Membrane Bioreactors for On-site Wastewater Treatment and Recycling at The Visionaire, NYC

This study considered ways to optimize the integration of an in-building Water Treatment and Reuse System (WTRS) to maximize opportunities for potable water conservation while minimizing associated system costs and carbon footprint. The studied WTRS is installed at The Visionaire, a Platinum LEED certified residential tower block in Battery Park, New York City that has approximately 900 residents. The WTRS is designed to treat 95,000 liters per day and incorporates a Membrane Biological Reactor (MBR) with subsequent disinfection and roof-water capture. Reclaimed water is used for toilet flushing, cooling tower make-up and irrigation. From May 2010 to March 2011, the WRTS saved 8 mega liters of potable water and reduced water utility bills at The Visionaire by over 25,000. Per capita potable consumption at The Visionaire was reduced by 27% in comparison to a conventional building. Operation of the WTRS required that pH was kept below 7.0 to discourage calcium phosphate precipitation in the cooling tower condenser. To maximize water reuse in the cooling tower it was required to halt the continuous hypochlorite disinfection strategy so that conductivity in the cooling tower was kept within limits. Power usage at this scale was approximately 380 kWh/day, of which approximately 50% was consumed by the MBR blowers. Beyond reducing potable water consumption, it is recommended that similar systems be installed to serve entire blocks rather than single buildings, or to achieve a reuse footprint of 380,000 liters per day, so that these systems become competitive with conventional supply and treatment from a carbon footprint and operational cost standpoint.