Water Quality & Basic Chemistry

Water Quality

• Focuses on foreign substances present in water
• Focuses on effects of foreign substances on people and the environment
• To assess water quality, identify substances, their concentrations, and their effect on environmental health
• Standards are required to judge the suitability of water for specific uses
• Water dissolves substances easily, making it rarely found pure in nature
• Natural impurites exist in solution and suspension even in mountain streams
• Changes in water quality start with precipitation
• Rain picks up gases like oxygen and carbon dioxide, and dust
• Runoff collects silt, bacteria, minerals and organic material
• Groundwater has more dissolved minerals because it has more contact with soil and rock
• Human activities affect water quality: land use, municipal/industrial discharge

Chemistry Basics

• Water quality study needs chemistry knowledge
• Chemistry studies composition and properties of matter
• Elements form compounds through reactions
• Compounds are various basic element combinations
• Molecules are the smallest compound parts with same chemical properties

States of Matter

• Matter exists in four phases: solid, liquid, gas and plasma
• Solids: ordered atoms/molecules, stable shape, defined volume
• Liquids: less order, defined volume, variable shape and fluidity
• Gases: disordered atoms and molecules, no fixed shape or volume
• Plasma: gas-like clouds
• Plasma: mix of charged particles (ions/electrons)
• Plasma is universes most abundant matter, found mostly in stars

Chemical Formulas

• Molecules use atom symbols in combinations
• Chemical formula is the name for this combination
• Water has the chemical formula H₂O
• H₂O or "H-two-O" is water; subscript 2 means two hydrogen atoms in the molecule
• Iron oxide (rust) has the formula Fe3O4
• Fe3O4 three iron atoms and four oxygen atoms exist in one molecule

Organic and Inorganic Compounds

• Organic compounds are carbon molecules with hydrogen/oxygen
• Proteins, Carbohydrates, and Lipids are organic compounds
• Organic compounds are closely related to living organisms
• Inorganic compounds lack carbon in the structure
• Carbon monoxide and carbon dioxide are exceptions to the standard
• Inorganic compounds are part of the inanimate world
• These get used in water and wastewater treatment

Atomic Structure

• Atomic structure dictates how elements form complex compounds
• Atomic structure model includes dense center or nucleus
• Protons are in the nucleus and are positively charged
• Neutrons exist in the nucleus without electric charge
• Electrons with negative charge spin around nucleus in orbitals
• Neutral atoms have the same number of electrons and protons

Atomic Number and Weight

• Atomic number: number of protons in nucleus
• Each element has a unique atomic number
• Hydrogen's atomic number is 1, oxygen's is 8
• Atomic weight: total protons and neutrons in the nucleus
• Hydrogen's atomic weight is 1 (one proton, zero neutrons)
• Oxygens atomic weight is 16; 8 protons + 8 neutrons

Electron Behavior

• Elements' chemical behavior primarily depends on the number of electrons in an atom’s outer shell or orbital
• Innermost orbital is stable with two electrons max
• Next orbital is stable if it contains eight electrons max
• Larger atoms have additional orbitals for electrons

Molecule Formation

• Atoms form compounds by transferring or sharing electrons
• Ionic bonding involves full electron transfer
• Covalent bonding involves electron sharing to stabilize outer orbitals
• Sodium chloride (NaCl) forms when sodium (Na) transfers an electron to chlorine (Cl)
• Sodium's atomic number is 11, chlorine's is 17
• A sodium atom has one electron in its outermost orbit
• A chlorine atom contains seven electrons in its outermost orbit
• Atoms need eight orbiting electrons total
• Both atoms are unstable with the number they originally had
• When brought together, Na loses its outermost electron, becoming positive
• Na becomes +, Cl becomes - due to the negative charge attracted to it

Ionic Bonding

• NaCl forms as Na+ and Cl- ions attract; this is ionic bonding
• Ions are totally transferred in ionic bonds
• In water molecule or H₂O, hydrogen shares with the oxygen atom
• A hydrogen molecule has one proton, while oxygen has eight protons and eight neutrons
• No protons or electrons are gained or lost and the number of electrons is the same (10); thus, H₂O is neutral
• Oxygen and hydrogen form covalent bonds, but do not share equally
• There is complete transfer in ionic bonds
• Covalent bonds stabilize outer orbitals by sharing electrons

Solutions

• Solution: a uniform mixture with two or more substances in one phase (solid, liquid, gas)
• Solutions using water are aqueous solutions
• Carbon monoxide (CO) and more can form gaseous solutions when in the air
• Mixing manganese/carbon with iron is a solid solution called steel
• Solute is the largest amount substance, solvent the smaller
• Solutions show properties that differ from the properties of the solvent on its own
• NaCl's presence in water lowers the freezing point

