WATER FOR DOMESTIC USE

WATER THAT IS SUITABLE FOR DRINKING IS CALLED POTABLE WATER.

TREATMENT OF WATER FOR DOMESTIC USE

1. Screening2. Sedimentation3. Coagulation4. Filtration5. Disinfection of water

SCREENINGIn order to remove floating impurities screening is carried out. screens of different kinds such as Bar screen, drum screen, and micro screeners are employed. These screens retain any floating impurity and are cleaned.

SEDIMENTATIONSedimentations a process of removing suspended impurities by allowing the water to stay undistributed for some time in large tanks when most of suspended particles settle down due to force of gravity. The accumulation of the debris at the bottom of tank is periodically scraped and removed.•The velocity with which a particle in water falls under the action of gravity depends upon following factors:•The horizontal flow of velocity of water•The size of particle•Temperature of water

Coagulation

Coagulation is a process of removing colloidal particles from water by addition of certain chemicals known as coagulants before sedimentation.

Colloidal particles present in water either do not settle down at all or take a very long time.

These coagulants reacts with bi-carbonates present in water and form bulky gelatinous precipitate called flock.

Colloidal particles are very small sized particles possessing either positive or negative charge. colloidal particles of clay possess negative charge.

Types of filters:

Gravity sand filter Pressure filter

Gravity sand filters

PRESSURE FILTER

GRAVITY SAND FILTER•Filtration is a process of removing insoluble colloidal and bacterial impurities by passing water through a bed of proper sized material.•It consists of a large shallow rectangular tank made of concrete. At the bottom of the tank, there is a channel of brick through filtered water goes out.•The rate of filtration after 24 hours of use becomes slow due to clogging of pores of sand layer is scrapped off and replaced by a new sand layer. And the scrapped sand is reused.•These filters are also best for municipal water supply and the scrapped sand is re-used after washing with water.

PRESSURE FILTER •Body aid is used when the slurry is low in solids content with fine and slimy particles that are difficult to filter. To enhance filtration coarse solids with large surface area are added to the slurry and serve as a body-aid that captures and traps in its interstices the slow filtering particles and produce a porous cake matrix. The amount added depends on the nature of the solids and varies from ½ for non-compressible and up to 5 times for gelatinous solids.•Precoating the plates with a 2-3 mm thick medium of a known permeability and its application requires skills since it takes-up effective cake volume, lengthens the cycle time and an over consumption can be quite costlyThe following materials serve as body-aid or are used

to form a precoat: Diatomaceous Earth (also called Diatomite) consisting

of silicaceous skeletal remains of tiny aquatic unicellular plants.

Perlite consisting of glassy crushed and heat-expanded rock from volcanic origin.

Cellulose consisting of fibrous light weight and ash less paper like medium.

Special ground wood is becoming popular in recent years since it is combustible and reduces the high cost

of disposal. There are nowadays manufacturers that grind, wash and classify special timber to

permeability's which can suit a wide range of applications.

Disinfection of water

The disinfection of water can be carried out by following methods:

Boiling Chlorination Aeration Removal of algae Ultraviolet rays ozonisation

WHAT IS DISINFECTION OF WATER??

Water disinfection means the removal, deactivation or killing of pathogenic microorganisms. Microorganisms are

destroyed or deactivated, resulting in termination of growth and reproduction. When microorganisms are not removed

from drinking water, drinking water usage will cause people to fall ill.

Sterilization is a process related to disinfection. However, during the sterilization process all present microorganisms

are killed, both harmful and harmless microorganisms.