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2014 Training Seminars

WATER CHEMISTRY

Colin Frayne CWT

AQUASSURANCE, INC.

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Why is Water used as a Process Fluid?

• Liquid water and gaseous steam forms of H2O are commonly employed as heat-transfer vehicles for the transport of heat to some distant point of use, or for the uptake/ removal/ rejection of heat . Also, for use in a wide variety of industrial processes.

• Water has a high heat capacity • It’s a good solvent and medium for chemical reactions

Apart from boilers and cooling systems, we use water for: • Washing , Cleaning ,Rinsing, Dying, Melting, Quenching,

Stripping, Scrubbing, Cooking, Hydrolyzing reactions • We can obtain water for reuse from:

Distillers, Evaporators, Condensates, Boiler Blowdown, Softener/Filter Rinsing, RO-Reject, Neutralization, Electronics, Formation/Produced Water, Refinery Sour Waters, Mining, Treated Wastewater, Rainwater

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Heat Capacity of Water is measured in Btu’s (unless we go Metric/SI!)

• What is a Btu?

• Provide a definition?

• How many Btu’s required to raise 1lb. of water from 32oF to 212oF at sea level?

• What is the heat content of 1 lb. of steam at sea level (from and at 212oF)?

• What is the air pressure at sea level?

For Metric/SI: 1 Btu/lb = 4.177 kJ/kg, or 0.516 calories/gram

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Heat Capacity of Water

• Btu is a British Thermal Unit

• It is amount of energy required to raise temperature of 1 lb water by 1oF

• 212-32 = 180 Btu

• Enthalpy of evaporation (latent heat of vaporization) = 970 Btu/lb. So, heat content = 180 + 970 = 1150 Btu

• Atmospheric pressure = 14.7 psiatm (Approx 1 Bar)

• Absolute pressure (psia) = psiatm + psig

• 1 Btu/lb = 4.177kJ/kg

• 970 Btu/lb = 2257 kJ/kg

• Latent Heat of Vaporization of water = 1150 Btu/lb (2260 kJ/kg, 593cal/g) @ 100oC

• Latent Heat of Fusion of water = 144 Btu/lb (334 kJ/kg, 79.7cal/g) @ 0oC

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Why is Water Treatment vital?

Effects of poor water treatment!

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Because Water is a “universal solvent”!

• Natural impurities and introduced contaminants can promote many types of problems in water systems

Effects are:

• Hinders heat-transfer and steam gen. processes

• Adversely affects quality and purity of steam

• Primary instigator in metals corrosion/wastage.

• Deposits crystalline/non-crystal scales/sludges

• Produces foulants, and encourages biofoulants

• Promote hygiene and infection hazards

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So, understanding basic chemistry is critcally important in water treatment!

Dissolved minerals + concentration effects + local operating conditions & stresses = risks of water-side problems

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Matter – Anything with space/weight (mass) -solids, liquids gases.

Elements – 92 naturally occurring types of matter, perhaps 117 in total. They consist of: protons and neutrons in a nucleus, plus electrons surrounding nucleus in elliptical, circular and spherical orbits. (Plus other sub-atomic particles)

Chemistry Basics: 1

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Allotropes – Some elements exist in different atomic geometric arrangements, e.g. Carbon exists as diamond, graphite and amorphous carbon (charcoal) - which confers

different properties.

We now know that carbon also exists as graphene – sheets of single atom thickness carbon and the basis of nanotubes and fullerenes (used in nano-technology)

Chemistry Basics: 2

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Chemistry Basics: 3

Atom – Smallest unit of element capable of chemical combination. Example = elemental nitrogen N, elemental hydrogen H

Proton “+” charged, sub-atomic particulate(s) found in

atomic core. Atomic Weight = 1 Neutron Non-charged, sub-atomic particulate(s) found in

atomic core. Atomic Weight = 1 Electron “-”charged particulate(s), surrounding atomic

core. Atomic Weight = 0 Q: What is the real mass of an electron? (mass = weight at constant

gravity) A: 9.1093821545 × 10-31 kilograms (Kg)

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Chemistry Basics: 4

Electrons surround atomic nucleus in discrete, 3- dimensional, quantum energy “shells”, filling inner “shells” first, (holding 2, 2+6, 2+6+10, 2+6+10+14, 2+6+10, etc. electrons).

