(185e) Ozonation of a Non-Nitrified Secondary Effluent to Reduce Microfiltration Fouling

Microfiltration (MF) is a common unit process for treating municipal wastewater effluent for indirect potable reuse.  However, effluent organic matter (EfOM) can foul MF membranes thereby reducing flux, increasing cleaning frequencies, and shortening membrane longevity.  Research has shown high molecular weight (MW) organics are the primary source of MF fouling, and ozonation is known to preferentially oxidize large MW organics.  However, this application of ozone is uncommon and there are few references discussing it in the scientific literature.  Therefore, pilot testing was performed to evaluate the feasibility of oxidizing EfOM with ozone to restore MF performance while treating non-nitrified secondary effluent with poor water quality.  Two parallel MF treatment trains, one with ozone pretreatment (O₃-MF) and the other without it, were used to compare the benefits of EfOM oxidation with ozone.  The MF unit without ozone pretreatment operated at 19.3 gfd for < 3 days before it shutdown from high transmembrane pressure, but the MF unit with ozone pretreatment (6 mg/L transferred dose) operated at 20 gfd for 21 days.  These results demonstrated ozonation of EfOM extended the interval between MF cleanings by seven-fold, indicating this MF pretreatment strategy could provide significant benefits if implemented at full-scale.