[FONT="]Recirculating solution culture systems such as NFT & DWC have less buffering capacity to water treatment chemical residues than organic media-based systems.
The key to getting rid of chlorine is to let it sit out in a pail, large surface area is important and let it off gas for 48 hrs. minimum.
To get rid of chloramines get a charcoal/activated carbon filter.
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 1990’s 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.[/FONT][FONT="]
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 don’t 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.
[/FONT]
