Malaprabha Biogas Plant developed by Dr S V Mapuskar

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Recycle Human Waste

For Health, Wealth and Energy

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MALAPRABHA

BIOGAS PLANT

Developed By

Dr. S. V. Mapuskar

******************************************

NEW DESIGN FOR

RECOVERY OF BIOGAS FROM

LATRINE

Published by

Jyotsna Arogya Prabodhan,

Dehu village, Tal. Haveli,

Dist. Pune, Maharashtra 412 109

INDIA

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Copy right

Dr. S. V. Mapuskar,

Dehu village, Tal. Haveli,

Dist. Pune, Maharashtra 412 109

INDIA

Published – June 1988

Updated: November 2011

For Private circulation only

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Recycle Human Waste

For Health, Wealth and Energy

***************************************

MALAPRABHA

BIOGAS PLANT

Developed By

Dr. S. V. Mapuskar

***************************************

NEW DESIGN FOR

RECOVERY OF BIOGAS FROM

LATRINE

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CONTENTS

Sr. No. Particulars Page No.

1. Development of Nightsoil 4

Based Biogas Plants

2. Introduction To Malaprabha 12

3. Basis Of The Design 14

4. Design Calculations 18

5. Construction Work 24

6. Field Implementation of the design 32

ANNEXURES

1. Material Estimates 34

2. Labour Component Estimates 37

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Chapter 1:- Development of Night Soil

Based Biogas Plant

In India, biogas technology is in use very effectively for

nearly five decades. Curiously, one of the first few biogas

plants in the world which was constructed at Leprosy Home at

Wadala in Bombay in about 1901, worked on sewage.

Subsequently, in 1937, biogas generation was undertaken at

Dadar Sewage works at Bombay, again, during the treatment of

sewage sludge.

Unfortunately, for the last several years, it is being

presumed at various levels, that cattle dung is the only

appropriate feed for the biogas plant. This presumption received

a further boost, because the biogas plants in India were and are

still known by people as ‘Gobar Gas Plant.’ This name has been

an unfortunate nomenclature in the development of biogas

technology in this country, as it gave rise to the impression that

gas is possible only from Gobar (cattle dung).

We are aware that biogas is generated during the

anaerobic digestion of any naturally produced dead organic

matter. It is now high time that we start working more

vigorously on the use of organic feeds (which are at present a

wasted resource) other than cattle dung for biogas generation.

The earlier we do it, the better it will be.

The review of the cattle population in India gives some

interesting findings. Only about 15% families in the country

own 2 or more cattle heads. Therefore, it becomes obvious, that,

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hardly about 10% population in the country (if all are ideally

covered) can manage to run biogas plants. If biogas technology

remains restricted to cattle dung feed, only the rich farmers will

benefit from the biogas technology. The poor and weaker

sections of the society will remain deprived from the benefits of

biogas.

We can take the benefits of biogas technology to these

deprived people only if, we are able to use alternative feeds

(other than cattle dung) for the production of biogas. Further, it

is also necessary to think in terms of establishing community

biogas production facilities.

When we think in terms of use of alternative feeds, the

existing technology has to be modified to suit the alternative

feeds. Unfortunately, the technology in use for cattle dung feed

was used in toto for other feeds also. This resulted in several

problems. As a result, in many cases, the use of alternative

feeds was abandoned. This is a negative approach. To take a

more positive view, the parameters, the design criteria and

characteristics of the feed will have to be considered as a

package.

Many such alternative feeds are available. At present,

most of them are treated as an organic waste, a nuisance and

hazard. The biogas programme could be easily extended to a

wider section of population, if these alternative feeds are tapped

imaginatively and adequately.

Human nightsoil is one such alternative feed. At present,

human nightsoil treatment is a major sanitation problem in the

country. It is a major source of pollution, health hazard and

social injustice. It has become a nuisance to rural and urban

environment. Its effective treatment is becoming unmanageable.

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If it is used imaginatively in biogas plant, it can become an asset

instead of a nuisance.

Realizing the importance of proper nightsoil disposal in

rural India, Mahatma Gandhi included it in his ‘gramsafai’ and

village upliftment programme. Sanitary disposal of nightsoil

was visualized to serve fold three purpose, viz. 1. emancipation

of scavenger community (Bhangi Mukti), 2. clean villages

(gram safai) and 3. production of manure (Khad nirmiti).

Proper treatment of human waste (Nightsoil) is an

essential requirement for better village sanitation and promotion

of health, with the ultimate objective of ‘Health for all.’

Recycled imaginatively, it can also partially meet the energy and

fertilizer needs of the country. Thus, the waste can turn into

wealth.

‘On site’ nightsoil treatment methods are very

satisfactory in developing countries as they obviate the process

of manual lifting, carriage and occasional spilling of faeces.

