I have well water and it is 380ppm so I use a RO system with double DI filters to bring it down to under 8ppm and it PH is 7.0
Municipal water supplies
Many indoor gardeners are reliant on municipal water supplies and have few other options for a better quality water source. Its likely that some plant losses have and do occur as a result of some municipal water supplies, particularly in sensitive species and in water culture systems where there is no media to act as a buffer. On the other hand, many municipal water supplies are quite suitable and given that they have had organic matter and pathogens removed already, are a good deal as far as hydroponic systems go. Interestingly plants have rather different responses and requirements from a water supply than humans and this is where problems can occur. Municipal water treatment ensures that drinking water meets the World Health Organization (WHO) and EPA standards for mineral, chemical and biological contamination levels, making it generally very safe to drink and use. However, what is safe for us to drink may not be so good for plant growth, particularly when we consider many hydroponic systems are recirculating which allows build-up of unwanted contaminants in the plant root zone.
Recirculating solution culture systems such as NFT have less buffering capacity to water treatment chemical residues than organic media-based systems.
Water treatment options used by municipal suppliers change over time and hydroponic growers should be aware of the implications of these. Many years ago the main concern was the use of chlorine as a disinfection agent to destroy bacteria and human pathogens. Chlorine had the advantage in that it disinfected water effectively; however, residual chlorine in water sources, which could often be detected by smell, could be toxic to sensitive plants and where it built up in certain hydroponics systems. Also when chlorine reacts with organic matter it forms substances (trihalomethanes) which are linked to increased risk of cancer and other health problems. Chlorine was, however, quite easy to remove from water with the use of aeration or even just aging the water a few days before irrigating plants. In the 1990s it was found that some organisms such as Cryptosporidium were resistant to chlorine and the resulting health issues from this meant that drinking water regulations were changed and alternative disinfection methods began to be used. These included use of ozone and UV light, chloramines (chlorine plus ammonia) and chlorine dioxide.
Filtration, flocculation, settling, UV and ozone used for water supply treatment are non-problematic as far as hydroponic systems go, as they leave no residue and are effective. However, use of chloramines and some of the other chemicals by municipal water treatment plants may still pose problems where high levels are regularly dosed into water supplies. Chloramines are much more persistent than chlorine and take a lot longer to dissipate from treated water, so gardeners who are concerned can use a couple of different treatment methods just as those with aquarium fish often choose to do. There are specifically designed activated carbon filters which can remove most of the chloramines in a domestic water supply and also dechloraminating chemical or water conditioners available in pet shops. Carbon filters must be of the correct type that have a high quality granular activated carbon and allow a longer contact time which is required for chloramines removal. Even then not every trace may be removed, but levels are lowered enough to prevent problems. Use of ascorbic acid (vitamin C) is also used in the industry, and by laboratories to remove chloramines from water after they have done their disinfection job.
Chemicals are also added to drinking water to adjust its hardness or softness, pH and alkalinity. Water that is naturally acidic is corrosive to pipes and sodium hydroxide may be added to reduce this. Sodium is a contaminate we dont need in hydroponic systems, but may be present at surprisingly high levels in certain water supplies. Domestic water softeners may also contaminate the water with sodium which is not seen as a problem for drinking, but can run amuck with a well balanced hydroponic system and sodium sensitive crop.
What water problems may look like
Its extremely difficult to determine if something in the water supply is causing plant growth problems. Root rot pathogens may originate in water, but they can come from a number of sources, including fungal spores, blown in dust or brought in by insects. Mineral problems can be a little easier to trace if the water supply analysis is available to check levels of elements. Plant problems which may be caused by water treatment chemicals are difficult to diagnose as some plants are much more sensitive than others and the type of system also plays a role.
Research studies have reported that chloramines in hydroponic nutrient solutions can cause growth inhibition and root browning in susceptible plants. One study reported that the critical chloramines amount at which lettuce plant growth was significantly inhibited was 0.18 mg Cl/g root fresh weight, however, the levels at which some other species would be damaged is as yet undetermined. Similar problems exist with the use of other water treatment chemicals; chlorine and hydrogen peroxide are good disinfection agents, but too much in the hydroponic nutrient will cause root damage and just what is a safe level is dependant on a number factors such as the level of organic loading in the system.
Hard water
Hard water is water that has a high mineral content, usually calcium and magnesium, with calcium present as calcium carbonate or calcium sulfate. Hard water can occur in wells and municipal sources and has a tendency to form hard lime scale on surfaces and equipment. A hard water supply is generally not a major problem for hydroponic gardens; calcium and magnesium are useful elements for plant uptake, however, high levels in the water can upset the balance of a nutrient solution making other ions less available. Commercial growers routinely use hard water supplies and adjust their nutrient formulation to take into account the Ca and Mg naturally occurring in the water and also adjust for any alkalinity problems with water acidification. Smaller growers can use one of the many excellent hard water nutrient products on the market to get a similar effect.
