Process principle of coagulation sedimentation
The basic principle of coagulation method is to put coagulant into wastewater. Since coagulant is an electrolyte, it forms a micelle in wastewater, and neutralizes with colloidal substances in wastewater to form flocculent sedimentation. Coagulation sedimentation can not only remove the fine suspended particles with the particle size of 10-3~10-6 mm, but also remove the chromaticity, oil content, microorganisms, nitrogen and phosphorus and other eutrophic substances, heavy metals and organic substances.
Before coagulant is added to the wastewater, the colloid and fine suspended particles in the water are light in weight, and they make irregular Brownian motion due to the collision of thermal motion of water molecules. The particles have the same charge, and the electrostatic repulsion between them prevents particles from getting close to each other to form larger particles; Secondly, the charged colloidal particles and counter ions can hydrate with the surrounding water molecules to form a layer of hydration shell, which can prevent the polymerization of each colloid. The more charged a colloidal particle is, the greater its potential is; The more counter ions in the diffusion layer, the greater the hydration, and the thicker the hydration layer. Therefore, the thicker the diffusion layer, the stronger the stability.
After the coagulant is put into the wastewater, the colloid will destroy the stability of the particles (called destabilization) due to the reduction or elimination of the potential. The process of unstabilized particles gathering into larger particles is called agglutination. The unstabilized colloid can also form large particles, which is called flocculation. Different chemicals can destabilize, agglutinate or flocculate colloids in different ways. According to the mechanism, coagulation can be divided into four types: compressed electric double layer, adsorption electric neutralization, adsorption bridging and sediment netting.
In the process of coagulation and sedimentation treatment of wastewater, there are many factors that affect coagulation. Among them, there is the influence of water sample: for different water samples, the treatment effect of the same coagulant may vary greatly due to the different components of wastewater. There is also the influence of water temperature, which is mainly reflected in: a It affects the speed of chemical reaction of the agent in the alkalinity of water, and has a great influence on the coagulation of metal salts, because its hydrolysis is an endothermic reaction; B Affect the composition and quality of alum flower land. When the water temperature is low, the flocculent form is slow, the structure is loose, and the particles are fine; C When the water temperature is low, the viscosity of the water is large, and the intensity of Brownian motion is weakened, which is not conducive to the mutual aggregation of destabilized colloidal particles, and the flow shear force is also increased, affecting the growth of the flocs. This factor mainly affects the coagulation of metal salts, and has little influence on polymer coagulants.
Reprinted in: http://www.shenhuanwater.com
Keyword search: high-density micro vortex, wing diaphragm, V-shaped inclined plate, star shaped wing, small hole grid, small distance inclined plate, honeycomb inclined pipe, coagulation sedimentation, catch basin, water treatment
