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Post Info TOPIC: Neutralizing Chlorine With Sodium Metabisulfate


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Date: Sep 23, 2011
Neutralizing Chlorine With Sodium Metabisulfate
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I think it might be cool to have a water tank full of this stuff to rinse the roof and water plants with biggrin

 

 

 

How much bleach neutralizer do I need to use?

Thiosulfate (Bleach Stop) is not as strong as Anti-chlor (sodium metabisulfite).

You need to use one whole ounce by weight (30 grams) of Bleach-Stop (sodium thiosulfate) per gallon of warm water, or a pound and a quarter for a twenty-gallon washing machine load — so, using your washing machine for this step would be very expensive and you'd better stick to a bucket, but you can do that. Cost per gallon of bleach neutralizing bath, 25¢. Not too expensive.

In contrast, you need only one teaspoon, or 2.2 grams, of Anti-chlor (sodium metabisulfite) per 2.5 gallons of water, or less than half a teaspoon per gallon of water. That works out to 18 grams per twenty-gallon washing machine load, if you like to use it there. Cost per gallon of bleach neutralizing bath, three-quarters of 1¢. Very, very inexpensive. Cheap enough even to use in the washer, if you're lazy about carrying buckets around, or if you want to use it as a regular laundry additive to reduce unwanted bleaching from chloramine in your water supply.



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Date: Sep 24, 2011
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Chris,

Would the salt in sodium metabisulfate harm the plants if it gets into the soil?



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RCIA Founder

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Date: Sep 25, 2011
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Bruce Weber wrote:

Chris,

Would the salt in sodium metabisulfate harm the plants if it gets into the soil?


 Not sure ?

 

Re: Sodium Bisulfate Ph down

Quote:
Originally Posted by Norcalmatt
Sodium........thats a technical word for salt.
Um, no, not at all. Sodium is a technical term for... Sodium. As in the element designated Na, number 11 on the periodic table.
http://en.wikipedia.org/wiki/Sodium

Sodium is a slang term for salt - from "sodium chloride" (common table salt). Typically this is used - errantly - by people who've been told by their doctors that they need to cut back on their "sodium" intake.

Quote:
Originally Posted by Norcalmatt
Anything with sodium in the name i wouldn't use.
Yes and no. Sodium is actually listed as one of the commonly used elements in hydroponics. Granted, it's not always used and when it is it's generally in very small quantities (though after a teeny bit of research I've found published nutrient formulas with Na ppms as high as 92ppm. I don't know how well that worked, or for what plant it was tailored, but it is what it is.)

But, given that some nutrient formulas do make use of sodium-based chemcial salt fertilizers, your advice of avoiding adding any unnecessary sodium to a reservoir isn't bad. Sodium is used by plants but in very small quantities and certain other nutrients can actually dangerously increase sodium uptake. Sulphates, for example, when used in high concentrations can severely boost sodium uptake and lead to toxicity.

Oh, and the Advanced Nutrients pH adjusters you mention are really nice. It's definitely worth paying for the good stuff, like you say.


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Date: Sep 25, 2011
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Here is some more info on chlorine neutralization using chemicals.

Chemical Dechlorination

 

              Whenever it is not possible to dispose of chlorinated waters safely by non-chemical methods, chlorine may be neutralized using chemicals.  Several solid, liquid and gaseous dechlorination chemicals are commercially available and are widely used by water and wastewater utilities.  This section describes the reactions of various chemicals with free and combined chlorine, related water quality, health & safety issues, ease of use, cost and other issues related to the application of the chemicals commonly used for dechlorination.

 

Sulfur Dioxide (SO2)

            Sulfur dioxide is a colorless gas with a suffocating pungent odor.  It is widely used in water and wastewater treatment plants for dechlorinating backwash water and wastewater disinfected with chlorine.  Sulfur dioxide reacts instantaneously with free chlorine according to the following stoichiometry (1):

SO2  +             H2O +    HOCl                          ®  SO4-2  + Cl-  +  3H+

Sulfur dioxide                   Hypochlorous acid                           Sulfate         

 

In the field, nearly 1.1 parts of SO2 are required to neutralize 1 part of chlorine (2).  SO2 is an oxygen scavenger.  It can deplete dissolved oxygen in the discharge water and receiving stream.  SO2 can also reduce pH of water significantly.  Approximately 2.8 mg of alkalinity as CaCO3 is consumed per milligram of chlorine reduced.

