| Product Flow | Salt Rejection | Delta Pressure | Direct Cause | Indirect Cause | Corrective Action |
|---|
| Decreasing | Decreasing | Increasing in Second stage | Scale Fouling | No antiscalant Antiscalant underfed | Carry out mass balance, confirm that antiscalant is present in the concentrate stream and ensure shutdown flush operating to determine source of problem
Clean the system |
| Increasing in First stage | Colloidal Fouling | Poor pretreatment | Clean the system
Improve the pre-treatment performance |
| Compaction | Poor Pretreatment
System operation outside limits | Stop train and clean before the DP increases beyond 52 psi (3.6 bar)
Improve pretreatment as colloidal fouling on the front end membrane normally accompanies first element compaction |
| Incompatible Chemicals | Use of non-approved products
Carryover from pretreatment processes | Review chemical compatibly
Clean the system |
| Biofouling | Ineffective or absent biocide program | Carry out a bacterial survey
Disinfect/clean the entire system and piping
Add or increase biocide injection and continue to monitor until the system proves to be under control |
| No Change | No Change | Organic Fouling | Oil and/or Polyecltroclye residual in RO feedwater | Investigate source water and improve pretreatment
Clean the system |
| Increasing | No Change | Compaction | High pressure
Uneven flux | Compacted elements are irreparably damaged. Replace effected membranes and determine how to reduce pressure and re-balance flow rates |
| Increasing | Decreasing | No Change | Oxidation Damage | Free chlorine or use of an incompatible cleaner | Attempt to use Resize to restore performance temporarily
Replace affected elements |
| Membrane Failure | Product backpressure or vacuum , abrasion, installation damage to permeate tube | Remove source of backpressure/vacuum
Improve pretreatment |
| O-Ring leak | Movement or improper installation | If possible, probe elements to determine which membrane(s) in the vessel are effected
Replace o-rings, shim vessel
Determine how to avoid "ramming" the membranes during system start-up and shut down |
