Turn the water-quality need into a measurable question
First define what must be separated and how the filtrate will be used. Protecting RO from colloids, separating MBR sludge and substantiating a microbiological barrier are different objectives. Specify inlet and outlet parameters and the analytical method. A general request to remove viruses or reduce COD can conceal requirements that need different treatment steps or different forms of supporting evidence.
Assign a verification condition to each objective: representative water, temperature, operating state and sampling location. Distinguish quality delivered by membrane separation from quality dependent on the complete process. In an MBR, biological conversion and solids separation perform different functions. This distinction helps the buyer request appropriate documentation rather than expecting one pore-size number to substantiate every treatment claim.
Read nominal pore size and MWCO with their test methods
The EPA technical guidance distinguishes pore characterisation from removal efficiency and module integrity. When comparing quotations, ask how the stated pore size is determined and which product revision it covers. Use this information to understand membrane structure, then complete the comparison with results relevant to the actual contaminant that the project needs to control or the downstream equipment it needs to protect.
If the data sheet uses MWCO, request the test solute, conditions and retention criterion. MWCO is expressed as molecular mass, usually daltons, whereas pore diameter is a length. Preserve each quantity's definition. Converting kDa automatically into micrometres with a generic chart can make two products appear equivalent even though their characterisation methods and measured separation behaviour are different.
Request the report behind a log-removal claim
Log removal is expressed as LRV = log10(Cfeed/Cfiltrate), using comparable concentrations. For example, reducing 100,000 units per litre to 10 gives 4 log removal, equivalent to 99.99%. This is a mathematical illustration. Assessing an actual result requires the organism or marker, analytical method, detection limits and test conditions, including how feed and filtrate samples were obtained and compared.
Check the report's connection to the quoted model, including fibre type, configuration, manufacture and the scope of tested units. Identify whether the value comes from a challenge test, an operating sample or a general catalogue statement. If filtrate concentration is below the analytical limit, the report should explain how that result is expressed. It does not automatically establish complete absence of the contaminant.
| Quoted information | What it describes | Supporting purchasing document |
|---|---|---|
| Nominal pore size | Membrane characterisation | Method and model data sheet |
| MWCO | Solute separation under test conditions | Solute, conditions and criterion |
| Log removal | Measured concentration ratio | Test report and analytical limits |
| Integrity | Condition of the tested barrier | Procedure and acceptance criterion |
Connect performance to assembly integrity
A membrane operates within a module that includes potting, seals and connections. Define the start-up and operational checks used to identify loss of barrier integrity. EPA guidance treats challenge testing and integrity verification as related parts of assessment. Its technical framework helps structure purchasing questions, while the requirements for the intended water use are established with the relevant project and authority.
Request the procedure, test conditions, instrumentation, threshold and response to a deviation. Establish which parts of the assembly are included and how a leak is located. This turns purchasing documentation into an operational tool. The article on pressure-decay testing develops that particular method; the purchasing task is to define which evidence accompanies the module and how operations will use it after installation.
Compare complete data sheets and close the quality duty
Neptuno's data sheets present nominal pore size alongside materials, membrane area, dimensions and operating conditions. Read these together to organise the enquiry around the exact model, permitted exposure and separation objective. Complete the retention documentation with the test appropriate to the required parameter. Apply the same questions when assessing PES, PVDF and MBR families for the project.
Record the required result, feed conditions, documentary scope and acceptance criterion in the quotation. Distinguish solids and colloid removal from removal of salts and small dissolved constituents. Where the objective includes the latter, review the additional treatment needed. A purchase becomes clearly specified when each quality claim is linked to a data item, a report or a defined service test that can be reviewed by the buyer.
Common questions
Does smaller pore size always mean a better offer?
Compare the quality objective together with flux, pressure, washing and integrity. Pore size is one selection parameter rather than the complete decision.
What does below detection limit mean?
The method cannot quantify a concentration below that limit. The report should explicitly account for the limit when calculating or bounding retention.
Will UF reduce conductivity like reverse osmosis?
Conventional UF is principally selected for solids, colloids and separations associated with its cut-off. Dissolved-salt reduction requires assessment of another process.