Views: 210 Author: Site Editor Publish Time: 2024-01-05 Origin: Site
In this article, we will continue to introduce the dosing system, dosing amount calculation and dosing point selection, and continue to discuss dosing methods, flocculation influencing factors and dosing precautions in subsequent articles. Let us unveil the mystery of water treatment agents and contribute to protecting our water resources.
When designing a dosing system, the following key elements need to be considered to ensure the effectiveness and economy of the system:
1. Main equipment: including dissolving tanks, storage tanks, dosing agitators, dosing pumps and metering equipment, which are the basis of the dosing system.
2. Layout: It is recommended to build the dosing room, drug warehouse and disinfection chlorination room together. Such a layout is designed to simplify operation management, reduce labor intensity, and save investment costs.
3. Liquid storage tank design: The capacity design of the liquid storage tank should ensure at least 2 hours of liquid supply demand. If the storage time is too long, the volume of the liquid storage tank will be too large and occupy more space; if the time is too short, it will increase the complexity of operation. In the case of a small amount of dosing, it is possible to consider merging the liquid storage tank and the dissolving tank into one.
4. Storage capacity of the drug warehouse: The storage capacity of the drug warehouse should be determined according to the actual situation. If the supply of the agent is sufficient and the transportation is convenient, the maximum dosage can be stored for 20 to 30 days. On the contrary, if the drug supply conditions are poor, it is recommended to store a 60 to 80-day supply according to the maximum dosage.
5. Dosing location: If the dosing method is used before the pump, the dosing system should be as close to the pump room as possible to improve the dosing efficiency.
6. Dosing pipe design: The depth of the dosing pipe inserted into the water pipe is recommended to be 1/3 to 1/4 of the diameter of the water inlet pipe to ensure smooth dosing. At the same time, the direction of the dosing pipe should be consistent with the water flow direction of the water inlet pipe to avoid obstruction of dosing.
7. Material: All pipe fittings in the dosing system should be made of corrosion-resistant materials to adapt to the filling of different chemicals and extend the service life of the equipment.
Through the above design points, an efficient and economical dosing system can be constructed to meet the demand for accurate dosing of chemicals in the water treatment process.
There are no special precautions during the preparation process. Usually, the weight ratio concentration of the prepared solution is controlled between 10%-20%, and the actual dosage is about 200-300PPM (that is, 200-300mg of PAC is added per liter of water). Regarding the calculation of the set value in the dosing pump flow meter, please refer to the method for calculating the PAM dosage below.
1. The powdered product must be dissolved in clean water (such as tap water) before use to treat sewage in the form of an aqueous solution.
2. The water used for dissolution should be kept clean and at room temperature. Generally, it does not need to be heated. However, when the water temperature is below 5 degrees Celsius, the dissolution rate will slow down. If the water temperature exceeds 60 degrees Celsius, it will accelerate the degradation of the polymer and affect its use effect. In addition, strong acids, strong alkalis and high-salt water should not be used to prepare solutions.
3. It is recommended that the concentration of the polymer solution be controlled at 0.1% to 0.3%.
4. During the dissolution process, the reagent should be added slowly to the rotating water to avoid all-in-one addition, so as not to affect the dissolution rate or cause pipeline blockage due to insufficient dissolution.
5. The solution should be prepared before use. Long-term storage will cause degradation and affect the use effect. For a solution with a concentration of 0.1%, the non-anionic polymer aqueous solution should not be stored for more than one week, and the cationic polymer should not be stored for more than one day.
6. The stability of the solution is related to the concentration. The higher the concentration, the longer the storage time. However, high-concentration solutions should not be used directly for water treatment and need to be diluted before use.
7. Iron ions are catalysts that cause chemical degradation of polyacrylamide. Therefore, iron ion contamination should be avoided as much as possible during the preparation, transfer and storage of solutions. Equipment in contact with the solution should be made of stainless steel, plastic, fiberglass or carbon steel with resin coating on the surface.
8. When adding to wastewater, low-concentration addition should be used to ensure uniform mixing.
8. During use, the type of reagent and the optimal dosage need to be determined through experiments.
During sewage treatment or sludge treatment, after adding polyacrylamide (PAM), it is necessary to ensure that it is effectively mixed with sewage or sludge. The mixing time is usually controlled within 10-30 seconds and not more than 2 minutes. The amount of PAM used is closely related to factors such as the concentration, properties and treatment equipment of colloids and suspended solids in sewage or sludge. When treating sewage, the dosage is usually in the range of 3-10 PPM (i.e., 3-10 grams per ton of water). When treating sludge, the dosage is relatively large, and the optimal dosage needs to be determined through a large number of experiments.
Based on the optimal dosage concentration (PPM1, i.e., the concentration of PAM to be added) and the influent flow rate (t/h), as well as the concentration of the prepared polyacrylamide solution (PPM2, i.e., the prepared PAM concentration), the displayed value on the dosing pump flowmeter can be calculated (LPM) = influent flow rate (t/h)/60×PPM1/PPM2.
For example, if the water intake is 100t/h, the optimal dosage PPM1 is 10 ppm, and the preparation concentration is 2‰ (3Kg of medicine dissolved in 1.5t of water), then the dosing flow indication should be adjusted to 100/60×10/2=8.3 LPM.
Note: ppm means one part per million; in the unit of the dosing pump flow counting value, the LPM on the right means liters per minute, and the GPM on the left means gallons per minute (not used).
The setting of dosing point is flexible, and multiple points can be set or only one point can be set. However, it is necessary to ensure that the dosing point is located in the laminar flow area. At the same time, in order to improve the coagulation reaction effect and extend the residence time, the reaction tank should be designed as a baffle or set with a baffle.
In terms of operation simplification, one-time addition is the current traditional treatment method. If you want to save the amount of reagents and improve the coagulation effect, you can consider adding in batches, that is, adding a part of the coagulant before and after the mixing equipment. The effect of this method is better than one-time addition because the contact collision coagulation speed between particles of different particle sizes is greater than the collision coagulation speed between uniform particles; another method is to add all the
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