Bioreactor Experiment Initial Microorganisms Source Operating Conditions Period (days) NH4-N (mg/L) NO3-N (mg/L) Air Supply (mL/min) H2 Supply (mL/min) NH4-N bioreactor I Activated sludge from  drinking water system 30 - - - 60 II On-site groundwater 30 - - - 300 NO3-N bioreactor III Activated sludge from  drinking water system - 30 - 70 30 IV On-site groundwater - 30 - 70 30

Table 1: Summary of the operating conditions used in the experimental studies.