Thanks.I think you're correct. A good analogy would be with rubble and gravel, materials that we generally believe to be inferior to finer grained materials (i.e. sand/mud) for supporting an anoxic zone. It seems that chunkier materials actually provide excellent microhabitat for anaerobes (at least within the core), even when water flow around the particle is relatively strong. Maybe they even like the flow around the exterior of the particle, as it efficiently carries away wastes and delivers more nutrients. This study suggests that's at least true for denitrifying bacteria in general (including PNS bacteria): https://pdfs.semanticscholar.org/3c...10.1320731497.1612138666-583202434.1612138666 It's a long paper, but at least check out the sections on denitrification.
My PhD advisor was cited in that paper. It took me back to sediment biogeochem seminars of years past.
Interesting that nitrate reduction had such higher rates than denitrification. For nutrient removal, assimilatory NO3 reduction will put out N if the microbes are skimmed or filtered out. But if there’s ammonia generation from NO3, then we‘re not removing nutrients.
I have an email in to my hydrogeologist colleague in my dept who‘s a “fluid flow in porous media” expert. Trying to get his sense if flow around a porous object could effect dissolved fluxes into the object. If fluxes would be higher in higher flow, then I’d worry O2 supply would be too fast to allow an anaerobic process inside the ceramic.