Treatment of phenolic wastewater by combined UF and NF/RO processes

• Industrial wastewater was treated by combined UF and NF/RO processes.
• The permeate water from UF system was qualified to be used as the NF or RO feed water.
• The hydraulic resistances of NF/RO membranes under different TMPs were determined.
• The RO98pHt reached rejections of 95.5% and 94.9% for COD and phenol, respectively.

The potential of using the integrated membrane systems based on ultrafiltration (UF) coupled with nanofiltration (NF) or reverse osmosis (RO) for the treatment of phenolic wastewater from a paper mill was investigated. Polyethersulfone based membranes PES7000 (MWCO 7000), GR82PP (MWCO 5000), GR95PP (MWCO 2000), and SynderXT (MWCO 1000) were used for the UF treatment, and SynderXT exhibited the best results with the rejections of chemical oxygen demand (COD) and total dissolved solid (TDS) being 56.4% and 9.6%, respectively. The resulting UF permeate was further treated by NF membranes (NF99HF, NF97) or RO membrane (RO98pHt) to further remove the remaining pollutants (COD and phenol). The results showed that RO98pHt, which exhibited superior performance over NF membranes, reached rejections of 95.5% and 94.9% for COD and phenol, respectively.