Water Research Foundation (WRF) project 4997 has proposed a framework for Tier 2 validation of membrane bioreactors (MBRs) which outlines how proponents could demonstrate that their MBR systems achieve log reduction values (LRVs) exceeding Tier 1 values of 1.0 and 2.5 for protozoa and virus, respectively. To date, no Tier 2 validation studies have been completed per the WRF 4997 Tier 2 recommendations. When proposing LRVs for Tier 2 validation, challenge testing of target pathogens and indicators is conducted and use of a 5th percentile LRV is recommended for selection as the performance benchmark. MBR validation studies frequently suffer from censored data, where pathogens may be above a reporting limit or below a detection limit. There are a number of methods to deal with censored data in MBR validation. In this work, various calculation methods are applied to a set of validation data from a unique, 10-year-old, MBR installation. The benefits and drawbacks of each calculation method are shown. In addition, benchmark LRVs are proposed that account for the impacts of ageing of membranes due to prolonged operation. It was possible to demonstrate that the Kubota membrane system studied, can achieve LRVs of greater than 3.0 for Cryptosporidium, 4.0 for Giardia and 2.5 for enteroviruses, in its lifetime. The removal of pathogens was also compared against surrogate indicator microorganisms. This paper will be of interest to membrane suppliers and utilities considering undertaking Tier 2 validation to enhance potential LRV credits possible with MBR systems.
This presentation is available to AMTA Members only.
Speaker
- Larry Morris
Company
- Kubota Membrane USA
Event
- AMTA/AWWA Membrane Technology Conference, West Palm Beach, FL
Session
- AMTA/AWWA Membrane Technology Conference
Date
- 07/20/21
Media
Keywords
- Membrane Bioreactors, MBR Validation, Log Reduction Values
Reference
- 9710-DP2638