Gravity Fed water decontamination system for third world

As part of my final year at bournemouth, I dicided back in october to undertake the task of design and engineering a ‘Gravity Fed water decontamination system for the third world’.

At the top (attached to a tree, or roof of house/hut whatever is a water bladder, on the entry to this is a sediment filter, that basically takes out all of the dirt, etc… I want this bladder to have a life span of around 7 years, but ideally as long as possible. I have looked at PVC camping showers, and not sure how durable they would be. I was wondering if anybody had any ideas on fabrics, or materials that could be used, another idea was some sort of rubber, but i need to look into it.

Attached to the bladder is 20mm tubing that runs down to a filter capsual, which again is attached to a 40 litre bucket and lid.

Just looking for anyones input, or ideas really

You should be able to see my initial concept, but i must say things have developed since this point to quite some degree, but gives you a better idea.

All input and advice welcome


By decontaminate, are you just referring to particulates?

This isn’t for drinking, not without boiling or iodine added right?

I have done a big project on water purification in outdoor environments, and I think a bit more info is needed to understand it.

You might be able to filter out some particles, but that’s not the main issue, you need to get rid of the microbes and suchlike.

Will you boil it, becuase that is the safest way. You can also use pressure, or charcoal filter, etc. Simple gravity won’t be enough I don’t think. What is the point of having it so high?

How will they use it? Who are the users?
If this is a simple gravity fed device, how do you get the water to it? How do you clean the sediment out? Removing sediment will give the appearance of clean water, but will not make it safe to drink.

Google Lifestraw.

and - reverse osmosis.

gravity fed filtration, like in the Brita pitchers, is only for taste and odor.

okay, sorry forgot to say, in the filter capsual (that is attached to the 40 litre bucket) there is a pre-filter that retains particles above 5 microns, then an ultrafilter that retains particles above 25 Nanometers.

Yes this is for drinking water, cooking etc… and is intended to be consumed without boiling.

The hieght of the fabric funnel at the top is due to pressure head needed to achieve a flow rate roughly of 7 litres/hr.

Thanks guys

…and from undertaking research on viruses/bacteria i found the smallest virus around 30 nanometers

I am not sure but I went to a conference and an engineer was talking about a water Ionization product that works to destroy E-Coli and such.

You will have a problem with clogging almost immediately and you will have a problem with biofilms. Catching bacteria (don’t worry about viruses) in a filter only gives them a place to grow. You need to inactivate them. Iodine is cheap and works fast but there are a few other antimicrobials you can research. Good luck.

So Describe to me the user situation - It is aimed at the 3rd world I know that much. So you must bring home at least 7 litres of water, then sit around for an hour waiting for it to drip through the filter, like a coffee filter. Is that feasible?

The fine filters are a good idea, but unfortunately not enough to make it drinkable for humans. E. Coli isn’t foiled that easily.

How is it shipped to the user? Is it assembled on site, or what? Is it a special bucket? Can they just use a bucket they already have? What happens when the filter is clogged? How do you clean it?(esp. in a developing country) Can any parts be user maintained and repaired? How much does it cost? How is it better than what is already available? Have you looked at how other water filters work? Have you thought about actually making this work in real life? Like doing a trial?

I am being quite harsh I know, but it is better that I am harsh on you for a final year piece, than your professors. I am not trying to upset you, just want to make your design better.

so many projects for 3rd world lately.

My experience of third world conditions is Africa and a select middle eastern communities only.

You have to realize in these conditions weaknesses become prevalent and amplified. Also, devices continue to be used after multiple failure modes, for various reasons: lack of knowledge or understanding, no replacement parts, etc. And theft. Stuff gets stolen a lot, more than can possibly be imagined.

In this water bucket thingy I would suggest:

filters and the like with a servicable life time will never be replaced or will simply be removed and discarded.

the bag and the long tube will decay, crack and leak. They will be stolen, guaranteed.

the spigot at the bottom will break within days of first use.

the bucket lid will be used to carry corn, sorghum, etc.

the bucket may be carried around, if so it will be on a woman’s head. She will probably appreciate handles near the bottom of the bucket.

Here’s an anecdotal story. I was shown a water pipe being installed in Southern Africa bringing a natural aquifer’s water down from a low mountain several kilometers to a plain for irrigation. It would be gravity fed as pumps just wouldn’t last. The buried pipeline could be seen because of course excavated earth eventually sinks and appears different than undisturbed earth. There was great concern Massai would dig it up and steal the pipe for arrow quivers. The conclusion was to leave it as the erupting water pressure would surely kill the Massai sawing into the pipe, and his buddies would learn and warn others of the pipes bad juju. Indeed, it happened.

Thank you all for your replies to my post.