 

Sulfur dioxide is a toxic chemical subject to reporting requirements of the Superfund Amendments and Reauthorization Act (SARA).  It has a National Fire Protection Association (NFPA) rating of 2, 0 and 0 for health, fire and reactivity, respectively.  (Hazard ratings range from 0 to 4, with 0 indicating no hazard and 4 indicating extremely hazardous).  It is an extremely irritating gas.  While it is suitable for use in facilities such as treatment plants and pumping stations, it is not best suited for field applications.

 

Sodium Thiosulfate (Na2S2O3)

Sodium thiosulfate is a colorless, transparent monoclinic crystal widely used by municipalities for dechlorination.  It undergoes multiple reactions with free and combined chlorine, depending on solution pH (1,3).  Reaction with chlorine yields the following:

Na2S2O3 +       4HOCl +   H2O            ® 2NaHSO4  +           4HCl

Sodium thiosulfate         Hypochlorous acid                             Sodium bisulfate                 Hydrochloric acid

Na2S2O3    +   HOCl               ® Na2SO4      + S   +              HCl

Sodium thiosulfate         Hypochlorous acid                     Sodium sulfate            Hydrochloric acid

2Na2S2O3     +             HOCl               ®  Na2S4O6    +  NaCl             +    NaOH

Sodium thiosulfate       Hypochlorous acid                 Sodium tetrathionate  Sodium chloride   Sodium hydroxide

 The amount of thiosulfate required for dechlorination may vary with solution pH (3).   Sodium thiosulfate is a reducing agent.  However, it scavenges less oxygen than sodium sulfite, bisulfite or metabisulfite.

 

Sodium thiosulfate is a skin, eye, nose and throat irritant.  It has a NFPA Rating of 1,0, 0 for health, fire and reactivity, respectively. An EPA toxicity study indicated that sodium thiosulfate is not very toxic to aquatic species.  Sodium thiosulfate may react slowly with chlorine under some conditions, and requires more time for dechlorination than most dechlorination chemicals (4).  Over-dechlorination with sodium thiosulfate may encourage thiobacillus and some other bacterial growth in receiving streams, particularly during low flow conditions.

 

Sodium Sulfite (Na2SO3)

Sodium sulfite is another dechlorinating agent widely used by utilities.  It is available in powder/crystalline and tablet form.  It undergoes the following reaction with free chlorine (3):

Na2SO3  +    HOCl      ®Na2SO4  +  HCl

Sodium sulfite     Hypochlorous acid         Sodium sulfate                 Hydrochloric acid

 

On a weight-to-weight basis, approximately 1.775 parts of sodium sulfite are required to remove one part of chlorine (5).  Sodium sulfite is a reducing agent and is reported to scavenge more oxygen than sodium thiosulfate. 

 

The major advantage of using sodium sulfite is that, it is available in tablet form.  Many utilities find the tablets easier to store, handle and apply as compared to solutions or powders.   In addition, dechlorination tablets are very effective for dechlorinating constant, low flow rate chlorinated releases.

 

Sodium Bisulfite (NaHSO3)

Sodium bisulfite is available as a white powder, granule or clear liquid solution.  It is highly soluble in water.  Currently, many industries and wastewater utilities use sodium bisulfite solution for dechlorination.  It undergoes the following reactions with free chlorine:

NaHSO3     +      HOCl             ®  NaHSO4   +   HCl

Sodium Bisulfite          Hypochlorous acid                 Sodium bisulfate       Hydrochloric acid

 

On a weight-to-weight basis, approximately 1.45 parts of sodium bisulfite are required to dechlorinate 1 part of chlorine.  Sodium bisulfite is a good oxygen scavenger.  Sodium bisulfite can cause skin, eye and respiratory tract irritation.  It is harmful if swallowed or inhaled.  Sodium bisulfite may crystallize at room temperatures.  It is highly viscous and sometimes difficult to handle.  Sodium bisulfite is highly corrosive and caution must be exercised in safely handling this chemical.  It has a NFPA rating of 1,0,1.

 

Sodium Metabisulfite (Na2S2O5)

Sodium metabisulfite is available as crystal, powder or solution.  It reacts with chlorine as follows. 

