Sciencemadness Discussion Board

Treating waste water from fish farms.

White Yeti - 18-8-2011 at 11:52

Hello everyone.

I have a friend who owns a small fish farm and he once asked me if he could use the ammonia rich waste water from fish tanks to fertilize crops. I told him that ammonia is too toxic to be used as fertilizer and that the would kill crops rather than fertilize them.
However, this got me thinking, is there a way to treat waste water from fish farms and fertilize plants with it at the same time.
I thought of a process that might work, but I wanted expert feedback as to whether or not this process is feasible on a large scale. If this process won't work, I am open to constructive criticizm.

The process:
As ammonia dissolves in water, it forms ammonium hydroxide, a base. This water is then chilled and carbon dioxide is bubbled through it to produce carbonic acid. The carbonic acid dissociates into bicarbonate and a proton. Acid-base titration occurs and ammonium bicarbonate is formed. The ammonium bicarbonate is then reacted with epsom salt until bubbles of carbon dioxide gas cease to form. This reaction yields ammonium sulphate (a fertilizer), carbon dioxide, magnesium carbonate and water. Carbon dioxide is recycled, magnesium carbonate is filtered and the weak ammonium sulphate solution is used to fertilize plants.

What do you guys think? Is this process worth a try? Are there any improvements that can be made to this process?

Thank you for your time.

Megamarko94 - 18-8-2011 at 12:03

actually ammonia is used to fertilize crops (pure anhydrous ammonia ) which is the main source of nitrogen for plants...
but waste water from fish probably has a lot bacteria i guess that would demage plant (not sure about this, my opinion....

[Edited on 18-8-2011 by Megamarko94]

White Yeti - 18-8-2011 at 12:19

Hmm, strange. I know rhizobia bacteria in legumes produce ammonia, but in very small quantities, far lower than what would cause damage to cells. Anhydrous ammonia can't be used to fertilize crops because the plants have no way of absorbing such a gas, unless it is dissolved in water. The ammonia would then turn into ammonium hydroxide which exists in equilibrium with ammonia gas, which is harmful to cells of any kind.
Ammonia is used to kill bacteria.... Any bacteria present in the water would have been killed or at least weakened by the ammonia excreted by fish...

redox - 18-8-2011 at 12:32

No, :mad:anhydrous ammonia is definitely used to fertilize crops. Many farms use it. What is toxic to a human may not be toxic to plants, and vice-versa.

The ammonia is injected into the soil, where it reacts with the moisture present and is absorbed into the roots.

Please see "Using Anhydrous Ammonia Safely on the Farm" by
John M. Shutske if you don't believe me.

I would assume that the ammonia-rich water could be used on the farm strait from the fish tanks.

White Yeti - 18-8-2011 at 12:44

"Phytotoxicity of foliar-applied urea
Michael J. Krogmeier, Gregory W. McCarty, and John M. Bremner*
+ Author Affiliations

1Department of Agronomy, Iowa State University, Ames, IA 50011
Abstract
Recent work in our laboratory showed that the adverse effect of urea fertilizer on seed germination and seedling growth in soil is due to ammonia produced through hydrolysis of urea by soil urease (NH2CONH2 + H2O → 2NH3 + CO2) and can be eliminated by amending the fertilizer with a small amount of a urease inhibitor such as phenylphosphorodiamidate. Because the leaf-tip necrosis often observed after foliar fertilization of plants with urea is usually attributed to ammonia formed through hydrolysis of urea by plant urease, we studied the possibility that this necrosis could be eliminated or reduced by adding phenylphosphorodiamidate to the urea fertilizer."

Ammonia gas is indeed toxic to plants. It needs to be transformed into an ammonium salt so that proper assimilation can take place. I haven't found a single reliable source so far that stated ammonia is not toxic to plants.

gutter_ca - 18-8-2011 at 12:48

Aquaponics. Use biofiltration, grow the right bacteria to run the nitrogen cycle, and grow plants directly in the fish water, cleaning the water for the fish in the process!

The WiZard is In - 18-8-2011 at 13:46

Quote: Originally posted by White Yeti  
Hello everyone.

