Industrial wastewater refers to waste water, sewage and waste liquid produced in industrial production processes, which contain industrial production materials, intermediate products and products that are lost with water, and pollutants generated during production.
With the rapid development of industry, the types and quantities of wastewater have increased rapidly, and the pollution of water bodies has become increasingly widespread and serious, threatening human health and safety. For the protection of the environment, the treatment of industrial wastewater is more important than the treatment of urban sewage.
Although the treatment of industrial wastewater began as early as the end of the 19th century, and a large number of experimental research and production practices were carried out in the following half century, due to the complex and varied nature of many industrial wastewaters, there are still some technical problems that have not been fully solved. . This is different from the already mature urban sewage treatment technology.
Industrial wastewater classification: usually three
The first type is classified according to the chemical properties of the main pollutants contained in industrial wastewater. The inorganic pollutants are mainly inorganic wastewater, and the organic pollutants are mainly organic pollutants. For example, electroplating wastewater and wastewater from mineral processing are inorganic wastewater; wastewater from food or petroleum processing is organic wastewater.
The second is classified according to the products and processing objects of industrial enterprises, such as metallurgical wastewater, papermaking wastewater, coking coal gas wastewater, metal pickling wastewater, chemical fertilizer wastewater, textile printing and dyeing wastewater, dye wastewater, tannery wastewater, pesticide wastewater, power station wastewater. Wait.
The third type is classified according to the main components of the pollutants contained in the wastewater, such as acidic wastewater, alkaline wastewater, cyanide-containing wastewater, chromium-containing wastewater, cadmium-containing wastewater, mercury-containing wastewater, phenol-containing wastewater, aldehyde-containing wastewater, and oily wastewater. , sulfur-containing wastewater, organic phosphorus wastewater and radioactive wastewater.
The first two classifications do not address the major components of the contaminants contained in the wastewater, nor do they indicate the hazard of the wastewater. The third classification method clearly indicates the composition of the main pollutants in the wastewater, which can indicate the certain hazard of the wastewater.
In addition, from the difficulty of wastewater treatment and the hazard of wastewater, the main pollutants in wastewater are classified into three categories:
The first type is waste heat, mainly from cooling water, which can be reused;
The second category is conventional contaminants, ie substances that are not susceptible to toxicity and are readily biodegradable, including biodegradable organics, compounds that can be used as biological nutrients, and suspended solids;
The third category is toxic pollutants, that is, substances that are toxic and not easily biodegradable, including heavy metals, toxic compounds, and organic compounds that are not easily biodegradable.
In fact, an industry can discharge several different types of wastewater, and a wastewater will have different pollutants and different pollution effects. For example, the dye factory discharges both acidic wastewater and alkaline wastewater. Textile printing and dyeing wastewater, due to the difference in fabrics and dyes, the pollutants and pollution effects will be very different.
Even a wastewater discharged from a production unit may contain several pollutants at the same time. For example, distillation, cracking, coking, superposition, etc. of the refinery contain phenol, oil and sulfide in the condensed water of the overhead oil vapor. In different industrial enterprises, although the products, raw materials and processing processes are completely different, similarly similar wastewaters may be discharged. Such as refineries, chemical plants and coking gas plants, etc., may contain oil, phenol-containing wastewater discharge.
Industrial wastewater treatment principles
The effective treatment of industrial wastewater should follow the following principles:
1. The most fundamental thing is to reform the production process and eliminate the production of toxic and harmful wastewater in the production process. Replace toxic materials or products with non-toxic materials or products.
2. In the production process of using toxic raw materials and producing toxic intermediates and products, adopt reasonable process and equipment, and implement strict operation and supervision to eliminate leakage and minimize the loss.
3, containing highly toxic waste water, such as containing some heavy metals, radioactive materials, high concentrations of phenol, cyanide and other wastewater should be diverted from other wastewater, in order to facilitate the treatment and recovery of useful substances.