Isotope – Two or more atoms of element with same At. No. and properties, but different At.Wt’s, due to increased number of neutrons. Isotopes decay over time, down to a stable energy level. (e.g. 14C 12C). Some isotopes exhibit radioactive decay! (e.g. U232/U238) Almost every element has multiple isotopes.

NUCLEAR FUEL PLANT TO EXTRACT DEUTERIUM

ISOTOPE FROM WATER

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Molecule – The smallest unit of chemical substance retaining all chemical identity. e.g. molecular nitrogen N2 hydrogen H2 and ammonia NH3.

- Many elemental atoms unite, forming molecules for more stability (i.e to produce lower energy levels) e.g. O2 gas

- They combine (bond) with other elements in different ways and via different types of bonds

- Some elements are sufficiently stable to exist as single atoms (e.g. gold, platinum) Periodic Table – Each element is unique and is placed in a table reflecting common properties

Chemistry Basics: 5

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Periodic Table of Elements

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Chemistry Basics: 6

Radical – Group of elements with unsatisfied “valance” [space for electron(s) in outermost energy-level shell]. Acts as single element in reaction. e.g. ammonium radical: (NH4)+

Valency – The number of bonds formed by an atom of a given element. i.e. “combining power” of an atom.

Example: O atom (with a valency of 2 – or a space to accept two electrons) combines with 2 x H’s (each with a valency of 1) ,to form water - H2O

Ion – Atom or molecule that has either gained or lost an electron. Salt (NaCl) consists of two ionic atoms = Na+Cl-

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Chemistry Basics: 7

Some types of molecular bonds

• Ionic bond- combination of electronegative and electropositive attraction. Salts forms ionic bond

• Metallic bond - lattices/crystals in metals

• Covalent bond – sharing of electron pairs by atoms

• Coordinate bonds – bonding of metals by a chelant, forming a complex

• Hydrogen bonding – electrostatic attraction of atoms gto those in different molecules , linking the molecules together by the attractive force

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• How many protons, neutrons and electrons in each atom?

Water Molecule: H20 molecular wt = 18, Dipolar

Hydrogen atom Oxygen Atom Hydrogen atom

= Electron = Proton = Neutron = Hydrogen bond attractions

The atoms in a water molecule are covalently bonded.

Note: This model reflects a simplified version of a combination of Bohr & Schrodinger quantum physics theories, where shells represent discrete quantum energy levels, and

changes in energy result in photonic electromagnetic radiation

HYDROGEN BOND – ACTUAL PICTURE!

Atomic force microscopy (AFM) picture of (antiseptic) 8-hydroxyquinoline molecules (C9H7NO), showing hydrogen bonding, whereby electropositive hydrogen atoms form a bridge between two electronegative species X and Y, (i.e. X-H-Y). Color code: Green = C, Blue = N, Red = Oxygen, White = Hydrogen)

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Why is valency and bonding important?

–Because molecular physics defines the structure and properties of chemicals, and the physical world

The result is reflected in:

• High heat capacity of water - hydrogen bonding

• Leakage of sodium cations through a demineralizer

• Difficult to remove non-reactive silica from water

• Corrosive nature of chloride and sulfate anions

• Different forms and colors of iron oxide rusting

• Hardness of diamond and softness of graphite

• The loss of carbon dioxide from bicarbonate, and resulting scale

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Compounds –2 or more elements bonded by reaction, forming new product. Not easily reversed. Examples: Salt - NaCl (sodium, Na and chlorine, Cl) Sulfuric acid - H2SO4 (hydrogen, H; sulfur, S; oxygen, O) Mixtures – 2 or more elements, compounds, or both, brought together in any combination, without bonding or chemical reaction. Capable of separation. Examples: Air -(O2, N2, CO2, H2O, SO2, inert gases) Chemical treatment - (caustic, polymers, phosphonates, tolyltriazole, molybdate)

