Efficacy of bioelectrochemical and electrochemical systems in ammonia recovery from slaughterhouse wastewater

Ammonia presence in water has many negative impacts including eutrophication. So, the major objective of this research was to evaluate the efficiency of microbial fuel cell (MFC) and electrochemical (ECS) systems for their removal and/or recovery from wastewater at different levels of ammonia (500 ppm, 1000 ppm, and 1500 ppm). Additionally, a novel approach was tested by using nanomaterial prepared from pomegranate peel as a coating material for the electrodes as it is abundant in many countries. Two systems were tested: Group (A) with a non-coated graphite plate anode (MFC1 and ECS1) and Group (B) which was coated with nano-graphene oxide made from pomegranate peels (MFC2 and ECS2). Results revealed that MFC1 gave the best ammonia removal efficiency reaching 96.2% when the initial concentration was 500 ppm after 13 days, and MFC2 gave maximum removal efficiency of 94.4% and 99.4% for 1000 and 1500 ppm after 19 and 25 days, respectively. COD results coincided with the removal efficiency. Electrochemical ammonia removal was carried out using two external electrical currents, 40 and 80 mA. Results showed that ECS2 gave the highest ammonia removal efficiency of 95.08% at 80 mA in case of 500 ppm, and the maximum for recovery was 80% when 1000 ppm was tested at 80 mA along with an increase in pH in the cathode chamber. Furthermore, ECS2 consumed less energy than ECS1 for ammonia recovery. ECS2 efficiently treated slaughterhouse wastewater reaching almost 100% ammonia removal; however, the maximum recovery of 44.7% occurred after 6 h, but consuming less energy than ECS1. It was evidenced that using an anode coated with nanographene oxide provided dual benefits of quickness and effective ammonia removal and/or recovery and provisioning energy requirements.