The aqua privy or septic tank latrines (an ‘on site’ disposal

method) which are essentially anaerobic digestion processes, are

increasingly being constructed in the country. Human nightsoil,

being a naturally occurring organic material, emits methane

containing gas (i.e. biogas, which is an asset, not a nuisance)

during anaerobic digestion in the septic tank. Unfortunately, no

attention is given to this component, while promoting the

construction of latrines. The gas emitted from these latrines is

considered as a ‘nuisance gas’ and is let off through as high a

vent as possible, polluting the air and depleting ozone layer.

Late Appasaheb Patwardhan took up human nightsoil

treatment this activity as a mission for his life. He worked

feverishly, since 1928, on the problem of nightsoil disposal,

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devising in the process, several innovative designs for latrines

such as ‘Sopa Sandas’ (simple latrine), Gopuri latrine etc. and

subsequently biogas plants.

The technological design for a biogas plant to be used

for nightsoil feed must be suitable for the characteristics of

human nightsoil. In the initial stages, the design which was

found to be suitable for cattle dung was used for human

nightsoil without any change. Human nightsoil has physical,

chemical and microbial characteristics which markedly differ

from those of cattle dung. Therefore, the parameters, design

criteria etc. fixed for cattle dung biogas plants are not valid for

human nightsoil.

Late Appasaheb Patwardhan a dedicated Gandhian

worker, pioneered nightsoil based biogas plants in India, with

the construction of the first nightsoil based biogas plant at

Kankavli in Ratnagiri district of Maharashtra in 1953.

It was based on ‘Gramlaxmi’ design developed by Shri.

Jasbhai Patel in 1951 (which was adopted for propagation by

KVIC since 1962). Appasaheb Patwardhan worked further on

‘Gram laxmi’ design and modified this design for the use of

human nightsoil as a feed.

The design which he devised, was a water jacketed

digester with a floating dome gas holder. He termed it ‘water

jacket gas plant’ later called as ‘Gramgaurav gas plant’. This is

the design which is now known as ‘Floating Dome Water

Jacketed Digester’ design. Subsequently he constructed many

such plants throughout the country, creating a cadre of trained

social workers in the process.

The feasibility of ‘on site’ treatment of nightsoil in a

biogas plant was effectively demonstrated by him. He was a

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visionary, quite ahead of his times. He constructed the first

nightsoil based biogas plant in India, at a girls’ hostel in

Kankavli.

The plant receives nightsoil directly via pipes (no

manual handling and exposure of nightsoil) from four adjacent

latrines which are being used by the inmates of the hostel. The

biogas is being used in the kitchen. The effluent slurry is being

used as a fertilizer for plantation.

The original plant at Kankavli still continues to function

satisfactorily even after nearly 35 years. This fact speaks

effectively for the suitability of the design and for the feasibility

of biogas generation from nightsoil.

Appasaheb Patwardhan, in his capacity as Chairman of

Bhangi Mukti Samiti of Gandhi Smarak Nidhi, tried to

popularize nightsoil fed biogas plants throughout the country

and also arranged for the subsidy to be paid by Gandhi Smarak

Nidhi headquarters in New Delhi.

After the biogas programme was taken up by D N E S, it

has given a positive boost for the propagation of nightsoil based

biogas plants.

In 1981, Dr. S. V. Mapuskar developed an innovative

design ‘MALAPRABHA BIOGAS PLANT’ for recovering

biogas from anaerobically digested human nightsoil. While

developing this design, he had taken into consideration the

relevant hygiene factors along with the parameters for

biomethanation of human nightsoil. The relevant social factors

and convenient latrine use also were considered.

These parameters could be enumerated as follows:

• There should not be any direct handling of nightsoil,

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• Undigested nightsoil should not get exposed to

surroundings and should be inaccessible to insects and

animals,

• Aesthetically there should be freedom from odour and

unsightly conditions,

• There should not be any contamination of subsoil or

surface water,

• Surface soil should not get contaminated,

• Maintenance of the treatment process should be easy and

should not evoke any repulsive feelings,

• The recycling should give maximum possible

advantages,

• The social and behavioural aspects need to be tackled by

educational process.

Taking all the abovementioned parameters into

consideration, it is felt that for human nightsoil biomethanation,

only two designs are suitable:-

1. Floating dome water jacketed biogas plant developed by

Shri S.P. alias Appasaheb Patwardhan in 1953.

2. Fixed dome ‘Malaprabha Biogas Plant’ developed by Dr.

S.V. Mapuskar in 1981.

Malaprabha biogas plant has a cubical shape and hence

can be installed even inside the house. Latrine seat can be

installed above the biogas plant, minimizing the land

requirement. It is very easy for operation and maintenance. As a

result the design has been accepted widely.

Since 1981, hundreds of Malaprabha biogas plants have

been constructed. The results are very good. The plants have

been designed from 1 CuM capacity to 30 CuM capacity.

