Ozone Pretreatment of a Non-Nitrifed Secondary Effluent Before Microfiltration
Year Released: 2014
Funding Partners: Bureau of Reclamation, West Basin Municipal Water District
Total Investment: $354,048.34 (Cash: $199,914.34, In-Kind: $154,134)
Principal Investigators: Marc Serna, West Basin Municipal Water District, R. Shane Trussell, Trussell Technologies, Inc., and Fredrick W. Gerringer, Trussell Technologies, Inc.
Wastewater effluent organic matter (EfOM) is the primary factor limiting microfiltration (MF) performance when treating secondary wastewater effluent at water reuse treatment plants. Fouling by EfOM can lower membrane flux, increase chemical cleaning frequencies and cause irreversible fouling that reduces membrane longevity and treatment efficiency. Optimizing biological oxidation during secondary wastewater treatment could reduce MF fouling, but this approach is not always feasible. In those situations, chemical oxidation using ozone could be an effective alternative.
Goals and Objectives
The project was designed to optimize the operation of PVDF MF membranes after ozonation of wastewater effluent and evaluated the impacts of ozonation on other aspects of IPR treatments and the performance of reverse osmosis (RO) membranes that treat MF filtrate.
This project used pilot-scale equipment to optimize ozone pretreatment of MF, compare MF performance after coagulation pretreatment and ozone pretreatment, and evaluate the impact of ozone pretreatment on other aspects of a water reuse treatment train, such as RO performance and disinfection byproduct concentrations. Two parallel treatment trains of MF and RO were operated with three possible pretreatment strategies: (1) ozone, (2) coagulation, and (3) ozone plus coagulation. MF, RO and water quality data were compared between these treatment trains to evaluate to effect of preozonation and the other pretreatment approaches.
Findings and Conclusions
- Preozonation improved microfiltration (MF) feed and backwash water quality.
- Preozonation had a beneficial effect on MF performance.
- Mitigation measures, such as ozone dose control using ultraviolet transmittance at 254 nm or ferric chloride coagulation, were needed to prevent inorganic fouling by manganese after ozone oxidation.
- The concentration of n-nitrosodimethylamine increased significantly after ozonation.
- Preozonation reduced the concentration of many contaminants of emerging concern.
- There were no negative effects of preozonation on reverse osmosis membrane performance.