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GOVT. (AUTO.) AYURVEDIC COLLEGE AND HOSPITAL GWALIOR

DEPARTMENT OF SWASTHAVRATHA

SUBMITTED TO-

DR. UPASANA BHARADWAJ (H.O.D)

Dr. Pawan Sharma

(lecturer)

SUBMITTED BY-

HIRDESH AGRAWAL

ROLL NO-14

(BAMS 3rd YEAR)

TOPIC- EXCRETA DISPOSAL FOR SEWERED AREA

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The improper disposal of excreta results many diseases,

e.g. typhoid, paratyphoid, dysentery, diarrhea , cholera, worm infestation,

viral hepatitis, etc. the health hazards of impr1oper excreta disposal are same as that of accumulated solid wastes

EXCRETA

DISPOSAL :

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The disease agent is transmitted from faeces to a new host through various channels i.e., water, fingers, flies, soil and food.
The disease cycle may be broken at various levels i.e., segregation. of faeces, protection of water supplies, protection of foods, personal hygiene and control of flies.
Out of these, the most effective step is segregation of the faeces by imposing a sanitation barrier. This barrier is provided by sanitary latrines and disposal pits.

Transmission

of

Faecal - borne

diseases :

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Water Carriage system and sewage treatment•
Primary treatment.

Screening

Removal of grit

Plain sedimentation

Secondary treatment•

Trickling filters

Activated sludge process

Other methods•

Sea outfall

River outfall

Sewage farming

Oxidation ponds

Methods

for

Sewered Area :

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It is the method of choice for collecting and transporting sewage (excreta) from cities and towns where population density is high.

In this system sewage is collected and disposed by a network of undergoing pipes (sewers).

Water carriage system or

sewerage system :

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There are two types of water carriage system :

(1) Combined- Sewers carry both the sewage and surface water.

(2) Seperate- Surface water is not admitted to sewers.

It is the system of choice.

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i) House hold sanitary fitting ;

Water closet

ii) House drain or sewer:

4 inches diameter pipes fitted 6 inches below the ground with a gradient towards the drain.

A water carriage system consists of the following four Elements :

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(iii) Public or Street or Trunk sewer :

These are 9 inches to 10 feet diameter pipes fitted 3 feet below ground level on a concrete bed. There should be sufficient gradient for self cleansing velocity of 2-3 feet/second. Collected sewage is transported to a place of final disposal

A water carriage system consists of the following four Elements :

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(iv) Sewer Appurtenances ;

MANHOLES-

These are build up at every 100 meter distance ,meeting point of sewers and turns for inspection, repair and cleansing.

TRAPS-

There are three places for traps to remove grit, sand and grease from sewage i.e. under the basin of water closet, house drain joint the public drain and surface water enter the drain.

A water carriage system consists of the following four Elements :

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SEWAGE

SEWAGE :

It is the waste water from a community, containing solid and liquid excreta. It is derived from houses, streets, factories and industries.

SULLAGE :

Waste water which does not contains human excreta e.g. waste water from kitchen and bathroom.

The average amount of sewage which flows through the sewerage system in 24 hours is called the "dry weather flow".

SULLAGE

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Composition :

99.9% water and 0.10% organic and inorganic solids. The offensive odor is due to presence of organic matter.

Aim of sewage purification :

To stabilize the organic matter, so it can be disposed off safely and to convert the sewage water into effluent of an acceptable standard of purity, which can be disposed to land, river or sea.

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(i) BOD (Biochemical Oxygen

Demand):

It is the amount of oxygen absorbed by a sample of sewage during a specific period (usually 5 days) at a specific temperature (20° C) for aerobic destruction or use of organic matter by living organisms. It is 1 mg/lit for natural water, 300 mgs/lit for untreated domestic sewage. If BOD is 100mgs/lit the sewage is supposed to weak and 2300 mgs/lit it is supposed to strong.

Standard for strength of sewage :

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(ii) COD (Chemical Oxygen Demand) :

The oxygen equivalent of that portion of the organic matter in a sample which is susceptible to oxidation by a strong chemical oxidizer.

(iii) Suspended solids :

In domestic sewage usually the amount of suspended solids is 100-500 ppm (mgs/liter). If it is $100 ppm then sewage is called weak and 2500ppm sewage is called strong.

