At present, there are many sludge treatment technologies in China, including sludge dewatering, concentration, and drying. Sludge dewatering is the most difficult part in the process of sludge treatment, because generally the volume of the sludge is very large, and it is nearly impossible to be transported, the cost of sludge treatment will be greatly increased. The goal of the most ideal sludge dewatering treatment is to achieve the maximum sludge water removal, at the same time to preserve the dehydrated sludge solid particles as much as possible, and realize the goal of protecting the environment and safeguarding the physical and mental health of the people with maximum economic benefits.
Generally there are the following two chemical conditioning methods of sludge dewatering:
1. The combination of inorganic and organic flocculants
Inorganic flocculants can be used alone to strengthen the floc structure and obtain a certain conditioning effect, but this effect is not obvious, and more agents are needed and the flocculants formed are quite small with this method; Although the use of organic flocculant alone can form larger flocculants with a small dosage, the overall strength of flocculants is not enough, which is not conducive to the further sludge dewatering treatment. If the two flocculants are combined together, not only can the dosage be reduced compared with that of only one flocculant, but also large and strong flocculants can be formed, so as to achieve better sludge dewatering effect.
2. The combination of cationic polymer and nonionic polymer
The combination of the two polymers can avoid a sharp reduction in the effect of dehydration. The combination of cationic organic flocculant and nonionic organic flocculant can also enhance the strength of flocs to some extent. The mechanism is as follows: Firstly add cationic polymers in sludge and let them adsorb on the surface of the sludge to form primary flocs, then add nonionic polymers and let them absorb on the primary flocs to form larger flocs by the action of Van der Waals' force and water, thus obtaining pretty good flocculation effect.