Chemical Basics 8: Compounds/Mixtures:

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Chemical Basics 9: Acids, Bases and Salts

Acids/Bases/Salts – Early chemistry denoted acids as sour. Also, soda or potash bases (soluble alkalis) reacted with acids to form salts.

Acids – Substances releasing hydrogen ions (H+) in water. (hydrogen that has lost an electron)

• Sulfuric: a strong acid, dissociates to 2H+ and SO42-

• Carbonic: weak acid, limited dissociation, 2H+ and CO32-

Bases – (Alkali) Substance dissociating in water, producing hydroxyl ions (OH-)

• Sodium hydroxide: (NaOH), a strong base. Readily dissociates, producing Na+ and OH-.

• Ammonium hydroxide: weak base. Forms some NH4+OH-

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Acid + Base = Salt + Water HCl + KOH KCl + H2O Hydrochloric potassium potassium water acid hydroxide chloride

Chemistry Basics: 10 - Salts

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Chemistry Basics 11: Inorganic/Organic

Inorganic chemistry – non-organic (i.e. non-living) e.g. caustic soda, sulfuric acid Organic chemistry –originally, chemistry of living organisms – Carbon chemistry!, e.g. polymers. Carbon chemistry - forms long chain compounds with single/double/triple bonds (Aliphatic chemistry) - e.g. propane, gasoline, kerosene Also, sharing of unpaired electrons provides for resonating ring-structures, and (Aromatic chemistry) e.g. Benzene, Toluene, Xylene (BTX) Silica also has wide range of chemistries like carbon!

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Water Chemistry:

Water is a “universal solvent”, formula H2O. MW 18.

Hydrogen bonding causes molecular attraction, high latent heat, surface tension.

Ionization potential water only slightly ionizes, which makes it a poor conductor. Dissolves ionic solids – leading to increase in TDS.

pH: A logarithmic scale (from 0 to 14) of acidity (H+ concentration) of water. Each unit change indicates a factor of 10x concentration!

• 7.0 0 indicates increasing acidity • 7.0 14 indicates increasing alkalinity

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Water Chemistry: pH

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Water Chemistry: Alkalinity

The Sum of carbonate, bicarbonate, hydroxyl ions. But phosphate, silicate etc. also contribute. Analyses given in ppm (mg/l) CaCO3

Phenolphthalein Alkalinity: (P. Alk) portion of alkalinity titrated with acid to pH 8.2 end-point

Total Alkalinity or M. Alkalinity: portion of alkalinity titrated with methyl orange to pH 4.2

Interpretation of “P” & “M” alkalinity titrations:

• Bicarbonates + hydroxides do not exist together • CO2 does not exist with carbonates • “P” Alkalinity = ½ carbonates and all hydroxides • “M”Alkalinity = all hydroxides, carbonates and bicarbonates

Ions P = 0 P < M/2 P = M/2 P > M/2 P = M

(OH) 0 0 0 2P - M M

CO3 0 2P M 2(M - P) 0

HCO3 M M - 2P 0 0 0

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Water Chemistry: Hardness

Alkaline earth salts in water provides “hardness”, interferes with cleaning. Need more soap! Causes scaling/ sludge deposits. Permits under-deposit corrosion to develop.

Total hardness = sum of Ca and Mg hardness

Note: Calcium carbonate: solubility is 14 mg per liter (14ppm) @ 60oF in CO2 free w

Temporary hardness or carbonate hardness: can be removed by heating water to precipitate as carbonate salt (e.g. bicarbonates), equal to or less than the P. alkalinity.

