Controllable deep sand beds - a discussion thread

[Dr. Dendrostein]

@Lasse, is quick to listen, slow to answer. Very wise man.

 

[Scrubber_steve]

Has anyone read Paul B's thread about his 47 year old tank? He runs a reverse flow undergravel filter which is conceptually not so different from what is being discussed here, just less complicated.

https://www.reef2reef.com/threads/how-to-make-a-tank-last-for-40-years-with-few-problems.290237/

I read an early article of Pauls regarding his use of the reverse flow undergravel filter. His intention then was a slow flow through it, & he expected it would act as a nitrifying & de-nitrifying filter.
He now happily admits to having very high NO3 levels so the de-nitrification part didn't work out for him.

 

[Sallstrom]

Do you think it would be possible to use something like the aqua medic denitrators and replace the bioballs with sand and coral rubble? A carbon source is added through a dosing pump and the probe could be linked to an external dosing pump would add a few litres of fresh tank water every hour, the redox can therefore be easily maintained at -200mv, the internal circulation pump would stop hydrogen sulphide pockets forming. So you end up with a semi fluidised sand bed with zero oxygen.
https://www.drsfostersmith.com/Media/PDF/19139-NitrateReductorManual.pdf
I’ve built something similar using an ALR2 reactor but have used siporax as the media, but now wondering if sand/ coral rubble might be better.

Yes, that would be the same I think. But probably better than my setup due to the internal circulation. So a little better but with one more pump

/ David

 

[Dr. Dendrostein]

I'm gonna grill some steaks. Be back soon

 

[Lasse]

Bob Goemans correctly uses the term 'anoxic' to describe a zone that contains an oxygen level of approximately 0.5 to 2.0 mg/litre and >>> directly due to this<<< destructive denitrification occurs ( NO3 to nitrogen gas).

The often & incorrectly term used 'anaerobic' represents a zone that contains less oxygen than the anoxic condition, and >>> directly due to this <<< the ammonification form of denitrification occurs (NO3 is converted back to ammonia). Hydrogen sulphide will also form in an anaerobic zone, so creating such an environment must be avoided.

Substrate grain size & depth, along with flow rate through, are key considerations for success in this type of nutrient processing method especially if a thick substrate is being utilised. Removal of organic particulate matter from the water entering the substrate would be necessary. But over time channelling can occur leaving dead spots - anaerobic zones. If fine sediments eventually have high organic matter loading they tend to go anoxic/anaerobic at very shallow depths - between a few centimetres to a few millimetres.

This method is not set & forget. Organic matter build up in the substrate, compaction of the substrate & channelling of flow through the substrate can cause subtle changes that can lead to disaster over time.

IMO - there is a lot of misunderstandings in this. It is true that denitrification (i total) can take place when oxygen is present in the water but it is more effective during anaerobic situations. In reality - denitrification can´t take place in the singel cells if oxygen is present in that cell. Why? Let us first define the term denitrification - normally this term means (from this paper)

“microbial reduction of nitrate or nitrite coupled to electron transport phosphorylation resulting in gaseous N either as molecular N2 or as an oxide of N.” The key to denitrification as defined is the availability of the N oxides, nitrite (NO2−) or nitrate (NO3−)

There is other bacterial pathways of transform some dissolved inorganic nitrogen in water and soil to other species of inorganic N. NO3 to NH4/NH3 by the anaerobic DNRA pathway (Dissimilatory nitrate reduction to ammonium). NH3/NH4 to N2 and water by the anaerobic anammox pathway and NO3 to N2 gas by autotrophic anaerobic sulphur bacteria are some of the pathways. According to @Jomama and his alkalinity problems with the last process - this article - chapter 4 maybe can be interesting.

The "true" denitrification process include a lot of bacteria that can be defined as facultative anaerobs (optional anaerobs) In other words - they can change between aerobic and anaerobic environments. In aerobic environments they use oxygen as an electron acceptor in the cell respiration cycle (electron donor NADH) In anaerobic environment - they use NO3 as electron acceptor (the whole molecule !) but in order to be effective - it needs DOC (Dissolved Organic Carbon) as an electron donor. As I see it - the single cell will chose the most effective pathway and that is oxygen if it is present - otherwise it will take NO3 if NO3 and DOC is available. There is other potential electron donors but DOC is the most effective but it can be differences between DOC species too. IMO - denitrification at the level of single cells - it can only happens in anaerobic environment (absence of oxygen in the cell process) but at the biofilm level - there can be som oxygen dissolved in the water.

