How is sewage generally treated? How sewage is generally treated

1.The physical process, including filtration, precipitation, air flotation, and high-end membrane separation, I think it should also be considered a physical means. However, with the exception of membrane separation.

Several other means can basically only solve the problem of suspended solids impurities in water, and are generally used as pre-treatment means. In addition, there are energy-intensive distillation and concentration methods, which are generally only suitable for small-scale wastewater treatment with high concentrations. Otherwise, no one can afford that cost.

2.Chemical processes, including dosing precipitation, dosing and color removal, chemical oxidation, etc., are simply put, or to solve the problem of color. More often, it is mainly through the reaction to form a precipitate to remove some harmful components, and at the same time adjust the pH value, which is one of the main means to treat heavy metal wastewater and strong acid and alkaline wastewater.

3. Physical and chemical process, which is the most important type of process for treating industrial wastewater, such as resin adsorption, photocatalyst cracking, electrolytic replacement, etc., this part almost concentrates various high-tech sewage treatment, and I also; This part can mainly play several roles, one is to separate the high-concentration materials in the sewage and reduce the concentration of sewage, and the other is to degrade the polymers in the water, improve the B C ratio, make the wastewater biodegradable, and reduce the toxicity of the wastewater and remove certain pollutants in a directional manner.

4. Biochemical process, the biochemical process principle of industrial sewage is the same as that of domestic sewage, but the process is more complex, the load range is larger, and it can easily withstand several thousand mg L of COD. Multi-stage biochemistry is often required to gradually reduce the concentration of the effluent so that it can eventually reach the target. <>

The relative composition of live sewage is fixed, and after the approximate scale and influent water quality are determined, it can be done with certain routines, but it is adjusted and optimized according to the specific local conditions and investment requirements. However, strictly speaking, process calculations, numerical modeling, and experiments are still required before the design and construction of biochemical wastewater.

Industrial wastewater due to the source of production is very different (such as papermaking wastewater, alcohol wastewater, printing and dyeing wastewater), different production processes (for example, the same printing and dyeing enterprises, the production line built in the last century and the production process of the production line built now are completely different) and the local environment, management level and other factors, basically a factory sewage (even if it is two factories that also produce the same product, as long as the location is different) is a new technology research and development and construction, so there is no fixed model, can only be through digital modeling, Small-scale experiments, medium-sized experiments, etc. Industrial wastewater is not much to say, interested friends can take a look at the industrial sewage section of the "Outdoor Drainage Handbook". There's a rough description in it.

The domestic sewage generated by human life is collected through the pipe network to the underground septic tank near the building, where the initial sedimentation and digestion are carried out. Here, feces, toilet paper, etc., precipitate to the bottom of the septic tank due to their own density, and at the same time are decomposed (eaten) by aerobic bacteria, anaerobic bacteria, and facultative bacteria (which can survive with or without oxygen) and become small particles and water-soluble substances. Therefore, the septic tank needs to be cleaned for a period of time (generally half a year to a year), even if it is a high-end community septic tank.

The first thing that domestic sewage passes through is the grid, which generally has two thick and thin channels. The coarse grille is in the gap of 10-30 mm, and the fine grille is around the gap of 3 mm. Floating and suspended solids in the wastewater are intercepted as they pass through here, transported by screw conveyor or belt conveyor to the slag dump point and transported to the landfill for landfill.

In order to reduce the complexity of the subsequent system and save energy, the sewage filtered by the coarse and fine grids (some in front of the coarse grids and the fine grids) is generally lifted to the highest point of the whole sewage plant through the pumping station, and then flows through the subsequent treatment facilities by gravity. <>

Separation is to separate some pollutants in sewage from the water body, specific measures include sedimentation, flocculation, centrifugation, air flotation, blowing off, etc., basically physical and chemical methods. Usually, most of the pollutants in the sewage, such as organic matter, can be removed after preliminary separation and treatment, and if the requirements are not high, they can be discharged directly. This is known as primary treatment.

Some contaminants cannot be effectively separated, such as dissolved organic matter, ammonia nitrogen, and phosphate, which need to be converted into harmless substances or substances that can be easily separated. The main biochemical processes in wastewater treatment are the conversion of organic matter, such as the removal of dissolved organic matter by converting organic matter into carbon dioxide (basically harmless, the gas can be easily separated from the water body) and biological sludge (harmful, but also easy to precipitate). This is known as secondary treatment.

There are many kinds of transformation methods, such as various advanced oxidation, acid-base neutralization and so on. The cyanide sewage produced by the Tianjin ** accident can only be broken by strong oxidation of hydrogen peroxide to break the C-N bond and make it harmless. <>

The choice of sewage treatment method mainly depends on the water quality of the sewage Xunzipai, and the Muhe methods that can be selected are: physical method (precipitation, air flotation, filtration, ion exchange, etc.), chemical method (Fenton oxidation, acid-base neutralization, catalytic oxidation, etc.), biochemical method (activated sludge method, biofilm method, oxidation pond, land treatment, etc.).

