1. Introduction to high-difficulty wastewater
High-difficulty wastewater usually refers to industrial wastewater with complex ingredients, high organic content, high toxicity, poor biodegradability, and extremely difficult to treat. These wastewaters often contain a variety of pollutants that are difficult to degrade, posing a serious threat to the environment and human health.
2. Characteristics of high-difficulty wastewater sources
Chemical industry: such as petrochemicals, fine chemicals, pharmaceutical chemicals, etc., will produce a large amount of high-difficulty wastewater during the production process. For example, wastewater discharged in the process of synthetic dyes, pesticides, pharmaceutical intermediates, etc. contains various complex organic compounds, heavy metal ions, toxic and harmful substances, etc.
Electronic industry: In the process of semiconductor manufacturing, printed circuit board production, etc., wastewater containing high concentrations of heavy metal ions (such as copper, nickel, lead, cadmium, etc.) and organic matter (such as photoresist, cleaning agent, etc.) will be generated.
Electroplating industry: Various chemical agents used in the electroplating process, such as chromic acid, cyanide, heavy metal salts, etc., will cause the wastewater to contain high concentrations of heavy metal ions, cyanide and other toxic and harmful substances.
Printing and dyeing industry: The wastewater generated by dyeing, printing and other processes contains a large amount of organic matter such as dyes and additives that are difficult to degrade, with high chromaticity and poor biodegradability.
Features:
Complex composition: High-difficulty wastewater often contains many different types of pollutants, including organic matter, inorganic matter, heavy metal ions, toxic and harmful substances, etc., and the composition is extremely complex.
High organic content: Chemical oxygen demand (COD) and biochemical oxygen demand (BOD) are usually high, and contain a large amount of organic matter that is difficult to biodegrade.
High toxicity: It may contain toxic and harmful substances such as heavy metal ions, cyanide, pesticides, and pharmaceutical intermediates, which are extremely harmful to aquatic organisms and human health.
Poor biodegradability: Due to the complex structure and high stability of organic matter in wastewater, it is difficult to be degraded by microorganisms, resulting in poor biodegradability.
Large fluctuations in pH value: Different production processes will produce acidic or alkaline wastewater, and the pH value varies widely.
High water temperature: Some production processes will produce high-temperature wastewater, which needs to be cooled.
3. Process flow of high-difficulty wastewater treatment
Pretreatment stage:
Grate slag removal: remove larger solid impurities in wastewater, such as branches, plastic bags, fibers, etc., to prevent clogging of subsequent treatment equipment.
Regulating tank homogenization: adjust the water volume and water quality of wastewater to keep it stable within a certain range so that subsequent treatment equipment can operate normally.
Neutralization treatment: For acidic or alkaline wastewater, neutralization treatment is carried out to adjust the pH value of wastewater to neutral or near neutral.
Sedimentation treatment: remove suspended matter and some organic matter in wastewater through natural sedimentation or coagulation sedimentation.
Advanced oxidation pretreatment: For high-difficulty wastewater with poor biodegradability, advanced oxidation technology (such as ozone oxidation, Fenton oxidation, photocatalytic oxidation, etc.) can be used for pretreatment to decompose difficult-to-degrade organic matter into small molecular substances and improve the biodegradability of wastewater.
Main treatment stage:
Aerobic biological treatment: use aerobic microorganisms to decompose organic matter in wastewater into harmless substances such as carbon dioxide and water. For high-difficulty wastewater with poor biodegradability, special aerobic biological treatment processes can be used, such as biological fluidized bed, membrane bioreactor, etc.
Anaerobic biological treatment: For high-concentration high-difficulty wastewater, anaerobic biological treatment can be carried out first to reduce the COD content of the wastewater, and then aerobic biological treatment can be carried out.
Adsorption treatment: Adsorbents such as activated carbon and zeolite are used to adsorb organic matter and heavy metal ions in wastewater.
Membrane separation treatment: Membrane technologies such as ultrafiltration, reverse osmosis, and nanofiltration can effectively remove organic matter, heavy metal ions and salts in wastewater.
Ion exchange treatment: Ion exchange resin is used to remove heavy metal ions in wastewater.
Filtration treatment: Wastewater after biological treatment and physical and chemical treatment may still contain a small amount of suspended matter and residual organic matter. Filtration treatment, such as sand filtration, activated carbon filtration, etc., can be used to further remove impurities in wastewater.
Disinfection treatment: If the treated wastewater needs to be discharged or reused, disinfection treatment is carried out to kill microorganisms such as bacteria and viruses in the wastewater. Commonly used disinfection methods include ultraviolet disinfection, chlorine dioxide disinfection, ozone disinfection, etc.
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