High-quality clarification of effluents guarantees complete safety for the environment when they are discharged into water bodies. The sewage treatment process takes place in several stages. One of them is the use of flocculants for wastewater treatment. Due to a chemical reaction, all micro and macro suspensions in the composition of sewage become larger. This allows them to be removed in the future mechanically.
Definition and purpose
- preliminary purification of water from reservoirs before its supply to city communications;
- clarification of industrial effluents from dairies, chemical / pharmaceutical industries, etc.;
- household waste water treatment.
Flocculation is also an integral part of such processes as the production of drugs, enrichment, and refining of petroleum products.
Types and classes of flocculants
All flocculation reagents are divided into classes according to the type of their origin:
- Organic (natural): guar gums, starch and dextrin, sodium alginate, cellulose ether.
- Inorganic: silicic acid. It acts especially actively against metal hydroxides - aluminum, iron, magnesium, etc. As a result of the work of silicic acid, heavy, durable flakes are formed.
- Synthetic: High molecular weight compounds that dissolve organically in water and have molecular weights ranging from thousands to millions.
There are also cationic, anionic and neutral flocculants (in terms of electric charge). The most popular is the latter type - polyacrylamide (PAA). Aggregate state of reagents: liquid and powder.
The principle of operation of flocculants in water
- All flocculants interact with colloidal particles. First, they settle on their surface, significantly disrupting the water-salt balance of the shell. In parallel, flocculants nullify the electric charge of colloidal impurities. Initially, all colloidal compounds are, as it were, surrounded by a shell that prevents particles from sticking together. It is destroyed by a flocculant.
- Due to its high molecular weight and the reactions that have already taken place in water, the reagents are fixed on the surface of foreign impurities. At the same time, they form a kind of bridges, due to which a bond is formed between the molecules of flocculants.
- As a result, all suspended particles of colloidal solutions stick together into large visible flakes. They are also called floccules.
After the reaction has passed, foreign impurities in the form of flakes can be easily removed from the clarified liquid. This is done using mechanical filters.
The effectiveness of the chemical method
- clean the most polluted domestic / industrial wastewater;
- seriously accelerate the process of precipitation of impurities in the liquid;
- prevent the possible ingress of contaminants into the water at the next stages of cleaning;
- to refuse additional costs for enhancing the productivity of the treatment plant;
- increase the service life of mechanical VOC filters;
- to reduce the cost of capital wastewater clarification.
All the effects of the use of flocculants can only be discussed if the method is used in combination, after the coagulation stage. As a rule, the reagents themselves do not fully purify water, the method does not work.
It is especially important to include the flocculation process in the wastewater treatment system if the station will soon receive large volumes of polluted water. Here, without a thorough modernization of the VOC and significant financial investments, it will be possible to maintain the performance of the treatment plant. In fact, you will have to spend only on the purchase of a powder-flocculant.
The use of this method in everyday life is irrelevant, since the process is complex and unjustified for a small volume of contaminated water.
