KLE College of Engineering and Technology Chikodi

UNIT – 3
RURAL SANITATION:
 Public latrine
 Concept of Eco-sanitation,
 Trenching
 Composting methods
 Two pit latrines
 Aqua privy
 W.C
 Septic tank

 Soak pit.

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Public latrine
Excreta disposal is an important part of over all environmental Sanitation. Inadequate and unsanitary
disposal of infected human excreta leads to the contamination of groundwater and sources of
drinking water supplies.
It is the place of breeding for flies to lay their eggs and to carry infection from faeces of human
beings. Man is the reservoir of infection for several diseases.
All the diseases that spread through faecal can be controlled or prevented through good sanitary
barriers through safe disposal of human excreta.
Types of Public Latrines
1. Pit latrines

Pit latrines are the most common and simplest form of excreta disposal in many developing
countries. These are almost universally acceptable in rural areas and are also widely used in low
income urban communities, although often not appropriate. They are, however, the cheapest system
possible and the system most appropriate for individual householders responsible for their own
sanitation. A pit latrine consists of manually dug or bored hole into the ground, an appropriate seat or
squatting plate with or without a super structure is provided. The pit is simply a hole in the ground
into which excreta fall. Urine and other liquids soak into the ground and solid materials are retained
and decomposed in the pit. Simple pit latrines though not fully sanitary, are sometimes promoted in
order to discourage open defecation and other unsanitary practices. Conventional pit latrines with a
basic pit and a shielding superstructure have many disadvantages, odor and fly and
mosquito nuisance in particular.

Advantages of pit latrine

 Pit latrines are least costly;

 Simple technology
 Helps to develop practice to use latrine
 These are easily constructed and maintained;

Disadvantages of pit latrine

 Flies lay their eggs in faeces within poorly built latrines. Increase in the fly population
increases spread of diseases caused by the faecal pathogens they carry;
 Odor nuisance;
 Improper lining of pits may lead to collapse of the superstructure.
 Risk of falling into the pit
 Risk of groundwater pollution
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Fig: Simple Pit Latrines

2. Ventilated Improved Pit (VIP) Latrines

The VIP is a ventilated improved pit. It is an improvement over the simple pit because
continuous airflow through the tall vertical ventilation pipe vents with fly screen fitted outside
the superstructure to trap flies as they escape towards the light and reduce odour nuisance.
VIP remains among the simplest and cheapest toilet systems. populated areas. It is a non water
dependent latrine, which does not require water for functioning, though small amount of water
is required for cleaning of squat plate.

Advantages

 Significant reduction in pathogens

 Potential for use of stored faecal material as soil conditioner
 Flies and odours are significantly reduced (compared to non-ventilated pits)
 Can be built and repaired with locally available materials. Long service life
 Does not require a constant source of water
 Less chances for transmission of excreta related disease than lid latrine.
 Good health and hygiene practice
 Can be used as fertilizer after one year of composting.
 Construction and maintenance are easy.

Disadvantages
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 Leachate can contaminate groundwater

 No specific reuse of faeces and urine
 Pits are susceptible to failure/overflowing during floods; stagnant water in pits may promote
insect breeding
 Manual removal of humus is required
 Possible contamination of groundwater

Fig: Ventilated Improved Pit Latrine

3. Pour Flush Latrines

The pour flush latrine is a specially designed water sealed bowl, which requires 1-2 liters of water for
flushing the excreta. This is a water dependent latrine. Some water always remains at the bottom of
the pan after it has been used. This water seal latrine room eliminates the entry of odour and prevents
rodents to the latrine room from pit through the bowl.

Advantages

 The water seal effectively prevents odours

 The excreta of one user are flushed away before the next user arrives
 Low capital costs; operating costs depend on the price of water
 Privacy
 Little chance for transmission of excreta related diseases.
 Good health and hygiene practice

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 Appropriate where the water is available.

 Construction and maintenance are cheap and easy.

