Estimation of nitrifying and heterotrophic bacterial activity in biofilm formed on RAS biofilter carriers by respirometry

Biofilm, the aggregates of microbial layers that are attached on surface biofilter carriers, plays a central role in removal and conversion nutrients recirculating aquaculture systems (RAS). The bacterial activity biofilm involves autotrophic heterotrophic processes. These biological processes crucial for water quality RAS but difficult to monitor. In this study, we demonstrate new method based intermittent respirometry selectively estimate following spike substrate concentration. was tested with three different carriers (extruded polypropylene, injection molded polypropylene polymeric foam) from moving bed reactors common freshwater RAS. Oxygen consumption rates biofilm-associated bacteria were measured closed metabolic chambers under standard conditions. protocol included sequential flushes either pure tap water, or spiked nitrite, ammonium acetate. results showed consistent carrier-specific activities endogenous respiration, nitrite-oxidizing (NOB), ammonia-oxidizing (AOB) (HB) biofilm. highest normalized volumetric oxygen rates, found foam values 677 ± 125, 764 156 166 36 g O2·m?3·d?1 NOB, AOB HB, respectively. performance evaluation respirometric data satisfactory accordance degradation batch kinetic tests all confirming feasibility robustness as means assessing performance. Our study provides an on-site tool leads better understanding dynamic relationship between biofiltration quality.