Can someone tell me how much Cal to use in a cisterna, say for 5000 litres of water?
I know that I have to mix it to a paste before adding and then wait a few days before drinking any water (all a bit vague) but my main question is how much to add.
Any (sound) advice much appreciated.
Thanks

Thanks for the links. Interesting and the most common is the use of Chlorine in the water. I do that at present with the tablets designed for swimming pools and a carbon filter to fix the taste. However water then goes to a septic tank (which won't like any chlorine) and plants which likewise could do without the chlorine.
This all brings me back to looking at the local traditional way of using lime, but how much?

Calcium hypochlorite (Ca(OCl)2, HTH, High Test Hypochlorite, Sentry, Perchloron, chlorinated lime, bleaching powder)

This is usually available in granular format or as non-effervescent tablets.  This is often used by military and aid agencies for large scale water treatment.  The US military uses ampoules to ease measurement of chemical needed to treat water trailers, Lyster bags, etc.  It unfortunately leaves a chalk residue that can cloud treated water and gives it a chalky taste on top of the chlorine taste.



Bleaching powder often comes in 33-37% strength and High Test Hypochlorite (HTH) comes in crystal form and has nearly 70% available chlorine.



Either a chlorination test kit is needed to titrate treatment or water can be intentionally over treated and then neutralized with a reducer.



One way to treat clear water is to first make a 1% solution of calcium hypochlorite by mixing 14 gram (one heaping tablespoon of granules) of HTH per quart (liter) of water.  Then adding 11 drops of this 1% solution can to each quart (liter) of clear water.  This produce about 5PPM chlorine, which is equivalent to 5 parts of 1% solution to 10,000 parts clear water.


5mg/L (PPM) concentrations with

Hypochlorite Granules (70% Chlorine)
Liters      Gallons      Grams
250      66      1.4
500      132      3.6
1000      264      7.1
2000      528      14.3
3000      792      21.4
5000      1320      35.7
10,000      2641      71.4


28.3 grams = 2 heaping tablespoons of granules = 1 once



Please note that HTH is highly reactive and can burn or explode if it comes in contact with reducing agents such as sodium thiosulfate, other chlorinating compounds, concentrated acids, and organic compounds such as antifreeze, oil, kerosene and gasoline.  You should never mix HTH with bleach.

Thanks for all the posts.
A couple of thoughts  ...  although bottled water for drinking is not expensive in terms of €, I would rather not use so much plastic.
And getting back to the original topic ... I take it no one has use Cal, so if and when I find out I'll post it here
Cheers

Quote:



Sorry guys, only just seen this thread. Coldalba, you seem to be worrying about the chlorine too much. It's simple to remove.


If you are using 'Activated Carbon' and not just ordinary powdered or granulated Carbon, there should not be any Chlorine left in the water at all anyway - so long as you have enough carbon and change the carbon now and then so the pores are not all blocked with contaminants.

If you are really worried about the chlorine, why not pass it though a open topped vessel with a large surface area and aerate it with a small (solar powered?) fountain? looks good and is guaranteed to remove the chlorine simply after a while simply by evaporation. this works the same way as when you fill a large bucket from a cold tap turned on full and get a strong whiff of chlorine - it's the chlorine coming out of the water you can smell.

Alternatively, pass it though a slow sand filter with an activated carbon layer incorporated. That will also do it.

Hope this helps. As a Biologist, this and sewage treatment methods, and grey water treatments, are also exactly the sort of business I'm setting up when I move over.

BTW, if you are worried about the amount of lime to use and whether it is still too high a level in the water, why not buy a 'PH meter' or some 'litmus paper', or a simple water test kit?

Please also bear in mind that putting lime into a cisterna is not the same as putting into a well where the water is continually replaced as it's used. The water in  cisternas is usually only  replaced when the levels are low. If you have too much lime in the bottom of your cisterna, then as the water level drops, the concentration of lime in the water increases. This doesn't happen with wells since the water level stays the same. Neither does it happen with chlorine since it evaporates naturally over time and so concentration drops instead of increases.



John

John,
Thank you for the very usefull information.
My concern is of water supplied from unknown sources,which at best will be agricultural water,or worse still from the river.(
What would you recommend to test for,such as radioactivity,before commencing treatment ?

Quote:


I don't think it will be too much of a problem in the septic tank, after all, the water ging into it is a small volume in relation to the tanks volume. The water in the tank will have been standing for some time and there will be plenty of time for any chlorine to evaporate and drop to very low levels. Raising the levels a bit shouldn't make much difference at all.

The lime is an option but take into account what I said earlier - AND that if there is any left in the bottom of the tank when you refill it, it will be disturbed and will  need time to settle out again before you can use the water. The time needed will be determined by various factors such as volume, depth, amount of lime present, etc. It isn't possible therefore for me to say how long will be needed. You would need to test the water before use using a test kit.

hope this helps.
John.

John
Good to hear that you think the inflow of Cl is unlkiley to limit the septic tank.
I will see what I can establish about Cal and post anything back here
Cheers
and .. our water is rainfall, and we are trying to work out how best to use it (when it comes!).