Pilot-scale evaluation of separate-stage nitrification using an attached-growth, moving-bed media process

Submerged attached-growth processes, both fixed and moving bed, are becoming more popular. These processes may or may not be used in combination with suspended-growth treatment. The objective of this project was to evaluate a tertiary attached-growth, moving-bed media nitrification system based on the ammonia-nitrogen removal rates and effluent concentrations that could be achieved. A pilot-scale system for nitrification of secondary municipal wastewater effluent was operated for 142 days. The minimum aeration requirements for media mixing provided sufficient dissolved oxygen. The generation of biological solids from nitrification was insignificant. Design effluent ammonia-nitrogen concentrations (<6 mg/L) were achieved at influent loading rates greater than design (1.18 g ammonia-nitrogen/[m2 x d]) coincident with detention times shorter than design conditions (4 hours). Empirical relationships for the ammonia-nitrogen removal rate and effluent concentration as a function of influent ammonia-nitrogen loading were developed. Detention time is believed to be an important parameter affecting these relationships.