The effect of Chlorine on DOCs

[HTH]

I expect the following will make some people uncomfortable so I added this preface.

To save posts about this not working with chlorimines I am ask people not to try this if you have chlorimines instead of chlorine in your water. In fact I am not suggesting anyone try this as I will not be responsible for the trouble you get into. Sill it is interesting to talk about. There is also an issue with "chlorinated disinfection byproducts", so it is a tradeoff between them and the DOCs. I expect naysay from the people who are unwilling to step outside their comfort zone. No problem with that please note I am not asking you to experiment on your pond.

Adding chlorinated water to a pond should oxidize the DOCs. Obviously the new water in a small water changes would have a small effect. But say one did a 25% or 50% water change, you immediately get a DOC reduction from the change. From what I have been reading the chlorine in the new trickled in water would further reduce DOCs. If you trickle water the best time to add water conditioner may be after you have filled the pond.

It would be very interesting to compare the DOCs prior to and after a water change with chlorine to see if they have been reduced by a fraction greater then expected from the change. I did a quick look on ebay and amazon without luck for a DOC test kit.

OK so if this works it makes sense that one could process the water directly with chlorine bleach without doing a change. I am not suggesting adding it directly to the pond. Maybe a small processing setup where bleach is added and excess removed in a second stage of the process. I would not try this unless I had a good monitoring and control system in place. A batch setup would be easy.

 

[Mucky_Waters]

Howard I'm having trouble understanding what you are suggesting, on one hand you suggest "Adding chlorinated water to a pond should oxidize the DOCs.", then you say "I am not suggesting adding it directly to the pond."
Best I can figure is you are suggesting adding chlorine to the water before adding it to the pond, then removing the chlorine and then adding the water to the pond as part of a typical water change. Am I correct?
If so I see no need to try and reduce the DOCs in fresh water being added to the pond, since it's the DOCs that develop in the pond that you are trying to get rid of, and the best way to do that is through frequent water changes, or a Foam Fractionator. Though, I believe I can attest that the former is far more effective than the later.

Here's my thoughts on the mater, and what I do, and I have stated them before in this forum. Our water is chlorinated, I trickle (drip) water into my pond constantly 24/7. Because, as you say the chlorine oxidizes with the DOCs, the minute quantities of chlorine added to the pond are quickly neutralized and can never (ever) accumulate to levels that would be detectable by normal fish keeper chlorine test kits, and of course could never harm the fish. To me it makes sense to accomplish water changes in this way.
I imagine that the tiny amounts of chlorine do help to "oxidize" DOCs in a minute way, but by far the greatest reduction in DOCs occurs, not from the chlorine, but from the constant water change that is continually going on as new water is slowly being added and replacing water that is constantly being flushed out the overflow.
I have found this method of flow through trickle water change to be the most effective way to solve a multitude of pond water quality problems and routine maintenance chores. It helps reduce everything from DOCs, to nitrate, to all kinds of algae (green water and string algae), it also helps maintain a constant PH in the pond water, replaces water loss from evaporation and wicking, and maintains a constant water level in the pond without the use of extra mechanical devices like automated water timers or floats. It also totally eliminates the need for doing routine weekly water changes, which can be a big chore, especially if your source water is chlorinated. No need for storing and dechlorinating the water before adding it.
The only down side I see is if your water is metered and it will cost you a little extra money to do this. Of course the bigger your pond the bigger an issue this will be.

 

[HTH]

Drip is fine for people who can afford the water. With large ponds or it is not an option unless you are lucky enough to have a spring.

I am talk about 2 concepts.

1st the effect of trickling chlorinated tap water into a pond during a major water change.

Adding chlorinated water to a pond should oxidize the DOCs. Obviously the new water in a small water changes would have a small effect. But say one did a 25% or 50% water change, you immediately get a DOC reduction from the change. From what I have been reading the chlorine in the new trickled in water would further reduce DOCs. If you trickle water the best time to add water conditioner may be after you have filled the pond.

2nd the possibility of adding a chlorine injection system to a filter.

OK so if this (the above) works it makes sense that one could process the (existing pond) water directly with chlorine bleach without doing a change. I am not suggesting adding it directly to the pond. Maybe a small processing setup where bleach is added and excess (if any) removed in a second stage of the process. I would not try this unless I had a good monitoring and control system in place. A batch setup would be easy.

 

[Mucky_Waters]

Ok I think I understand now, you are talking about removing a certain amount of water from the pond, chlorinating it, then adding it back again. Possibly having a rotating batch system, which would require two auxiliary tanks, one to hold the previously treated water, and another one drain the pond water to so you can fill the pond with the treated water, then after refilling the pond, treat the newly drained water for the next water change and repeat the process.
That leads me to ask what actually happens to the DOCs when it is "oxidized" by the chlorine. What is the chemistry, where does the carbon go, or rather, what does it get converted into when it oxidizes?
And what about nitrates, after ammonia is converted to nitrite, and nitrite is converted to nitrate, nittrate buildup can still be a problem in some ponds that don't have enough plants to absorb it. Does chlorine treatment do anything to nitrates in the water?

 

[HTH]

Again I need to try to say that I am talking about two ways of applying the same process. You have a handle on one aspect of the 2nd one.

