Membrane and Desalination Technologies - TCE Moodle Website

382 N.K. Shammas and L.K. Wang
7.3. Membrane Installation
Membrane module installation should be conducted according to the instructions obtained
from the manufacturer. Care should be taken not to damage the membranes during the
installation process. It is recommended that the location of each individual membrane in
the system be recorded according to its serial number. Factory test data are often shipped with
the membranes, and this information should be collected and filed.
Membrane modules are typically shipped “wet” with a liquid preservative solution. The
particular preservative depends upon the type of membrane. Most membranes are preserved
with a 1% solution of sodium bisulfite, a reducing agent that acts as a biocide to control
microbial growth. Prior to installation, the membrane modules should be stored in an
appropriate manner such that they are not subjected to freezing conditions that could damage
the membranes. Regardless of the membrane type, the preservative should be flushed to waste
after the membranes are installed. Note that the disposal of any preservative solutions should
be conducted in accordance with any applicable regulations.
Some membrane modules are shipped with more problematic storage solutions. For
example, glycerin solutions may pose a waste treatment issue because of the biochemical
oxygen demand (BOD) that may result from the solution being flushed down the drain. The
use of formaldehyde, once a common membrane preservative is generally no longer acceptable
and it may pose a significant disposal problem. Both state and local regulations regarding
chemical disposal may apply to membrane preservative solutions, and these may dictate
whether it is permissible to discharge these preservatives to the sanitary sewer, or if collection
and alternate disposal and/or treatment is required.
7.4. System Disinfection
Initial system disinfection typically involves the application of a disinfectant, such as a
chlorine solution, throughout the entire system, including both the feed and filtrate piping.
Although both soaking and recirculating procedures are used, recirculating the solution
through the system will generally provide more effective disinfection. This disinfection
step may be required by the state, and in any case is recommended to inactivate bacteria
or other pathogenic organisms that may contaminate the membrane filtration system and
associated piping. Because some membranes have limited compatibility with disinfecting
chemicals, the manufacturer may have specific requirements for the disinfection process,
and approval will be necessary if manufacturer recommendations differ from state requirements.
General procedures for the disinfection of both chlorine-tolerant and chlorineintolerant
membranes are described in the following sections. In either case, once the
system disinfection is complete, the entire system (including the membranes) should be
flushed prior to placing the membrane unit(s) into continuous service. This final flush can
be conducted according to guidelines and should continue until the desired filtered water
quality is attained as measured by site- or membrane system-specific water quality
parameters.