2. Physical treatment: through the separation of the physical effect, can be recovered in the wastewater insoluble in the suspended state of the pollutants (including the oil film and oil beads) of the wastewater treatment method, can be divided into gravity separation method, centrifugal separation method and sieve retention method;
3. Physical treatment: the physical separation can recover the undissolved pollutants in the wastewater in suspension (including oil film and oil beads), which can be divided into gravity separation, centrifugal separation and sieve filtration and retention method;
3. Chemical treatment: generally through chemical reaction and mass transfer to separate, remove the wastewater solution was dissolved, colloidal state of pollutants or convert them into harmless substances of a wastewater treatment method;
4. Biological treatment: mainly through the metabolism of micro-organisms, so that wastewater was solution, colloidal and fine suspended state. Biological treatment: mainly through the metabolic action of microorganisms in the wastewater is a solution, colloid and fine suspended state of organic pollutants, can be converted into stable, harmless substances of a wastewater treatment method.