The world is facing unprecedented humanitarian needs. Today’s humanitarian crisis tend to be greater in number, often in urban settings, longer in duration and broader in regional impact. They generate human sufferings on a greater scale, disrupt essential services, such as water supply or sanitation and put health of large population at risk. Engineers and technical specialists in water, sanitation, energy, environment, and in other related fields play a vital role to respond to these challenges and growing needs. In the humanitarian sector, they are called the public health engineers and today they are increasingly needed! Why public health engineering matters so much in humanitarian crises? And how its related activities are carrying out in such complex environment? This is what this MOOC is all about! The EPFL, EAWAG-SANDEC and ICRC have decided to partner to guide you through this introduction to the fascinating field of public health engineering in humanitarian contexts.
Water Distribution, Transport & User safety
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From the course by École Polytechnique Fédérale de Lausanne
Introduction to Public Health Engineering in Humanitarian Contexts
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École Polytechnique Fédérale de Lausanne
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From the lesson
WATER SUPPLY SYSTEMS
The week does a review of water technologies commonly used from the source to the distribution point. We discuss some pros and cons of different water systems that may be encountered in humanitarian contexts.
Meet the Instructors
Christoph LüthiDr.
Sanitation, Water and Solid Waste for Development / Eawag
Javier Cordoba
Water & Habitat Unit / ICRC
Previously, we covered functional groups from source to treatment.
Today, I would like to talk in more detail about the last two functional groups,
distribution and transport, as well as user safety.
We will get familiar with the water transport and
distribution systems in the developmental and emergency context.
The use of safety aspects will be considered only in regard to storage.
If you're interested to find out more about household water treatment,
please refer to the Eawag's online course on household water treatment and safe storage.
Transport of water in jerrycan is a reality for many rural and urban families.
Depending on the location of the water source,
it requires often a lot of time,
which can be used for other activities.
In areas where water sources are located at longer distances,
other water distribution options should be considered first.
Transport of jerrycans filled with safe water to home
by water kiosk providers can be costly but in general,
adequate option in case of water in jerrycans are disinfected and safely sealed.
Usually, this is not the case,
and the duration of water quality can be expected during transport and during use.
Chlorination of jerrycans as a part of
water collection can be an option to improve the situation.
Water vendors range from individuals who carry water in containers, pushcarts,
or bicycles or delivered in jerrycans with carts driven by animals or by trucks.
Reselling of water can be as a formal,
so water trucks managed by utilities or communities or informal,
such as individuals buying water or fetching it at
a source and carrying it to people's home and reselling it at high price.
Water vendors often operate as an extension of public supply in open areas,
performing a service to fill the gap between demand and supply.
In rural areas, high distance to
water sources often is a driving force for water vendors.
High price and water as a network,
water kiosks or borehole is often the drawback.
On this picture, water kiosk delivers water to household as a part of the services.
Water tankering is still used in
remote rural settings without access to adequate water sources.
Urban and peri-urban areas without distribution networks or as
an emergency water supply when other adequate water sources are not available.
In all cases, it is expensive,
not easy to organize and should be avoided whenever it is possible.
If water is not chlorinated,
water quality is likely to deteriorate during transport and tankering of water from
contaminated water sources can support spreading of
diseases in a large areas result in a very short time.
Thus, chlorination of tankered water as well as shock chlorination of
the tankers in times of disease outbreaks is highly recommended.
It helps that known volume and water source,
as well as mixing during transport, make chlorination of tankered water rather easy.
Water distribution systems transport water from
the water source or water treatment plant to the point where it is delivered or used,
such as community standpipe,
yard connection, or household connection.
It is the most desired and convenient way of delivering water to consumers.
It is also usually a safer way as contamination likely to be lower
than in case of transporting water by jerrycan or a truck.
Water demand in community distribution systems varies during the day.
Water consumption is highest during the hours it is used for personal hygiene,
washing, and cooking and is lowest at night.
This variations need to be addressed by water storage or pump control mechanisms.
In small community water supply,
the option with a storage reservoir is preferred,
especially considering that electric power or diesel supply is usually unreliable.