Disadvantages/limitations

 Requires a constant source of water (can be recycled water and/or collected rainwater)
 Risk of groundwater and surface water contamination.
 Not appropriate where the water is not available
 Difficult to construct in high ground water table area.
 Requires materials and skills for production that are not available everywhere
Coarse dry cleansing materials may clog the water sea
4. Eco-san Toilet (Ecosanitation)

Ecological sanitation is based on recycling principles. Excreta and Urine are separated for disposal.
The eco-san model consists the double vault compost latrine consists of two water tight
chambers(Vaults) to collect feaces. Urine is collected separately as the contents of the vault have to
be kept relatively dry.

Initially a layer of absorbent organic material is put in the vault and after each use, the faeces is
covered with ash to deodorize the faeces, soak up excessive moisture and to improve
carbon/ nitrogen ratio. When the first vault is three quarters full, it is completely filled with dry
powered earth and sealed so that the components can decompose anaerobically. The second vault is
used until it is also three quarters full and the first vault is emptied by hand, the contents are used as a
fertilizer.

Advantages

 It is most ideal for areas where water is scarce and pour flushing implies water to be carried
from source, or areas where water table is high such as flood plains or coastal areas and
densely populated areas where risks of ground water pollution from pits to drinking water
sources is assessed high.

Disadvantages

 Proper operation needs full understanding of the concept, lack of which makes the system
dysfunctional.
 Where people are eager to use the contents as fertilizer, they may not allow sufficient time for
the contents to become pathogen free.

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 This system is only to be used where people are motivated to use human excreta as a
fertilizer.

Trenching

Trenching is the act of burying the organic waste directly into the garden soil. The advantage of this
method over conventional composting is that it enables you to compost meat, grains, dairy and
cooked foods in addition to other kitchen scraps. The material if it is covered by at least 30-45 cm
(12-18”) of soil.

Trenching is an excellent method to use in combination with growing annual plants, especially heavy
feeding plants like cabbage, corn and squash. It also encourages the development of deep, water
conserving root systems. Trenching creates an underground band of nutrient-rich humus for the
plants. The trenched materials will retain more nitrogen during the process.

Procedure

1. Dig a hole or trench in your garden 45-60 cm (18- 24”) deep and as wide and long as is
practical -- a shovel’s width is usually fine. Pile the soil up beside your trench.
2. Fill the bottom 15 cm (6”) of your trench with your nutrient-rich food waste and organic
materials. Make sure the materials are quite moist before you bury them. Fill in the hole with
the excavated soil, making sure there is at least 30- 45 cm (12-18”) of soil on top of them.
3. Protect the soil with a layer of organic material (i.e. leaves or straw). Alternatively, you can
also sow a cover crop to protect the soil from the elements and suppress weeds in the time it
takes for the trenched materials to decompose.

Trench composting offers some great advantages:

 It virtually eliminates all smell and rodent problems if materials are buried at least 45 cm (18”)
deep and well covered with garden soil.

 It requires no investment in containers or materials, all you need is a shovel!

Water Closets (WCs)

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The water closet is defined as a sanitary fitting which is designed to receive human excreta directly from the
person using it.

The water closets are of two types

1. Indian type water closet

2. European type water closet

Indian type water closet

 It is made up of porcelain and the pan and the trap are in two different pieces.
 The trap has an opening for anti siphonage pipe.
 The pan has a flushing rim to spread the flush water.
 The excreta do not fall directly into the trap and there are chances for excreta to become foul,
if not properly flushed.
 It is fixed in squatting or sitting position at floor level.
 The over all length varies from 450 mm to 675 mm.
 Width near one end is about 150 mm and increased to about 225 mm to 280 mm near the
other end.
 Over all height including the trap is about 400 mm to 500 mm.
 It requires 10 liters of water for proper flushing.

European types water closet:

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 It is made up of porcelain
 The pan has a flushing rim to spread the flush water
 Cover is provided at the top.
 The excreta do not fall directly into the trap and with a good flush of water, the pan remains
in clean position.
 Over all length varies from 500 mm to 600 mm
 Height varies from 350 mm to 400 mm.
 It is some times reffered as commode type water closet.

Requirements of good water closets

 It should be convenient in use for persons of different age groups.

