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© Envireau Ltd 2015 © Envireau Ltd 2015
Water Quality with emphasis on inorganic chemistry
David Banks Holymoor Consultancy Ltd
© Envireau Ltd 2015
Folkefiende
I tell you-the gravest possible danger to the
public health! All the nastiness up at Mølledal,
all that stinking filth, is infecting the water in the conduit-pipes leading to
the reservoir; and the same cursed, filthy
poison oozes out on the shore too-
Henrik Ibsen: An Enemy of the People (1882)
En Folkefiende
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Water quality
• The characteristics of a water, in relation to its suitability for a proposed use.
• A water may be of excellent quality for a one use, but poor quality as regards another...
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Water quality
What parameters are relevant for the following uses ? • Human potable water
– drinking water regulations
• Ground source heating scheme – temperature, dissolved gases, particles, iron
• Agriculture – depends on crop; nitrate, boron, temperature?, salinity
• Laundry – hardness, colour, Fe, Mn
• Bottled mineral water – mineral water regulations, market appeal
• Industrial cooling water, boilers – hardness, salinity
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Water quality parameters
• Microbiological
• Physical
• Aesthetic
• Organic chemical
• Inorganic chemical
• Radiological
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Water Quality in Norway
• In around 1990, it was accepted that 100,000 to 300,000 working days were lost per year due to waterborne infection (population c. 4.3 million)
• In 1993, 25% of population received water of unsatisfactory quality
From Kuusi et al. (2003) Incidence of gastroenteritis in Norway – a population-based survey. Epidemiol. Infect. 131: 591-597
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•Bacteriological non-compliance studied at 169 waterworks based on bedrock groundwater (largely untreated)
•50% had frequent or infrequent non-compliance regarding coliform bacteria
Sylvi Gaut (1999-2005) Drinking water wells in bedrock: Factors influencing microbiological quality. PhD. Department of Geology, Norwegian University of Technology and Science
DOG-NUTS
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Seasonality (these diagrams from Norway) (agriculture during summer, followed by autumn rains)
© Envireau Ltd 2015
Microbiology
• Microbiological – protozoa (Cryptosporidium, Giardia, amoebae) – bacteria – viruses – prions – biofilm-forming bacteria
• There are way too many potentially pathogenic species to analyse them all. We thus focus on indicator organisms... (e.g. of faecal contamination)
– e.g. faecal coliforms for pathogenic bacteria – e.g. Clostridium perfringens for protozoa (more resistant to
disinfection) – bacteriophages (e.g. coliphages) as indicators of viral
contamination
© Envireau Ltd 2015
Bacteria
• Total heterotrophic plate counts (THPC) are not necessarily good indicators of microbiological water quality. It is a good indicator of disinfection efficiency.
• Faecal bacteria are a better indicator of faecal contamination or pathogenic potential
– Faecal coliforms
– Faecal streptococci
– E. coli
• E.coli
– Lives in mammalian gut.
– E.coli and similar bacteria comprise only 0.1% of gut flora.
– Are mostly harmless or even beneficial.
– Can survive for short time out of body. Transmitted by faecal-oral route.
– A very few strains can be pathogenic
E. coli. Public domain image
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Protozoa: Giardia and Crytosporidium
• Ability to encyst. Periodically shed in faeces from domestic and wild and animals. Cysts or oocysts survive for prolonged periods (weeks or months)
• Cause gastrointestinal disorders. Pose a severe risk to immuno-compromised individuals.
• Rather resistant to chemical disinfection and sand filtration
• UV disinfection or membrane filtration can remove / inactivate oocysts Giardia: cyst diameter 8-12 µm. Giardia is the most common cause of
waterborne infection in the USA.
