Industrial wastewater refers to the wastewater, sewage and waste liquid produced in the industrial production process, which contains industrial production materials, intermediate products and products that are lost with the water and pollutants generated during the production process. It summarizes the chemical industrial wastewater and the printing and dyeing industrial wastewater. 15, paper industry wastewater, dye production wastewater, food industry wastewater and pesticide wastewater treatment process of 15 industrial wastewater.
1. Desulfurization wastewater from coal-fired power plants
Most desulfurization devices in power plants use flue gas limestone-gypsum wet desulfurization process. The process is mainly composed of a limestone slurry preparation system, a gypsum dehydration system, and a desulfurization wastewater treatment system. The water in the slurry of the desulfurization device will be enriched with heavy metal elements and Cl- in the process of continuous circulation. On the one hand, it accelerates the corrosion of the desulfurization equipment, on the other hand, it affects the quality of gypsum, and it is necessary to discharge the wastewater in a timely manner.
Desulfurization wastewater treatment process of power plant: desulfurization wastewater → wastewater tank → wastewater pump → pH neutralization tank → sedimentation tank → flocculation tank → clarifier → outlet tank → outlet pump → discharge to standard The desulfurization wastewater treatment system includes three parts: wastewater treatment, dosing, and sludge treatment. The waste water treatment system is mainly composed of waste water tanks, triple tanks, clarifiers, sludge pumps, outlet tanks, clean water pumps, fans, dehydrators and other equipment. In addition to a large amount of Cl-, Mg2 +, the impurities in the desulfurization wastewater also include: fluoride, nitrite, etc .; heavy metal ions, such as: Cu2 +, Hg2 +, etc .; insoluble CaSO4 and fine dust. In order to meet the wastewater discharge standards, corresponding wastewater treatment devices are required.
2. Chemical industry wastewater
Chemical industry wastewater mainly comes from: petrochemical industry, coal chemical industry, acid and alkali industry, chemical fertilizer industry, plastic industry, pharmaceutical industry, dye industry, rubber industry and other industrial wastewater.
The main measures for the prevention and control of chemical wastewater pollution are: first of all, production processes and equipment should be reformed to reduce pollutants, prevent waste water from being discharged, and be comprehensively used and recycled; waste water that must be discharged should be selected according to water quality and requirements.
The primary treatment mainly separates suspended solids, colloids, oil slicks or heavy oils in water. Water quality and quantity adjustment, natural sedimentation, floating and oil separation can be used.
The secondary treatment is mainly to remove biodegradable organic dissolved matter and some colloids, and to reduce the biochemical oxygen demand and some chemical oxygen demand in the wastewater. Biological treatment is usually adopted. A considerable amount of COD remains in the biologically treated wastewater, sometimes with high color, odor, and odor, or because of high environmental hygiene standards, a tertiary treatment method is required for further purification.
Tertiary treatment is mainly to remove organic pollutants and soluble inorganic pollutants that are difficult to biodegrade in wastewater. Common methods include activated carbon adsorption and ozone oxidation, and ion exchange and membrane separation technologies can also be used. Various chemical industry wastewater can choose different treatment methods according to different water quality, water quantity and external drainage quality requirements after treatment.
3. Printing and dyeing industry wastewater
The printing and dyeing industry has a large amount of water, and usually consumes 100 ~ 200t of water per 1t of printing and dyeing. 80% ~ 90% are discharged as printing and dyeing wastewater. Common treatment methods are recycling and harmless treatment.
Recycling: Wastewater can be recycled separately according to the characteristics of water quality, such as the diversion of bleaching and cooking wastewater and dyeing and printing wastewater. The former can be washed by convection. Multiple uses of one water can reduce the discharge;
The lye is recovered and reused, usually by evaporation method. If the amount of lye is large, it can be recovered by three-effect evaporation. If the amount of lye is small, it can be recovered by thin film evaporation.
Dye recovery, such as Shihlin dye can be acidified into cryptobasic acid, showing colloidal particles. Suspended in the residual liquid, it can be recycled after filtration.
Harmless treatment can be divided into physical treatment methods such as precipitation method and adsorption method. The precipitation method mainly removes suspended matter in wastewater; the adsorption method mainly removes dissolved pollutants and decoloration in wastewater.
