Process reasoning
Suspended particles can respond to sedimentation or be retained in a filtration cake, depending on size, density, liquid properties and the chosen separation principle. Dissolved salts remain in the liquid unless the process creates a separable phase, for example by crystallization. Analytical measures such as total solids, suspended solids, turbidity and conductivity describe different properties. A low suspended-solids result does not imply low dissolved salt concentration.
ILLUSTRATIVE EXAMPLE
Apply the reasoning
An illustrative wastewater contains suspended mineral fines and dissolved salt. A decanter trial may lower the suspended-solids load while leaving much of the dissolved salt in the centrate. If the final requirement is low conductivity, another treatment duty must be considered. Conversely, a crystallization process can turn part of the dissolved product into crystals that a filtration centrifuge may then recover.
What to record
| Item | Basis to document |
|---|---|
| Suspended solids | Particles present as a separate phase; specify the test method |
| Dissolved solids | Material in solution; mechanical separation alone is insufficient |
| Turbidity | Optical response; not a universal conversion to solids mass |
| Conductivity | Useful indicator for ionic solutions; not a direct cake-recovery measure |
Review checklist
- Define the contaminant or valuable component explicitly.
- Distinguish liquid clarity from chemical purity.
- Check whether sampling changes temperature or causes precipitation.
- Agree which analytical result is the acceptance measure.
Your next decision
Ask for a process review when a specification combines solids removal with dissolved-component removal. A centrifuge may be one stage in a larger system, with crystallization, extraction, membranes or other treatment providing a different function. Clear phase definitions prevent an impressive-looking solids recovery percentage from being applied to the wrong material.