Basic disinfection of potable water in 3rd world 1

[brianslater]

Help
I'm not a water expert, just a humble engineer working on the borders of Laos/cambodia. We have a simple rain water harvesting system collecting into 5000l cement jars - a long established practice. However we do get outbreaks of jungle belly which I believe is due to poor management of the jars (I smelled and tasted the water). They dont practice roof flushing of first run off (for 10 mins say). we have a lot of birds and worse, the jungle chickens. they dont have effective covers over the jars, they dont flush out the gutters (not easy), we have a lot of trees and leaves.

It seemed to me that 4 drops of household bleach (sodium hypochlorite 5%vv) per litre would help sanitise the water but I cant find anywhere on the net that admits this as an ok practice. Do you see any problem with this?
Once the water is disinfected it should stay that way (assuming the covers are in place and no new rain arrives. After a week or so the chlorin will have gone anyway.

If this is ok, why dont they use this in Bangladesh, say?
Its cheap and cheerful. All this pious advice about boiling water for 15mins is of no use when you dont have firewood.

Secondly I was proposing to use a simple form of sand filter for the local pond/river water which is sometimes available, mainly to remove turbidity and vegetable matter, then dose with bleach. Any comments on this

Please excuse my ignorance if I am stating the obvious here. Its very frustrating to read the learned dissertations from 3rd World water.org to find they have told you nothing useful

Your guidance may reduce the incidence of child jungle belly, which I also get sometimes.

 

[BRIS]

It is a long time since I used bleach as a disinfectant in Sudan. I recall using 6 drops of houshold bleach per gallon of water as the rule of thumb. (Houshold bleach contains about 5% free chlorine (Sodium hyperchlorite). Industrial bleach may contain 15% and will require only 2 drops. The container needs to be shaken to give adequate contact. I think the danger is if your water includes rotting vegetation chlorination may end up producing toxins but I am no expert. I can only say that we used bleach in Sudan and as far as I can recall it did not have an adverse health affect on the local population.


However, I would suggest UV disinfection using clear plastic bottles is a safer alternative. Stand the water in sunlight for 24 hours before it is used.

Brian

 

[KRSServices]

The bleach available here is 12%.

I would use it to disinfect the containers. I have never used it to actually disinfect water per se, but if others have used it the basic principals would remain the same. However, this would be subject to the cleanliness of the water in the first place. If there is a high organic loading (rotting vegetation) then in the long term, you could be creating more problems by the toxic compounds resulting from the chlorine and the organic reactions. I disinfect my motorhome system annually with bleach and water, as well as swabbing valves and pipe repairs in water distribution systems, and therefore have direct knowledge of it's application.

You should ensure the vessels are meticulously cleaned and disinfected. Splash and scrub them with the bleach, if it's plentiful. The water should be as clean (even filtered) as possible to remove as much undesirables as possible, given your circimstances.

Then add the drops of bleach to the collected rainwater in the cleaned and disinfected vessels. I have never added bleach to water to disinfect and provide some residual chlorine and therefore have no idea as to how much to use. I do know however, that some bleach contains "fresheners, whiteners and other types of fragrances and soaps" and those are not recommended for usage in a consumable "potable" system.

KRS Services

http://www.krs-services.com

 

[cvg]

try the following website:

http://www.healthplanning.gov.bc.ca/hlthfile/hfile49b.html

 

[KRSServices]

cvg,

Very, very good website....thanks for your reply to this thread. And I stand corrected...the bleach here is 4.5%, not 12%.

The BC government finally did provide some useful info....LOL.

KRS Services

http://www.krs-services.com

 

[brianslater]

Hi guys
Many thanks for your inputs, also agree the site is vg and down to earth, no bs!
I would consider using a sand filter to remove obvious vegetable matter and turbidity and have read up on the effect of bleach and the production of THMs trihalomethanes
Rain water harvesting does not normally suffer from this unless overhanging leaves prevail. Ther is the problem of guttering however which never gets cleaned?

The second water source comes from ponds which are excavated to provide high ground, 250mm above the paddy field floods. These are often used as fish ponds to raise catfish varieties. I believe this water could also be made potable with sand and bleach. However, big warning here, you must keep ducks away from the water, they are serious polluters with some unpleasant parasites in their faeces.

What I cant understand is why these simple remedies are not recommended as reasonable practice under the prevailing circumstances? I have spent several days searching the net on this subject and come up against a brick wall of pontificating self serving academicos - if I may be so blunt

Not an ounce of use to the average poor family with chronic diarhheoa from poor water quality. Im in the swamps of thailand at the moment, relatively benign, but my time in Nigeria was a mightmare.