Na2S2O5    +                2HOCl + H2O              ®2NaHSO4   +   2HCl

Sodium metabisulfite    Hypochlorous acid          Sodium bisulfate     Hydrochloric acid

 

Scavenging properties of sodium metabisulfite are comparable to that of sodium bisulfite.  On a weight-to-weight basis, approximately 1.34 parts of sodium metabisulfite are required to remove 1 part of free chlorine.  Sodium metabisulfite is an eye, throat, skin and lung irritant.  The hazard ratings for sodium metabisulfite are 3,0,1.

 

Calcium Thiosulfate (CaS2O3)

Calcium thiosulfate is a clear crystalline substance, with little color, a faintly sulfurous odor and near neutral pH.  It reacts with free as well as combined chlorine.  Calcium thiosulfate undergoes the following reactions with free chlorine (6). 

CaS2O3     +      4HOCl        + H2O  ®    CaSO4 +     4HCl     +       H2SO4   

Calcium thiosulfate     Hypochlorous acid                       Calcium sulfate    Hydrochloric acid       Sulfuric acid    

Approximately 0.99 and 0.45 mg of calcium thiosulfate is required to neutralize one mg of residual chlorine at pH 7.35 and 11, respectively.  Calcium thiosulfate is not toxic to aquatic species.  The 96-hour LC50 for fathead minnows is greater than 750 mg/L.  The NFPA hazard rating of calcium thiosulfate is 0,0,0.

 

One concern with using calcium thiosulfate is that dechlorination reactions using stoichiometric concentrations require nearly five minutes for complete neutralization (6).  Over-dosing of calcium thiosulfate may produce milky-colored suspended solids, causing turbidity violations.  Also, excess thiosulfate release may promote thiobacillus bacterial growth. 

 

Ascorbic Acid (Vitamin C)

Ascorbic acid has recently been used by several water utilities for dechlorination.  The reactions with chlorine are shown below:

C5H5O5CH2OH  +  HOCl      ® C5H3O5CH2OH + HCl  +  H2O

Ascorbic acid                Hypochlorous acid      Dehydroascorbic acid        Hydrochloric acid

 

Approximately 2.5 parts of ascorbic acid are required to neutralize 1 part of chlorine.  Ascorbic acid is not reported to scavenge DO.  Since ascorbic acid is weakly acidic, the pH of water may decrease slightly in low alkaline waters.  Caution must be exercised to prevent accidental inhalation or contact with the skin, eyes or lungs. 

 

Sodium Ascorbate

In addition to ascorbic acid, sodium ascorbate is also currently under evaluation by several utilities for dechlorination.  Sodium ascorbate undergoes the following reaction with free chlorine. 

 

C5H5O5CH2ONa  +  HOCl      ®  C5H3O5CH2OH   +   NaCl    +    H2O

Sodium ascorbate                Hypochlorous acid         Dehydroascorbic acid        Sodium chloride

 

Approximately 2.80 parts of sodium ascorbate are required to neutralize one part of chlorine.  Sodium ascorbate is not reported to impact the DO or pH of the receiving streams.  The pH of sodium ascorbate is approximately 7.0.  The chemical is very stable with a shelf life of at least one year in a dry state, if kept in a cool, dark place.  However, once in solution, the chemical degrades within a day or two. 

 

Dechlorination Chemical Summary

Currently, sodium bisulfite, sodium sulfite and sodium thiosulfate are most frequently used by water utilities for dechlorination.  The choice of a particular dechlorination chemical is dictated by site-specific issues such as the nature of water release, strength of chlorine, volume of water release, and distance from receiving waters.  Sodium bisulfite is used by some utilities due to its lower cost and higher rate of dechlorination.  Sodium sulfite tablets are chosen by utilities due to ease of storage and handling, and its ease of use for dechlorinating constant, low flow rate releases.  Sodium thiosulfate is used for dechlorination since it is less hazardous and consumes less oxygen than sodium bisulfite and sodium sulfite.  Ascorbic acid and sodium ascorbate are used because they do not impact DO concentrations. 

 

Knowledge on dechlorination efficiencies of various chemicals is incomplete.  A comprehensive study evaluating all the chemicals for various chlorinated water release scenarios is not currently available. 

 

Field Methods for Residual Chlorine Measurement

            Several methods such as water quality test strips, swimming pool test kits and orthotolidine indicator kits can be used to measure TRC in the field.  Many of these methods lack sensitivity required for ensuring regulatory compliance. 

