Describe the complete exposure envelope
List minimum and maximum temperature, pH, oxidants, solvents, oils and process variability. Separate continuous exposure from short cleaning events. Record concentration, duration and frequency: compatibility with a cleaning step does not imply suitability for receiving the same chemical continuously throughout the operating campaign.
Request written limits for the membrane, potting, seals, housing and connections. Modules made from the same named polymer may use different formulations and structures. The Inge manual, for example, describes a particular product family; its approved envelope cannot be treated as a property of every PES membrane.
Module geometry can matter more than the polymer
Compare dead-end and crossflow operation, inside-out and outside-in flow, channel opening and cleaning options. Fibrous or coarse solids may require screening and different circulation even where two modules use the same material. Pretreatment and maintenance access are therefore part of membrane selection rather than optional details.
An outside-in UltraFlux™ system and another manufacturer’s tubular crossflow configuration require a separate hydraulic and mechanical assessment. Similar nominal cut-off does not make them directly interchangeable. For a retrofit, specify which pumps, headers, controls and operating sequences remain and which require modification.
Test cleaning and recovery over repeated cycles
Use representative samples and record net flux, TMP, axial loss where applicable and consumption over multiple operating cycles. Determine which cleaning procedure restores permeability without compromising integrity or selectivity. Ceramic resistance to demanding conditions can be useful, but the seals and housing still require their own checks.
A brief clean-water test cannot establish the preferred alternative. Include reasonably foreseeable adverse feed conditions and concentration if that is the intended duty. Analyse filtrate against its end use: clear appearance does not demonstrate removal of dissolved salts or other soluble compounds that govern acceptance.
Request a service-cost comparison
Separate membrane area, net output, availability, energy, cleaning water, chemicals and replacement in each quotation. Add pretreatment, pumps, instrumentation, installation and access for module removal. Cost per square metre of membrane does not necessarily represent cost per useful cubic metre delivered to the process.
Agree acceptance criteria, supply boundaries and missing information. If an option needs cooler or cleaner feed, include the corresponding treatment cost. A defensible selection meets the defined duty with documented assembly limits and identified uncertainty, rather than relying on a generic promise of longer membrane life.
Common questions
Is PVDF always more resistant than PES?
There is no universal ranking for every formulation, oxidant and temperature. Compare the approved limits of the actual models.
Does ceramic UF remove more salt than polymeric UF?
Selectivity depends on the active layer and cut-off. A ceramic UF membrane does not become a desalination membrane because of its material.