What kind of raw water pretreatment do you know?

In the first process, the dissolved air water is supplied by the dissolved air system, which adheres to the algae in the water through the bubbles in the water, floats it on the pool surface, and scrapes it off with the slag scraper Air flotation is a physical method to separate algae from water, which is very suitable for algae removal The effect of algae removal is good, and it will not have adverse effects, and the sensory index has been greatly improved The air flotation process needs to increase the return pressure water and dissolved gas system, increase the investment and operation cost, and increase the difficulty of operation and management The effect of air flotation is good, but it is not thorough If the algae is more than 100 million, other processes must be combined to ensure the water quality 2 Chemical algaecide chemical algaecide is to use disinfectant to kill algae in water, and to remove algae by subsequent precipitation and filtration process This method is simple and easy to operate However, disinfectants such as liquid LV, if they are added in large quantities, will produce three carcinogens, and there is also a risk of exceeding the standard of algal toxins Ozone preoxidation has a good auxiliary effect on algae removal In water plants with ozone activated carbon advanced treatment process, preoxidation is often used to replace the original liquid LV for algae removal Ozone kills algae by dissolving and splitting algae cells The algae toxins released after the destruction of algae can also be partially decomposed and removed by ozone At the same time, ozone plays a certain role in removing the odor produced by algae secretion The first pretreatment pretreatment process is generally used as an auxiliary measure for other processes In order to facilitate the removal of subsequent processes, it is necessary to reduce or change the properties of substances with more standards and higher indicators in advance Pretreatment technology is mainly biological pretreatment and strong oxidation treatment technology The application of biological pretreatment technology biological pretreatment is to remove ammonia nitrogen and some organic matters through biological action The research and application of biological pretreatment technology for micro polluted water source has a history of more than 30 years, and has been generally recognized by people As the pretreatment of micro polluted water source, the main advantages of biological treatment are: significant removal of NH3-N, NO2-N, AOC, organic matter, chroma, odor, TOC, turbidity The disadvantage is that it occupies a large area and the treatment effect is greatly affected by the water quality and temperature of the water source The application of pre oxidation technology mainly includes pre chlorination, pre ozone technology, permanganate pre oxidation technology and chlorine dioxide pre oxidation technology Prechlorination and prechlorination have been widely used in China It can be used to remove algae and degrade organics at a low cost However, the disinfection by-products generated by chlorine and organics in water are very harmful to human body Therefore, it is necessary to gradually cancel the use of prechlorination and prechlorination in micro polluted water sources Pre ozone pre ozone technology is mainly used to eliminate iron and manganese in groundwater, remove chromaticity and smell, degrade high molecular organic matter in water, and improve flocculation and clarification In the application of pre ozonation, the main purpose of pre ozonation is to assist coagulation If necessary, it is necessary to strengthen the removal of algae, chroma and organic pollutants The ozone dosage is generally 0.2-2.0mg/l Some studies have shown that the effect of controlling disinfection by-products by pre ozone is also relatively stable When pre ozone dosage is about 1.0mg/l (0.23mgo3 / mgdoc), the removal rate of trihalomethane precursor is about 23%, and the algae removal rate is as high as 47% in high algae stage In the process of ozone preoxidation, ozone does not reduce the content of organic matter in water to control the precursor of disinfection by-product, but mainly oxidizes the hydrophobic organic matter with high molecular weight Most of these organic compounds have aromatic structure or unsaturated double bond They are easy to be attacked and break down and become smaller They are converted into hydrophilic substances By changing the physical and chemical properties of organics in water and reducing the chlorination activity of organics in water, ozone pretreatment can control the generation of disinfection by-products However, it should be noted that when there is a high concentration of bromine ion in the raw water or when the ozone is added excessively, the Preoxidation of ozone will change bromine ion into bromate ion, and increase the concentration of bromotrihalomethane and bromoacetic acid in the water The pre ozone process occupies less land, the process effect is not affected by season, temperature and other factors, and the effect is stable However, ozone needs to be prepared on site, and the operation cost is high Permanganate preoxidation of potassium permanganate is a kind of strong oxidant, which can selectively interact with organic pollutants in water and destroy the unsaturated functional groups of organic matters It has been used to remove the smell and color of water since 1960s, with good effect In recent years, the permanganate composite agent has been developed, which has significant oxidation and coagulation aid, algae removal, odor removal, micro organic pollutants removal efficiency, and can also reduce the formation potential of trihalomethane The intermediate and new ecological components produced in the process of permanganate composite can enhance the removal of trace organic pollutants in water In addition, the new ecological manganese dioxide has adsorption effect on a variety of micro organic and inorganic pollutants in water, which can improve the removal effect of a variety of organic pollutants and heavy metals in water The application of chlorine dioxide preoxidation chlorine dioxide preoxidation is still relatively small, but chlorine dioxide preoxidation has a good removal effect on aromatic hydrocarbon compounds, which can control the formation of trihalomethane (THMs), reduce the generation of total organic halogen, and have a good decolorization effect on colored substances in water Pre oxidation with chlorine dioxide results in less organic by-products and less toxic effects The main inorganic by-products are chlorite and chlorate It has been reported that the adverse effects of chlorite and chlorite are mainly due to its strong oxidation and toxic effect on human nervous system, and long-term drinking can lead to anemia At present, the research in this area needs further study Chlorine dioxide also needs to be prepared on site, and according to different preparation methods, reaction conditions need to be strictly controlled to prevent explosion When chlorine dioxide is used for preoxidation to remove organic matter, iron and manganese, the dosage is 1-1.5mg/l, and the specific dosage needs to be determined according to the water quality The dosing concentration must be controlled below the explosion-proof concentration, and safety explosion-proof measures must be set Inert materials shall be used at the contact with chlorine dioxide; separate rooms shall be set for each agent, and measures shall be taken to exclude and contain or leak the agent Through the above comparison, it can be seen that the purpose of pre ozone process and biological pre-treatment process is different: pre ozone mainly degrades organics and removes chromaticity and odor through strong oxidation; while biological pre-treatment is to remove ammonia nitrogen and some organics through biological action In addition, the project is located in the Yellow River Estuary, where the temperature is low in winter The biological pretreatment method is adopted, which has poor effect on the treatment of organic matters, large land occupation and high cost for the thermal insulation of the pool body If it is not insulated, it is difficult for the bioreactor to discharge sludge, which affects its operation It is considered that the quality of raw water will be improved after the implementation of enhanced pollution control Biological pretreatment is not considered in this plan for the time being The use of pre chlorination will undoubtedly generate a large number of chlorination by-products, which will bring harm to the safety of drinking water Permanganate and ozone pre oxidation are relatively economic, and the removal effect of heavy metals is good, which can be considered together with the subsequent advanced treatment process 。