Purging (Cooking) GFO possible?

[chris melb]

Been reading about purging (cooking) live rock whereby autotrophic bacteria strips bound phosphate out of rock (turgoing) and wondered whether the same could be done for GFO? I understand there is another way to regenerate GFO using chemicals but prefer not to use this method.

Chris

 

[dkeller_nc]

Some of us with a scientific background have some doubts about the magnitude of the effect of bacteria on dissolution/striping of phosphate on solid substrates. Regardless, the potential issue with doing this to GFO is that you would need to add materials to promote the growth of a bacterial culture - at the very least, a carbon and nitrogen source.

I'm guessing that the end result would be a real mess - a stinking bacterial culture that would potentially irrevocably clog the pores in the GFO media. The internal porosity of the GFO is critical to its use as a phosphate absorber - the surface area on the outside of the particles contributes very little to the ultimate phosphate-absorbing capacity of the material.

The chemical means of regenerating GFO is very simple and quite safe if one takes reasonable precautions - it's no more hazardous that clearing one's drains with a product like Drano.

 

[stephenhall1987]

Phosphate doesn't absorb into GFO, it binds to it on an atomic level. Idk that bacteria would be able to break those bonds. Here's an article:

http://www.reefkeeping.com/issues/2004-11/rhf/

 

[Hitch08]

Responses like those above remind me of how bad I was in HS Chemistry class.

 

[CStrickland]

I think the idea with bacteria is that they create a little pocket of acid at the surface of the rock, like they slobber on it and then soak up the carbon and phosphate that they need to live and grow. The nutrition that they catch this way becomes part of their body until they die, and what they miss floats away; dead bacteria, their waste, and some leftover minerals make up the detritus that people find on the bottom of the bin that they cook in and water changes take out what the bacteria miss. Turgor is the process that pushes it out of the rock, like a weak current from the bacteria doing their version of breathing.

GFO and rocks / sand (calcium carbonate) attract phos using an ionic bond. It's not as scary as it sounds. This is the HS chem where the teacher would show a pic of a molecule like a little circle (nucleus) with bigger circles around it (electrons) and talk about how the molecule has a negative or positive charge because its last circle is missing an electron so it is sad until it meets another molecule that has an extra and they hook up or whatever because ions.

Fresh gfo has a hydroxide bound to it already (the little OH's pictured in Randy's article linked above), but it would rather hook up with phos, so it kicks hydroxide to the curb and pulls the phos out of our water. Regenerating blasts the gfo with hydroxide again, knocking off the phos to be rinsed away. So it's more like replacing the phos than just breaking it off and leaving an empty space in the rock.

Idk if the gfo bond would respond to the bacteria's little puddle of slobber the same way as people say the rock's bond does. Idk if you could make a nice home for them to eat on the gfo like a rock does either, there's been a few threads about cooking sand and people seem to think its not worth the trouble to figure out a way to let detritus turgor out and fall down (like hang it in a bag, or put a layer of gravel under it) for easy collection. Idk if blasting rock with hydroxide would knock the phos out of it either.
There's a lot I don't know cause I don't have a scientific background, but I did get my GED so that's how much weight you should give this little explanation

 

[Dan_P]

Been reading about purging (cooking) live rock whereby autotrophic bacteria strips bound phosphate out of rock (turgoing) and wondered whether the same could be done for GFO? I understand there is another way to regenerate GFO using chemicals but prefer not to use this method.

Chris

Bacteria can "mine" mineral phosphate.

I am not convinced anyone has actually studied the mechanism of "cooking" live rock. Is it desorption? Is it decomposition of organic material that is liberating phosphate? Is it mineral mining bacteria in action? Live rocks are not a subject of study at universities.

Binding of phosphate to GFO is very stable. It does not desorb too any appreciably degree in water. Sodium hydroxide is needed to displace it. Could bacteria mine GFO bound phosphate? The way phosphate is released from ferric oxide hydoxide in nature is through the reduction of iron (III) to iron (II). So, that won't help you.

I still like the question though.

 

[firebirdude]

http://reefcentral.com/forums/showthread.php?t=1734717

 

[chris melb]

Wow some great posts here, thanks all. I have read (on forums) that live rock "cooking" was achieved via mineral mining bacteria. I have also read a few studies which have shown that phosphate solubilizing bacteria (PSBs) can solubize insoluble phosphate from calcium phosphate (if I read this right - with rates of upto 525mg/l over a 24hr period). This was achieved using a bacterial culture medium SRSM1. Nevertheless, is this not similarhttp://bashanis.org/gmaweb/pdfs/vazquez1.pdf.

 

[chris melb]

Wow some great posts here, thanks all. I have read (on forums) that live rock "cooking" was achieved via mineral mining bacteria. I have also read a few studies which have shown that phosphate solubilizing bacteria (PSBs) can solubize insoluble phosphate from calcium phosphate (if I read this right - with rates of upto 525mg/l over a 24hr period). This was achieved using a bacterial culture medium SRSM1. Nevertheless, I do wonder if this process would work with GFO, granted a carbon, nitrogen source would be needed. Although I don't recall nitrogen being used when folks are cooking live rock.

Ref:http://bashanis.org/gmaweb/pdfs/vazquez1.pdf.

Dkeller_NC, can I ask what the reasons are for having doubts about the effectiveness of PSBs to solubise rock bound phosphate in reef aquaria? Ive often wondered how this happens given rock is often covered with life forms like coraline algae, possibly preventing bacteria from getting into the rock and turgoing?