That leads me to ask what actually happens to the DOCs when it is "oxidized" by the chlorine. What is the chemistry, where does the carbon go, or rather, what does it get converted into when it oxidizes?

When DOC are oxidized they create "chlorinated disinfection byproducts". As far as I know chlorination is the last step in water treatment for most water supplies. Whatever the chlorine leaves behind you drink. They already exist in the water we use to fill the pond even if we dechlorinate the water. But I am not saying the CDB's in the tap water will be the same as created by chlorine oxidizing DOCs in the pond. But it is already happening when one trickle fills a pond, the only difference is scale.

And what about nitrates, after ammonia is converted to nitrite, and nitrite is converted to nitrate, nittrate buildup can still be a problem in some ponds that don't have enough plants to absorb it. Does chlorine treatment do anything to nitrates in the water?

[SIZE=12.727272033691406px]Apparently[/SIZE] nitrates are not effected by chlorine because nitrates exist in chlorinated water supplies.

 

[Mucky_Waters]

So, in essence you are trading DOCs Dissolved Organic Compound for DBPs Chlorination Disinfection Byproducts.
Questions is, which is more desirable to have in your pond?
I guess if you are mainly interested in is water clarity, there would be no question, go with the DBPs, but for fish heath the DOCs would be safer I would think.
Let us know how it goes.

 

[HTH]

Randy the people here including me who do large water changes and trickle tap water to refill are already doing it! Along with every person who forgot to turn off the tap and overflowed their pond.

Somebody who can measure DOCs needs to take some readings. I was hoping to generate some interest and find someone equipped to do so.

If some pond supply was selling this for $25 a pint people would be all over it.

 

[Mucky_Waters]

The difference I see, and correct me if I'm wrong, is that with a "normal" water change, or if you are overflowing your pond, you are totally removing some of the old water along with some of the DOCs and the DBPs from the system. It's true you will be creating new DBPs as you add the new chlorinated water, but as you already mentioned it is minimal, but because you are actually removing some of the old water (as well as DOCs and DBPs) from the system your total PPM count won't continue to build. But if you simply treat the water with chlorine, creating new DBPs, and then add the same water back to the pond your total DBPs will continue to climb each time you do a water treatment. Same problem they have with swimming pools where water changes are uncommon.
I guess what I don't understand is how will you be removing the DBPs from your system so they don't build up to toxic levels.

 

[HTH]

The difference I see, and correct me if I'm wrong, is that with a "normal" water change, or if you are overflowing your pond, you are totally removing some of the old water along with some of the DOCs and the DBPs from the system. It's true you will be creating new DBPs as you add the new chlorinated water, but as you already mentioned it is minimal, but because you are actually removing some of the old water (as well as DOCs and DBPs) from the system your total PPM count won't continue to build.

There may be some buildup but it should be much slower then treating the pond without any water change. It is not totally unlike the calculus problem where you have a hose filling a leaky tank. When does it go dry or empty sort of thing.

.But if you simply treat the water with chlorine, creating new DBPs, and then add the same water back to the pond your total DBPs will continue to climb each time you do a water treatment. Same problem they have with swimming pools where water changes are uncommon.
I guess what I don't understand is how will you be removing the DBPs from your system so they don't build up to toxic levels.

Agreed that they will continue to rise.. With each unit of chlorine used the levels would rise. The question is what levels are unacceptable and how long does it take to reach them? . There are other questions like do plants take up DBP's. Do any of the them break down over time? I have no way of figuring this. But when levels are getting close you do a water change... no big surprise there.

 

[HTH]

Someone on the forum (can't find the post to credit the person) mentioned using potassium permanganate to neutralize DOCs in much the same way as I proposed using chlorine bleach in this thread. Found a link on the use of PP in fish ponds..

 

[crsublette]

Interesting idea.

Yep, chlorine essentially reacts with organics kind of like an oxidizer. I don't know what the impact of the accumulating chlorine by-products have on the pond. The problem with the "wait and see" method is ya won't know anything until the problems already happen. I would think an activate carbon product might remove the by-products, just my guessing though.

Potassium permanganate (PP) leaves a residual of manganate, which is a dense form of manganese, and is beneficial to the biological activity in the pond, but PP is extremely easy to overdose, very easy to kill everything in the pond, if the measurement is off just a few grams.

There's really no test for DOCs since DOCs can be many things and can refer to all sorts of dissolved organic particulates. It is like KH represents all resistance to buffering, since KH test is just an acid titration test within a particular range, but we assume it is a test for bicarbonate since that is the buffer system that is most common and the one most folk typically use in managing their pH. With DOCs, the closest test you would get to would be with a TDS meter, but a TDS test will test for dissolved organic particulates and also include many trace minerals, presence of bicarbonates and precipitated compounds such as calcium carbonate, other minerals, and can test for chloride ions as a measure of salinity.

Interesting theory though with the chlorine, as long as it gets neutralized prior to the water being re-introduced to the pond. Sounds like it would work in theory as long as the by-products are not a concern. I would imagine the by-products are not that big of a concern since, when dechlorinator is put into the pond, the chlorine is not instantly neutralized so there will always be some of these by-products in the pond since there will always be some chlorine reacting to the dissolved organic particulates in the water..