Electric Power Consumption and Current Efficiency of Electrochemical and Electrobiological Rotating Disk Contactors Removing Nutrients from Wastewater Generated in Soil-Less Plant Cultivation Systems

The study was conducted in a one-stage rotating electrobiological disk contactor (REBDC) and a rotating electrochemical disk contactor (RECDC). Synthetic wastewater with characteristics similar to the wastewater from soil-less cultivation of tomatoes was used in the experiment. Current efficiency (CE) values, that express the denitrification performance of bio- and electrochemical reactors, were higher in the electrobiological contactor than in the electrochemical one. Combining biological processes with electrochemical processes in the electrobiological contactor resulted in almost 20% higher current efficiency in the contactor operated at a density of 0.63 A/m2 and hydraulic retention time (HRT) = 4 h. The study showed that, in both the electrochemical and the electrobiological contactor, current density increase and hydraulic retention time extension increased electric power consumption (E) during phosphorus compounds removal and simultaneously lowered current efficiency.