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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
http://www.notesfornurses.com/wp-content/uploads/2010/02/IDPitLatrine.pnghttp://www.notesfornurses.com/wp-content/uploads/2010/02/IDPitLatrine.png8/3/2019 Sewage and Excreta Disposal
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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
http://www.csir.co.za/rhp/state_of_rivers/state_of_umngeni_02/photos/redbreast_tilapia_800.jpghttp://www.csir.co.za/rhp/state_of_rivers/state_of_umngeni_02/photos/redbreast_tilapia_800.jpg8/3/2019 Sewage and Excreta Disposal
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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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