Key points of flocculant selection for sludge dehydrator
1、 Sludge properties.
For sludge with high organic content, the more effective flocculant is cation. The higher the organic content, the higher the polymerization degree of cationic flocculant should be selected. Anions can be considered for the sludge mainly composed of inorganic substances. The different properties of sludge directly affect the conditioning effect, while scum and residual activated sludge are difficult to dewater, and the dewatering performance of mixed sludge is between the two. Generally speaking, the more difficult it is to dewater, the larger the amount of flocculant, and the smaller the sludge particles will lead to an increase in the consumption of flocculant. The high content of organic matter and alkalinity in the sludge will also lead to an increase in the amount of flocculant. 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 the sludge dehydrator.
2、 PH of sludge.
The pH of sludge determines the form of hydrolysate, and the treatment effect of the same flocculant on sludge with different pH is also very different. The hydrolysis reaction of aluminum salt is greatly affected by pH, and the pH range of its coagulation reaction is 5~7. The ferric salt conditioner is less affected by the pH, and the pH range is 6~11. In the sludge with pH of 8~10, the hydrolysate with high solubility can be oxidized into flocs with low solubility. Therefore, when selecting inorganic salt flocculants, the specific pH of the dewatered sludge should be considered first. 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 sludge before conditioning sludge.
3、 Flocculant concentration.
The preparation concentration of flocculant not only affects the conditioning effect, but also affects the consumption of reagent and the sludge cake yield of the sludge dehydrator, of which the effect of organic polymer flocculant is more significant. Generally speaking, the lower the preparation concentration of organic polymer flocculant, the less the reagent consumption, and the better the conditioning effect. However, if the preparation concentration is too high or too low, the cake yield will be reduced. The conditioning effect of inorganic polymer flocculant is almost not affected by the preparation concentration. The preparation concentration of organic polymer conditioner is 0.05%~0.1%, the preparation concentration of ferric chloride is 10%, and the preparation concentration of aluminum salt is 4%~5%.
4、 The temperature of the mixed treatment solution.
The temperature of sludge directly affects the hydrolysis of flocculant. When the temperature is low, the hydrolysis will slow down. If the temperature is lower than 10 ℃, the flocculation effect of sludge dewatering machine will be significantly worse, and 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 thermal insulation of the sludge dehydrator, which should not be lower than 15 ℃, to minimize the heat loss in the process of sludge transportation.