In Dehu village nearly 80 Malaprabha plants, working on

human nightsoil are functioning satisfactorily. Dehu is probably

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the only village in India which has such a large number of

functioning nightsoil based biogas plants.

In the following pages ‘Malaprabha Biogas Plant’ design

is described.

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Chapter 2: Introduction to ‘Malaprabha’

Any naturally grown dead organic matter generates

biogas after anaerobic digestion. However, so far, the stress has

been on using cattle dung as main feed material for the biogas

plant.

During the past few years, there has been a distinct

change in this attitude. The presently available designs were

designed mainly for the cattle dung feed. These designs may

not be the optimized designs for other feeds. Hence, the designs

need to be evolved so that the optimum conditions are created

for the utilization of these feeds within the right parameters.

Now the efforts are being made to decide on the parameters

which would be suitable for the use of feed materials other than

cattle dung.

Human nightsoil is one of the important and readily

available feed materials for biogas generation. The biogas

programme could be given an additional boost if the human

faeces are utilized for the biogas generation.

However, for the use of human night soil feed and for

the efficient functioning of human night soil based biogas plant,

the parameters and the design criteria as regards the procedures

for the feeding and handling the feed, the physical and chemical

characteristics of the feed, the movement of slurry, odour,

aesthetics, etc. need to be considered so as to create optimum

conditions for the use of human nightsoil. Further, from health

point of view, it will be necessary to see that the raw human

nightsoil is not exposed to environment, insects, animals etc.

and is not manually handled. During the digestion process, it

should not be exposed to environment. Further, the most

important parameter from health point of view will be the extent

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of pathogen kill or pathogen inactivation achieved, during the

process so that the effluent is not pathogenic.

It may be necessary to accommodate such a biogas plant

in close proximity of the residence, perhaps in the house itself.

Thus, it may be desirably suitable for the space constraints and

the conventional cubical format of house construction. Further,

the cost of the unit and the space requirement could be

minimized if the biogas plant and the toilet seat are made into an

integrated unit where the toilet seat is superimposed on the

biogas plant, although offset toilet seat may be a requirement in

some situations.

Keeping these factors in mind, a new design specially

suitable for the human nightsoil has been evolved, by Dr. S. V.

Mapuskar, in 1980. After watching the performance for five

years, the design was presented at national conference on

‘Biogas from Human Waste’ organized by ‘CORT’ at New

Delhi from 22nd

Aug. 1985 to 23rd

Aug. 1985.

It is named as ‘MALAPRABHA BIOGAS PLANT. It

could be classified as a fixed dome biogas plant.

With a little modification, it can also be used for other

feeds.

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Chapter 3: BASIS OF THE DESIGN

As stated earlier, the basis for the biogas plant

functioning on human nightsoil will necessarily differ from that

for the cattle dung based biogas plant.

Number of studies has already been done throughout the

world on the anaerobic digestion of human nightsoil. These

studies have been in the context of a human nightsoil disposal

system and not as a biogas generation system. However, since

these studies are for anaerobic digestion, such available data was

taken into consideration while developing this design.

1. Pathogenicity - The destruction or inactivation of the

pathogens will be a very important criterion for the biogas

system working on human nightsoil. The human faeces contain

various species of viruses, bacteria, protozoa as well as the

vegetative forms and ova of helminthes. It has been reported

that, for the inactivation and/or destruction of viruses, bacteria

and protozoa, a maximum period of about 45 days of anaerobic

digestion is necessary. Helminthes ova are not destructed in

anaerobic condition. However, they either float at the top or

sink to the bottom (depending on the species) in the digester.

Hence, in ‘Malaprabha’ design, the care has been taken to see

that the top and the bottom layers of the slurry do not flow

onwards and do not get in to the effluent. Thus, these ova are

retained in the plant and end in a natural death or inactivation

over a period of about two years. Thus, the effluent coming out

from the biogas plant of this design will be free from active

viable pathogens.

2. Direction of slurry flow - In biogas generation systems,

because of the buoyancy due to gas bubbles attached to slurry

particles and some other factors, there is a vertical up and down

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movement in the slurry. However, the slurry getting in from the

inlet tends to push the digesting slurry in the digester towards

the outlet. It would be desirable not to have these two

movements in the same direction. It would be better if inlet to

outlet movement is horizontally directed. This sort of a

movement would be more akin to horizontal plug flow type of

movement. In this design, it has been arranged that the

movement of the slurry from inlet to outlet is in horizontal

direction.

The consistency and the physical characteristics of

human night soil are such that the diluted digesting slurry gets

stratified into three layers. The lighter material floats as a

suspension in upper ⅓rd portion. The heavier component settles

down in the lower ⅓rd portion. During the digestion process,

these materials tend to move up and down in vertical direction,

depending upon the attached gas bubbles, specific gravity etc.