4. Some wastewater with large flow and low pollution, such as cooling wastewater, should not be discharged into the sewer to avoid increasing the load on urban sewers and sewage treatment plants. This type of wastewater should be recycled after proper treatment in the plant.
5. Organic wastewater that is similar in composition and properties to municipal wastewater, such as papermaking wastewater, sugar wastewater, food processing wastewater, etc., can be discharged into urban sewage systems. Large-scale sewage treatment plants should be built, including simple and feasible treatment facilities such as biological oxidation ponds, sewage reservoirs and land treatment systems constructed according to local conditions. Compared with small-scale sewage treatment plants, large-scale sewage treatment plants can significantly reduce capital construction and operation costs, and because of the stable water volume and water quality, it is easy to maintain good operating conditions and treatment effects.
6. Some toxic waste waters that can be biodegraded, such as phenol and cyanide-containing wastewater, can be discharged into urban sewers according to the allowable discharge standards after being treated in the factory, and further subjected to bio-oxidative degradation treatment by the sewage treatment plant.
7. Wastewater containing toxic pollutants that are difficult to biodegrade should not be discharged into urban sewers and transported to sewage treatment plants, but should be treated separately. The development trend of industrial wastewater treatment is to recycle wastewater and pollutants as useful resources or to implement closed loops.
Introduction to industrial wastewater treatment methods
1. What are the hazards of phenol-containing wastewater, and how to deal with it?
The phenol-containing wastewater mainly comes from the industrial sectors such as coking plants, gas plants, petrochemical plants, and insulating materials plants, as well as the production process of petroleum cracking to ethylene, synthetic phenol, polyamide fiber, synthetic dyes, organic pesticides and phenolic resins.
The phenol-containing wastewater mainly contains phenolic compounds such as phenol, cresol, xylenol and nitrocresol. A phenolic compound is a protoplasmic poison that causes the protein to coagulate.
When the concentration of phenol in water at a 0.1 0.2mg / L, i.e. fish odor can not eat; concentration increased to 1mg / L, will affect fish spawning, phenol 5-10mg / L, will be a large number of fish death. The presence of phenol in drinking water can affect human health. Even if the concentration of phenol in water is only 0.002mg/L, disinfection with chlorine will produce phenol odor.
The phenol-containing wastewater having a mass concentration of 1000 mg/L is generally referred to as a high-concentration phenol-containing wastewater, which is subjected to treatment after being recovered. The phenol-containing wastewater with a mass concentration of less than 1000 mg/L is called a low concentration phenol-containing wastewater.
This type of wastewater is usually recycled, and the phenol is concentrated and recovered for treatment. The methods for recovering phenol include solvent extraction, steam stripping, adsorption, closed loop, and the like. Wastewater containing a phenol concentration of less than 300 mg/L may be treated or discharged by biooxidation, chemical oxidation, or physicochemical oxidation.
2. How to treat mercury-containing wastewater, what are the characteristics of mercury-containing compounds?
Mercury-containing wastewater is mainly from non-ferrous metal smelters, chemical plants, pesticide plants, paper mills, dye factories and thermal instrumentation plants.
Methods for removing inorganic mercury from wastewater include sulfide precipitation, chemical coacervation, activated carbon adsorption, metal reduction, ion exchange, and microbial methods.
Generally, alkaline alkaline mercury-containing wastewater is usually treated by chemical coacervation or sulfide precipitation. Acidic mercury-containing wastewater can be treated by metal reduction. Low-concentration mercury-containing wastewater can be treated by activated carbon adsorption, chemical coacervation or activated sludge. Organic mercury wastewater is difficult to treat. Organic mercury is usually first oxidized to inorganic mercury and then treated.
3. What are the characteristics of oily wastewater and how to control it?
Oily wastewater mainly comes from petroleum, petrochemical, steel, coking, gas generating stations, mechanical processing and other industrial sectors.
The oil-contaminated substances in the wastewater have a relative density of less than 1 except for the relative density of the heavy tar of 1.1 or more. Oils are usually present in three states in wastewater.
