Maintenance vs recovery cleans
Maintenance cleans are short, low-strength cleans done routinely to slow fouling. Recovery cleans are longer, stronger soaks done when permeability has dropped. A healthy plant relies mostly on maintenance cleans, with recovery cleans spaced months apart. Zyramic Swing uses reverse-flow chemical cleaning with relaxation rather than pressurized backwash.
Root causes of frequent cleaning
- Flux set too close to peak for long periods
- Biological stress: low DO, short SRT, nutrient deficiency or toxic slugs
- High or poorly mixed MLSS in the membrane zone
- Wrong chemistry for the foulant (oxidant for organics, acid for scale)
- Old or damaged membranes that no longer recover
Fixes
Re-check design flux against actual flow, stabilize the biology, confirm screening, and match cleaning chemistry to what recovers permeability. If membranes are past their best, replacing them can cut cleaning frequency sharply. Adding membrane area, by populating spare positions or adding Swing cartridges, also lowers flux per square meter. See fouling and high TMP.
| Mild backwash (special cases only) |
|---|
| Backwashing is not a standard Swing operating mode and is not meant for routine use. Swing has been pressure-tested to 14.5 psi (1 bar) and held without breaking. If a site is in a bind even after relaxation and CIP, contact us; we may be able to work out a special mild-backwash procedure. |
Worked sizing example
Take a 118,877 gpd (450 m³/day) plant cleaning monthly:
| Item | US | Metric | Note |
|---|---|---|---|
| Average flow | 118,877 gpd | 450 m³/day | about 83 gpm (18,750 L/h) |
| Design flux (gross) | 8.8 gfd | 15 LMH | Zyramic design guidance |
| Derate for relaxation and cleaning | ~20% | ~20% | |
| Net flux | ~7.1 gfd | ~12 LMH | |
| Membrane area needed | ~16,819 ft² | ~1,562 m² | average flow ÷ net flux |
| Swing-8 cartridges | ~125 | ~125 | 135 ft² (12.5 m²) each |
| Peak factor | ~2.0 | ~2.0 | |
| Peak flow | ~237,755 gpd | ~900 m³/day | extra area, short-term higher flux, or equalization |
This is an illustration only; a real design also checks temperature, MLSS, redundancy and the cleaning schedule.
Tips for a smooth project
- Look for the root cause before increasing cleaning strength
- Use temperature-corrected permeability when judging membranes
- Check screens for bypasses after storms
- Plan replacements ahead of permit deadlines
Next step
Membrane issues are easiest to resolve early. Send your trend data, cleaning records and a few photos, and we will give you our read on whether to focus on pretreatment, biology, operation or the membranes themselves, and a sensible next step, whether that is a change in procedure, a partial replacement or interim capacity.
Sizing considerations
To give a useful recommendation we usually need:
- Current cleaning schedule and chemicals
- Permeability before and after cleans
- Flux vs design
- Biological parameters
- Membrane age
Most relevant product: Swing MBR. See also replacement membranes, rentals and how to choose.
Why engineers look at Zyramic flat-sheet modules
| Item | Details |
|---|---|
| Smaller sheets, less wear and tear | each sheet flexes less in service, and a damaged unit affects less area. |
| Strong wide membrane welds | designed to resist delamination over the membrane's life. |
| Thick, robust membrane | about 250 microns including support. |
| Assembled in Poughkeepsie, NY | of domestic and imported components. In our Poughkeepsie shop we cut and weld membrane sheets to plates, build module frames and assemble complete modules. For funded projects, tell us your domestic-content requirements and we'll review what we can document. |
| Buy, rent or replace | new modules, rentals and pilots for US projects, and replacement membranes that fit many existing cassettes. |
Performance and life depend on pretreatment, design flux and operation; flux figures are Zyramic design guidance, sized to each project.
Frequently asked questions
How often should an MBR need a recovery clean?
It varies by design, but most well-run plants go months between recovery cleans.
Can adding membrane area reduce cleaning?
Often, because lower flux slows fouling.
Is hypochlorite safe for your membranes?
Within the published limits, yes. Ask for our cleaning guidance.
Can you review our cleaning program?
Yes, send your records with a quote request.
Which chemicals are typical?
Sodium hypochlorite for organic and biological fouling and citric or oxalic acid for scale are common, used within the membrane limits.
Can automation help?
Automated maintenance cleans on a fixed schedule usually keep permeability steadier than ad hoc manual cleaning.