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Membrane Systems Planning and Design 343
After cleaning, a direct integrity test should be conducted before the pilot unit is returned to
service. If the membrane is integral and an acceptable flux has been restored, then the
cleaning is deemed successful. If not, alternate cleaning strategies should be considered. A
flow chart outlining a general pilot study sequence of events is shown in Fig. 8.2, illustrating a
typical series of test runs and subsequent chemical cleaning events.
2.3. Testing and Monitoring
A thorough and carefully developed testing and monitoring plan is a critical component of
a pilot test program, as this is the means by which system performance is assessed. There are
several categories of testing and monitoring that should be addressed in a pilot test protocol,
including operational parameters, water quality, and microbial monitoring (where applicable),
and integrity testing.
2.3.1. Operational Parameter Monitoring
Monitoring pilot unit operational parameters is an important means of assessing system
performance and tracking the rate of membrane fouling. The following operational parameters
should be monitored continuously, if possible:
1. Elapsed run time
2. Pressure (feed, filtrate, and concentrate)
3. Flow (feed, filtrate, and concentrate)
4. Temperature (feed or filtrate)
Another important consideration in the evaluation of a membrane process is operational
data collection for the intermittent process sequences, such as backwashing. For these
intermittent processes, the design parameters (e.g., flows, times, volumes) associated with
air, water, or chemical usage during the sequence should be established and verified during
pilot testing. It is not uncommon for the pilot unit to operate under different parameters than
those that would be considered appropriate for a full-scale unit. For example, a pilot system
generally has faster pneumatic valve actuation times and a shorter overall backwash sequence
than a full-scale unit. Some of these discrepancies are unavoidable; however, these scale-up
issues should be noted for consideration prior to initiating pilot testing.
2.3.2. Water Quality Monitoring
The particular water quality data collected during a pilot study will depend upon the type
of membrane filtration system, site-specific treatment objectives, and foulants of concern. In
general, Table 8.2 can be used as a guideline.
In addition to those flows listed in Table 8.2, it is recommended that the MF/UF backwash
flow be checked weekly for total suspended solids (TSS) and turbidity. Note that the
recommended parameters and sampling frequencies should be modified to meet the requirements
and objectives of each particular site-specific pilot study. The sampling frequencies
may also be modified during the course of a pilot study if conditions warrant.