How to choose flocculant? - CHINAFLOC
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How to choose flocculant?
2015-03-23 12:54:10

How to choose flocculant?

Normally,the flocculant can be divided into inorganic and organic flocculant.we should choose the right flocculant according to the characteristics of  the wastewater.meanwhile,we should know which prosess the flocculant will be added and what it is used for.

How to choose flocculant depends on the concerntration of the colloid and suspended matter in the water.if the pollutants show colloidal state,we should choose inorganic flocculant to make it destablization and flocculation,if the floc is small,we need to add high molecular flocculant or can be used  in conjuction with activated silica gel as coagulant aid。It can obviously improves the effect of coagulation and expand the application range if the inorganic floccluant be used in concert with the organic flocculant.for high molecular,for the high molecular, the charge on the chain-shaped molecular is greater ,the charge is higher and the chain can be extend fully,the effective range of absorption and bridging is also bigger,the flocculent effect is better.we should consider the composition and PH value of the wastewater when choosing the inorganic flocculant ,and then choose the optimum model.we should consider if it is anionic PAM or cationic PAM or nonionic PAM when choosing the organic flocculant.the anionic PAM can be divided to weak ,medium and strong anionic PAM according to the different hydrolysis degree.the cationic PAM mainly used for sludge dewatering,the selection test is very important,for  municipal sewage treatment,we often use cationic PAM with medium or strong ionicity.the cationic PAM with weak ionicity often be used for the sludge dewater  of  papermaking and dyeing plant.the cationic PAM with strong ionicity often be used for medical wastewater treatment.

Choosing the right flocculant according to the following the aspects:

1.the molecular structure:the molecular structure of flocculant depends on the dewatering performance be required.the structure of cationic flocculant as follows:

linear structure:after choosing the right molecular weight,the dosage is small and the dewatering performance is better if we make the dewatering treatment using linear flocculant.

Dendritic structure:medium dosage,can obtain better dewatering performance.

corss-linked structure:big dosage but can get special water filtering and and shear resistance performance

2.the molecular weight::The choice of molecular weight depends on the types of dewatering equipment, and molecular weight are also said the length of the polymer chain. For centrifuge equipment , the higher of the molecular weight the  better of the application result, because in centrifugal dewatering engineering, floc will be subject to a large shear force. For the filter type equipment:,the lower molecular weight to the medium molecular weight flocculant meet the requirement, meanwhile,we  can get a good  water filtering performance..

 3.Choosing the flocculant charged according to the type of particles in waste water. In general, we will use the flocculant with negatively charged  to capture the particle in inorganic sewage , treat organic particles with positively charged flocculant , of course, we have to confirm the the best flocculant throught simple test and pratice on machine.

4.Flocculant charge density (ionic degree): that mean the quantity that the flocculant will be positive charge or negative charge to get the best flocculent result if the caseof minimum quantity. the charge density is related to the type of sludge, municipal sludge is often a function of the content of organic matter in the sludge,the organic content is related to the content of Volatile components.the higher of the Volatile content,the higher charge of the flocculant we need.

Each kind of waste water has its own unique characteristics, nonionic polyacrylamide is mainly used in acidic condition, printing and dyeing mill often use nonionic PAM. We can only confirm the final model according to the selection test .we can confirm the economic and optimum flocculant according to the dosage , flocculent and sedimentation result and the cost.