Aquaponic Gardening

A Community and Forum For Aquaponic Gardeners

I found this diagram helpful when explaining the nitrification cycle. Hope it is some use for y'all.

.


Views: 1700

Reply to This

Replies to This Discussion

Is it this you are looking for The Aquaponic Source

If so, there is a link to it at the top of the page as well "Shop"


Darryl Hinson said:
Kobus... .sorry for taking your time......how do i get in touch with sylvia bernstein...
i cant find her email......
i want to ask her the name of her husband's company.....forgot it...
thanks.
d.
@ Kobus Jooste (or anyone that knows definitively)

Does urea break down into 2 ammonia via urease as follows?

1 mol CH4N2O + 1 mol H2O + energy => 2 mol NH3 + CO2
Hey Darryl, here I am. You can also go into Members, search for anyone you want, click on them and send them a comment or direct email if you have Friended them. But the link TC included is right about TheAquaponicSource...except that it is my company....I hired my husband because he is cute and charming :). Oh, and he just pointed out that he is also competent and free. An excellent hire any way you look at it!



Darryl Hinson said:
Kobus... .sorry for taking your time......how do i get in touch with sylvia bernstein...
i cant find her email......
i want to ask her the name of her husband's company.....forgot it...
thanks.
d.
So I just had this comment posted on my blog post about Speeding up Cycling. I'm interested in what you science gurus have to say about it...
_________________________

I am not an expert but this will help a little. I hope.

There two bacterial species involved. Nitrosomonas sp. bacteria which oxidize ammonia to nitrite, while Nitrobacter bacteria convert nitrite to nitrate, with both species utilising the energy released by the reactions. This seemingly simple process involves a complex series of reactions that can be summarised in chemist shorthand as:

For Nitrosomonas: (55NH4+)+(76 O2)+(109HCO3-) –> (C5H7O2N)+(54NO2-)+57H2O + 104H2CO3. This 104H2CO3 will break into H2O and CO2

For Nitrobacter: (400NO2-)+(NH4+)+ 4H2CO3 + (HCO3-) + 195 O2 C5H7O2N + 3H2O + (400NO3-)

What these reactions tell us in plain language is that;

in equation (1), ammonia (NH4+) is combined with oxygen and hydrogen carbonate to produce bacterial cell mass, nitrite (NO2-) , water and carbonic acid,

in equation (2), nitrite is combined with ammonia, carbonic acid, hydrogen carbonate and oxygen to produce bacterial cell mass (C5H7O2N), water and lots of nitrate (NO3-).

While this all seems a bit grand and a bit unnecessary there are two important points that come out of these equations.

Approximately 4.3 mg O2 are consumed for every mg of ammonia-nitrogen oxidised to nitrate-nitrogen

8.64 mg of alkalinity in the form of HCO3- are consumed per mg of ammonia-nitrogen oxidised. This is quite a substantial amount of alkalinity and will over a period of time dramatically change the character of the pond water, affecting both hardness and pH stability. It is also an acidifying process, producing a gradual build up of nitric acid. It should also be noted that the process does not remove any nitrogen from the system; merely changing it from one form to another.

nitrification uses substantial amounts of oxygen and carbonate, reducing water hardness and buffering capacity and has a mild acidifying effect.

So you should use ammonium bicarbonate (NH4HCO3) (to start a cycle and keep the bacteria alive)which has a stable PH (Buffer effect ) of 6.36 instead of pure amonia NH4OH which has a PH of 9 more or less and it does not act as a buffer.
Duh um,
ok being definitely not a chemist I read only part of this and it says to me......

The whole process uses dissolved oxygen and carbonate and has an acidifying effect (yep knew this but it's worth repeating)

The new bit to me is that last paragraph recommending ammonium bicarbonate. Rather makes sense to me, however is that a material easily gotten? It really isn't that hard to add some calcium carbonate as a buffer and just use plain ammonia or cheaper still for those not yucked out bottled aged humonia.
So can someone explain to me in simple Chemistry for Dummies language why pH tends to rise during the nitrification process, and fall once the system is fully cycled? Thanks!
Are we sure it actually rises because of the nitrification process? Or does it just seem that way because most people take their first pH reading on water that has just come out of the pipe and has a false low pH reading because of dissolved carbon dioxide? And then they assume that the pH of 7 of the water right out of the pipe is real and then a few days later after they start cycling and do another pH test and find the pH has risen to 8 and they blame it on cycling?
My well water will read 7 fight out of the pipes, if I bubble it for a day it will read between 8 and 8.2 depending on time of year/amount of rain. My big system hung around a pH of 7.9-8 through initial cycle up until it was nearly cycled at which point the pH dropped pretty quickly to 7.6 and stayed there because of my shells.

Another culprit I've seen mess with pH is algae.


Sylvia Bernstein said:
So can someone explain to me in simple Chemistry for Dummies language why pH tends to rise during the nitrification process, and fall once the system is fully cycled? Thanks!
I've had it in the back of my head that that is what happens, and Dr. Lennard let me put it in the Rules document and he didn't let get away with putting anything in there that he didn't agree with. Maybe TC is right. Maybe it is just the cumulative effect of adding in high pH tap water without the downward buffering effect of the nitrification process...

OK ..... I THINK this explains why I had an ammonia and nitrate spike when I finally managed to get my pH to move down ( albeit too rapidly).. and I did the right thing putting the air stones on in the tank? Wow- chemistry was a long time ago!
Kobus Jooste said:
For the Nitrification process:

2 mole NH4 + 4 mole O2 => 2 mole NO3 + 4 mole H + 2 mole H2O + energy.
While the Nitrogen component in the equations (Nitrosomonas and Nitrobactor reactions) stay at a 1:1:1 ratio (Thus 1g of ionized ammonia is converted to 2.56g of nitrite and then to 3.45g of nitrate. Because NH3 and NO3 each contains the same amount of Nitrogen, but the rest of the molecular weight differs, you have an increase in weight of waste materials down the Nitrification line while keeping your nitrogen ratios the same.), 36g of ionized ammonia (or 28g of ammonia-nitrogen) is burned by 128g of oxygen producing 124g of nitrate (or 28g of nitrate-nitrogen) + 4g of hydrogen + 36g of water + energy. This not only helps put the process in a bit of light around waste treatment, but also why we can end up with such major Nitrate readings, why we need so much DO and why we need to have the alkalinity (buffering the H production). Now that you know this bit, you can reverse engineer the Ammonia production based on your fish food protein content (there are a few variations of how to get there) and within a short time, you have an understanding of the amount of oxygen and Alkalinity you need to deal with each gram of fish food tossed into your system. Around 7g of alkalinity (usually your lime or coral sand addition) is required to completely Nitrify a gram of Ammonia.
Yep, air stone a good thing. Moving pH fast bad thing. Hope it's all worked out. :)

Reply to Discussion

RSS

© 2022   Created by Sylvia Bernstein.   Powered by

Badges  |  Report an Issue  |  Terms of Service