Enhanced Ammonia Nitrogen Removal and Recovery Through Intermembrane Distance and Stack Length Optimization in Bipolar Membrane Electrodialysis Systems

Abstract

The removal of ammonia nitrogen from wastewater are crucial due to its role in environmental pollution and eutrophication. Traditional methods often have high operational costs and energy inefficiencies, necessitating the development of sustainable alternatives. This study introduces an innovative approach for optimizing the intermembrane distance and stack length in bipolar membrane electrodialysis (BMED) systems, which is a relatively underexplored area in current research. By systematically varying intermembrane distances (190, 360, 610, and 1000 µm) and stack lengths (10, 20, 30, and 40 cm) under different current densities (20–80 mA/cm2), we demonstrated that while increasing intermembrane distance and stack lengths improves ammonia nitrogen removal and recovery rates, it also raises specific energy consumption (SEC). The removal and recovery rates reached nearly 100% at an intermembrane distance of 1000 µm across all current densities tested. The lowest observed SEC was approximately 9.11 kWh/kg-N at an intermembrane distance of 190 μm under a current density of 20 mA/cm2. The identified optimal configuration, combining an intermembrane distance of 360–610 µm with a stack length of 20–30 cm, achieved a balance between high recovery rates and low energy consumption. These findings provide valuable insights into the design and optimization of BMED systems, contributing to more efficient and sustainable ammonia management in wastewater treatment.

Keywords: Ammonia removal and recovery, Specific energy consumption, Intermembrane distance, Stack length, Bipolar membrane electrodialysis