Extending Tertiary Treated Municipal Wastewater as Boiler Feed-Water via a Dual Membrane CUF/RO Process

Abstract

The objective of this work is to conduct feasibility studies on water treatment for boiler feeding water use from treated municipal wastewater effluent using a pilot dual continuous ultrafiltration - reverse osmosis (CUF/RO) membrane process with the capacity of 15m3/h. A CUF membrane from HYDRAcap and LFC3-LD RO membrane were used in this study. The CUF unit and RO unit were operated at over 97% and 75-80% water recovery, respectively. The results indicate that CUF process is not only capable of reducing organic and nutrient pollutants but also achieves a silt density index (SDI) less than 2, turbidity of less than 0.47NTU which is suitable for RO treatment. Rejection of the RO unit in terms of average conductivity, COD, hardness, alkaline, NH4+-N, TN, TP were higher than 98.2%, 97.9%, 99.8%, 97.9%, 93.9%, 95.1% and 75%, respectively. Other parameters also can match the quality of high-grade water for use in the boiler industry except pH. Finally, a cost comparison between dual membrane and ion-exchange process showed annual savings of more than 33000000 CNY can be possible.