However - there is a need of DOC in order to have an effective denitrification process. Normally - you add this from an external source but it is possible in a anaerobic bacterial digestion of organic matter to produce these wanted DOC internally. But in order to do that - you need a lot of detritus to form this oxygen free environment. Is it dangerous to do this - maybe if you do not make it controllable in one or another way but in the long run and managed the right way - nema problema IMO.

The bad guy that always will occur in discussion around anaerobic pathways and the reef aquaria - hydrogen sulphide - how bad is this guy? Hydrogen sulphide gas is deadly but it is easily oxidized by oxygen - hence in normal operation it is no problems with it. Hydrogen sulphide gas that slip out from my sand bed during normal operations will be oxidized directly. This is the reasons for some of my constructions with this reversed flow remote deep sand bed.

1. I have my refugium in the same apartment (macro algae produce oxygen during the light period - in my case night)
2. I have the refugium/sand bed directly after the DT and get the full flow over the sand bed (oxygen production from micro algae and zooxanthella and good movement of the water from streamers)
3. I have my skimmer directly after the refugium/sand bed (oxygen transfer from air to water through the skimmer)
4. I have an oxydator placed in the return apartment (oxygen additions from catalyzed hydrogen peroxide)

Hence - the risk for deadly hydrogen sulphide to my DT in normal operation - negligible

However - a power failure can be a risk. If I´m home - I can use both hydrogen peroxide direct to the water and to move my oxydators (I have one as reserv) to the DT and refugium.
If I am not home - the last frontier is that the return pump will not start before the skimmer has run for 5 minutes and be able to handle the hydrogen sulphide coming down from the refugium. When I´m away or prolonged periods - I place an oxydator in the refugium too (a small one)

DOC that will be added to my plenum directly affect my ORP level - an indication that DOC is a limited factor for my anaerobic bacteria - they directly rise their reduction rate nd ORP going down.

The reason why I chose 0 mV as target level for my plenum is that I expect that the ORP will go further down in the sand bed My pH level is around 7.9 in the plenum. pH in DT just now 8.3

Sincerely Lasse

 

[Dr. Dendrostein]

IMO - there is a lot of misunderstandings in this. It is true that denitrification (i total) can take place when oxygen is present in the water but it is more effective during anaerobic situations. In reality - denitrification can´t take place in the singel cells if oxygen is present in that cell. Why? Let us first define the term denitrification - normally this term means (from this paper)



There is other bacterial pathways of transform some dissolved inorganic nitrogen in water and soil to other species of inorganic N. NO3 to NH4/NH3 by the anaerobic DNRA pathway (Dissimilatory nitrate reduction to ammonium). NH3/NH4 to N2 and water by the anaerobic anammox pathway and NO3 to N2 gas by autotrophic anaerobic sulphur bacteria are some of the pathways. According to @Jomama and his alkalinity problems with the last process - this article - chapter 4 maybe can be interesting.

The "true" denitrification process include a lot of bacteria that can be defined as facultative anaerobs (optional anaerobs) In other words - they can change between aerobic and anaerobic environments. In aerobic environments they use oxygen as an electron acceptor in the cell respiration cycle (electron donor NADH) In anaerobic environment - they use NO3 as electron acceptor (the whole molecule !) but in order to be effective - it needs DOC (Dissolved Organic Carbon) as an electron donor. As I see it - the single cell will chose the most effective pathway and that is oxygen if it is present - otherwise it will take NO3 if NO3 and DOC is available. There is other potential electron donors but DOC is the most effective but it can be differences between DOC species too. IMO - denitrification at the level of single cells - it can only happens in anaerobic environment (absence of oxygen in the cell process) but at the biofilm level - there can be som oxygen dissolved in the water.

However - there is a need of DOC in order to have an effective denitrification process. Normally - you add this from an external source but it is possible in a anaerobic bacterial digestion of organic matter to produce these wanted DOC internally. But in order to do that - you need a lot of detritus to form this oxygen free environment. Is it dangerous to do this - maybe if you do not make it controllable in one or another way but in the long run and managed the right way - nema problema IMO.

The bad guy that always will occur in discussion around anaerobic pathways and the reef aquaria - hydrogen sulphide - how bad is this guy? Hydrogen sulphide gas is deadly but it is easily oxidized by oxygen - hence in normal operation it is no problems with it. Hydrogen sulphide gas that slip out from my sand bed during normal operations will be oxidized directly. This is the reasons for some of my constructions with this reversed flow remote deep sand bed.

