With the acceleration of urbanization, the production of industrial and domestic sewage is increasing, and sewage treatment has become one of the important problems to be solved in modern society. Sludge is a by-product of the sewage treatment process, and its dewatering treatment has become one of the key steps to enhance the efficiency of sewage treatment and reduce disposal costs. In recent years, poly(dimethyldiallylammonium chloride) (PDADMAC), as a kind of polymer chemical agent, has been widely used in the field of sludge dewatering due to its good flocculation performance.

I. Properties and characteristics of PDADMAC

Poly(dimethyldiallylammonium chloride) is a cationic polymer chemical with good water solubility and strong flocculation. It is made of diallylammonium chloride (DADMAC) monomer polymerization, the molecular structure contains a large number of cationic groups, so that it has a strong adsorption capacity, and can be formed with the sludge in the negatively charged substances stable floc.

Main features:

Strong flocculation performance: its cationic groups can quickly react with colloidal particles and suspended matter in sludge, prompting them to aggregate into larger flocs, which is convenient for subsequent dewatering treatment.

Low additive amount: Compared with traditional inorganic flocculants, under the same conditions, polydimethyl diallylammonium chloride requires less additive amount, thus reducing the cost of use.

Wide pH adaptability: insensitive to changes in water pH, able to work effectively under a wide range of acid and alkali conditions.

Environmentally friendly: polydimethyl diallylammonium chloride has less impact on the environment during use.

2. the principle of action in sludge dewatering

Sludge dewatering is a complex process, mainly including flocculation, sedimentation, filter press and drying. The application of polydimethyl diallylammonium chloride in sludge dewatering is mainly reflected in its good flocculation effect. The specific principles are as follows:


Adsorption and bridging: poly(dimethyldiallylammonium chloride) has adsorption reaction with negatively charged particles in sludge through its cationic group to form stable floc. In addition, the long chain structure of the polymer chain can connect different particles together through the “bridging” effect, forming larger flocs and promoting the aggregation of sludge.

Degradation and polymerization: Under the action of dimethyldiallylammonium chloride, the macromolecular organic matter and fine particles in sludge can be degraded and polymerized to form larger particles, which can enhance the settling performance and filtration performance of sludge.

Moisture discharge: through the flocculation effect of polydimethyl diallylammonium chloride, the water in sludge is wrapped in the floc formed, and then it is well discharged in the dewatering equipment, which improves the dewatering efficiency of sludge.

3. the application effect in sludge dewatering

Improve the dewatering efficiency: the use of polydimethyl diallylammonium chloride can improve the dewatering rate of sludge. In some sludge dewatering experiments, after using polydiallyldimethylammonium chloride as flocculant, the dewatering efficiency is significantly improved compared with traditional chemicals (such as polymerized aluminum chloride), and the water content of the dewatered sludge is significantly reduced.

Reduce the cost of sludge treatment: Due to the good flocculation performance of polydimethyl diallylammonium chloride, its use is small, which reduces the purchase and transportation cost of flocculant. In addition, the reduced volume of the dewatered sludge also helps to reduce the cost of subsequent disposal and transportation.

Improvement of filter cake properties: PDMCC can improve the quality of filter cake after sludge dewatering, making it more dry and treatable for further disposal (e.g. incineration, landfill, etc.).