What is semi-countercurrent regeneration?
Semi-countercurrent regeneration is a four-bed five-tower desalination system. The process flow of ion exchange treatment is: positive bed-decarburization-negative bed-positive bed-negative bed. Both anion and cation resins are strong alkali and strong acid exchange resins. The first cation bed and the anion bed contain more resin, which can basically remove all ions; the second cation bed and the anion bed have less resin, which is used for refinement. During regeneration, the acid and alkali regenerating liquids enter the second anion and cation beds respectively, and then are connected in series to the first anion and cation beds for regeneration. Each exchanger adopts downstream regeneration, which is easy to operate. This method has the meaning of layered regeneration. When the resin fails, the arrangement of the cation bed is: Ca type-Mg type-Na type-H type. When regeneration is carried out in the opposite direction, that is, H type-Na type- Mg type-Ca type, this kind of regeneration efficiency is higher, because H replaces Na, which can then replace Ca and Mg. Therefore, the burden of replacement by H is greatly reduced, and the similar benefits of countercurrent regeneration are obtained, so it is called semi-countercurrent regeneration. This method is suitable for desalination water treatment with high salt content. The investment is larger and the equipment is larger.
What is suspended matter in water?
Suspended substances in water are particles with a particle diameter of about 0.0001mm or more. Visible to the naked eye. These particles are mainly composed of silt, soil, protozoa, algae, bacteria, viruses, and high-molecular organic matter. They are often suspended in water streams. The erosion of water is also caused by such substances. . These particles are very unstable and can be removed by precipitation and filtration. When the water is standing still, heavy particles (mainly inorganic substances such as sand and clay) will sink. Light particles (mainly a class of organic compounds of plants and animals and their remains) will float on the water and can be removed by separation methods such as filtration. Suspended matter is the main source of turbidity, color and smell. They are also unstable in the water, and often change with seasons and regions.
What are colloidal substances in water?
Colloidal substances in water refer to particles with a diameter between 0.0001 and 0.000001mm. A colloid is a collection of many molecules and ions. The organic mineral colloids in natural water are mainly compounds of iron, aluminum and silicon. The organic colloidal substances in the water are mainly humus produced by the rot and decomposition of the limbs of plants or animals. Among them, lake water has the most humus content, so the water is often yellow-green or brown.
Since the particles of colloidal substances are small, light in weight, and have a large surface area per unit volume, their surface has a large adsorption capacity and often adsorbs a large amount of ions and is charged. The colloids of the same kind repel each other because of the charges of the same sex. The colloids cannot bond to each other in water and are in a stable state. Therefore, colloidal particles cannot be removed by self-sedimentation by gravity. Generally, chemicals are added to the water to destabilize the colloidal particles so that the colloidal particles increase and settle to be removed.
What are dissolved substances in water?
Dissolved substances in water are tiny particles with a diameter less than or equal to 0.000001mm. Mainly various ions and gases that are dissolved in water and exist as low-molecular dissolved salts. Dissolved substances can be removed by methods such as ion exchange or desalination.
What are organic substances in water?
The organic matter in water mainly refers to the pollutants of humic acid and fulvic acid polycarboxylic acid compounds, domestic sewage and industrial wastewater. Among them, the former is a weak organic acid with multifunctional aromatic macromolecules, which accounts for more than 95% of the organic substances dissolved in water. Humus is the product of aquatic life activities. Domestic sewage is mainly human excrement and garbage waste. The organic matter in various industrial wastewater includes animal and plant fibers, oils, sugars, dyes, organic acids, various organic synthetic industrial products, and organic raw materials. These organic matter pollute the water body and worsen the water quality.
What harm does organic matter have to water bodies?
The organic water in the water has a common feature, that is, to carry out biological oxidation and decomposition, it needs to consume the dissolved oxygen in the water, which leads to the lack of oxygen in the water. At the same time, spoilage and fermentation will occur, causing bacteria to grow, deteriorating water quality, and destroying water bodies; the organic pollution of industrial water will also reduce the quality of products. Organic matter is one of the main causes of water pollution.