Defining Risk-Based Monitoring Frequencies to Verify the Performance of Water Treatment Barriers

Preventing failures of water treatment barriers can play
an important
role in meeting the increasing demand for microbiologically safe water.
The development and integration of failure prevention strategies into
quantitative microbial risk assessment (QMRA) offer opportunities
to support the design and operation of treatment trains. This study
presents existing failure models and extends them to guide the development
of risk-based operational monitoring strategies. For barriers with
rapid performance loss, results show that a failure of 15 s should
be reliably detected to verify a log reduction value (LRV) of 6.0;
thus, detecting and remediating these failures may be beyond current
technology. For chemical disinfection with a residual, failure durations
in order of minutes should be reliably detected to verify a LRV of
6.0. Short-term failures are buffered because the disinfectant residual
concentration sustains a partial reduction performance. Therefore,
increasing the contact time and hydraulic mixing reduces the impact
of failures. These findings demonstrate the importance of defining
precise frequencies to monitor barrier performances during operation.
Overall, this study highlights the utility of process-specific models
for developing failure prevention strategies for water safety management.