sewage and excreta disposal

8/3/2019 Sewage and Excreta Disposal

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EXCRETA, SEWAGE,REFUSE DISPOSAL


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EXCRETA: HUMAN FECES AND URINE Contains nutrients:

Nitrogen (N) 12 gPhosphorous (P) 2 gPotassium (K) 3 gOrganic Matter 90 g

Most organic matter in feces Most N and P (70-80 %) in urine. K equally distributed between urine and feces.


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Nutrient excretion by humans is directly linked to diet

We excrete the same amount of nutrients that we take upin our diet (except for children who retain a smallproportion for growth of bones)

The amount of excreted nutrients by one person is thesame amount that is needed as fertiliser to grow the foodfor that person

N

NP

P

Diet Excreta


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Excreta: Human Feces and Urine Dry Systems

Human (sanitary) waste in settings where water use islimited by preference or lack of indoor plumbing for water

supply and liquid waste (sewage) disposal

Pre-treatment prior to use Nutrients and organic matter are: detrimental in surface

water, eutrophication causes anoxia and fish kills

Beneficial on land as fertilizer, soil conditioner, land

stabilizer Potential for excreta misuse and environmental pollution is

great if there is no proper attention to management plans

and human behavior considerations


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Public Health importance:

The health hazards of improper excreta disposal are:

1. Soil Pollution.

2. Water Pollution.

3. Contamination of foods.

4. Propagation of flies.


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Diseases resulting from contamination are :

1. Typhoid and paratyphoid fever.

2. Diarrheas and Dysenteries.

3. Cholera.4. Hook worm and other intestinal parasitic

diseases.

5. Viral hepatitis.

6. Poliomyelitis and other viral infections.


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Approved types of toilet facilities:

LEVEL I : Non-water carriage toilet, ex. Pit latrine, VIP and

Bored Hole latrine.

Toilet facilities requiring small amounts of water to

wash into the receiving space, ex. Water sealedlatrine

LEVEL II:

On-site toilet of water carriage type with water- sealed

(flush type) with septic tank

LEVEL III:

Water carriage type connected to sewerage system totreatment plant


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Excreta Disposal

Criteria for acceptable excreta disposalfacilities

Sanitary

Simple, cheap and easy to construct withlocal materials

Easy to maintain

With adequate protection against elementsand provides desirable privacy

Acceptable to the users


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Methods of Excreta Disposal1. Cat-hole Latrine

2. Straddle Trench Latrine

3. Sanitary Pit privy Level 1

- Pit type

- VIP

4. Bored-hole Latrine Level 1

5. Water-sealed Latrine Level 1

6. Chemical Toilet

7. Pail System

8. Overhung Latrine


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Cat-hole latrine

Simplest method

A small hole is excavatedusing any suitable

implement Not used as regular excreta

disposal facility


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Straddle Trench Latrine

A trench is dug to a depthof about 2 feet.

An improvised shovel is

used to cover theexcrement after eachdefecation.

When the trench is filled towithin 6 inches from thetop, the content is sprayedwith oil and covered with

soil and compacted.


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Pit Privy

A pit is dug to a depth of4 6 feet.

A floor cover at the top of

the pit is providedtogether with a riser, seatand self-closing lid allmade in as fly tight as

possible.

A vent is provided with flyscreen


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Contents of Pit Privy

People use old newspapers for anal cleansing


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Ventilated Improved Pit
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Bored-hole Latrine

Deep holes bored into theearth with mechanical ormanual earth-boring

equipment. The hole is provided at the

top with a cover.

Foot rest are sometimesprovided to facilitatesquatting.


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Chemical Toilet

Utilizes the principle ofliquefaction of organic matterusing caustic soda (sodium

hydroxide) to liquefy the fecalmaterial and destroy bacteria.

After several months ofoperation, the liquefied matter

together with the spentchemicals are removed anddrained.


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Pail System

Also known as Box andCan Privy or BucketLatrine

Regular removal anddisposal of waste in asanitary manner.

Burial of contents atleast 12 inches from theground, to preventaccess to flies or escape

of adult flies.


