Why keeping the reactor anoxic?
Anoxic is a condition in which less 0.5ppm dissolved oxygen is present.
Anaerobic is a situation in which no free oxygen is used.
It has been shown T.denitrificans is able to transform nitrate into nitrogen using its anaerobic pathway, retrieving energy from the oxidation of sulfur compounds, also HS and elemental sulfur. T.d. is not able to use elemental sulfur using its aerobic pathway.
T.d. is able to change from an aerobic pathway to an anaerobic pathway in conditions where the biological oxygen demand ( BOD) is high and oxygen may be consumed faster as it can be delivered, in oxygen minimum zones ( OMZ). T.d. is a survivor, able to use both pathways. it has been shown T.d. switches to its anaerobic pathway still +- 3ppm DO being available, this when BOD is very high. T.d. is not able to compete for free oxygen against fast growing heterotrophs.
Anaerobic remineralisation, including heterotrophic denitrification, needs anoxic conditions, anaerobic respiration using nitrate and sulfur compounds does not, it can take place where free oxygen demand is high.
What happens in an anoxic reactor ?!
T.d is limited to its anaerobic pathway!
In a mainly anoxic ( <0.5ppmDO) sulfur denitrator, the anoxic condition is created due to the consumption of all oxygen ( +6ppm DO) present in the influent, aerobic remineralisation is limited due to the limited flow meaning little nitrate is produced in the reactor.
Most users of a sulfur denitrator target 0 nitrates in the effluent, this means all nitrate present in the influent is used up. What happens in an anoxic marine environment when no nitrate is available any more? Will T.d. survive? As there is only a very small oxygen minimum zone they are not able to move up and switch to its aerobic way of live. They are not able to compete with the heterotrophs for oxygen if enough organics are made available. if the condition persists, not many will survive producing organic waste.
Anaerobic remineralisation takes place using sulfate, producing not only HS but also a lot of ammonia , phosphate and CO2 will be produced.
OM + 59H2SO4 → 106CO2 + 16NH3 + H3PO4 + 59H2S + 62H2O. ref: MB Remineralisatie CMF De Haes 2019-2020
When nitrate becomes available in the anoxic zone and the presence of T.d. has been drastically limited, nitrate is used by heterotrophs for denitrification and DNRA, the production of ammonia.
Some denitrators are managed using an on/off flow regulator which transforms the denitrator into a batch reactor, not very suitable for BADES.
No nitrate in the effluent,? Who measures the presence off ammonia ?
High gas production in anoxic conditions means a high anaerobic remineralisation rate ( heterotrophic denitrification, DNRA and or sulfate reduction)! High ammonia production!
Using an anoxic reactor in combination with targeting 0 nitrates in the effluent, not a very good solution for trying to export safely stored nitrogen as nitrate entered may be transformed back to ammonia and nitrite.
Why export safely stored nitrate using a sulfur denitrator? The remedy used may become more problematic as the presence of nitrate ever may be.
For making good use of BADES no reactor is needed.
Anoxic is a condition in which less 0.5ppm dissolved oxygen is present.
Anaerobic is a situation in which no free oxygen is used.
It has been shown T.denitrificans is able to transform nitrate into nitrogen using its anaerobic pathway, retrieving energy from the oxidation of sulfur compounds, also HS and elemental sulfur. T.d. is not able to use elemental sulfur using its aerobic pathway.
T.d. is able to change from an aerobic pathway to an anaerobic pathway in conditions where the biological oxygen demand ( BOD) is high and oxygen may be consumed faster as it can be delivered, in oxygen minimum zones ( OMZ). T.d. is a survivor, able to use both pathways. it has been shown T.d. switches to its anaerobic pathway still +- 3ppm DO being available, this when BOD is very high. T.d. is not able to compete for free oxygen against fast growing heterotrophs.
Anaerobic remineralisation, including heterotrophic denitrification, needs anoxic conditions, anaerobic respiration using nitrate and sulfur compounds does not, it can take place where free oxygen demand is high.
What happens in an anoxic reactor ?!
T.d is limited to its anaerobic pathway!
In a mainly anoxic ( <0.5ppmDO) sulfur denitrator, the anoxic condition is created due to the consumption of all oxygen ( +6ppm DO) present in the influent, aerobic remineralisation is limited due to the limited flow meaning little nitrate is produced in the reactor.
Most users of a sulfur denitrator target 0 nitrates in the effluent, this means all nitrate present in the influent is used up. What happens in an anoxic marine environment when no nitrate is available any more? Will T.d. survive? As there is only a very small oxygen minimum zone they are not able to move up and switch to its aerobic way of live. They are not able to compete with the heterotrophs for oxygen if enough organics are made available. if the condition persists, not many will survive producing organic waste.
Anaerobic remineralisation takes place using sulfate, producing not only HS but also a lot of ammonia , phosphate and CO2 will be produced.
OM + 59H2SO4 → 106CO2 + 16NH3 + H3PO4 + 59H2S + 62H2O. ref: MB Remineralisatie CMF De Haes 2019-2020
When nitrate becomes available in the anoxic zone and the presence of T.d. has been drastically limited, nitrate is used by heterotrophs for denitrification and DNRA, the production of ammonia.
Some denitrators are managed using an on/off flow regulator which transforms the denitrator into a batch reactor, not very suitable for BADES.
No nitrate in the effluent,? Who measures the presence off ammonia ?
High gas production in anoxic conditions means a high anaerobic remineralisation rate ( heterotrophic denitrification, DNRA and or sulfate reduction)! High ammonia production!
Using an anoxic reactor in combination with targeting 0 nitrates in the effluent, not a very good solution for trying to export safely stored nitrogen as nitrate entered may be transformed back to ammonia and nitrite.
Why export safely stored nitrate using a sulfur denitrator? The remedy used may become more problematic as the presence of nitrate ever may be.
For making good use of BADES no reactor is needed.