Unit – 2

Physical, chemical and biological characteristics of water

Q1) Explain Physical characteristics of Water?

A1)

Following physical parameters are used to calculate the physical quality of water.

1. The Colour
2. Taste and Odour
3. Temperature
4. Turbidity

1. Colour:

• The pure natural water does not have any colour. The presence of any organic and in-organic matter in the water gives the colour like green, blue, black, red etc.
• When the industrial waste gets mixed up with the surface water the colour is added to the natural water.
• It is necessary to investigate the source of this chemical contamination must be indentified to reduce the danger of water pollution.
• The changes in the colour of water can be qualified by making use of the space photometer.
• The unit of measurement of intensity of colour in the water is cobalt-platinum (copt) unit.

2. Taste and Odour:

• In fact the pure water is tasteless and odourless. The organic matter, industrial wastes, gives a different odour and the taste also changes.
• In case of stored water, the odour and tastes are developed. The underground water, mainly.
• The well water gets a typical taste and odour also because it gets some dissolved chemicals when it percolates through the rocks. Such water is also called as hard water.

3. Temperature:

• We generally prefer to consume cool water but if the water is warm the growth of micro-organisms is promoted and the taste, odour and colour also get changed.

4.Turbidity:

• It is the suspended matter like mud, clay, algae and micro-organism that make the water turbid.
• This turbidity can be measured by using turbidity meter and the unit of measurement is Nephelometric Turbidity unit (NTU).
• The unit of measurement is PPM or mg/per litre on silica scale e.g. Are mg of colloidal silica suspended in one litre of distilled water, produces one unit of turbidity.

Q2) Explain Chemical characteristics of Water?

A2)

Following Chemical parameters are used to calculate the chemical quality of water.

1. Total Dissolved Solids (TDS)
2. PH
3. Hardness

1. Temporary hardness
2. Permanent hardness

1.Total Dissolved Solids (TDS)

• They are composed of inorganic salts, mainly the chlorides, sulphates and bi-carbonates of calcium, magnesium, potassium and sodium.
• The industrial waste makes the addition of these TDS. It also is added in case of underground water which collects those inorganic components in the process of percolation.
• The TDS in the water can be measured by simple evaporation method or by using TDS meter. The unit of measurement of T.D.S. Is mg/l (mg/per litre).

2. PH

• It is the value of hydrogen ion concentration in the water on the base of the pH value, it is called as acidic or alkaline.
• The normal pH value of water is seven, if it is less than seven, the water is called acidic water, if it is more than seven it is called as Alkaline water.
• The pH value is measured by pH meter or by using pH paper, which changes its colour when dipped in the water.
• By using the colour code, the pH value can be measured.

3.Hardness

• The hardness to the water is of two types:

a. Temporary hardness:

• It is caused by soluble bicarbonates which can be removed by boiling the water.

b. Permanent hardness:

• It is caused by sulphate and chlorides of calcium and magnesium. It can be removed by using iron exchange methods.

The following components make the water hard:

• Sodium, Iron and manganese, chlorides, sulphate, Nitrates. The Fluorides in the water is an important parameter of good quality of water.
• If the concentration is less than 1.0 mg/l, it gives rise to dental caries among the children and if it is more than 1.5 mg/1, it may cause dental and skeletal flurosis.
• The fluoride content in the water is measured by spectrophotometer.
• The toxic materials like heavy metals, pesticides, industrial chemicals, can have acute effects as the human being if consumed in large quality or for a long period.

Q3) Explain Biological characteristics of water?

A3)

The presence of micro-organism like bacteria and Virus make the water contaminated. All the microorganism are not harmful to human beings but the microorganism which are pathogenic cause water borne diseases.

Biological Tests:

• For the Biological or Bacteriological following tests are observed.

1. Total count of Bacteria
2. Bactria coli (B-coli) Test or E Coli Test

1.Total count of Bacteria:

• In this, the total number of bacteria present in one millilitre of sample water are counted. The sample water is diluted one millilitre water is diluted in 99 ml of sterilized water.
• Then 1 ml diluted water is mixed with 10 ml of agar of gelatine i.e. culture medium. This mixture is then kept in the Incubator at 37°C temperature for 24 hours or may be at 20°C temperature for 48 hours.
• After this required period the sample is taken out from the incubator and then the colonies of bacteria are counted under microscope.
• This product of the number of colonies and the dilution factor will give the total number bacteria/per ml of the undiluted water sample.

2. Bactria coli (B-coli) Test OR E Coli Test

• Two tests are designed for B-coli. The 1st test is known as presumptive test and the 2nd test is known as the confirmative test.
• In case of 1st i.e. the presumptive test, a definite amount of diluted water sample water, is kept, in standard fermentation tubes, which contain, lactose broth, as a culture medium.
• These tubes are kept in the incubator at 37°C temperature for 24 hrs to 48 hrs.
• If, after this period, a gas is produced in these fermentation tubes, it is an indication of presence of B coli and if these is no gas formation it is an indication of no-presence if B-coli in the sample. In the 2nd i.e. the confirmation test some sample from presumptive tube is taken and is placed in another fermentation tube which contains Brilliant green lactose bile, as a culture medium.
• It is also kept in the incubator at 37°C temperature for 48 hrs. If it again produces gas that confirms the presence of B-coli and water is unsafe for consumption purpose.
• Now a days, an another method has been introduced to find out the B-coli. In is known as "Membrane Filter Technique." It is a very simple technique. The sample water is filtered through a sterilized membrane of special design to collect all the bacteria, present in the sample water. The membrane is then put contact of culture medium i.e. M-Endo's medium, in the incubator at 37°C temperature for 24 hrs.
• After the incubation period the membrane is kept under the Microscope to count the colonies of Bacteria. Previously the standard statistical tables were referred to determine the Most Probable Number (MPN) of B coli per 1000 ml, MPN indicates the density of bacteria in the water sample.
• As the new technique 'Membrane filter' has been. Introduced the MPN methods are not used.
• In drinking water at least 5 samples of 100 ml, each should be collected and tested. The number of C-coli colonies per std sample should not be more than 4 per 100 ml of sample water.