 The flushing should be effectively be achieved with small quantity of water.
 The surface of pan should be smooth, durable and attractive in appearance and should be such
that excreta do not stick to it and flow down easily.

Two pit latrines (Twin Pit Latrines)

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The Twin Pit Water Seal Toilet is a complete excreta disposal system which, on one hand fulfills all
the sanitary requirements and provides continuous operation with minimal efforts.

The main components of such a toilet are the water seal pan/trap arrangement, squatting platform,
junction chamber, two pits and a superstructure.

The squatting platform is a raised pucca floor constructed with appropriate plinth and foundation.
The pan has a steep bottom slope which allows easy flushing of excreta. The outlet of the pan is
connected with a P-trap. On flushing, some water always remains in the trap and forms a water seal.
The water seal prevents the bad odour coming from excreta. The outlet of the trap is connected with
a junction either by using a pipe or by constructing a covered brick drains.

The junction chamber has one inlet(connected to the P traps) and two outlets (connected to the leach
pits) which are for alternate use. A temporary or permanent superstructure is constructed over the
platform for privacy and protection.

For the twin pit toilet operational, one of the outlets of the Y-junction in the junction chamber is
blocked while the other outlet is kept open to the corresponding pit. The disposal process of the
exceta is the same as in a ‘direct pit toilet’. In this case, when the first pit gets filled up, the flow of
excreta has to be diverted to the stand-by second pit. For doing this, one has to remove the cover of
the junction chamber, open the outlet connected to the second pit, block the outlet connected to the
first filled up pit and replace the junction chamber cover. The contents of the filled pit will become
organic humus and safe for manual cleaning in about twp years. When the second pit also gets filled
up, the first pit is cleaned and the same operation is repeated to dvert the flow of excreta from the
second pit to the first pit as was followed earlier. Thus the “Twin-pit Water Seal Toilet” provides a
continuous operation.

Composting

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• It is a method where in the combined disposal of solid waste is carried out along with stable
litter, night soil and sludge.

• Compost is humus like material, which is generated due to the breakdown of organic matter
under bacterial action,

• Rich manure.

• Thus the final product of degradation in composting has a recyclable component and the
compost could be sold at a price to agriculturists.

• Composting uses aerobic method of digestion.

Pre‐treatment :

• The refuse or solid waste is pre‐sorted to remove materials that could be recycled, which cannot be
composted.

• It is thereafter ground to reduce the waste particle size and this improves the efficiency of
decomposition process.

(a) Bangalore method

• First carried out in Indian Council of Agricultural Research at the Indian Institute of Science,
Bangalore.

• It is also known as the hot fermentation process due to the generation of heat in the process to
decompose the waste.

Procedure

• In this method long trenches are dug each with a depth of 1 m and width of 1.5‐2.5 m.
Greater depths is not recommended since they delay the process of decomposition and
therefore decrease its effectiveness.

• The refuse is then placed in the trench at the bottom making a layer of about 15 cms thick.

• Over this a layer of nightsoil is put to a depth of 5 cms.

• In this manner alternate layers of solid waste and nightsoil are layered one above the other till
the heap rises 30 cms above the ground level.

• The top layer is recommended to be of refuse of about 25 cms thickness.

• Thereafter the heap is covered with excavated earth firm enough to not allow a person’s legs
to sink in the heap while walking.

Process :

• The fermentation process begins in a week’s time with generation of considerable amount of
heat, which stays for 2 to 3 weeks.

• The organic mass is decomposed and pathogenic microorganisms are destroyed in the
process, which is completed in 4 to 6 months.
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• Gases such as ammonia, methane, carbon dioxide and nitrogen produced in the process are
released into the atmosphere.

• The resultant manure is well‐decomposed, odourless, material of high market value.

• The soluble material produced may leach into the underlying or surrounding soil or ground
water.

b) Indoor Method of Composting

• Uses manual turning of piled up mass (refuse+night soil), for its decomposition under aerobic
condition.

• In this method, layers of vegetable wastes and night soil are alternatively piled in depth of
about 7.5 to 10cm each, to a total depth of about 1.5m in a trench or above the ground to form
a mound called Windrow.

