Water Chemistry

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Water Chemistry

• Characteristics of water chemistry as needed by
  aquatic life forms.

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Data Quality Objectives

• The purpose of collecting information is to
  provide quantitative data required by the users
  to meet a program needs.
• By
• Screening for regulatory compliance
• Governmental, federal, state, and local laws
  mandating specific water conditions
• Documenting chronic or episodic problems
• Tracking trends or changes
• Providing original baseline information
• Extending monitoring coverage to augment other
  programs.

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pH

• The pH test is one of the most common analyses in
  water testing.
• pH is the measurement of the activity of hydrogen
  ions (H) for the acid side and hydroxide ions
  (OH-) for the base side.
• The pH scale is logarithmic, meaning that for
  every change in pH from say 6 to 5 is an increase
  or a factor of 10 times.
• So, a pH of 5 is 10 times more acidic than a pH
  of 6 and a pH of 11 is 1000 times more basic than
  a pH of 8.

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pH
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pH

• A range of pH 6.5 to pH 8.2 is optimal for most
  aquatic organisms.
• When pH drops below 6.5 the biological filtration
  system begins to suffer.
• After feeding the Tilapias respiration increases
  releasing carbon dioxide which reacts with the
  water to produce carbonic acid, thereby lowering
  the pH to dangerous levels.
• This lower pH is counteracted by adding baking
  soda at 20 of the mass of the food.

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Indirect Effect of pH

• Changes in waters pH can affect aquatic life
  indirectly by changing chemistry of water.
• Example toxic metals that were trapped in the
  sediment are released into the water at low pH
  levels.
• The toxicity of ammonia to fish varies
  tremendously within a small range of pH values
  (see next table).

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Dissolved Oxygen (DO)

• Aquatic animals need dissolved oxygen to live.
• Fish, invertebrates, plants, and aerobic bacteria
  all require oxygen for respiration.
• Water absorbs oxygen from the atmosphere at the
  surface until the water is saturated.
• Distribution of dissolved oxygen depends on
  currents caused by winds, turbulence, water flow,
  and thermal upwelling.

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DO Capacity

• The capacity of water to hold an amount of oxygen
  is limited by the waters temperature, salinity,
  and the atmospheric pressure (or altitude).
• Lets look at each of these parameters
  individually.

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DO Capacity Temperature

• As water temperature changes, an inverse
  relationship between temperature and DO capacity
  develops.
• Lower temperature higher potential dissolved
  oxygen level
• Higher temperature lower potential dissolved
  oxygen level

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DO Capacity Temperature

• During the summer, warmer water temperatures also
  increases aquatic organisms metabolism resulting
  in higher oxygen demands.
• Critically low oxygen levels in the warmer months
  coincide with increased oxygen demand from the
  aquatic organisms that include increased algae
  and decaying organic matter resulting in a die
  off of fish.

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DO Capacity and Dissolved Salts

• The various minerals dissolved in water lower the
  waters ability to hold oxygen.
• In fresh water, this effect is insignificant when
  compared to the effect of temperature.
• Lower salinity Higher potential for dissolved
  oxygen
• Higher salinity Lower potential for dissolved
  oxygen

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Potential dissolved oxygen levels (ppm) comparing
temperature to various salinity concentrations at
sea level.
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DO Capacity Atmospheric Pressure

• Lower atmospheric pressure found at higher
  altitudes, such as mountain lakes and streams,
  slightly decrease the solubility of oxygen in
  water.
• Lower altitude (higher pressure) Higher
  potential dissolved oxygen level
• Higher altitude (lower pressure) Lower
  potential dissolved oxygen level

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Significant Levels of Dissolved Oxygen

• The amount of dissolved oxygen required varies
  according to species and stage of life.
• DO levels below 3 ppm are stressful to most
  aquatic organisms.
• DO levels below 2 will not support fish.
• DO levels from 5 to 6 ppm are required for growth
  and noraml activity of fish.

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Dissolved Oxygen

• Hypoxia - low dissolved oxygen levels from 2 down
  to 0.5 ppm. Fish show signs of extreme stress
  and will die unless they can move to more
  oxygenated waters.
• Anoxia - the absence of oxygen, DO levels below
  0.5 ppm.

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Biochemical Oxygen Demand

• All living aquatic organisms, plants and animals,
  require oxygen.
• However, oxygen is also required for the
  decomposition of organic material by bacteria and
  other microorganisms, in addition, there are
  other chemical reactions that interact with
  oxygen.
• These uses of oxygen, not including the oxygen
  use by animals and plants, is termed the
  Biochemical Oxygen Demand.

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Biochemical Oxygen Demand

• Biochemical Oxygen Demand (BOD) is determined be
  measuring the dissolved oxygen level in a freshly
  collected sample of water and then subtracting
  the dissolved oxygen level in a sample from the
  same location that was stored for five days at
  20C in complete darkness.
• The difference between the two oxygen levels
  represents the amount of oxygen required for the
  decomposition of organic material and the
  oxidation of chemicals in the water during the
  storage, this is known as the BOD.

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Odor

• The human nose, not as good as say a wolf, but
  good enough to detect differences in water
  quality.
• Odor is caused by chemicals that originate from
  sources like municipal and industrial waste
  discharges, natural sources such as decomposing
  vegetable matter, microbial activity, or water
  that has absorbed a substance that it has flowed
  over or a substance that has fallen in to the
  water.