Ground water wells
Many commercial hydroponics growers use well water for hydroponic systems and adjust their nutrient formulations to suit the natural mineral content of their water supply. Smaller growers would be advised to find out what is in their well water source just to check for potential problems as water which has percolated through soils tends to pick up some minerals and in some areas, high levels of unwanted elements such as sodium or trace elements. Well water can also contain pathogens and may need treatment before use, although often it is just the mineral levels that need adjustment. Water from dams, lakes and springs is usually similar to well water, but can contain much higher levels of sediment, organic matter and fungal pathogen spores.
Rain water
Rain water collection can be a good way to bypass problems with municipal or well water in some areas; however, there are still some risks. Acid rain from industrial areas, sodium in coastal sites and high pathogen spore loads in agricultural areas can still occur. Generally rain water is low in minerals, but in the process of collection from roofs and other surfaces, can collect wind blown dust and fungal spores. While this is generally not a problem for healthy plants, rain water should be treated before use with young seedlings and clones where pathogens could infect sensitive tissue and open wounds.
Solutions to water quality problems
Organic material such as coconut fiber gives a greater buffering capacity for some water problems, including residues from chemical water treatments, than solution culture systems. Drain to waste media systems are also useful where the water supply contains unwanted elements such as sodium as these arent as susceptible to the accumulation that can occur where the solution is recirculated over a long period of time. Where problems with unwanted minerals and very hard water exist, frequent changing and replacement of the nutrient in the system can also be useful to keep things in balance. Water with a high alkalinity will need considerably more acid to keep the pH down to acceptable levels than water with low alkalinity; however, by acidifying the water first before making up a nutrient solution or adding to the reservoir, much less acid will need to be added to the system to adjust pH over time.
There are a range of other treatment options that indoor gardeners can use to improve the quality of their water supply. If pathogen contamination is an issue, slow sand filtration is one of the most effective methods, although perhaps not that practical for those with limited space. Chemical disinfection methods for pathogen control include hydrogen peroxide, chlorine and other compounds, although care should be taken that most of the active chemical has dissipated before the water is used to make up the nutrient solution. Heat, distillation, reverse osmosis and UV treatment can all be used for pathogen control, with many small RO and UV treatment systems now on the market. UV filters for aquariums can be used for small hydroponic growers to treat water with good success, provided sufficient contact time is allowed. If excess minerals or unwanted elements such as sodium are present in a water supply, reverse osmosis (RO) or distillation can be used to remove these. Organic matter in ground water sources can be removed with settling and filtration and treatment with H2O2, while chemical contamination problems and removal of water treatment compounds are more easily treated with the correct type of activated carbon filter with a sufficient contact time.
Super-charged water for hydroponics
While it seems logical that pure, clean and demineralized water is the best place to start when making up a hydroponic nutrition solution, the possibility of creating a water source that has certain benefits for plants is a relatively new concept. Water is not just a carrier for essential nutrient ions, the nutrient solution becomes a whole biological system in its own right with organic matter, root exudates, various species of microbes including fungi, bacteria and their by-products (both good and bad), beneficial and unwanted mineral elements and a range of additives growers may be using. Some studies have found that inexplicable growth increases could be obtained using certain ground water sources compared to rain or RO (essentially pure) water to make up a hydroponic nutrient solution indicating there may be natural factors in such waters which have benefits. Not all ground water sources have this effect; in fact, some can have negative influences on plant growth. Furthermore, another essential plant nutrient oxygen in dissolved form - is usually present in water supplies; however, some water treatment processes can drive much of the dissolved oxygen (DO) out of a water source. In theory it would be possible to not only remove those things in the water we dont want pathogen spores, unwanted minerals, chemical residues from water treatment - but to also boost the water with useful properties such as a high DO content, a population of useful and disease suppressant microbes and some natural and potentially beneficial minerals and compounds. One way of achieving this would be with the use of slow sand filters or mineral filters for water supplies which are inoculated with beneficial microbes and with oxygenation of the water for a few days before making up nutrient solutions or topping up reservoirs. Further down the track we may see quicker and easier methods of supercharging water for hydroponic systems, taking water quality to a whole new level of science.
Chlorine Gas:
This highly reactive halogen gas is volatile enough that can be easily detected by its odor, especially in the shower or when aerating faucets are used. This is one of chlorines short-comings as a disinfectant: It off-gases (volatilizes) from exposed water. Hobbyists have made good use of this effect for many years. Chlorinated tap water, especially drawn through an aerating faucet, will off-gas and effectively lose all its chlorine to the atmosphere within days. Some growers may not fully understand the off-gassing process and may not use the most effective setup for off-gassing. The best process is an open-top container with a power head or pump to circulate the water, or even just an air stone. This obviously calls for a relatively large container, but it also means that fewer containers are needed, as the circulation greatly enlarges the effective surface area for off-gassing. Exposed surface area is critical. The best situation without circulation in theory could be shallow trays with large surface exposed to room air, but that is impractical in application it would be very messy and require large amounts of space. Buckets are acceptable, but not overfilled, please. If bottles must be used, do not fill past the shoulder (where the bottle starts narrowing) this will allow the largest possible surface exposure. I used 45gal tanks or food-safe plastic tubs (trash can scale), both with pumps and heaters, open-topped. I have never detected residual chlorine after 24 hours operation in these, but allowed 48 hours for safety and to remove the requirement for routine testing. Static containers may or may not be safe to use after just 24 hours. Most, with good surface area exposed, will be after 48 hours, but this is best confirmed by test. If after you have found the required time for off-gassing, then you can add a bit more to ensure removal and no longer routinely test so long as the utility does not change the concentration. We no longer have hobby liquid tests for chlorine or chloramine, but must rely on swimming pool tests.