(1) Floating oil. The oil droplets have a particle size of more than 100 μm and are easily separated from the wastewater.
(2) Disperse the oil. The oil droplets have a particle size between 10 and 100 μm and float in water.
(3) Emulsified oil. The oil droplets have a particle size of less than 10 μm and are not easily separated from the wastewater.
Because the oil concentration in the wastewater discharged from different industrial sectors varies greatly, such as wastewater generated during the refining process, the oil content is about 150-1000 mg/L, and the tar content in the coking wastewater is about 500-800 mg/L. The tar content can reach 2000-3000mg/L.
Therefore, the treatment of oily wastewater should first use the grease trap to recover the oil or heavy oil. The treatment efficiency is 60% to 80%, and the oil content in the effluent is about 100-200mg/L. The emulsified oil and dispersed oil in the wastewater are difficult. Treatment should prevent or mitigate emulsification.
One of the methods is to reduce the emulsification of the oil in the 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. The treatment method usually uses air flotation and demulsification.
4. What are the sources of heavy metal wastewater and its treatment principles?
Heavy metal wastewater mainly comes from wastewater discharged from mining, smelting, electrolysis, electroplating, pesticides, medicine, paint, pigments and other enterprises.
The type, content and form of heavy metals in wastewater vary with different manufacturers. Because heavy metals cannot decompose and destroy, they can only transfer their location and transform their physical and chemical forms.
For example, after chemical precipitation treatment, heavy metals in the wastewater are converted from dissolved ion forms into insoluble materials to be precipitated and transferred from the water to the sludge; after ion exchange treatment, heavy metal ions in the wastewater are transferred to the ions. The exchange resin is transferred from the ion exchange resin to the regeneration waste liquid after regeneration.
Therefore, the principle of heavy metal wastewater treatment is:
First of all, the most fundamental thing is to reform the production process. No or less toxic heavy metals are used; secondly, reasonable process, scientific management and operation are adopted to reduce the amount of heavy metals and the amount of wastewater discharged, and to minimize the amount of discharged wastewater. Heavy metal wastewater should be treated locally at the place of production, and different other wastewaters should be mixed to avoid complicating the treatment. It should not be discharged directly into urban sewers without treatment, so as to avoid the expansion of heavy metal pollution.
The treatment of heavy metal wastewater can usually be divided into two categories:
The first is to convert the heavy metal in the dissolved state into an insoluble metal compound or element, which is removed from the wastewater by precipitation and floating. It can be applied by methods such as neutralization precipitation, sulfide precipitation, floating separation, electrolytic precipitation (or Uplifting method, diaphragm electrolysis, etc.
The second is to concentrate and separate the heavy metals in the wastewater without changing the chemical form. The applicable methods include reverse osmosis, electrodialysis, evaporation and ion exchange. These methods should be used singly or in combination depending on the quality of the wastewater, the amount of water, etc.
5. How to deal with cyanide-containing wastewater?
Cyanide-containing wastewater mainly comes from electroplating, gas, coking, metallurgy, metal processing, chemical fiber, plastics, pesticides, and chemical industries. Cyanide-containing wastewater is a kind of toxic industrial wastewater. It is unstable in water and easy to decompose. Inorganic cyanide and organic cyanide are highly toxic substances. People can cause acute poisoning by ingestion. The lethal dose of cyanide to human body is 0.18, and the potassium cyanide is 0.12 g. The mass concentration of cyanide in fish to death is 0.04 to 0.1 mg/L.
The main treatment measures for cyanide-containing wastewater are:
(1) Reforming the process to reduce or eliminate the effluent containing cyanide. If the cyanide-free plating method is used, the industrial wastewater in the electroplating workshop can be eliminated.
(2) Waste water with high cyanide content should be recycled. Waste water with low cyanide content should be purified before being discharged. The recovery methods include acidification aeration-alkali absorption method, steam desorption method, and the like.