However, the middle ⅓rd portion is found to be relatively free

from solids. Hence, in this design, care has been taken to see

that the horizontally forward movement of the digesting slurry is

from the middle ⅓rd portion. This more or less simulates the

plug flow pattern in horizontal direction, mainly from the

middle ⅓rd portion. The plant is designed to have three

horizontally interconnected chambers. This mode of movement

ensures that there is no short circuiting of incoming raw slurry.

Incidentally, slurry inlet and outlet pipes also serve as small

additional chambers regulating the flow.

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3. Solid Content & Digester Volume - Available data shows

that for anaerobic digestion of human nightsoil, the optimum

solid contents need to be around 3% to 4 %, the variation being

between 2% to 5%. The fresh night soil has a solid content of

about 25%, varying between 20% to 30%. In Indians, the

average weight of fresh night soil per person/day is around 300

gm. It has been shown that the use of about 2·17 liters of water

per person/day would give an optimum solid content required

for the anaerobic digestion of slurry. Hence, this volume has

been taken as a basis for calculating the digester volume.

It has been noted that human nightsoil yields about 35 to

40 litres of biogas per person/day. Therefore, for getting 1 CuM

of biogas per day, it would be necessary to feed the night soil of

about 25 persons/day.

Thus, for a biogas plant having a capacity of producing

one CuM. Biogas per day, the digester volume should be

sufficient to accommodate the night soil of 25 persons per day

with input volume of 2·17 litres per person per day. Further,

the expected retention period required for the pathogen kill has

been taken as 45 days. This basis has been used for the

calculation of digester volume.

4. Scum Breaking & Allowance for Sedimentation – During

the digestion of slurry, the lighter solids will tend to form a

scum which will hamper the gas accumulation at the top. In

order to avoid this, a scum breaking arrangement has been

incorporated. This device consists of horizontally fixed PVC

pipe grid attached to the inlet pipe at a distance of 300mm from

the top. Every time the slurry moves up and down, this device

automatically breaks the scum accumulating on the top of the

slurry.

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In order to prevent the helminth ova from escaping to the

second chamber, a very simple arrangement has been made at

the bottom. The displacement window between the first and

second chamber is partially closed at the bottom by placing

loose bricks up to height of 225 mm from the bottom. While

desludging the plant, these bricks can be removed so as to

facilitate the removal of the settled nondigestible sludge from

the first chamber.

5. Slurry Inlet Pipe – A 100 mm Dia. PVC pipe is embedded in

the R.C.C roof of the first chamber, with the help of M. S.

flanges and anchoring bolts, the pipe projecting in the chamber

to a depth of 700 mm from the roof. This ensures that the gas

does not escape through the inlet.

6. Gas Storage & Gas Outlet – The roof of the digester

chamber and the sides of the digester chamber are rendered gas

proof by cement plastering and by gas proofing treatment. Thus

the upper portion of the digestion chamber serves as a gas

storage space.

Gas outlet is fixed in the roof of the digester by

embedding it in R.C.C. roof with the help of flanges and

anchoring bolts. In order to avoid the blockage by the scum, the

diameter of gas outlet pipe is kept at 75 mm.

The continuously generating biogas will keep on

accumulating in the upper portion of the digestion chamber by

pushing the corresponding amount of slurry towards the second

chamber (Displacement chamber). As the slurry outlet level in

the third chamber is at the level of the top of the digestion

chamber, the accumulating gas in the digestion chamber will be

stored at a pressure exerted by the slurry column in the second

and third chambers which will be at a higher level than the

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slurry level in the digestion chamber. (This action is similar to

the action in the other fixed dome designs.) The pressure on the

gas will vary between 0 to 30 cm water column.

7. Slurry Outlet Position – Slurry outlet pipe is placed in the

third chamber at the level of the roof of the digestion chamber.

Thus, when there is no gas in the gas storage space, the slurry

levels in all the three chambers will be at the outlet level.

8. Structural Provisions to Prevent Gas Leakage – As stated

earlier, the roof of the first chamber is cast in R.C.C., in which

the slurry inlet pipe and gas outlet pipe are embedded with the

help of M. S. flanges and anchoring bolts. PVC pipes are used.

In order to avoid the lifting of the edges of the slab, a brickwork

load is given on the edges of the slab. Also, anchoring for the

slab is provided in the top layer of the brickwork supporting the

slab. In order to minimize the stresses at the corners and joints,

the corners are rounded off with cement mortar plaster, thus

diverting the stresses. The joints between the brickwork and the

slab as well as slab and pipes are also rounded off in a similar

way.

9. Toilet Seats – As stated earlier, the toilet seat is placed on top

of the digestion chamber using load brickwork as a plinth. The

latrine pan is connected to the inlet pipe through the water seal

trap via inspection chamber.

If desired toilet seat may be placed off site. However, it

will increase the construction cost to that extent.