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Odor

• The human nose can accurately detect a wide
  variety of odors.
• To measure odor, collect a sample of water in a
  wide mouth beaker and waft the air over the water
  to your nose by waving your hand over the top of
  the beaker directing the air towards your nose.
• Use the following list of odors to describe what
  you smell.

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Descriptors that are common used for odor from
water

• Aromatic (spicy)
• Cucumber
• Balsamic (flowery)
• Geranium
• Nasturtium
• Sweetish
• Violets (Odor descriptors continue on to the
  next page)

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Descriptors that are common used for odor from
water (continued).

• Chemical
• Chlorinous
• Hydrocarbon
• Medicinal
• Sulfuretted
• Disagreeable
• Fishy
• Pigpin
• Septic (Odor descriptors continue on to the next
  page)

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Descriptors that are common used for odor from
water (continued).

• Earthy
• Peaty
• Grassy
• Musty
• Moldy
• Vegetable

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Alkalinity

• A healthy, productive freshwater lake has a pH
  of about 8, slightly alkaline.
• Natural pH buffers, primarily carbonate and
  bicarbonate, help maintain the pH at this level.
• Alkalinity measurement does not refer to pH but
  to the buffering capacity which is the ability of
  the water to resist pH change.

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Alkalinity

• A Total Alkalinity of 100 to 200 ppm will
  stabilize the pH level in a stream.
• Freshwater ranges between 20 and 200 ppm.
• Seawater ranges between 100 to 125 ppm.
• Alkalinity is measured by adding an acid of known
  concentration in a dropwise manner until the pH
  of the sample drops to a specific level as shown
  by a color change.

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Hardness

• Hardness refers primarily to the amount of
  calcium and magnesium in the water.
• Source of hardness is from the leaching of rocks.
• Calcium is important to aquatic plant cell walls,
  shells, and bones of aquatic organisms.
• Magnesium is essential nutrient for plants and a
  component of the chlorophyll molecule.

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Hardness

• Waters with calcium levels of 10 ppm or less are
  usually oligotrophic and can only support sparse
  plant and animal life.
• Calcium levels of 25 ppm are typical of eutrophic
  waters.
• Typical freshwater magnesium levels range from 5
  to 50 ppm.
• There are no health standards for water hardness,
  but hard water causes problems with scaly
  deposits in plumbing and appliances and decreased
  cleaning action of soaps and detergents.

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Other parameters used to monitor and study water
quality

• Temperature
• Thermal stress and shock can occur in sensitive
  fish with a change of water temperature of as
  little as 1 to 2C over a 24 hour period.
• Tilapia are a hardy fish and can with stand a
  temperature change of up to 3C change within
  minutes.

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Other parameters used to monitor and study water
quality

• Turbidity
• The cloudiness of water caused by suspended
  matter which scatters light.
• Microscopic organisms contribute to turbidity
  especially if there are excess nutrients in the
  water that allow great increases in microscopic
  organisms populations.
• Sediment from erosion increase the cloudiness.
• Suspended particles near the surface absorb
  sunlight leading to an increase in temperature of
  the water.

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Other parameters used to monitor and study water
quality

• Color
• The color of water can tell a great deal about
  the source and content.
• Water color results from dissolved substances and
  suspended matter.
• Natural metallic ions, plankton, algae,
  industrial pollution, and plant pigment from
  humus and peat contribute to color in water.
• Use a standardized color chart.

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Other parameters used to monitor and study water
quality

• Nutrients
• The addition of phosphorus, nitrogen and other
  nutrients to a body of water results in increased
  plant growth, a process called eutrophication.
• Eutrophication is more of an issue in slow moving
  water, fast moving water normally prevents the
  establishment of floating aquatic plants, algae,
  and epiphytes even in the presence of high
  concentrations of nutrients.

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Other parameters used to monitor and study water
quality

• Nutrients
• Phosphate
• Phosphorus occurs in natural waters in the form
  of phosphates, there are numerous types of
  phosphates, some requiring extensive laboratory
  procedures.
• We will only work with the orthophates that come
  from fertilizers from farms and residential lands.

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Other parameters used to monitor and study water
quality

• Nutrients
• Phosphate (continued)
• Total phosphorus levels of 0.03 ppm contribute to
  eutropication.
• Total phosphorus levels of 0.1 ppm may stimulate
  plant grow beyond the normal eutrophication rates.

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Other parameters used to monitor and study water
quality

• Fecal Coliform Bacteria
• Is normally found in the lower intestines of
  warm-blooded animals.
• Their presence is an indicator of raw sewage or
  fecal contamination in the water.
• Although coliform bacteria themselves are not
  pathogenic, their presence indicates possible
  fecal contamination and the possible presence of
  intestinal pathogens responsible for a variety of
  diseases.

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General requirements for Coliform Bacteria in
water
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Other parameters used to monitor and study water
quality

• Total Dissolved Solids

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Other parameters used to monitor and study water
quality

• Salinity
• Salinity is the total of all dissolved salts in
  water, normally expressed in part per thousand
  (ppt).
• In an estuary, where freshwater flows and mixes
  with sea water, the salt concentration ranges
  from 0 to 35 ppt.
• The salt concentration of water affects the
  distribution of animals and plants.

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Salt concentrations
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