Cryptosporidium. Oocysts diameter 4-6 µm. 1993 outbreak in Milwaukee affected c. 400,000 people and cost over 96 million USD
Public domain image: CDC / Janice Carr / Stan Erlandsen Public domain image: CDC / Scale bar = 5 µm
Giardia Cryptosporidium
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Biofilms on rock walls – Hvaler tunnel
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Gallionella biofilm cultivated on glass slide suspended in hard rock borehole
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Physical Parameters
• Temperature – ground source heat
– agriculture
• Turbidity / Suspended solids – abrasion
– aesthetics
– well design and land stability
– 2 mg/L x 50 L/s = 100 mg/s
= 8.64 kg/d = 3.2 tonnes per year
http://www.watermonitoringequip.com
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Well collapse in Drammen, Norway
"geologists are going to go and look at the hole"
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Physical Parameters
• Electrical conductivity – indicator of salinity
– corrosivity
• Redox potential – may be an indicator of other “problem parameters” (iron, H2S, taste)
– may be an indicator of corrosivity
– “master variable” controls solubility of many other species (e.g. Fe, Mn, Ra, Ba, U)
• pH – may be an indicator of corrosivity
– “master variable” controls solubility of many other species (e.g. Al, Fe, Mn, Ca, CO2)
© Envireau Ltd 2015
Note that, for many field parameters, it’s really important to analyse on site
0
1
2
3
4
5
6
7
0 1 2 3 4 5 6 7
pH Field
pH
Lab
0
1
2
3
0 1 2 3
Alkalinity (meq/l) Field
Alk
alin
ity (
meq
/l)
Lab
Data from Sheephouse Wood mine water discharge, South Yorkshire
pH and alkalinity decrease on storage due to oxidation and hydrolysis of iron
4Fe2+ + 10H2O +O2 ↔ 4Fe(OH)3 + 8H+
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Throughflow cell
• To ensure minimal contact with the atmosphere, pumped water is often directed through a sealed cell, containing electrodes….
From “Water Wells and Boreholes” by Misstear, Banks and Clark (2006)
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Field “laboratories”
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Aesthetic parameters
• Odour – e.g. rotten egg smell caused by H2S
• Colour – may indicate surface water influence (humic acids)
– may be related to iron / manganese
• Dissolved gases
• Taste
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There’s nothing more irritating than negotiating with a village elder for access to his well....arranging a tank truck....calculating the amount of chlorine to add to the tanker....
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...installing a nice shiny PVC bladder tank....
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...and looking forward to distributing water to waiting refugees...
Photos by Dave Banks, Chad, 2004
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Inorganic Water
Chemistry
We’ve heard some scare stories from Norway in the 1990s.
BUT
A recent survey (Banks et al. 2015, Flem et al. 2015) found that, for inorganic chemical quality of public European tap water
•for most parameters a 99% (or better) degree of compliance was achieved. •1% non-compliance in EU member states for arsenic (1.6% when samples from non-EU states are also considered) •0.6% non-compliance in EU member states for sodium (1.0%) •0.2% 1% non-compliance in EU member states for uranium
Banks, D., Birke, M., Flem, B. & Reimann, C. (2015). Inorganic chemical quality of European tap-water: 1. distribution of parameters and regulatory compliance. Applied Geochemistry, 59, 200-210. doi: 10.1016/j.apgeochem.2014.10.016 (first published online 31 October 2014) Flem, B., Reimann, C., Birke, M., Banks, D., Filzmoser, P. & Frengstad, B. (2015). Inorganic chemical quality of European tap-water: 2. Geographical distribution. Applied Geochemistry, 59, 211–224. doi: 10.1016/j.apgeochem.2015.01.016
© Envireau Ltd 2015
A Lot of Processes Conspire to Determine the Chemical Fingerprint of a Water Sample
Rainfall
Water-mineral reaction in unsaturated zone
Interaction with soil and vegetation
Water-mineral reaction in saturated zone
Mixing with deep groundwater near borehole
Water treatment Use
Contamination (bacteria, NO3
-)
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Rainfall chemistry
H and O isotopes Nitrate, sulphate Oxygen Sodium and Chloride
•Concentrations of marine salts increase with proximity to the coast.
