Septic Tank, It’s Principle and Guidelines

Public sewerage system is not laid at some places or in houses located in isolated areas which can not be connected with public sewer system economically. In this situation the waste of the house can be disposed off through individual disposal system such as septic tank or soak pit etc. Septic tank has limitations and will provide unsatisfactory quality of the effluent and also faces difficulty for providing proper disposal system of the effluent. The septic tank is recommended for small communities where population does not exceed 300. 

Working Principle        

Sewage and waste of the house come into septic tank and solid matters settle down at the bottom of the tank. Anaerobic Bacteria convert the sewage into liquid and gases during the process of digestion. In this way there is appreciable reduction in the volume of waste and it changes into semi solid condition, which is called sludge. It is necessary that septic tank is covered with water tight top roof slab. Septic tanks are generally constructed in brick masonry.
       
Guidelines for Septic Tank

1. Sufficient water is required for proper functioning of septic tank.
2. The waste containing detergent should be avoided in septic tank as it had adverse effect on anaerobic bacteria.
3. Septic tank should have minimum width of 0.75 meter and minimum depth of 1 meter below water level of the septic tank.
4. Length of the tank should be 2 to 4 times the width.
5. Every septic tank should be provided with ventilation pipe of at least 50 mm diameter.
6. Minimum free board above water level should be of 30 cm.
7. The floor of the tank should be of cement concrete 1:1.5:3 and has a minimum slope 1 in 10 provided towards the sludge outlet to facilitate de-sludging. 
8. The inner surface of septic tank should be plastered with rich cement.
9. For efficient working of septic tank the sludge should be cleaned half yearly or yearly.