Removal of polar micropollutants from domestic wastewater using a methanogenic - aerobic Moving Bed Biofilm Reactor system

Abstract

A lab-scale system consisting of a methanogenic and an aerobic moving bed biofilm reactor (MBBR) was operated for seven months to investigate major pollutants' and polar organic micropollutants' removal from domestic wastewater under three different organic loading rates (OLRs). For all OLR values tested, the system achieved efficient COD (>84%) and NH4-N removal (>96%); both reactors contributed to the decrease of organic loading, while the aerobic bioreactor was exclusively responsible for the removal of ammonium nitrogen. The increase of OLR from 0.20 ± 0.10 to 2.10 ± 0.20 kg COD m-3 d-1 resulted to increase of the detected volatile fatty acids in the anaerobic reactor and increase of the produced biogas to 172.7 ± 25.3 mL L reactor-1 d-1. All target micropollutants were partially removed during different experimental phases; their removal ranged between 31% (5-methyl-1H-benzotriazole, 5TTR) and 97% (2-hydroxybenzothiazole, OH-BTH). Except benzotriazole (BTR) and OH-BTH, both reactors contributed significantly to the removal of target micropollutants, while the addition of extra aerobic MBBR as a final polishing step enhanced only OH-BTH removal. Use of experimental and literature data showed that the increase of organic loading enhanced the removal of three out of five target micropollutants, while the key factor responsible for this effect was COD concentration in influent wastewater. The modelling of micropollutants' removal efficiency using biodegradation kinetics calculated in batch experiments showed satisfactory correlation between predicted and measured values for most target compounds.