Disinfection Guidelines for Satellite Water Recycling Facilities
Year Released: 2013
Funding Partners: Bureau of Reclamation, California State Water Resources Control Board
Total Investment: $653,660.64 (Cash: $350,000, In-Kind: $303,660.64)
Principal Investigator: Joseph G. Jacangelo, MWH Americas, Inc.
Water reuse regulations or guidelines are developed at the state level in the U.S. Where chlorine is used to disinfect recycled water for uses such as the irrigation of open access landscape irrigation sites, most states require tertiary-treated water. When satellite water recycling facilities are utilized for applications that require tertiary-treated recycled water, membrane bioreactors (MBRs) are often a preferred treatment process. However, a lack of data on real-world performance of MBR facilities has precluded the potential to lower CT (total chlorine residual times modal contact time) disinfection requirements imposed by California and some other states.
Goals and Objectives
The project develops disinfection guidelines for MBR effluents when free chlorine is used as the disinfectant. The study included data collection from 38 satellite facilities that use MBR processes, with intensive sampling at nine of those facilities and two MBR pilot systems.
This study was designed to accomplish the following objectives:
- Characterize satellite MBR effluent water qualities through a reconnaissance survey of a wide range of satellite facilities.
- Assess satellite MBR effluent water quality variability at selected satellite facilities.
- Assess worst-case scenarios on satellite MBR effluent water quality.
- Develop disinfection requirements for MBR effluents produced under routine and stressed operating conditions.
- Conduct monitoring of the nitrification process consistency at a full-scale MBR water recycling facility and identify potential causes for reduction in nitrification efficiency of the biological process.
Findings and Conclusions
Results from the study demonstrated the ability of the MBR process to produce oxidized, nitrified effluents that have very low concentrations of particles and pathogens. Microbial inactivation studies conducted on effluents from satellite MBR facilities and pilot MBR systems showed that a free available chlorine CT of 30 mg-min/L and turbidity of ≤ 1.0 were sufficient to achieve a 5-log removal of seeded male-specific bacteriophage and total coliform bacterial concentrations at or below 2.0 CFU/100 mL. In order to employ these low CT values at satellite facilities, implementing a process control strategy that will ensure production of high-quality effluent by the MBR process with respect to particles and ammonia is critical.