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Method for selecting flocculant when treating sludge by sludge dewatering machine
- 2020-08-03-

Method for selecting flocculant when treating sludge by sludge dewatering machine

When sewage and sludge are treated by a sludge dewatering machine, some flocculants are often needed to achieve better treatment effects. When choosing a suitable flocculant, we generally start with the following four aspects.

1. Properties of sludge

For sludge with high organic content, the more effective flocculant is cationic. The higher the organic content, the higher the degree of polymerization of cationic flocculant. For inorganic sludge, anions can be considered. The difference in sludge properties directly affects the conditioning effect, scum and excess activated sludge are more difficult to dewater, and the dewatering performance of mixed sludge is somewhere in between.

Generally speaking, the more difficult to dewater the sludge flocculating dose, the finer sludge particles will lead to an increase in flocculant consumption, and the high organic content and alkalinity in the sludge will also lead to an increase in the flocculant dosage. In addition, the solid content of sludge also affects the dosage of flocculant. Generally, the higher the solid content of sludge, the greater the dosage of flocculant when using a sludge dehydrator.

2. Sludge pH

The pH of the sludge depends on the form of the hydrolysate, and the same flocculant has very different treatment effects on sludge with different pH. The hydrolysis reaction of aluminum salt is greatly affected by the acidity and alkalinity, and the acidity and alkalinity of the condensation reaction ranges from 5 to 7. Ferric salt conditioners are less affected by pH, and the pH range is 6-11. In sludge with a pH of 8-10, ferrous salts can be oxidized into flocs with lower solubility in hydrolyzed products with higher solubility.

Therefore, when selecting inorganic salt flocculants, the specific pH of the dewatered sludge must first be considered. If the pH deviates from the range of its coagulation reaction, replace it with another one. Otherwise, it is necessary to consider adding acid or alkali to adjust the pH of the sludge before conditioning the sludge.

3. Concentration of flocculant

The concentration of the flocculant not only affects the conditioning effect, but also affects the consumption of the agent and the output rate of the sludge dewatering machine mud cake. Among them, the effect of organic polymer flocculant is more significant. Generally speaking, the lower the concentration of the organic polymer flocculant, the less the consumption of the agent and the better the conditioning effect.

However, if the preparation concentration is too high or too low, the yield of mud cake will be reduced. The conditioning effect of the inorganic polymer flocculant is almost not affected by the concentration of the formulation. The concentration of the organic polymer conditioning agent is between 0.05% and 0.1%. The concentration of ferric chloride is 10%, and the concentration of aluminum salt is between 4% and 5%.

Fourth, the temperature of the mixed treatment liquid

The temperature of the sludge directly affects the hydrolysis of the flocculant. When the temperature is low, the hydrolysis will slow down. If the temperature is lower than 10°C, the flocculation effect of the sludge dehydrator will be significantly worse. The conditioning effect can be improved by appropriately extending the flocculation time. When the temperature is low in winter, attention should be paid to the heat preservation of the sludge dewatering machine, which should not be lower than 15°C to minimize the heat loss during the sludge transportation process.