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The Water Network research team has consolidated an answer to the above question. 
Further input from members is welcome and appreciated.   
 

Cholera is an infection of the small intestine due to the Vibrio cholera bacterium . It causes acute diarrhoea and in some cases vomiting and muscle cramping. Symptoms can vary from none, mild to severe.

Cholera causes dehydration and electrolyte imbalance which can have severe consequences – researchers estimate that between 21.000 and 143.000 of people die due to cholera every year, while 1.3 to 4 million get infected.

The incubation period is from a few hours to 5 days so the disease can spread rapidly.

Areas especially prone to risk are slums without proper infrastructure, camps for refugees and disaster-struck areas without proper sanitation and hygiene.

Cholera is often caused by consuming water which contains faecal matter or improper hygiene.

Groundwater and wells can easily get contaminated if open defecation is practised or if pit latrines are too close to the well. Pit latrines and surface and ground water should be as far away as possible. It is recommended that the well is at least 30 m away from the pit latrine.

Also, you are advised to check if the septic system is malfunctioning , if the area has one, since this might be causing the outbreaks.

To prevent cholera outbreaks it is important to highlight hand-washing since some people can be asymptomatic but contagious.

Furthermore, cholera can spread by food since bacteria multiplies faster on food than in water. Safe food chain should be promoted.

Disinfecting a well on a regular basis to prevent a cholera outbreak before it happens is inefficient.

We suggest you train the community health workers to teach the locals about the importance of hygiene – handwashing and the secure food chain as well as how do build sanitation facilities and toilets.

Disinfecting the well as a method of cholera outbreak prevention is not a good method since the amount of water in the well may vary so the dose of the substance used for disinfection varies and would need to be calculated every time.

Additionally, after taking out a portion of treated water, it is replaced with untreated water and mixed with the treated one.

Chlorination is the most efficient method for disinfecting a well if cholera has already been detected in a water source.

It is important to stress chlorine does not kill all the pathogens, but it successfully gets rid of cholera.  

It is advised to treat a well (or another contaminated water source) with shock-chlorination after cholera has already been detected.

Chlorination is a method of disinfecting a water well with regular household bleach or chlorine.

The chlorine is released immediately and residual chlorine is an indicator of whether the water is safe to drink.

Free residual chlorine of about 0.5 mg/l is advisable.

Shock chlorination is NOT a recommended method for treating recurring bacteria problems.

Shock chlorination should be a "one time only" occurrence.

Levels of chlorine in water will be high after shock chlorination. Therefore, it is not recommended for drinking and an alternative source should be provided. The treatment should last for 12 to 24 hours and in that period, water should not be used.

How much chlorine should be used depends on the amount of water in the well, which will depend on the volume of water in the well (depth of the water * well surface).

The amount of chlorine needed increases with the turbidity of water.

If water is visibly cloudy, the chances of it containing a great number of bacteria is bigger. Cloudiness occurs due to suspended organic and/or inorganic matter.

Chlorine readily reacts with all organic matter, cloudy, turbid water will consume and more chlorine than clear water.

To overcome this problem without increasing the chlorine dose, the water should be boiled or filtered, or alternatively given enough time so that the suspended matter settles.

After chlorination, the water should not be used for 30 minutes.

Chlorinated water may not be too palatable.

Chlorination becomes less efficient with lower temperatures!

Furthermore, recontamination can easily occur – as soon as the water comes in contact with the bacteria, e.g. someone carrying the disease touches the water.

Some of our alternative suggestions:

Boiling water may be impractical or unavailable so it may not be the best solution. However, we would like to state that boiling water will get rid of cholera bacteria.

If possible, storing water in a tank and treating it with chlorine would be a practical way to solve your problem since the volume of water can be precisely determined so the chlorine dose can be exactly calculated.
Consider using a product with continuously releases chlorine and maintains the chlorine level.

Train your community health workers to teach the locals to disinfect the water at household level . They should use regular bleach which is inexpensive. This will be much more efficient and economical than treating the wellwater.

Chlorine is harmful in high doses, but doses used for disinfection (0.5 mg/l) are safe. 


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