Permanent hardness or non-carbonate hardness is that portion of total hardness that cannot be removed by heating water (e.g. sulfate hardness), and is the difference between total hardness and total alkalinity.

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CO2 + H2O H2CO3 carbon dioxide water carbonic acid H2CO3 + CaCO3 Ca(HCO3)2 carbonic calcium calcium acid carbonate bicarbonate Ca(HCO3)2 CaCO3 + CO2 + H2O calcium HEAT scale carbon water bicarbonate dioxide

Water Chemistry Scaling:

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Water Chemistry: Corrosion:

• An oxidation process, to a lower energy state!

Note: Oxidation is the addition of oxygen, removal of hydrogen, or loss of electrons

• The wastage, loss of utility, or destruction of a metal by an electrochemical, or electro-biochemical reaction

• Corrosion occurs whenever water, oxygen, and metal are present together. Also, when a corrosive chemical is present (e.g. excess chlorination of water, sulfates from bacteria)

CORROSION REACTIONS

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Water Chemistry: Water Analysis Units: 1

Mass Quantity of matter, equal to weight at constant gravity

Atomic weight Weight of elemental atom relative to 16O or 12C. Example: H =1, He =4, Li =7 atomic weight/Daltons

Molecular weight Average weight of molecule (in atomic units/Daltons). Example: MW of H2 = 2, MW of NH3 = 17

Mole Molecular weight of element/compound, expressed in grams Example: NaCl = 23 +35.5 = 58.5g

Molar solution One mole of solute dissolved in liter water (M/1, or M, or 1M) Example: M/1 CaCO3 = 100g/L

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Water Chemistry: - Molarity/pH Relationship

In dilute solutions (e.g. tap water) H+ activity is approx. equal to the numeric value of the conc. of the H+ ion, denoted as [H+] ([H3O+]), moles per liter (molarity).

• Therefore, it is convenient to define pH as: pH −log10 [H+]/1 mole per L

• For example, if we make lemonade with a H+ conc. of 0·0050 moles per liter, its pH would be:

pH −log10 (0.0050) = 2.3

A solution of Milk of Magnesia (pH = 8·2) will have an [H+] conc. of 10−8·2 mole/L, or about 6·31 × 10−9 mole/L. Thus, its hydrogen activity (αH

+) is around 6·31 × 10−9

pH = log10 1 or: pH = −log10[H+] or: pH = −log10 α[H+] [H+] 1mole/L

• Do you remember a Mole? i.e. Molecular weight of element/ compound, expressed in grams Example: NaCl = 23 +35.5 = 58.5g

• Do you remember Valency ?– The number of bonds formed by an atom of a given element. i.e. “combining power” of an atom.

• Now look at the molecular weight (MW) divided by the valence. This is an Equivalent weight.

• Equivalents refers to the equivalent weight (EW) of the substance expressed in grams (or Meq in milligrams [mg]). E.g. Calcium (Ca), molecular weight = 40. It’s divalent (2), so EW is 20 (40/2 = 20).

• (Equivalent weight/gram equivalent Mass of substance that will supply/react with one mole of hydrogen cation [H+] in acid-base reaction.) Example CaCO3: MW =100, EW = 50

• Normal solution One gram equivalent wt. dissolved in 1 liter water (N/1). Example: N/1 CaCO3 = 50g/L

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Water Chemistry: Water Analysis Units: 2

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Milliequivalent or gram milliequivalent (Meq) 1/1000 of a gram equivalent

Milliequivalent per liter: (Meq/L),. Same as N/1000. 1Meq/L of CaCO3 = 50 mg/l or 50 ppm.

Milligram per liter: (mg/L), equal to g/m3. Also equal to part per million (ppm), on a wt/wt basis for solns. with an S.G. = 1.00.