 

[dhdoyle]

> What I cant understand is why these simple remedies are
> not recommended as reasonable practice under the
> prevailing circumstances?

Yeah, I can understand that...

If I recall correctly, the MIOX process (

http://www.miox.com)

was developed as a low-tech, expedient purification process. I can't find a reference, but I recall something about the U.N. or W.H.O. testing the method (maybe not the brand) for exactly your type of locale. They added table salt to a bucket of water and applied a small electrical current to disassociate the sodium chloride to produce "mixed oxidizers". They mentioned that you can use a solar panel, generator, or car battery to produce the required current.

The bucket of water becomes a stock solution that is then mixed in to untreated water. If I have some more time, I might be able to track this down further.

 

[brianslater]

Hi DHD
Thanks for the tip, I hadnt heard of that process. But doesnt it further reinforce my point about simple expedients and why are these not commonly recommended. I am really puzzled about that.Household bleach is readily available and cheap here, but the table salt and car battery is an even more basic idea (of course a car battery is not suitable for deep discharges, even a new one will rapidly deteriorate and lose capacity - been there done that). but the solar panel is a possibility, at a price. need to find out some engineering details like how much power to disinfect a litre , what proportions of salt to water say 3%, probably not critical.
They mostly collect rainwater from their roofs here. I am working on a tilting collection pipe that will automatically dump the first 5 mins of rainwater. Then the gutters need a steeper fall so as to wash out leaves. Simple but would reduce water contamination. Leave in rainwater jars dont do well with added chlorine.

 

[BRIS]

Brian

I guess that you are looking in the wrong places. There is a whole Appropriate Technology Industry out there where low cost appropriate water supply and treatment systems are discussed.

Try sites such as

http://www.researchinformation.co.uk/apte.php#vol29no1

http://www.lboro.ac.uk/departments/cv/wedc/specialist-activities/ws/water-supply.htm

http://www.itdg.org

You should find the contacts are very keen to exchange ideas with you.

brian

 

[BRIS]

Also

http://www.itdg.org/html/technical_enquiries/docs/rainwater_harvesting.pdf

 

[dhdoyle]

So Bris said:
> I guess that you are looking in the wrong places

You might be right. It sounds like brianslater is actually looking for an improvised / field-expedient / survival / type of technology, rather than a village system that might build on some existing infrastructure (like power)

If I look at his problem from that perspective, iodine might be a better treatment chemical. Its residual persists a litte longer and it doesn't seem to be as effected by turbidity and organics (leaf litter, etc.).

US Army FM 3-05.70 (Chapter 6- water procurment)

http://www.adtdl.army.mil/cgi-bin/atdl.dll/fm/3-05.70/ch6.htm

US Center for Disease Control (CDC)- Article on water disinfection and containter handling in 3rd-world countries.

http://www.cdc.gov/safewater/pub/pub/mintz_e.htm

 

[saxon]

Brian, Sounds like an old rainwater/cistern system. This system has been in use for thousands of years and are still used in some rural areas here in the States. As in any potable water system you'ree running up against the problem of attention to and a fastidiousness in regards to cleanliness and hygeine. Welcome to the Third World, I know places where the water supply doubles as the sanitary sewer and everyone wonders why Typhus, Cholera, & Dysentary run rampant. A little hygiene goes a long way. In this type of system, the cleanliness of the collection, transmission, and storage is of the outmost importance.

My grandfather had a system that utilised a manual preflush dump, Organic debris screening prior to the cistern (made out of window screens), and final pump out filtration utilizing flannel cloth and homemade powdered charcoal. In addition, the system was inspected and cleaned once a month. It worked just fine, and no one every got sick.

When it comes to water purification there are four process employed, location of a clean source, chemical treatment, filtration, heat. Under primiteve conditions, normally chemically treatment is out of the question. That leave filtration and heat. The heat method is highly recomended because it destroys bacterial organisms that cause the diseases mentioned above. Thats why every one recomennds boiling everything. If it can't be boiled, bring it to 180F and hold it there for 5 to 10 min..

Hope this helps.
saxon

 

[bimr]

One caution regarding the use of bleach is that there may be impurities in the bleach. Bleach is generally an industrial product, not a potable water product.
See the attached:

http://www.odysseymanufacturing.com/filtertest.htm

Here is a link on solar water treatment:

http://www.lboro.ac.uk/wedc/papers/25/310.pdf

 

[supunya]

Hi Brianslater

if you like to dose household bleach, you'd better use bleaching powder (containing ~ 60 % available Cl2) that is sold in Thailand. i visited 3 waterworks in combodia, they ordered from Thailand. your problem is, it's sold in 40 or 50 Kg package. too much for your demand.
i heard about slow sand filter that one applied for rainwater cistern in rural area too, but don't have details. you may get idea.

