Challenges of municipal wastewater reclamation for irrigation by MBR and NF/RO: Physico-chemical and microbiological parameters, and emerging contaminants.

Climate change and the increased demand for food amplified the global problem with water supply for irrigation. This work deals with the reclamation of municipal wastewater (MWW) for irrigation by a membrane bioreactor (MBR), nanofiltration (NF), and reverse osmosis (RO). The emphasis was on the comparison of physico-chemical and microbiological parameters with the World Health Organization (WHO) and the European Union (EU) guidelines. In addition, the detection and removal of contaminants of emerging concern (CEC) from the Watch List (EU Decision 2015/495) were examined. Firstly, the MWW was monitored (physico-chemical and microbiological parameters, trace elements, and occurrence of CECs) for six months. Thereafter, the MWW was treated with MBR, NF, and RO. The reclaimed water satisfied the physico-chemical and microbiological quality requirements only after additional NF/RO treatment. Membrane bioreactor efficiently removed methiocarb (>99.9%), tri-allate (>99.9%), clothianidin (88.0%), and clarithromycin (71.9-74.2%), while the removal of azithromycin, acetamiprid, and oxadiazon was around 30%. The low and even negative removal during MBR treatment was observed for diclofenac (15%), clothianidin (-14%), imidacloprid (-18%), and diclofenac (-157%). Additional treatment of MBR effluent with NF90 and XLE membranes resulted in complete rejection of detected CECs, while NF270 membrane achieved results between 75% and 91%.