What are the common treatment processes of chemical wastewater?
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Update time : 2023-03-24 10:56:16
In the process of chemical industry development, wastewater treatment has always been a hot issue. The ingredients are increasingly complex and difficult to explain.
Therefore, it is difficult to achieve effective treatment of chemical wastewater by using only one wastewater treatment technology. In the future treatment of chemical wastewater, the mode of combining various wastewater treatment technologies should be gradually adopted, so as to improve the wastewater treatment effect as far as possible and better solve the problem of environmental pollution caused by chemical wastewater.
In addition, chemical enterprises should be clear about the characteristics of their own wastewater, scientific selection of chemical wastewater treatment technology and program, so that it can play a maximum role.
01 Characteristics of chemical industry wastewater
In the process of chemical industry development, chemical related raw materials are mainly composed of compounds similar to solvents. These compounds have certain complexity and diversity, which makes it relatively difficult to deal with compounds.
In chemical wastewater, the amount of toxic substances also shows an increasing phenomenon, including nitrocompounds and halogen compounds and other toxic substances, these chemical raw materials in the water after effective decomposition, can form substances containing toxic properties, these substances have a serious threat to human health.
02 Common processing process
Physical method
Physical method refers to a treatment technology that separates the water contained in suspended solids by mechanical and physical action. It is usually used to remove floating solids in wastewater, and can also remove suspended solids, sand and oil contained in wastewater.
At present, there are three kinds of physical chemical wastewater treatment methods widely used in the chemical industry:
Gravity precipitation method;
Gravity precipitation method is mainly based on the density difference between suspended particles in water and water, which depends on gravity field to precipitate them, so as to achieve the purpose of solid-liquid separation.
Filtration method;
The filtration rule is to remove insoluble impurities contained in the water through the filter layer, usually relying on filters and microporous tubes and other equipment to reduce the suspended matter contained in the water.
Air flotation method;
Gas flotation method refers to the adhesion of suspended matter in water with the help of highly dispersed tiny bubbles, and the effective separation of water and suspended matter by density difference. This treatment technology is generally applied to the separation and treatment of oil and hydrophobic fine suspended matter.
The physical method is relatively simple in the specific process, but it is difficult to separate and treat the soluble components. At present, magnetic separation and membrane separation are the main physical technologies used in chemical wastewater treatment.
Chemical method
Chemical treatment is through chemical reaction and mass transfer to separate, remove the dissolved, colloidal pollutants in the wastewater or transform them into harmless substances wastewater treatment method. Compared with other sewage treatment methods, chemical method is more complex and expensive, but it can really achieve the purpose of removing pollutants.
Chemical methods can also be subdivided into neutralization, coagulation, REDOX, electrochemical and other methods.
The PH value of chemical wastewater can be reduced to neutral level by the chemical reaction of neutralization method, which is also used in the pretreatment of wastewater. Even if coagulant is put into the wastewater, the coagulant can be used as an electrolyte to form colloids of some substances in the wastewater and gradually form flocs settling. Through REDOX reaction and electrolytic reduction reaction can be some highly toxic substances into slightly toxic or non-toxic substances, to achieve the purpose of pollution control.
Physicochemical method
Physical chemistry method refers to the comprehensive analysis of physical chemistry principle, combined with chemical separation to implement a method of wastewater treatment.
In general, physical and chemical methods mainly include ion exchange method, adsorption method, extraction method and separation method. This kind of wastewater treatment method can effectively remove fine suspended matter and dissolved organic matter in wastewater, but it is only suitable for the separation and treatment of certain substances, and it is difficult to be applied in a wide range. At the same time, the cost of this treatment process is high, and it is likely to lead to secondary pollution.
Ion exchange method is based on the differences in affinity of chemical bonds to exchange the ion exchanger and water ions to achieve effective purification of wastewater. Extraction method is to effectively extract non-polar organic matter in wastewater and complete wastewater purification by putting extractant into wastewater and adopting similarity and compatibility principle. Adsorption method refers to the adsorption of organic pollutants contained in chemical wastewater with the help of porous media, so as to achieve the effect of purifying wastewater.
Biological method
Biological method refers to a treatment method that gives full play to the metabolic role of microorganisms to achieve effective decomposition of organic pollutants contained in chemical wastewater and smoothly remove them.
In general, biological treatment of chemical wastewater mainly includes two kinds, aerobic biological treatment; Anaerobic biological treatment.
Aerobic biological treatment methods mainly include biofilm method and activated sludge method, the former mainly through biofilm to achieve effective adsorption and oxidation of organic matter, in the process of direct contact with chemical wastewater to complete wastewater treatment; The latter carries out wastewater treatment by suspending microorganisms to promote the effective degradation of organic matter in wastewater.
Some studies have found that the application of aerobic biological adsorption method in the treatment of high concentration organic wastewater has a remarkable effect, which can increase the COD removal rate in wastewater to 99%.
Anaerobic biological treatment refers to a method that realizes the effective removal of pollutants contained in wastewater by means of the degradation of anaerobic microorganisms. Studies have found that the application of biological method in the wastewater treatment process of printing and dyeing industry can obtain 99.6% COD removal rate, the application effect is very significant.
Microelectrolysis method for pollution treatment of chemical wastewater
With the development of modernization of science and technology in our country, the microelectrolysis treatment method has become a newly arisen sewage treatment method. It is an ideal process for treating high concentration organic wastewater, also known as internal electrolysis.
This method can use the micro-electrolytic material filled in the wastewater to generate 1.2V potential difference for electrolytic treatment of wastewater without electricity, so as to achieve the purpose of degrading organic pollutants. Its reaction rate is very fast, the treatment of general industrial wastewater only takes a few hours, and the effect of decontamination is also very ideal, suitable for various types of chemical wastewater treatment, is a relatively ideal chemical wastewater pollution treatment way.
03 new chemical wastewater treatment process
With the continuous development and progress of chemical wastewater treatment technology, a variety of new treatment technology began to emerge.
High temperature incineration
In foreign countries, some chemical plants choose to implement oxidation decomposition of high-concentration organic wastewater through high-temperature incineration, so that it can be successfully converted into water and carbon dioxide. This wastewater treatment technology is conducive to reducing pollution, but its cost is extremely high, so far it cannot be popularized on a large scale.
Constructed wetland
Constructed wetland, as a new method and technology in chemical wastewater treatment, has the characteristics of low energy consumption, and can greatly reduce the cost, and can play a certain role in the field of environmental science. Some studies have found that the method of constructed wetland can realize the effective exposure treatment of distillery wastewater, the COD removal rate can reach 60%, and is conducive to improving the nitrogen and PH value of wastewater and other related indicators.
These new technologies usually have outstanding characteristics, and they have been tried and applied in the actual chemical wastewater treatment, and become a significant development trend of chemical wastewater treatment technology in the future.
The diversity of pollutants in chemical wastewater determines that it is a developing trend to adopt a variety of processes for wastewater treatment. With the improvement of environmental standards, waste water treatment must reduce energy consumption and cost, improve the treatment efficiency in order to meet the requirements of environmental protection, while ensuring the competitiveness of enterprises and economic benefits.
