Water Treatment for your Wasabi Farm
No matter what type water supply you have there will be some requirement to treat the water before it is used in the wasabi farm.
The very minimum you will need is a filter for the incoming water to remove debris and other rubbish, including silt from the supply water.
The wasabi plant does not like having silt smothering its feeder roots. If the build up gets too much then the plants will die even if every other environmental parameter is OK.
If you are using a recirculating water system then you will need a filter at the water discharge end as well to remove any plant pieces that will fall from the growing plants.
Dependent on the results of your Water analysis you will need some sort of sterilisation system to remove all the living material that might cause problems. This could be ozone, Ultra violet light or even a dosing system to inject sterilising solution into the water flow.
The most important thing to remember about whatever water treatment system that you use is that the water that you allow to get to your plants must be as clean and pollution free as you can make it.
It has been for this reason that the amount of wasabi being grown in Japan (the reputed home land of Wasabi) has been reduced on an annual basis for many years. Initially, it was because of acid rain and people leaving the countryside. The latest reduction is due to the Fukushima nuclear power plant problem when a significant number of streams and rivers are now radio-actively contaminated. At one time all wasabi exports from Japan required a declaration that the product was free of radiation. That requirement has now stopped, but it shows the sensitivity of the wasabi plant to outside influences.