In order to reduce the moisture content of the sludge to below 55%, it is necessary to select the appropriate agent during the sludge conditioning process. Here are some effective agents and their mechanisms of action:
A, inorganic coagulant
Inorganic coagulants such as iron salts (especially polyferric chloride FeCl₃) and aluminum salts are commonly used in sludge conditioning agents. Through the compression of double electric layer, charge neutralization, adsorption bridge and net trapping, the sludge colloid is destabilized to form a larger floc, thereby improving the sedimentation and dewatering performance of the sludge.
Iron salt: is currently the most effective treatment of organic sludge, the most widely used agent. It can not only react with the bicarbonate alkalinity in the sludge to form hydroxide as a coagulant, but also neutralize the negatively charged sludge solids and make the sludge aggregate and destabilize. However, it should be noted that iron salt is highly corrosive, and solid products are easy to absorb water and delix, which is not easy to preserve.
Lime: used with iron salt, it has a good effect on sludge conditioning. Lime controls the pH of the sludge, reduces odors and sterilizes it. At the same time, CaCO₃ formed by the reaction of lime and bicarbonate in sludge can provide a granular structure, increase the porosity of sludge and reduce the compressibility of sludge.
Two, organic polymer coagulant
Organic polymer coagulants, such as polyacrylamide (PAM), are also commonly used in sludge conditioning agents. They can effectively form large floc resistant to shear action in the process of press filtration, and are suitable for mechanical dewatering of sewage sludge.
PAM: both coagulant and coagulant aid, with the function of net sweep. It can react with negatively charged dissolved matter to produce insoluble salt, and the sludge water after conditioning and dehydration is colorless and transparent, and the sludge water separation effect is good. The amount of PAM is usually 0.1%0.5% of the dry solid weight of the sludge, and the dosage should be 0.1% to 0.3%.
Three. New sludge conditioner
In addition to the traditional inorganic coagulants and organic polymer coagulants, there are some new sludge conditioning agents such as SJC-08, etc., which can also reduce the sludge moisture content to below 55%. These new conditioning agents usually contain sludge wall breaking agents, sludge stripping agents, sludge surface structure modifiers and other components, which can achieve deep and rapid wall breaking, release free water and interstitial water in the sludge, so as to improve the dewatering performance of the sludge.
Four, precautions
In the selection of conditioning agents, the characteristics of sludge and treatment objectives should be fully considered. Different sludge composition and properties may affect the selection and dosage of the agent.
The dosage of the drug should be controlled within a reasonable range. Too little dosage may not achieve the desired effect, while too much dosage may increase treatment costs and have adverse effects.
The sludge after conditioning should be dehydrated in time to avoid the sludge re-absorbing water or other adverse changes.
In summary, in order to reduce the moisture content of the sludge to below 55%, it is necessary to choose the appropriate sludge conditioning agent and control the reasonable dosage. At the same time, it is also necessary to comprehensively consider and adjust the characteristics of sludge and treatment objectives.