Chemical treatment methods include neutralization, coagulation and oxidation. The neutralization method consists in adjusting the pH of the wastewater, and can also reduce the color of the wastewater. The coagulation method consists in removing the dispersed dyes and colloidal substances in the wastewater. The oxidation method consists in oxidizing the reducing substances in the wastewater to precipitate the sulfur dyes and reducing dyes.
Biological treatment methods include activated sludge, biological turntable, biological drum and biological contact oxidation method. In order to improve the quality of the effluent water and meet discharge standards or recycling requirements, it is often necessary to use several methods for joint treatment.
4. Wastewater from the paper industry
Papermaking wastewater mainly comes from the two processes of pulping and papermaking in the paper industry. Pulp is the process of separating fibers from plant raw materials to make pulp, which is then bleached; papermaking is to dilute, shape, squeeze, and dry the pulp to make paper. Both processes discharge large amounts of wastewater.
Polluted wastewater is the most severely polluted. The waste water discharged during washing is dark brown, which is called black water. The concentration of pollutants in black water is very high, BOD is as high as 5 ~ 40g / L, and it contains a large amount of fiber, inorganic salts and pigments. Wastewater from the bleaching process also contains a large amount of acid and alkali substances. The waste water discharged from the paper machine is called white water, which contains a large amount of fiber and fillers and rubber added during the production process.
Wastewater treatment of the paper industry should focus on improving the recycling rate, reducing water consumption and wastewater discharge. At the same time, we should actively explore a variety of reliable, economical and able to make full use of useful resources in wastewater treatment methods. For example, the flotation method can recover fibrous solid matter in white water with a recovery rate of 95% and the clarified water can be reused; the combustion method can recover sodium hydroxide, sodium sulfide, sodium sulfate, and other sodium salts combined with organic matter in black water.
Neutralization method to adjust the pH value of wastewater; coagulation sedimentation or flotation method can remove suspended solids in wastewater; chemical precipitation method can decolorize; biological treatment method can remove BOD, which is more effective for kraft paper wastewater; wet oxidation method is more effective success. In addition, there are also domestic and foreign treatment methods such as reverse osmosis, ultrafiltration, and electrodialysis.
5.Dye production wastewater
Dye production wastewater contains acids, alkalis, salts, halogens, hydrocarbons, amines, nitro compounds, dyes and their intermediates, and some also contain pyridine, cyanide, phenol, benzidine, and heavy metals mercury, cadmium, and chromium. The components of these wastewaters are complex, toxic and difficult to treat. Therefore, the treatment of dye production wastewater should be based on the characteristics of the wastewater and its discharge requirements. Select an appropriate treatment method.
6. Food industry wastewater
The food industry has a wide range of raw materials and a wide range of products. The amount and quality of discharged wastewater varies widely.
The main pollutants in wastewater are: solid substances floating in wastewater, such as vegetable leaves, peels, minced meat, poultry feathers, etc .; the substances suspended in wastewater include oil, protein, starch, colloidal substances, etc .; acids dissolved in wastewater , Alkali, salt, sugar, etc .; mud and other organic matter entrained by raw materials; etc .;
Food industry wastewater is characterized by high organic matter and suspended matter content, easy to spoil, and generally has no major toxicity. Its harm is mainly to make the water body eutrophic, which will cause the death of aquatic animals and fish, promote the odor of organic matter deposited on the bottom of the water, deteriorate the water quality and pollute the environment.
In addition to proper pretreatment according to water quality characteristics, the wastewater treatment in the food industry is generally suitable for biological treatment. If the quality of the effluent is very high or the organic matter content in the wastewater is high, a two-stage aeration tank or a two-stage biological filter, or a multi-stage biological turntable can be used. Or two types of biological treatment devices can be used in combination, or anaerobic can be used. -Aerobic series.
7. Pesticide wastewater
There are many types of pesticides, and the quality of pesticide wastewater is complex. Its main characteristics are: high concentration of pollutants, chemical oxygen demand (COD) can reach tens of thousands of milligrams per liter; high toxicity, in addition to pesticides and intermediates in wastewater, toxic substances such as phenol, arsenic, mercury and many other Bio-degradable substances; foul odor, irritating to the human respiratory tract and mucous membranes; water quality and quantity are unstable.
