Table 1 Effect of filter geometry, fabrication process, and operating conditions/parameters on xylem filter performance (flow rate, volumetric capacity (or filter lifetime), and rejection).
Performance metrics | Xylem filter geometry | Fabrication methods | Operating conditions/parameters | ||||
|---|---|---|---|---|---|---|---|
Sapwood area (A) | Thickness (t) | Dry preservation | Hot-water treatmentb | With cloth or GAC pre-filtration | Pressure used for driving flow (P) | ||
Alcohol treatmenta | Stacking multiple filters in seriesa | ||||||
Flow rate (Q) | \(Q \propto A\) | \(Q \propto 1/t\), if tracheids are well-connected, else decreases more rapidly with thickness. | Increases | \(Q \propto 1/n\), where n is the number of filters | No significant effect. | Generally increases; depends on water quality and pre-filtration process. | \(Q \propto P\) |
Volumetric capacity (V) | \(V \propto A\) is expected for the same driving pressures | Unknown | Increases | Unknown; may be comparable to a single filter. | Increases if self-blocking is more dominant than fouling due to contaminants in water, else significant effect is not expected. | Generally increases; depends on water quality and pre-filtration process. | Unknown; depends on how pressure affects fouling. |
Rejection: Filtration-based | No effect | Depends on particle size. Typically increases rapidly till thickness exceeds tracheid length; may not increase further if sapwood has resin canals, else theoretically expected to increase with length. | Increases | Increases; theoretically log-additive, if rejection of each filter is identical. | Depends on temperature and duration of treatment; may decrease rejection. Soaking at high temperatures or for long durations compromises rejection performance. | Depends on pre-filtration method used; GAC can augment performance by removal of chemical contaminants. | No significant effect expected. |
Rejection: Adsorption-based (viruses) | No significant effect expected if permeate flux is constant | Expected to increase for the same driving pressure. \(\tau \propto 1/t^2\), where \(\tau\) is contact time. | Unknown | Expected to increase; theoretically log-additive, if rejection of each filter is identical. | Unknown | Expected to decrease. \(\tau \propto 1/P\), where \(\tau\) is contact time. | |
