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WELCOME. PHYSICAL, CHEMICAL & BACTERIOLOGICAL CONTAMINATION OF WATER AND WATER QUALITY STANDARDS. Distribution of water on earth. Ocean and sea - 97% Snow and ice caps - 2% Rivers,lakes, Ground water - 1%. UNIVERSAL SOLVENT. QUALITY DEMERIT

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distribution of water on earth
Distribution of water on earth
  • Ocean and sea - 97%
  • Snow and ice caps - 2%
  • Rivers,lakes, Ground water - 1%
universal solvent
UNIVERSAL SOLVENT
  • QUALITY
  • DEMERIT
  • 45 LAC WELLS

AND

50 LAC SEPTIC TANKS ( ?)

contamination
contamination
  • Geological
  • Human activities

. Organic waste

Industrial waste

safe drinking water
Safe drinking water

Free from pathogenic organisms

Clear

Not saline

Free from offensive taste or smell

Free from compounds that may have adverse effect on human health

Free from chemicals that cause corrosion of water supply systems

water quality parameters
WATER QUALITY PARAMETERS
  • Physical parameters
  • Chemical
  • Bacteriological
colour
Colour
  • May be due to the Presence of organic matter,metals(iron, manganese) or highly coloured industrial waste
  • Aesthetically displeasing
  • Disirable that drinking water be colourless
  • Disirable limit, 5 Hazen unit
  • Permissible limit 25 Hazen Unit
taste and odour
Taste and Odour
  • Mainly due to organic substances, ,Biological activity, industrial pollution
  • Taste buds in the oral cavity specially detect inorganic compounds of metals like magnesium, calcium, sodium, copper, iron and zinc
  • Water should be free from objectionable taste and odour.
turbidity
Turbidity
  • Caused by suspended matter
  • High level turbidity shield and protect bacteria from the action of disinfecting agents
  • Disirable limit-5NTU

should be below 1 NTU when disinfection is practiced

Permissible limit-10NTU

slide12
pH
  • It is the measure of hydrogen ion concentration
  • Neutral water pH-7
  • Acidic water has pH below 7
  • Basic water has pH above 7
  • Disirable limit 6.5-8.5 Beyond this limit the water will affect the mucous membrane and water supply system
substances that change ph of water
Acidic

Industries

Sugar - 5 – 6

Distillery 3 - 4

Electro-

Plating unit 2.5-4

Pickle 2 - 3

Basic

Paper 8 – 10

Textile 8.5-11

Fertiliser 6.5- 9

Oil Refine-

ries 6.5-9.5

Substances that change pH of water
hardness
HARDNESS
  • Capacity of water for reducing and destroying the lather of soap
  • It is total concentration of calcium and magnesium ions
  • Temporary hardness – Bicarbonates of Calcium and Magnesium
  • Permanent hardness – Sulphates, chlorides and nitrates of calcium and magnesium
hardness contd
Hardness – contd…
  • 0 – 50 mg/l - soft
  • 50 – 150 mg/l - moderately hard
  • 150 – 300 mg/l - hard
  • 300 above - very hard
  • Surface water is softer than ground water
  • Causes encrustations in water supply structures
alkalinity
ALKALINITY
  • Capacity to nutralise acid
  • Presence of carbonates, bi-carbonates and hydroxide compounds of Ca, Mg, Na and K
  • Alkalinity = hardness, Ca and Mg salts
  • Alkalinity > hardness - presence of basic salts, Na, K along with Ca and Mg
  • Alkalinity < hardness – neutral salts of Ca & Mg present
slide18
IRON
  • One of the earth’s most plentiful resource
  • High iron causes brown or yellow staining of laundry, household fixtures
  • Metalic taste, offensive odour, poor tasting coffee
  • Cause iron bacteria
  • Acceptable limit – 0.3 mg / l
chloride
CHLORIDE
  • Causes
  • Dissolution of salt deposit
  • Discharge of effluents
  • Intrusion of sea water
  • Not harmful to human beings
  • Regarding irrigation – most troublesome anion
  • Acceptable limit - 250 mg/l
nitrate
NITRATE
  • Increasing level of nitrate is due to
  • Agricultural fertilizers, manure,animal dung, nitrogenous material ,sewage pollution
  • (blue baby diseases to infants)
  • Maximum permissible limit 45 mg / l
flouride
FLOURIDE
  • Occurs naturally
  • Long term consumption above permissible level can cause –
  • dental flurosis (molting of teeth)
  • Skeletal flurosis
  • Acceptable limit – 1 mg / l
  • Maximum permissible limit – 1.5 mg / l
  • Remedy – 1) Deflouridation