Grain: 1/7000 of lb. Grain/US gallon = 17.1 mg/L

For CaCO3: (MW =100):100 mg/l = 100 g/m3 = 100 ppm = 2Meq/L = 5.848 grains/ US gallon (gpg)= N/500 = 0.84 lb. per 1000 US gall

Ion Exchange resins: 1 eq/L or 1 Meq/mL = 21.87 Kgr/ ft3. 1.0 grains per gallon = 17.1 ppm of substance expressed as calcium carbonate.

Water Chemistry: Water Analysis Units: 3

• The capacity of an ion exchange resin is expressed as quantity of ions that can be taken up by a specific resin volume (i.e. quantity-per-unit volume). E.g. kilograins per cu ft (Kgr/ft3), or milli-equivalents per milliliter (Meq/mL) - which also equals equivalents per liter (eq/L).

• Remember that Calcium (Ca) has a mol. wt of 40 and is divalent (2), so Equiv. Wt (EW) is 20 (i.e. 40/2 = 20)

• Thus, in theory, an ion exchanger with a capacity of 1.95 eq/L (or Meq/mL) would therefore have a capacity to remove 1.95 x 20 = 39 grams of calcium per liter of resin, or 1.1 kilograms (k) or 2.43 lbs. of calcium/ft3.

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Water Chemistry: Water Analysis Units: 4

Water softener example!

• A typical strong acid cation exchanger will have a total capacity of 1.95 meq/ml or 42.7 Kgr/cu.ft. of resin.

• To get an idea of how this capacity equates to ions, one equivalent of sodium is equal to Avogadro’s Number (6.02 x 1023 ions). Thus, a liter of resin would therefore have 1.17 x 1024 (6.02 x 1023 x 1.95) reactive sites per liter of resin or 3.32 x 1025 sites per cubic foot.

• A single exchange bead would thus contain some 1.7 x 1017 reactive sites (that’s 170,000,000,000,000,000 or one hundred seventy quadrillion reactive sites).

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Examples of Minerals Found In Water

calcium bicarbonate: Ca(HCO3)2 calcium chloride: CaCl2 calcium sulfate: CaSO4 calcium carbonate CaCO3 magnesium bicarbonate: Mg(HCO3)2 magnesium chloride: MgCl2 magnesium sulfate: MgSO4 sodium bicarbonate: NaHCO3 sodium chloride: NaCl sodium phosphate: Na3PO4 sodium sulfate: Na2SO4 ferrous bicarbonate: Fe(HCO3)2 manganous bicarbonate: Mn(HCO3)2 silica: SiO2 silicic acid: H2SiO3 sodium silicate: Na2SiO3

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Problems Associated With Crystalline/ Non-crystalline Scale Deposits

• Reduction In Heat Transfer Capacity • Blockages (Fouling) In Pipes And Fittings • Under Deposit Corrosion • Microbiological Fouling • Interferes With Inhibitor Filming • A cost, due to need for cleaning, loss of efficiency, and

possible loss of capital asset

ALL THESE PROBLEMS GO BACK TO A

HIGHER FUEL COSTS, LOSS OF PRODUCTION, MORE MAINTENANCE, ETC.

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ORP (REDOX) Chemistry :

• Oxidation: Addition of oxygen, removal of hydrogen, or loss of electrons

• Reduction: The removal of oxygen, addition of hydrogen, or gain of electrons

• ORP sensor measures the ability of a solution to act as an oxidizing agent or reducing agent. ORP stands for oxidation-reduction potential.

• ORP meter measures redox potential in the range of -450 to +1100 mV. Readings in the positive region indicate a strong oxidizing agent, while readings toward negative region indicate a strong reducing agent. Resolution is 0.5 mV

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ORP Chlorine Chemistry:

• ORP does not tell you the chlorine conc. in ppm. It does indicate effectiveness of chlorine as an oxidizer. An ORP reading will vary as pH fluctuates. As the pH goes up, the millivolt reading on ORP meter will go down, indicating that the sanitizer is not as effective. Reducing pH or adding more sanitizer will raise mV reading.