Q4) What is water quality criteria?

A4)

• The quality of drinking water depends upon various parameters such Physical, Chemical, and as Microbiological.
• The quality of water used for drinking must be followed to achieve good health and to control various water borne or water induced diseases.
• In the third world countries like the Asian and African countries about 90% of the total morbidity cases, in a year, are related to the consumption of water which does not maintain the given standards of drinking water.
• There are various agencies who play an important role in specifying the norms to fix the water quality standards such as-

1. Indian Standards Institution (I.S.I)
2. World Health Organization (W.H.O)
3. United States Public Health Service (U.S.P.H.S)
4. Indian Council of Medicine Research (I.C.M.R)

Q5) Explain Quality of water as per IS 10500 (2012)?

A5)

Physical parameters as per IS 10500(2012) are as follows:

Q6) What are water borne diseases?

A6)

Human health gets affected by the consumption of contaminated water, either directly or through food. The water related diseases may be grouped as:

1. Water borne diseases
2. Water based or water induced diseases
3. Water related vector diseases
4. Water diseases

1.Water Borne Diseases:

• These diseases are caused by the consumption of contaminated water having virus or bacteria. The viral diseases are viral hepatitis A, hepatitis E, Poliomyelitis and rotavirus diarrhoea.
• The Bacterial diseases are, Typhoid, and Paratyphoid fever, Bacillary dysentery, E Coli diarrhoea and Cholera etc.
• Excess levels of nitrates cause blood disorders, the pesticides in the drinking water may cause cancer and neurological disorders. It may cause infertility.

2.Water Based or Water Induced Diseases:

• Aquatic organism that lives a part of their life cycle in water and the rest as a parasite in human body lead to several diseases e.g. Guinea worm disease is spread through Cyclops.
• The round worm, thread worm, live in the small intestine mainly of children.

3.Water Related Vector Diseases:

• The insects such as mosquitoes that breed in stagnant water, causes Malaria, Filasia, Dengue fever.
• Among these Dengue fever causes very high mortality.

4.Water Scarcity Diseases:

• In the areas having, scarcity of water and lack of sanitation, there is a high incidence of diseases, such as Tuberculosis (T.B.), Leprosy, Tetanus etc.
• They are the results of poor personal and social hygiene, mainly in the rural areas of India. It may cause the diseases like Trachoma, Conjunctivitis and scabies.
• All the above diseases can be put under control if the safe drinking is made available and the level of personal and social hygiene is improved by the government and non-government organizations.

Q7) Explain Natural purification of water?

A7)

• Water purification for human intake functions is composed withinside the elimination of various contaminants as chemicals (i.e., pollutants, poisonous metals), organic contaminants (algae, bacteria, fungi, parasites, viruses), suspended solids, and gases.
  There are numerous strategies used withinside the water purification technique, which include: (1) bodily methods, which include filtration, sedimentation, or distillation; (2) organic methods, which include sand filters, lively carbon; (3) chemical methods, which include flocculation, chlorination, using ultraviolet light.
• Regarding the bodily tactics utilized in water purification, those fluctuate withinside the phenomenon on which the methods are primarily based totally.
• For instance, filtration is primarily based totally at the separation of solids from fluids, with the aid of using interposing a porous medium (filter) which keeps the strong debris and permits the fluid to byskip on the alternative side.
• On the alternative hand, the sedimentation method makes use of the gravitational pressure which determines the solids to shape a deposit at the lowest of the tube containing infected water, even as distillation includes the transformation of the liquid (water) right into a vapor phase, technique that is primarily based totally at the distinction withinside the volatility of the compounds.
• Slow sand filters constitute one instance of organic tactics utilized in water purification, which suggests the usage of 1–2 m deep tubes full of sand, which preserve the impurities gift withinside the filtered water.
• Activated carbon (charcoal), some other applied method, is a microporous carbon with excessive floor place and more advantageous adsorption properties.
• In clinical terms, flocculation is a technique wherein colloids in suspension grow to be destabilized after the addition of a clarifying agent; concerning the water purification technique, the flocculation phenomenon can confer with the destabilization and coagulation of contaminants gift withinside the water. Water
• Chlorination is typically encountered withinside the remedy of water deliver and is composed withinside the addition of chlorine or hypochlorite to kill microbes and to save you the spreading of waterborne diseases.
• The use of electromagnetic light, specially with brief wavelength (in ultraviolet range) is typically utilized in disinfection, because of the truth that it produces gaps withinside the shape of nucleic acids of microorganisms disabling their cell functions.
• This technique is frequently utilized in water decontamination.