PURE WATER SEMINAR

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PURE WATER SEMINAR

• An Educational Overview of water purification
  techniques and applications in the laboratory
  environment

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Our Objectives Today

• Understand why water purification is required.
• Cover the basic technologies, and International
  standards involved in water purification.
• Know what questions to ask when looking for a
  water system.

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Impurities to deal with
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The Water Cycle
Clouds
Evaporation
Evaporation
Rain
Rain
Soil
Rivers
Seas Oceans
Lakes
Rocks
The Land
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Impurities in Municipal Water

• Dissolved inorganic salts
• (anions cations)
• Dissolved organic compounds
• Suspended particles and colloids
• (organic and inorganic)
• Micro-organisms
• (bacteria, virus, algae, micro-fungi etc)
• Pyrogens
• Dissolved gases

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IN SOLUTION
organic molecules
inorganic ions

-
COLLOIDS
GASES

CO2, O2







IN SUSPENSION
particulate matter
Micro-organisms
bacteria
algae
viruses
microfungi
pyrogens
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Dissolved inorganic salts

• Calcium and magnesium bicarbonate, CA(HCO3)2 and
  Mg(HCO3)2 temporary hardness
• Calcium and magnesium sulphate and chloride CaSO4
  and CaCl2 permanent hardness
• Sodium and potassium salts
• Iron salts, Silicates, Chloride and sulphate
• Nitrates from fertilisers
• Phosphates from detergents and fertilisers

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Dissolved organic compounds

• Naturally occurring, e.g. humic and fulvic acids,
  from decay and vegetable matter
• Synthetic e.g. detergents, pesticides, solvents
• Derived from water treatment processes e.g.
  Trihalomethanes (formed from action of chlorine
  in organics)

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Suspended particles

• Inorganic, e.g. sand, silt
• Naturally-occurring organics, e.g. vegetation
• Industrial effluent e.g. from paper manufacture

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Dissolved gases

• Mainly oxygen (O2), carbon dioxide (CO2) and
  nitrogen (N2) from natural sources
• - CO2 behaves as a weak anion
• - O2 and N2 cause foaming in solutions

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Micro-organisms

• Virusses, Bacteria, Algae, Fungi, Protozoa
• - bacteria are the major micro-organism of
  concern in water purification
• - Municipal water treated with Cl2 to keep
  bacterial levels down

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Cell Debris Impurities

• Pyrogens (endotoxins)
• Nucleases (RNase/DNase)
• Proteases

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Purification technologies
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Purification technologies

• Filtration / Adsorption
• Reverse osmosis (RO)
• Ion-exchange (IX)
• UV irradiation/photo-oxidation (UV)
• Recirculation (dead volume)

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Purification technologies

• It is essential to use a combination of
  techniques to ensure that ultra pure water is
  ultra-low in impurities
• Reverse Osmosis is the single most effective
  technique to remove impurities including ions
• Ion-exchange, UV are also used to achieve higher
  level purification, including removal of low
  molecular weight ions and trace ions.

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Complimentary Technologies
GASES
PARTICULATE
COLLODIAL
MICRO-ORGANISMS
ORGANIC
INORGANIC
DEPTH FILTRATION MICRO FILTRATION ULTRA FILTRATI
ON REVERSE OSMOSIS ION EXCHANGE ELECTRICAL DEI
ONISATION ADSORPTION UV IRRADIATION
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Filtration
After
Before
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Filtration

• Multi-media depth filters (industrial)
• Pre-filter (10 to 20 ?m)
• Micro (MF), 0.1 to 1.0 ?m for bacteria removal
• Ultramicro (UMF), 0.05 ?m
• Ultra (UF), 5000 Dalton for viruses pyrogens
• RO gt 1 nm

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Adsorption

• Granular activated carbon removes
• Dissolved organics
• Free and combined chlorine
• Used prior to RO membranes, in polishing loops
  and in composite vent filters used on reservoirs

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Adsorption
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Reverse Osmosis (RO)
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Osmosis/reverse osmosis
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RO spiral-wound membrane
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Reverse Osmosis
RO Membrane
Product
Feed
Ions Particles Organics Micro-organisms Gases
Ions lt5 Low MW Organics Gases
Reject Ions gt95 Organics
Particles Micro-organisms
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RO removal performance

• TDS (inorganic ions) up to 98
• Colloids, bacteria, 99.5
• Pyrogens and viruses
• Silica 95-98
• Molecular wt. cut-off 100-200

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Reverse Osmosis (RO)

• Membrane process
• Application of pressure forces water from feed
  water through membrane to form the permeate
• Contaminants do not pass and are accumulated in
  the concentrate

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RO Feed requirements and flow

• Feed water tolerances
• 1000ppm TDS
• lt0.5 ppm free chlorine
• lt 10 fouling index test
• Flow-rate is relatively slow and dependent on
  pressure and temperature
• Minimum freed pressure is 4 bar (60psi)

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RO Feed requirements and flow
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Deionization
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Ion

• An atom or group of atoms which has gained or
  lost one or more electrons
• Cation positively charged
• Anion negatively charged

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Ion exchange (IX) general

• Reversible chemical process in which resins
  remove ionic impurities from water.
• Resins are spherical beads of synthetic,
  insoluble polymer that carry ionic side-groups
• Cation resins exchange cations
• Anion resins exchange anions

