Membrane Bioreactor Pathogen Reduction For Potable Water Reuse

Membrane Bioreactors (MBRs) are an intensified process for wastewater (WW) treatment, relative to conventional activated sludge. Due to the immersion of micro or ultra filtration membranes into a biological process MBRs produce a consistent high quality filtrate. The hybridization of bioreactor and membrane separation means a MBR removes pathogens by a combination of mechanisms including size exclusion, enhanced rejection due to fouling layer development, biological degradation and adsorption to sludge flocs and wasting. The combination of mechanisms results in robust pathogen reduction by MBR. Colorado (CO) published direct potable reuse (DPR) regulations which define pathogen reduction requirements at default levels of 12 enteric virus and 10 Giardia and Cryptosporidium from the treated WW or an approach where the treated WW may be characterized to set alternative log reduction targets. This presentation will 1) define the mechanisms of and typical levels of pathogen reduction by MBRs, 2) provide an overview of the procedure via existing case studies for treated wastewater characterization to set alternative project specific DPR LRTs in CO and 3) define a pathway for how the alternate pathway could be followed when implementing DPR in CO downstream of a MBR.