Solubility

• Most solids are soluble in hot v. cold water
• Gas solubility decreases as tempetature of water increases
• Oxygen, carbon dioxide, and chlorine water solubility relates to environmental tech
• The concentration of oxygen in the water is measured as “mg⁄L” or milligrams per litre

Aqueous Solutions

• Aqueous sugar solutions retain the idenity of the sugar in the mixture
• Sugar molecules themselves do not change or break apart
• The uncharged sugar molecules are dispersed in the solution, surrounded by the water
• Saturated solution: sugar will no longer dissolve because of physical limitations

Ionization

• Some substances break apart, or dissociate, which forms elecrically charged ions
• The dissolving process that creates the ions and particles is ionization
• NaCl dissociates into Na+ and Cl- when dissolved

Suspensions and Colloids

• Some mixtures have substances suspended in fragments so large they go beyond the molecules
• Environmental tech considers properties between these mixtures and normal solutions

True Solutions

• Solute particles will never separate
• Physical separation from the solvent using filters wont work
• Suspended particals will settel out from the water due to gravity
• Particles can be removed from the water by using filters

Suspensions and Colloids Defined

• A coarse suspension are suspensions of relatively larger particles
• Large particles settle out, in still water, in just minutes
• Smaller Particles, take longer or hours to fully clear

Colloids

• Colloids: very fine particles, less than 0.1 μm in size
• Gravity or most filters cannot remove Colloids on their own
• Colloids have a size larger than true solutions and smaller than coarse
• repel each other, will not stick together to form anything heavier

Occurrence and Microscope

• Colloids are both in water and air
• clay particles are in water, smoke particles in air
• Microscopy cannot see solution particles

Tyndall Effect

• Collodial particles will scatter light, letting the beam be shown

Concentrations

• Concentrations are dependent on properties of the solutions, suspensions, and colloids mixtures
• Concentrations require quantitative expression rather than broad "dilute" or "strong"

Mass Per Unit Volume

• These are usually expessed with: mass per a single unit volume parts per million or billion, or in percent form
• mg/L is a common concentration term
• 10mg of oxygen in 1L of water has its concentration shown simply by writing 10 mg/L
• Problem
• If 0.3 g of salt is in 1500ml of water, whats the concentration?
• Start by coverting the following
• 0.3g = 300 mg
• 1g = 1000 mg; 1 L = 1000 mL So 1500 mL = 1.5L
• Answer: 300 mg/ 1.5 L = 200mg/L
• Parts Per Unit Volume
• Dilute solutions use microgranms per liter (micro g/L)
• Micrograms and Milligrams
• 1000 micro g equals 1 mg
• Move the decimal over to the right for convertion (multiply by 1000).
• Move decimal to the left for converstion for the other way
• Question
• 0.004 mg/L concentration is what in micrograms/L
• Convert
• 4 micrograms/L Particulate and gass concentrations floating in the air are micrograms per cubic meter (micro g/m3).

Parts Per Million, Billion or Trillion

• At Standard Temperatuer and Pressure
• One liter of water has 1 kg mass
• kg is about 1000 g or a million mg
• If i mg exists within liter of water, that is 1 mililion mg water
• Meaning there is one particle that exists, it equals one part per million, or 1 ppm
• All of this concentration = one part per million ( 1 ppm)
• One mg per litier is equivalent to onepart per million (1 mg/L = 1 ppm)
• Question
• If the concentration is 17.5 mg/liter in ppm?
• A concentration of 17.5 mglitre is 17.5 parts per million
• Million's expression is helpful; it conveys an image of just how small the concentations for the tecnologies are
• (1 PPM) - one port per million = 1in to 16 miles, or as one second into a max of 12 day period

Parts Per Billion

• Parts per billion can also show concentraions
• Parts per billion (PPB), or 1 ppb = 1 micrograms litre three (1 microg/L3)
• .005 ppm = 5 ppbs parts per billio
• 1 part per bilion roughly corresponds to 11 second 33-years , 1 penny per millions of dollars.
• Lowered or extremely tiny concentration are important can significantly result in environmental harm.
• Parts for Million Billiosn or Trillion
• tools measure "trace amounts" - at ng per and or part per trillion (ppt).
• a 1 ng per lire concentation ( (1 ng/L) = 11 ppt
• Express chemical mass the concentration of them in mass per unit volume
• mg/L than ppm, and microg/L compared to part per billion, ng/L over ppt

Percentage Concentration

• Above 10,000 mg are generally written with percentage %
• for correct puposes, the changes of 10,000 mg = 1% even though the densities are higher

Conversions

• 11 L = 1kg= 1000g
• 1g = 1000mg
• 1L = 1,000,00mg