As it is necessary to restrict the use of water to about

2·17 litres per person, the water seal trap with only 20 mm water

seal is used. With this type of water seal, only 1·5 liters of

water is sufficient for flushing. Automatic flushing cistern is not

20

provided. If the situation demands, automatic flushing system

with low volume controlled flushing, can be used. Because of

the provision of water seal, there is no smell or odour from inlet

pipe. Further, the insects do not find an access to the system.

Some gases are likely to emanate from the inlet pipe. A

vent is provided for these gases. This vent also ensures that the

water seal is not disturbed by the negative pressure. An

inspection chamber provided between inlet pipe and the water

seal trap allows for the cleaning and maintenance of water seal

trap and inlet pipe whenever necessary.

The second and third chambers are completely covered.

Some gases are likely to accumulate in second and third

chambers. For these gases also a vent is provided. This vent is

combined with the vent from inlet chamber and a common vent

is taken above the roof of the latrine. Thus the system becomes

totally odourless.

10. Maintenance – The required routine maintenance is

minimal. Inspection chambers at inlet and outlet provide an

easy access for occasional cleaning. In this system it is not

necessary to manually handle the night soil. Once the night soil

gets past the water seal trap under the seat, it is not exposed to

environment anywhere in the system. After total digestion, the

end product in the form of harmless digested slurry comes out

from the slurry outlet.

Thus, in this design all the important requirements for

the biogas generation and hygienic requirements for human

night soil management are taken care of.

11. Safety – In comparison to LPG, biogas contains a mixture of

mainly methane and carbon-dioxide which is under very low

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pressure ranging between 0 to 40cms water column. Further,

methane is not explosive, unless it is mixed with air and is under

very high pressure. Therefore, the biogas plant is very safe.

Further, in case, because of non use, more gas is stored in the

gas storage space, the pressure will never exceed 40 cms of

water column. It is because after the maximum storage space is

occupied, the excess gas escapes through inlet pipe and further

through the vent provided for inlet chamber and second and

third compartments. Therefore, this plant can be installed even

inside homes.

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Chapter 4: Design Calculations

1. Basic Data –

i. Average weight of fresh human night soil –

300gm/person/day.

ii. Solid content -25% (varying between 20% to 30%).

iii. Quantity of biogas generated -35 to 40 litres/day/person.

iv. Optimum water use -2·17 litres/ person/day.

v. Desirable solid content of slurry – 3% to 5%.

2. Calculations for 1 CuM biogas/day – Daily feed for 1

CuM biogas/day–Night soil from 25 persons/day.

Therefore, daily input 25x2·17 – 54·25 litres/day.

Therefore, for 45 days HRT

Required digester volume= 54·25 x 45 = 2441·25 litrers.

Now,

Total volume= vol. of I chamber + ½(vol. of II+III chamber)

Therefore,

The proposed dimensions of I chamber (digestion chamber)

are,

Length = 1·125 M, Breadth = 1·05 M, Depth = 1·5 M.

Thus,

Volume of I chamber (digestion chamber) = 1·7718 CuM

Volume of II chamber (displacement chamber) = 0·4061 CuM

Volume of III chamber (outlet chamber) = 0·4061 CuM

Total vol. of I+II+III chambers = 2·584 CuM

3. Calculations for 2 CuM biogas/day – Daily feed for 2

CuM biogas/day – Night soil from 50 persons/day.

Therefore, daily input–50x2·17=108·5 litres/day

Therefore, for 45 days HRT –

Required digester volume = 108·5x45=4882·5 litres

Therefore,

The proposed dimensions for I chamber (digestion chamber) are,

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Length=2·03 M, Breadth=1·05M, Depth=1·5 M.

Thus,

Volume of I chamber = 3·1985 CuM

Volume of II chamber = 0·780 CuM

Volume of III chamber = 0·780 CuM

Total Volume of I+II+III = 4·758 CuM

4. Calculations for 3 CuM biogas/day –

Daily feed for 3 CuM biogas /day – Night soil from 75

persons/day.

Therefore, daily input – 75x2·17=162·75 litres/day

Therefore, for 45 days HRT –

Required digester volume = 162·75x45=7323·75 litres.

Therefore,

The proposed dimensions for I chamber (digestion

chamber) are,

Length = 3·15 M, Breadth = 1·05 M, Depth = 1·5 M.

Thus,

Volume of I chamber = 4·97 CuM

Volume of II chamber = 1·11 CuM

Volume of III chamber = 1·11 CuM

Total volume of I+II+III = 7·19 CuM

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Chapter 5 Construction Work

1. Rectangular lineout is given for excavation. In lineout

150 mm more on each side than the actual construction

measurements are given to make an allowance for a regular

excavation.

2. Soling is laid and P.C.C. as per drawing is laid.

3. Bricks of good quality are used for brick work.

Improperly burnt or excessively burnt bricks are not used.

Bricks are soaked fully in water. Care is taken to see that mud

does not get attached to the bricks.