2) Mixing Fluride free water

3) Intake of vitamin C,D, calcium,antioxidants

flouride causes
FLOURIDE CAUSES

Three types of Fluorosis

1. Dental Fluorosis

2. Skeletal Fluorosis

3. Non-skeletal Fluorosis

arsenic
ARSENIC
  • Occur in ground water from arseniferous belt
  • Industrial waste, agricultural insecticide
  • High arsenic causes 1) various type of dermatological lesions, muscular weakness, paralysis of lower limbs, can also cause skin and lung cancer
  • Acceptable limit – 0.05 mg / l
heavy metals
Heavy Metals
  • Present as mineral in soil and rocks of earth
  • Human activities

Battery – Lead & Nickel

Textile - Copper

Photography – Silver

Steel production – Iron

pesticides
Pesticides
  • Cancer
  • Birth defects
  • Blood disorder
  • Nervous disorder
  • Genetic damage
residual chlorine
RESIDUAL CHLORINE

Chlorine added to water forms hypochlorite ions and hypochlorite acids

Chlorine demand – Quantity required for killing micro organisms and reacting with ammonia, organic compounds etc.

Free residual chlorine – To take care of post contamination

Desirable – 0.2 mg / liter

slide30

Measures of Water Quality

Some of the Most basic and Important Measures

Dissolved Oxygen

Biochemical Oxygen Demand

Solids

Nitrogen

Bacteriological

slide31

Dissolved Oxygen (DO)

Typically Measured by DO probe and Meter

Electrochemical Half Cell Reaction

slide32

Biochemical Oxygen Demand (BOD)

Amount of oxygen used by microorganisms to decompose

organic matter in a water

Theoretical BOD can be determined by balancing a

chemical equation in which all organic matter is

converted to CO2

Calculate the theoretical oxygen demand of 1.67 x 10-3 moles of

glucose (C6H12O6):

C6H12O6 + O2 CO2 + H2O general, unbalanced eqn

C6H12O6 + 6 O2 6 CO2 + 6 H2O

1.67x 10-3moles glucose/L x 6 moles O2/ mole glucose x 32 g O2/mole O2

= 0.321 g O2/L = 321 mg O2/L

slide33

BOD Test

Dark

20oC

Time

Standard – 5 days

Ultimate

slide34

BOD = I - F

I = Initial DO

F = Final DO

If all the DO is used up the test is invalid, as in B above

To get a valid test dilute the sample, as in C above. In this

case the sample was diluted by 1:10. The BOD can then be

calculated by:

BOD = (I – F) D D = dilution as a fraction

D = volume of bottle/(volume of bottle – volume of dilution water)

BOD = (8 – 4) 10 = 40 mg/L

slide35

For the BOD test to work microorganisms have to be present.

Sometimes they are not naturally present in a sample so we have

to add them. This is called “seeding” a sample

If seed is added you may also be adding some BOD. We have to

account for this in the BOD calculation:

BOD = [(I – F) – (I’ – F’)(X/Y)]D

Where: I’ = initial DO a bottle with only dilution water and seed

F’ = final DO of bottle with only dilution water and seed

X = amount of seeded dilution water in sample bottle, ml

Y = amount of seeded dilution water in bottle with only

seeded dilution water

slide36

Example

Calculate the BOD5 of a sample under the following conditions.

Seeded dilution water at 20oC was saturated with DO initially.

After 5 days a BOD bottle with only seeded dilution water had a

DO of 8 mg/L. The sample was diluted 1:30 with seeded dilution

water. The sample was saturated with DO at 20oC initially.

After five days the DO of the sample was 2 mg/L.

Since a BOD bottle is 300 ml a 1:30 dilution would have 10 ml

sample and 290 ml seeded dilution water.

From the table, at 20oC, DOsat = 9.07 mg/L

BOD5 = [(9.07 – 2) – (9.07 – 8)(290/300)] 30 = 174 mg/L

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