At present, most of the sewage treatment uses biochemical methods, and some of the more difficult ones are treated with physics or chemistry, or physicochemical and biological, and finally decide what method to use or what combination of methods is the element, or water quality.

1. Physical method: It mainly uses physical action to separate non-soluble substances in sewage, and does not change the chemical properties during the treatment process. Commonly used are gravity separation, centrifugal separation, reverse osmosis, air flotation, etc.

The physical treatment of limb Hengxun structure is relatively simple and economical, and is used for the situation that the water body of villages and towns has a large capacity, strong self-purification ability, and low requirements for sewage treatment.

2. Biological method: using the metabolic function of microorganisms, the organic matter in the dissolved or colloidal state in the sewage is decomposed and oxidized into stable inorganic substances, so that the sewage can be purified. Commonly used are activated sludge method and biofilm method. The biological method is more highly processed than the physical method.

3. Chemical method: It is a method that uses chemical reaction to treat or dissolved substances or colloidal substances in sewage, and is mostly used in industrial wastewater. Commonly used are coagulation method, neutralization method, redox method, ion exchange method, etc.

The chemical treatment method has good treatment effect and high cost, and is mostly used as effluent after biochemical treatment for further treatment to improve the effluent quality.

Sewage treatment refers to the process of removing impurities, harmful substances and microorganisms from human production and life through a series of treatment processes to meet the discharge standards or reuse standards stipulated by the state. Eco laboratory wastewater treatment equipment uses high-quality materials and advanced manufacturing technology, with good durability and reliability, and can operate stably for a long time. Sewage treatment can generally be divided into the following steps:

1.Hydrolysis and acidification: The raw sewage is mixed, the pH value is adjusted, and an appropriate amount of microbial agent is added to make it decompose, acidify and other reactions.

2.Activated sludge treatment: The sewage that has been hydrolyzed and acidified is deeply treated, activated sludge is added, and the organic substances in the sewage are further decomposed and purified through aeration, sedimentation and other processes.

3.Filter filtration: Large particles of impurities and sediment are filtered out through the filter to reduce the impact on the follow-up treatment equipment.

4.Disinfection treatment: By adding disinfectants, the treated sewage is disinfected to kill various pathogens in it to ensure the health and safety of the effluent.

After the final treatment is completed, it is discharged through the effluent pipeline or reused, such as for irrigation, industrial water, etc.

There are many kinds of industrial sewage, and there is not a basic uniform pattern like urban sewage.

Take printing and dyeing wastewater as an example:

Dye production wastewater contains acids, alkalis, salts, halogens, hydrocarbons, amines, nitros, dyes and their intermediates and other substances, and some also contain pyridine, cyanide, phenol, benzidine and heavy metals mercury, cadmium, chromium, etc. 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.

For example, to remove solid impurities and inorganic substances, coagulation and filtration methods can be used; Chemical oxidation, biological and reverse osmosis are mainly used to remove organic matter and toxic substances. Decolorization can generally use the process composed of coagulation and adsorption, and ion exchange method can be used to remove heavy metals.

Take food wastewater, for example

The food industry has a wide range of raw materials and a wide variety of products, and the hidden source content of the water quantity and water quality discharged from the wastewater varies greatly. The main pollutants in wastewater are: (1) solid substances floating in wastewater, such as vegetable leaves, fruit peels, minced meat, poultry feathers, etc.; (2) The substances suspended in wastewater include oil, protein, starch, colloidal substances, etc.; (3) Acids, alkalis, salts, sugars, etc. dissolved in wastewater: (4) Sediment and other organic matter entrained by raw materials; (5) Pathogenic bacteria and toxins.

Food industry wastewater is characterized by high content of organic matter and suspended solids, easy to spoil, and generally no major toxicity. The main harm is to eutrophicate the water body, so as to 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 appropriate pretreatment according to the characteristics of water quality, biological treatment is generally suitable for the treatment of wastewater in the food industry.

If the quality of the cracked effluent is very high or the organic matter content in the wastewater is very high, a two-stage aeration tank or a two-stage biological filter can be used, or a multi-stage biological turntable or a combination of two biological treatment devices, or an anaerobic-aerobic series biological treatment system can also be used.

1. Physical treatment:

The wastewater treatment method of insoluble suspended pollutants (including oil film and oil beads) in the wastewater can be divided into gravity separation method, centrifugal separation method and sieve filtration interception method by physical action. The treatment method based on the heat exchange principle is also a physical treatment method.

2. Chemical treatment method:

This is a wastewater treatment method that separates, removes, or converts pollutants in a dissolved or colloidal state from wastewater into harmless substances through chemical reactions and mass transfer.

3. Biological treatment method:

Through the metabolic action of microorganisms, the organic pollutants in the wastewater in the form of solutions, colloids and fine suspension are converted into stable and harmless substances. According to the different microorganisms, biological treatment can be divided into two types: aerobic biological treatment and anaerobic biological treatment.