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Overhung Latrine

Consists of asuperstructure providedwith latrine floor on top of

wooden piles above thewater.

The disposal of humanwastes consists essentially

of defecation into the water.

Unsanitary


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Sanitary Sewage

Liquid or Wet Systems, Septic Tank

Typical for human waste in settings where there ispiped, household water supply and sanitary waste

disposal using water. About 99.9% water and 0.10% solids

Typically consists of washing water, feces, urine,

laundry waste and other material which goes downdrains and toilets from households and industry.


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Septic Systems


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Septic Tank System

Wet system with collectioninto a subsurface tank,separation (settling) andanaerobic digestion ofsolids and discharge of

liquid effluent viaperforated pipes intosubsurface soil.

Widely used in developedand developing countries.

Often fail (eventually) dueto poor site conditions,poor installation andobstruction.


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Problems encountered using communal

toilets or public toilets:1) No dedicated service providers2) Due to lack of running water and a situation of

poor water availability people come only witha mug of water for anal cleansing but notflushing.

3) No lighting facilities lead to poor usage by

women.4) When septic tank is filled up it is not emptied

quickly and hence usage goes down.

These situations lead to open defecation.


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Greywater

Other wastewater from human activity

Not directly from human feces and urine

Wastewater from washing, bathing, etc

Treatment and reuse for irrigation and ground water

recharge

Greywater contains some P (from detergents) but

little N


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of no major (or less) hygienic concern/risk volumetrically the largest portion of wastewater

contains almost no (or less) nutrients (simpler

treatment)

may contain spent washing powders etc.

3. greywater

less hygienically critical (less risk)

contains the largest proportion of nutrients

available to plants

may contain hormones or medical residues

2. urine

hygienically critical (high risk) consists of organics, nutrients and trace elements

improves soil quality and increase its water

retention capacity

1. feces

characteristic

Characteristics of Human Wastes


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Ecological SanitationEcosan

Treats human excreta as a beneficial resource

Excreta are confined and processed on site until they

are free of pathogenic (disease-causing) organisms

Sanitized excreta are then recycled by using them foragricultural purposes.

Key features of ecosan:

Prevent pollution and disease caused by humanexcreta

Manage human excreta as a resource rather than as awaste product

Recover and recycle water and nutrients


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Guiding principle for fertilisation with ecosanproducts

We are fertilising thesoil, not the plant!

Ecosan products not to

be used on plantsdirectly but on the soil in

which the plants are

grown

Urine is applied in afurrow about 10 cm.

away from the plants


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Role of feces as an organicfertiliser

High concentrations of P and K

Organic matter is beneficial because: Improves soil structure

Increases the water-holding capacity and ion-buffering capacity of the soil

Supports soil microorganisms by serving asan energy source

Avoid feces as fertiliser for growingvegetables which are eaten raw


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Visual evidence for agricultural benefitsof ecosan products

urinefaeces & urine none

compostimproved soil

untreated soil

after one week without waterMaize (corn)

Source: GTZ presentations


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Source: Morgan (2007)

without ecosanproducts

with ecosanproducts

The dark green colour comes from more nitrogen uptake


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Increased yield for maize (corn) with ecosan products

Source: Morgan (2007)


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Hormones and pharmaceuticalresidues in ecosan products (mainly

urine) are not really a problem for

reuse because

Vegetation and soil microbes can degradehormones and pharmaceuticals

It is far better to recycle urine and faeces (withtheir hormones and pharmaceuticals) to arableland than to flush them into recipient waters

Urine of hospitals is not recommended to beused in agriculture.


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What if people are still really worried about eatingfood fertilised with human excreta?

You can use human excreta also on othertypes of crops, which are not eaten byhumans, e.g.