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Soil zone and vegetation: evapoconcentration and CO2 generation
Rainfall
Cl = 4 mg/L
1 L
Evapotranspiration 60%
Cl = 0 mg/L
0.6 L
Recharge
0.4 L
Cl = 4 mg
Cl = 10 mg/L
Soil
and a lot of CO2
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Water-rock interaction
Acid-base reactions (reactions using up CO2)
CaCO3 + CO2 + H2O Ca2+ + 2HCO3-
Calcite + carbon dioxide + water = dissolved cations + alkalinity
2NaAlSi3O8 + 2CO2 + 3H2O 2Na+ + 2HCO3- + Al2Si2O5(OH)4 + 4SiO2
Feldspar + carbon dioxide + water = dissolved cations + alkalinity + silica + clay
Redox reactions (reactions using up O2)
Oxidation of organic matter
CH2O + O2 CO2 + H2O HCO3- + H+
Oxidation of pyrite
2FeS2 + 2H2O + 7O2 2Fe2+ + 4SO42- + 4H+
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Contamination and mixing
Contamination -nitrate from agriculture / land use -nitrate / bacteria from latrines / septic tanks -industrial chemicals
Shallow groundwater: oxic, Ca-HCO3, nitrate, vulnerable to pollution
Deep groundwater: anoxic, saline (Na-Cl or Na-HCO3), no nitrate, H2S, methane, iron, manganese
Sea water intrusion
Na-Cl-SO4
Sea
Mixing & reaction
Run-in of surface water via well-head
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Typical natural water composition
Net result – Consumption of O2 and CO2
– Increase in pH, alkalinity
– Release of base cations (Ca2+, Mg2+, Na+, K+)
– Mixing with Cl- and SO4=
from deep brines or marine salts
Thus, the major ions in most groundwaters are dominated by
Cations
Ca2+
Mg2+
Na+ K+
HCO3-
Cl-
SO42-
NO3-
Anions
Ca2+
Mg2+
© Envireau Ltd 2015
Presentation of hydrochemical data Pie diagrams
If good ion balance, the cations and anions should form 180° of the pie each…
Borehole 2
Na+
K+
Ca++Mg++
SO4=
NO3-
Cl-
F-
Alkalinity
© Envireau Ltd 2015
Major Ion Chemistry is also important for practical purposes
Iron normally exists in water in its
reduced ferrous (Fe2+) form
on contact with oxygen, it oxidises to its insoluble ferric (Fe3+) form
which then reacts with water to produce ‘ochre’ flocs / precipitate
Fe3+ + 3H2O = Fe(OH)3 + 3H+
Note that bacterial biofilms may be involved
in some iron clogging problems
Fe2+ Fe3+ O2
=
http://www.filtersfast.com/forums/whole-house-water-filter-systems/863-whole-house-iron-filter.html
http://www.h2oequipment.com/water-problems/iron-bacteria/
© Envireau Ltd 2015
Major Ion Chemistry is also important for practical purposes
Manganese normally exists in water in its
reduced Mn2+ form
on contact with oxygen, it oxidises to its insoluble black dioxide
Mn2+ MnO2 O2
=
© Envireau Ltd 2015
Major Ion Chemistry is also important for practical purposes
Alkalinity
is the sum of alkaline species in water
[ ]
it describes the buffering capacity of the water (to withstand acidification)
At high pH and Ca2+ can contribute to calcite scale formation
Hardness is the sum of calcium and
magnesium in water (meq/L)
calcium and magnesium react with stearates in soap and prevent it from scumming
can also contribute to scaling
Ca2+ Mg2+ HCO3-
CO3=
OH-
Ca2+ + HCO3- + OH- = CaCO3 + H2O
© Envireau Ltd 2015
Major Ion Chemistry is also important for practical purposes
i.e. determining whether the water will cause scaling or corrosion:
Langelier Saturation Index (LSI) and Ryznar Saturation Index (RSI) are calculated using Ca, HCO3, pH and temperature and predict tendency for calcium scaling
Larson-Scold Corrosion Index (LSCI) is calculated using Cl-, SO4= and alkalinity
and predicts tendency for corrosion of mild steel
Abesser et al. (2014) Mapping suitability for open-loop ground source heat pump systems; a screening tool for England and Wales, UK. Quarterly Journal of Engineering Geology and Hydrogeology 47:373-380
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Water Treatment
• Did you know that most of UK’s water is dosed with phosphate to suppress plumbosolvency?
• No, neither did I !
Flem, B., Reimann, C., Birke, M., Banks, D., Filzmoser, P. & Frengstad, B. (2015). Inorganic chemical quality of European tap-water: 2. Geographical distribution. Applied Geochemistry, 59, 211–224. doi: 10.1016/j.apgeochem.2015.01.016
© Envireau Ltd 2015
A hydrochemical fingerprint
=
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...and, of course, water chemistry is important for health
A study in 1996-98 of Norwegian (mostly) private hard-rock boreholes
– 13.9% exceed the recommended action level for radon (500 Bq/L in Norway at that time)
– 16.1% exceed the drinking water norm for fluoride (1.5 mg/L)
– Considering pH, sodium, radon and fluoride together, 29.9% of all wells violate drinking water maximum concentrations for one or more of these parameters.
– 12% exceeded the WHO provisional guideline level of 30 µg/L for uranium
Banks, D., Frengstad, B., Midtgård, Aa.K., Krog, J.R. & Strand, T. 1998. The Chemistry of Norwegian Groundwaters: I. The Distribution of Radon, Major and Minor Elements in 1604 Crystalline Bedrock Groundwaters. The Science of the Total Environment, 222, 71-91. 2000 Frengstad, B., Midtgård Skrede, Aa., K., Banks, D., Krog, J.R. & Siewers, U. 2000. The chemistry of Norwegian groundwaters. III. The distribution of trace elements in 476 crystalline bedrock groundwaters, as analysed by ICP-MS techniques. The Science of the Total Environment, 246, 21-40.
