“…Thirdly, we evaluated if H 2 O 2 decomposition rates could reflect the microbial activities in biofilm by testing different quantities of mature bioelements from the same biofilter. It is well-known that the rate of H 2 O 2 decomposition catalyzed by catalase is proportional to the catalase concentration, when the H 2 O 2 concentration is low [38,39]. However, measuring the catalase concentration excreted by biofilm can be difficult and impractical.…”