CN1626464A

CN1626464A - Method for treating carbonized sewage through cultivating and domesticating nitrobacterium and denitrified bacterium

Info

Publication number: CN1626464A
Application number: CN 200310111176
Authority: CN
Inventors: 曹吉良; 毛云海; 郭启鸿; 栾春生
Original assignee: KUNMING STEELS CO Ltd
Current assignee: KUNMING STEELS CO Ltd
Priority date: 2003-12-08
Filing date: 2003-12-08
Publication date: 2005-06-15

Abstract

A process for treating the coking sewage by culturing and naturalizing the nitrifying bacteria and the denitrifying bacteria is disclosed. The process for culturing and naturalizing the denitrifying bacteria includes filling the mixed liquid from aerobic pool into anaerobic pool, flowing the supernatant from depositing pool back into anaerobic pool, inoculating denitrifying bacteria, culturing and naturalizing. The process for culturing and naturalizing the nitrifying bacteria includes introducing the nitrogen-contained sewage to aerobic pool, culturing naturalizing.

Description

Method for treating coking sewage by culturing and acclimating nitrifying and denitrifying bacteria

Technical Field

The invention relates to a sewage treatment method, in particular to a method for treating sewage of a coking plant by culturing, domesticating nitrifying and denitrifying bacteria by utilizing original common activated sludge.

Background

Biological thresherNitrogen is ammonia Nitrogen (NH) in wastewater by utilizing chemical principle₄ ⁺) Finally, the ammonia nitrogen is converted into harmless nitrogen and removed through nitration and denitrification reactions. Nitrification is the entire process of converting ammonia nitrogen to the nitrate form. Namely, it is The reactions are carried out by means of heterotrophic and autotrophic bacteria, which produce in natural environment a large amount of nitrates and nitrifying bacteria, which for their own growth require the production of energy-a carbon source (i.e.CO-from the oxidation of inorganic substances₂Or a carbonate). Therefore, the nitrification is to utilize nitrifying bacteria to nitrify NH under aerobic conditions₄ ⁺The oxidation of N to nitrite and nitrate. The reaction formula is as follows:

the overall reaction formula is:

at NH₄ ⁺The oxidation of-N requires a large amount of alkalinity (HCO)₃ ^-) Oxidizing 1 mg of NH₄ ⁺Consumption of 8.64 mg HCO for-N₃ ^-A small fraction of which is incorporated into the cellular material, most serve to neutralize the hydrogen ions released during oxidation. Per mg NH₄ ⁺Oxidation of-N to NO₃ ^-4.33 mg of oxygen was required for-N.

Denitrification is the reaction of Nitrate (NO) under anoxic conditions₃ ^-) And Nitrite (NO)₂ ^-) Reducing to gaseous nitrogen (N)₂) The process of (1). The bacteria involved in this process are called denitrifying bacteria, most of which are Pseudomonas (heterotrophic bacteria), typically gram-negative bacteria. The bacteria are heterotrophic facultative bacteria, and can make ammonia Nitrogen (NH) under the condition of aerobic and inorganic carbon sources₃-N) to NO₂ ^-And NO₃ ^-. While under non-oxidizing conditions they utilize NO₂ ^-And NO₃ ^-Performing anaerobic respiration with NO₂ ^-And NO₃ ^-The oxygen in the carbon source is used as an oxygen source to complete the oxidation of organic matters (carbon sources) and simultaneously react with NO₂ ^-And NO₃ ^-Reduction to N₂. The reaction formula is as follows:

