1
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
Published by
Jyotsna Arogya Prabodhan,
Dehu village, Tal. Haveli,
Dist. Pune, Maharashtra 412 109
INDIA
2
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
3
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
4
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
5
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,
6
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.
7
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,
8
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
9
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,
10
• 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
11
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.
12
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
13
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.
14
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
15
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.
16
17
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.
18
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
19
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
21
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.
22
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,
23
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
24
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.
25
26
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.
27
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. 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
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
N.B. Cost will change depending on Market rates.
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. 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
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
N.B. Cost will change depending on Market rates.
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
N. B. Cost will change depending on prevalent daily wages rates.
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
N. B. Cost will change depending on prevalent daily wages rates.
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