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SOPA SANDAS: A design for pit type latrine

developed by Appasaheb Patwardhan. By

Dr. S. V. Mapuskar,

Appa Patwardhan Safai wa Paryawaran Tantraniketan, Dehu Village,Tal.Haveli,Dist.Pune,Maharashtra 412 109. INDIA 1. INTRODUCTION

During the Bhangi Mukti movement initiated by Mahatma Gandhi, a number of social as well as technical interventions were initiated by his followers. Appasaheb Patwardhan was the most notable person working for the technological aspects of sanitation interventions. He was the key person in the development of technical interventions.

2. SOPA SANDAS Sopa sandas was a significant innovation developed by Appasaheb Patwardhan in 1946 for the appropriate, hygienic and sustainable management of human excreta. From 1960s, Maharashtra Gandhi Smarak Nidhi has been propagating this design in Maharashtra. During the Mahatma Gandhi Birth Centenary year celebrations in 1969, this design was being propagated for use throughout India under the Hindi nomenclature of Sulabh Shauchalaya ( sopa sandaas, the original name in Marathi language was translated in Hindi).

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In this design, the human excreta is managed in the pits dug in the soil. The design comprises of toilet seats from where human excreta would flow by gravity, a little flush water and anal cleansing water to the pit. In the pit, human excreta would get biologically digested aerobically or facultative anaerobically into a solid compost which would remain in the pit as residual compost. The liquid and gaseous components resulting from biological digestion process would get leached out into the soil surrounding the pit. Two pits were included in the design to facilitate the continuous use of the toilet. For the change-over of the flow from one pit to other pit an intervening chamber was designed. In order to minimize the use of flush water, latrine pan slope was increased. 3. SALIENT FEATURES OF THE DESIGN: The design was developed by Appasaheb Patwardhan keeping in view the need for providing a simple, easily manageable, affordable, fertilizer producing, scavenger free latrine and appropriate for the rural ambient conditions and socio- behavioural aspect of the Indian rural population. This design has three basic features- a) Latrine pan with flap - The use of water seal trap for the pan is avoided. Instead, an automatically closing and opening hinged flap is used for preventing bad odour and insect movement where a hinge is provided at the top. The suspended flap opens during passage of excreta and water. After passage, the flap closes by its own weight, preventing any insect movement. However it allows inflow of air for ventilation. As the air flow is from pan to vent, any bad odour in latrine enclosure is avoided.

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. Design by Appasaheb Patwardhan Modified by Dr. Mapuskar b) Ventilation -Bad odour, mosquitoes and fly nuisance is taken care of by providing a ventilation from the latrine pan to pit and onward through a vent pipe provided in the system.

The toilet seat is provided with an automatically opening flap

at the lower end of the latrine pan. As a water seal trap was not provided for the pan, an innovative system of ventilation was provided. For this purpose, a vent pipe was provided over the pit. In the system, air ventilation is established from the latrine pan to pits and onwards to the vent pipe. The vent pipe is raised above the level of the latrine super structure. Thus the atmospheric air draft from wind establishes air flow from latrine pan to vent pipe and outside. This system avoids the smell in latrine super structure and the movement of insect like mosquitoes and flies from the toilet seat. The top end of the vent pipe is covered with a suitable net mesh to prevent insect movement without hampering the air movement.

c. Composting & excreta is done by pit. With the provisia time. When the p

g & pathogen kill - The treatmene by allowing natural composting provision of two pits, it is possible to the pit in use is full the faecal flow

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eatment of human ting process in the ble to use one pit at l flow is diverted to

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other pit. This allows adequate period for the completion of the composting process for the faecal content of the pit and to make the compost pathogen free.

4. CONSTRUCTION TECHNOLOGY: a) A toilet seat with enclosure of suitable dimensions is provided at an appropriate place. In the latrine floor, the latrine pan is provided for defecation. b) Latrine pan with flap - A latrine pan is provided with the slope of

about 30 degrees from the horizontal plane. This slope minimizes

the flushing water for downward movement of faeces. At the

posterior and lower end of the pan instead of water seal trap, a

flap cover hinged with the pan at the top, is provided so that the

chute opening is always kept closed by gravity pull.

c) At the back of the toilet seat, a chamber is provided. This

chamber is an inspection chamber constructed in such a way that

the flap of the pan remains accessible from the chamber. This

chamber also provides an access for the change over of flow of

excreta from the filled pit to the empty pit.

d) Adjacent to the chamber, two brick lined pits with honey

combing brick works are provided.

e) Two shorts lengths of 4 inch diameter pipe are provided for

linking the chamber to the pits.

f) In the earlier design, a single rectangular pit of 5 ½ ft x 3 ½ ft pit

inside dimensions, were constructed in 9 inch thick honey comb

brick work. This was divided into two compartments by

constructing a 6 inch thick wall in the center. This partition is

plastered in cement mortar from both the sides. Only a small vent

is fixed in this partition at the upper end.

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Subsequently as a rectangular shape was found to be

structurally more unstable and costly, in recent years, two

circular pits were constructed in 4 inch thick honey comb brick

work. However, users of ferrocement technology for the pits,

find rectangular shape to be more convenient.

g) Vent pipe - A.C. vent pipe of 4 inch diameter is provided

from the chamber or the pits reaching atleast 1 ½ feet above

the roof of the super structure. The upper end of the vent pipe

is covered with mesh net so as to prevent the movement of

insects like mosquitoes, flies etc.

h) The pits are covered with appropriate cover so that the smell

and insects are avoided.

i) Super structure - Any suitable super structure for privacy is

provided.

5. OPERATION AND MAINTENANCE:

In this design two pits are used alternately. The flow of

excreta and water is led to only one pit by blocking the pipe

from the inspection chamber. When the functioning pit is full,

the flow is diverted to the other pit by opening the inspection

chamber. The pipe leading to the full pit is simultaneously

blocked. The full pit is kept closed for 1 year so as to allow the

composting process and the pathogen kill. After a year, the

closed full pit is opened and the matured compost is removed

for use in agriculture. This compost is dry without any odour

and is hygienically safe.

If the pan flap has to be replaced, it can be done easily as it

is accessible from the chamber.

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The upper end of the vent pipe is to be kept covered with a

mesh netting which would prevent movement of mosquitoes,

flies, etc.

For proper functioning of the system, the use of water

should be minimized.

No anti-microbial should be used as a cleanser, as the use

of such materials will hamper the biodegradation process. Non

antimicrobials can be occasionally used. Simple water would

be the best cleansing material.