as can be seen from the reaction, the reaction is carried out in the absence of oxygen and in the presence of a sufficient carbon source. The principle is utilized in industrial production to achieve the aim of final denitrification. Because, nitrogen and phosphorus are main factors causing eutrophication of water bodies. Industrial sewage, especially coking sewage, contains a large amount of ammonia Nitrogen (NH)₄ ⁺) It consumes oxygen in water to produce nitrate Nitrogen (NO)₃ ^--N) or nitrous Nitrogen (NO)₂ ^--N) to cause a sharp drop in dissolved oxygen in the water, eventually resulting in contamination of the water body. Chinese patent 89107208 discloses a method and equipment for denitrifying high-nitrogen-content sewage. The method comprises the steps of firstly introducing nitrogen-containing sewage into a denitrification device, then introducing the nitrogen-containing sewage into a nitrification device, finally introducing the nitrogen-containing sewage into a sedimentation tank for sedimentation and then discharging the nitrogen-containing sewage, refluxing sludge in the sedimentation tank to the nitrification device, and refluxing part of supernatant water in the sedimentation tank to the denitrification device so as to enable nitrification and denitrification to be in the optimal denitrification state. However, if there are not enough biological bacteria in the nitrification and denitrification processes or additional biological bacteria are required, denitrification in a preferable state cannot be achieved. Therefore, there is a need for improvements in the prior art.

Disclosure of Invention

The invention aims to provide a method for effectively treating coking sewage by culturing and domesticating sufficient nitrifying bacteria and denitrifying bacteria for the nitrification and denitrification processes by utilizing the self process flow of sewage treatment in a short time.

The method provided by the invention comprises the following steps: introducing nitrogen-containing sewage into a denitrification process, introducing a nitrification process after treatment, and finally introducing a precipitation process, wherein part of sludge in the precipitation process flows back to the nitrification process, and part of supernatant water in the precipitation process flows back to the denitrification process, and the method is characterized in that:

a. firstly, the mixed liquid of the aerobic tank in the nitration process is filled into the anoxic tank in the denitrification process, and then the mixed liquid is mixed by 80-120m³Refluxing the supernatant of the sedimentation tank to an anoxic tank at the flow rate of/h, circulating the sludge in the tank for at least 120 hours, allowing microorganisms in the sludge to adhere to a filler in the tank, completing inoculation of denitrifying bacteria, controlling the dissolved oxygen in the tank to be below 0.5mg/L, controlling the pH value to be 7-8, and culturing and domesticating the denitrifying bacteria at the temperature of 25-30 ℃;

b. introducing nitrogen-containing sewage into an aerobic tank in the nitration process, controlling COD (chemical oxygen demand) in a mixed solution of the aerobic tank to be less than 500mg/L, ammonia nitrogen to be less than 50mg/L, dissolved oxygen concentration to be 3-5mg/L, pH value to be 7-9, temperature to be 20-35 ℃, P (phosphorus) content to be 4-5mg/L and alkalinity to be 80-150mg/L, and culturing and domesticating nitrobacteria.

In the process a, the reflux ratio of supernatant in the sedimentation tank to the anoxic tank is 2-4: 1.

Na can be added into the aerobic tank₂CO₃(sodium carbonate) to adjust the pH of the mixture to 7-7.5 and the alkalinity to 80-150 mg/L.

In the process of researching and utilizing the common activated sludge of the sewage treatment system to inoculate and domesticate nitrobacteria capable of oxidizing ammonia nitrogen into nitrate and nitrite and denitrifying bacteria capable of reducing the nitrate and nitrite into gaseous nitrogen, the following problems are mainly solved:

1. as the primary condition for culturing and domesticating denitrifying bacteria, the invention needs to have abundant and easily degradable organic matters as carbon source and energy source, therefore, the invention sets a pre-denitrification process and fully utilizes the organic matters in the nitrogen-containing sewage as the carbon source (CO)₂Or carbonate) while supplying NO to denitrifying bacteria using the returned sewage₃ ^-。

2. Due to O₂Has inhibitory effect on nitrate reductase activity, and NO₃ ^-And O₂The difference of oxidation-reduction potential of the bacteria can cause the denitrifying bacteria to preferentially select O₂But not NO₃ ^-Therefore, the dissolved oxygen in the anoxic tank must be controlled to be below 0.5 mg/L.

