A breakdown of 14 industrial wastewater treatment methods

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1、Oily wastewater

Oily wastewater mainly comes from petroleum, petrochemical, iron and steel, coking, gas generation station, machining and other industrial sectors. Wastewater oil pollutants, in addition to heavy tar relative density of 1.1 or more, the rest of the relative density is less than 1.

Oil substances in wastewater usually exist in three states:

(1) Floating oil, oil droplet particle size greater than 100μm, easy to separate from the wastewater;

(2) Dispersed oil. Oil droplet particle size between 10 a 100μm, pleading floating in the water;

(3) emulsified oil, oil droplet particle size less than 10μm, not easy to separate from the wastewater.

As the oil concentration in wastewater discharged from different industrial sectors varies greatly, such as oil refining process produces wastewater with oil content of about 150 to 1000 mg/L, coking wastewater with tar content of about 500 to 800 mg/L, and the tar content in wastewater discharged from the gas generating station can be up to 2,000 to 3,000 mg/L. Therefore, the treatment of oil-containing wastewater should be utilized firstly in the form of oil separator tanks, which can recycle floating or heavy oil, with a treatment efficiency of 60%. Heavy oil, processing efficiency of 60% to 80%, the oil content in the effluent is about 100-200mg/L; emulsified and dispersed oil in the wastewater is more difficult to deal with, so it should be prevented or mitigated emulsification phenomenon. One of the methods is to pay attention to reduce the emulsification of oil in the wastewater during the production process; the second is to minimize the number of times the wastewater is lifted by pumps during the treatment process to avoid increasing the degree of emulsification. Treatment methods are usually used air flotation and emulsion breaking method.

3、Hg-containing wastewater

Mercury-containing wastewater mainly comes from non-ferrous metal smelters, chemical factories, pesticide factories, paper mills, dyestuff factories and thermal instrumentation factories. Methods to remove inorganic mercury from wastewater include sulfide precipitation, chemical coagulation, activated carbon adsorption, metal reduction, ion exchange and microbiological methods. General alkaline wastewater containing mercury is usually treated by chemical coagulation or sulfide precipitation. Acidic wastewater containing mercury can be treated by metal reduction method. Low concentration of wastewater containing mercury can be treated by activated carbon adsorption method, chemical coagulation method or activated sludge method. organic mercury wastewater is more difficult to treat, and organic mercury is usually oxidized to inorganic mercury first, and then treated later.

4、Heavy metal wastewater

Heavy metal wastewater mainly comes from the wastewater discharged from mining, smelting, electrolysis, electroplating, pesticide, medicine, paint, pigment and other enterprises. The types, contents and existence forms of heavy metals in wastewater vary with different production enterprises. Since heavy metals can not be decomposed and destroyed, but can only transfer their existence position and change their physical and chemical form. For example, after chemical precipitation treatment, heavy metals in wastewater from the dissolved ionic form into insoluble chemical platform and precipitation, from the water to the sludge; after ion exchange treatment, heavy metal ions in wastewater transferred to the ion exchange resin, after regeneration and then from the ion exchange resin on the regeneration of the waste water transferred to the regeneration. Therefore, the principle of heavy metal wastewater treatment is: first of all, the most fundamental is to reform the production process, do not use or less toxic heavy metals; secondly, the use of reasonable process flow, scientific management and operation, to reduce the amount of heavy metals and the amount of wastewater loss with the wastewater to minimize the amount of discharged wastewater. Heavy metal wastewater should be treated locally at the place where it is generated, and not mixed with other wastewater, so as not to complicate the treatment. What's more, it should not be directly discharged into urban sewers without treatment, so as not to expand heavy metal pollution. The treatment of heavy metal wastewater can usually be divided into two categories; one is to make the wastewater in a dissolved state of heavy metals into insoluble metal compounds or elements, by precipitation and flotation from the wastewater removal. Application methods such as neutralization and precipitation, sulfide precipitation, floating separation method, electrolytic precipitation (or floating) method, diaphragm electrolysis method, etc.; the second is the heavy metals in wastewater in the conditions of its chemical form without changing the concentration and separation of the application of methods such as reverse osmosis, electrodialysis, evaporation, and ion exchange method. These methods should be used individually or in combination according to the wastewater quality and water quantity.

