ENGINEERING WATER DISTRIBUTION

Our Long Term Filter

 

Alongside our portable filter idea, we wanted to design another, more permanent water filter. In this section the idea of a long term filtration system is explained. Our reason for designing a long term water filtration system is that we feel it is important to allow the water usage of populations of developing countries to become more self-reliant and sustainable. Our filter will help towards this goal as it is relatively cheap to run and requires miminal manual labour. In designing an automatic filter,  we hope to ease the burden of the 500 million people in the developing world who live without access to clean water in our idea for a simple, durable, long term filter. Providing a low cost solution to water purification could help to reduce the number of deaths due to disease that are carried by water. To find out more about the different waterborne diseases, click on the page titled 'Waterborne Diseases' in the drop-down box under 'Water Filtration System'.

 

 

The filtration process

The process of our filter is listed in the steps below, however first it is good to know about the three typical branches used in effective water filtration systems:

 

Physical: screening, filtration, sedimentation, and can include boiling and distillation
Biological: carbon filters, storage to allow for bacterial breakdown
Chemical: flocculation, chlorination and can include UV radiation

 

The following steps have been decided on by studying effective existing filters and the diagram to the right demonstrates how the filter would look.

 

The steps in our water filter:

1. Screening – the water flows through a mesh screen which
   removes any big objects, e.g. plants, weeds, debris
    

2. Coagulation – If you then add aluminium sulfate to water, a
   gelatinous solutionis formed due to the water reacting with the
   bicarbonate alkalinities of the aluminum sulfate. Other chemicals
   are added to cause particles within the water to stick to each
   other (forming floc). The floc attracts dirt particles.
    

3. Sedimentation – the floc sinks to bottom and where it is removed
   .

4. Filtration - layers of gravel/sand filter out the remaining particles
   (gravel: 1 foot deep; sand: 2 and a half feet deep).
   
    

5. Disinfection - the water is now transferrred into another tank
   where chlorine and other chemicals are added to sterilise the
   water. Sterilisation works due to the chlorine attacking the lipids
   in the cell walls of the microbes and destroying the enzymes and
   structures of the cells. Also chlorine helps to keep the water clean
   until distribution. This is 90% effective.
    

6. Activated carbon - made from coconut shells (renewable
   resource).When the water flows through it removes the chlorine
   and other chemicals from step 5.
    

7. UV radiation - a special UV lamp emits UV rays at the right
   wavelength to kill off any remaining microbes. This radiation
   does this by emitting UV rays of the right wavelength to destroy
   the nucleic acid  of the bacteria or virus, thus inihibiting replication. Must use a lamp as UV light from the sun is too weak as most of it has already been absorbed by the ozone layer in the atmosphere.

 

A bucket will be placed at the bottom of the filtration system to collect the clean water.

 

 

The filtration system

 

We were initially considering a turbine in the middle of the filtration process as a way of
generating kinetic energy which could then be converted into electrical energy. This electrical energy
would then be used to help pump the next round of water to the top of the system. However, we
decided against this idea as soon as we realised that the amount of energy generated would barely
cover the energy needed to put in to get the turbine to turn (friction and air resistance being two
resistive forces). Therefore the turbine could be seen as inefficient and a waste of precious money.

 

 

We want our filtration system to be automatic so that people can get instant clean water without
having to wait for it. The clean water would first have to be transferred from a river or lake and then
pumped to a level high enough so that it can fall down through the filter due to the force of gravity. This water filter will help make people in the developing world more self-reliant and independent as they will have a way of their own to getting clean water and generating electricity. To make the filter automatic, we would need a motor to pump the lake water up to the top of the filter. However, we want to keep this filter eco-friendly and not use electricity generated by fossil fuels to do this. Due to the cancellation of our turbine idea, we have decided upon solar power.

 

The benefits of a few other renewable ways to generate electricity are outlined in another
section of this website but I will quickly go over solar power. There many advantages to solar
power as a way of generating energy, but often it is not the first go-to choice due to weather
conditions. However, in the developing part of the world, there is a lot of sun and thus a solar
panel is a great way to generate electricity. The electricity generated through a single solar
power will be enough to pump the water up to the top of filter.

 

Water Pump

We have decided to use an Archimedes screw to pump the water up from the lakes/river to the
top of the water filter as it is a reliable and efficient method for doing this. An Archimedes screw
works due to a revolving screw inside a cylinder. The screw revolves either by the use of a handle
or when it is connected to a motor.

 

We have opted for the automatic version as we want water to be constantly filtering through the
system so that clean water is always available. To keep to our eco-power promise, we will power the
motor using a solar power panel. This solar panel will also provide enough energy to power the UV
lamps as well in the final stage of the filtration process.