Naked Science Forum

Non Life Sciences => Technology => Topic started by: guest45734 on 27/03/2018 11:33:45

Title: What's the best way of gardening in a drought?
Post by: guest45734 on 27/03/2018 11:33:45

I am currently in South Africa for a few weeks staying near the coast. There is a water restriction in place due to the drought. The water table where I am staying is only 3 to 4 m below the surface, but is very saline due to a coastal location on a tidal estuary. Gardens are dying due to lack of water for the plants.

What would be the simplest most cost effective way of desalinating ground water sufficiently so that it can be used for irrigation on a a small scale. The temperature here is typically 25C to 35C here at the moment, could some form of evaporation and distillation be carried out, or could some form of filtration be used. Normal desalination plants for drinking water need clean sea water and filter membranes. The ground water is not clean so would block a filter membrane easily.   

Does anyone have a simple solution other than change the garden plants for salt resistant plants.

Title: Re: What's the best way of gardening in a drought?
Post by: wolfekeeper on 27/03/2018 16:34:09

Provided the humidity is low, seawater greenhouse technology might be applicable:

https://eandt.theiet.org/content/articles/2014/06/seawater-greenhouses-growing-food-in-the-worlds-driest-regions/

Basically, you wet a cardboard filter/evaporator with the saline water upwind of the plants, and let the wind blow the vapour across the plants. You cover the plants with greenhouse (possibly polythene tunnels might work).

You also collect condensation on the outside of the evaporator, and use that to water the plants.

But no, it's not simple.

Title: Re: What's the best way of gardening in a drought?
Post by: guest45734 on 28/03/2018 12:46:04

Quote from: wolfekeeper on 27/03/2018 16:34:09

Provided the humidity is low, seawater greenhouse technology might be applicable:

https://eandt.theiet.org/content/articles/2014/06/seawater-greenhouses-growing-food-in-the-worlds-driest-regions/

Basically, you wet a cardboard filter/evaporator with the saline water upwind of the plants, and let the wind blow the vapour across the plants. You cover the plants with greenhouse (possibly polythene tunnels might work).

You also collect condensation on the outside of the evaporator, and use that to water the plants.

But no, it's not simple.

Thanks for the link. Do you or anyone else have any details ref the maths involved? can these be scaled down? what type of cardboard is used on the front wall? how big are the cardboard perforations? what temperature do the condensor tubes need to be, on the other end of the tunnel?

Here is a wiki link on the process but there is not enough detail to engineer one easily. https://en.wikipedia.org/wiki/Seawater_greenhouse#Process

Edit found this link answering some of my questions. https://www.sciencedirect.com/science/article/pii/S0011916417302400?via%3Dihub