• A windrow is a long mound or stack of organic MSW dumped on land in a height of about
1.5 to 2m, usually about 2.5m to 3m wide at the base.

• The Composting waste is aerated by periodically turning the waste mix in the windrow.

• Manual turning- Pitch Fork is used.

• Larger plant- Mechanical devices like self propelled over cab loaders, rotary plough etc may
be used to turn the refuse once or twice per week, which serves to introduce oxygen and
control the temperature.

• Bulldozers are used for reshaping the stacks and for forming new ones.

• The moisture content of the turning mass is maintained at about 55% for getting optimal
decomposition of wastewater.

• The process of turning is continued for about 4 to 5 weeks, during which time the readily
biodegradable organics are consumed.

• Curing- 2 to 8 weeks without turning.

• Entire composting takes 3 to 4 months time to complete, after which the compost becomes
ready for being taken out for use or for sale.

Vermicomposting
• Utilizing earth worms and microorganisms to convert organic waste into a nutrient-rich
humus like material known as vermicompost (worm castings)

Benefits of vermicompost

Vermicompost is a nutrient rich compost which:

o helps better plant growth and crop yield

o improves physical structure of soil.

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o enriches soil with micro-organisms

o attracts deep-burrowing earthworms already present in the soil which,indirectly

improves fertility of soil.

o increase water holding capacity of soil.

o enhances germination, plant growth, and crop yield.

o improves root growth of plants.

o enriches soil with plant hormones such as auxins and gibberellic acid.

o it is helpful in elimination of biowastes .

Vermicompost contains :

o 1.6% Nitrogen;

o 0.7% Phosphorus;

o 0.8% Potash;

o 0.5% Calcium;

o 0.2% Magnesium;

o 175 ppm Iron;

o 96.5 ppm Manganese;

o 24.5 ppm Zinc

o 15.5 C:N ratio.

Method of Production
Vermicompost can be produced by two methods : Pit Method

Pit method is commonly used for small scale production of vermicompost. These steps can be
followed :

 Construct a pit of 3 x 2 x 1 m size (L x W xD) over ground surface using bricks. Size
of pit may vary as per availability of raw materials

 Fill the pit with following four layers:

• 1st layer – sand or sandy soil of 5-6 cm. This layer helps to drain excess water
from the pit.

• 2nd layer - paddy straw or other crop residue of 30 cm above 1st layer which
will be used for providing aeration to the pit.

• 3rd layer - 15 to 30 days old dung over paddy straw layer at a thickness of 20-
30 cm. This helps in initiating microbial activity.

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• 4th layer - pre-digested material about 50 cm

 Inoculate earthworm @ 1000 worms per square meter area or 10 kg earthworm in 100
kg of organic matter.

Spray water on the bed and gunny bag. Maintain 50-60% moisture of the pit by periodical water
spraying.

Septic Tank
A septic tank is a watertight chamber made of concrete through which domestic wastewater (sewage)
flows for primary treatment.[1] Settling and anaerobic processes reduce solids and organics, but the
treatment is only moderate.[1] Septic tank systems are a type of onsite sewage facility (OSSF). They
can be used in areas that are not connected to a sewerage system, such as rural areas. The treated
liquid effluent is commonly disposed in a septic drain field which provides further treatment.
However, groundwater pollution may occur and can be a problem.

Septic systems are underground wastewater treatment structures, commonly used in rural areas
without centralized sewer systems. They use a combination of nature and proven technology to treat
wastewater from household plumbing produced by bathrooms, kitchen drains, and laundry.
A typical septic system consists of a septic tank and a drainfield, or soil absorption field.
The septic tank digests organic matter and separates floatable matter (e.g., oils and grease) and solids
from the wastewater. Soil-based systems discharge the liquid (known as effluent) from the septic
tank into a series of perforated pipes buried in a leach field, leaching chambers, or other special units
designed to slowly release the effluent into the soil or surface water.

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Design of Septic Tank

The capacity of septic tank depends on number of users and interval of sludge removal. Normally
sludge should be removed every 2 years. The liquid capacity of tank is taken as 130 liters to 70 liters
per head. For small number of users 130ltr per head is taken.

