| Physical Treatment |
Includes sedimentation, filtration, air flotation, etc. |
Simple process, low cost, easy operation |
Only suitable for suspended solids or larger particles; limited removal efficiency |
| Chemical Treatment |
Such as neutralization, coagulation, redox reactions |
Effective for heavy metals and hard-to-degrade organics |
Requires chemicals; possible secondary pollution; higher cost |
| Biological Treatment |
Mainly aerobic and anaerobic treatments, like activated sludge and biofilm processes |
Low cost, capable of degrading most organics |
Sensitive to operational conditions (temperature, pH, etc.); long start-up time |
| Membrane Separation (RO, UF, NF, etc.) |
Uses membrane technology to separate dissolved substances |
Excellent effluent quality, small footprint, potential for water reuse |
High initial investment, prone to fouling and scaling; requires periodic maintenance |
| Advanced Oxidation Processes (AOPs) |
Includes ozone oxidation, Fenton's reagent, photocatalysis, etc. |
Degrades most recalcitrant organics |
High energy consumption, high O&M costs; best for difficult wastewaters |
| Evaporation & Crystallization |
Mainly for high-concentration brine |
Enables zero liquid discharge (ZLD) |
Very high energy consumption, significant capital cost |
| Adsorption (e.g., activated carbon) |
Suitable for trace pollutants |
Efficient removal of trace organics or heavy metals |
Adsorbent requires regeneration or replacement, high operational cost |