I have a friend who owns a small fish farm and he once asked me if he could use the ammonia rich waste water from fish tanks to fertilize crops. I told him that ammonia is too toxic to be used as fertilizer and that the would kill crops rather than fertilize them.



I remember years ago being out sending woodchuck to the
big bean field in the sky. The farmer on the next field was
spreading chicken manure. What a smell and its
ammonia fumes caused ones eyes to burn when the wind
changed direction. Granted this was being applied before planting
corn.

If you read in the instructions for using 4-legged animal manure
you are advised to let it ferment before using. I would posit
this is to let la ammonia gas off.

Google anhydrous ammonia fertilizer and see
what is said bout it.


djh
----
My neighbour disappointed me.
I asked him 'bout the cart of
fertilizer I would see in his yard
once a year. Ammonium nitrate
asked I - visions of me putting my
generator and shop vac in the back
of my ATV and going out at night
to vacuum some up.

Urea. Oh well.

redox - 18-8-2011 at 14:38

Quote: Originally posted by White Yeti  


Ammonia gas is indeed toxic to plants. It needs to be transformed into an ammonium salt so that proper assimilation can take place. I haven't found a single reliable source so far that stated ammonia is not toxic to plants.


If this is true then what are tanks of anhydrous ammonia doing in farm fields?

White Yeti - 19-8-2011 at 02:34

I found more info relevant to this topic:

Anhydrous ammonia is used to replenish soil BEFORE crops are planted. This allows bacteria to convert ammonium into nitrite and then to nitrate, which is useful to plants. Now, since water from fish tanks is constantly removed, it cannot be practically stored until it can be used to fertilize soil (before crops are planted). Ammonium sulphate however, can be used to fertilize crops while they are growing because it is much less toxic.

Neil - 19-8-2011 at 05:25

Quote: Originally posted by White Yeti  
I found more info relevant to this topic:

Anhydrous ammonia is used to replenish soil BEFORE crops are planted. This allows bacteria to convert ammonium into nitrite and then to nitrate, which is useful to plants. Now, since water from fish tanks is constantly removed, it cannot be practically stored until it can be used to fertilize soil (before crops are planted). Ammonium sulphate however, can be used to fertilize crops while they are growing because it is much less toxic.



Dear god, the unneeded arguing.

Anhydrous ammonia gets used before planting, during planting and after planting. You just only use a wee bit as opposed to soaking the entire field.

http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agd...

Which is why meth heads rob it off fields all year round as opposed to the crack of dawn on a fine spring morning.


For the proud yuppie
http://earthfirst.com/indoor-%E2%80%98river-ecosystem%E2%80%...


For the essential farmer
http://www.northernaquafarms.com/aquaphonics.html


I've been looking at these things for a while. Your biggest problem is likely keeping enough oxygen in the waste to keep the roots alive and to keep the waste from becoming super anoxic.

Take a look at fluidized bed sand bubble scrubbers.

bbartlog - 19-8-2011 at 06:25

If the fish can live in the water, it's not concentrated enough to be toxic to plants. You're looking for a solution to a problem that isn't there.

(edit): also, if you want to create the sulfate, CaSO4 is surely more economical than MgSO4.

[Edited on 19-8-2011 by bbartlog]

not_important - 19-8-2011 at 06:32

So I did a search using the thread title as the target, and on the 1st page of results were the attached PDF and :

Wastewater use in aquaculture http://www.fao.org/docrep/T0551E/t0551e09.htm


Fish hatchery management http://www.archive.org/details/fishhatcherymana00pipe


and several others.

For the love of Goddess, people, learn how to do searches first. After that ask questions, although further reading usually helps with those too.



Attachment: Open-air treatment of wastewater from land-based marine fish farms.pdf (933kB)
This file has been downloaded 896 times

gutter_ca - 19-8-2011 at 13:03

http://en.wikipedia.org/wiki/Aquaponics

http://www.backyardaquaponics.com/

497 - 19-8-2011 at 15:33

Duckweed is the answer... then feed it back to the fish. It is proven technology, at least for use with intensive tilapia cultivation.

If the fish can live in it, most any plant will be fine. Duckweed is just nice because it requires no soil, and less surface area than other plants because it can reproduce (and yield high protien biomass) at a higher rate than terrestrial plants.