Therefore, the pollution of pesticide wastewater to the environment is very serious. The purpose of pesticide wastewater treatment is to reduce the concentration of pollutants in pesticide production wastewater, improve the recycling rate, and strive to achieve harmlessness. Pesticide wastewater treatment methods include activated carbon adsorption method, wet oxidation method, solvent extraction method, distillation method and activated sludge method. However, the development of new pesticides with high efficiency, low toxicity and low residue is the development direction of pesticides.
The cyanide-containing wastewater mainly comes from electroplating, coal gas, coking, metallurgy, metal processing, chemical fiber, plastic, pesticide, chemical and other departments.
Cyanide-containing wastewater is a relatively toxic industrial wastewater. It is unstable in water and easily decomposes. Inorganic cyanide and organic cyanide are highly toxic substances. Human ingestion can cause acute poisoning. The lethal amount of cyanide to the human body is 0.18g, the potassium cyanide is 0.12g, and the mass concentration of cyanide to fish in water is 0.04 ~ 0.1mg / L.
The cyanide-containing wastewater treatment measures mainly include: reforming the process to reduce or eliminate effluent cyanide-containing wastewater. If cyanide-free electroplating is used, industrial wastewater in electroplating workshops can be eliminated. Wastewater with high cyanide content should be recycled. Wastewater with low cyanide content should be purified before being discharged. Recovery methods include acidification aeration-alkali solution absorption method, steam desorption method, and the like.
The treatment methods include alkaline chlorination method, electrolytic oxidation method, pressure hydrolysis method, biochemical method, biological iron method, ferrous sulfate method, and air stripping method. Among them, the alkaline chlorination method is widely used, the ferrous sulfate method is incomplete and unstable, and the air stripping method pollutes the atmosphere and the effluent does not meet the discharge standards. Less adopted.
Phenol-containing wastewater mainly comes from coking plants, gas plants, petrochemical plants, insulation materials plants and other industrial sectors, as well as the production of ethylene, synthetic phenol, polyamide fibers, synthetic dyes, organic pesticides and phenolic resins from petroleum cracking. The phenol-containing wastewater mainly contains phenol-based compounds, which are a protoplasmic toxicant that can solidify proteins.
10. Mercury-containing wastewater
Mercury-containing wastewater mainly comes from non-ferrous metal smelters, chemical plants, pesticide plants, paper mills, dye plants and thermal instrumentation plants. The toxicity of various mercury compounds is very different, such as methylmercury, methylmercury is easily absorbed into the human body, not easily degraded, excreted very slowly, and easily accumulated in the brain.
11.Heavy metal wastewater
The heavy metal wastewater mainly comes from the wastewater from mining, smelting, electrolysis, electroplating, pesticide, medicine, paint, pigment and other enterprises. The types, contents and existing forms of heavy metals in wastewater vary with different production enterprises.
The principle of heavy metal wastewater treatment is: the most fundamental is to reform the production process without using or reducing the use of toxic heavy metals; followed by the use of reasonable technological processes, scientific management and operation to reduce the amount of heavy metals and the amount of waste with wastewater, and minimize efflux Amount of wastewater. Heavy metal wastewater should be treated in situ at the place of production and mixed with other wastewater to avoid complicating the treatment. Moreover, it should not be discharged directly into urban sewers without treatment, so as to avoid expanding heavy metal pollution.
The treatment of heavy metal wastewater can generally be divided into two categories: one is to convert the heavy metals in the wastewater in a dissolved state into insoluble metal compounds or elements and remove them from the wastewater by precipitation and floating. Applicable methods such as neutralization precipitation method, sulfide precipitation method, floating separation method, electrolytic precipitation (or floating) method, diaphragm electrolysis method, etc .; second, the heavy metals in the wastewater are concentrated without changing their chemical form and For separation, applicable methods include reverse osmosis, electrodialysis, evaporation, and ion exchange. These methods should be used alone or in combination according to the quality and quantity of wastewater.
12. Metallurgical wastewater
The main characteristics of metallurgical wastewater are large water volume, many types, and complex and variable water quality. According to the source and characteristics of wastewater, there are mainly cooling water, pickling wastewater, washing wastewater (dust removal, gas or flue gas), slag washing wastewater, coking wastewater, and wastewater condensed, separated or overflowed during production.