• World Health Organization ORP standard for drinking water disinfection is 650 mV. States that when ORP in a body of water measures 650/1000 (2/3v) the sanitizer in the water is active enough to destroy harmful organisms almost instantaneously

WATER TREATMENT CHEMISTRY: Chemically, how can we do the following?

1. Remove high iron content from a well water source?

2. Soften the water without using an ion-exchanger

3. Remove high silica from aquifer water?

4. Control silica scaling in an RO, using high silica feed water?

5. Remove excess chlorine bleach before discharging waste water to sewer?

6. Remove phosphate from treated wastewater for cooling water make-up?

7. Remove ammonia from a cooling water, due to process leaks?

8. Remove Calcium, Magnesium, Barium, Strontium, Iron, and Manganese metals from produced water, for water reuse?

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FIRST: UNDERSTAND WATER TREATMENT OPTIONS USING SOLUBILITY RULES

1. All common salts of Group 1 elements and ammonium (NH4

1+) are soluble.

2. All common nitrates (NO31-) and acetates are

soluble.

3. Most chlorides, bromides, and iodides are soluble except silver, lead (II), and mercury (I)

4. All sulfates are soluble except barium, strontium, lead (II), calcium, silver, and mercury (I)

5. Except for those in Rule 1, carbonates, hydroxides, oxides, and phosphates are insoluble

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SOLUBILITIES

acetate bromide carbonate chloride chromate hydroxide iodide nitrate phosphate sulfate sulfide

aluminum Slightly

soluble

soluble not exist soluble not exist nearly

insol uble

soluble soluble nearly

insol uble

soluble decomp

ammonium soluble soluble soluble

soluble soluble soluble soluble soluble soluble soluble soluble

barium soluble soluble nearly insoluble

soluble nearly insoluble

soluble soluble soluble nearly insoluble

nearly insoluble

decomp

calcium soluble soluble nearly

insoluble

soluble soluble slightly soluble soluble nearly

insoluble

slightly

soluble

decomp

copper (II) soluble soluble nearly insoluble

soluble nearly insoluble

nearly insoluble

decomp soluble nearly insoluble

soluble nearly insoluble

iron (II) soluble soluble nearly

insoluble

soluble not exist nearly

insoluble

soluble soluble nearly

insoluble

soluble nearly

insoluble iron (III) soluble soluble not exist soluble nearly

insoluble

nearly

insoluble

not exist soluble nearly

insoluble

slightly

soluble

decomp

lead (II) souble slightly soluble

nearly insoluble

slightly soluble

nearly insoluble

nearly insoluble

slightly soluble

soluble nearly insoluble

nearly insoluble

nearly insoluble

magnesium soluble soluble nearly

insoluble

soluble soluble nearly

insoluble

soluble soluble nearly

insoluble

soluble decomp

mercury (I) slightly soluble

nearly insoluble

nearly insoluble

nearly insoluble

slightly soluble

not exist nearly insoluble

soluble nearly insoluble

slightly soluble

nearly insoluble

mercury(II) soluble slightly

soluble

nearly

insoluble

soluble Slightly

soluble

nearly

insoluble

nearly

insoluble

soluble nearly

insoluble

decomp nearly

insoluble potassium soluble soluble soluble soluble soluble soluble soluble soluble soluble soluble soluble

silver slightly

soluble

nearly

insoluble

nearly

insoluble

nearly

insoluble

Slightly

soluble

not exist nearly

insoluble

soluble nearly

insoluble

slightly

solube

nearly

insoluble sodium Soluble soluble soluble soluble soluble soluble soluble soluble soluble soluble soluble

zinc soluble soluble nearly insoluble

soluble soluble nearly insoluble

soluble soluble nearly insoluble

soluble nearly insoluble

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UNDERSTAND THE SOLUBILITY OF METALS AS A FUNCTION OF PH

We can remove Barium, Strontium, Calcium, Magnesium, Iron, Manganese, etc. from water by selective use of reaction/ solubility rules and the appropriate pH

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1. IRON REMOVAL FROM WELL WATER (Also Mn and H2S)

• Use an Iron Removal filter system (Greensand/BIRM/Filox, etc.)

