Sustainability and Appropriate Latrine Designs Some Notes

8/3/2019 Sustainability and Appropriate Latrine Designs Some Notes

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Sustainability and appropriate latrine designs-Some Notes

By Dr.S.V.Mapuskar

Appa Patwardhan Safai w Paryawaran Tantraniketan

Dehugaon, Tal: Haveli, Dist: Pune, Maharashtra-412109

SUSTAINABILITY CRITERIA

Sanitation is explained in dictionary as adoption of measures to eliminate unhealthy

elements especially with regards to dirt and infections. Thus, adoption of these measures, a

sanitation system, could be considered as comprising the uses of all parts of the system,along with collection, transport and treatment of human excreta, grey water, solid waste,

industrial waste water and storm water and the management of resulting and products.

This recognizes sanitation as being multi faceted and includes social, economical andlogistical side along with the resource management.

Thus, for sustainability, a holistic decision making process for sanitary provision isneeded.

Therefore a sustainable sanitary system should1. protect and promote human health

2. Should not contribute to environmental degradation or depletion of the resource base.

3. should be technically and institutionally appropriate4. should be economically viable

5. should be socially acceptableThe basic or core consideration for sustainability criteria may be drawn up on this basis.

As seen above, sanitation provision is multifaceted with following important criteria

for sustainability

I) Health1. Risk of infection

2. Risk of exposure to hazardous substances

II) Environmental

1. Use of natural resources for facility2. Use of land for facility

3. Use of energy for facility

4. Construction material

5. Chemical6. Fresh water

7. Discharge to water bodies

8. Discharge of hazardous substances9. Air emissions

10. Contribution to global warming


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11. Odour

12. Resource recovery

III) Economic1. Costs-capital

2. Costs- operation and maintenance3. Capacity to pay- by user

IV) Sociocultural1. Willingness to pay

2. Convenience (Comfort, smell, noise, privacy, adaptability etc.)

3. Responsibility distribution

4. Acceptable for use and maintenance5. Awareness and information needs.

V) Technical

1. System robustness2. Robustness in use

3. Local competence for construction4. Local competence for O & M

5. Durability

6. Complexity of construction and O & M

7. Flexibility to user needs and environmental conditions.

PROMOTION OF SANITATION

With these sustainability criteria in mind promotion of sanitation may involvefollowing important aspects for implementation

1. Involvement and participation of community in planning and implementation2. Creation of Felt-need through awareness building and education

3. Low cost appropriate technologies using local skills

4. integration with other development activities5. Comprehensive sanitation programme planning

6. Well planned implementation strategy

SELECTION OF APPROPRIATE TECHNOLOGY

In this paper we shall restrict our attention to mainly technological aspects of

sanitation facilities which would in the long run be sustainable.

In nature, nothing is a waste. Matter only changes form. Thus, waste is wealth.

This is an important concept for selection of appropriate technology for management of

waste.


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Based on criteria for sustainability, some important parameters for selection ofappropriate technology may be

1. Disease prevention2. Environment friendly methods

3. Maximum population coverage from low income urban, periurban and rural

population4. On site to avoid transportation

5. Economic viability

6. Low capital and O & M cost

7. Financial benefits from resource recovery and recycling8. Energy recovery

9. Production of fertilizers as end product

10. Suitability for levels of local skills available for installation and maintenance

SUITABILITY OF THE TREATMENT PROCESS

In India (for that matter, in tropical countries) natural biodegradation process

is most suitable and appropriate for biodegradable waste, while recycling and

reuse would be desirable for most of the non biodegradable waste. In nature, twobiodegradation processes take place 1) Aerobic, where microbes degrade the

substrate in presence of air, 2) Anaerobic, where microbes degrade the substrate

in absence of air. Both these processes can be On site or Off site.

HUMAN EXCRETA MANAGEMENT

Human excreta management gets priority in sanitation programme as itsimproper management is a major cause for illnesses in the community.

Appropriate technology selection for human excreta management will have tobe especially based on sustainability criteria and appropriate technology selection

parameters discussed above.


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Selection of Technology

Can community Latrines be the solution? Probably not! Community Latrine isNo bodys baby. As such, its O & M is always problematic. Therefore, latrine

construction programme needs to be focused on individual families. The basic norm

may be Each family should understand its own responsibility to manage its ownwaste and should adopt necessary measures accordingly.

What comprises a Latrine? It has two components. One is where humanexcreta is managed and treated. Other is a superstructure. First component is most

important. It has to be constructed properly from health and sustainability points of

view. Superstructure can be adjusted to suit mainly financial requirements.

Minimum requirements for such a Latrine can be as follows-

1. Prevent spread of infection2. Ecofriendly

3. Low cost

4. Easy for construction5. Suitable for soil and climate

6. Odourless

7. Aesthetically good8. Harmless to water sources

9. Faeces inaccessible to insects and animals

10. Keeping soil surface clean

11. Easy for maintenance12. Produce fertilizer


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Several technologies are at present available. Some of them are aerobic digestion

based, some are anaerobic digestion based.