3. The nitrifying bacteria are high aerobic bacteria, have the advantages of self-oxygen specialization and high sensitivity to the existence of organic matters, and can inhibit the nitrifying bacteria when the concentration of the organic matters or the concentration of ammonia nitrogen exceeds a certain amount, so that only a small amount of nitrogen-containing sewage can be doped, and COD (chemical oxygen demand) in mixed liquid of an aerobic pool is less than 400mg/L and the concentration of ammonia nitrogen is less than 40 mg/L.

4. Nitrifying bacteria oxidize a large amount of NH₄ ⁺Or NO₂ ^-To obtain sufficient energy for growth and therefore sufficient dissolved oxygen must be available in the aerobic tank. When the dissolved oxygen is less than 0.5mg/l, the nitrification reaction tends to stop, and as the dissolved oxygen concentration increases, the nitrification rate also increases. So that the dissolved oxygen concentration of the mixed liquid in the aerobic tank is controlled to be 3-5 mg/L.

5. The temperature has great influence on the growth and nitrification rate of nitrifying bacteria, the nitrifying bacteria can grow in the range of 4-45 ℃, but the optimal temperature is 25-35 ℃. The system has the advantages that the water temperature of the aerobic pool in winter is 20-24 ℃, the water temperature in summer is 27-32 ℃, the aerobic pool is relatively stable, and the growth and nitrification rate of the nitrifying bacteria are relatively ideal.

6. The optimum pH value of the nitrifying bacteria is 8.5, and when the pH value is lower than 7, the nitrification rate is obviously reduced; however, when the pH is adjusted to be too high, the required alkalinity is large, and the running cost is increased. Therefore, the pH value is controlled within the range of 7-7.5, the nitrobacteria are adaptive to the environment with low pH value, and the purpose is to reduce Na₂CO₃(amount of sodium carbonate) added.

7. C, N, P the proportion coordination of nutrient elements is an important condition for the growth of nitrobacteria, the P nutrient elements in the coking wastewater are less, and the phosphorus salt must be added to regulate the P (phosphorus) content of the mixed liquor in the aerobic pool within the range of 4-5 mg/L.

8、Na₂CO₃The adding amount of the (sodium carbonate) can be determined according to the PH value and the alkalinity of the mixed liquor of the aerobic tank, and the aim is to adjust the PH value to 7-7.5The alkalinity is controlled in the range of 80-150 mg/L.

The invention has the following advantages and effects: due to the scheme, the nitrifying bacteria capable of oxidizing ammonia nitrogen into nitrate and nitrite and the denitrifying bacteria capable of reducing nitrate and nitrite into gaseous nitrogen can be inoculated and domesticated by utilizing the common activated sludge of the sewage treatment system, so that the domestication link can be reduced, the culture time can be shortened, the nitrifying bacteria and the denitrifying bacteria required by sewage treatment can be fully met, the operation cost can be reduced, and the treated coking sewage can completely reach the national specified discharge standard. Table 1 shows the data relating to the treatment of sewage from a coke-oven plant by the prior art process and the process of the present invention. Table 2 shows the data obtained for the treatment of the sewage from a coking plant by the process of the invention. NO in aerobic tank₃ ^--N and NO₂ ^-The variation of-N is shown in figure 2, and water NH is fed into the aerobic tank₃-N and effluent NH₃The variation of-N is shown in FIG. 3.

Drawings

FIG. 1 is a process flow diagram of the present invention;

FIG. 2 shows NO in the aerobic tank₃ ^--N and NO₂ ^--a change in N;

FIG. 3 shows the inlet water NH in the aerobic tank₃-N and effluent NH₃-variation of N.

Detailed Description

The invention is further described with reference to specific examples.

