The influence of electric current density on specific denitrification rate of and nitrogen removal rate in electrochemical and electrobiological rotating contactor

This study aimed to determine the infl uence of the electric current density on the rate of nitrogen compounds removal (r N ) and the specifi c rate of denitrifi cation (r D ) in a rotating electrochemical disk contractor (RECDC) and a rotating electro-biological disk contactor (REBDC).In REBDC and RECDC, the cathode consisted of disks with immobilized biomass and disk, from which biofi lm was periodically removed, respectively.An aluminum anode was mounted in contactor chambers.The study was conducted using synthetic wastewater with characteristics similar to wastewater from soilless cultivation of tomatoes.The fi rst stage of the study determined r N and r D in the RECDC.The second stage determined r N and r D in the REBDC.Four hydraulic retention times (HRT) were tested: 4 h, 8 h, 12 h, and 24 h, with electric current densities of 0.63 A/m 2 , 1.25 A/m 2 , 2.50 A/m 2 , 5.00 A/m 2 , and 10.00 A/m 2 .In RECDC, a linear dependency was observed between r N and current density in the examined HRTs, whereas in REBDC, a logarithmic dependency was confi rmed between r N and current density.In both contactors, an exponential dependency was observed between r D and current density.The specifi c rate of denitrifi cation decreased when the current density and HRT were increased.The study showed that, in both contactors, the rate of total nitrogen removal increased when the current density was increased and the HRT was decreased.