1. Raise pH to >8.5

2. Typically, oxidize with NaOCl and precipitate the ferrous/ferric (Fe2+/Fe3+) oxides/hydroxides E.g.: 4 Fe + 3 O2 + 2 H2O → 4 FeO(OH)

3. Filter thru a greensand glauconite filter with a small continuous feed of potassium permanganate (n.b BIRM is not suitable for H2S)

It is also possible to remove multi-valent ions, such as Fe/Mn using an ion-exchange softener – but the ions exchange onto the resin beads and can only be removed by use of a chelating acid, such as HEDP.

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2. Softening water without using ion-exchange

• Use a cold or hot lime or lime/soda softener – and then filter

Ca(HCO3)2 + Ca(OH)2 = 2CaCO3 + 2H2O calcium calcium calcium water bicarbonate hydroxide carbonate

Mg(HCO3)2 + 2Ca(OH)2 = Mg(OH)2 + 2CaCO3 + 2H2O magnesium calcium magnesium calcium water bicarbonate hydroxide hydroxide carbonate

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3.Remove high silica from aquifer water?

• Use a cold or hot lime or lime/soda softener – and then filter • Remove the silica by adding magnesium chloride and precipitating

the silica as a colloid adsorbed onto the Mg(OH)2

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• We can remove Fe/Mn simultaneously in the same plant • Substitute caustic for lime to have a denser sludge

4. Control silica scaling in an RO, using high silica feed water?

• Raise the feedwater pH to >9.5-10.0 to prevent polymerization of the silica and resultant colloidal precipitate. Use a static mixer!

• Also going to need blend in a silica control polymer (such as 5000 MW AA/AMPS terpolymer, or 2000 MW polyether monoamine) into the antiscalent formulation (Using perhaps PMA/HEDP/PCA ).

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5. Remove excess chlorine before discharging waste water to sewer?

• Feed sodium bisulfite to neutralize the chlorine bleach NaHSO3 + NaOCl → NaCl + NaHSO4

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6. Removing phosphate from treated wastewater for cooling water make-up

• The best way is to remove the phosphate is at a POTW tertiary

treatment plant using Ferric or Al salts, otherwise we need to have our own small flocculation/clarification tank and filter.

• Keep a 0.3 mg/L PO4 – residual to provide anodic corrosion inhibition.

• Filter the precipitated phosphate salt using an anthracite“depth” filter, or similar - to make sure there is no carryover into the cooling water of (I micron colloidal) Fe/Al salts from the PO4 removal process

• Ensure phosphate dispersants are used in the cooling system

• Control COC, pH, Langelier, etc. to ensure no tricalcium phosphate or ferric phosphate scaling

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• Use breakpoint chlorination!

3 NaOCl + 2NH3 → 3NaCl + N2↑ + 3H2O

• But difficult to control with fluctuating incoming NH3 concentrations.

• Undesirable side-effect is the possible formation of chloroform (one of 126 regulated priority pollutants to POTWs)

• Also, the highly corrosive nature of the chlorinated water.

• Only useful if ammonia levels are <2 mg/L as NH3. Otherwise use a biological nitrification process , e.g. activated sludge – such as extended aeration or MBR with anoxic zone

• Another method is air stripping over the cooling tower at pH 10-5-11 (which prevents the ammonium ion forming – but calcium ppt. risks!)

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7. Removing ammonia from a cooling water, due to process leaks

Theoretical Breakpoint Chlorination Curve

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• Zone 1 is associated with the reactions of chlorine and ammonia to form monochloramine • Zone 2 is associated with an increase in dichloramine and the disappearance of NH3 • Zone 3 is associated with the appearance of free chlorine after the breakpoint

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8. Removing Ca, Mg, Ba, Sr, Fe, and Mn metals from produced water, for water reuse

• Use a sequential precipitation process (SPP)

• The process first removes barium from the wastewater as barium sulfate sludge via precipitation under controlled pH and ORP conditions.