The treatment methods include alkaline chlorination method, electrolytic oxidation method, pressurized hydrolysis method, biochemical method, bio-iron method, ferrous sulfate method, air stripping method, and the like. Among them, the alkaline chlorination method is widely used, the ferrous sulfate method is not thorough and unstable, and the air stripping method not only pollutes the atmosphere, but also fails to meet the discharge standard and is less used.
6. What are the characteristics and treatment methods of pesticide wastewater?
There are many varieties of pesticides, and the water quality of pesticide wastewater is complicated. Its main features are:
(1) The concentration of pollutants is high, and the chemical oxygen demand (COD) can reach tens of thousands of mg per liter;
(2) It is highly toxic. In addition to pesticides and intermediates, wastewater contains toxic substances such as phenol, arsenic and mercury, as well as many substances that are difficult to degrade.
(3) It has a foul odor and is irritating to human respiratory tract and mucous membranes;
(4) Water quality and water volume 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 the wastewater of pesticide production, improve the recycling rate, and strive to achieve harmlessness. The treatment methods of the pesticide wastewater 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. Some countries have banned the production of organochlorine and organic mercury pesticides such as hexachlorocyclohexane, and actively researched and used microbial pesticides. This is a new way to fundamentally prevent pesticide wastewater from polluting the environment.
7. What are the characteristics of waste water pollution in food industry and what are the treatment methods?
The food industry has a wide range of raw materials and a wide variety of products. The amount of water and water quality of wastewater discharge varies greatly. The main pollutants in the wastewater are as follows:
(1) Solid substances floating in wastewater, such as vegetable leaves, peels, minced meat, bird feathers, etc.;
(2) The substances suspended in the wastewater are oils, proteins, starches, colloids, etc.;
(3) Acids, alkalis, salts, sugars, etc. dissolved in waste water:
(4) Mud sand and other organic matter entrained in raw materials;
(5) Pathogenic bacteria and so on.
The waste water of the food industry is characterized by high content of organic substances and suspended solids, easy to be spoiled, and generally no major toxicity. The hazard is mainly to make the water body eutrophication, causing the death of aquatic animals and fish, causing the organic matter deposited on the bottom to produce odor, deteriorating water quality and polluting the environment.
In addition to proper pretreatment according to the characteristics of water quality, wastewater treatment in food industry should generally adopt biological treatment. If the effluent water quality is very high or because the organic matter content in the wastewater is very high, a two-stage aeration tank or a two-stage biological filter, or a multi-stage biological turntable, or a combination of two biological treatment devices, or an anaerobic can be used. - Aerobic series.
8. How to deal with paper industry wastewater?
The papermaking wastewater mainly comes from the two production processes of pulping and papermaking in the paper industry. Pulping is to separate the fibers in the plant raw material, make a slurry, and then bleach; the paper is to dilute, shape, press, and dry the slurry to make paper.
Both processes discharge large amounts of wastewater. The wastewater produced by pulping is the most polluted. The waste water discharged during washing is dark brown, called black water. The concentration of pollutants in black water is very high. The BOD is as high as 5-40g/L, which contains a lot of fiber, inorganic salt and pigment. The wastewater discharged from the bleaching process also contains a large amount of acid and alkali substances. The waste water discharged from the paper machine, called white water, contains a large amount of fibers and fillers and rubbers added during the production process.
The treatment of paper industry wastewater should focus on increasing the recycling rate, reducing water consumption and wastewater discharge, and actively exploring various reliable, economical and fully utilizing treatment methods for useful resources in wastewater. For example, the flotation method can recover fibrous solid materials in white water, the recovery rate can reach 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 substances in black water.
The neutralization method adjusts the pH value of the wastewater; the coagulation sedimentation or flotation method can remove the suspended solids in the wastewater; the chemical precipitation method can decolorize; the biological treatment method can remove the BOD, and is effective for the kraft paper wastewater; the wet oxidation treatment of the sulfite pulp wastewater success. In addition, reverse osmosis, ultrafiltration, electrodialysis and other treatment methods are also used at home and abroad.
