A bio-electrochemical reactor coupled with adsorber for the removal of nitrate and inhibitory pesticide

In this study, the treatment characteristics of nitrate and toxic pesticide by a combined bioelectrochemical reactor (BER)/adsorption process was investigated. Experimental results showed that the disappearance of NO₃^- in BER was in accordance with the applied current. NO₂^- was not detected in the effluent, but the production of N₂O was increased with increasing IPT loading. In the presence of IPT, up to 30% of the nitrate nitrogen consumed was converted to N₂O, while more than 95% converted to N₂ in the absence of IPT. In adsorption column, IPT was efficiently removed onto either granular activated carbon or silicone resin so as to meet the guideline value (40μg/l) and to reduce the N₂O accumulation. A simplified kinetic model that considers the sequential reduction of nitrate and inhibition of the N₂O reduction step by pesticide as well as Langmuir adsorption isotherm was developed and used to evaluate the process performance. Theoretically predicted effluent concentrations were in good agreement with the observed results for nitrate, nitrite, N₂O, N₂ and IPT. It was considered that high removal performance of nitrate and pesticide by the combined process is attributable to high affinity of adsorbates for IPT in comparison with relatively large inhibition constant (K_i).