Use of Advanced Three-Stage Membrane System for Turning Extreme Wastewater Into Boiler Feed Water

An engine manufacturer enacted a number of sustainability goals, one of which was 90% wastewater reuse. One facility in the northeast United States implemented a ceramic ultrafiltration system in 2019 to reduce labor intensity, free up footprint, and improve life cycle costs versus a polymeric ultrafiltration system. The ceramic ultrafiltration system reduced oil and grease and suspended solids by over 99% to prepare the permeate for biological treatment and achieved over 90% recovery. Subsequently, the site started up a new ceramic membrane-based membrane bioreactor in place of its activated sludge plant, the effluent of which was causing the plant to incur quality surcharges. The membrane bioreactor produced effluent of suitable quality to allow recycle of wastewater via reverse osmosis. The client decided on a spacer tube reverse osmosis system as it was proven in challenging applications and offered more reliability for treating effluent with high concentrations of organics. The reverse osmosis system was started up early in 2020. The permeate is used to displace city water for use as boiler feed water and cooling tower make-up. The permeate passes through a mixed bed ion exchange resin to polish out dissolved solids prior to being pumped to the boilers. The reverse osmosis system has delivered significant savings in resin regeneration chemical costs. The combined system has been operational for over 1.5 years, with the ultrafiltration system being operational for over 2.5 years and the membrane bioreactor over 2 years. This paper will share design experience and lessons learned from this project.