Flowers

Potted plants

Fibre-producing plants (e.g. hemp)

Oil-producing plants, e.g. olive trees

Trees


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Sewage Treatment Systems

Subject sewage to physical, biological andchemical treatment processes Separate settable solids from remaining liquid

Biologically degrade ands stabilize organic

matter Biologically reduce pathogens

Physically and chemically disinfect pathogens

Oxidize and stabilize non-settleable organic

matter and nitrogen in the remaining liquid Or denitrify (biologically convert nitrogen to N2

gas)


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Sewage Treatment

Physical and biological treatment


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direct injection of liquid fertiliser

dried faeces - soil amelioration)

irrigation urban agriculture

composting with organic waste

Agricultural Use

urban agriculture


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Aquaculture Wastewater treatment by aquatic plants and fish with

nutrient recyling by human consumption Offers high quality protein at low cost

Predominantly in Asian countries

Fish production of 1-6 tons/year achieved

tilapia

carp
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Advanced (Tertiary) Sewage Treatment

Uses physical and chemical processes

Removes nitrate and phosphateExpensive

Not widely used


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Refuse Disposal

General term applied to solid and

semi-solid waste materials other

than human excreta.


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Solid Wastes include

Garbage (food wastes)

Rubbish ( paper, plastics, wood, metal, throw

away containers, glass).

Demolition products (bricks, masonry, pipes).

Sewage treatment residue (sludge and solids

from the coarse screening of domesticsewage).

Dead animals, manure, other discarded materials.


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Paper: 50%

S f lid


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Sources of solid wastes :

Street refuse : collected by street cleaning service or

scavenging, such as leaves, straw, paper, animal

droppings.

Market refuge: contains putrid vegetables and animal

matter.

Stable and cowshed refuse.

Industrial refuse: contains wastes ranging from completely

inert materials to highly toxic and explosive compounds.

Domestic refuse: contains ash, rubbish and garbage.


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Solid waste if accumulated anywhere is

a health hazard because :

It decomposes and favors fly breeding.

It attracts rodents and vermin.

Possibility of water and soil pollution.

Unsightly appearance and bad odors.

Solid waste accumulation increases chances of

vector borne diseases.


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Storage of solid waste:


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Home Refuse Disposal Methods

Composting

Burning

Feeding to animals


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Composting

Method of combined disposal of

refuse and night soil. It is a process

of nature where organic matterbreaks down under bacterial actionresulting in formation of relatively

stable humus.


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Composting The principal by product when

refuse and night soil is mixedare CO2, water and heat.

The heat produced is 60C or

higher over a period of severaldays which destroys eggs andlarvae of flies, weed seeds andpathogenic agents.

Compost is a very good soilbuilder and has major plantnutrients.


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Burning

Involves open burning inthe ground or drum

Prohibited because burning

household waste releasetoxic substance known asdioxins


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Feeding to animals

Left-over foods can bemade use by feeding topigs, chicken, other

poultry and livestock.


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Collection of community solid wastes:

House to house collection is the best method thendispose thru the following principal methods:

Dumping

Controlled Tipping or Sanitary Land Fill

Incineration


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Dumping : Easy method of disposal of dry solid

waste. Land reclamation is often done by this

method. Refuse decreases considerably in volume

due to bacterial action and is gradually converted to

humus.

Drawbacks of open dumping are:

Refuse is exposed to flies and rodents.

Source of foul smell and unsightly appearance.

Loose refuse is dispersed by the action of wind.

Drainage from dumps contributes to pollution

of surface and ground water.


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Controlled Tipping:

Most satisfactory method where suitable landis available.

Solid waste is placed in a trench, compacted

and covered with earth at the end of theworking day. Require impermeable barriers to stop escape

of leaches: can cause problem by

overflow Gases produced by decomposing garbage

needs venting


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Controlled tipping is of two types:

Trench method: Long trench 2 3 mdeep and 4 12 m wide is dug. Refuseis compacted and covered withexcavated earth.

Area method: Used for filling land

depressions, unused quarries and claypits.


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Why controlled tipping is a good method?

Chemical, bacteriological and physical changesoccur in buried refuse.

Temp. rises to over 60 degrees within 7 days and

kills all the pathogens and helps indecomposition.

Cools down in 2 3 weeks and within 4 - months

complete decomposition of organic matter takesplace.


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Incineration

Adv:

- Refuse is disposed offhygienically

- Preferred method for hospitalrefuse

- Solves space problem but.

Disadv:

- Produces toxic gases- Expensive


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