Therefore, the NH3eN removal efficiencies of all three substrates systems are relatively
better. When the system HRT is greater than 4 days, the NH3eN removal efficiencies of all four substrate systems become stable.
When HRT reaches 6 days, the average NH3eN concentration indices in the final effluents are 2.9 mg/L, 6.3 mg/L, 3.6 mg/L and 4.7 mg/L respectively.