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What are the methods for ammonia nitrogen wastewater treatment?

Time : 2020-04-15

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What are the methods for ammonia nitrogen wastewater treatment?

What should I do with the ammonia nitrogen wastewater treatment? In the following article, Making Green Environmental Protection introduces you to the relevant ammonia nitrogen wastewater treatment methods. Let's go to understand it together.
 
Folding materialization
Blow-off method
Under alkaline conditions, a method of separation using the gas-liquid equilibrium relationship between the gas-phase concentration and the liquid-phase concentration of ammonia nitrogen is generally considered to be related to temperature, pH, and gas-liquid ratio.


2. Zeolite deamination method
The cations in the zeolite are exchanged with the NH4+ in the wastewater to achieve the purpose of nitrogen removal. The application of zeolite deamination method must consider the regeneration of zeolite, there are usually regeneration liquid method and incineration method. When the incineration method is used, the generated ammonia gas must be treated. This method is suitable for the treatment of low-concentration ammonia nitrogen wastewater. The content of ammonia nitrogen should be 10--20mg / L.


3. Membrane separation technology
A method for ammonia nitrogen removal using the selective permeability of the membrane. This method is easy to operate, has a high recovery rate of ammonia nitrogen, and has no secondary pollution. For example: gas-water separation membrane to remove ammonia nitrogen. Ammonia nitrogen has a dissociation equilibrium in water. With the increase of pH, the proportion of ammonia in water NH3 form increases. At a certain temperature and pressure, the gaseous and liquid states of NH3 reach equilibrium. According to the principle of chemical equilibrium movement, the principle of A.L.LE Chatelier. In nature, all balances are relative and temporary. Chemical equilibrium can only be maintained under certain conditions. "If one of the conditions of the equilibrium system is changed, such as concentration, pressure, or temperature, the equilibrium moves in a direction that can weaken this change." Following this principle, the following design concepts were carried out in the membrane One side is high concentration ammonia nitrogen wastewater, and the other side is acidic aqueous solution or water. When the left temperature T1> 20 ℃, PH1> 9, P1> P2 maintain a certain pressure difference, then the ion ammonia NH4 + in the wastewater becomes free ammonia NH3, and diffuses to the membrane surface through the raw material liquid side interface, in the membrane Under the effect of the surface partial pressure difference, it passes through the pores of the membrane and enters the absorption liquid, and quickly reacts with H + in the acidic solution to form an ammonium salt.


4. MAP precipitation method
Mainly use the following chemical reaction: Mg2 ++ NH4 ++ PO43- = MgNH4PO4
In theory, phosphorus and magnesium salts are added to wastewater containing high concentrations of ammonia nitrogen at a certain ratio. When [Mg2 +] [NH4 +] [PO43-]> 2.5 × 10–13, magnesium ammonium phosphate (MAP) is generated Remove ammonia nitrogen from wastewater.


5. Chemical oxidation
A method to remove ammonia nitrogen directly into nitrogen by strong oxidant. Inflection point chlorination is the use of ammonia in the water to react with chlorine to generate ammonia deamination. This method can also play a sterilizing role, but the residual chlorine produced will affect the fish, so it must be equipped with a facility to remove residual chlorine.


Folding biological denitrification
Traditional and newly developed denitrification processes include A / O, two-stage activated sludge process, strong oxidation aerobic biological treatment, short-range nitrification and denitrification, and ultrasonic blow-off treatment ammonia nitrogen method.