1. I have my refugium in the same apartment (macro algae produce oxygen during the light period - in my case night)
2. I have the refugium/sand bed directly after the DT and get the full flow over the sand bed (oxygen production from micro algae and zooxanthella and good movement of the water from streamers)
3. I have my skimmer directly after the refugium/sand bed (oxygen transfer from air to water through the skimmer)
4. I have an oxydator placed in the return apartment (oxygen additions from catalyzed hydrogen peroxide)

Hence - the risk for deadly hydrogen sulphide to my DT in normal operation - negligible

However - a power failure can be a risk. If I´m home - I can use both hydrogen peroxide direct to the water and to move my oxydators (I have one as reserv) to the DT and refugium.
If I am not home - the last frontier is that the return pump will not start before the skimmer has run for 5 minutes and be able to handle the hydrogen sulphide coming down from the refugium. When I´m away or prolonged periods - I place an oxydator in the refugium too (a small one)

DOC that will be added to my plenum directly affect my ORP level - an indication that DOC is a limited factor for my anaerobic bacteria - they directly rise their reduction rate nd ORP going down.

The reason why I chose 0 mV as target level for my plenum is that I expect that the ORP will go further down in the sand bed My pH level is around 7.9 in the plenum. pH in DT just now 8.3

Sincerely Lasse

That's a lot of info.. Well said @Lasse. Making me hungry again.

 

[Dr. Dendrostein]

IMO - there is a lot of misunderstandings in this. It is true that denitrification (i total) can take place when oxygen is present in the water but it is more effective during anaerobic situations. In reality - denitrification can´t take place in the singel cells if oxygen is present in that cell. Why? Let us first define the term denitrification - normally this term means (from this paper)



There is other bacterial pathways of transform some dissolved inorganic nitrogen in water and soil to other species of inorganic N. NO3 to NH4/NH3 by the anaerobic DNRA pathway (Dissimilatory nitrate reduction to ammonium). NH3/NH4 to N2 and water by the anaerobic anammox pathway and NO3 to N2 gas by autotrophic anaerobic sulphur bacteria are some of the pathways. According to @Jomama and his alkalinity problems with the last process - this article - chapter 4 maybe can be interesting.

The "true" denitrification process include a lot of bacteria that can be defined as facultative anaerobs (optional anaerobs) In other words - they can change between aerobic and anaerobic environments. In aerobic environments they use oxygen as an electron acceptor in the cell respiration cycle (electron donor NADH) In anaerobic environment - they use NO3 as electron acceptor (the whole molecule !) but in order to be effective - it needs DOC (Dissolved Organic Carbon) as an electron donor. As I see it - the single cell will chose the most effective pathway and that is oxygen if it is present - otherwise it will take NO3 if NO3 and DOC is available. There is other potential electron donors but DOC is the most effective but it can be differences between DOC species too. IMO - denitrification at the level of single cells - it can only happens in anaerobic environment (absence of oxygen in the cell process) but at the biofilm level - there can be som oxygen dissolved in the water.

However - there is a need of DOC in order to have an effective denitrification process. Normally - you add this from an external source but it is possible in a anaerobic bacterial digestion of organic matter to produce these wanted DOC internally. But in order to do that - you need a lot of detritus to form this oxygen free environment. Is it dangerous to do this - maybe if you do not make it controllable in one or another way but in the long run and managed the right way - nema problema IMO.

The bad guy that always will occur in discussion around anaerobic pathways and the reef aquaria - hydrogen sulphide - how bad is this guy? Hydrogen sulphide gas is deadly but it is easily oxidized by oxygen - hence in normal operation it is no problems with it. Hydrogen sulphide gas that slip out from my sand bed during normal operations will be oxidized directly. This is the reasons for some of my constructions with this reversed flow remote deep sand bed.

1. I have my refugium in the same apartment (macro algae produce oxygen during the light period - in my case night)
2. I have the refugium/sand bed directly after the DT and get the full flow over the sand bed (oxygen production from micro algae and zooxanthella and good movement of the water from streamers)
3. I have my skimmer directly after the refugium/sand bed (oxygen transfer from air to water through the skimmer)
4. I have an oxydator placed in the return apartment (oxygen additions from catalyzed hydrogen peroxide)

Hence - the risk for deadly hydrogen sulphide to my DT in normal operation - negligible

However - a power failure can be a risk. If I´m home - I can use both hydrogen peroxide direct to the water and to move my oxydators (I have one as reserv) to the DT and refugium.
If I am not home - the last frontier is that the return pump will not start before the skimmer has run for 5 minutes and be able to handle the hydrogen sulphide coming down from the refugium. When I´m away or prolonged periods - I place an oxydator in the refugium too (a small one)

DOC that will be added to my plenum directly affect my ORP level - an indication that DOC is a limited factor for my anaerobic bacteria - they directly rise their reduction rate nd ORP going down.

