Water-Chemistry.pdf

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Basic Chemistry for WaterBasic Chemistry for WaterPlant OperatorsPlant Operators



MatterMatter SolidsSolids

LiquidsLiquids

GassesGasses



Pure ElementsPure Elements

Elements are matter built up from subatomic particlesElements are matter built up from subatomic particles

Properties are determined by their nucleus ( protonsProperties are determined by their nucleus ( protons

and neutrons) and by their electron shells.and neutrons) and by their electron shells.

All of the atoms of an element have the same All of the atoms of an element have the samenumber of protons in their nuclei.number of protons in their nuclei.

Elements do not break down into simpler elements.Elements do not break down into simpler elements.

There are over 118 known elements.There are over 118 known elements. 92 occur naturally, and others have been produced in92 occur naturally, and others have been produced in

the laboratorythe laboratory



Periodic Table of the ElementsPeriodic Table of the Elements



Electrons in Outer ShellElectrons in Outer Shell



The Periodic ChartThe Periodic Chart

Use of Atomic WeightUse of Atomic Weight

3

OOxygen

15.99

Atomic Number

Symbol

Name

Atomic Weight



Calculating Molecular WeightCalculating Molecular Weight

of a Compoundof a Compound

The Molecular Weight of a Compound is theThe Molecular Weight of a Compound is thesum of the Atomic Weights in the Chemicalsum of the Atomic Weights in the ChemicalFormula. For example for HFormula. For example for H22OO

Hydrogen Atomic Weight = 1Hydrogen Atomic Weight = 1

Oxygen Atomic Weight = 16Oxygen Atomic Weight = 16

There are 2 Hydrogen Atoms so theThere are 2 Hydrogen Atoms so themolecular weight of Hmolecular weight of H22O is 2 + 16 = 18O is 2 + 16 = 18



Element Symbol Element Symbol Element Symbol

Aluminum Al Chromium Cr Oxygen O

Arsenic* As Fluorine† F Phosphorus P

Barium* Ba Hydrogen H Potassium K

Boron B Iodine I Radium* Ra

Bromine Br Iron Fe Selenium* Se

Cadmium* Cd Lead* Pb Silicon Si

Calcium Ca Magnesium Mg Silver* Ag

Carbon C Manganese Mn Sodium Na

Chlorine Cl Mercury* Hg Strontium* Sr

Copper Cu Nitrogen N Sulfur S

Common Elements of Water Treatment



Equivalent WeightEquivalent Weight

The equivalent weight of an element isThe equivalent weight of an element isthat weight which will combine with orthat weight which will combine with ordisplace 8 grams of oxygen or thedisplace 8 grams of oxygen or the

equivalent weight of another element.equivalent weight of another element.

Atomic weight = Equiv. Weight X Valance Atomic weight = Equiv. Weight X Valance

Many elements have more than one valance.Many elements have more than one valance.



Mole Equivalency in WaterMole Equivalency in Water

TreatmentTreatment

A mole is the weight in grams of the A mole is the weight in grams of themolecular weight of a substance.molecular weight of a substance.

One mole of HOne mole of H22O is equal to 18 grams.O is equal to 18 grams.

A mole is a measure that defines how the A mole is a measure that defines how theelements in a substance will combineelements in a substance will combine

In the above equation 2 grams of hydrogenIn the above equation 2 grams of hydrogen

will combined with 16 grams of oxygen or 1will combined with 16 grams of oxygen or 1gram of hydrogen will combine with 8 gramsgram of hydrogen will combine with 8 gramsof oxygen.of oxygen.



Molar andMolar and MolalMolal Solutions inSolutions in

Water ChemistryWater Chemistry

Molar andMolar and MolalMolal solutions are used tosolutions are used todetermine the concentrations of knowndetermine the concentrations of known

compounds in the water.compounds in the water.

A molar solution consists of 1 gram molecular A molar solution consists of 1 gram molecularweight dissolved in enough water to make 1weight dissolved in enough water to make 1

liter.liter.

