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  • From: Chris Reid <chriscreid AT yahoo.com>
  • To: market-farming AT lists.ibiblio.org
  • Subject: [Market-farming] 1. Re: Purifying Rural Water for Watering Garden Plants
  • Date: Mon, 4 Jan 2010 11:45:39 -0800 (PST)

Regarding the question on clearing chlorine and arsenic, there are two types of "chlorine" used in municipal water systems: chlorine which is more fugitive and can be bubbled out of the water using an aquarium filter (or just let the water sit to do so) and chloramine, which is harder to get rid of.  I do know that ascorbic acid can be use to get chloramine out of water, but I know this from research cited in a compost tea e-group I used to belong to (Yes, for brewing compost tea, removal of chlorine and chloromine is recommended).  I am sorry I cannot help with amounts, but they will vary according to how heavily treated the water is.
 
Any fixtures that handle untreated water only must be kept scrupulously clean as there is more of an opportunity for them to  become reservoirs for organisms such as the one that causes legionnaire's disease .
 
But water in a bucket or trash can, with or without an air filter, will off gas and some ascorbic acid stirred in could help.  The chlorine is to minimize development of bacteria, but has nothing to do with other contaminants such as heavy metals or pesticides.
 
Thus, the arsenic is a different matter.  It varies how much is natural.  It is not present in great degree in all soils, but can be locally present for geological reasons.  I read up on it some this year and found that arsenic can be absorbed into plants at fairly low levels, and it displaces phosphorus so might look the same as a phosphorus deficiency symptomatically.
 
Arsenic compounds can also enter water from farm or industrial sources.  For example, arsenic compounds in Roxarsone, an antiparasitic feed additive that has been used in conventional chicken production, are nearly completely passed out of the chicken who are fed it into their manure.  Runoff from such manure (or heavy use of it as fertilizer on ground near a well that is partly groundwater fed) is worth exploring as a potential source of arsenic contamination.  ATTRA did a piece on this topic awhile back that is available on their website.
 
For people on municipal water (or perhaps near a reservoir and thus subject to some of the conditions affecting it), Environmental Working Group has assembled an extensive database on municipal water.  By typing in http://www.ewg.org/tap-water/welcome you will come to their database, which allows you to enter your zip code and look up the contaminants that have tested  in that town's water.The database shows whether they are under or over health limits (and legal limits, which are often higher than limits at which chronic health problems have been shown to occur).  The NY Times has been running an informative series on municipal water in recent weeks, also linked elsewhere on the ewg site.  It has been an interesting read.  Short story: there are far more chemicals than there is information on their health impact, and the original legal  levels for some contaminants we now know should be lowered, but this has nto been done.  And tests above legal levels have not resulted in muncipalities taking action to correct defects in an increasing number of cases.
 
On the subject of filtration options, the ewg site also has information on the different types of filters and what they can filter.  Activated charcoal filters some things; reverse osmosis or distillation removes other issues -- rather than guessing, if this is highly important to your health or your business, testing the water will reveal  the pattern of minerals and contaminants in the water being treated.  This is a better way to select a filter than what one is afraid of (but may not be there anyhow).   Some contaminants may be be present only intermittently in testing, so it may be helpful to ask the lab about timing of testing, depending on one's goals.
 
Our community is dealing with a long-unaddressed industrial landfill with a lengthy list of identified contaminants, and a cluster of cancers and contaminated wells not far from the site that may have been separately contaminated with chlordane and dieldrin.  As we are learning in our community, groundwater is no longer something we can assume is clean.  A recent research effort at McMasters University in Canada resulted in a test for chlordane that would be far cheaper and more easily usable in the field. Making contaminant testing affordableand widely available will ultimately be very helpful, as testing currently can run into hundreds of dollars or more, depending upon what one wants to test for.
 
As examples of what can be taken up by plants:  antibiotics (again, raw uncomposted  manure or runoff can be sources, but there are a very few persistent antibiotics), pathogenic bacteria (it has now been found not just ON the surface, but photographs now show bacteria within the cell structure of e.g. green onions or lettuce), heavy metals, herbicides and pesticides. 
 
Life is dirty, to be sure.
HTH
 
Chris Reid
Stamford, CT




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