Modeling and design of anaerobic fluidized bed reactor with recycling for denitrification of reverse osmosis concentrates

• High nitrate removals from brine concentrates observed in anaerobic fluidized bed reactor.
• Modeling work presents AFBR process dynamics in transient and steady states.
• Model predictions and AFBR experimental data are in good agreement for nitrate removals.
• Model simulations present sensitivity of dynamics to process variables and process upscaling.

Reverse osmosis is a widely used technology in wastewater treatment, water purification, water reclamation and reuse. A major concern is production of brine concentrates containing high levels of ammonia or nitrogen. This work addresses biological denitrification of brine concentrates in anaerobic fluidized bed reactor (AFBR) systems. Previous publications (Ersever et al., 2007a and Ersever et al., 2007b) described the first phase: process development, feasibility evaluation, and reaction optimization. This paper describes the second phase involving process modeling for performance prediction, simulation, and design with upscaling implications. Laboratory-scale studies provided data for AFBR process evaluation and model verification under different conditions, including media characteristics, hydraulic residence times, and influent nitrate levels. Model simulations facilitated process design and upscaling, and further projected that among different parameters the Monod yield coefficient and maximum specific growth rate significantly influenced process dynamics. Transient-state dynamics provided insight into process induction and acclimation besides process recovery after upsets.