4. Bricks are laid in alternate layers of headers and

stretchers. While laying the bricks, each layer is laid

continuously for all the walls including partition walls. So that

the bonding at the corners is not weak. (A practice of raising

each wall separately is not followed.)

5. During this process, the partition wall is also

simultaneously laid leaving appropriate gap for the displacement

window. Brick work is raised up to 525 mm.

6. While laying the next layer, an arch is constructed over

the window. For the arch, dry bricks are stacked to serve as a

shuttering for the arch. The height of the arch at the centre is

600 mm and at both corners it is 525mm.

7. Brick work is then continued up to a total height of 1.4

meters, taking care that top most layer is a header layer.

8. On top of this a stretcher layer is laid with bricks laid on

edges so that a groove of 50 mm is formed in the middle.

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9. The dry bricks which were stacked to serve as a

shuttering for the arch are removed, so that a passage is

established between first and second chamber.

10. A shuttering is fixed for the first chamber. A slope of

about 25 mm is given at the far end.

11. A hole is provided in the shuttering at an appropriate

place for the inlet pipe.

12. Reinforcement steel is laid as per specifications in the

drawing. A two way slab is planned.

13. The slurry inlet assembly is placed in the hole provided

in the shuttering. Care is taken to see that this assembly is

placed over the reinforcement so that it would get properly

embedded in the R.C.C. slab.

14. The Biogas outlet assembly is placed at the far end of

the slab, which is raised by 25 mm while providing shuttering,

care is taken to see that flanges of gas outlet assembly are placed

below the reinforcement grill.

15. The R.C.C slab is then laid in 1:2:4 proportion of cement

concrete. While laying the cement concrete, care is taken to see

that the flanges of slurry inlet assembly and biogas outlet

assembly are properly embedded in cement concrete. Further,

care is taken to see that a slab is laid in shortest possible time

and in one sitting.

16. Care is taken to see that the cement concrete is laid

properly in the groove provided in the top layer of brick work.

Also, short lengths of steel are inserted in the groove at the four

corners.

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17. The slab is then kept wet for curing. A curing period of

minimum 21 days is given. Shuttering is removed after two

weeks.

18. After laying the slab, on the next day the brick work on

top of the slab and the second and third chambers is completed,

to the height of 300 mm. (During the construction of the

superstructure the weight of the partition walls is likely to come

on the slab. In order to laterally distribute it, the placing of an

arch under the partition wall is suggested.)

19. Simultaneously, tee pipe is fixed for slurry outlet from

third chamber. The bottom of horizontal arm of tee is kept at

the level of top of the slab in first chamber.

20. After about 15 days after casting the slab, the shuttering

of the digestion chamber is removed through the displacement

window.

21. Lime cement mortar is then used for rendering the

plaster coating for all the chamber walls and the roof from

underneath. Addition of lime helps in reducing the chances of

development of hairline cracks in the plaster layer. Further, it

will have to be seen meticulously that excess water is not added

during preparation of cement mortar. Proportion of water

quantity of approximately 30 to 35 litres per 50 kg bag of

cement is observed. Freshly prepared cement mortar must be

used. Polymer additives for water proofing should be used.

Plastering the chambers should be preferably completed in a

single day so as to avoid joints in the CM plaster layer. These

precautions will help in rendering gas tight plastering avoiding

any possibilities of biogas leakage.

28

22. Plaster coating is done in two layers, each of 12 mm

thickness.

23. For the first coat, 1:3 cement mortar with 10% lime

powder (Percentage in relation to quantity of cement) is used.

24. For the second coat, 1:2 cement mortar with 10% lime

powder is used.

25. Neat finish is provided with cement to which lime

powder is added. (10% lime).

26. All the corners and the joints are rounded off during the

process of plastering. This is done followed at the joints for

slurry inlet assembly and biogas outlet assembly also.

27. All renderings of cement mortar plaster coating are

completed in one day, so that there is no chance left for the gas

leakages at the joints of the rendering.

28. A groove for the partition wall between second and third

chamber is prepared by laying additional cement mortar without

disturbing the initial plaster coating.

29. On the next day, partition wall between second and third

chamber is raised. An opening of 100 mm dia. is provided in

this wall as a connection between the second and third chamber

at 700 mm from the bottom of the plant. An opening of 50 mm

dia. is provided in the same wall above the level of the slurry

outlet, so as to serve as the vent.

30. The partition wall is then coated with cement mortar

plaster rendering.

29

31. Bottom of the chambers is also finished with cement

mortar.

32. On top of the R.C.C. slab of first chamber, an inlet

chamber is constructed. An inspection window opening through

the wall, to the outside is provided. Further a vent pipe is laid

horizontally from third chamber to the inspection chamber.

33. A vertical vent pipe is provided from the inspection

chamber. This vent pipe will be later carried above the roof of

the latrine super structure. It will be fixed along the wall of

latrines super structure.