5、Cyanide wastewater

Wastewater containing cyanide mainly comes from electroplating, gas, coking, metallurgy, metal processing, chemical fiber, plastics, pesticides, chemicals and other sectors. Wastewater containing cyanide is a kind of industrial wastewater with high toxicity, unstable in water, easy to decompose, inorganic cyanide and organic cyanide are all highly toxic substances, which can cause acute poisoning when ingested. The lethal amount of cyanide to human body is 0.18, potassium cyanide is 0.12g, and the mass concentration of cyanide in the water body which is lethal to fish is 0.04~0.1mg/L. The main measures for the management of cyanide wastewater are: 1) Reform the process to reduce or eliminate the discharge of cyanide wastewater, such as the use of cyanide-free plating method to eliminate the industrial wastewater of plating workshop. 2) Wastewater containing high cyanide content should be recycled, and wastewater containing low cyanide content should be purified before being discharged. Wastewater with low cyanide content should be purified and treated before discharge. Recycling methods include acidification and aeration - alkaline liquid absorption method, steam desorption method, etc. Treatment methods include alkaline chlorination, electrolytic oxidation, pressurized hydrolysis, biochemical method, bio-iron method, ferrous sulfate method, air blowing method, etc. Among them, alkaline chlorination is more widely used. Among them, alkaline chlorination method is more widely used, ferrous sulfate method is not complete and unstable, air blowing off method not only pollutes the atmosphere, but also fails to meet the emission standards. Less used.

7、Food industry wastewater

The food industry has a wide range of raw materials, a wide range of products, and the quantity and quality of wastewater discharged varies greatly.

The main pollutants in the wastewater:

(1) Floating in the wastewater solids, such as leaves, peels, minced meat, poultry feathers and so on;

(2) Suspended in the wastewater substances such as grease, protein, starch, colloidal substances;

(3) Acid, alkali, salt, sugar, etc. dissolved in wastewater:

(4) Mud and sand entrained by raw materials and other organic substances, etc.;

(5) Pathogenic bacteria and toxins.

Food industry wastewater is characterized by a high content of organic matter and suspended solids, easy to rot, generally no major toxicity. The harm is mainly to make the water body eutrophication, so as to cause the death of aquatic animals and fish, prompting the deposition of organic matter under the water to produce odor, deterioration of water quality, pollution of the environment. Food industry wastewater treatment in addition to appropriate pretreatment according to the characteristics of water quality, generally appropriate to use biological treatment. If the water quality *ments are very high or because of the high content of organic matter in the wastewater, two-stage aeration pool or two-stage biofilter, or multi-stage biological carousel. or the joint use of two biological treatment devices, can also be used anaerobic - aerobic tandem.

8, paper industry wastewater

Paper wastewater mainly from the paper industry production of pulp and paper two production processes. Pulping is the separation of fibers from plant materials, made of pulp, and then bleaching; paper is diluted pulp, molding, pressing, drying, made of paper. Both processes discharge a large amount of wastewater. Pulping wastewater, the most serious pollution. Pulp washing wastewater discharged black-brown, known as black water, black water in the concentration of pollutants is very high, BOD up to 5 ~ 40g / L, containing a large number of fibers, inorganic salts and pigments. The wastewater discharged from the bleaching process also contains a large number of acid and alkali substances. The wastewater discharged from the paper machine, called white water, contains a large number of fibers and fillers and gums added in the production process. Paper industry wastewater treatment should focus on improving the recycled water rate, reduce water consumption and wastewater discharge, but also should actively explore a variety of reliable, economic and can make full use of the useful resources in the wastewater treatment methods. For example, flotation method can recover fibrous solids in white water, recovery rate of up to 95%, the clarified water can be reused; combustion method can be recovered from black water in the hydroxide, sodium sulfide, sodium sulfate, and other sodium salts with the combination of organic matter. Neutralization method to adjust the pH of wastewater; coagulation and precipitation or flotation method to remove suspended solids in wastewater; chemical precipitation method can be decolorized; biological treatment method to remove BOD, kraft wastewater is more effective; wet oxidation method to deal with sulfite pulp wastewater is more successful. In addition, reverse osmosis, ultrafiltration, electrodialysis and other treatment methods are also used at home and abroad.

