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Basic Characteristics and Treatment Methods of Chemical Wastewater
2019-1-31
Source:Publication
Clicks:  7105        作者:未知
  • Characteristics of Chemical Wastewater and Principles of Wastewater Treatment

    With the rapid development of economy, the pollution of the environment in the production process of chemical products is aggravated, and the harm to human health is becoming more and more widespread and serious. Especially the organic substances discharged from the production process of fine chemical products (such as pharmaceuticals, dyes, daily chemicals, etc.) are mostly complex, toxic, harmful and biodegradable substances. Therefore, it is difficult to treat chemical wastewater.

    The basic characteristics of chemical wastewater are extremely high COD, high salinity and toxicity to microorganisms. It is a typical refractory wastewater. It is the research focus and hotspot of water treatment technology at present. The characteristics of chemical wastewater are analyzed as follows:

    (1) The composition of water quality is complex and there are many by-products. The raw materials are usually solvents or ring-shaped compounds, which increase the difficulty of wastewater treatment.

    (2) The high content of pollutants in wastewater is due to incomplete reactions of raw materials and the introduction of a large number of solvent media into the wastewater system.

    (3) There are many toxic and harmful substances. Many organic pollutants in fine chemical wastewater are toxic and harmful to microorganisms, such as halogen compounds, nitro compounds, dispersants or surfactants with bactericidal effect, etc.

    (4) There are many biodegradable substances, B is lower than C, and biodegradability is poor.

    (5) High chroma of wastewater.

    Treatment of Chemical Wastewater

    Wastewater treatment technology has been developed for more than 100 years. With the development of social economy and the improvement of living standards, the types and amount of pollutants in wastewater are increasing. With the development of science and technology, sewage treatment technology has changed rapidly. At the same time, the old sewage treatment technology has been constantly innovated and developed. Especially, the pollutants in chemical wastewater are various, and it is often impossible to remove all the pollutants in the wastewater by one process. It is very difficult to treat chemical wastewater to discharge standard by physicochemical process, and the operation cost is high. Chemical wastewater contains more refractory organic matter, and its biodegradability is poor. Moreover, the quantity and quality of chemical wastewater vary greatly, so the effect of treating chemical wastewater directly by biochemical method is not ideal.

    In view of the characteristics of chemical wastewater treatment, we think that appropriate pretreatment methods should be adopted according to the actual wastewater quality, such as flocculation, internal electrolysis, electrolysis, adsorption, photocatalytic oxidation, etc., to destroy the refractory organic matter in wastewater and improve the biodegradability of wastewater; and then combined biochemical methods, such as SBR, contact oxidation process, A/O process, should be used to treat chemical wastewater. Do deep processing.

    At present, the domestic research on chemical wastewater treatment process tends to adopt a combination of various methods. For example, medical wastewater is treated by internal electric bait coagulation sedimentation-anaerobic-aerobic process, organic chemical wastewater is treated by macroporous adsorption resin adsorption and anaerobic-aerobic biological treatment-flocculation sedimentation process, ephedrine wastewater is treated by flocculation-electric bait method, organic pollutants are removed by ozone-biological activated carbon process, photocatalytic oxidation-internal electric bait-sBR is adopted. Good results have been achieved in the treatment of highly concentrated chemical wastewater by combined methods. Chemical wastewater is complex in composition and varies greatly in water quality and quantity. With the stricter and stricter requirements of the state for its treatment to meet the standards, it is difficult for people to get a good treatment effect by using a method. Various combined treatment technologies are used to treat chemical wastewater according to the actual situation. In order to take the advantages of simplicity and simplicity, the optimization of processing system is realized.

    Water pollution index

    Water pollution index is a numerical indicator to measure the degree of water pollution, and it is also an important basis to control the operation status of water treatment equipment. Among them, there are 8 most commonly used water pollution indicators:

    Biochemical Oxygen Demand (BOD): The amount of free oxygen consumed by aerobic microorganisms in degrading organic matter per liter of water in a certain number of days under saturated oxygen condition at 20 C. The standard time for determining BOD is usually 5 days, expressed as BOD5.

    Chemical oxygen demand (COD): The equivalent amount of oxygen consumed by oxidizing organic matter to hydrogen peroxide and carbon dioxide with a strong oxidant. Commonly used oxidants are potassium dichromate or potassium permanganate, which are expressed as CODCr or COD or COMn (also known as oxygen consumption, or OC) in mg/L, respectively.

    Total Oxygen Demand (TOD): When organic matter is completely oxidized, the amount of oxygen consumed by C, H, N and S is oxidized to CO 2, H 2, NO and SO2 in mg/L, respectively.

    Total Organic Carbon (TOC): Indicates the total carbon content of organic pollutants in water, expressed in terms of carbon content, in mg/L.

    Suspended solids (SS): Substances intercepted from filter membranes or filter papers after filtration of water samples in units of mg/L.

    PH: Indicates the acidity and alkalinity of sewage.

    Toxic substances: indicating the content of harmful substances in water, such as cyanide, arsenide, mercury, cadmium, chromium and lead, in mg/L.

    Number of Escherichia coli: The number of Escherichia coli per liter of water, in units of 1/L.

    Classification of wastewater treatment methods

    According to the characteristics of different pollutants, different wastewater treatment methods have been developed, especially the treatment of chemical wastewater. These methods can be divided into four categories according to their working principles: physical treatment, chemical treatment, material chemical treatment and biological treatment.
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