Topic

Waste Management

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Waste
Definition—
 Unwanted material
 Unusable /worthless material
 Substance which is discarded after primary use.
 United Nations-Wastes are materials that are not
prime products (that is products produced for the
market) for which the initial user has no further use in
terms of his/her own purposes of production,
transformation or consumption, and of which he/she
wants to dispose.
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Types of wastes
 Municipal waste - household waste, commercial waste,
and demolition waste
 Hazardous waste - industrial waste
 Biomedical waste - clinical waste
 Special hazardous waste - radioactive waste, explosive
waste, and electronic waste (e-waste)

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Types of wastes
 Human excreta (urine & faeces) – Sewage (night soil).
 Solid waste
 Industrial wastes

Waste disposal is governed by Kenya’s Public Health Act

Cap 242, Sect 126, which deals with drainage & latrines.

Each of these wastes exerts negative impact upon

specific Environmental resources, namely, soil, water,
food etc.

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NATURE OF EXCRETA & SEWAGE
 Volume of excreta and sewage produced differ from race to race and
community to community.
 The difference depends on factors such as diet, climate and state of
health.
 Individual wet faecal weight vary from 20g/day per person – 1.5 kg per
day.
 North America & Europeans produce 100 – 200 g/day, while people in
developing countries average 130 – 520 g/day.

 Vegetarians generally have higher faecal weights than other groups.

 Rural communities have considerably higher weights per person than

the town communities.

 Children, adolescents and the elderly have lower faecal output than the
others.

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SOCIAL & BIOLOGICAL PUBLIC HEALTH PROBLEMS ASSOCIATED
WITH SOCIAL
MANAGEMENT OF HUMA EXCRETA
BIOLOGICAL
1. Surrounded by many taboos e.g.
a) Bucket emptiers, considered
outcasts malodorous – having ill smell

a) Use of latrine by all

members of the family may Contains disease pathogens
not be accepted

a) Witch craft – Enemy who gets Vehicle for disease transmission

your faeces may harm you

a) Bad spirits live in the pit i.e. Many support disease carriers,
cannot use the pit because flies & mosquitos
bad spirits could kill him

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TRANSMISSION OF PATHOGENSS FROM EXCRETA
 Human excreta is the major source of diarrhea diseases
called gastro intestinal diseases;
 Direct transmission –
 This form of transmission is referred to as the Four “FS”
 Faeces – Fingers - food – Mouth
OR
 Faeces – House flies/Cockroaches - food – Mouth.

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TRANSMISSION OF PATHOGENS
FROM EXCRETA
 Indirect Transmission;
 Uncontrolled Faeces - Soil – Food – Mouth.
 Uncontrolled Faeces - Water – Food – Mouth.
 Excreta and sewage permit the breeding of certain
disease vectors
a) Certain fly vectors - musca domestica – transmits
most diarrheal illnesses
b) Culex mosquitos C.pipiens-breeding Pit-Latrines –
Filariasis (Elephantiasis)

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Stopping transmission by means of Sanitation
S
T Water
O
P
P
I
N
G
FOCUS OF
INFECTION T Protected
R Hands Host
A
N
S
M
I
S
S
I
O
N
Foods

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COLLECTION & DISPOSAL OF NIGHT SOIL

 Cardinal objective of human excreta disposal is to totally

isolate human excreta from food, water and immediate
environment at large i.e.

 To prevent contamination of surface & ground water.

 To prevent contamination of surface soil.
 To prevent accessibility of flies and animals to human
waste.
 To avoid and minimize direct handling of fresh excreta.
 To provide privacy and convenience while relieving
ourselves.
 To eliminate bad odour, which attract flies and the
unpleasant sight of areas defiled by human excreta.
 Note: Choice of particular disposal system must satisfy the
above objectives.

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Points considered prior to selecting a particular system

 Climate & nature of soil formation in a given area.

 Type of construction material availability and the cost.
 Financial capacity of the community to support a
specific excreta system disposal.
 The prevailing habits and customs of the community
i.e. awareness of the dangers of human excreta as an
imminent source of disease.
 The aptness of a particular system; to install, to use
and to replace when need

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human waste disposal systems are divided into two
types

 Non-water carriage system

 The water carriage system

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. TRANSPORT SYSTEMS NON TRANSPORT SYSTEMS

(WATER CARRIED) (NON -WATER CARRIED)

1. Flush toilet – Connected to sewer 1. Bucket latrine

line
2. Pit latrine (V I P L)
1. Flush toilet – Connected to septic
tank
3. Compost Latrine
1. Aqua Privy

Note: Flush toilets are more

expensive
80% of the cost goes to
reticulation
i.e. collection pipes network

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Rural systems
Pit latrines
 Commonly used in many parts of the developed
and developing countries.

