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[compost_tea] Re: Effects of chlorinated water
Incredibly wonderful ICTC conference this month. Thank you everyone
for a wonderful time.
It seems to me we could pay for a couple SFI tests, one that showed
microbe counts in the tea, and the other showing microbe counts in
tea pulled through a hose bib via a Siphonject which will dilute the
tea with 16 parts water. Drawing the diluted tea for testing from
the end of the drip tubing will tell how the organisms have changed
through their brief encounter with chlorinated water.
We are fortunate in Eugene Oregon to have incredibly clean water from
the McKenzie River as our source, which needs only minimal treatment
with chlorine gas.
A similar test with chloramine treated water will provide essential
information to those who have chloramine in their water.
I questioned the supervisor of our local water treatment facility
regarding the use of chlorine in our water and the effect of that
chlorine on compost tea. We posted this information for our local
Master Gardeners. It may be helpful to this discussion.
It's long, so pull up a chair and a cup of tea....
And remember this is for a water source treated with chlorine gas,
not chloramine...
The following is a series of questions asked by Anne Donahue,
Compost
Specialist for the City of Eugene to Doug Wise, Supervisor of Water
Treatment and Filtration for the Eugene Water and Electric Board in
Eugene, Oregon.
Anne:
Not many Master Gardeners realize what a hidden jewel of expertise
we
have in our midst. Can you share with us what you do for EWEB and
how
you have come to be our local "water expert"?
Doug:
I did my apprenticeship in a filter plant going to college, studied
and assisted the microbiologist in Denver, worked as a treatment
plant
operator in Aurora, Colorado after teaching high school and then
moved
to Eugene where I've been an operator, water quality lead and Water
Supply and Treatment Supervisor for EWEB for the last 23 years.
Also,
I've passed five four-hour examinations and attended different water
treatment conferences and classes over the years. I have a Masters
Degree in Public Policy, Planning and Management from the University
of Oregon.
* * * * *
Anne:
Can you tell us where our water comes from, and in general, how it
makes it way to our tap? How does the water source/system of Eugene
differ from Springfield?
Doug:
The McKenzie River is one of the clearest and cleanest sources of
surface water imaginable. There is very little commerce or industry
upstream from our community and it is one of three rivers in Oregon
which will not have any future discharge permits (sewerage outfalls)
issued by the DEQ, so it will stay clean. We take the water and
disinfect it with chlorine and then add aluminum sulfate (high
quality
pickling alum) which "catches" the negatively charged dirt particles
with the positively charged aluminum ions. We settle out the floc
that
is formed from this reaction before we filter out any remaining
particles. Our water is very soft and we add lime (just over half a
dry ounce of calcium oxide per thousand gallons) to raise the pH to
7.7 so the water won't corrode plumbing fixtures, reducing the risk
of
lead or copper leaching. We also take some chlorine OUT leaving
only
one-half part per million as it leaves the plant. The average
chlorine in the distribution system (customer taps) is 0.32 mg/l
(parts per million). Most people's noses can detect chlorine in the
water at about 0.4 mg/l...just above our delivered dosage.
* * * * *
Anne:
Why is chlorine added to the water? How much chlorine is added to
the
water? What is the difference between chlorine and chloramine, and
why do we use chlorine and not chloramine as Portland does.
Doug:
This is an easy one. Few people in this country have feared
typhoid,cholera, amoebic dysentary, bacilliary dysentary or other
water borne illness since the advent of chlorine disinfection. It
is
even effective (eventually) against Giardiasis (beaver fever).
To assure disinfection, we average about 1.6 mg/l of chlorine added
to
the raw water, or about a third of what you might expect in a
swimming
pool. After the demand is met (killing bacteria and oxidizing
organic
carbon) and the treatment process is complete, we still have between
0.8 and 1.0 mg/l of chlorine in the water. We reduce this to 0.5-
0.1
leaving the plant.
Free chlorine -- the kind EWEB uses -- is a dissolved gas, just like
the carbon dioxide in soda pop. Soda usually has a pressure of 14
psi. The water is under 80 psi on average so the chlorine will
"escape" the solution as quickly as it can when the pressure is
relieved. This happens when customers open their tap.
Interestingly, the effect of chlorine leaving solution causes two
types of common complaints. The first is that "my water smells like
chlorine, especially in the morning." The gas leaves the solution
during the night in the warm house and the first spurt of water
pushes
the gas out, often with a noticeable odor in the shower or the
sink.
The second common complaint is that "when I leave my water on the
nightstand, it tastes different." This too is because the water
can't
hold the naturally dissolved oxygen, carbon dioxide and chlorine.
When
these products off-gas, the water tastes different.
Chloramines are used when a water system is too large or lacking
steady pressure to keep a free chlorine residual and, therefore, may
be at risk of bacteria and other pathogens. The upside of
chloramines
is that they hang around a LOOONG time. The problem is that they
are
much less effective as a disinfectant, by the order of ten times or
even 100 times depending on the source water. Chloramines are also
hard to get rid of in water. Pet stores sell de-chlor which is
NEEDED
in chloraminated water. Free chlorine can be removed simply by
letting
the water set in an open container for "a half hour" or so.
* * * * *
Anne:
Does the chlorine dissipate by the very act of overhead watering?
Doug:
Most of it will. This is a good way to reduce chlorine, but without
measuring the collected water, the exact amount of chlorine
remaining
might vary.
