KH Guardian(KHG) Alk calculation

[JonasRoman]

It depends on how you *show the numbers* :)

For example, in our case with KHG, they mentioned 20ml sample volume. Let's assume we want to perform near continuous analysis and sample every 15 minutes on a 100G system. Using your numbers above (0.0002 dKH drop for every 10ml of fully neutralized sample), this will result in a whooping 0.27 dKH drop in 7 days if dumped back into the system. Not insignificant...

In one of my previous designs I was allowing a possibility of dumping waste back into the system, but the sample volume was 1.0 ml and I wanted to do hourly sampling.

On a side note, one would probably don't want to dump a sample spoiled by pH indicator back into the system in case if its colorimetric machine. It definitely smells toxic to me :)

Thanks,
Kirill

Very good Point:-) In a photometric method it is even more "bad". I will not have bromocresoolgreen in my tank;-)

 

[jerlo reef tank]

See my example above with smaller tank:)

Thank you for your feedback @JonasRoman
Does the KHG automatically re-adjust the sodium hydrogen carbonate according to the results it finds and the other parameters necessary for this calculation?

 

[jerlo reef tank]

Very good Point:) In a photometric method it is even more "bad". I will not have bromocresoolgreen in my tank;-)

Maybe the sps go that colorful with bromocresoolgreen.... or not lol :)

 

[JonasRoman]

Maybe the sps go that colorful with bromocresoolgreen.... or not lol :)

:-)

 

[JonasRoman]

Thank you for your feedback @JonasRoman
Does the KHG automatically re-adjust the sodium hydrogen carbonate according to the results it finds and the other parameters necessary for this calculation?

I am not the right person to comment their product in detail and how their algoritms works:-)

 

[Randy Holmes-Farley Verified Community Expert]

It depends on how you *show the numbers* :)

For example, in our case with KHG, they mentioned 20ml sample volume. Let's assume we want to perform near continuous analysis and sample every 15 minutes on a 100G system. Using your numbers above (0.0002 dKH drop for every 10ml of fully neutralized sample), this will result in a whooping 0.27 dKH drop in 7 days if dumped back into the system. Not insignificant...

Ah, but let's dig deeper. :D

If you remove the same amount of tank water, and just let your ATO replace it with fresh, you will have EXACTLY the same total drop in alkalinity as if you returned the used water to the tank. :)

Then if you correct for salinity later with a mix like Reef Crystals that has more alk than your tank, you will find the alkalinity increases over time. lol

So none of the options are "perfect". :D
That said, I'll repeat that I'd send it to a waste jug. :)

 

[JonasRoman]

Ah, but let's dig deeper. :D

If you remove the same amount of tank water, and just let your ATO replace it with fresh, you will have EXACTLY the same total drop in alkalinity as if you returned the used water to the tank. :)

Then if you correct for salinity later with a mix like Reef Crystals that has more alk than your tank, you will find the alkalinity increases over time. lol

So none of the options are "perfect". :D
That said, I'll repeat that I'd send it to a waste jug. :)

Good comment Randy:)
In the scenario when you through away the sample water you will replace that part with salt(automatically with the ATO to keep salinity constant. )So there will only be an alteration if the saltmix has a different KH from the tank, thus it could be everything between a slight lowering, no difference at all, or slight increasing.
If it is a small/negligable alteration already when not replacing with salt(method putting the acid back to the tank) this method with replacing loosen water with new saltwater, will be even more negligable. So there is difference between the methods in that direction that the method to through the sample away, has a much much smaller impact in dKH. As it is difference, i choose that method with a minimum of impact of dKH. As you too, so we agree:-)

If we again compare, my example above (200l, 20 measures a day, one week, 8.5dKH) the dKH will decrease by 0.3dKH over a week if we put he sample back. If we instead through it away, and replace the loosen water with salt the only difference will be the difference in the saltmix/tankdKH. That is for sure often not measurable. Say that we uses a saltmix with a dKH of 10, and we have 8.5 in the aquarium, then we will in the same example only get a difference(increase) of dKH 0.05 (instead of 0.3 if we put the sample back to the system). In that example I have counted with a salt with a quite big difference in dKH. Mostly we have not that, so the difference will be even less. The difference is so low so we will not be able to even detect it.
Well, we all know the theories, and seems to like the same method. That is valuable for me to know:-)
Thanks for good discussion and inputs:-)

 

[Randy Holmes-Farley Verified Community Expert]

Sounds good.

Good luck with all your developing, folks! :)

 

[SCSI]

I don't think we're done here just yet :)

While talking about amounts of waste produced, we should keep in mind the difference between sample size and the total volume of tank water required for one complete measurement cycle. Obviously there is a need to rinse the machine to flush the old fluid from the circuits prior to the next measurement and in many cases it takes more water than the sample size itself. As I understand what KHG folks are saying, their sample size is 20ml but the total volume consumed is 50 ml per test. Guessing some of that is for rinse.