• Following barium removal, the remaining scale formers; calcium, iron, magnesium, manganese, and strontium are precipitated as carbonates and hydroxides in two separate precipitation steps, using sodium carbonate and sodium hydroxide additions.

• After clarification, the pH of the finished water can be adjusted to meet recycle specifications by addition of carbon dioxide.

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A-Z Terms: QUIZ – What do you know?

• Amphoteric metal: • Brownian movement: • Colloid: • Dispersant: • Enthalpy: • Galvanic series: • Hematite:

• Ion:

• Jackson turbidity units:

• Kinetic energy:

• Latent heat of fusion of water:

• Molecular bridging:

NTA: Osmotic pressure: Passivation: QUAT: Reduction: Specific gravity: Tuberculation: Ultrasonic testing: Viscosity: WBA Resin: X-Rays: Ytterbium: Zeolite:

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A-Z Terms: 1

• Amphoteric metal: Metal such as zinc, that forms salts with potentially weak acidic or basic properties

• Brownian movement: Movement of colloidal suspended particles due to forces resulting from collision of colloids and molecules of suspended medium (usually water)

• Colloid: Very small particle, typically 10-5- 10-7 cm diameter

• Dispersant: Chemical agent having ability to lift, separate, and maintain in suspension a variety of mineral particles for a limited period

• Enthalpy: Total heat content of a body. Sum of sensible heat and latent heat

• Flocculant: Chemical agent that causes agglomeration of small, pin-head sized particles to larger flocs for purposes of settlement and water clarification

• Galvanic series: A list of metals and alloys arranged for the purposes of water treatment to show their relative potential for nobility or resistance to corrosion

• Hematite: A form of rust. Magnetic, gray-to-red colored iron oxide (Fe2O3) offering no protection from further

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A-Z Terms: 2

• Ion: An electrically charged atom, radical or molecule • Jackson turbidity units: A measure of turbidity of suspended

particles comparing optical obscurity against a series of standards

• Kinetic energy: The dynamic energy of a body or substance that comes from molecular motion

• Latent heat of fusion of water: 144 Btu/lb. at 32 oF • Molecular bridging: The joining of particles by polymers as part

of the process of flocculation. Usually higher MW polymers produce higher levels of molecular bridging

• NTA: Nitrilotriacetic acid or its sodium salts • Osmotic pressure: Pressure differential that exists between two

solutions separated by a semi-permeable membrane • Passivation: Conversion of a reactive metal surface into lower

energy state that does not readily further react or corrode • QUAT: Quaternary ammonium compound –alkyl

dibenzylammonium chloride (ADBAC) • Reduction: Removal of oxygen, addition of hydrogen or gain of

electrons

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A-Z Terms: 3

• Specific gravity: Ratio of density of a substance to that of water

• Tuberculation: Very visible form of corrosion in which voluminous layers form of brittle, iron oxide corrosion debris, usually covering a pit or deep crevice

• Ultrasonic testing: A form of non-destructive testing in which an ultrasonic beam is applied to sound-conducting materials in order to locate any discontinuities

• Viscosity: The property of a fluid that resists any force such as atmospheric or pump pressure, tending to produce flow

• WBA Resin: Weak base, anion exchange resin • X-Rays: A form of electromagnetic radiation with a wavelength

in the range of 10 to 0.01 nanometers • Ytterbium: The rare earth element with an atomic number of

70 and atomic weight of 173.04. The malleable Lathanide metal is a component of x-ray sources and a doper for optical systems.

• Zeolite: A natural ion-exchange material used for softening water and other purposes. Typically, minerals of hydrated aluminum or sodium silicates