From the feces, disease agent can be transmitted to the host through five channels: 1. Food 2. Flies 3. Fingers 4.Water 5. Soil. Sanitation barrier is a barrier which is imposed between feces and all these five channels. So the disease agent cannot be transmitted to the host through these channels. Sanitation barrier can be effectively provided in the form of sanitary latrine.
Criteria for a sanitary latrine
1. Excreta should not contaminate the ground or surface water.
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2. Excreta should not pollute the soil.
3. Excreta should not be accessible to flies, rodents or animals.
4. Excreta should not create bad odor or ugly appearance.
Disposal of excreta
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Excreta can be disposed by a variety of latrines. These latrines are classified as:
1. Service type (Conservancy system): Bucket latrine
2. Non-service type (Sanitary latrines) Bore hole latrine
Dug well latrine Water seal latrine
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1. Bucket latrine:
It is a service type (conservancy system) of latrine. These latrines contain a bucket from which night soil is removed by human agency. Disadvantages of this type are: a. exposure to flies b. soil and water contamination c. buckets need frequent replacement d. adequate staff needed for collection
2. Bore hole latrine:
It consists of a circular hole of about 16 inches in diameter dug into the ground to a depth of 20 feet. A concrete squatting place with a central opening and foot plate is placed over the hole. A suitable enclosure is put up for privacy. This type of latrine is useful for a family of 5 of 6 people for about one year.
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3. Dug well latrine:
It is an improvement over bore-hole latrine. It consists of a circular pit of 30 inches diameter and 10 to 12 feet deep. This pit is lined with pottery rings. A concrete squatting plate is placed on the top of the pit. The latrine is enclosed within a suitable structure for privacy. This type of latrine may serve for 5 years.
Water seal latrine
It is an improved form of sanitary latrine. Two types are available: 1. PRAI type (evolved by Planning Research and Action Institute of Lucknow) 2. RCA type (designed by Research-cum-Action Projects in environmental sanitation of Health Ministry). Of these two, RCA type is most popular.
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Parts of RCA type
The essential parts of RCA type of water seal latrine are: 1. Squatting plate with pan 2. Trap 3. Connecting pipe 4. Dug well pit 5. Superstructure.
1. Squatting plate with pan: The size of squatting plate is 3feet x 3feet. It contains raised foot rests and a pan which receives feces urine and wash water.
2. Trap: It is a bent pipe of about 3 inches in diameter and it is connected to the pan. The trap contains water and acts as a water seal. Water seal is the distance between the level of water in the trap and the lowest point in the concave surface of the trap. It is usually about – inch. The water seal prevents access to flies and also suppresses bad odor.
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3. , Connecting pipe: The trap is connected to the dug well pipe
by means of a connecting pipe. It is 3 inches in diameter and 3 feet in length with a bend at the end.
4. Dug well pit: It is 30 inches in diameter and 10 to 12 feet deep. When one pit is full another one may be dug.
5. Super structure: It provides both privacy and shelter.
Advantages of water seal latrine
i. It prevents access to flies
ii. It prevents the escape of foul odor and gases
iii. It requires minimum use of water.