 

[biom]

Putting the sample back into tank in not a big issue, this negligible lowering of kH will not accumulate with time, it will last only to next measurement followed by buffer addition.
There could be problem with ionic balance if the acid used is H2SO4 or HCl, but will be really small especially if there are regular WC.

 

[JonasRoman]

Sounds good.

Good luck with all your developing, folks! :)

Many thanks:-)

 

[Randy Holmes-Farley Verified Community Expert]

I don't think we're done here just yet :)

While talking about amounts of waste produced, we should keep in mind the difference between sample size and the total volume of tank water required for one complete measurement cycle. Obviously there is a need to rinse the machine to flush the old fluid from the circuits prior to the next measurement and in many cases it takes more water than the sample size itself. As I understand what KHG folks are saying, their sample size is 20ml but the total volume consumed is 50 ml per test. Guessing some of that is for rinse.

That is a concern when sending the sample to waste, but not when recycling it into the tank since it is not neutralized with acid. :)

 

[JonasRoman]

I don't think we're done here just yet :)

While talking about amounts of waste produced, we should keep in mind the difference between sample size and the total volume of tank water required for one complete measurement cycle. Obviously there is a need to rinse the machine to flush the old fluid from the circuits prior to the next measurement and in many cases it takes more water than the sample size itself. As I understand what KHG folks are saying, their sample size is 20ml but the total volume consumed is 50 ml per test. Guessing some of that is for rinse.

No it doesn't´t with my machine;-) I have some algorithms that it is only consuming exact the water that the sample takes. My rinsing algoritms take no extra water from the system, and I have done a lot of experiments with different algorithms and can promise, there is absolutely no difference in dKH with two measures following each other indicating that the rinsing procedure is enough:_). And I use NO extra rinsing buckets, no need of osmosewater etc. So, "my" test-volume is 50 ml, and no more is nettoextracted.

BUT, with this said, I consider to include a function that a pump will automatically pump back fresh saltwater in exact same amount that a measure cycle is consumed. The customer can choose themselves, either have some eye on the salinity(which is not an issue), OR, invest in the other version with this adding feature (which is not expensive at all). Then the question about measure volume is not an issue at al. I still think this is better as the precision and accuracy has higher priority.

 

[JonasRoman]

Putting the sample back into tank in not a big issue, this negligible lowering of kH will not accumulate with time, it will last only to next measurement followed by buffer addition.
There could be problem with ionic balance if the acid used is H2SO4 or HCl, but will be really small especially if there are regular WC.

A lot of needed buffer-actions of a KH-machine will lead to wrong balance between Kh/Ca. Thus, this is another reason of having a method that not itself lowering the dKH. But I agree, in most cases there is very small impact on the dKH, but in small systems and high measure frequency you will with time get wrong balance between KH/Ca if you take the sample water to the aquarium of that reason you self mentions.
The acid itself is not important as it is only H-ions, because the S-content in sulfuric acid is totally negligable. In a natural seawater we have a S-content of 900ppm, thus one of the macroelements. So in that point if view it is totally negligable with the S-adding.

 

[Daniel@R2R Verified Admin]

This thread is full of great info! Super excited to see these new Alk measuring/monitoring devices coming to be!

 

[L Driehuis]

Did somebody check out the "Automated Spectrophotometric Analyzer for Rapid Single-Point Titration of Seawater Total Alkalinity"?

The fixed ratio is a great idea. I am wondering if this can be done using cheaper 2 way valves. I only do not understand how the excess acid is measured (equations 8 and 9).

 

[Dennis Cartier]

I played with SIA years ago just for fun of it. Here's one example (below) which had well over $2k in parts in it (if bought new). It had sample volume of around 0.4cc and reagent 0.1cc per measurement if I recall correctly. Teflon plunger in that syringe pump didn't like the salt crystals and started to leak in a few months... :)

Thanks,
Kirill

Kirill, did you ever try any other syringes in the pump or just the one? I have a couple of syringe pumps with 12 position heads that I was planning to use for tank duty and am wondering if they will suffer the same fate as yours or if a different syringe using a different material can be used that does not fall victim to the salt crystal problem. Were you flushing the syringe compartment with RODI after every use?

Dennis

 

[Larry L]

Thanks very much to everyone contributing to this thread, this is great information!

 

[karimwassef]

Very interesting. Any updates?

 

[Dennis Cartier]

Kirill (@SCSI), do you have any other threads on here (or RC) with more details about the various version of titrator's that you have built? I have seen your original one from 2007, but am wondering if you have anything newer. I am curious to hear about your successes, and more importantly, your failures.

Dennis