Activity monitoring for nitrifying bacteria by fluorescence in situ hybridization and respirometry

The activities of two families of nitrifying bacteria were measured by appl ied respirometer and fluorescence in situ hybridization (FISH) for the purp ose of monitoring nitrogen removal. Oxygen uptake rates (OUR) for Nitrosomo nas and Nitrobacter were separately measured with the dosing of selective i nhibitors during respirometric monitoring. The FISH method was applied to a nalyze microorganism communities. In 5 mg NH4+-N/L solution, the total nitr ogen oxygen demand (NOD) was found to be 6,672 mg DO/L-day with ammonia and nitrite oxidation rate of 4,512 and 2,160 mg DO/L-day, respectively. The o xygen consumption by endogenous oxidation was 288 mg DO/L-day and the biolo gical oxygen demand 936 mg DO/L-day. Respirometric measurements were well m atched by the FISH result, which described the presence and quantity of eac h nitrifying bacteria as nitrification proceeded. It was found that when co upled with OUR data, FISH could provide valuable information about the nitr ogen removal process in many practical wastewater treatment systems.