A A molalmolal solution consists of 1 gram molecularsolution consists of 1 gram molecular

weight dissolved in 1 liter of water.weight dissolved in 1 liter of water.



Solutions and StandardsSolutions and Standards

Aqueous AqueousSolutionSolution Mixture completely dissolved in waterMixture completely dissolved in water

StandardStandard

SolutionSolution

A solution in which the exact A solution in which the exact

concentration (molecular weight isconcentration (molecular weight isknown)known)

StandardizeStandardize Determining the exact strength ofDetermining the exact strength of

solution by comparison with standardsolution by comparison with standard

of known strengthof known strength

TitrationTitration Process of adding chemical of knownProcess of adding chemical of known

strength to determine concentrationstrength to determine concentration

of unknown compoundsof unknown compounds



Acids and Bases Acids and Bases

Hydrogen Ions (moles/liter)Hydrogen Ions (moles/liter)pHpH CompoundCompound Hydrogen IonsHydrogen Ions00 Hydrochloric AcidHydrochloric Acid 101000

11 Stomach AcidStomach Acid 1010--11

22 Lemon JuiceLemon Juice 1010--22

33 Vinegar Vinegar 1010--33

44 Root BeerRoot Beer 1010--44

55 RainwaterRainwater 1010--55

77 Pure WaterPure Water 1010--77

99 Baking SodaBaking Soda 1010--99

1010 Ammonia Ammonia 1010--1010

1212 Drain CleanerDrain Cleaner 1010--1212

1313

Sodium HydroxideSodium Hydroxide

1010--1313



Ions in Water TreatmentIons in Water Treatment All acids, bases and salts disassociate or ionize in water. Thes All acids, bases and salts disassociate or ionize in water. Thesee

are known as electrolytes.are known as electrolytes.

Electrolytes normally have the same number of protons asElectrolytes normally have the same number of protons as

electrons that neutralize one another. When dissolved in waterelectrons that neutralize one another. When dissolved in water

they split into their respective elements or compounds and losethey split into their respective elements or compounds and lose

or gain electrons. This results in the elements or compoundsor gain electrons. This results in the elements or compounds

becoming positively or negatively charged.becoming positively or negatively charged.

Sodium and Calcium give up electrons and become positivelySodium and Calcium give up electrons and become positively

charged. Positively charged ions are calledcharged. Positively charged ions are called “ “cations.cations.” ” Chlorine is negatively charged because it gains electrons.Chlorine is negatively charged because it gains electrons.

Negatively charged ions are calledNegatively charged ions are called “ “anions.anions.” ”



Important Ions in WaterImportant Ions in Water

Chemistry and Common ValencesChemistry and Common Valences

CationsCations

H+H+

Na+Na+

Ca++Ca++ Mg++Mg++

MnMn++ or +++++ or +++

FeFe ++ or +++++ or +++ S ++S ++

NHNH44++

Anions Anions

ClCl – –

OO -- --

OHOH – – HCOHCO33 – –

COCO33 ----

NONO33 -- SOSO44 – –

OClOCl --



Use of Aluminum and Iron SaltsUse of Aluminum and Iron Salts

in Coagulationin Coagulation

COMMON COAGULANT CHEMICALS

Aluminum

Sulfate

Al2(SO4)3

Ferric Sulfate Fe 2 (SO4)3

Ferrous Sulfate FeSO4

Ferric Chloride FeCl 3

Sodium Aluminate NaAlO 3



Oxidation Reduction ReactionsOxidation Reduction Reactions

Oxidation or Reduction is a method of forcingOxidation or Reduction is a method of forcing

reactions to completion by the reaction of anreactions to completion by the reaction of an

ion with an oxidant or reducing agent.ion with an oxidant or reducing agent.

