Submerged or Sidestream: Best Forward Osmosis Configuration For an Osmotic Membrane Bioreactor

A pilot-scale osmotic membrane bioreactor (OMBR) was developed with a forward osmosis (FO) membrane submerged in a bioreactor and a Membrane Distillation re-concentration step driven by waste heat for potable wastewater reuse applications at military forward operating bases. Biofilm thickness, which is influenced by the forward osmosis (FO) membrane configuration, is a key parameter of reverse salt transport and elevated bioreactor salinity inhibits carbon and nutrient removal. Reverse salt flux (RSF) from two bench-scale forward osmosis membrane configurations were evaluated; the first is a membrane cassette submerged in the bioreactor and the second is a sidestream process external to the bioreactor. The water flux and RSF of the bench-scale systems were used to model pilot-scale bioreactor salinity and the effects of changing the solids retention, reactor volume, and draw solution concentration were examined.