Environmental Engg.

Lesson-18 Importance of sanitation

Principles of sanitation

Following are some of the fundamental or rather ideal principles of sanitation which, if observed, result in better living conditions

Collection and conveyance

The basic principle of sanitation is to remove any waste matter as early as possible after its formation.  The earlier it is removed, the easier it becomes to render it harmless.  The waste matter may be in any of the three forms – solid, liquid or gas

Interior decoration

The interior decoration of the building should be done after giving a serious thinking.  The substances which are likely to catch dust should not be generally placed in room or if placed, arrangement should be made to clean them periodically

Orientation of building

In order to achieve natural ventilation, the orientation of building should be made to adjust with the prevailing natural conditions at site of construction of building.  The building should be so oriented with respect to the local climatic conditions that all the rooms are properly lighted naturally and that there is free circulation of fresh air.

Prevention of dampness

The construction of building should be damp proof.  The health of human body is considerably affected when there is presence of damp in the surroundings. The preventive measures to admit damp should invariably be taken to achieve proper sanitation of the building

Supply of water

There should be plentiful supply of pure water to the building.  The scarcity of water leads to the development of unhygienic conditions in the building

Treatment of water

All the waste matter received from the building should be disposed off only after giving proper treatment to it.  Thus the effluent from sewage plant should be thrown into natural river or stream after it has been made harmless.

Site for sewage treatment works

The site for treatment units sewage of any town should be carefully selected and the following aspects are to be considered at the time of its final selection

1. Good foundation soil should be available for various sewage treatment units to rest firmly on the ground and thus to grant the structural stability to them

2. The general slope of the site should neither be too steep nor too flat.  It will assist in placing various treatment units at such levels that sewage may flow from one unit to the other by gravity only

3. The general level of the site should be lowest level area of the town or city so that the sewage from the entire town or city can be collected and conveyed by gravity only

4. The location of site should be appropriate with respect to the method of sewage treatment to be adopted for the project

5. The location of site should be such that enough area is available nearby when it becomes necessary in future to expand the existing project.

6. The proximity of water course near the site or enough waste land for irrigation will be considered as an additional advantage.

7. The site should be safe from floods for all the time

8. The site should be situated on the leeward side of wind so that the undesirable odours will be prevented from entering the town or city

9. The site should not be, as far as possible, far away from the town or city

10. The subsoil water level at the site should remain low even during monsoon

Design aspects

Following aspects should be kept in mind while making design of the sewage treatment plant:

1. Every unit of the plant should have flexibility in control and operation

2. The design of the plant should be aimed at granting the safety of health of the personnel operating the plant

3. The major units of the plant should have bypass facilities which can be put into commission during emergency

4. The overall design of the plant should be such that there is easy accessibility for operating and maintaining valves, sampling points and various other operating devices.

5. There should be adequate alternative provisions in case the plant fails or is shut down for repairs or any other reason

6. There should be some alternative for operating of the plant when its outlet is submerged under high water.

7. The treatment plant should accommodate a full-fledged laboratory in which routine tests can be carried out for the performance of various units of the plant.

Some definitions

In order to simplify the understanding of the subject, the following five important definitions are mentioned at this stage

Bacteria

These are microscopic unicellular plants or organisms and for the study of sanitary engineering, they are divided into three groups, aerobic, anaerobic and facultative.

The aerobic bacteria require light and free oxygen for their existence and development

The anaerobic bacteria do not require light and free oxygen for their existence and development

The facultative bacteria can exist in presence or absence of oxygen but they grow in plenty in absence of air.

Invert

The lowermost level or surface of a sewer is known as the invert and in the construction of sewers, the invert levels are to be carefully checked for the proper functioning of the sewer line.

Refuse

The term refuse is used to indicate what is rejected or left as worthless and for the study of sanitary engineering, it is divided into five categories:

Garbage

The term garbage is used to indicate dry refuse and it includes decayed fruits, grass, leaves, paper pieces, sweepings, vegetables, etc.

Sewage

The term sewage is used to indicate the liquid waste from the community and it includes sullage, discharge from latrines, urinals, stables, etc., industrial water and storm water.  The term night soil is sometimes used to indicate the human and animal excreta.

Storm water

The term storm water is used to indicate the rain water of the locality

Subsoil water

This indicates the ground water which finds its entry into sewers through leaks.

Sullage

The term sullage is used to indicate the wastewater from bath rooms, kitchens, etc.  It is merely waste water and does not create bad smell.

Sewer

The underground conduits or drains through which sewage is conveyed are known as sewers.

Sewerage

The entire science of collecting and carrying sewage by water carriage system through sewers is known as sewerage and the sewage thus collected and conveyed is taken to a suitable place for its disposal.