AEROBIC DIGESTION BASED

POUR FLUSH TWO PIT LATRINE TECHNOLOGY

In most parts of India, pour flush two pit latrine with offset pits has been

found to be suitable. In this design water seal trap and pan are used.

Two pit pour flush latrine design


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In this design the shape of pit is shown as circular. Structurally circular pits are

more stable than rectangular pits. Hence circular shape (hollow cylindrical) should

always be preferred.

Preferable shape of pit circular and not rectangular

Sizing of the pit is an important issue. Following parameters may be kept in mind

for sizing of latrine leach pits.

1. Manurial residue per person per year is to 1 cubic foot

2. One toilet seat for maximum 20 persons3. For digestive process availability of air from soil is up to a depth of 4 feet.

4. A period of one year is necessary for pathogen kill in the pit.

5. Distance between two pits may be about 3 feet. so that the maturing manure in

closed pit would be dry and pathogen free.

Thus, for an average latrine the pit may have a depth of 4 feet and a diameter of 3 feet.This

pit will last for about five yrs. for a family of five persons.

Two pits will be used alternately, so that manure from full pit can be emptied after one

year,when it will be pathogen free.


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.

Methodology of construction of leach pit

For leach pit work, honey combing is done.. 6 to 8 holes of 2 inches width are kept in

alternate layers of brick work. In top 1 1/4 foot holes are not kept.

Inlet pipe coming to pit is usually accommodated in upper one foot. Chamber

intervenes between the toilet seat and the pit. The pipe from chamber to pit is given a slope

of 1 ft. in 10 ft. length. The plinth of the seat is usually kept one foot higher than the top ofthe pit.


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Difference in levels of pit top and plinth top indicating gradient for pipe slope


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Appropriate Rural pan and trap

For minimizing the use of flushing water, a pan with high gradient and trap with low water

seal height are used. The sloping surface of the pan has an angle of 25 to 30 with thehorizontal plane, while the water seal trap has a waterseal with 20 mm height. This reduces

required quantity of flushing water to about one to two liters of water.

Comparison of urban and rural pan indicating angle of slope with

horizontal plane


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20mm. height waterseal trap


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Important points to be remembered during construction

Some important points to be noted during construction of pour flush two pit latrine are asfollows-

1. Pit should be circular. The inner dia of pit may be about 3 ft., depth of pit should be

about 4 ft.2. Pit wall construction should be raised 3 inches above ground level.

3. Two pits to have intervening distance of 3 ft.

4. Pipeline from the pan to the pit should have a gradient pf 1:10 that is 1 ft. drop for10 ft.

5. Top of the plinth should be 9 inches to 12 inches above the level of top of the pit

6. Bottom of the trap should be about 18 inches from the top of the plinth. However, this

will depend on the total height of pan placed over the trap.7. Surface in the chamber should be rounded off and polished with near cement. Turn in

the chamber should be Y shaped.

8. Latrine pan floor should have around 25 to 30 angle with the horizontal plane.

9. Trap should have 20 mm. water seal.10. Internal dia of pipe from chamber to pit should be about 100 mm. or 4 inches

11. Rear edge of pan should be 6 inches to 8 inches from the rear wall.12. Seat floor should be sloping gradually towards the pan and should be finished in neat

cement.

13. Foot rests should be rectangular. The distance between two foot rests may be around

10 inches14. Cement stuck up on the inside surface of pan and trap should be thoroughly cleaned

and the surface should be made smooth.

Operation and maintenance guidelines

Some important observation and maintenance guidelines for the user families may

be-1. Moisten the pan a little before use. This will reduce water required for

flushing.

2. Use only water for cleaning seat. Do not use disinfectant or antiseptic.3. Do not use excessive water.

4. When one pit is full, change the flow to second pit by opening chamber.

5. Keep the full pit closed for one year. Open it after one year and remove the

fertilizer residue.6. In case of blockage in trap, open the chamber also and remove the blockage

by working from both sides of trap.

After manure is matured, the pit can be opened and manure can be removed by the

owner himself very easily. No outside help is required. Masons help may be required only

for closing the pit again. The manure can be used on the agricultural land as fertilizer.


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ANAEROBIC BIODEGRADATION PROCESSES SEPTIC TANK

Septic tank is not a preferred option. However, if it is constructed, it should be

constructed with correct design. It should have volume of 45 days HRT. Further, effluentshould be managed in a leach pit. It should not be allowed to flow in open or in surface

drain. Top of its vent pipe should be covered with nylon mesh to prevent entry of

mosquitoes and flies

Design of septic tankHRT TO BE 45 DAYS


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ANAEROBIC BIODEGRADATION PROCESS-BIOGAS PLANT

Biogas plant is a preferred option if anaerobic biodegradation is to be used,

Floating dome water jacketed biogas plant

Fixed dome Malaprabha Biogas plant

Generally two designs. 1. Floating dome water jacketed biogas plant 2. Fixed dome

Malaprabha biogas plant are two preferred designs. These plants should have 45 days HRT.


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Sustainability and Appropriate Latrine Designs Some Notes

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