 Shape & dimensions:

 Generally circular in shape, 80 – 120 cm in
diameter with depth varying from 2.5m – 5m or
more.
 Not less that 2.5m; otherwise would promote fly-
breeding.

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Sitting of the latrine:
 Proper location depends on several factors:-

 For greater convenience near the home minimum 6m &

maximum 50m. If too near the house it would create fly
& smell nuisance. If too far regular use is reduced.

 From Sanitary point of view which is the most important

factor, the pit should be located below the level of any
well or water source minimum distance of 20 – 30m &
on the upward or leeward side.

 1.5m above the ground water table only if the soil is

uniform or free of cracks.

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Pit Latrine
How the system works
 Flies enter via the squatting hole, lay eggs and hatch. Adults escape but are
prevented by wire mesh. They escape upward the vent because it is the only
place they see the light. They bounce back & forth until they die.
 Air-smelly air is suctioned by the outside air moving over the vent.

Advantages
 Contains the fly – hence reduces incidences of diarrhea diseases. They can be
located near the house.
 Controls the odour – hence can be located as close to the house as possible.
 If constructed according to the specifications used and maintained properly it
satisfies the basic objectives of correct excreta disposal.
 It is relatively easy and cheap to construct.
Disadvantages of a Pit latrine
 Not suitable for crowded town areas but appropriate for rural areas because
there is space.
 Cannot be constructed in – rocky areas
- areas with high H2O table.
 Sometimes act as breeding place for mosquitos particularly culex-pipiens.

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COMPOST LATRINE OR DOUBLE-VAULT LATRINE

 The term compost refers to decomposition of organic

waste such as garbage, human excreta into suitable
fertilizer. Hence it is a biological process brought
about by aerobic and anaerobic bacteria.
 Commonly used in the far east – China and Vietnam

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COMPOST LATRINE OR DOUBLE-VAULT LATRINE
Advantages;
 It prevents spread of excreta borne diseases.
 It provides compost i.e. soil fertilizer

 One compartment is used and after it is filled, the other is used. The filled one
is sealed with heavy irremovable material and left undisturbed for 6 – 9
months and then the compost is shoveled out. If correctly operated the
temperature generally reaches 60° c - 70° c and the heat destroys all the
pathogens in the excreta. A small door 30 cm by 30 cm for extracting compost
is installed and sealed off until removal of compost.

 Before use, the floor is sprinkled with ashes or soil and after use a scoop of
ashes is added to absorbs moisture and prevents sticking and to facilitates
decomposition aerobic and anaerobic.

 The filled compartment is left undisturbed for 2 – 3 months and the second
compartment is put into use.
 According to Vietnamese experience, after 45 days, all the larvae of intestinal
parasites are destroyed and the compost is ready to use as fertilizer.

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Compost Latrine

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SUB-URBAN DISPOSAL SYTEMS

• These systems can Serve higher density population

• include few of the following;-

 Aqua-privy or qua latrine
 Pour – flush toilet - a water-seal latrine
 Chemical toilet
 Bucket latrine

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Aqua Privy
 The tank is 1.20 M long , 90 cm width and 1.50 m depth
 Ideal for 10 family members
 Dislodging 4 – 6 yrs
 After each use a bucket of H2O or 4 liters used for flushing.
 Aqua-Privy literally means “Water Latrine”. The excreta is
deposited into a tank containing a fixed level of water.
 The funnel prevents flies from coming into contact with
excreta. It also minimizes the smell (nuisance odour)
 The drop pipe funnel is normally 10 cm – diameter and
descends 10 cm below the water level. As aerobic digestion
takes place in the tank, sludge settles and the liquid
effluent is discharged into seepage pit.
 Aqua-Privy is more common in communities where water
is available.

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Aqua Privy

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Aqua Privy
Advantages of Aqua Privy
 If properly constructed, operated and utilized, satisfies
the criteria for proper excreta disposal.
 Convenience – can be located as near the dwellings as
possible and can be used by all ages at night & day.
 Saves water use, without installing flush system.
DISADVANTAGES OF AQUA-PRIVY
 The initial installation cost is relatively high.
 The system constantly needs water, though minimal.
 Entails effluent & sludge removal problem.
 Requires supervision & maintenance e.g. daily
flushing, periodic desluding etc.