9, Printing and dyeing industry wastewater

Printing and dyeing industry water consumption is large, usually every printing and dyeing processing 1t textile water consumption 100 ~ 200t. 80% ~ 90% of which to printing and dyeing wastewater discharged. Commonly used treatment methods are recycling and harmless treatment. Recycling: 1) Wastewater can be recycled according to the characteristics of water quality, such as bleaching and cooking wastewater and dyeing and printing wastewater diversion, the former can be convective washing. A water multi-purpose, reduce emissions; 2) lye recycling, usually using evaporation method recovery, such as lye volume, available three-effect evaporation recovery, lye volume is small, available film evaporation recovery; 3) dye recovery. Such as serum dyes can be acidified into cryptoparaffinic acid, as colloidal particles. Suspended in the residual liquid, after precipitation and filtration recycling. Harmless treatment can be divided into: 1) physical treatment method, such as precipitation and adsorption method. Precipitation method is mainly to remove suspended solids in wastewater; adsorption method is mainly to remove dissolved pollutants in wastewater and decolorization. 2) Chemical treatment method has neutralization, coagulation and oxidation method. Neutralization method is to adjust the acidity and alkalinity of wastewater, but also to reduce the chromaticity of wastewater; coagulation method is to remove dispersed dyes and colloidal substances in wastewater; oxidation method is to oxidize the reducing substances in wastewater, so that sulfide dyes and reducing dyes precipitate down. 3) biological treatment methods include activated sludge, biological turntable, biological rotor and biological contact oxidation method. In order to improve the quality of the effluent water to meet the discharge standards or recycling *ments. Often need to use several methods of joint treatment.

10、Dye production wastewater

Dye production wastewater contains acids, alkalis, salts, halogens, hydrocarbons, amines, nitro substances and dyes and their intermediates, etc. Some of them also contain pyridine, cyanide, phenol, benzidine and heavy metals such as mercury, cadmium and chromium. These wastewater components are complex, toxic and difficult to treat. Therefore, the treatment of dyestuff production wastewater. According to the characteristics of the wastewater and its discharge *ments. Appropriate treatment methods should be selected. For example: to remove solid impurities and inorganic substances, coagulation and filtration method can be used; to remove organic and toxic substances, mainly using chemical oxidation, biological methods and reverse osmosis; decolorization can generally be used in coagulation and adsorption method composed of the process, the removal of heavy metals can be used in the ion-exchange method and so on.

11、Chemical industry wastewater

Chemical industry wastewater mainly comes from the petrochemical industry, coal chemical industry, acid and alkali industry, fertilizer industry, plastics industry, pharmaceutical industry, dyestuff industry, rubber industry and other production wastewater discharged. Chemical wastewater pollution prevention and control measures are: first of all, we should reform the production process and equipment, reduce pollutants, prevent wastewater discharge, comprehensive utilization and recycling; must be discharged wastewater, the degree of treatment should be based on the quality of water and the *ments of choice. The primary treatment mainly separates the suspended solids, colloidal matter, floating oil or heavy oil in the water. Water quality and quantity adjustment, natural sedimentation, floating and oil separation methods can be used. Secondary treatment is mainly to remove biodegradable organic solutes and some colloidal matter, reduce the biochemical oxygen demand and part of the chemical oxygen demand in wastewater, usually using biological treatment. After biological treatment of wastewater, but also a considerable amount of residual COD, sometimes with high color, smell, taste, or because of high environmental health standards, it is necessary to use tertiary treatment methods for further purification. Tertiary treatment is mainly to remove organic pollutants and dissolved inorganic pollutants in wastewater that are difficult to biodegrade. Commonly used methods include activated carbon adsorption and ozone oxidation, and ion exchange and membrane separation technology can also be used. Various chemical industry wastewater can be based on different water quality, water quality and discharge water quality *ments after treatment, the choice of different treatment methods.

Mineral processing wastewater has a large amount of water, high content of suspended solids, containing more types of harmful substances. The harmful substances are heavy metal ions and mineral processing chemicals. Heavy metal ions are copper, zinc, lead, nickel, barium, cadmium and arsenic and rare elements.

(6) ore paddle regulator, such as sulfuric acid, lime and so on. Beneficiation wastewater mainly through the tailings dam can effectively remove suspended solids in wastewater, heavy metals and flotation chemicals content can also be reduced.

(2) The main addition of flotation chemicals can be used ore adsorption method, activated carbon adsorption method;

(3) Cyanide-containing wastewater can adopt chemical oxidation method.

14, metallurgical wastewater metallurgical wastewater is mainly characterized by a large amount of water, a variety of complex and variable water quality. According to the source and characteristics of wastewater classification, there are mainly cooling water, pickling wastewater, washing wastewater (dust, gas or flue gas), slag flushing wastewater, coking wastewater, as well as by the production of coagulation, separation or overflow of wastewater and so on.

If you still have questions about wastewater treatment, please contact, WhatsApp: +86 1903715 2650 Yuan Zhang Manager