Volatile fatty acids and ammonia recovery, simultaneously cathodic hydrogen production and increasing thermophilic dark fermentation of food waste efficiency

Abstract

A combined thermophilic anaerobic bioreactor of food waste and bioelectrodialysis system was used to recover volatile fatty acids and ammonia as renewable materials and also to remove the inhibitory effect of biohydrogen production byproducts. Different configurations of bioelectrodialysis system under various amounts of inlet food waste and external electrical currents were examined were investigated to find out the best conditions for system performance. When the two anion exchange membranes (AEM) were installed on the anode and cathode sides of separation chamber, 12 mL min-1 of mixed liquid was circulated between fermenter and separation chamber, while the external energy of 2.7 V and 0.2 M NaCl as electrolyte were used in the electrodialysis chambers. As long as the food waste with 70000 mg COD L-1 was used in the fermenter, the concertation of organic acids in the recovery chamber was the highest, 507.3 mg L-1 after 24th h. As a result, 0.63 L L-1 biohydrogen and 50 mL cathodic hydrogen were produced. When a cation exchange membrane was embedded on the cathode side of the separation chamber, the ammonia concertation in the recovery chamber was the highest, 518 mg L-1, at 36th h. At the same time, the chemical oxygen demand of the anode solution was decreased by about 3600 mg L-1. This sustainable and bioelectrical system can recover organic acids and ammonia, cathodic hydrogen production, while simultaneously increase biohydrogen production and efficient even when substrate concentration was higher.