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Aqua Privy
Functions of Water Seal
 Controls flies and other insect vectors from coming into
contact with faeces.
 Controls/stops smell of H2S, gases from coming into the
house, hence forced to escape to escape via vent-pipe.
 After each use 3 litres of water is poured via the trap
and moves excreta to the tank. The effluent moves via
outlet “T” to an absorption seepage pit. Although the
water is used, it is not a water carriage system.

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Chemical Toilet
 The waste is deposited in the tank containing NAOH, Cresol or
Phenol and bits of crude oil solutions.
 NAOH. Caustic Soda: Break ups and sterilizers excreta.
 Phenol: Disinfects and prevents foul smell.
 Crude oil: Minimizes splashing during use.
 Once the tank is full, it is emptied via the drainage pipe and
more of the chemicals are added. Chemical toilets can be of
movable and non-movable types. Non-movables have capacities
of 500 litres and contain 10 – 15 kg – soda + 50 litres of H2O.
Movables have capacities of 40 litres.

 They are used in Aeroplanes, Boats, Trains, motor caravans or

Trailers.

 They are also used in isolated homes, construction sites etc.

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Chemical Toilet

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Chemical toilet

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Chemical Toilet

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Chemical Toilet

Advantages
 If properly suited, satisfies the criteria set for proper
human excreta disposal.

Disadvantages
 Initial installation & operational expenses.
 Corrosion – resistant tank material are expensive and
difficult to find.
 The cost of disinfectant is beyond reach by average
man.

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THE BUCKET OR PAIL LATRINE

 They are the oldest in history and generally less hygienic.

 This method is regarded temporary suitable for refugee camps, army camps and small
growing towns while permanent (sewer systems) solutions are underway.
 This type of work is an occupational health hazard, hence the workers should be
protected.
 Protective Clothing Hand gloves
Gumboots
Overall
Helmet
Musk or Respirators

 Once the bucket is removed and emptied, it should be replaced by a disinfected one.
Sanitary workers load them into carts/lorries and take them to disposal site where:-

 Compositing is done
 Burial of excreta (night soil) takes place in pits or trenches
 Dumping into sewer line

 In order to contain disease outbreaks, strict supervision is mandatory plus dedicated staff
for this unpleasant work.

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Bucket toilet

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Pail Latrine

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Health Problems associated with this system

 It is mostly likely that it would contaminate workers

and may result into disease transmission.
 Offensive odours.
 If buckets are not cleaned/washed under water
pressure and disinfected, flies become a menace.

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URBAN DISPOSAL SYSTEMS
(WATER CARRIAGE)

 The term as it implies, means water under pressure is

used to remove the excreta from the building.
Normally water carriage systems depends on the
following:-
 The installation of a piped water supply in homes.
 The installation of sanitary fittings to receive excreta
and waste water. (W. C. – Water Closet)
 The construction of a network of pipes (reticulation)
house drains, sewers etc, to collect sewage from
individual houses and convey it to the final disposal
site.
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URBAN DISPOSAL SYSTEMS (WATER CARRIAGE)
There are three major methods for disposing of human excreta.
 Septic tank system/s
 Conventional sewage disposal systems
 Natural (biological) oxidation pond systems.
These systems are the most expensive because:-
 They serve larger populations
 Sewer lines require 10 – 20L of clean water per flush.
 Require mechanical & non-mechanical treatment plant with a laboratory.
 Technical and non skilled workers.
 The sewage is made up of 99% liquid and 1% solids.
 It contains thousands and thousands of both pathogenic and non pathogenic
micro organisms.
 As one flushes, the excreta goes through the “P” or “S” trap and finally to the
treatment plant. At the plant the sewage undergoes biological decomposition
processes; by the following types of micro organisms.
 aerobic organisms – need 02
 anaerobic organisms – thrive without 02
 Facultative organisms – live in presence or absence of 02

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 FLOW DIAGRAM OF CONVENTIONAL TREATMENT PLANT
.
PRE-TREATMENT STAGE
No
A proportion of Pathogens settle in the sludge No
Large matter, rugs, babies etc. No pathogens removal.