34. Sufficient time of 21 days for curing of the plaster is

allowed, taking care to see that the plaster coating is kept wet

continuously.

35. After curing, the plaster is allowed to dry completely.

36. After the plaster has dried, the roof and side walls of the

digestion chamber are painted in two coats by bituminous paint

or epoxy resin paint. (Two component water miscible epoxy

paint is preferable).

37. After the paint has dried, the scum breaker fittings are

fitted along the slurry inlet pipe in the digestion chamber.

38. The slurry outlet pipes are fitted to the tee embedded in

brick work at slurry outlet level. Upward arm of the tee is

brought above the level of cover over second and third chamber.

This opening is closed with removable end cap. The opening

serves as an inspection cum maintenance window.

30

39. Dry bricks are stacked in displacement window up to a

height of 275 mm. The second and third chambers are then

covered with flagstone or R.C.C slab fitted with chamber

covers. The vent pipe will emerge from under the cover.

40. The joints are properly sealed with cement mortar so that

the gases do not escape from the joints.

41. A channel is provided from the slurry outlet to manure

pits.

42. Gas supply line fitting along with condensate removal

arrangement is carried out as per requirements.

43. Water seal trap for the latrine seat is fixed on top of the

digestion chamber, the opening of the trap leading to inlet

chamber on top of the slurry inlet pipe.

44. The latrine superstructure is constructed on top of the

digestion chamber and toilet seat is fitted over the water seal

trap.

45. While fixing the seat, the inlet chamber is covered from

the top so that inlet chamber has an access only from out side

through the window in the wall.

46. As stated earlier, vent pipe assembly is led above the

roof of the latrine superstructure.

47. The gas plant is then completely filled with water. If

possible the slurry from the other biogas plant could be put in

the digestion chamber via latrine seat. This slurry will act as

seeding for the digestion process.

31

48. The latrine and the biogas plant will then be ready for

use.

49. If required toilet seats can be placed at distance from

biogas plant. In that case, the inlet chamber will have to be

provided a separate chamber cover.

32

Chapter 6: Field implementation of the design

Field Performance

The plants of this design are functioning at a number of

homes in Dehu village of Pune district, as also in Madhya

Pradesh, Tamil Nadu and Hyderabad with very satisfactory

performance since 1980. The beneficiaries appreciate the design

as it occupies minimum space, can be installed inside homes,

and the top of the biogas plant can be used as an empty floor

space. These plants have been constructed in places like hostels,

institutions etc. In these cases, the plant capacities reach upto 20

cu.m. gas capacity per day.

Need for Training

The construction demands meticulous work and skilled

masons. Cement plaster coating in gas storage area is crucial.

Hence, it demands skills on the part of the masons. Therefore

adequate training of the masons is essential. This is being

carried out by Appa Patwardhan Safai wa Paryawaran

Tantraniketan, Dehu village, District:Pune, Maharashtra, India.

The need for adequate supervision during construction is

also very crucial. Further the guidance for operation and

maintenance of the plant as well as for the gas utilization system

is very essential.

Suggestions for Promotion And Wider Application

1. This design is very useful in urban housing complexes.

33

2. It can be accommodated in a limited space and can be

incorporated during the construction of the house.

3. In rural area it can be used as a shared latrine facility.

34

Annexures:

Table I A: Estimates of quantities of Materials Required for

1CuM (One CuM) capacity ‘Malaprabha’ Biogas Plant

Sr.

No.

Item Quantity Unit Amt in

Rs.

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Bricks

Cement

Sand

Soling

Stone Chips

Lime

P.V.C. Assembly Set

for Inlet and gas outlet

A.C. Pipe 75 mm dia.

A.C. Bend 75 mm

A.C. Cowl & Net cover

Chamber Cover

10 mm Steel Bar

Binding Wire

Rough Shahabad Stone

Paint

1621

720.009

ie 14.40

1.71665

0.612

0.5669

13.543

One

4.0

One

One

One

40.575

ie 16.027

0.25

1.2375

1.78104

Nos.

Kg.

Bag

m³

m³

m³

Kg.

No.

Meter

No.

No.

No.

Meter

Kg.

Kg.

m²

Litre

Total

N.B. Cost will change depending on Market rates.

35

Table II A: Estimates of quantities of Materials Required

for 2 CuM (Two CuM) capacity ‘Malaprabha’ Biogas Plant

Sr.

No.

Item Quantity Unit Amount

in Rs.

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Bricks

Cement

Sand

Soling

Stone Chips

Lime

P.V.C. Assembly Set

for Inlet and gas outlet


A.C. Bend 75 mm


Chamber Cover

10 mm Steel Bar

Binding Wire


Paint

2246

1058.300

ie 21.166

2.47198

0.9664

0.89436

20.2328

One

4.5

One

One

One

62.84

ie 24.821

0.25

2.075

2.1492

Nos.

