In recent years, with the expansion of the city and economic development, the management of the three wastes has lagged behind, and the quality of raw water in the waterworks has deteriorated. Seriously affecting the water quality of the water source, resulting in poor water effluent in the conventional water treatment process. The combination of potassium permanganate pretreatment, pre-filtration and powdered activated carbon combination process and conventional water treatment process combine to degrade organic matter and improve deodorization and decolorization. Ability, the effect is obvious. At the same time, this combination process has a significant reduction in turbidity and cost savings. Therefore, for the tap water plant, the combination of potassium permanganate and powdered activated carbon in the treatment of micro-polluted source water is the best cost-effective method.  Selection and dosage of potassium permanganate and powdered activated carbon (1) Potassium permanganate: The content is 99.3%. According to the water sample test, considering the reaction time of 30 to 35 minutes, considering the effect of potassium permanganate on the subsequent process, the optimum dosage is 0.25 to 0.40 mg/L. (2) Powdered activated carbon: As far as the existing process is concerned, the addition of powdered activated carbon before filtration can minimize the negative influence of potassium permanganate and eliminate the competition between coagulation and coagulation, but also lead to the contact time of powdered activated carbon. Short (on-site test is 5-8 min), and improper selection can easily penetrate the filter layer. Therefore, powdered activated carbon is selected according to the particle size of the filter material and the corresponding water quality. The corresponding technical index: mesh size is 120-150 mesh, iodine value ≥800 mg/L, methylene blue value ≥7-8, specific surface area 800-1200 m2/g. The dosage method is the wet pressure addition, and the sample test shows that when the CODMn is about 10 mg/L, the dosage is 20 m g/L. [How to regenerate after activated carbon failure?] After the activated carbon fails, regeneration is required. There are four methods for regeneration: (1) heating to about 100 degrees Celsius, causing the water to vaporize; melting at 800 degrees Celsius; and heating to 800-900 degrees Celsius for activation, so that the organic matter adsorbed on the activated carbon is oxidized and removed, so that the activated carbon is obtained regeneration. (2) Regeneration with steam purge. The low boiling point volatile adsorbate is substantially purged by steam purge. This method is simple and consumes less. (3) Regeneration with 10% acid or alkali to remove and remove the organic adsorbate. (4) The regeneration of the activated carbon is carried out using a solvent such as carbon tetrachloride, dichloromethane, acetone or the like. [Carbon Activated Carbon Recycling System Process] The regenerative furnace is discharged from the bottom of the furnace into a small quench tank. There are two separate pump suction pipes in the quench tank, each tank has several spouts and connecting lines, and the spouts are installed in the quench tank to keep the char flowing. The carbon slurry is sent from a quench tank to a regenerative char storage tank or washing tank. The two pumps used to pump the carbon slurry are diaphragm type mud pumps, which have a working capacity of 10 to 80 liters/min. The mud pump sends the carbon slurry to the storage tank or the cleaning tank through the conveying pipe. After washing, the washing tank is pressurized, and the charcoal-like regenerated charcoal is piped to the top of the carbon tower. At the same time, a certain amount of new carbon is added to the treatment system to supplement the charcoal lost during the regeneration process. The new charcoal needs to be washed in the washing tank before being placed in the charcoal tower. [Factors affecting the adsorption of activated carbon] The adsorption of activated carbon is a physical and chemical reaction process. The external factors and the bulk factors of activated carbon will affect its adsorption effect. The adsorption process and the principle of action involved in the treatment of activated carbon are complicated, so the influencing factors are also More. It is mainly related to the nature of activated carbon, the nature of pollutants in water, the process principle of activated carbon treatment, and the selected operating parameters and operating conditions. First, the nature of activated carbon Since the adsorption phenomenon occurs on the surface of the adsorbent, the specific surface area of ​​the adsorbent is one of the important factors affecting the adsorption. The larger the specific surface area, the better the adsorption performance. Because the adsorption process can be regarded as three stages, the internal diffusion has a great influence on the adsorption speed, so the micropore distribution of activated carbon is another important factor affecting the adsorption. In addition, the surface chemistry, polarity and charge of the activated carbon also affect the adsorption effect. Activated carbon for water treatment should have three requirements: large adsorption capacity, fast adsorption speed, and good mechanical strength. The adsorption capacity of activated carbon is related to the specific surface area of ​​activated carbon, and the specific surface area is large, the number of micropores is large, and the adsorbate adsorbed on the pore wall is more. The adsorption rate is mainly related to the particle size and pore distribution. The activated carbon for water treatment requires a transition hole (radius 20~1000A) to be developed, which is beneficial to the diffusion of the adsorption mass into the micropores. The smaller the particle size of activated carbon, the faster the adsorption speed, but the head loss should be increased, generally in the range of 8~30 mesh. The mechanical wear resistance of activated carbon directly affects the service life of activated carbon. Second, the nature of the adsorbate (solute or pollutant) The same activated carbon has great differences in the adsorption capacity of different pollutants. (1) Solubility The solubility of a substance of the same group decreases as the chain lengthens, and the adsorption capacity increases as the series of homologues rises or the molecular weight increases. The smaller the solubility, the easier it is to adsorb. For example, the order in which activated carbon adsorbs organic acids from water is increased by formic acid-acetic acid-propionic acid-butyric acid. (2) Molecular structure The size and chemical structure of the adsorbate molecules also have a large effect on adsorption. Because the adsorption rate is affected by the internal diffusion rate, the size of the adsorbate (solute) molecule is proportional to the pore size of the activated carbon, which is most favorable for adsorption. In homologues, molecules larger than molecules are easily adsorbed. The organic matter of the unsaturated bond is more soluble than the saturated one. Aromatic organics are easier to adsorb than aliphatic organics. (three) polarity Activated carbon can be regarded as a non-polar adsorbent, and its adsorption capacity for non-polar substances in water is greater than that of polar substances. (4) Adsorption sanctions (solute) When the concentration of the adsorbate is within a certain range, the adsorption capacity increases as the concentration increases. Therefore, the concentration of the adsorbate (solute) changes, and the adsorption capacity of the activated carbon for the adsorbate (solute) also changes. Third, the effect of solution pH The effect of pH on the adsorption should be considered in combination with the effects of activated carbon and adsorbate (solute). The pH of the solution controls the degree of dissociation of acidic or basic compounds. When the pH reaches a certain range, these compounds dissociate and affect the adsorption of these compounds. The pH of the solution also affects the solubility of the adsorbate (solute) and the charge of the adsorbate (solute) of the colloid. Since activated carbon can adsorb hydrogen and oxygen ions in water, it affects the adsorption of other ions. The effect of activated carbon adsorbing organic pollutants from water generally decreases with the increase of pH value of the solution. When the pH value is higher than 9.0, it is not easy to adsorb, and the lower the pH value, the better the effect. In practical applications, the optimum pH range is determined experimentally. Fourth, the effect of solution temperature Since the adsorption heat is small when the liquid phase is adsorbed, the influence of the solution temperature is small. Adsorption is an exothermic reaction. The heat of adsorption, that is, the total heat released by the activated carbon adsorption unit weight of the adsorbate (solute), in KJ/mol. The greater the heat of adsorption, the greater the effect of temperature on adsorption. On the other hand, temperature has an effect on the solubility of the substance and therefore also on the adsorption. When water is treated with activated carbon, the effect of temperature on adsorption is not significant.
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