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Fluoride
• Typical drinking water limit = 1.5 mg/l
• Excessive consumption can lead to dental or skeletal fluorosis in humans or cattle
• Sources: fluorite, apatite, some aluminosilicates (amphiboles)
• Characteristic of granites, gneisses and other metamorphic rocks, tuffs/volcanics (but not only these).
• Also found in many lithologies under low Ca, high pH conditions. May be concentrated by evaporative processes
Treatment: •Change of usage habits: avoid F-rich water for young children, avoid supplements •Low tech: Adsorption onto laterite-based ceramics, fish bone-ash •Small scale: Reverse osmosis, anion exchange •Large scale: co-precipitation with alumina / Nalgonda method
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Uranium
Not as rare (or as toxic) as you might think!
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Uranium
•Very soluble under oxidising conditions. •In Scandinavia, can get high concentrations especially in granites and acidic metamorphic rocks •Over 20 mg/L have been reported in groundwater from Finland •Elsewhere, can occur in a variety of lithologies •Is susceptible to evapotranspiration •Can be derived from apatite (amongst other sources) and apatite derived fertilisers may be a source of U
Frengstad, B.S. & Banks, D. (2014). Uranium distribution in groundwater from fractured crystalline aquifers in Norway. In: Sharp, J.M. (ed.) “Fractured Rock Hydrogeology”, International Association of Hydrogeologists Selected Papers, 20, 257-276. CRC Press/ Taylor & Francis, London. ISBN 9781138001596. doi: 10.1201/b17016-17.
N=476 Norway
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Uranium
•Very long half-life, so not very radioactive •Eventually degrades radioactively to radium and thence uranium •Chemotoxicity probably exceeds radiotoxicity
– No drinking water limit in EU – 20 µg/l in Canada – 30 µg/l in USA (USEPA) – 30 µg/l = WHO provisional
guideline – 10 µg/L in Germany
(Umweltbundesamt) – 15µg/L in Sweden
Livsmedelsverket (recommended)
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Mo
dif
ied
fro
m U
.S. G
eolo
gic
al
Surv
ey
The uranium-238 decay series
Radon gas 3.8 days half-life
Radon progeny: solid and short-lived polonium, bismuth, and lead isotopes
Radium-226
Uranium
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Radon (222Rn)
Part of Uranium-238 decay series
A radioactive gas which is moderately soluble in cold water (222 mL per L at 20°C)
A noble gas essentially non-reactive
A dense gas - 9.73 kg/m3 at STP (air = 1.217 kg/m3)
Decays by -particle emission with a half-life of 3.8 days
The leading cause of lung cancer next to smoking
Radon is found in rocks rich in radium.
Because radium behaves very differently (chemically) from uranium...
...there is not necessarily a very close correlation between uranium and radon in rocks
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For the treatment of: Gout
Rheumatism Arthritis
Nephritis Arterio-sclerosis
Diabetes etc etc
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Those were the days, my friend….
“All the next day the family is provided with two gallons of real, healthful radioactive water . . . nature's way to health….”
“Vita Radium suppositories. Recommended for sexually weak men. Also splendid for piles and rectal sores”
“Die Zellen werden mit neuer Lebensenergie geladen, die Bakterien in ihrer zerstörenden Wirksamkeit gehemmt.”
“mmm…chocolate”
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Radon
•Norwegian domestic water limit = 500 Bq/l
•De-gasses inside the home via showers, washing machines etc.
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Concentr
ation
Perc
entile
Rn Bq/L %
Radon in Norwegian crystalline bedrock groundwater: n=1326
Maximum recorded value 32,000
Bq/l in Iddefjord granite in an area
covered with thick marine clay
© Envireau Ltd 2015
Radon Guidelines
COUNCIL DIRECTIVE 2013/51/EURATOM:
• The long-lived decay products of radon are included in the evaluation of Total Indicative Dose as defined in the Drinking Water Directive (Council Directive 98/83/EC) (0.1 mSv/year)
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DWI Recommendation
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DWI Recommendation
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Hazard Maps . Report 24/3/15
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Radon: Water Treatment
•Relatively simple: – aeration
– plus storage to allow daughters to decay
– filtration (activated carbon / RO) to remove residual daughters
– Better ventilation in home
– Wear a gas mask in the shower
http://www.awqinc.com/clearadon_works.html
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Thanks for your attention
Thanks to: Bjørn Frengstad as co-author in a recent Geological Society talk on radon (from which some slides are taken) and the Sedatives® (new album soon to be available through several semi-reputable outlets)