition of acidifying and eutrophying compounds within a time-span shorter than 100-200
years. Consequently well type fields pumping phreatic groundwater from relatively shallow
aquifers composed of unsolidated sands or limestone aquifers have been selected.
The most vulnerable fields are those which:
1. receive the highest load of atmospheric deposition of acidifying and eutrophying compounds;
2. have the shortest travel time of water from the land surface to the pumping wells;
3. lack reactive phases in both uppersoil and aquifer system.
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Figure 1. Vulnerable wellfields and physical-geographical regions
In figure 1 a map is shown with the vulnerable well fields in the Netherlands. The total amount of
vulnerable well fields in the Netherlands is 110 which equals 44 % of total (250) amount of
wellfields in the Netherlands.
aspects obscuring estimation of effect of policy against acidification
The effects on groundwater quality may be obscured due to intensified agriculture and
urbanisation. This pleads for research on well fields in nature reserves. However there we have to
be aware of other obscuring effects, especially due to declining groundwater tables which may
trigger the oxidation of organic matter and pyrites.These oxidation reactions may directly or
indirectly increase the concentrations of nitrate, sulphate, H+ (means decrease of pH), and
several other minerals. These concentration increases can easily be confonded with those due to
their increased atmospheric depostion during the past century, or their mobilisation in
consequence of the raised input of acidifying substances.
A well funded estimate of the contribution of atmospheric deposition to the concentration changes
of NO3 and SO4 and changes of total hardness (=Ca+Mg) in the raw water pumped at the
vulnerable well fields, during the past 40 years reveals that changes (increases) in atmospheric
deposition contributed:
- 0 - 45 % for NO3, with the lowest levels in nature reserves like the coastal dunes, where
denitrification in the aquifer is adequate, and with the highest levels in the large ice-pushed
hills;
- 25 - 95 % for SO4, with the lowest levels in areas with pyrite oxidation due to declined water
tables, and with the highest levels in the large ice-pushed hills;
- 0 - 95 % for total hardness, with the lowest levels in completely decalcified areas, and the
highest levels in the calcareous coastal dunes and limestone areas.
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Another aspect to be considered is that most effects due to acidification are irreversible. If for
example the equilibrium of carbonates in the soil has been changed it can not be restored by just
stopping acidification. Therefore the effect of the policy implemented after a long period of
acidification will be less then if implemented before acidification can effect the equilibrium.
effects on drinking water infrastructure
Changes in groundwater quality will affect drinking water production and its inherent
infrastructure. Our approach to estimate the effects on infrastructure follows the normal sequence
of process units or steps in drinking water production. The reason is that process steps do not
need to be influenced, if an effect occurs in one of the previous process steps, provided that
proper measures are taken there to prevent negative effects.
The following process units are discerned, within which various process steps can be present:
- the groundwater abstraction system, composed of pumping wells and transport mains to the
treatment plant;
- the drinking water treatment plant (DWTP) consisting of various treatment steps, which
transform groundwater into drinking water; and the distribution system of drinking water,
composed of pipelines, valves, pumps etc., for transport to the customers.
Figure 2. Representative groundwatertreatment in the Netherlands
Aeration with
cascades
clear water
tank
aeration
pump
pump
Primary secondary
filter
filter
The main effects of a change in groundwater quality on the drinking water production as a result
of the policy against acidification are:
- Clogging of groundwaterwells:
Clogging is a normal process in the exploitation of wells, affecting either the transport main (to
the treatment plant), the well screen slots or the surrounding aquifer pores or all. As a result,
the capacity of the well drops. This is initially compensated for by a higher pumping rate
leading to higher energy consumption. At a specific moment the well needs to be regenerated
or, when this fails, to be replaced by a new one. Obviously, an increased clogging rate leads
to higher exploitation costs.
The well clogging rate depends on various parameters. The following can be influenced in a
beneficial way by implementing a policy against atmospheric deposition of acidifying
substances and nitrogen:

pH: a higher pH reduces the dissolution rate of metals (specifically Fe and Al) and
CaCO3, and accelerates the mineralisation of organic material, thus leaving less oxygen
to react with dissolved iron;
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
-
-
-
-
nitrate: a lower concentration means less precipitation of ironhydroxides by reaction of
nitrate with dissolved iron, and – in some cases – less bacterial growth by lack of
nutrients.
