In the sewage treatment of papermaking, steel, metallurgy, mineral processing, chemical industry, electroplating, slaughtering, urban sewage and other industries, polyaluminium chloride and polyacrylamide are often added to accelerate the sedimentation rate of pollutants in the water during the flocculation and sedimentation process. When adding agents, polyaluminium chloride is added first and then polyacrylamide. So why does polyacrylamide need to be used with polyaluminium chloride? Why add polyaluminium chloride first and then polyacrylamide?
To answer the above questions, we need to know what the functions of polyaluminium chloride and polyacrylamide are respectively.
The role of polyaluminium chloride
1. The aqueous solution of polyaluminium chloride is acidic, with a pH value between 3.5 and 5.0, which can adjust the pH value of water quality;
2. The pH value range of water quality applicable to polyaluminium chloride is wider than that of polyacrylamide, between 3 and 12;
3. After polyaluminium chloride comes into contact with sewage, it will first form a flocculent group of small particles;
4. Polyaluminium chloride is a coagulant, also known as a coagulant aid, which can play a coagulant role;
5. Polyaluminium chloride has a certain demulsification ability;
6. When polyaluminium chloride is used alone, flocs will form in the water, but these flocs are not easy to settle. After the water quality is treated, it is very turbid and cannot achieve the effect of rapid flocculation and sedimentation.
The role of polyacrylamide
1. When polyacrylamide is used, the pH range of water quality is between 6-9;
2. When polyacrylamide is used alone, the amount added is large and the effect is poor. It is necessary to use a coagulant to adjust the pH value first.
Combining the role and usage characteristics of Lvyuan's polyaluminium chloride and polyacrylamide, we will understand: in the flocculation and sedimentation stage of sewage treatment, polyaluminium chloride must be added first, and then polyacrylamide.
The reason is: adding polyaluminium chloride first can adjust the pH value of water quality to 6-9, which is more suitable for the use of polyacrylamide. At the same time, polyaluminium chloride can also play a coagulant role, helping polyacrylamide to accelerate sedimentation, making the water clear and the sludge sinking.
If the order of their addition is reversed, not only will the treatment effect be unstable, but the amount of polyaluminium chloride and polyacrylamide will also increase.
Therefore, in the flocculation and sedimentation stage of sewage treatment, Lvyuan polyaluminium chloride PAC should be added first, and then Lvyuan polyacrylamide PAM should be added.