Polyacrylamide according to ionic characteristics can be divided into non-ionic, anionic, cationic polyacrylamide types. According to the molecular weight to have different specifications of molecular weight, ionic degree and so derived a lot of models, in the face of the market messy specifications system, for their own sewage system to optimize the best polyacrylamide model is very difficult, how to solve the common problems of sewage or sludge polyacrylamide selection.

1. Understand the source of sludge

Sludge is the inevitable product of sewage treatment, first of all, we should understand the source of sludge, properties, composition and solid content. According to the main components of sludge, sludge can be divided into organic sludge and inorganic sludge.

In general, cationic polyacrylamide is used to treat organic sludge, anionic polyacrylamide is used to treat inorganic sludge, it is not easy to use cationic polyacrylamide when the alkaline is very strong, and it is not appropriate to use anionic polyacrylamide when the solid content of the sludge is high, usually the amount of polyacrylamide is larger.

2. Molecular weight selection of polyacrylamide

Polyacrylamide molecular weight refers to the length of the molecular chain in the molecule, the molecular weight of polyacrylamide between 5-18 million, in general, the higher the molecular weight of polyacrylamide products, the greater the viscosity, however, in use, not the higher the molecular weight of the product, the better the use of the effect, specific in use, To determine the appropriate polyacrylamide molecular weight according to the actual application industry, water quality, treatment equipment and other conditions.

Polyacrylamide is a high molecular weight coagulant. According to its average molecular weight, the product can be divided into low molecular weight (< 1 million), medium molecular weight (2-4 million) and high molecular weight (> 7 million) three categories.

Polyacrylamide is used in sewage treatment, molecular weight from millions to tens of millions of polymer water-soluble organic polymers. Domestic polymer polyacrylamide: non-ionic polyacrylamide (abbreviated NPAM, molecular weight 800-15 million), anionic polyacrylamide (abbreviated APAM, molecular weight 800-20 million), cationic polyacrylamide (abbreviated CPAM, molecular weight 800-12 million, ionic degree 10%-80%).

If it is simply used as a coagulant aid, the higher the general molecular weight, the tighter the flocs and the less medication, but the molecular weight of anionic polyacrylamide is recommended not to exceed 20 million.

If in sludge dewatering. The use of belt filter press, the general molecular weight can not be too high, if the molecular weight is very high may lead to clogging of the filter cloth, affecting the dehydration effect; For example, if you use a centrifugal filter press, the molecular weight requirements will be higher, because the centrifugal filter press requires that the floc can be shear resistant as much as possible, so choose a relatively high molecular weight product.

3, the ionic degree of polyacrylamide selection

For the sludge to be dehydrated, flocculants with different ionic degrees can be screened through small experiments to select the best suitable polyacrylamide, so that the best flocculant effect can be achieved, and the dosage can be minimal and cost can be saved. Select ion degree key look:

(1) The size of the floc

Flocs size: flocs too small will affect the speed of drainage, flocs too large will bind more water and reduce the mud biscuit degree. The size of the floc can be adjusted by selecting the molecular weight of the polyacrylamide.

(2) Floc strength (moisture content)

Strength of floc: Floc should be stable and not broken under shearing. Increasing the molecular weight of polyacrylamide or selecting suitable molecular structure is helpful to improve the stability of floc.

(3) Mixing of polyacrylamide and sludge

The polyacrylamide must fully react with the sludge at a certain position in the dewatering equipment to flocculate. To this end, the viscosity of the polyacrylamide solution must be appropriate, and it can be fully mixed with the sludge under the existing equipment conditions, and whether the two are evenly mixed is a key factor for success. The viscosity of polyacrylamide solution is related to its molecular weight and preparation concentration.

(4) Dissolution of polyacrylamide

Only when the dissolution is good can the flocculation be fully exerted. As mentioned earlier, the dissolution process of polyacrylamide is actually the ripening process of polyacrylamide, and sometimes it is necessary to speed up the dissolution rate, at which time the concentration of polyacrylamide solution can be considered.

Therefore, the best product choice should be determined by the laboratory beaker experiment.

It can be seen from the above that the choice of molecular weight and ionic degree is not absolute, it is best to do the selection test before choosing polyacrylamide, it is best to operate the test on the machine, so that the data obtained is the most accurate, and the preferred polyacrylamide is more cost-effective.