Corrosion of DWTP and distribution system:
The water pumped can corrode groundwater abstraction systems. Corrosion mainly depends
on pH and salinity: a lower pH and higher salinity enhance corrosion.
Implementation of a policy against atmospheric deposition of acidifying substances and
nitrogen will reduce corrosion, because of the resulting pH increase and salinity decrease.
Extension of the existing plants with new treatment steps:
New treatment steps could be: (a) conditioning, like de-acidification or softening (if not
available); (b) membrane filtration: especially direct nanofiltration is a technique that seems to
be promising for the removal of organic micropollutants and multivalent ions; and (c) Granular
Activated Carbon (GAC) filtration for removal of organic micropollutants. Other techniques are
not commonly applied in groundwater treatment.
Waste (sludge) production, energy consumption and dosage of chemicals:
If the concentrations of manganese and iron decrease in the raw water the concentrations in
the backwash water will reduce and thus less waste of the process (residuals) needs to be
disposed. Every kg of iron and manganese in the raw water means various kg of waste!
Reduction of Existing Treatment steps:
A reduced atmospheric deposition of acidifying substances and nitrogen may lead to
decreasing concentrations of iron, manganese, organic matter and nitrogen as ammonia in
the raw water. This will lower the oxygen demand during filtration, and may thereby save the
last (second or third) aeration step.
Drinking water treatment plants (DWTPs) equipped with a conditioning step are able to adjust
the dosage of chemicals to cope with specific changes in water quality. This is an advantage
compared to DWTPs without conditioning step, which can only react on such changes by
adding a new process step. Changes in pH, TIC, Cl or SO4 concentration in the raw water
however lead to changes in chemical dosage and / or energy consumption, and in waste
production (in case of a pellet reactor for CaCO3 removal).
economic benefits of a policy against atmospheric acidification
The economic benefits of the policy against acidification relate to the lower costs with policy (WP)
as compared to the situation without (no) policy (NP).
The benefits considered are restricted to those for the drinking water sector. Other benefits,
particularly the positive health effects by an improved quality of drinking water, are not included in
this analysis.
Crucial in this analysis is that the benefits generally only become substantial on the medium and
long term. This is caused by:
- long travel times (years to decades) of the (rain)water from land surface to the pumping wells;
- a high buffering capacity of both the upper soil and aquifer system that can postpone the
acidification and eutrophication of groundwater for years up to millennia.
These “postponed” benefits raise the fundamental question how to value these benefits. In case
present and future benefits would be considered of equal importance, the sum of the benefits
would be infinitive. However, in financial and economic calculations the Net Present Value (NPV)
method1 is commonly used. In this method benefits (or costs) are given a lower value when they
occur in later years. Table 1. illustrates these values for different years and for two different
interest rates.
The table shows that at a low interest rate (3.75 %) the NPV reduces the benefits to 20 % in year
50. At a double interest rate (7.5 %) the NPV in this year becomes marginal. The total sum for the
first 50 years is still substantial for the first 50 years, but becomes little or even marginal after 50
1
The formulate used is X t=0= X t / (1+i) t ; t is the year and i for interest rate
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years. The table also clearly demonstrates that the choice of the interest rate has a considerable
effect upon the NPV values.
Table 1: Examples for the Net Present Value method
Interest rate
After individual years
%
0
5
50
3.75
1
0.85
7.5
1
0.73
sum for years
100
0-50
51-100
0.20
0.04
25.6
4.9
0.04
0,002
15.7
0.6
It is proposed to follow the above described approach to identify the interest rate to be used in the
benefits of the policy against acidification, where we deal with future capital costs. The Dutch
Central Planning Agency (CPB) estimates this (basic) cost at 3,25 %2. The water companies can
be a (semi) public institution or a (large) private enterprise.
