Irrigation reuse

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Irrigation reuse
We are looking for a way to reuse irrigation water that has been used to irrigate potted plants and trees.  The plants are from various vendors so the amounts of fertilizers, etc is unknown.  Our fear is that in storage we will have large algae plumes and make the water useless.  Does anyone have experience or ideas to remedy this?  We are planning to have the water pass through a bioswale but not sure of the specifics.   --- thanks 

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  1. The level of treatment would depend on the reuse/enduse that you have in mind. I agree with Steven that if you can store the runoff/excess water in a covered tank the quality shouldn't change much in storag. Knowing what you're starting with and where you want to get to is key.

    If the volumes are large you can justify spending more time and money on the solution - if the volumes are small a trial and error approach might be least cost. Feel free to message me if you want to discuss/develop details.

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    1. thanks Harry, the water is running through potted plants to go back to the same plants (what isn't absorbed or evaporates).  we were planning on tanks but when it starts to rain again we will have too much water for the storage system.  the other thought is that it will be a punch bowl of chemical fertilizers, fungicides, etc from every supplier of plants.  we can't control what they put on the plants before they arrive to the site so they are bound to be loaded with nitrogen and phosphorus, etc.  its sounding , from your two comments , that the holding area should have a cover.   I am thinking too that it should be aerated to keep it from stagnating.   question : would a bioswale mitigate the excess chemicals used?  

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      1. Theo - True, a bio swale is a very good idea if you have the space. The trick is to keep it shallow - there are some good design guides on the web but most would not be concerned about minimising evaporation, which could be an issue for you. Algal blooms could develop but so long as they are not toxic - like blue-green "algae" (which is actually a bacteria) - that should be fine. If you are concerned about toxic algae you can add a pond aerator - even a solar powered one. One thing to be careful of is to ensure the water you take out is filtered or drippers will clog. I suggest putting a coil of slotted drain pipe in the bottom of the pond and covering it with ~100mm of sand and then connecting the outlet/return pipe to that - making sure there are no spots where unfiltered water can get in. Keep an eye on the salinity - you can use a cheap hand held conductivity probe to monitor that. If you have seasonal surplus rainfall let that also flush out the bio swale to wash out the dissolved salts/chemicals. Finally, you might need to talk to your local/state government about environmental regulations/approvals - especially if the volumes are large. Let me know how you go. :)

  2. Generally, used irrigation water would have minimal residual nutrients unless the original users weren't careful about their budget.  The mix would be diverse in any case, with the final amounts in a storage tank depending on the consistency of the sources.  As a monitor it would be possible to select just the most common nutrient and measure the amounts in the collective vat periodically.  That would at least tell you if you have a real cause for concern or nothing much to worry about.

    Preventing algal "blooms" regardless of nutrient content may be easier, as they require sunlight to prosper.  Simply depriving the solution from sunlight by using covered ponds or completely closed opaque vessels would prevent any algal bloom from occurring, even in the presence of sufficient nutrients.

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    1. thanks Steven, it seems from your comments that during the rainy season everything will be so diluted that the chemicals will be less damaging.  i am still concerned about the rest of the year - we have a six month dry spell here where there is no rain water.