If you do not have the space and time to off-gas chlorinated water, there are many products available which will neutralize the dissolved chlorine. The active ingredient historically was sodium thiosulfate, and it is still highly effective for this use. This material captures any free dissolved chlorine gas and coverts the elemental chlorine (Cl2 dissolved gas) to the chloride ion (Cl-) which is harmless at those concentrations. The reaction is rapid. Just add the recommended amount, stir very briefly and add to the reservoir.
With dissolved chlorine gas disinfectant, there is only one job to be done, and it can be accomplished in two ways: Remove the chlorine gas (off-gassing), or inactivate it (chemical conversion to the chloride ion by thiosulfate). These are simple and straightforward.
Chloramines:
The growing situation with chloramines is more complex and demanding. We cannot efficiently off-gas chloramines, so the simplest solution with chlorine does not apply at all. We equally cannot use just thiosulfate it does not do enough. There are 3 separate and distinct jobs, all of which must be done to ensure the safety of chloraminated water for use in our reservoir:
1. Break the chloramine-ammonia bond. Thiosulfate alone can do this at about the same dosage used for chlorine-only disinfectant.
2. Convert the freed dissolved gas chlorine (Cl2) to chloride ion (Cl-). Thiosulfate again can do this as well; at about the same dosage as before, so double the chlorine-only dose can do both of these two jobs well.
3. Lock the freed ammonia dissolved gas (NH3) into the ammonium ion (NH4+) form (which is usable by the nitrification bacteria). The former is toxic; the concentration may only be high enough to damage the plants, or can be high enough to kill them. Thiosulfate alone is useless for this job, regardless of the dosage. Thiosulfate has no effect whatsoever on dissolved ammonia gas. Bummer! We must use newer and specialized agents which specify on the bottle that they do each and all of the three jobs required.
There are a number of commercial products which specify in print that they destroy (or other terms to that effect) chloramines. That is valid even if the only active agent is thiosulfate it does break the chlorine-ammonia bond which defines chloramine, so technically the chloramine is no longer there. Does that mean the water so treated is safe to use? No, it definitely does not. The freed chlorine gas must be converted to chloride ion, but as with the bond breaking, thiosulfate can do that as well, and is cheap and safe - so double the chlorine-only dose and cover the freed chlorine as well. Is the water now safe to use in the reservoir tank? No, unfortunately not. It still has all the ammonia released floating around at hazardous levels. If the product does not specify that it locks the ammonia into the harmless ammonium ion form, or at least notes that it neutralizes both the chlorine and the ammonia released, we have to assume it does not do this commercial products never claim less that they do. Destroying chloramine is required, but is not sufficient. This is a key point, do not be misled. Both of the freed dissolved gases must be neutralized to make the water safe. This is where the marketing wizards take advantage of the chemically and biologically naïve. You do have to both read and understand the fine print, or you could kill your fish. Strictly as an FYI, yes, I have killed fish that way. I will not do that again. Specialized agents are available which do the whole job break the chloramine bond and convert both freed toxic gases to harmless ions. Unfortunately, this is another situation where you cannot trust your local fish store, nor the chains, or mail-order houses. They quite likely do not understand the chemistry themselves. You need to ask on-line for suggestions of brands which do all the necessary jobs reliably, or search the manufacturers site for detailed information if they do not clearly state that all three tasks are done, that product is not suitable.
There is another complication with post-chloraminated water. It still reads positive for ammonia on most hobby test kits. Read the information on your test kit for ammonia. If it specifies that it reads total ammonia nitrogen (or TAN), you will see positives with your test after using a good anti-chloramines agent. These are not false positives. They are real and valid, but do not necessarily indicate a hazard to your fish which the kit instructions historically have listed as hazardous. Remember that ammonium ion (NH4+) is harmless, only ammonia dissolved gas (NH3) is dangerous, just as was the case for chlorine gas versus the ion form. The effective anti-chloramine agents lock all free ammonia gas into the ammonium ion form which is harmless. The problem is that our 20th century tests are no longer adequate in this century. There are tests available which read only free ammonia (NH3), but to me they are not yet user-friendly. Technology changes rapidly these days, hopefully more user-friendly but adequate test kits will available soon. Until then, we must use the proper dose of an effective agent and rely on it working, or prescreen with difficult-to-use tests.
For what it is worth, I use Seachems Prime for chloramines, and Genesis for chlorine-only.
References:
1.
http://en.wikipedia.org/wiki/Chlorination
2.
http://en.wikipedia.org/wiki/Chloramine
3.
http://www.epa.gov/ogwdw000/disinfectio
index.html
4.
http://www.lenntech.com/processes/disin
lorine.htm
5.
http://www.lenntech.com/processes/disin
amines.htm
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