Is the LRV Calculation Applicable in Water Reclamation?

The EPA developed the Membrane Filtration Guidance Manual (MFGM) as a tool to use in conjunction with the new Long Term 2 Enhanced Surface Water Treatment Rule (LT2) drinking water requirements which requires additional cryptosporidium removal. The MFGM recommends using the Log Removal Value (LRV) calculation to measure membrane integrity in terms of actual particle removal. Historically membrane applications in wastewater do not measure log removal of particles because they rely on disinfection to reduce bacteria counts. Clark County Water Reclamation District (District) in Las Vegas has implemented a 3 LRV requirement as part of the membrane procurement for their tertiary facilities and has evaluated it in pilot testing. The District has decided to implement direct integrity monitoring as part of their goal to produce effluent close to drinking water standards. The objective of this paper is to convey the bacteria removal results from a tertiary membrane application and show the comparison to the LRV calculation.