Polyacrylamide is widely used in sludge dewatering of water treatment, and it is the most commonly used dehydrating agent. However, some water treatment plants find that when polyacrylamide is used for sludge dewatering, the sludge will stick to the filter cloth, block the filter cloth, the water quality is unclear, and the viscosity of water will increase. Why do these phenomena occur? Gongyi Filter Industry Co.,Ltd will answer the question.

The final link of sewage treatment is sludge dewatering. This process is to add polyacrylamide to the turbid mud, so that the sludge in the mud can quickly flocculate and agglomerate. When passing through the filter cloth of belt filter press, most of the water seeps out for reuse or discharge. The dewatered sludge can be directly buried or mixed with coal combustion. In this process, sludge sticking to filter cloth or blocking may be caused by the following reasons:

1. Molecular weight of polyacrylamide does not match filter press

When the molecular weight of cationic polyacrylamide is too high, the viscosity of stirred sludge will increase. When the filter cloth is used for pressure filtration, the too viscous sludge is easy to block the seepage hole of the filter cloth, resulting in poor desliming effect of the filter cloth.  Different types of polyacrylamide required by different sludge sources and different filter presses are different. Generally, low molecular weight amide with ionic degree less than 30 is more suitable for crawler filter presses. If centrifuge type desliming equipment is used, amide with high molecular weight should be selected, and flocs are more resistant to shear. Amide with ionic degree of 30 and 40 is more suitable for stacked screw centrifuges, and amide with ionic degree of 30 and 40 is more suitable for high-speed centrifuges In addition, the plate and frame filter press with 20 and 30 degrees of ion is the most suitable.

2. The dosage of polyacrylamide is too much or the agent is not dissolved

If the dosage of polyacrylamide is too large, there will be too much colloidal viscosity, which will also cause the mud to become viscous. Moreover, the partially dissolved polyacrylamide will produce colloidal substance, which can not be dissolved after adding mud, resulting in the sticky substance sticking to the filter cloth during filter pressing.

Therefore, it is suggested that the dosage of polyacrylamide should be based on the test results and should not be increased or decreased at will. In addition, when preparing polyacrylamide solution, first add water to the mixing drum, then start the mixer, and slowly and evenly add polyacrylamide along the vortex formed by mixing. According to the volume of the mixing drum, add the dosage of the test, and continue to stir for not less than 30 minutes to dissolve it. After use, the reagent dissolving mixing bucket needs to be cleaned regularly, and the undissolved medicine block at the bottom should be treated in time.

3. The pressure of filter cloth washing water is too low

As the main method of cleaning filter cloth, the pressure of cleaning water is very important. If the water pressure is too low, the excess sludge on the filter cloth is not cleaned, and the water permeability will be reduced. At the same time, the sludge is more likely to stick to the filter cloth, which is difficult to clean, and the solid content of the sludge cake will be reduced. In the long run, the filter cloth will be seriously blocked, which can not ensure the normal operation of sludge dewatering. Therefore, the water treatment plant should regularly check the operation of sludge dewatering equipment, and timely deal with the problems found.