TREATMENT OF WATER

Water treatment  is done to make the water clean and pure for purpose of drinking ,cocking and for other household uses.Their various impurities are present and it must be removed before consuming such water.we are going to discuss the different methods of treatment of water.

The treatment of water is dependent on the quality of raw water, and desired standard of treated water.

There are various method of water treatment :-

1-     Screening

2-     Aeration

3-     Coagulation and flocculation

4-     Sedimentation

5-     Filtration

6-     Disinfection

7-     Softening

8-     Fluoridation or Defloridation

9-     Desalination

 

If the water is extracted from the surface and is provided storage and extracted from ground having turbidity less than 10 NTU.

The sample is free from test, odour and dissolved gases.In this case plane disinfection is sufficient  for the treatment of water.

If surface water contain excessive iron dissolved carbon dioxide and odourous gases then treatment given are :- aeration , screening , coagulation and flocculation , sedimentation , filtration and dis-infection.

NOTE

If slow sand filtration are used for the filtration it is never proceeded by coagulation and flocculation.

In order two remove bad test , odour , bad gases and minerals .Excess chlorine from water activated carbon in powder form can be used due to its strong adsorption properties , it removes all impurities from water. It is recommended to use activated carbon during process of coagulation and flocculation.

Different Methods of treatment of water are discussed below

SCREENING

Screening is the method of treatment of water in which screens are used.

Screening is done to remove the heavier suspended impurities from the water like plants , animals ,stones , etc.

Screening is generally adopted with help of two types screens

1-     COARSE SCREEN

2-     FINE SCREEN

 

COARSE SCREEN

It is in the form of bars of diameter 25 mm and spacing  of 20 to 100 mm is maintained between the bars .

AERATION

In aeration water is brought in intimate contact with air  so as to remove undesirable gases lie cabon dioxide from the water. It is also used to add oxygen in the water to carry out thee oxidation of undesirable substances like organic matter and oils .

It is also done to remove volatile liquid  like phenol and humid liquid from water.

 

SEDIMENTATION

The particle that settle out that is known as sediment  , and in water treatment is known as sludge.

In water sedimentation process for treatment of water of water  might be used to reduce the  concentration of particle in suspension before the application of coagulation , to reduce the amount of coagulating chemicals needed.

Sedimentation is one of the several method for application prior to filtration , other options include dissolved air floatation and some methods of filtration . Generally such solids – liquids separation processes are sometimes referred to as clarification processes.

There are variety of methods for the sedimentation process like inclined plate , radial flow, horizontal flow etc.

COAGULATION AND FLOCCULATION

The efficiency of sedimenation is very less when water contain very fine suspended solids , hence to improve its efficiency co-gulation aided sedimentation is adopted for the treatment of water

The entire process of this coagulation for the treatment of water is completed in three stages;-

Co-gulatiom (fast mixing )

Flocculation (slow mixing)

Sedimentation

Coa-gulation

It is process in which certain chemicals known as coagulants are added in the water so as to neutralise negative protective carge over the particles in order to increase their contact opportunity in subsequent stages.a certain minimum amount of energy i required for these neutralisation known as THRESHOLD ENERGY

 

FILTRATION

Filtration is most often used for the treatment of water  as the limiting step to remove the flocs and finer waste particles  .It is also used to remove organic matter , micro-organism and dissolved minerals from the water.

GRAVITY FILTER

Gravity filter is the type of filter in which head required by the water to pass through filter medium is provided by the water to pass through filter medium medium .

These filter are of two types

1-     Slow sand filter

2-     Rapid sand filter

 

PRESSURE FILTER

Pressure filter is the type of filter in which head required by the water to pass through filter medium is provided artificially by external application of pressure over the water.

 

DISINFECTION

Disinfection is  the process that used for the treatment of water .This involves the process  of removal of disease causing micro-organism from the water.

The process of removal of all the micro-organism is called sterlisation .The process of removal of only disease causing microbes is called disinfection.

During disinfection it is assumed that disinfectant destroys the microorganism by fallowing mechanism:-

1-     By inactivating the enzymes of the micro-organism required to perform metabolic activities.

2-     By damaging the cell walls of micro-organism

3-     By changing the nature of their self protoplasm.

4-     By altering the permeability of their cells.

 

SOFTENING

Softening is  the method used for the treatment of water ,It is done to remove the hardness from the water both temporary and permanent.

 

DEFLORIDATION

The process of removal of fluorine from the water if its concentration is more than 1.5mg/l.

There are various chemicals are added to remove the fluorine , some chemicals are :-

-        ACTIVATED CARBON

-        LIME

-        CHARCOAL

 

FLORIDATION

The process of addition of fluorine in the water if its concentration is less than 1mg/l is known as the fluoridation.

Chemicals added to increase the concentration of fluoride are as  fallow:

-        Sodium fluoride

-        Sodium silica fluoride

-        Hydro silica acid

  DESALINATION

Desalination is the process  which involves the process of talking out salt from the water and make it drinkable . Many countries uses desalination as a way of purifying the water and make it reliable water for drinking , cocking , washing .