Water Quality

WATER QUALITY

Water Quality ■

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Water quality refers to the basic chemical and physical characteristics of water that determine its suitability for life or for human uses. Some basic water quality variables include: – – – – – – –

Color, Taste and Odor Temperature Conductivity pH Turbidity Alkalinity Hardness

Water Quality Analysis ■

Physical Factors including suspended materials (called suspended solids) and dissolved substances (dissolved solids)

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Chemical Factors including concentrations of ions, pollutants, etc…

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Biological Factors including presence of organisms, plankton, fish, nutrients, etc…

Water Quality: Color, Taste & Odor ■ Pure

water is colorless, tasteless and odorless in nature. ■ But in most origins T/O are natural. ■ Bacteria large contributor as water flows through geologic deposits. ■ Salt or seawater intrusion in coastal areas.

Water Quality: Color, Taste & Odor Human sources – landfill activities, agricultural activities, industrial waste disposal. ■ Hydrogen Sulfide most common odor. ■ Dissolved iron create some taste, unpalatable. ■ Brown water is most common complaint. ■

Water Quality: Temperature ■ Temperature

is a basic water quality variable ■ Temperature determines the suitability of water for various forms of aquatic life

Water Quality: Conductivity ■ Conductivity

measures the ability of water to conduct an electrical current ■ Conductivity is a good way to determine the ionic strength of water because the ability of water to conduct a current is proportional to the number of ions in the water

Water Quality: pH ■

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pH is a measure of the acidic or basic characteristics of water Specifically, pH = -log [H+] So a pH of 7 means the [H+]=10-7 A pH of 7 is considered neutral, below 7 is acidic and above 7 is basic

Water Quality: pH ■

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Organisms generally prefer a pH of 5-9 with some being even more picky A near neutral pH will allow the greatest diversity of life

Physical Factors TSS – Total Suspended Solids can be measured by taking the amount of solid separated from a water sample. Measurement in mg/L TDS – Total dissolved solids can be measured through evaporation and measured in mg/L

Measuring Water Clarity ■

Turbidity is a measure of the degree to which the water looses its transparency due to the presence of suspended particulates.

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A turbidity measurement could be used to provide an estimation of the TSS (Total Suspended Solids)

Causes of Turbidity ■

There are various parameters influencing the cloudiness of the water. Some of these are: – – – – –

Sediments from erosion Resuspended sediments from the bottom Waste discharge Algae growth Urban runoff

Water Quality: Alkalinity ■ The

alkalinity of water is a measure of its capacity to neutralize acids. ■ Alkalinity of natural waters is due to the salts of carbonates, bicarbonates, borates, silicates and phosphates along with the hydroxyl ions in the Free State.

Water Quality: Alkalinity ■

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The ability of a water body to resist acidification is called alkalinity Alkalinity is generally attributable to the amount of carbonate (CO3-2) and bicarbonate (HCO3-) in the water Alkalinity is generally measured in units of mg/L as CaCO3

Water Quality: Alkalinity ■ ■

CO3-2 can absorb one H+ to become HCO3HCO3- can absorb another H+ to become H2CO3

Water Quality: Alkalinity ■ Alkalinity

values provide guidance in applying proper doses of chemicals in water and wastewater treatment processes, particularly in coagulation, softening and operational control of anaerobic.

Water Hardness Water hardness is a traditional measure of the capacity of water to precipitate soap. ■ Hardness of water is not a specific constituent but is a variable and complex mixture of cations and anions. ■ It is caused by dissolved polyvalent metallic ions. ■

Water Hardness ■ In

fresh water, the principal hardness-causing ions are calcium and magnesium which precipitate soap. ■ Total hardness is defined as the sum of the calcium and magnesium concentration, both expressed as CaCO3, in mg/l.

Water Hardness Temporary: ■ Ca and Mg Bicarbonates ■ Will precipitate minerals upon heating Permanent: ■ Ca and Mg Sulfates or Chlorides ■ Use of ion-exchanger is necessary – Adds sodium

Carbonate &Non –carbonate Hardness ■ Carbonate

(temporary / equivalent to total alkalinity) ■ Non-carbonate (permanent / excess of total alkalinity )

Carbonate Hardness ■ When

total hardness is numerically greater than that of total alkalinity expressed as CaCO3, the amount of hardness equivalent to total alkalinity is called 'carbonate hardness'.

Carbonate Hardness ■ Carbonate

hardness refers to the amount of carbonate and bicarbonates in solution that can be removed or precipitated by boiling. ■ This type of hardness is responsible for the deposition of scale in hot water pipes and kettles

Non-carbonate Hardness ■ When

total hardness is numerically greater than that of total alkalinity expressed as CaCO3, the amount of hardness which is more than the total alkalinity is called ‘non carbonate hardness'.

Non-carbonate Hardness ■ Non-carbonate

hardness is caused by the association of the hardnesscausing cation with sulfate, chloride or nitrate and is referred to as "permanent hardness". ■ This type of hardness cannot be removed by boiling.

Advantage of Hard Water ■ May

have firming effect on fruits and vegetables

Disadvantages ■ Scale

formation ■ Reduce heat exchange rate ■ Corrosion – Salts make water more basic ■ Difficulties in cleaning

Degree of Hardness PPM Calcium ■ Soft

– Less than 20 ■ Slightly Hard - 20-40 ■ Hard 40-80 ■ Very Hard Above 80