Kg.

Bag

m³

m³

m³

Kg.

No.

Meter

No.

No.

No.

Meter

Kg.

Kg.

m²

Litre

Total


36

Table III A: Estimates of quantities of Materials Required

for 3 CuM (Three CuM) capacity ‘Malaprabha’ Gas Plant

Sr.

No.

Item Quantity Unit Amou

nt in

Rs.

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Bricks

Cement

Sand

Soling

Stone Chips

Lime

P.V.C. Assembly Set for

Inlet and gas outlet


A.C. Bend 75 mm


Chamber Cover

10 mm Steel Bar

Binding Wire


Paint

3844

1380.943

ie 31.618

3.8236

2.2581

1.2702

28.511

One

5.0

One

One

One

90.30

ie 35.668

0.50

2.70

3.750

Nos.

Kg.

Bag

m³

m³

m³

Kg.

No.

Meter

No.

No.

No.

Meter

Kg.

Kg.

m²

Litre

Total


37

Table I B: Estimates of Labour Component for

1 CuM (One CuM) Capacity ‘Malaprabha’ Biogas Plant

Sr.

No.

Item Period Cost in

Rs.

1.

2.

3.

4.

5.

Mason

Carpenter

Painter

Labour

Excavation

7 Work Days

1 Work Day

1 Work Day

16 Work Days

Lump sum

Total

N. B. Cost will change depending on prevalent daily wages rates.

Table II B: Estimates of Labour Component for

2 CuM (Two CuM) Capacity ‘Malaprabha’ Gas Plant

Sr.

No.

Item Period Cost in

Rs.

1.

2.

3.

4.

5.

Mason

Carpenter

Painter

Labour

Excavation

10 Work Days

1 Work Day

1 Work Day

22 Work Days

Lump sum

Total


38

Table III B: Estimates of Labour Component for

3 CuM (Three CuM) capacity ‘Malaprabha’ Gas Plant

Sr.

No.

Item Period Cost in

Rs.

1.

2.

3.

4.

5.

Mason

Carpenter

Painter

Labour

Excavation

13Work Days

1 Work Day

1 Work Day

28 Work Days

Lump sum

Total


On a similar basis, the configuration of compartments can be

adjusted to suit the available space and necessity.

39

Appa Patwardhan Safai Va Paryawaran Tantraniketan

Dehu, Tal. Haveli, Dist. Pune,

Maharashtra, Pin. 412 109, INDIA.

It has been observed that in developing countries, about

80% ailments occur because of improper sanitation and unsafe

water supply, 80% aliments could possibly be prevented at

causative end, rather than at an attempt to treat these aliments.

Under these circumstances, there is a need for positive

sanitation promotion efforts if health promotion in developing

countries is to be achieved. Therefore, it is necessary to

promote these ideas and to suggest appropriate low cost

technologies for sanitation promotion.

In light of these considerations, Appa Patwardhan Safai

W Paryawaran Tantraniketan was established in 1988.

Activities of Tantraniketan A : Training : Technical and practical training imparted at

this institution is useful for creating awareness and developing

manpower for sanitation, non conventional energy sources and

environment programmes.

B : Research and Development : Sanitation is a discipline

which has so far been neglected for multiple reasons. Therefore,

there is a need to undertake research and development work as

regards various aspects of sanitation. This institution is trying to

do its own bit in the field in its own laboratory. Research as

regards biomethanation is also undertaken.

C : Project consultancies : With available knowledge

resource, the institution offers consultancy services so as to

come up with field level solutions for sanitation problems and

bioenergy projects.

D : Project Implementation : Wherever necessary, the

institution also undertakes project implementation work

especially if the work is of pioneering nature.

40

JYOTSNA AROGYA PRABODHAN Dehu, Tal. Haveli, Dist. Pune,

Maharashtra, Pin 412 109, INDIA,

In a developing country like India, attainment of health

for its population is an important means towards bright future.

Jyotsna Arogya Prabodhan Proposes to contribute in a small

way in tackling this gigantic task. This institution is engaged in

health education activities predominantly amongst the rural

population of India.

With the highest possible standard of health for the

population in view, it is under taking various educational and

field research activities for creating awareness, imparting

information, fostering attitudes and inspiring ideals as far as

health is concerned. Some of its activities are as follows:

• Preparing and using various audio-visual aids,

• Organizing discussions, seminars etc. about the various

aspects of health,

• Publishing health information hand outs, periodicals etc.,

• Organizing exhibitions etc.,

• Establishing health library for public use,

• Undertaking research activities in the field,

• Running experimental workshop for sanitary

conveniences.

JYOTSNA AROGYA PRABODHAN,

AN INSTITUTION BASED IN RURAL AREA

& DEDICATED TO THE CAUSE OF RURAL HEALTH

Malaprabha Biogas Plant developed by Dr S V Mapuskar

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