Example 1

1. The sewage generated in the production process of each workshop is intensively discharged into an oil removal tank, and heavy oil and partial light oil are removed;

2. the effluent of the oil removal tank automatically flows into a flotation tank for oil removal again, so that a good water quality condition is created for the next procedure; when the water quality is poor or the water quantity is large, the water discharged from the oil removal tank enters a regulating tank, and is pumped back to the oil removal tank when the load of the subsequent process is reduced;

3. the effluent of the flotation tank automatically flows into a neutralization tank, phosphorus salt is added according to the requirement to be mixed with the wastewater, the amount of phosphorus (P) is controlled to be 4-5mg/L, and then the mixture is sent into an anaerobic tank;

4. the anaerobic tank is internally provided with a combined filler and a stirrer, and the wastewater is fully stirred to carry out acidification reaction with a biological film (anaerobic bacteria) on the combined filler in the tank, so that a part of harmful substances are degraded, and meanwhile, the biodegradability of the sewage is improved, and favorable conditions are created for the next-stage treatment;

5. the effluent of the anaerobic tank automatically flows to a suction well for later use;

6. firstly, filling the mixed liquid in the aerobic pool into the anoxic pool, then filling the anoxic pool with the mixed liquid, and filling the anoxic pool with the mixed liquid in a range of 80-120m³Refluxing the supernatant of the sedimentation tank to an anoxic tank at the flow rate of/h, circulating the sludge in the tank for at least 120 hours, allowing microorganisms in the sludge to adhere to a filler in the tank, completing inoculation of denitrifying bacteria, controlling the dissolved oxygen in the tank to be below 0.5mg/L, controlling the pH value to be 7-8, and culturing and domesticating the denitrifying bacteria at the temperature of 25-30 ℃;

7. feeding the sewage in the water absorption well into an anoxic tank, continuously refluxing the supernatant water in the sedimentation tank into the anoxic tank at a reflux ratio of 2-4, taking the organic matters in the inlet water as nitrified carbon source and energy source in the anoxic tank, taking nitrate nitrogen in the reflux water in the sedimentation tank as denitrification oxygen source, and carrying out denitrification reaction under the action of a biofilm facultative bacteria colony on the combined filler in the tank to ensure that NO in the wastewater is subjected to denitrification₃ ^-、NO₂ ^-Reducing the nitrogen to nitrogen and escaping into the atmosphere;

8. the effluent of the anoxic tank flows into the aerobic tank in small amount to make COD less than 500mg/L and ammonia nitrogen less than 50mg/L in the mixed liquor, so as to prevent the excess concentration of organic matters or ammonia nitrogen therein from inhibiting nitrobacteria, and simultaneously, in order to meet the biochemical requirement, air is blown into the aerobic tank to keep the dissolved oxygen concentration within the range of 3-5mg/L, so as to provide oxygen for the microorganisms and stir the mixed liquor, and sodium carbonate (Na) is added according to the requirement₂CO₃) And sodium dihydrogen phosphate (NaH)₂PO₄) Controlling pH value to 7-9, temperature to 20-35 deg.C, P (phosphorus) content to 4-5mg/L, alkalinity to 80-150mg/L, culturing, and domesticatingNitrifying bacteria are dissolved out, so that ammonia nitrogen in the wastewater is oxidized into nitrate nitrogen in the aerobic tank;

9. the effluent of the aerobic tank automatically flows into a sedimentation tank, the mixed solution is subjected to mud-water separation, the supernatant automatically flows into a sewage return pump room and is sent into an anoxic tank through a pump part, and the rest water is sent into a clarification tank for further treatment; most of the separated activated sludge is returned to the aerobic tank as return sludge, and the rest is periodically sent to the sludge tank.

Table 1 units: mg/l

TABLE 2

Claims

1. A method for culturing and domesticating nitrifying and denitrifying bacteria to treat coking sewage includes introducing nitrogen-containing sewage into denitrification process, introducing treated sewage into nitrification process, introducing precipitation process, returning partial sludge to nitrification process, returning partial supernatant water to denitrification process, characterized in that:

2. The method according to claim 1, wherein the reflux ratio of supernatant in the sedimentation tank to the anoxic tank in the process a is 2-4.

3. The method as claimed in claim 1, wherein Na is added to the aerobic tank₂CO₃(sodium carbonate), adjusting the pH value of the mixed solution to 7-7.5 and the alkalinity to 80-150 mg/L.