When treating sewage and sludge using a sludge dewatering machine, flocculants are often required to achieve optimal treatment results. When selecting an appropriate flocculant, consider the following four key factors.
Sludge Properties
For sludge with a high organic content, cationic flocculants are more effective. The higher the organic content, the more effective a cationic flocculant with a higher degree of polymerization. For sludge primarily composed of inorganic matter, anionic flocculants can be considered. Sludge properties directly affect the conditioning effect. Scum and excess activated sludge are more difficult to dewater, while mixed sludge has an intermediate dewatering performance.
Generally speaking, the more difficult the sludge to dewater, the higher the flocculant dosage. Finer sludge particles lead to increased flocculant consumption. High organic content and alkalinity in the sludge also lead to increased flocculant dosage. Furthermore, the sludge solids content also influences the flocculant dosage. Generally, the higher the sludge solids content, the greater the flocculant dosage required when using a sludge dewatering machine.
Sludge pH
Sludge pH determines the form of hydrolysis products, and the same flocculant will have significantly different treatment effects on sludge with different pH values. The hydrolysis reaction of aluminum salts is significantly affected by pH, with the optimal pH range for their coagulation reaction being 5-7. Ferric salt conditioning agents are less affected by pH, with an optimal pH range of 6-11. Ferrous salts, with their more soluble hydrolysis products, can be hydrogenated into less soluble flocs in sludge with a pH of 8-10.
Therefore, when selecting an inorganic salt flocculant, the specific pH of the dewatered sludge should be considered first.
Flocculant Concentration
The flocculant concentration not only affects the conditioning effect, but also affects chemical consumption and the sludge dewatering machine cake yield. Organic polymer flocculants have a more significant impact. Generally speaking, the lower the organic polymer flocculant concentration, the lower the chemical consumption and the better the conditioning effect. However, excessively high or low concentrations will reduce sludge cake yield, while the conditioning effect of inorganic polymer flocculants is virtually unaffected by concentration. The ideal concentration for organic polymer flocculants is 0.05% to 0.1%, 10% for ferric chloride, and 4% to 5% for aluminum salts.
Mixed treatment fluid temperature
The sludge temperature directly affects the hydrolysis of the flocculant by appropriately extending the flocculation time. Low temperatures slow the hydrolysis process. If the temperature falls below 10°C, the flocculation effect of the sludge dewatering machine will be significantly reduced. In winter, when temperatures are low, it's important to maintain the sludge dewatering machine at a minimum of 15°C to minimize heat loss during sludge transportation.