Here in the U.S. we’re used to the idea of turning on the faucet and having unlimited quantities of clean, safe drinking water available at all times. We should definitely count our blessings. In some parts of the world people have to walk for miles each day to fetch water, water that we probably wouldn’t consider safe to drink. But it’s what they have.
Even in the United States our tap water isn’t completely pure. The Environmental Protection Agency (EPA) has rules regulating contaminants in water. Testing and compliance however is almost completely in the hands of our local utilities. If you have any concerns about your local water supply it is up to you to check up on it. If your local water utility exceeds the EPA guidelines for contaminants it is only required to inform you, by mail, within thirty days after they discover the problem. If they don’t test very often, who knows how long that might take. According to the EPA,
In 2001, one out of every four community water systems did not conduct testing or report the results for all of the monitoring required to verify the safety of their drinking water.
There are many resources on the web that discuss the various contaminants in drinking water and their possible effects on human health. I won’t go into that here. I want to concentrate on what we might find in our tap water that will have an effect on our ability to raise food.
The only water contaminants that I’m seriously concerned about in my garden are chlorine, Cl2, and sodium, Na. The EPA allows utilities to add a maximum of 4 ppm of chlorine to drinking water as a disinfectant. Now, I have no problem with that. The alternative to adding chlorine is to allow unchecked bacterial growth in the water mains. This could lead to bad results!
There are two problems with chlorine once it reaches my garden.
First, it will continue to do what it’s designed to do – kill microbes. Why is this a problem? My compost piles, the bacteria in my aquaponics water, and the microbes in my soil are major parts of my garden’s ecology. This ecology is necessary to grow high quality food.
Secondly, it is poisonous to my fish.
Back in the old days we had a simple fix for this problem. To prepare tap water for adding to an aquarium or our turtle pond my mom would fill up a suitably sized container with tap water and let it sit, uncovered, for two days. Virtually all of the chlorine in the water would simply evaporate into the air. Then it could be added without any worries about killing our aquatic creatures.
When I first started my tabletop aquaponics unit this is what I did. And boy did I have trouble. It turns out that elemental chlorine is no longer the preferred disinfectant in Pinellas county. These days the water utility is using chloramine as the disinfectant. Chloramine, a chlorine compound, is not as effective a disinfectant as straight chlorine. It is, however, more stable. It ensures that the water is delivered to all households still containing enough residual chlorine to protect from bacterial growth. It also does not react as easily with chemicals in the pipes. The EPA found that chlorine on its way to my house could form some very interesting molecules—carcinogens.
As an interesting aside, chloramine is formed by first chlorinating the water and then adding ammonia. Your mom was right when she warned you not to mix ammonia and bleach!
Once again, the problem with chloramine is that it does what it’s supposed to do. It remains stable. If you fill a bucket with tap water and let it sit for two days the chloramine does not evaporate. It is still present, ready to kill any fish or microbes it touches.
After learning this I surfed aquarium websites to discover a solution. Many aquarists use a chemical called sodium thiosulphate to neutralize chlorine and chloramine. I began to do likewise.
Warning: on a couple of aquarium forums I found references to using chloramine to help prevent or cure diseases of freshwater fish. The writers were confusing chloramine with chloramine T, a very different molecule that acts as both a mild disinfectant and as a sulfa drug. This may be used (with approval) for treating diseases. Normal chloramine isn’t good for fish.
Once I moved into my house, however, I began to have my doubts. Is this chemical an acceptable one for organic gardening? What about the fact that it neutralizes the chlorine by turning it into sodium chloride – salt? Sodium, it turns out, was something I was adding to the water. Salt isn’t good for plants.
I wasn’t the only person wondering about this. Shortly thereafter received Friendly Aquaponics newsletter #125 talking about the neutralization of chloramine. I did a little research and, by the time I had received newsletter #126 I’d found the same answer that Suzanne came up with. It was reassuring to have her validate my research.
As I go to press 🙂 newsletters 125 and 126 are not yet available online. The bottom line, however, is that vitamin C, ascorbic acid, neutralizes chlorine (including chloramine) . And ascorbic acid is on the list of chemicals that may be used with organic fruits and vegetables .
Since I’m only concerned with my backyard, that’s good enough for me. If I were trying to get organic certification I would do a lot more research!
Remember how sodium thiosulfate neutralizes the chlorine? It turns into a chloride, specifically sodium chloride, salt. There is a form of vitamin C called sodium ascorbate. Don’t use this—it also converts the chlorine into salt. The sodium-type chlorine neutralizers are popular because they work almost instantly—and salt has no effect on the pH of the water. A small amount of salt in the water doesn’t harm most fish—it may be beneficial for certain species. Remember, though, that salt isn’t good for any plants commonly grown for food.
Ascorbic acid works similarly in that it converts the chlorine into a chloride. The chloride in this case, however, is hydrogen chloride. Another name for hydrogen chloride dissolved in water is hydrochloric acid. What? Are you nuts, Rick? You’re worried about a little salt so you decide to poison your fish and plants with hydrochloric acid?
I agree that HCl isn’t a recommended additive for aquaponic water. It can, however, be easily neutralized in one of two ways. The fast way is to stir a calcium carbonate slurry into the water. Calcium carbonate, in the form of crushed oyster shell or crushed coral, is an approved substance for organic farming. In fact, I add it to my tabletop aquaponics unit to buffer the pH. The Friendlies use it for the same purpose. This converts the HCl to calcium chloride, carbon dioxide, and water.
The second way to get rid of the HCl is to wait. Almost all of it will evaporate in two days—just like chlorine.
How much ascorbic acid do I need to add to my water? That depends upon how many parts per million of chlorine it contains. Pinellas county aims to deliver 2 ppm to my faucet, but my tap water has a very strong chlorine smell. I like to play it safe and assume I’m getting 4 ppm. At that concentration I need to add 1 g of ascorbic acid to every 25 gallons of water. If I overdose on ascorbic acid it won’t really matter. Heat, sunlight, and oxygen (air) destroy it very quickly. Since I let the water sit in order to evaporate the HCl, the ascorbic acid will degrade at the same time.
Ascorbic acid can be purchased in bulk from many online retailers. A 1 pound bottle contains about 454 grams, which would be enough to treat 11,350 gallons of water. At $20 per pound, it will cost me $0.0018 per gallon. Maybe I should buy a smaller bottle.
The method I use for dosing with vitamin C is to dissolve a quarter teaspoon (about 1.25 g) in 6 tablespoons of water (3 ounces). Then I use one tablespoon of the solution in a five-gallon bucket of water. I store any unused portion in a glass bottle in the refrigerator. That way it doesn’t degrade so quickly.
God bless you all,