Standard for strength of sewage :

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1. Aerobic-

End products are- CO₂. NH₃, H₂O, NO₃, NO₂, and SO₂.

2. Anaerobic-

End products are- CO₂, NH₃, CH₄, and H₂

The anaerobic decomposition is comparatively a slow process.

Decomposition

Of

Organic Matter :

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METHOD OF

SEWAGE

TREATMENT

Primary

treatment (Anaerobic) :

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(1) Primary treatment (Anaerobic) :

(i) SCREENING -

•Sewage arriving at a disposal work is first passed through metal screen, which is made up of vertical or inclined steel bars situated 2 inches apart.

•It separates the large floating objects e.g. wood pieces, rags, garbage, dead animals etc.

•These objects are removed time to time and disposed off by trenching or burial.

METHOD OF SEWAGE TREATMENT :

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(ii) GRIT or DETRITUS CHAMBER -

-This is a long narrow chamber of 10-20 meters length.

-The velocity of sewage in this chamber is 1 foot/second.

-Sewage after screening is entered in this chamber, where heavier solids e.g., sand and gravel are settled. These solids are removed periodically and disposed off by dumping or trenching.

METHOD OF SEWAGE TREATMENT

Primary treatment (Anaerobic) :

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(iii) PRIMARY SEDIMENTATION -

- Primary sedimentation tanks are rectangular which holds the ¼-1/3 of dry weather flow.

- Velocity of sewage is very slow in this chamber i.e.1-2 feet/minute.

- 50-70% of solids (suspended matter) are sediment here.

- The organic matter which settled down here is called sludge, the fat and grease rise to the surface to form the scum.

METHOD OF

SEWAGE

TREATMENT

Primary treatment (Anaerobic) :

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- The sludge and scum are removed periodically.

- Microorganisms in the sewage break the complex organic matter (solid) into simpler soluble substances and NH3

- When sewage contains organic trade wastes, it is treated with chemicals e.g., lime, aluminum sulphate and ferrous sulphate for the quick precipitation of animal proteins.

METHOD OF

SEWAGE

TREATMENT

Primary treatment (Anaerobic) :

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(2) Secondary treatment

(Aerobic) :

Effluent from primary sedimentation tank still contains living organisms and organic matter in solution of colloidal state. It has a high oxygen demand, and can causes water and soil pollution. It requires secondary treatment by one of these two methods

METHOD OF SEWAGE TREATMENT :

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(i) Trickling filter method (T.F.M.) or percolating filter :

It is a bed of crushed stones or canker, which is 4-8 feet deep and 6-100 feet in diameter (depends on the size of population).
Effluent from primary sedimentation tank is sprinkled the surface by a revolving device.
The device consists of rotating hollow pipes having a row of holes.

METHOD OF

SEWAGE

TREATMENT

Secondary treatment

(Aerobic) :

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A very complex biological growth is formed over the bed, consisting of algae, fungi, protozoa and bacteria. It is known as zoogleal or vital layer.
When the effluent percolates through the filter bed, it gets oxidized by the bacterial flora in zoogleal layer
This filter is biological, not the mechanical.
The oxidized sewage now led into secondary sedimentation or humus tank.
This is a smaller unit and used in towns.

METHOD OF

SEWAGE

TREATMENT

Secondary Treatment (Aerobic)

Trickling

filter method

(T.F.M.) or

percolating filter :

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METHOD OF

SEWAGE

TREATMENT

Secondary Treatment (Aerobic)

Trickling

filter method

(T.F.M.) or

percolating filter :

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(ii) Activated sludge process :

The heart of this process is an aeration tank.
Effluent from primary sedimentation tank is mixed with the sludge drawn from final settling tank which is rich in aerobic bacteria.
Mixture is subjected to aeration for 6-8 hours.
After aeration, organic matter of the sewage gets oxidized into CO, NH, and H₂O by aerobic bacteria.
This is a larger unit and used in big cities.

