Ammonium removal from synthetic wastewater promoted by current generation and water flux in an osmotic microbial fuel cell

Abstract

Recovering useful resources from wastes represents a new approach of clean production with significant environmental and economic benefits. Ammonium nitrogen, which is an important inorganic contaminant and also a resource for fertilizer, can be removed and recovered from wastewater. As the first step of recovery, ammonium removal was successfully demonstrated in this study by using an innovative treatment system - osmotic microbial fuel cell (OsMFC). This OsMFC achieved the removal efficiency of 80.1 ± 2.0% with an anolyte flow rate of 0.4 mL min−1. Current generation was a key driving force for ammonium ion movement and increasing current generation from 0 to 1.8 ± 0.1 A m−2 could greatly enhance the removal efficiency from 40.7 ± 2.4% to 85.3 ± 3.5%. When current generation was similar, water flux could contribute significantly to facilitating ammonium removal, and as a result the OsMFC exhibited 55.2 ± 6.5% higher ammonium removal with water flux of 1.3 ± 0.2 LMH than that without water flux. In addition, ion diffusion and ion exchange contributed to 17.3 ± 2.4% and 2.8 ± 0.1% of ammonium removal, respectively, with 35 g L−1 NaCl as a catholyte. The key challenges such as the exact mechanism of ammonium transport, disposal of ammonium residue after recovery, effects of draw solutes, and system scaling up have been identified and discussed. The results of this study will help to develop an efficient approach for NEW recovery (NEW: nutrient, energy and water) from wastewater.