Competition in biofilms

Competitions in biofilms for substrate and space have been studied by using a microelectrode technique and a microslicing technique. Three different kinds of biofilms, cultured by laboratory-scale rotating drum biofilm reactors (RDBR) with synthetic wastewater, have been used as test materials. Oxygen, ammonium-nitrogen, nitrate-nitrogen, and pH concentration profiles in the biofilms were measured using microelectrodes. Experimental results showed that: 1) an increase of organic loading rate would result in a decrease of DO concentration in the biofilm. However, after the organic loading rate exceeded a certain value, the oxygen profiles within the biofilm did not change any more; 2) Heterotrophs competed for oxygen with nitrifiers, which resulted in the inhibition of nitrification because of the shortage of oxygen. Glucose itself, however, did not inhibit the nitrification processes; and 3) The competition for substrate in biofilms resulted in a stratified biofilm structure. Experi...