The development trend of metallurgical wastewater treatment is to develop and adopt new processes and technologies that use no or little water and no pollution or pollution. Develop comprehensive utilization technologies, such as recovering useful substances and heat energy from waste water and waste gas, and reducing material and fuel loss; according to different water quality requirements, comprehensively balance and use in series, while improving water quality stabilization measures, and continuously improving water cycle utilization; The new treatment technology and technology of metallurgical wastewater characteristics, such as magnetic steel treatment of steel wastewater, has the advantages of high efficiency, small footprint, convenient operation and management.
13. Acid and alkali wastewater
Acid wastewater mainly comes from steel plants, chemical plants, dye plants, electroplating plants and mines, etc., which contains various harmful substances or heavy metal salts. The mass fractions of acids vary widely, ranging from less than 1% to as high as 10%.
Alkaline wastewater mainly comes from printing and dyeing plants, leather mills, paper mills, and oil refineries. Some of them contain organic bases or inorganic bases. Some of the mass fractions of alkali are higher than 5% and some are lower than 1%. In addition to acid-base wastewater, acid-base wastewater often contains acid salts, basic salts, and other inorganic and organic substances.
Acid-alkali wastewater is highly corrosive and can only be discharged after proper treatment.
The general principle for treating acid-alkali wastewater is: high-concentration acid-alkali wastewater should be prioritized for recycling. According to water quality, water volume and different process requirements, carry out plant or regional scheduling and try to reuse as much as possible: if reuse is difficult, or the concentration is too high Low, large amount of water, can be concentrated to recover acid and alkali.
Low-concentration acid and alkali wastewater, such as the washing water of the pickling tank and the rinse water of the alkali cleaning tank, should be neutralized.
For neutralization treatment, the principle of treating waste with waste should be considered first. Such as acid and alkaline wastewater neutralize each other or use waste alkali (slag) to neutralize acidic wastewater, use waste acid to neutralize alkaline wastewater. In the absence of these conditions, a neutralizing agent can be used.
Beneficiation wastewater has the characteristics of large water volume, high suspended matter content, and many types of harmful substances. Its harmful substances are heavy metal ions and ore dressing agents. Heavy metal ions include copper, zinc, lead, nickel, barium, cadmium, and arsenic and rare elements.
The beneficiation wastewater is mainly passed through the tailings dam to effectively remove suspended matter in the wastewater, and the content of heavy metals and flotation reagents can also be reduced. If the discharge requirements are not met, further treatment should be carried out. Common treatment methods are: lime neutralization and roasted dolomite adsorption can be used to remove heavy metals; ore adsorption method and activated carbon adsorption method can be used as the main removal flotation agent; Cyanide wastewater can be chemically oxidized.
15. Oily wastewater
Oily wastewater mainly comes from industrial sectors such as petroleum, petrochemicals, iron and steel, coking, gas generation stations, and mechanical processing. Except for heavy tars with a relative density of 1.1 or higher, the remaining relative density of oily pollutants in the wastewater is less than 1. Oily substances usually exist in three states in wastewater.
Floating oil, the diameter of the oil droplets is larger than 100 μm, and it is easy to separate from the waste water.
Disperse the oil, the diameter of the oil droplets is between 10 and 100 μm, and float in water.
Emulsified oil, the diameter of the oil droplets is less than 10 μm, and it is not easy to separate from the wastewater.
Due to the large differences in oil concentration in wastewater discharged from different industrial sectors, such as wastewater generated during the refining process, the oil content is about 150 ~ 1000mg / L, the tar content in coking wastewater is about 500 ~ 800mg / L, and the wastewater from the gas generation station is discharged into the wastewater. The tar content can reach 2000 ~ 3000mg / L.
Therefore, the treatment of oily wastewater should first use an oil trap to recover oil slicks or heavy oil. The treatment efficiency is 60% to 80%, and the oil content in the effluent is about 100 to 200mg / L. Emulsified and dispersed oil in wastewater is difficult. Treatment, it should prevent or reduce the emulsification phenomenon.
The first is to reduce the emulsification of oil in wastewater during the production process;
The second is to minimize the number of times the pump is used to raise the wastewater during the treatment process, so as not to increase the degree of emulsification. Treatment methods usually use air flotation and demulsification.