The treatment capacity of a
1990's vintage conventional water treatment plant was to be expanded from 20 to 42 mgd. The owner desired to provide capacity expansion while
ensuring the ability to comply with the worst-case disinfection
requirements of the proposed Long Term 2 Enhanced Surface Water
Treatment Rule (LT2). The plant's existing
treatment process includes pre-ozonation, conventional
filtration, post-ozonation, GAC adsorption and chlorine
disinfection.
Alternatives
Two treatment process options for
meeting the owner's requirements were evaluated for cost and
effectiveness: 1) adding UV disinfection to the current
treatment process; and 2) replacing conventional filtration with
membrane filtration. The membrane filtration option was
pilot tested and selected for plant expansion.
Warranty
Considerations
In preparing the
specifications and procurement documents for the membrane
equipment, strong consideration was given to ensuring the
membrane system would meet operational requirements over its
entire life. In order to minimize operational costs and avoid negative
impacts on other treatment processes, warranty requirements were
developed and negotiated to assure system integrity and to limit wastewater production, chemical cleaning
frequencies and upstream and downstream flow variation
associated with membrane cleaning.
O&M
Considerations
A long-term service
agreement was capitalized and stipulated in the warranty to
require the manufacturer to provide maintenance and replace the
membrane modules upon failure. The membrane fibers were also
required to pass periodic challenge and porosity testing.
Membrane cleaning chemicals were specified to meet NPDES permit
requirements, and waste neutralization system redundancies were
established to avoid delays in membrane cleaning; or the need to
discharge un-neutralized waste to the on-site wastewater handling
facilities.
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