Exploring Bioelectrochemical Systems for Removal and Recovery of Hexavalent Chromium or Nutrients

Bioelectrochemical systems (BES) is a platform technology that is able to realize versatile engineering functions and recover valuable resources in an energy-efficient manner. One of the potential applications of BES is to remove and recover nutrients simultaneously from nutrient-rich wastewater, such as digested manure from livestock. A four-chamber BES was developed and used in this study to explore the potential to remove and recover hexavalent Chromium from synthetic wastewater, and ammonia and phosphate from digested manure. The BES was able to achieve 99.6% removal of Chromium by membrane adsorption in 5 days but failed to recover in the concentration chamber. Nutrients were removed from the waste stream and recovered in the recirculated catholyte by the electrical field generated from the waste. The BES was demonstrated to achieve substantial COD removal, nutrients removal and recovery. On average, the removal efficiencies were about 50% for COD, 85% for NH4-N and 40% for PO4-P, and the concentration of NH4-N recovered in the catholyte was 670 mg/L after 5 cycles under an applied voltage of 0.8 V. PO4-P was not recovered in solution, probably because it has precipitated under the alkaline condition together with Mg and Ca concentrated in the catholyte. It was also demonstrated that nutrients removal and recovery depended on the current generation and were mostly completed at high current.