 

[brianslater]

Hi Bris
I checked out the first 3 links but these are largely self serving, the 4th one was a complet pdf doc on rainwater harvesting, looks very good, will read it in depth.

In my humble defence, I would say that my first port of call was the intermediate/alternative technology searches, but I found these largely frustrating. They were more concerned with puffing themsleves rather than offering tangible info. Many of these UK university sites seem to be like that, always looking for research grants etc. Not much use to me where I am with my slow inet link.
So I stumbled on this site which I guess is largely patronised by engineering professionals rather than academics. In praise of this site, I got more mentoring in a few days that the several weeks I spent on these other searches. My experiences with conversing with academics is not good and has not been productive.

rgds

brian

 

[brianslater]

Hi DHD

I really enjoyed the US army emergency water tract, very down to earth. just the kind of approach that is needed
The other CDC one I have to digest some
Thanks

brian

 

[brianslater]

Hi Bimr

I fully accept that bleach is not meant for human consumption. However, the benefits of one drop per litre of household bleach may far outweigh these concerns.
So far in my searches I have not found any evidence that this tiny proportions (ca 2ppm of CL) are at all harmful.
Will study you suggested link on bleach purification, at first glance I have never seen a fresh bottle of bleach which has anything other than a pale straw colour, indicating minimal metal ion contamination, but my searches continue.

 

[brianslater]

Hi Saxon
I agree there are some pretty nasty water supplies around - you should try Nigeria - where I was once posted.
I can picture the cistern arrangement, something simple and automatic will suffice. Cant rely on granny getting up and operating a dumper every time it starts to rain.
Its difficult enough to persuade people to keep their jar covered with a proper lid so as to stop mozzies breeding. A cap ful of bleach soon kills off any larva btw and leaves no taste.
I am curious about your hoemade powdered charcoal btw. Is it effective? how do you stop it floating?
If it is to be activated charcoal as used in professional water filters, then dont you have to heat it up in a closed vessel to 500C?

Of course the standard advice given is to boil water. Well I can say from personal experience that this is a last resort and is unreliable - shock!!
No, not that the process doesnt kill bacteria, its that the people you instruct to boil water dont do it, or lie about it - Old Nigeria hand.
In Thailand, instructions to boil drinking water are not convenient for the average rural family. They normally only have one charcoal pot going and thats for cooking rice. Its not that they couldnt have another one, its just so difficult to persuade granny to change her ways after 90 years.
Water is stored in cement jars here, 5000 litres each, usually about 6 of them will suffice an extended family for a year. They are traditionally emptied and cleaned out at the end of the dry season. I queried why they had some sludge in some of them. This started my hunt for a simple
improvement.
My first reactions are that
a) a steep gutter flow with catchment pot for leaves
b) an auto dump of the first 5 mins of rain
c) a dose of bleach at the beginning of the rainy season
d) properly fitting lids
will produce a big improvement in water quality

Another part of the problem is that pure rain water has no mineral content. This can produce calcium and related deficiencies in children. I havent seen any source of instant water hardening salts to create "spring water"

Any one any ideas?

I always remember some of the finest tap water I ever tasted was from the Holmenkollen Hotel in Oslo, Norway. It was cold, clear and sparkling, effervescent with an amazing taste. I asked the management and they told me quite modestly that it came from a mountain stream at the back of the hotel and was used as potable water.

rgds
brian

 

[BRIS]

brian

I have to agree that in many cases: "They were more concerned with puffing themselves rather than offering tangible info". . But there are some good sources of appropriate technology. It is over 20 years since I worked on rural development and provision of basic services to refugee camps in Africa (mainly Sudan) so I am out of touch but I will chase some contacts.- I understand the frustrations of steam driven internet connections.- As for boiling - it is not a solution .

keep at it - best of luck brian

 

[saxon]

brainslater, Adequate training and carry through is of vital importance, simply instructing and hoping that it is carried through is not enough. The amplification and indotrination in regards to boiling, can only be impressed on the mind when the alternatives are made real, tangible, and visible. Such that, contaminated water leads to sickness, sickness leads to death, period end of discussion. It's one of natures ways of maintaining the population carrying capacity of the land. Or in other terms, it's a form of wildlife management applied to humans. It's hard hearted but that's the way it works. Since one meal is prepared daily, the boil function needs to be accomplished at this time. Boiling enough for the next days potable uses. As to the naysayers, if done religiously, it works.

As for the powdered carbon, it was held between two layers of flannel in a wood frame.

saxon