Someone asked in a comment on Sylvia's latest blog post about whether, in a disaster, aquaponic water is safe to drink. Given the floods we've just copped in CO, I thought it was worth a discussion for the sake of our learning.
High nitrate levels in water, whilst absolutely fantastic for plant growth, are not safe for human consumption. The bacteria in your guts converts it to nitrites when are then converted to Methemoglobin which bonds preferentially to your blood cells instead of haemoglobin which means your blood can't transport oxygen as efficiently. The condition is called Methemoglobinemia (also known as blue baby sysndrome) and is easy to treat.
So no, I wouldn't drink water directly from an aquaponic system.
But don't be scared of the water, you would have to drink a lot of it over time to have any issue at all. If I was dying of thirst I'd still drink some. But not the greatest option
Some better options are:
- If you wanted to have emergency drinking water on had for a disaster you could definitely use the water stored in your off-gassing tanks.
- If you are really clever, and have built a sustainable greenhouse with water barrels lining the north facing wall to act as a heat exchange, that would also be a great source of emergency water supply.
Are there any other ideas for water storage?
I've gotten giardia on 4 continents from water, so its obvious I haven't spent enough time thinking about it. I keep a large supply of water purification tablets and drops for emergencies and I know how to boil water if I need to. Sometimes, though, you just have to drink the water and deal with the consequences later.
Interesting topic! My father and I have had an ongoing conversation about the safety of my AP system. He is a doctor (general practitioner) and has treated many a patient who has ingested the wrong thing. He cringes at the thought of eating veggies outta my AP system(although he has eaten them often, unawares). He insists that I be more hygienic with my AP play, because of the potential for bad bacterial growth. I argue, that I know the input, therefore my AP system is safe... I have had giardia as well, from a stream in Wyoming, No fun!
Yeah, flooding always make me think of running out of water and dying of dehydration too ;)
A tank full of aquaponics water could certainly be valuable as an emergency water supply if disaster struck, but I don't think it would be safe to drink straight out of the tank. If you really needed to drink the water in an emergency you could run it through a Berkey filter (or similar filter type) first. Berkey filters are supposed to filter down to 0.2 microns which is essentially sterile filtration. It is also supposed to reduce nitrates, but by how much is dependent on how much there was to begin with and what other contaminants are present and age of the filter. I would think that at the very least it would be safer than drinking the AP water straight out of the tank.
From what I understand, there is still too little known about AP systems to know whether any human pathogens can be transmitted. Listeria lives on the skin and in the gills of fishes so it is possible that there could be transmission of that particular nasty if the water gets on the plants (or you drink it)....recall that the Colorado melon incident had to do with Listeria. I would certainly treat aquaponic water like any other untreated water until more is known about what human pathogens can and cannot grow/survive in it and wash your produce, try to keep the fish water off the produce, don't drink the water straight out of the tank without filtering it, etc.
You could make a slow sand filter to get rid of a lot of harmful things and then put in water bottles to place in the sun for a day or so (poor man's reverse osmosis). Just for safety reasons I'd send a sample to test at the local water works before drinking though. Or maybe just pick up a bulk pack of life straws.
What an interesting topic... As Casey suggests, I'm in process of buying a couple sets of Berkey filters. Additionally, I’m trying to learn about proper chemical treatment of water as well. I'm also tinkering with a couple of 5 gallon filters using sand , different size rock/gravel and then another using charcoal just to see what the results are—but the process of getting the water tested is painful at best. My focus has been dealing with rain water collection—but if one were to get thirsty enough, it would probably be time to sacrifice the fish. Anyone have any good sources for proper water treatment?
Good point on listeria. Listeria is a type of bacteria present in soil, water and animals, and when present in meat it is killed by cooking. So I guess boiling would take care of that one.
So I was just wondering if boiling has any effect on nitrates..so I googled it, and it actually concentrates the nitrate (makes sense I guess, the volume of water is reducing).
However you can distill it (the following is from the linked paper from New Mexico State University):
Demineralization removes nitrate and all other minerals from the water. Distillation is one of the oldest, most effective types of demineralization. The distilling process has only three steps:
The nitrate and other minerals remain concentrated in the boiling tank.
So there you go. Nitrates are extremely soluble and hard to remove from water, which makes aquaponic water an A+ way to grow plants (which are 100% fine to eat by the way, and probably healthier then a lot of stuff growing in the ground), but not a great way to store drinking water unless you make a couple of preparations. I'm sure it would be pretty easy to build some sort of distillation machine. If you had a woodfired greenhouse heater or something you could probably rig something up to make use of that.
Nitrate removal from water: http://aces.nmsu.edu/pubs/_m/m-114.html
We have plans for building a GH this summer, my original system design was to have the ST buried but then the city tells us we had to be a foot above ground because we are in a flood zone. So we paid for an expensive inspector to come out and tell us we weren't in a floodzone. Now we can dig in the ground but we have to show that AP water is safe in case of leakage into the drinking water system. I would think once the water leaks out, the nitrates get mostly absorbed by the soil and is a safe level.