A septic tank is usually provided with brick wall in which cement mortar [not less than 20cm (9
inch)] thick and the foundation floor is of cement concrete 1:2:4. Both inside and outside faces of the
wall and top of the floor are plastered with minimum thickness of 12mm (one-half inch) thick
cement mortar 1:3 mix.

All inside corners of septic tank are rounded. Water proofing agent such as Impermo, Cem-seal or
Accoproof etc. is added to the mortar at the rate of 2% of the cement weight. Water proofing agent is
to be added in similar proportion in to the concrete also for making floor of the tank.

For proper convenience in collection and removal of the sludge, the floor of septic tank is given a
slope of 1:10 to 1:20 towards the inlet side. Which means that floor of the outlet side will be on the
higher elevation than the floor at inlet side.

Aqua Privies

An aqua-privy has a watertight tank immediately under the latrine floor. Excreta drop directly into
the tank through a pipe. The bottom of the pipe is submerged in the liquid in the tank, forming a
water seal to prevent escape of flies, mosquitos and smell. The tank functions like a septic tank.
Effluent usually infiltrates into the ground through a soakpit. Accumulated solids (sludge) must be
removed regularly. Enough water must be added to compensate for evaporation and leakage losses.

Three chambers are constructed in this aqua privy. The end of the pan is taken about 100 mm deep in
water to provide a water seal. The night soil smoothly falls into first chamber and it is decomposed
under anaerobic conditions. The gases formed during the decomposition are allowed to escape into
the atmosphere through the vent pipe provided in the second chamber.

The second chamber is connected to the atmosphere and in this chamber the aerobic bacteria attack
the organic matter. The first and second chambers are of equal capacity and the sludge is generally
removed once in two years.

The effluent from second chamber is taken to the third chamber through a pipe whose outlet is
situated near the bottom of chamber. The third chamber is of small size and it is filled with clinker.
The effluent while rising through the clinker gets purified and it can be used for farming or
gardening or can be directly disposed off in nearby water courses.

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The aqua privy is the most useful method of disposal of night soil without the help of carriage system
and hence, it is most suitable for localities having no piped water supply. It is economical and
hygienic. Such type of privies are found to be convenient for factories, hill stations, isolated colonies,
villages etc.

Advantages Disadvantages
Does not need piped water on site Water must be available nearby
Less expensive than a septic tank More expensive than VIP or pour-flush latrine
Fly, mosquito and smell nuisance if seal is lost because insufficient
water is added
Regular desludging required, and sludge needs careful handling
Permeable soil required to dispose of effluent

Soak Pit
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A soak pit, also known as a soakaway or leach pit, is a covered, porous-walled chamber that allows
water to slowly soak into the ground. Pre-settled effluent from a Collection and Storage/Treatment or
(Semi-) Centralized Treatment technology is discharged to the underground chamber from which it
infiltrates into the surrounding soil.
As wastewater (greywater or blackwater after primary treatment) percolates through the soil from the
soak pit, small particles are filtered out by the soil matrix and organics are digested by
microorganisms. Thus, soak pits are best suited for soil with good absorptive properties; clay, hard
packed or rocky soil is no Design Considerations

The soak pit should be between 1.5 and 4 m deep, but as a rule of thumb, never less than 2 m above
the groundwater table. It should be located at a safe distance from a drinking water source (ideally
more than 30 m). The soak pit should be kept away from high-traffic areas so that the soil above and
around it is not compacted. It can be left empty and lined with a porous material to provide support
and prevent collapse, or left unlined and filled with coarse rocks and gravel. The rocks and gravel
will prevent the walls from collapsing, but will still provide adequate space for the wastewater. In
both cases, a layer of sand and fine gravel should be spread across the bottom to help disperse the
flow. To allow for future access, a removable (preferably concrete) lid should be used to seal the pit
until it needs to be maintained.

Advantages Disadvantages/limitations
- Can be built and repaired with locally - Primary treatment is required to prevent clogging
available materials - May negatively affect soil and groundwater
- Technique simple to apply for all users properties
- Small land area required
- Low capital and operating costs

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