MF-570 Microfiltration — Module Format and the Backwash Cycle

MF-570Microfiltration — Module Format and the Backwash Cycle

A physical sieve at around 0.1 micron. It takes out suspended solids, algae and protozoa completely, and it does it at under a bar — but it blinds as it works, so the design is really a design of the cleaning cycle, and the module format decides what cleaning is even possible.

Cutaway — Microfiltration — Module Format and the Backwash Cycle

WaterSuspended solidsPermeateBackwash

How it works

An absolute barrier — Unlike a sand filter, MF is a true barrier: nothing larger than the pore gets through, whatever the loading. That is why it displaced conventional filtration for protozoa removal — the log removal does not degrade as the run progresses.
How the membrane is packaged — The same square metre can be a hollow fibre, a tube, a flat sheet or a ceramic monolith. Packing density runs from 50 to 900 m²/m³, so the format sets module count and footprint before the duty does. Switch format above and watch the rack size move.
Flux and TMP — Flux is what you demand; transmembrane pressure is what it costs. Their ratio is permeability, and permeability falling is the single number that tells you the membrane is fouling. Watch the trace climb through each run.
The backwash cycle — Every 20–60 minutes the flow reverses and the cake is lifted off. Most of the TMP comes back — but not all, and that residue accumulates run on run until a chemical clean is needed. A flat sheet cannot do this at all; it relaxes and air-scours instead, and pays for it in cleaning frequency.
Choosing a format — Flux against fouling rate, and format against feed. Hollow fibre for anything municipal. Tubular when the feed would plug a fibre. Flat sheet in mixed liquor. Ceramic when the water is hot, oxidising or valuable. The cheapest membrane plant is usually the one running at modest flux in the cheapest format the feed allows.
Outside-in hollow fibre — Feed on the shell side, permeate collected in the bore. There is no narrow channel to plug, so hair, fibre and grit pass by rather than blocking an entrance, and the outside of the bundle can be air-scoured. That tolerance is why it dominates municipal surface water.

Design parameters

The panel opposite runs the same correlations as the MF-570 design sheet, so the animation and the calculator cannot disagree. Every parameter below is live — drag one and the picture responds.

Parameter	Unit	Default	Range
Module configuration
Format		Hollow fibre outside-in	5 options
Spiral-wound is left out: it cannot be backwashed, and an MF duty that needs no backwash is rare enough not to be the lesson.
Duty
Permeate flow	m³/h	60	5 – 400
Design flux	LMH	95	15 – 440
Clean TMP	bar	0.2	0.05 – 0.9
Cleaning cycle
Filtration interval	min	30	10 – 90
Fouling rate	bar/30 min	0.06	0.01 – 0.35

Open the full MF-570 design sheet for the other six inputs, all twenty-six results with their envelopes, the six equations printed beside the numbers they produce, and a calculation record you can export and put in a design file.

Live parameters

Five of the eleven inputs the MF-570 design sheet takes.

Module configuration

Format

Spiral-wound is left out: it cannot be backwashed, and an MF duty that needs no backwash is rare enough not to be the lesson.

Duty

Permeate flow 60 m³/h

Design flux 95 LMH

Clean TMP 0.2 bar

Cleaning cycle

Filtration interval 30 min

Fouling rate 0.06 bar/30 min

You have an estimate. The design sheet is the justification.

This page sizes the unit on five variables and tells you whether the headline numbers land in range. That is enough to sketch with, and it stays free. What it will not do is survive a design review: it does not show you the equation behind any number, it checks the obvious limits rather than all of them, and there is nothing to file.

The MF-570 design sheet runs the same physics on eleven inputs, reports twenty-six results against their envelopes, prints the six governing equations beside the numbers they produce, and exports the lot as a calculation record for the design file.