Various Dutch Ministries and Research Institutions collaborated in a report on the costs and
benefits of environmental policy3. The interest rate proposed is based on the percentage at which
the national government borrows money in the market. This rate varies with time. Capital costs
also differ per type of borrower, being a government, enterprise or individual (consumer). This is
explained by the risks being different to the lender (usually a bank).
approach for estimating the effect of the policy against acidification
Adagio molto 21 stands for “Atmospheric Deposition And its Groundwater qualIty Offences;
Modelling the Long Term Overall effects on the drinking water infrastructure in the 21st century”.
This is the name of the method/program we propose, to calculate the quality changes of
groundwater due to changes in atmospheric deposition in the 21st century.
The normal significance of “Adagio molto”, being “very slowly” and “in an easy graceful manner”,
also applies to the low speed of these water quality changes in well fields, and to the easy and
graceful way to calculate these changes.
The program consists of two parts:
1. groundwater quality modelling;
2. modelling the effects on drinking water infrastructure and economic benefits
Adagio 21 calculates the quality changes of groundwater due to changes in atmospheric
deposition, and their effects on drinking water treatment and infrastructure, with the resulting
economic benefits.
Adagio Molto 21 is composed of 13 subprograms (Figure 3). It will consist of a user-friendly
interface, made in Microsoft’s spreadsheet EXCEL with Macro’s in Visual Basic. It includes some
of the features of the Easy-Leacher program and PHREEQC-2 to calculate the effects on the
groundwaterquality.
“European co-ordination Scenario”, mid-long term, excluding inflation effects
The Dutch ministry of Spatial Planning and Environment (VROM), Kosten en baten in het
milieubeleid, definities en berekeningsmethoden, publication no. 1998/6
2
3
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Figure 3 Set up of Adagio Molto
8. Input Water treatment
(EXCEL)
Corrosion
guidelines
9. Water
Treatment
(EXCEL)
Specifics
applied
Processes
10 output
water
treatment
EU standard
11. Input Economic benefits
(EXCEL)
Investment
specifics
12. Economic
benefits NPV
(EXCEL)
13 output
economic benefits
Exploitation
specifics
We will adapt the method proposed, if necessary and possible within the time limits posed by this
project, in consequence of the comments received from the participants of the workshop to be
held on 2 and 3 October 2002. For that purpose we ask the participants of the workshop to
answer the questions in chapter 6 and send their answer to the authors of this report.
Expertview on economic benefits in the Netherlands
In order to get a clue of the benefits to be expected in the Netherlands we made a global
estimation based on assumptions that are thought to be representative for the situation in the
Netherlands. For this aim we estimated the development of the groundwater quality between
1900 and 2200. In figure 3 it is shown that the initial waterquality will first continue deteriorating
but will improve on the long term. The groundwater quality will not reach the initial value.
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Groundwater quality
(% of initial value)
120
100
80
60
40
20
0
1800
1900
2000
2100
2200
2300
year
Figure 4 Development of groundwater quality in the Netherlands
with policy
The assumptions that are made and thought to be representative for the situation in the
Netherlands are:
- 110 vulnerable wellfields in the Netherlands at a maximum can
be influenced; Each well field
No policy
exists of 10 wells and is connected to 400 km of distribution mains;
- effects will commence after 50 years or after 100 years for all vulnerable wellfields; Therefore
the net present value at an interest rate of 3.75 % is presented(see table 1);
Start
of policy
- in 50 % of the DWTP investments
in the
treatment system are required;
- in 50 % of the wellfields the clogging rate will double;
- in 25 % of the distributionsystems the lifetime of mains will be reduced from 100 years to 75
years;
- in 25 % an increase of 10 % sludge production will occur;
- in 25 % of the wells an increase of 10 % aeration energy is required;
- horizon of NPV is 200 years.
In Table 2 the annual costs (benefits), the investments and the resulting net present value is
presented in the case the effects will commence after 50 years and in the case the effects of the
policy can be measured after 100 years.
Table 2. Estimation of total benefits for drinkingwater treatment of policy against
acidification in the Netherlands
costs (€ )
annual costs
Clogging of wells
Corrosion of DWTP and distribution (reduction of lifetime)
Extra sludgeproduction en energyconsumption
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275.000
8.100.000
100.000
costs (€ )
annual costs
investments (every 50 years)
New processes in DWTP
total Net Present Value (200 years)
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137.500.000
effect after 50
year
effect after
100 year
60.400.000
9.600.000
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