1. The A / O process connects the anoxic section in the front section and the aerobic section in the rear section in series. The DO in section A is not greater than 0.2 mg / L, and the DO in section O is 2 to 4 mg / L. Heterotrophic bacteria in the anoxic zone hydrolyze suspended pollutants such as starch, fiber, carbohydrates, and soluble organic matter in sewage into organic acids, so that macromolecular organic matter is decomposed into small molecular organic matter, and insoluble organic matter is converted into soluble organic matter. When the products of anoxic hydrolysis enter the aerobic tank for aerobic treatment, the biodegradability of the sewage is improved, and the efficiency of oxygen is improved; in the anoxic zone, heterotrophic bacteria ammoniate protein, fat and other pollutants (N on the organic chain) Or amino groups in amino acids) free ammonia (NH3, NH4 +), under sufficient oxygen supply, the nitrification of autotrophic bacteria oxidizes NH3-N (NH4 +) to NO3-, and returns to A pool through reflux control. Under oxygen conditions, the denitrification of isoxic bacteria reduces NO3- to molecular nitrogen (N2) to complete the circulation of C, N and O in the ecology and realize the harmless treatment of sewage. Its characteristic is that the organic carbon in the sewage is used by the denitrifying bacteria in front of the anoxic tank, which can reduce the organic load of the subsequent aerobic tank. The alkalinity generated by the denitrification reaction can compensate for the alkali in the aerobic tank. Degree of demand. After the aerobic tank is anoxic, the residual organic pollutants in denitrification can be further removed, and the effluent quality can be improved. The removal rate of BOD5 is higher than 90 ~ 95%, but the effect of nitrogen and phosphorus removal is slightly worse, the nitrogen removal efficiency is 70 ~ 80%, and the phosphorus removal is only 20 ~ 30%. Nevertheless, because the A / O process is relatively simple and has its outstanding characteristics, it is still a more commonly used process.


2. The two-stage activated sludge method can effectively remove organic matter and ammonia nitrogen, of which the second stage is in the delayed aeration stage, the residence time is about 36 hours, the sewage concentration is below 2g / l, no or less sludge Thereby reducing the cost of sludge treatment.


3. The typical representative of strong oxidation aerobic biological treatment is powder activated carbon method (PACT process)


The main feature of the powder activated carbon method is that the powder activated carbon (PAC) is added to the aeration tank to utilize the extremely developed microporous structure of the powder activated carbon and greater adsorption capacity, so that dissolved oxygen and nutrients are enriched on its surface for adsorption The microorganisms on the PAC provide a good living environment to increase the degradation rate of organic matter.
In recent years, a number of new denitrification processes have appeared at home and abroad, which provide a new way for the denitrification of high-concentration ammonia nitrogen wastewater. There are short-range nitrification and denitrification, aerobic denitrification and anaerobic ammonia oxidation.


4. Short-range nitrification and denitrification
Biological nitrification and denitrification is a more common method of nitrogen removal. It is a more economical method of removing ammonia nitrogen in water. Its principle is to simulate the nitrogen cycle in the natural ecological environment. The combined effect of nitrifying bacteria and denitrifying bacteria is Ammonia nitrogen is converted into nitrogen to achieve the purpose of nitrogen removal. Due to the large amount of oxygen required in the ammonia nitrogen oxidation process, the aeration cost becomes the main expense of this denitrification method. Short-range nitrification and denitrification is to control the oxidation of ammonia nitrogen in the nitrification stage, and then to perform denitrification, eliminating the two steps of oxidizing nitrite to nitrate and then reducing it to nitrite in traditional biological denitrification (Nitrite nitrogen is denitrified). This technology has great advantages: ① save 25% oxygen supply and reduce energy consumption; ② reduce the carbon source by 40%, and achieve denitrification and denitrification under low C / N; ③ shorten the reaction process and save 50 % Of the denitrification tank volume; ④ reduce the sludge output, the sludge production can be reduced by about 33% ~ 35%, and the sludge production during the denitrification stage is about 55%. The key to realizing short-term nitrification and denitrification biological denitrification technology is to control nitrification in the nitrite stage and prevent further oxidation of nitrite.


5. Anaerobic ammonia oxidation (ANAMMOX) and autotrophic denitrification (CANON)
Anaerobic ammonia oxidation refers to the process in which ammonia nitrogen is directly oxidized to nitrogen using nitrite as the electron acceptor under anaerobic conditions.


