Physical-chemical purification plants allow water pollutants – often not biodegradable – removal using chemical reagents. These additives react with pollutants and make them insoluble so that they are broken down by neutralization, coagulation/flocculation, precipitation.
Chemical-physical plant projects are studied case by case and based on in relation to the peculiarities of the water to be treated, the discharge parameters and customer demand.
The chemical-physical process phases are basically:
- Homogenization
- Insolubility of metal salts
- Coagulation – flocculation
- Sedimentation
- Final treatments
HOMOGENIZATION
The water to be treated is stored in a homogenization tank placed at the head of the plant to feed the purification process with permanent parameters water.
INSOLUBILIZATION METAL SALTS
Acid/alkaline waters coming from the homogenization section contain dissolved metallic salts. At a certain pH value by adding suitable reagents, metals precipitate as hydroxide.
COAGULATION – FLOCCULATION
Colloids are made by solid or liquid particles mixture; they are small size and their surface is covered by negative charges as to give them a high stability. The coagulants/flocculants reagents addition destabilises the colloidal system and allows the particles aggregation to flakes; their mass and size implies their sedimentation.
SEDIMENTATION
The water and flakes are separated inside the sedimentation section; in this tank the water is calm so that sludge may lay down on the bottom while the clarified water flows to the final treatment.
FINAL TREATMENTS
The water coming out from the sedimentation tank is pumped to neutralization and final refinement sectors; they consist in a physical filtration process such as quartz and/or active carbon. The sludge settled in the sedimentation tank is generally filtered to reduce its water content.