I have looked into Iodine, and found a competing product used ‘Iodine Impregnated Beads’ for the water to pass through it. I got in touch with a water chemical company, and they told me that using iodine in 3rd world countries would be a problem as they wouldnt be able to acuratly monitor the post filter removing the excess iodine.

Epic - Dont worry you havent upset me, I need these kind of questions to be asked.


I want the user to be as broad as possible, whether they are in a shanty town, on the outskirts of Joberg, or the outback of Kenya. I want this to be used by a family/community of roughly 6-8 people. (I know in reality a lot more people will use it that this).

I dint encorporate a means of transporting the water from the source to the settlement due to after research, i found that they had containers to do this.

How is it shipped to the user?

My customers are charities such as ‘Red-Cross’, ‘Oxfam’ and ‘WaterAid’. However I think there is a large opportunity selling to governments, and the U.N.

I want the product to be produced in factories in africa, cheaper labour, and cheaper transport costs. I have made the design transport friendly as the buckets are stackable, and all the other elements clip into place in the lid. The product would be dispatched by road, using trucks.

Is it assembled on site, or what?

It would be assembled for transport in factory, then shipped, then user would assemble/erect it.

Is it a special bucket? Can they just use a bucket they already have?

A ‘special’ bucket, handles encorporated, hole in bottom for tap (tap to be fitted by nut/screw (bought in)). The lid is attached by a live hinged mechanism, like that on lunchboxes etc…

What happens when the filter is clogged? How do you clean it?(esp. in a developing country)

I had planned for the filter to be hand washed in the ‘clean’ water weekly, then replacements could be given out by the charites on a 12-18 month basis.

Can any parts be user maintained and repaired?

I have tried to make all the parts easily replaceable, for example to top filter bag, the attachment to the tubing i have used some sort of clamp, that clamps the bag into place, so if the bag was to split it could be replaced by a variety of things.

How much does it cost?

New - $60-70 (to charaties, etc…)

How is it better than what is already available?

Ceramic filters, very cheap, but do not filter all virusses, and some bacteria.

BioSand filters, again very cheap, but very slow flowrate, that slows down even more after time.

LifeSaver Bottle, roughly £200 (expensive), and needs a replacement filter every 6 months (6000 litres) that cost a further £90

LifeStraw, biggest competition, but uses the iodine impreganted beads, that I was adviced against, and doesnt have a safe way of collecting the clean water.

Have you looked at how other water filters work?

Yes, I have done a lot of research into other filters, and getting to a point now, where im getting stuck, as i have been adviced away from each of them…

Have you thought about actually making this work in real life? Like doing a trial?

I would love this to actually work, I really do have a big problem with the fact that there are so many people across the world that dont have access to water, which above anything is a human right! Goverments and organisations are helping it, and last year a total of £6.2 billion was given to world water aid and sanitation, but its still hoing to take at least 30-40 years apprently to get clean water to all communities across the world.

Oh, sorry, and thank you Pier

Thanks for the input, and I hadnt thought about parts being stolen, or how they might use the lid to carry corn etc…

But how could I go about parts getting stolen?? I mean it would be a desriable product for someone who didn’t have one, but how could I encorporate a anti-theft device.

it’s a f’in tough project mate, I spent 6 months trying to develop a viable business case for something like this.

You could look into what the US military were doing i think in hurricane katrina - they had some random powder or something, can’t remember, but that could be an avenue to check out.

You know if the military use something it must be ok - kind of like the bare minimum to function you know, which is really all you need.

Once you have a way for this to work properly (or if it’s just a school project, make everyone think it works), then you should make it look more designer-y. Make it integrated smoothly, make the parts look good. RIght now it just looks like and IV bag connected to a bucket.

Make it sexy.

Yea i Know it does, this was the initial design, it has changed quite alot in terms of aesthetics yet, but nothings rendered, that image was taken back in december.

Thanks for the information on what the army did, i will look into that!

Yeah, im just starting to see that i bit off more thank i can chew. Its tough, I have 4-5 weeks till my next presentation, where I should have it basically finished, in terms of i need to know what my filter does, how it does it etc… and final design, between that presentation and the last we have to do FEA on it, and thats where i will have to work out the exact flow rate, etc…

Thanks for your input!

I hate to see you hang your hat on that filter, it will clog within 24 hours if there is no pathogen inactivation and lysing. Bacteria caught in the filter will reproduce and create a biofilm rendering the filter worthless. Do some research on biofilms, they happen quickly, lead to increased resistance and are very difficult to remove.

If you want to stick with the filter, look into bonding it with an antimicrobial. You may be able to take advantage of iodine without releasing it into the water or you can look into other things like ionic silver (although that is slow in killing pathogens).