* * * * *
Anne:
Will the chlorine damage the beneficial organisms on leaf surfaces
if
I overhead water?
Doug:
This is a tough one. Define and quantify "beneficial organisms" and
describe the chlorine dose. Soaking a leaf in Chlorox (50,000 parts
per
million) will clean most anything in a half hour. Last week each
drop of
McKenzie river water contained about 1,200 total (aerobic) bacteria.
Contact with 1.6 mg/l of chlorine for four or five hours reduced that
number to the 2 - 3 range (without filtration). So yes, high
concentration for a lengthy time might diminish advantageous
populations.
It would also impact plant pathogens.
* * * * *
Anne:
Will it damage beneficial organisms in my soil if I water my garden
through drip irrigation?
Doug:
Almost assuredly not. There are LOTS of soil bacteria, many of
which
are used as indicators of soil health, but some of which are also
indicators of contaminated water. Citrobacter, Klebsiella and
several
aeromonas species as well as E.coli bacteria are common in soils and
may be opportunistic pathogens. The chlorine concentration in the
water is used up VERY quickly by "dirt". We call this chlorine
demand. My guess is that too much water would do more damage from
limiting oxygen uptake than by the chlorine in the water. Dumping a
swimming pool or hot tub might be an exception since these commonly
have buffers to keep the disinfectant "active".
* * * * *
Anne:
If I use a hose end sprayer to spray compost tea, will I lose
organisms in the tea as I spray?
Doug:
Relative to billions, yes, relative to safe drinking water, no.
* * * * *
Anne:
If I dilute compost tea with city water will I kill the beneficial
organisms in the tea?
Doug:
Not if it's disinfected with reasonable amounts of "free chlorine".
* * * * *
Anne:
If I wanted to remove the chlorine altogether, how would I do that?
Doug:
There are several common commercial products out. Sodium bisulfite
used for wine-making works. Sodium thiosulfate, the active
ingredient
in most aquarium dechlorination products works. My common joke is
that a spoonful of dirt will create enough chlorine demand to kill
any
residual. Or a finger stuck into a glass of water. Another product
that works well is vitamin C or ascorbic acid, though it lowers the
pH
and may corrode metal products over time.
* * * * *
Anne:
How long will water have to sit in a bucket for the chlorine to
dissipate? How does that time change if I have an air stone bubbling
in the bucket?
Doug:
My rule of thumb for customers who are really concerned about
chlorine
in the water is to let a container set in a refrigerator
overnight...or keep "standing" water replenished since "old water"
will have enough demand to use up the chlorine.
Any aeration or agitation will speed the loss of chlorine gas from
solution. Probably, the airstone from an aquarium or tea-bucket will
have enough chlorine demand to do the trick all by itself.
* * * * *
Anne:
What if I add vitamin C? How much per gallon of water, or five
gallon
bucket?
Doug:
Dust on a finger will handle a gallon or more. Two pounds of
ascorbic
acid will handle 120,000 gallons of water with a chlorine residual
of
1.0 mg/l.
Anne:
What if I toss in a tablespoon of soil or compost, will the chlorine
bind to that soil/compost? (And why/how does it bind to the soil? Is
it binding to the organic material, or the soil components: sand,
silt, and clay? i.e., does the percent of organic matter in the soil
determine how chlorine is bound in the soil? Once bound, what
happens
to it?)
Doug:
Chlorine (and bromine and iodine and fluorine) all act to oxidize
natural organic matter (NOM) by forming complexes with them.
Chlorine
vigorously attacks many chemical bonds and replaces a variety of
atoms
or molecules making new compounds. In bacteria, it may attack the
cell wall or membrane, preventing nutrition and reproduction even
when
it doesn't kill the organism. Sunlight typically breaks these new
bonds when it gets a chance. Or any reducing (anaerobic) environment
will work on chlorinated compounds pretty aggressively.
* * * * *
Anne:
In essence, if using city water, are you "sacrificing" the organisms
in say, a teaspoon of tea, for every gallon of tea you use? (I'm
just
trying to get an idea of the amount of damage that is done by the
chlorine in the
water)
Doug:
Maybe the organisms in a small drop of tea.
* * * * *
Anne:
Do you have any further thoughts to share about the quality of our
local water?
Doug:
Eugene uses a multiple barrier approach to improve an outstanding
water source. We have detected no organic pesticides in the river
water over the last 95 years and we now screen for more than
five-dozen different organic chemicals regularly. That doesn't mean
there is "zero". It just means that we can't find any looking in
the
range of 50 - 500 parts per trillion. At these levels, if there was
a
chemical detected, I'd have to drink eight glasses of water a day
for
720 years to be sure of drinking a single drop of the chemical.
We have remarkable few minerals or other inorganic chemicals. The
treatment process reduces all metals by 30 - 70 percent and we are
mostly ND (not detected at measured levels) for heavy metals.
In short, we know what is in the water, and more importantly, what
isn't. And we're able to share this information with the confidence
of
decades of consistent test results.
Thanks for the questions. The answers are a little general, but may
be useful for gardeners with concerns.
Anne Donahue
Compost Specialist
City of Eugene Planning and Development Department
99 West 10th Ave
Eugene, Oregon 97401
Phone: (541) 682-5542
Fax: (541) 682-6806
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