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IX cation and anion exchange
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Ion exchange (IX) continue

• Used separately the resin will condition the
  water
• Used together resins purify the water
• Resins will become saturated with impurity ions
  exhausted
• Resins can be regenerated by treatment with
  appropriate chemicals
• Cation resin with hydrochloric acid (HCl)
• Anion with sodium hydroxide (NaOH)
• Resins in laboratory products are disposed of

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Reverse osmosis Ion Exchange
Ion Exchange
RO Membrane
Product
RO Product
Feed
Ions Particles Organics Micro-organisms Gases
Ions lt5 Low MW Organics Gases
Ions lt0.0001 Low MW Organics N2, O2
Reject Ions gt95 Organics
Particles Micro-organisms
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Softening
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IX cation exchange

• Softening
• Cation resin in sodium form. Sodium ions
  exchanged for calcium and magnesium ions.
  Regeneration using sodium chloride (NaCl).
• De-alkalisation
• Removes the calcium and magnesium associated with
  the alkalinity (bicarbonate) content

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Magnesium, Calcium, Other Cations are Exchanged
for Sodium in a Water Softener
Feed
Na
Fe
Mg
Ca
Na
Na
Na
Na
Na
Na
Na
Softening Resin
Na
Na
Na
Ca
Na
Na
Na
Na
Na
Mg
Na
Fe
Gravel Bed
Na
Na
Na
Na
Na
Na
Na
Softened Water
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Release of Organics and Silica from Resin Pack on
Exhaustion
19 18 17 16 15
25 20 15 10 5 0
Resistivity (Mohm-cm)
Concentration (ppb)
Resistivity
TOC
Silica
0
500
1000
1500
Volume (litres)
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Photo Sterilization
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UV photo-oxidation

• High intensity ultraviolet radiation
• 254 nm kills bacteria by degrading DNA
• 185 nm reduces level of organics by breaking
  molecular bonds and splitting water to produce
  highly reactive hydroxyl radicals

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Typical Laboratory system
Primary treatment
Reservoir
Polisher
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Basic components

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Common Measurement Units
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Conductivity

• Electrical conductivity of a solution depends on
  the number and types of ions present.
• Voltage applied across 2 electrodes in water
• Ions transmit electric current
• Greater the no. of ions the greater the current
• Temperature dependent
• Temp ?, conductivity ?
• Units (?S/cm)
• Values reported at 25C

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Conductivity - continue

• The electrical conductivity of a solution is a
  very good indication of ionic water purity.
• At a conductivity of gt 0.06 uS/cm it is no longer
  an accurate guide to trace ion levels.
• User has to rely on system design or monitoring
  of individual ions

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Conductivity andtemperature in Ultra Pure Water
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Resistivity

• Resistivity 1/conductivity
• Temperature dependent
• temp ? resistivity ?
• Units M?.cm, values reported at 25C
• If resistivity ? 0.5 M?.cm (2.0 uS/cm)
  measurement must be made on-line
• Ultra-pure water 18.2 M?.cm _at_ 25C

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Total Dissolve solids

• Weight remaining after evaporating water at 180oC
  
• Calculated as 0.7 x conductivity in µS/cm
• mainly inorganic and some organics
• only useful for feed water (mains etc)
• units ppm (mg/l)

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pH measurement of ultra pure water

• Very complex measurement
• No impurities to buffer against rapid pH changes
• US Pharmacopoeia specifies addition of 0.3ml of
  saturated potassium chloride solution to a 100ml
  sample prior to pH measurement on purified water.

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Water Storage
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Water storage

• Storage of purified water, that is not
  recirculated, should be kept to an absolute
  minimum
• Regular sanitization - to prevent build-up of
  bio-film.
• To prevent algal growth, avoid using translucent
  tanks and pipe work

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Effect of recirculation CVF on Reservoir
Resistivity
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Bacteria in Pure Water
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Water quality
ELGA meets ALL LabWater quality needs ...
Type I ULTRA-PURE WATER
Bio-Science Band
Type II PURIFIED WATER (General Lab Grade)
Type III Primary Grade Water
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Purified Water Standards
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Water quality standards

• British Standards Institute (BSI)
• American Society for Testing and Materials (ASTM)
• International Organisation for Standardisation
  (ISO)
• National Committee for Clinical Laboratory
  Standards (NCCLS)
• US Pharmacopoeia (USP)
• British and European Pharmacopoeia
• (BP EP)

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Purified Water Standards

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Purified Water Standards

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Standards Suitability for Applications

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Some Common uses of water in the Laboratory

• Blanks
• Standards
• Eluants
• Reagents
• Diluants
• Sample Preparation

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Common areas where water can have an effect upon
results

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Fitting it all Together

• Choosing, sizing and selling a system

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Selecting the right system

• Asking the right questions
• 1) What is the water needed for ? Be specific!
• 2) What quality of water (spec) do you need ?
• 3) What is your feed water quality?
• 4) Any specific impurities found in your feed
  water that may affect your application/s?
• 5) How much water do you need?
• a) per 8 hour day / shift / 24 hour day ?
• b) in one dispense? (think washing machines etc)
• 6) Where is the water system to be installed?

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Summary

• Waters impurities can have far reaching effects
  in your lab
• Reliance upon International Standards does not
  guarantee good results
• Its important to choose the right quality for
  your application

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Thank you for your attentionnatashak_at_labotec.co.
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