METHOD OF

SEWAGE

TREATMENT

Secondary

treatment :

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METHOD OF

SEWAGE

TREATMENT

Secondary

treatment :

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After the secondary treatment oxidized sewage is subjected to secondary sedimentation, sludge digestion and disposal of effluent

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Oxidized sewage from trickling filter or aeration tank is led into the secondary sedimentation or final settling tank or humus tank.
Sewage is detained for 2-3 hours in this tank.
The sludge collected in secondary sedimentation tank is called aerated sludge or activated sludge, which is non offensive, rich in bacteria, nitrogen, phosphate and of manuric value.
A part of activated sludge is pumped back into the aeration tank in the activated sludge process and the rest pumped into the sludge digestion tank for treatment and disposal.

(i) Secondary Sedimentation

Or

Final setting :

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(a) Digestion -

Sludge is incubated under favorable conditions of temperature and pH in the sludge digestion tank.
In tank sludge undergoes anaerobic auto-digestion, in which complex solids are broken down into water, CO2, NH3, and CH4.
The volume of sludge is also reduced here.
The complete sludge digestion takes 3-4 weeks or more.

(ii) Sludge

Treatment:

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The residue is non-offensive, sticky and tarry mud, which becomes dry readily and form an excellent manure.
Methane gas is used for heating and lightening purpose.

(ii) Sludge

Treatment:

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(b) Sea Disposal-

Sludge is disposed off in sea cost towns and cities e.g. Mumbai.

(c) Land disposal-

Sludge can be disposed off by composting with town refuse.

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(b) Disposal on land :

If the suitable land is available, the effluent can be used for irrigation purpose e.g. the okhla sewage treatment plant in Delhi.

(iii) Disposal of effluent :

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(3) Other methods of sewage disposal:

(i) Sea Outfall –

Sewage is disposed off in sea without treatment in sea coast towns and cities e.g., in Arabian sea in Mumbai

METHOD OF

SEWAGE

TREATMENT

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Purification of sewage takes place by dilution and slow oxidation.
It is not a good method because offensive solid matter may be washed back to the shore, therefor the sewage outfall is designed to discharge the sewage into deep water at many points.

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(ii) River Outfall –

It is the most unsanitary method of sewage disposal in rivers. However the purification takes place here by dilution and slow oxidation but is insufficient.

METHOD OF

SEWAGE

TREATMENT

Other methods of sewage disposal:

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(iii) Land treatment or sewage farming or broad irrigation –

If sufficient and suitable land (porous soil) is available sewage is applied to the land after grit removal, screening and short period of sedimentation.
one acre space is sufficient for sewage of 100-300 persons.

METHOD OF

SEWAGE

TREATMENT

Other methods of sewage disposal:

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The land is first laid into ridges and furrows then sewage is fed into the furrows intermittently and crops are grown on the ridges
It is suitable for growing fodder grass, potatoes, fruits and trees where fruits are at height, but not suitable for sugar cane, coriander, cucumber, tomato, onion or other underground vegetables.
During rainy season, their management is difficult because they can stink and there is lack of aeration, this is called sewage sickness.

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(iv) Oxidation pond or redox pond or sewage lagoons or waste stabilization tank –

The sewage is disposed off into an open, shallow pool of 3-5 feet depth with an inlet and outlet.
There must be presence of algae, bacteria and sunlight for decaying organic matter.
Organic matter is oxidized into CO₂,NH4,and H₂O by bacteria.

METHOD OF

SEWAGE

TREATMENT

Other methods of sewage disposal:

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Algae used these compounds with sunlight for their growth.
Oxygen is taken from algae and environment.
Cloudy weather lowers the efficiency of this process.
Oxidation ponds are aerobic during sunshine of day and early hours of night but in the remaining hours of night the bottom layers are anaerobic.
The effluent may be used for growing vegetables crops of discharged into river.

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(v) Oxidation ditches and aerated lagoons –

These are low-cost treatment methods for the purification of sewage.
These methods make use of mechanical rotors for extended aeration.
The required area for the waste of 5000-20000 people is 22 acres for oxidation ditches and 2.5 acres for aerated lagoons.

METHOD OF

SEWAGE

TREATMENT

Other methods of sewage disposal:

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(v) Oxidation ditches and aerated lagoons –

METHOD OF

SEWAGE

TREATMENT

Other methods of sewage disposal:

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THANKYOU !

- HIRDESH AGRAWAL