The reason why I chose 0 mV as target level for my plenum is that I expect that the ORP will go further down in the sand bed My pH level is around 7.9 in the plenum. pH in DT just now 8.3

Sincerely Lasse

But, I was paying attention. You mentioned 0mv in plenum. But hoping denutrification happening in substrate. That's assuming. And you know what assume means.

 

[Lasse]

I do not know where it is happen - if it is happen at the moment but if I stop dose NO3 - I get 0 in NO3.

I have no idea if 0 is the right ORP in the plenum - it is only a starting figure and if i 0 before the water reach the substrate - it will be lower in the middle of the substrate. I assume

Sincerely Lasse

 

[Mortie31]

I do not know where it is happen - if it is happen at the moment but if I stop dose NO3 - I get 0 in NO3.

I have no idea if 0 is the right ORP in the plenum - it is only a starting figure and if i 0 before the water reach the substrate - it will be lower in the middle of the substrate. I assume

Sincerely Lasse

Mine is currently -122mv in my reactor, not sure of an ideal level to run at, I’ve read between -250mv and - 50mv. If I reduce dose of NOPOx the redox will rise quite quickly.

 

[Lasse]

Somewhere between - 100 and - 200 probably works. Try to measure the outcoming water - it should be very low in NO2 (as near as zero as possible) If NO2 is 0 - then you can measure NO3 (NO2 in the sample make the NO3 reading to high !) NO3 should also be as close to 0 as possible in the outlet - however in the water column of the DT - I want to have around 4 ppm

Sincerely Lasse

 

[Mortie31]

Somewhere between - 100 and - 200 probably works. Try to measure the outcoming water - it should be very low in NO2 (as near as zero as possible) If NO2 is 0 - then you can measure NO3 (NO2 in the sample make the NO3 reading to high !) NO3 should also be as close to 0 as possible in the outlet - however in the water column of the DT - I want to have around 4 ppm

Sincerely Lasse

How can I measure NO2?

 

[Mortie31]

Sorry a senior moment... I’ll get my nitrite kit out lol

 

[Dr. Dendrostein]

Sorry a senior moment... I’ll get my nitrite kit out lol

Old timers disease. Heehee

 

[Dr. Dendrostein]

I do not know where it is happen - if it is happen at the moment but if I stop dose NO3 - I get 0 in NO3.

I have no idea if 0 is the right ORP in the plenum - it is only a starting figure and if i 0 before the water reach the substrate - it will be lower in the middle of the substrate. I assume

Sincerely Lasse

To much testing for me. Great info Lasse .

 

[Dr. Dendrostein]

I do not know where it is happen - if it is happen at the moment but if I stop dose NO3 - I get 0 in NO3.

I have no idea if 0 is the right ORP in the plenum - it is only a starting figure and if i 0 before the water reach the substrate - it will be lower in the middle of the substrate. I assume

Sincerely Lasse

I can see dosing keeps denitrification in check. That's new to me. I just understand that. The dosing control denitrification and corals like no3. Something new to me.

 

[Dr. Dendrostein]

Somewhere between - 100 and - 200 probably works. Try to measure the outcoming water - it should be very low in NO2 (as near as zero as possible) If NO2 is 0 - then you can measure NO3 (NO2 in the sample make the NO3 reading to high !) NO3 should also be as close to 0 as possible in the outlet - however in the water column of the DT - I want to have around 4 ppm

Sincerely Lasse

I know one thing @Lasse, when I finally build my dream tank, will be like yours but denitrator outside and very small. No sulfur denitrator. Thanks for info

 

[Mortie31]

Just had a thought, thinking of swapping my redox probe in the reactor for my oxygen probe, just to see how low the O2 sat is.. What do you think is it worth the hassle?

 

[Lasse]

Just had a thought, thinking of swapping my redox probe in the reactor for my oxygen probe, just to see how low the O2 sat is.. What do you think is it worth the hassle?

You can do that - but you will hav 0 mg/l

Sincerely Lasse

 

[Dr. Dendrostein]

You can do that - but you will hav 0 mg/l

Sincerely Lasse

Man Lasse, even i wouldn't know the answer to that. Id be stuck

 

[Lasse]

With -122 in ORP - there will be no oxygen

Sincerely Lasse