In conservancy system the human excreta is collected in various types of privies few of which are: 1. Pit Privy 2. Bore-Hole Privy 3. Cesspools 4. Concrete Vault Privy 5. Dug-Well Privy 6. Chemical Toilet 7. Removable Receptacle Privy 8. Aqua Privy.
Type # 1. Pit Privy:
This is very economical and requires no operation. Fig. 21.1 shows this type of improved privy. It essentially of a pit 1.3 x 1 m in plan and 1.5 to 2.8 m deep. At the top of this pit the squatting seat is provided in a compartment. The superstructure is of temporary nature. When the pit is filled, it is closed from the top by 60 cm thick earth layer and a new pit is excavated by the side of it.
The squatting pan along with the compartment is shifted to the new trench. A 10 cm diameter vent pipe is also provided to take the foul gases. If lime is applied frequently it will reduce the odours. Pit privy should be constructed 30 m away from the existing well in the nearby locality.
Type # 2. Bore-Hole Privy:
It is similar to pit privy, the only difference is that in place of a pit, it has long 40 cm diameter hole. The depth of the bore hole should be 100 cm less than the ground water table, so that the excreta may not pollute the ground water. The hole should be lined from inside. When the hole is filled up, it is covered by a thick layer of soil and another hole is dug by the side of it.
Fig. 21.2. shows the essentials of improved borehole privy in which the hole is provided by the side of the latrine compartment and is connected to the squatting seat by means of a trap. This improved type of privy will also avoid fly nuisance and odour.
Type # 3. Cesspools:
It essentially consists of a pit or chamber lined with dry bricks or stones as shown in Fig. 21.3. One cesspool can serve the function of more than one Building depending upon its capacity. The excremental matters flow through pipes from the water closets. When the cesspool is filled up, it is emptied and cleaned. The pumped materials are disposed of in a suitable manner.
Type # 4. Concrete Vault Privy:
ADVERTISEMENTS:
In previous soils and when water table is very close to the ground surface, it becomes difficult to construct borehole, pit or other types of privies, because the excremental matter will pollute the ground water. Under such circumstances concrete vault privy is most suitable.
Fig. 21.4. shows the essentials of concrete vault privy. It essentially consists of a watertight concrete vault constructed in the ground. Squatting pan with compartment is placed over the concrete vault as shown in Fig. 21.4.
When the vault is filled up, it is emptied and cleaned. To prevent bad odours daily after use soil should be thrown over the excreta. Squatting pan should be constructed in such a way that no water can enter the vault.
Type # 5. Dug-Well Privy:
It is similar to borehole privy only the difference is in the diameter of the hole. In dug well privy 75 x 75 x 360 cm pit is excavated which is lined with honey comb brick-work, to absorb the liquid wastes.
Type # 6. Chemical Toilet:
ADVERTISEMENTS:
This is the most satisfactory method of disposal of excreta without water carriage. In this privy a metal tank filled with concentrated solution of caustic soda is placed below the squatting seat. The excreta is totally sterilized and liquefied when it comes in contact of strong caustic soda. When the metal tank is filled up, it is cleaned and emptied. The effluent of chemical toilet is clear and free from any odour and can be easily disposed off.
Type # 7. Removable Receptacle Privy:
This is a cheap type of privy and is mostly used in India in unsewered town. It requires the services of sweeper for its daily cleaning, It essentially consists of a metal box placed below the squatting seat. The excreta is collected daily from this removable by sweeper. Fig. 21.5 shows this type of privy.
Type # 8. Aqua Privy:
Most of the privies described above are of temporary nature and shifted when the privy is tilled up with excreta. Therefore, they cannot be constructed as a permanent structure.
Aqua privy or wet latrine is an improved type of privy, which makes it possible to provide a permanent structure. Such types of privies are very convenient for factories, villages, hill stations etc. no doubt, they are more costly and require some attendance.
Fig. 21.6 shows the essentials of an aqua privy. It essentially consists of underground masonry chamber. Latrine pans enclosed inside small rooms are fixed the top of the masonry tank with the outlet ends dipped 8-10 cm in the liquid below. As the outlet ends of pans are dipped in water foul gases escape in the latrine rooms and no water is required for flushing it.
The extra directly goes in the masonry chamber and is digested anaerobically. One more chamber is also provided by the side of it, in which aerobic action takes place and the sewage is digested.
ADVERTISEMENTS:
The effluent from second chamber is allowed to pass through a filter tank as shown in Fig. 21.6. The final effluent is very clear and can be utilized for irrigating gardens or directly disposed of in nearby water courses. Aqua privies are most suitable for localities having no piped water supply, because very mall quantity of water is required for using it.