I dose ethanol below my deep sand bed and I totally control my NO3 concentrations that way but the PO4 - nada
The major control of my NO3 is not done by bacteria growth - its done by bacteria that use NO3 as an electron acceptor in oxygen free environment - ethanol is the electron donor in the same process - neither act as building blocks in this process.
However the whole process start with that ethanol act as an organic carbon source for heterotrophic bacteria in such a high grade that they consume all oxygen - In this process some organic carbon, NO3 and PO4 will be transformed into biomass - but not so much. When oxygen is limited or absent - some heterotrophic bacteria swing over and use NO3 instead for oxygen in the metabolism - hence convert NO3 into N2 gas (with help of some other steps but N2 is the final waste) This is the major part of NO3 reducing in my reversed flow DSB
I have always been sceptic to the claim that heterotrophic bacteria is able to take up so much dissolved PO4 and NO3 that it makes a difference.
On the contrary - if DOC is available, the bacteria will be able to eat more solid organic matter - and thus release both NH3/NH4 and PO4 from their organic origin (proteins and phosphorus organic compounds) in the solid organic matter
Sincerely Lasse
