Microfiltration of Primary Effluent for Clarification and Microbial Removal

Abstract

Microfiltration (MF) is gaining popularity as a process for providing clarification and a physical means of disinfection or microbial removal. This work presents the concept of using MF to directly treat primary wastewater effluent, and discusses results from pilot testing of MF for removal of suspended solids, bacteria, and other micro-organisms. In the wastewater industry, MF of primary effluent has applicability as a potential means of physically disinfecting wastewater for direct discharge without the use of conventional secondary treatment and chemical disinfection. In the water reuse industry, it can be applied as part of the reclamation process in a more efficiently integrated reclamation process. MF of the primary effluent was tested at a pilot scale for more than 1 year using a membrane system with 0.2- μ m membrane pore size and a pressure vessel configuration. The MF pilot demonstrated stable hydraulic operation with no or negligible evidence of long-term (irreversible) fouling. Excellent solids and bacterial removals were achieved, with total and fecal coliform removals averaging greater than 5 logs with maximum removals observed at 7 logs. Based on the pilot testing results, MF of primary effluent appears to be a promising option for both direct discharge of MF effluent to the ocean without chemical disinfection, or as a pretreatment to reverse osmosis for reclamation applications.