Treatment of domestic waste water

TREATMENT OF DOMESTIC WASTE WATER 

1. Equalization
2. Neutralization
3. Physical treatment
4. Chemical treatment
5. Biological treatment

1. Equalization

 Equalization consists of the holding of the waste water for some predetermined time in a continuously mixed brains to produce uniform waste water.

2. Neutralization:

 Neutralization means neutralizing the excessive acidity or alkalinity of the particular waste water by adding alkai or acids, respectively to the waste water. This may be achieved either in equalization tank where possible or a separate neutralization
tank may be used.

3. Physical treatment:

 Physical treatment consists of separating the suspended inorganic matter by physical
like sedimentation and floatation.

i) Sedimentation: 

Sedimentation is employed to separate the heaviers settable solids and hence
sedimentation tank may be
provided only when the waste water
contains a high percentage of such
heavy inorganic solids.

ii) Floatation: 

Floatation consists of creation of the air bubbles in the waste tank, by introducing of air into the tank from the bottom. The
 rising  air bubble attach themselves
to the bottom suspended particles
increasing their buoyancy and removed by skimming.

4.CHEMICAL TREATMENT 

Chemical Treatment is often necessary
before the biological treatment.
The chemical treatment is used to remove
the dissolved organic matter from the
waste water and may consists one or more
of the following process.
i) Reverse osmosis or hyper filtration

 Reverse  OSMOSIS

In reverse osmosis treatment process the
waste water containing dissolved salts are
filtered through semi permeable
membrane at a pressure higher than the
osmosis pressure. Such treatments
required pre-treatments like
i) Activated Carbon adsorption or
ii) Chemical precipitation followed by
same kind of filtration

ELECTRODIALYSIS

In electrodialysis treatment process
dissolved salts from waste water are
separated by passing an electric current
through the waste water tank. Installed
with long exchanger members. This
treatment process also requires some
pretreatment as is required in reverse
osmosis process.

 CHEMICAL OXIDATION 

In chemical oxidation chemicals are to required to reduce substance like ammonia and ozone are used to reduce substance like ammonia and cyanide etc from the waste water in order to reduce BOD load on biological treatment.

CHEMICAL COAGULATION 

Chemical coagulation is adopted in treating
raw water supplies and helps in sedimentation of unsettlable micro and
colloidal impurities. Which get absorbed in
the gelatinous floes. Formed by the
chemical reaction between the coagulated
and alkaline present in raw water.

ADSORPTION 

Adsorption is generally used to remove
non-biodegradable organics (like synthetic
detergents), colour and odour from the
waste water. The process involves passing
the pre-treated waste water through the
beds of activated carbon, as discussed.

DEIONIZATION 

De-ionization involves a similar passage of
waste water through the beds of synthetic
ion exchange resins, like organic cyanide,
which may be present in certain specific
industrial waste water.

THERMAL REDUCTION 

Thermal reduces required burning and
consequent oxidation of some toxic and
refractive substance like organic cyanide,
which may be present in certain specific
industrial waste water.