PRIMARY SEDIMENTATION
20 – 30 % of viruses are removed
90% of bacteria in 3 – 6 hrs are removed
50 % of cysts are removed
50 – 70% of helminths are removed
30 – 50 of BOD is removed
ACTIVATED SLUDGE AND TRICKLING FILTERS
This filter is like a bed small & large gravels
Where micro-organisms attach themselves
Hence ACTIVATED SLUDGE –meaning aerobic micro
organisms
Removes:- 90 – 99 % Virus pop
80 - 99 % Cysts pop
81 - 99.9 % Indicator pop
60 – 99 % Pathogenic pop
80 – 100 % Ova pop
SECONDARY SEDIMENTATION (HUMUS TANKS)
This process is expected to achieve 94 – 100 %,BOD and
Pathogen
removal. Most of the effluent is water.

TERTIARY TREATMENT
Deals with removal of everything and some times pre-treatment
before being discharged into a stream, river or any water
bodies.

EFFLEUNT DISCHARGE

SLUDGE DIGESTION

BOD – means the O2 required to oxidize various

organic
chemicals in raw sewage e.g. Raw sewage O2
demand of 300 mg/ requires 300 mg of
oxygen

SLUDGE DRYING

SLUDGE DISPOSAL
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SLUDGE DISPOSAL (DIGESTION,
DRYING & DISPOSAL)

 All the sludge from the tanks is pumped to the heated

digesters. The heat facilitates the sludge digestion. Gases
produced and released include Methane (CH4) which
primarily is used to heat the digesters or in the incinerator
or in the laboratory. Finally it is spread out to dry and sold
to the farmers as fertilizers.
 Therefore before the effluent is discharged off, sewage
undergoes:-

 Physical Separation – removes large constituents
 Biological oxidation – decomposes giving off NH3, H2S, CO2 &
CH4 and organic acids.

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DISADVANTAGES OF THIS
 Initial installation relatively high.
SYSTEM
 Requires mechanically operated equipment.
 Foreign exchange is relatively high since all
equipments are imported.
 Maintenance problems are prone.
 Requires qualified personnel Engineers.
 Requires energy in form of Electricity.
 Does not remove as much as 90% of BOD.

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SEWAGE WASTE STABILAZATION PONDS
 In some literature, they are referred as Natural oxidation
ponds or Sewage oxidation ponds. They are the most
widely applicable, appropriate and advantageous method
of waste treatment in hot climates. They comprise of series
of shallow lakes through with the sewage flows.
 They are further divided into;
 Facultative ponds – Shallow pond O2 or no O2 by Micro.
 Anaerobic ponds – micro organism need no O2 the pond is
deeper than above.
 Maturation ponds – Both aerobic and anaerobic processes
take place.
 Aerated ponds – Slanting (steep) and deep, aerobic

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SEWAGE WASTE STABILAZATION
PONDS

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SEWAGE WASTE STABILAZATION
PONDS

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 .
ADVANTAGES OF THIS SYSTEM
 Cheapest, provides physical, chemical and biological
process with no machinery, no energy than or except the
sunlight energy.
 Efficiency – has capability of removing 99.99% of
pathogens.
 Capability of removing 90% of BoD.
 Hence gives effluent the WHO standard 40 mg/l of BoD.
 The ponds require no routine operation and can be
expanded at minimal cost.
 Saves foreign exchange, since no machinery is required and
problems of spare parts are solved or avoided.
 DISADVANTAGES
 The greatest disadvantage is that they require and take up a
lot of land. Thus a lot of 50,000 requires a pond area of 15 –
20 ha’s.

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ASEPTIC TANK (WATER CARRIED)

 Aseptic tank is a water tight settling system.

 It is suitable for suburban residential areas, institutions –
Schools, Health Centres Etc.
 It is appropriate for low density areas, ˜100 pers. Per hectare.
 Most have capacity of 500 gallons (2000 litres), hence ideal for a
family of 5 and needs desludging after every 3 years.
FUNCTIONS OF A SEPTIC TANK
 Serves as a biological (aerobic) stabilization chamber.
 A settling chamber for both solids (sludge) and grease (scum).
Advantages of the system
 Releases effluent with few faecal solids.
 Pathogens are reduced to minimal levels.
Problem/disadvantage:
 If desludging is not done in time, it back flows to the house.
Caution :
 Efficiency of anaerobes is altered if toxic chemicals are flushed
in. Also temp & PH flacuation kill the anaerobes.

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Aseptic tank

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