Membrane and Desalination Technologies - TCE Moodle Website

140 N.K. Shammas and L.K. Wang
excursion occurs, a system must conduct a significant excursion evaluation and discuss the
evaluation with the state prior to the next sanitary survey.
3.3. Requirements for Membrane Filtration under the LT2ESWTR
In order to receive removal credit for Cryptosporidium removal under the LT2ESWTR,
a membrane filtration system must meet the following three criteria:
1. The process must comply with the definition of membrane filtration as stipulated by the rule.
2. The of a membrane filtration process must be established through a product-specific challenge test
and direct integrity testing.
3. The membrane filtration system must undergo periodic direct integrity testing and during
operation.
The rule does not prescribe a specific removal credit for membrane filtration processes.
Instead, removal credit is based on system performance as determined by challenge testing
and verified by the direct integrity testing. Thus, the maximum removal credit that a
membrane filtration process may receive is the lower value of either of the following:
1. The removal efficiency demonstrated during challenge testing.
2. The maximum log removal value (LRV) that can be verified by the direct integrity test used to
monitor the membrane filtration process.
Based on this framework, a membrane filtration process could potentially meet the Bin 4
Cryptosporidium treatment requirements, as shown in Table 4.1. Additionally, if a membrane
filtration system has been previously approved for 5.5 log Cryptosporidium removal by the
state, the utility would not be required to conduct source monitoring under the LT2ESWTR.
These primary elements of the regulatory requirements for membrane filtration under the
LT2ESWTR, including the definition of membrane filtration, as well as challenge testing,
direct integrity testing, and continuous indirect integrity monitoring, are summarized in the
following subsections.
3.3.1. Definition of a Membrane Filtration Process
For the purposes of compliance with the LT2ESWTR, membrane filtration is defined as a
pressure- or vacuum-driven separation process in which particulate matter larger than 1 mmis
rejected by a nonfibrous engineered barrier, primarily through a size exclusion mechanism
and which has a measurable removal efficiency of a target organism that can be verified
through the application of a direct integrity test. This definition is intended to include the
common membrane technology classifications: MF, UF, NF, and RO. In addition, any
cartridge filtration device that meets the definition of membrane filtration and that can be
subject to direct integrity testing in accordance with rule requirements would also be eligible
for Cryptosporidium removal credit as a membrane filtration process under the LT2ESWTR.
In the guidance manual (3), such processes are called membrane cartridge filtration (MCF).
Filtration processes that are reliant on mechanisms such as adhesion to filter media or
accumulation of a fouling layer to remove particulate matter are excluded from the definition