Storage reservoirs accumulate water during nighttime or when
energy is available and supplied during peak water demand hours.
The pressure of at least 5 to 10 meters of
water column is needed to protect water in network
from ingress of polluted seepage water and assure sufficient pressure in the taps,
intermittent supply, needs for deterioration of water quality
as well There are two types of community distribution networks: branched
network consisting of one of few mains which separate in
number of dead end connections and looped or
grid configuration which consist of one or few main loops
or rings from each water is conveyed to a secondary loops and branches.
Branched networks are simple to design and easier to install than looped networks.
Looped networks require a number of interconnected pipes,
valves and special parts and are more complex and expensive than branched networks.
Looped networks improve, however,
the hydraulics of the system and are generally more reliable.
Water can be supplied from different direction,
which can be important when one of the loops needs to be maintained.
Pressure variations are reduced and accumulation of sediments and
risk of microbial contamination due to stagnation of water are reduced as well.
Large scale distribution is basically a very complex loop to a mixed network.
They should be designed and constructed in a way that dead ends are eliminated or
designed in a way that flushing is possible, prevent cross-connections,
prevent unauthorized access, allow adequate disinfection,
and ensures that water system capacity sufficient to meet
domestic demand and other users connected to the network,
such as enterprises, public organizations,
fire protection, and others.
The planning design and construction requires higher level of expertise,
especially when multi-source systems are needed and requires huge investments.
Rehabilitation of a large scale distribution network is complex,
but it is being done more and more often,
also in emergencies as conflicts frequently
affect urban areas now becoming more often protracted.
Nearly 80 to 85 percent of costs of water supply of
a city is used in the distribution network.
Both the consumption at households connected to a centralized water system,
this multiple taps and often a flush toilet varies between 100 and 400 liter per
person per day and is considerably higher than household collecting water at the taps,
wells, or other decentralized sources without household connection.
This leads also to a considerably higher water wastage.
The pipe breakdowns and interruptions are common problems usually
lead into their contamination due to zero or
negative pressure and depletion of the chlorine concentration to zero.
People with intermittent supply tend to store water at home in containers,
which are not necessarily safe.
Water storage tanks are meant to ensure that
sufficient reserve of water is available when needed.
Usually, storage tanks are installed as a part of
a water supply system to cover for breakdowns in water supply,
balance peak demand, ensure adequate supply of water treatment processes,
or maintain pressure in the distribution system.
Oxfam water storage tanks are circular tanks built from
corrugated iron sheets and use synthetic rubber liner tank as you can see on the picture.
Also flexible collapsible tanks are often used to store water in an emergency setting.
Water storage is also used at the user-level at home.
Large storage water containers are often used by
households relying on tankers for intermittent water supply.
Smaller storage containers are placed in or around households to store water
carried from the source or collected through small rainwater harvesting system.
The best water treatment and supply system cannot prevent
health risks before the storage at home becomes contaminated.
Taps to reduce contact of water with hands,
as well as lids, help to reduce negative effects in small household tanks.
A proper design in lids,
as well as periodic cleaning or disinfection,
are required for larger household water storage installations as well.
If water is of bad quality or has been contaminated during transport,
household water treatment might be an option.
Eawag's online course in household water treatment
covers this in detail and we will discuss this further.
So to summarize, during this lecture,
we have discussed different distribution and storage options.
One of the options is transporting water in the jerrycans.
This might not be the most preferred option, but it is very,
very common where contamination of jerrycans
during transport and storage is a large problem,
which might be addressed with chlorination.
In areas without distribution networks and reliable groundwater sources,
water tankering is used.
It should, however, be considered as only and intermediate solution
or an immediate short-term measure in an emergency and avoid whenever possible.
Distribution networks are most convenient ways of transporting water to consumers.
These are complex systems require lots of engineering,
management, and high investments.
Water consumption and wastage are considerably higher.
However, rehabilitation of the complex distribution networks
is more and more frequently needed also in emergency,
as are conflicts are getting more urban and protracted.
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