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Views: 10 Author: Ryde Environment Publish Time: 2019-05-22 Origin: Ryde Environment
Sludge conditioner is usually used to improve the efficiency and effectiveness of sludge treatment. Sludge conditioner is needed in sludge dewatering process of plate-and-frame type filter press, centrifuge, belt filter press, multi disc screw press and so on.
So what factors should be considered in choosing sludge conditioner in practical application?
As far as the commonly used inorganic conditioners of aluminium and iron salts are concerned, the dosage of aluminium salts is larger, the floc density is smaller, the conditioning effect is poor, and the filter cloth will be blocked in the dehydration process.
Therefore, when choosing inorganic conditioner, iron salt should be used as far as possible; when using iron salt will bring many problems, aluminum salt should be considered again.
Compared with organic conditioner, inorganic conditioner has larger dosage, smaller floc particles, but higher floc strength.
Therefore, inorganic conditioner can be considered when vacuum filter and plate-frame filter press are used to dehydrate sludge. Compared with inorganic conditioner, the dosage of organic conditioner is smaller and the flocs formed are larger, but the strength of flocs is lower, and the flocs formed by organic conditioner are easier to crush than those formed by inorganic conditioner. And once the floc is destroyed, it is not easy to restore to its original state whether inorganic or organic conditioners are used.
Therefore, when using centrifugal dewaterer, belt filter press or multi disc screw press to dewatering sludge, organic conditioner can be considered. When using inorganic conditioner or organic conditioner is difficult to achieve the ideal conditioning effect, we can consider the combination of inorganic and organic conditioners, sometimes better conditioning effect can be achieved. For example, the combined use of lime and ferric trichloride can not only adjust the pH value, but also increase the porosity of sludge and promote sludge separation.
The types and dosage of conditioners for sludge with different properties are also quite different. For sludge with high organic content, the more effective conditioner is cationic organic macromolecule conditioner, and the higher the organic content, the more suitable to choose cationic organic macromolecule conditioner with higher degree of polymerization. Anionic organic macromolecule conditioner can be used for sludge mainly composed of inorganic substances. Different sludge properties directly affect the conditioning effect: sludge in primary clarifier is easier to dehydrate, while sludge and residual activated sludge are more difficult to dehydrate, and the dewatering performance of mixed sludge is between the two. In order to achieve a certain conditioning effect, there are significant differences in the number of conditioners needed.
Generally speaking, the more difficult it is to dehydrate the sludge, the larger the dosage of conditioning agent and the smaller the sludge particles will lead to the increase of the consumption of conditioning agent, the higher the organic content and alkalinity of sludge, and the increase of the dosage of conditioning agent.
In addition, the sludge solid content also affects the dosage of conditioner. The higher the sludge solid content, the larger the dosage of conditioner.
The temperature of sludge directly affects the hydrolysis of inorganic salt conditioners. When the temperature is low, the hydrolysis will slow down.
If the temperature is lower than 10oC, the conditioning effect will become worse. The conditioning effect can be improved by prolonging the conditioning time properly. When using organic macromolecule conditioner, if the temperature of mother liquor or tap water is too low or sludge temperature is too low, the dynamic viscosity of water and the viscosity of macromolecule conditioner solution itself will become larger, which is not conducive to the uniformity of dilution and mixing, thus affecting the effect of sludge conditioning and dewatering.
Therefore, when the temperature is low in winter, attention should be paid to the thermal insulation of sludge transportation system (the temperature of sludge discharged from sewage treatment system is generally no less than 15oC), so as to minimize the heat loss in the process of sludge transportation. When necessary, heating the dilution tank of organic polymer conditioner or prolonging the mixing dissolution time and increasing the stirring intensity can be adopted to improve the dissolution conditions.
