My understanding of this process which I am not sure is correct at all is that the sulpher needs to be in fed oxygen rich flow and "regulated" to keep sulpher bacteria from consuming itself without food(no3) . I am using something similar to what
@Belgian Anthias describes to slow feed/ faster feed water flow to keep No3 at ok level ( I am @ 2ppm today) after starting approx 2 months ago . Taking baby steps lol.started above 30 ppm .
BADES columns are remineralization filters. They have a high BOD ( biological oxygen demand) depending on the DOC production and TOC supply. Such a filter breaks down organic matter and removes DOC, it keeps DOC low which is a lot more important than the presence of a nitrate reserve. Nitrate is produced. Due to the BOD demand on and in the outer layers of the biofilm or BADES rolls oxygen minimum zones are created on the inside and some anoxic zones on the surface, on the substrate. Produced nitrate can be removed by denitrification, autotrophic and heterotrophic.
The sulfur bacteria can not consume themselves without food, they are autotrophs. They are able to use up their stored nutrient reserves to survive a prolonged period of time, without growing. They do not form cysts. Dead bacteria will be "consumed", remineralized, by heterotrophs, producing HS if done by anaerobic remineralization. ( no nitrate is produced in anoxic zones but ammonia, sulfate is used as an oxygen source) In a normal biofilm produced HS will be oxidized, if not anaerobically reducing nitrate, it will be done aerobically and it can be done by the same sulfur bacteria. Both processes produce sulfate. From sulfate back to sulfate.
BADES columns do not depend on nitrate present in the water column but it is advised to keep on a minimal detectable nitrate reserve. This makes it possible to follow up the nitrogen availability and prevents too much nitrogen may be exported.
One must keep in mind only nitrogen is removed, all the rest is left behind and may not be reusable due to nitrogen limitation. Removing safely stored nitrogen does not solve a thing as nothing is done to correct the source of the nitrogen reserve. Why a usable nitrogen reserve can build up in a well-lit aquarium?
It is not the sulfur needing good flow, it is the remineralization capacity of the filter. Remineralization removes organic waste and removes produced ammonia by transforming the ammonia to nitrate, used by the sulfur bacteria.
By managing the flow one is able to manage the oxygen supply. Using a refuge one is able to manage the nitrate level as desired by the user.
BADES Columns should be placed hanging free in the water, water may not be forced true the filter.
There are a lot of different sulfur bacteria but there are only a few who are specialized in using nitrate to oxidize sulfur. In BADES filters mainly T. denitrificans are responsible for oxidizing sulfur using nitrate. They do not depend on the presence of organic waste or food to prosper. They have the ability to use both pathways to retrieve oxygen and are able to function aerobically and anaerobically. They can switch over from oxygen to nitrate. They do NOT need NITRATE to survive as long there is a sulfur source they can use.
Their food is sulfur, not nitrate!! They are very active in oxygen transition zones, they do not need an anoxic environment, the moment not enough oxygen can be supplied to fulfill the demand they switch over to nitrate.
Only when using nitrate they are able to oxidize elemental sulfur. In an environment where growth is exponential, the biological oxygen demand ( BOD) can double at any moment.
T. denitrificans will NOT die off if no nitrate is available but growth will be limited. T.denitrificans will try to be as close as possible to the source of sulfur production. In an aerobic remineralization filter, this will be mainly close to the substrate where anoxic zones are created, making anaerobic remineralization possible and Sulfur compounds as HS are produced.
What we do is adding elemental sulfur to a remineralization filter to ensure sulfur is not the growth limiting factor for denitrification and limit the need for HS production, anaerobic remineralization, and anoxic zones. We do NOT try to prevent sulfate reduction as it is a normal and essential process in a nitrifying biofilm. The denitrification capacity of a normal remineralization filter can this way be increased to the level of nitrate production.
In a denitrator kept in an anoxic state, a lot more HS is produced as nitrate is not produced in the filter. Present and produced TOC and DOC is remineralized anaerobically., a lot of HS may end up in the water. Only nitrate present in the water column will prevent sulfate reduction, targeting 0 nitrates in the effluent is not a good idea.
In a sulfur denitrator kept in an anoxic state, the same may happen, but as the sulfur bacteria are not able to switch over to oxygen they will die off when nitrate is used up. HS will not be removed.
A BADES system is NOT kept in an anoxic state,!
BADES columns or rolls are very effective for exporting nitrogen, too much nitrogen may be exported. Nitrogen is part of the building materials left over after the complete remineralization of organic matter. If too much nitrogen is removed the balance between nitrogen availability and the presence of all other essential building materials may be lost. For example, the phosphate reserve may increase because there is not enough nitrogen to make good use of it.