Anaerobic ammonia oxidation (Anaerobicammoniaoxidation, ANAMMOX) refers to the microorganisms represented by Plantomycetalessp under anaerobic conditions directly using NH4 + as the electron donor and NO2- or NO3- as the electron acceptor, and NH4+, NO2- or NO3-Biooxidation process converted to N2. This process uses a unique biological body to convert nitrate nitrogen to N2 using nitrate as the electron donor, which achieves the cyclic anaerobic nitrification of N to a large extent. This coupled process is very useful for the removal of nitrogen from anaerobic nitrification wastewater Good prospects, for the high ammonia nitrogen and low COD wastewater due to partial oxidation of nitrate, greatly save energy. At present, it is speculated that there are multiple ways of anaerobic ammonia oxidation. One of them is the reaction of hydroxylamine and nitrite to form N2O, and N2O can be further converted into nitrogen, and ammonia is oxidized to hydroxylamine. The other is the reaction of ammonia and hydroxylamine to form hydrazine. Hydrazine is converted into nitrogen and generates four reducing [H]. The reducing [H] is passed to the nitrite reduction system to form hydroxylamine. The third is: on the one hand, nitrite is reduced to NO, NO is reduced to N2O, and N2O is reduced to N2; on the other hand, NH4+ is oxidized to NH2OH, and NH2OH is converted to N2 through N2H4, and N2H2. The advantages of the anaerobic ammonia oxidation process: it can greatly reduce the oxygenation energy consumption of the nitrification reaction; it eliminates the external electron donor of the denitrification reaction; it can save the neutralizing reagents required in the traditional nitrification and denitrification reaction process; The amount of sludge is very small. The shortcomings of anaerobic ammonia oxidation are: so far, the reaction mechanism of anaerobic ammonia oxidation, the involved bacteria and various operating parameters are not clear.


The whole process of autotrophic denitrification is completed in one reactor, and its mechanism is still unclear. Hippen et al. Found that more than 60% of the ammonia nitrogen was converted to N2 and removed by limiting dissolved oxygen (DO concentration 0.8 · 1.0 mg / l) and without adding an organic carbon source. At the same time, Helmer et al. Proved through experiments that at low DO concentrations, bacteria use nitrite ion as the electron acceptor, ammonium ion as the electron donor, and the product is nitrogen. Experiments have used fluorescent in situ hybridization technology to monitor microorganisms in the autotrophic denitrification reactor, and found that even when the reactor is in a stable stage, even in the case of restricted aeration, there are still active anaerobic ammonia oxidizing bacteria in the reactor , There is no nitrifying bacteria. 85% of the ammonia nitrogen is converted to nitrogen. In view of the above theory, the whole process of autotrophic nitrogen removal may include two steps. The first is the oxidation of part of the ammonia nitrogen to nitrite, and the second is the anaerobic ammonia oxidation.


6. Aerobic denitrification
Traditional denitrification theory holds that denitrifying bacteria are facultative anaerobic bacteria, and their respiratory chain uses oxygen as the terminal electron acceptor under aerobic conditions and nitrate as the terminal electron acceptor under anoxic conditions. Therefore, if denitrification is carried out, it must be under anoxic environment. In recent years, the phenomenon of aerobic denitrification has been continuously discovered and reported, which has gradually attracted people's attention. Some aerobic denitrifying bacteria have been isolated, and some can simultaneously perform aerobic denitrification and heterotrophic nitrification (such as Tpantotropha.LMD82.5 isolated and screened by Robertson et al.). In this way, real synchronous nitrification and denitrification can be realized in the same reactor, which simplifies the technological process and saves energy.


7. Ultrasonic blowing off treatment of ammonia nitrogen
Ultrasonic stripping method to remove ammonia nitrogen is a new type of high-concentration ammonia nitrogen wastewater treatment technology. It is based on the traditional method of stripping, introducing ultrasonic radiation wastewater treatment technology, a combination of ultrasonic and stripping technology derived from The method of handling ammonia nitrogen. The combination of these two methods not only improves the problem of high cost of ultrasonic treatment of wastewater, but also makes up for the shortcomings of traditional blow-off technology to remove poor ammonia nitrogen. The super-steam blow-off method can ensure the effect of treating ammonia nitrogen and can also treat organic matter in wastewater The degradation of the product plays a certain role in improving. Technical characteristics (1) The high concentration ammonia nitrogen wastewater adopts the high-tech ultrasonic denitrification technology in the 1990s. Its total denitrification efficiency is 70 ~ 90%, no chemical agents, no heating, low treatment cost, and treatment effect stable. (2) The biochemical treatment adopts the periodic activated sludge method (CASS) process, the construction cost is low, it has a unique biological denitrification function, the treatment cost is low, the treatment effect is stable, the load impact resistance is strong, and the phenomenon of sludge expansion does not occur. The nitrogen removal efficiency is greater than 90% to ensure that the ammonia nitrogen meets the standard.


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