During urban piling or shield tunnel construction, a large amount of sewage is generated during shield tunneling, tunnel segment cleaning, grouting pipelines, mortar bucket cleaning, and underground flushing, especially when the water-rich stratum encounters spouting. Will produce a lot of highly concentrated muddy water. The sewage contains a large amount of kaolin slurry, cement, etc.; the ground application wastewater is mainly mortar mixing and washing. Sewage from vehicles, road washing, toilet flushing, etc. Anionic flocculant for piling mud.
According to the summary of long-term experiments, by adding the flocculant PAC and polyacrylamide PAM to the water sample without pre-treatment of the construction sewage taken from the well, the sewage can be completely treated and reused after stirring and sedimentation. Standards.
The role of polyacrylamide precipitant for piling shield mud is adsorption, bridging, net capture and electrical neutralization, and the role of polyaluminum chloride is to generate strong electrical neutralization reaction to colloids in water, adsorption bridging, etc. Some difficult-to-treat slurries even need to add quicklime calcium oxide for coagulation breaking or dilution treatment.
In the construction of piling shields, it is necessary to choose anionic polyacrylamide or cationic according to the characteristics of the mud. The mud in different regions should be selected by small-scale experiments to select the polyacrylamide products suitable for the customer's on-site use. At present, most mud treatments are treated with anionic polyacrylamide. Long-term experiments have concluded that the hydrolysis degree of anionic polyacrylamide suitable for mud treatment is between 25-40% and the molecular weight is between 12 million and 18 million. The mud flocculation treatment effect is good.
Anionic polyacrylamide is used in sewage treatment with less materials and high organic matter removal rate. It can effectively reduce the content of COD, BOD, SS and ammonia nitrogen in the sewage. It has a fast sedimentation rate and has a huge advantage over traditional inorganic flocculants. . The anionic polyacrylamide flocculant APAM has good water solubility, does not require high water temperature, and uses a small amount. It needs to be configured into a solution of 1-3‰, and the treatment of one ton of wastewater requires 7-15g of anionic polyacrylamide. Use organic flocculant anionic polyacrylamide APAM with inorganic flocculant polyaluminum chloride PAC, polyferric sulfate. Iron salt, etc., the effect is better and remarkable. Resistance reduction: APAM can reduce the frictional resistance between fluids. Adding a small amount of anionic polyacrylamide to the water can make the resistance reduction rate reach 50-80%. Adhesion: APAM can bond suspended particles through chemical, physical, and mechanical effects. Flocculation: Flocculation is an important function of anionic polyacrylamide*.
When using a centrifuge for sludge dewatering, PAM needs to be added, so why add PAM? First of all, there are two factors that affect the dewatering effect of centrifuge sludge. One is that it depends on the size of the suspended particles. The larger the particle size, the more collisions per unit time and unit volume, and the more conducive to the formation of larger particles. Flocs; the larger the particle size, the faster the sedimentation rate, and the more conducive to the sedimentation of suspended solids in wastewater. Therefore, large suspended solids account for a certain proportion, which can produce a good effect on small particles in wastewater and colloids that have not Adsorption increases the probability of contact and collision between particles, which is conducive to the formation of large alum flowers. The formation of large alum flowers in turn increases the chance of particle collisions. The two promote each other, resulting in the formation of larger particles, resulting in larger particles. Increase the sedimentation speed of suspended solids and increase the removal rate of sludge. According to this, after the sludge centrifuge runs, although the sedimentation load of the sedimentation tank is reduced, the sewage produced by the centrifuge contains a large number of fine particles, Anionic flocculant for piling mud.
It is very important that the polymer flocculant and the solvent are completely mixed. Add water to the designated position and adjust to a specific concentration. Continue stirring until the high molecular weight flocculation polymer is completely dissolved. Test method: The test procedure varies depending on the treatment method. But under normal conditions, the raw water to be treated is poured into a measuring cylinder and left to stand for one hour. If most of the sludge has settled, polyacrylamide can be used alone for treatment. First use representative anionic, non-ionic and cationic high molecular weight polyacrylamide to test. Choose polyacrylamide that can produce stable flocs. Distinguish whether the ion is an anion or a cation. Then compare the weak, medium, strong anions and cations to determine the best polyacrylamide type. After determining the appropriate polyacrylamide type, choose two to three products from the type. Determine the dosage of the best product to produce the best precipitation speed, transparency and dehydration effect. Effect analysis: The use effect of polyacrylamide PAM varies according to the state of the raw water being treated.