 

A colorimetric kit supplied by Hach company is widely used to monitor dechlorination in the field.  The kit can measure free or combined chlorine residuals at concentrations of 0 to 4.5 mg/L with a detection limit of 0.1 mg/L.  In this method, a pre-measured amount of reagent is added to the water sample, mixed well, and the sample analyzed for chlorine concentration.  A liquid crystal detector indicates the chlorine concentration in solution based on the intensity of the color formed. 

 



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Date: Sep 25, 2011
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Here is some more info, the stuff looks cheap to buy.

 

I'm afraid that I must disagree. You are correct that vinegar will not safely neutralize hypochlorite (the active ingredient in chlorine bleach), and that thiosulfate will, but metabisulfite and peroxide are in completely different categories from vinegar.

The problem with vinegar is that acids react with hypochlorite to form even more caustic and deadly chlorine gas. One should never mix acid with hypochlorite, and vinegar is an acid.

However, thiosulfate is not the only chemical that will safely and completely neutralize hypochlorite bleach. Both sodium metabisulfite (ProChem's Anti-Chlor) and hydrogen peroxide (3% solution) are just as effective and safe as thiosulfate. ProChem does not even sell sodium thiosulfate.

Thiosulfate is an excellent bleach-stopping chemical, but it is slightly less practical for use than Anti-Chlor, because a much larger quantity needs to be used, making it less convenient and more expensive. While one gallon (4 liters) of neutralizing solution requires one ounce (30 grams) of sodium thiosulfate, the same amount of neutralizing solution made with metabisulfite requires less than half a teaspoon, or just 0.9 grams of Anti-Chlor. Dharma's Bleach-Stop costs a very reasonable 25¢ per gallon of neutralizing solution, but ProChem's Anti-Chlor costs less than 1¢ for an equivalent amount.

Hydrogen peroxide works excellently as a bleach neutralizing chemical. Hypochlorite reacts with hydrogen peroxide to form chlorine ion (the same as found in salt water), water, and oxygen gas. Its chief drawback is its cost. A half-liter bottle of 3% hydrogen peroxide solution bottle costs 79¢ at my local drugstore. I once used half a bottle to neutralize a child's shirt, so the cost was about 40¢ for one use; I probably could have used less, but this is not something I want to experiment with. The shirt had been soaked extensively in bleach solution, because its navy blue commercial dye was partially resistant to the bleach action; in contrast, a black tee discharged in the same session was bleached to off-white within seconds. After being neutralized with peroxide, the shirt was worn and washed probably more than a hundred times before it wore out. When the fabric wore out, holes appeared only in parts of the shirt that had never been exposed to the bleach. Thus, experience shows that peroxide is highly effective as a bleach neutralizer on cotton.

Individuals who have asthma and are sensitive to the effects of sulfite-containing preservatives (a chemical essentially identical to Anti-Chlor, problematical for some asthmatics when used in dried fruit or wine) may find that hydrogen peroxide is safer to use than the sulfur-containing bleach neutralizers such as Bleach-Stop or Anti-Chlor. I recommend that people who are sensitive to sulfites always use peroxide as a substitute when neutralizing bleach.

For more information on this topic, see "How can I neutralize the damaging effects of chlorine bleach?".



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Date: Sep 25, 2011
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Would it help to pre-treat work clothes in the washer with hydrogen peroxide, and then wash them each time with some peroxide to stop the damage caused by the sodium hypochlorite that will inadvertently get on the work clothes ? Is anyone doing this ?

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Date: Sep 26, 2011
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I am the proud owner of a 50 lb bag of it I just bought from Florida Chemical Supply here in Tampa!

The stuff is pretty cheap, and goes a long way



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Date: Sep 26, 2011
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Just use a lot of H2O and you'll be fine Chris.. You think wayyyyyyyyy too much, I think a lot about new ideas but you my friend are off the chain...

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RCIA Founder

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Date: Sep 27, 2011
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JHWorth wrote:

Just use a lot of H2O and you'll be fine Chris.. You think wayyyyyyyyy too much, I think a lot about new ideas but you my friend are off the chain...


 Always trying to get better, even after all these years.

Hey, got another idea ! Either take sawdust or Kitty Litter and put down where the chemical drips on the grass to absorb it.

We just water like hell, then water some more, just thinking all the time about other ways.



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