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Borehole wash water reuse?

We are looking at possible options for reuse of water that has been used to clean an operational borehole. The water will be high in chlorine and turbidity. Assuming that there is no legislation to cover this, and that the community is happy, is it possible to reuse this water in agriculture for human consumption? If not, any other options other than discharging into the environment? I think that treatment options for reducing the chlorine load are not economically feasible considering the large amount of water. Any thoughts?

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Depends on your community. Should not be a problem for agriculture, but for human consumption, storing and aerating the water should get rid of most of the chlorine. If stored in reservoir, suspended solids should settle.

nashalbu gravatar imagenashalbu ( 2019-04-15 17:14:24 +0100 )edit

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Have you concluded that sodium metabisulfite and sodium bisulfite are too expensive? The application can require nothing more than a bag to hold some tablets in the water stream. Otherwise discharging into a watercourse is could have fish-kill & other ecological implications.

Are the community, and all other potentially affected communities, happy after fully understanding the repercussions?

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I am a bit confused as to why the water will be chlorinated. Usually borehole development involves pumping out from the borehole with the water in the aquifer. Or are chemicals being added to develop the borehole in flow etc.?

If you are adding chlorine to achieve this it is feasible to dechlorinate. This does not have to be done by chemical dosing to a flow but can be by putting flow through a chamber with bags of sodium sulphite etc as Martin suggests.

For reuse for agriculture I would suggest de-chlorination and to reduce the suspended solids load through settlement .

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I think there should be quite a bit of scope for using the well-tried reed bed water treatment process. This link seems to provide some useful detail..

http://www.recyclingexpert.co.uk/recy...

KC

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In Zambia, there are areas where boreholes are the only source for water especially in the Southern Provinces. Instead of installing soak pits, they make animal drinking troughs. All run off goes into the animal trough and this is used for animal drinking. In some areas, small gardens are also made around some water points to improve nutrition.

In areas where water is a problem, we can not stop people from using borehole water for other uses.

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Part of your decision will depend on where the water is going to be disposed of. Going straight into a surface water stream will need higher levels of wastewater treatment than running over a vegetated surface or a shallow soak away.

You should only need the final flush of wash water for the borehole to be super chlorinated. There should still be a residual of free chlorine when the water is finally flushed out. However the initial dose should not be excessive as that would be a waste of the chemical. Chlorine is highly reactive and it will be used up once it mixes with water with organic matter in.

If you can store the wash water for a while and test it before draining it to the environment, you can ensure the chlorine has all been reacted. If the water still has free chlorine mix it with some soil and test again.

The turbidity can also be dealt with by storing the wash water for an hour or two until it looks clear. Running it through some grass will help remove any other traces of solids before discharge to the environment.

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Part of your decision will depend on where the water is going to be disposed of. Going straight into a surface water stream will need higher levels of wastewater treatment than running over a vegetated surface or a shallow soak away.

You should only need the final flush of wash water for the borehole to be super chlorinated. There should still be a residual of free chlorine when the water is finally flushed out. However the initial dose should not be excessive as that would be a waste of the chemical. Chlorine is highly reactive and it will be used up once it mixes with water with organic matter in.

If you can store the wash water for a while and test it before draining it to the environment, you can ensure the chlorine has all been reacted. If the water still has free chlorine mix it with some soil and test again.

The turbidity can also be dealt with by storing the wash water for an hour or two until it looks clear. Running it through some grass will help remove any other traces of solids before discharge to the environment.

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