9. How to deal with printing and dyeing industry wastewater?
The printing and dyeing industry uses a large amount of water. Generally, it consumes 100-200 tons of water per 1 t of textiles for printing and dyeing. 80% to 90% of it is discharged by printing and dyeing wastewater. Commonly used treatment methods are recycling and harmless treatment.
(1) Recycling:
A. Waste water can be recycled separately according to the characteristics of water quality, such as the separation of bleaching and smelting wastewater and dyeing printing wastewater. The former can be used for convection washing. One water is used to reduce emissions;
B, lye recycling, usually by evaporation method, such as large amount of lye, can be recovered by three-effect evaporation, the amount of lye is small, can be recovered by thin film evaporation;
C, dye recovery. For example, the Shilin dye can be acidified into cryptic acid, which is colloidal particles. It is suspended in the residual liquid, filtered and precipitated for recycling.
(2) Harmless treatment can be divided into:
A. Physical treatment methods include precipitation method and adsorption method. The precipitation method mainly removes suspended matter in the wastewater; the adsorption method mainly removes dissolved pollutants and decolorization in the wastewater.
B. The chemical treatment method includes a neutralization method, a coagulation method, and an oxidation method. The neutralization method is to adjust the pH in the wastewater, and also to reduce the color of the wastewater; the coagulation method is to remove the disperse dye and the colloidal substance in the waste water; the oxidation method is to oxidize the reducing substance in the waste water to precipitate the sulfur dye and the vat dye.
C. 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, to meet emission standards or recycling requirements, it is often necessary to use several methods in combination.
10. How to deal with dye production wastewater?
Dye production wastewater contains acids, bases, salts, halogens, hydrocarbons, amines, nitros and dyes and their intermediates, and some also contain pyridine, cyanide, phenol, benzidine and heavy metals such as mercury, cadmium, chromium and so on.
These wastewater components are complex, toxic and difficult to handle.
Therefore, the treatment of dye production wastewater should be based on the characteristics of the wastewater and the discharge requirements. Choose the appropriate treatment method. For example, the removal of solid impurities and inorganic substances, coagulation method and filtration method can be used; the removal of organic matter and toxic substances mainly adopts chemical oxidation method, biological method and reverse osmosis method; decolorization can generally adopt a process composed of coagulation method and adsorption method. In the process, heavy metals can be removed by ion exchange or the like.
11. How to deal with chemical industry wastewater?
Chemical industry wastewater mainly comes from the production wastewater discharged from petrochemical industry, coal chemical industry, acid and alkali industry, fertilizer industry, plastics industry, pharmaceutical industry, dye industry and rubber industry.
The main measures for the prevention and control of chemical wastewater pollution are: firstly, the production process and equipment should be reformed, pollutants should be reduced, waste water should be prevented from being discharged, and comprehensive utilization and recycling should be carried out; the wastewater to be discharged should be selected according to water quality and requirements.
The primary treatment mainly separates suspended solids, colloids, oil slicks or heavy oil in water. Water quality and water volume adjustment, natural sedimentation, floating and oil separation methods can be used.
The secondary treatment mainly removes the biodegradable organic solute and some colloids, reduces the biochemical oxygen demand and partial chemical oxygen demand in the wastewater, and is usually treated by biological methods. A considerable amount of COD remains in the biologically treated wastewater, sometimes with a high color, smell, taste, or high environmental sanitation standards, and further purification is required by a three-stage treatment.
The tertiary treatment is mainly to remove organic pollutants and dissolved inorganic pollutants that are difficult to biodegrade in wastewater. Commonly used methods include activated carbon adsorption and ozone oxidation, and ion exchange and membrane separation techniques can also be used. Various chemical industry wastewaters can be selected according to different water quality, water quantity and post-treatment external drainage quality.
