final design ideas on large nitrate filter

[johnptc]

i think this is the best bet so far..........

use a 6 ft high plastic water tank filled with kaldness k1 media which is slightly buoyant.

mount the filter tank above the fish tank.........pump water into the top and gravity feed out the bottom with a high loop to keep the tank filled with water for anoxic conditions.

the bugs need to be feed organic carbon w2ith for wastewater treatment would be methanol............

There is a non toxic product called micro cg which can be used in lieu of the methanol....

this is metered in small amounts to feed the bacteria.......

N2 gas is released

still thinking about backwash and nitrogen burping.......

any thoughts ????

 

[fishdance]

What is the rational for having the filter tank over the main stock tank? Is there a benefit to outweigh the risks? I can see potential drainage blockage(s) creating back/overflow which will dump the filter contents (anaerobic water) straight into your main tank... or have I mis-read your design. Suspending a 6 foot high tank full of water over your tank will also be logistically problematic and expensive. Since your filter tank is full of water anyway, this filter tank doesnt need to be above your stock tank, just its water level does. ie Even 60cm head height between the two tanks is plenty enough for gravity drainage to occur. Therefore the anaeroic tank can be placed many meters away. What total volume do you need it? Why dont you make it a long thick pipe instead of a tank? (Thick diameter pipe is expensive but multiple thin pipes can hold same volumes economically)

Also almost all recirculating aquaculture systems, put their output of aerobic filter water through a gas exchanger (pure oxygen) to restore depleted dissolved oxygen levels or higher before returning the water to the main stock tank(s) and your filter will have MUCH lower D.O. content than this so that may be a problem. Just another point against having your filter over your stock tank.

How will you monitor and maintain anaerobic conditions? Simply by reduced inflow rate? Will channelling occur or does this media type move easily? Will you ever need to backwash? I guess anaerobic bacteria die off too with accumulation of crud. If you do want to backwash then an upflow system would be more suitable than down/top feed. I suspect nitrogen gas build up will create enough pressue to burp itself (eventually). How will you distribute the methanol/micro cg ? I have read sodium acetate can be used but this doesnt have organic carbon so i am not sure how..

I havent read up on denitrifying filters as much as you have John but I am happy to bounce ideas about and hopefully post some constructive comments.

 

[johnptc]

What is the rational for having the filter tank over the main stock tank? Is there a benefit to outweigh the risks? I can see potential drainage blockage(s) creating back/overflow which will dump the filter contents (anaerobic water) straight into your main tank... or have I mis-read your design. Suspending a 6 foot high tank full of water over your tank will also be logistically problematic and expensive. Since your filter tank is full of water anyway, this filter tank doesnt need to be above your stock tank, just its water level does. ie Even 60cm head height between the two tanks is plenty enough for gravity drainage to occur. Therefore the anaeroic tank can be placed many meters away. What total volume do you need it? Why dont you make it a long thick pipe instead of a tank? (Thick diameter pipe is expensive but multiple thin pipes can hold same volumes economically)

Also almost all recirculating aquaculture systems, put their output of aerobic filter water through a gas exchanger (pure oxygen) to restore depleted dissolved oxygen levels or higher before returning the water to the main stock tank(s) and your filter will have MUCH lower D.O. content than this so that may be a problem. Just another point against having your filter over your stock tank.

How will you monitor and maintain anaerobic conditions? Simply by reduced inflow rate? Will channelling occur or does this media type move easily? Will you ever need to backwash? I guess anaerobic bacteria die off too with accumulation of crud. If you do want to backwash then an upflow system would be more suitable than down/top feed. I suspect nitrogen gas build up will create enough pressue to burp itself (eventually). How will you distribute the methanol/micro cg ? I have read sodium acetate can be used but this doesnt have organic carbon so i am not sure how..

I havent read up on denitrifying filters as much as you have John but I am happy to bounce ideas about and hopefully post some constructive comments.

thank you for your input !!!!!!!!!!!

i was going to mount the filter ( 2 each 500gallon tanks)
up in the air due to space limitations.....near but not over the tank.

i didnt think about the do.........at 1000 gph it may not matter as the rest of the filtration is at 450 gpm....but some type or aeration could not hurt ...

the media is slightly positive bouyant.....it may self wash a little......working on ideas for the release of nitrogen gas and backflushing.