For example, the Cyanide (CN) ion can beFor example, the Cyanide (CN) ion can beoxidized with Chlorine to produce Nitrogenoxidized with Chlorine to produce Nitrogen

gas and Carbon Dioxide.gas and Carbon Dioxide.

Oxidation/reduction reactions will proceed toOxidation/reduction reactions will proceed tocompletion.completion.



Oxidation in Water TreatmentOxidation in Water Treatment

Oxidize Inorganic Elements such as Iron andOxidize Inorganic Elements such as Iron and

ManganeseManganese

Destruction of Taste and Odor CompoundsDestruction of Taste and Odor Compounds

Destruction of Synthetic Organic ChemicalsDestruction of Synthetic Organic Chemicals Assist in the Coagulation Process by Assist in the Coagulation Process by

Destabilization of ParticlesDestabilization of Particles

Control of Biological GrowthControl of Biological Growth



Oxidants Used in WaterOxidants Used in Water

TreatmentTreatment

OzoneOzone

PermanganatePermanganate

Chlorine DioxideChlorine Dioxide

ChlorineChlorineOxygenOxygen



Inorganic and OrganicInorganic and Organic

ChemistryChemistry The study of compounds containing carbonThe study of compounds containing carbon

The most basic compounds are hydrocarbonsThe most basic compounds are hydrocarbonsmade up of only carbon and hydrogenmade up of only carbon and hydrogen

Carbon can bond with each other formingCarbon can bond with each other forminglong chainslong chains

Major types include alcohols, polymers andMajor types include alcohols, polymers and

ketonesketones Chlorinated hydrocarbons are of particularChlorinated hydrocarbons are of particular

interest in water treatmentinterest in water treatment



Organic MeasurementOrganic Measurement

TOCTOC Total Organic CarbonTotal Organic Carbon

NOMNOM Natural Organic MaterialNatural Organic Material

SUVA SUVA SpecificSpecific UltraviolateUltraviolate

Absorbance Absorbance

PrecursorPrecursor Proportional to the TOCProportional to the TOCConcentrationConcentration

Humic SubstancesHumic Substances Products of NaturalProducts of Natural Vegetative Decay (Color) Vegetative Decay (Color)



Alkalinity/Acidity Alkalinity/Acidity Alkali Alkali Soluble Salts that neutralize AcidsSoluble Salts that neutralize Acids

Alkaline Alkaline Sufficient amount of alkali to raise pHSufficient amount of alkali to raise pH

above 7above 7

Alkalinity Alkalinity Capacity of Water to neutralize acidsCapacity of Water to neutralize acids

Does not exist below pH 4.5Does not exist below pH 4.5

Acidic Acidic Condition of Water to lower pH below 7Condition of Water to lower pH below 7

Acidified Acidified Addition of Acid to below pH 2 Addition of Acid to below pH 2



Water HardnessWater Hardness

Total HardnessTotal Hardness Carbonate and NonCarbonate and Non--CarbonateCarbonate

CarbonateCarbonate Bicarbonate, Carbonate andBicarbonate, Carbonate and

HydroxideHydroxide

NonNon--CarbonateCarbonate Sulfides and ChloridesSulfides and Chlorides

PermanentPermanentHardnessHardness

NonNon--Carbonate HardnessCarbonate Hardness

NaturalNaturalHardnessHardness Bicarbonate AlkalinityBicarbonate Alkalinity



Solids and Colloidal MaterialSolids and Colloidal Material

SuspendedSuspendedSolidsSolids Suspended in the Water and can beSuspended in the Water and can beRemoved by Conventional FiltrationRemoved by Conventional Filtration

ColloidsColloids Finely Charged Particles that do notFinely Charged Particles that do not

DissolvedDissolvedTurbidityTurbidity The Cloudy Appearance of WaterThe Cloudy Appearance of Water

caused by Suspended Matter andcaused by Suspended Matter and

ColloidsColloidsZeta PotentialZeta Potential Electrical Charge of a suspendedElectrical Charge of a suspended

particleparticle

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