12. What are the characteristics and treatment principles of acid-base wastewater?
Acidic wastewater mainly comes from steel plants, chemical plants, dye factories, electroplating plants and mines, which contain various harmful substances or heavy metal salts. The acid mass fraction varies widely, from less than 1% at low and greater than 10% at high. Alkaline wastewater mainly comes from printing and dyeing factories, leather factories, paper mills, oil refineries and so on. Some of them contain organic or inorganic bases. The mass fraction of the base is higher than 5%, and some are less than 1%. In addition to acid and alkali, acid-base wastewater often contains acid salts, basic salts and other inorganic and organic substances.
Acid-base wastewater is highly corrosive and needs to be properly treated before it can be discharged.
The principle of treating acid and alkali wastewater is:
(1) High-concentration acid-base wastewater should be prioritized for recycling. According to water quality, water volume and different process requirements, plant or regional dispatching should be carried out as much as possible: if it is difficult to reuse, or the concentration is low, the water volume is large. The acid and base can be recovered by a concentrated method.
(2) Low-concentration acid-base wastewater, such as washing water in the acid washing tank and rinsing water in the alkali washing tank, should be neutralized.
For neutralization treatment, the principle of waste treatment should be considered first. For example, acid or alkali wastewater neutralizes each other or neutralizes acidic wastewater with waste alkali (slag), and neutralizes alkaline wastewater with waste acid. In the absence of these conditions, a neutralizing agent treatment can be employed.
13. What flotation reagents are included in the ore dressing wastewater, and how to deal with them?
The ore dressing wastewater has the characteristics of large water volume, high suspended solid content and many types of harmful substances. Its harmful substances are heavy metal ions and mineral processing chemicals. Heavy metal ions include copper, zinc, lead, nickel, antimony, cadmium, and arsenic and rare elements.
The flotation reagents added during the beneficiation process are as follows:
(1) Collecting agents, such as xanthate (RocssMe), black medicine [(RO) 2PSSMe], white medicine [CS (NHC6H5) 2];
(2) Suppression of punishment,
Such as cyanide salt (KCN, NaCN), water glass (Na2SiO3);
(3) a foaming agent such as turpentine or cresol (C6H4CH30H);
(4) Active punishment, such as copper sulfate (CuS04), heavy metal salts;
(5) a vulcanizing agent such as sodium sulfide;
(6) Ore conditioners such as sulfuric acid, lime, etc.
The ore dressing wastewater can effectively remove suspended solids from the wastewater through the tailings dam, and the content of heavy metals and flotation reagents can also be reduced. If the emission requirements are not met, further treatment should be carried out. The commonly used treatment methods are:
(1) Removal of heavy metals may be carried out by lime neutralization and roasting dolomite adsorption;
(2) The main flotation reagent can be ore adsorption method or activated carbon adsorption method;
(3) The cyanide-containing wastewater can be chemically oxidized.
14. Metallurgical wastewater can be divided into several categories. What is its development trend?
The main features of metallurgical wastewater are large amounts of water, many types, and complex and variable water quality. Classified according to the source and characteristics of wastewater, there are mainly cooling water, pickling wastewater, washing wastewater (dust removal, gas or flue gas), slag wastewater, coking wastewater, and wastewater that is condensed, separated or overflowed from production.
The trend of metallurgical wastewater treatment development is:
(1) Develop and adopt new technologies and technologies that use no or little water and no pollution or less pollution, such as dry quenching, coking coal preheating, direct desulfurization and denitrification from coke oven gas;
(2) Develop comprehensive utilization technologies, such as recovering useful substances and heat energy from waste water and waste gas, and reducing material fuel loss;
(3) According to different water quality requirements, comprehensive balance, cross-flow use, and at the same time improve water quality stability measures, and continuously improve the water recycling rate;
(4) The development of new treatment processes and technologies suitable for the characteristics of metallurgical wastewater, such as the treatment of steel wastewater by magnetic method, has the advantages of high efficiency, small land occupation, convenient operation and management.
Kids Poncho Towel,Kids Hooded Beach Towel,Swimming Changing Hooded Towel For Kids,Kids Hooded Poncho Towel
Huaian Meisiyu Textiles Co.,Ltd , https://www.comfortrobe.com