CN116143333A - Nitrogen and phosphorus containing wastewater treatment process - Google Patents

Abstract

The invention discloses a nitrogen and phosphorus containing wastewater treatment process, which comprises the following steps: the organic nitrogen in the wastewater is converted into ammonia nitrogen through the action of aerobic bacteria, and the ammonia nitrogen is converted into nitrate nitrogen and nitrite nitrogen through nitrifying bacteria and nitrosating bacteria; the mixed solution of the aerobic tank is returned to the anoxic tank, and nitrate nitrogen and nitrite nitrogen are denitrified and converted into nitrogen gas which escapes from water through denitrifying bacteria in the anoxic tank; the anaerobic and anoxic treated waste water is treated by an activated sludge method, so that aerobic bacteria degrade organic matters in the waste water into carbon dioxide and water under the condition of oxygen, and ammonia nitrogen is converted into nitrate nitrogen and nitrite nitrogen; the method comprises the steps of pressurizing wastewater to enable water molecules to pass through an R0 membrane, collecting the water molecules through a fresh water collecting pipeline to obtain fresh water, and intercepting salt and macromolecular organic matters in the wastewater in concentrated water.

Description

A process for the treatment of wastewater containing nitrogen and phosphorus

technical field

The invention relates to the field of waste water treatment, in particular to a process for treating waste water containing nitrogen and phosphorus.

Background technique

Sewage treatment methods are divided into physical treatment methods (such as filtration, precipitation, adsorption and air flotation, etc.), chemical treatment (such as chemical coagulation, electrochemical, oxidation, etc.) and biochemical (or biological ) treatment method and combined process treatment method. According to the different sewage water quality and discharge standards, the treatment methods are also different. Physicochemical method: It is a chemical and physical treatment method to remove pollutants in sewage by adding flocculants and coagulants to carry out precipitation or air flotation in specific structures. However, due to the high cost of dosing, the removal of pollutants is not thorough enough, the amount of sludge is large, and it is difficult to further process, this type of method will produce a certain amount of secondary pollution. Generally, it is not used alone, but only as an auxiliary process for biochemical treatment; physical and chemical processes are commonly used. The main methods are: flocculation sedimentation, air flotation, adsorption, filtration, chemical oxidation, etc. Biochemical method: A treatment method that uses the action of microorganisms to degrade and remove organic matter in sewage. Due to its thorough degradation of pollutants, relatively low operating costs, and basically no secondary pollution, it is widely used in sewage treatment. Biochemical treatment is mainly divided into anaerobic and aerobic. Anaerobic includes: hydrolytic acidification, UASB, etc.; good Oxygen mainly includes: biofilm method, activated sludge method, etc.

In the nitrogen and phosphorus zero discharge project, the final wastewater needs to be evaporated and concentrated, and the operation cost of the evaporation system is very high, so the wastewater must be pretreated before entering the system to minimize the amount of wastewater entering the system.

In addition to the evaporation process, membrane concentration can also be used, but this process has a limitation: the concentration of organic matter entering the system must be lower than 100mg/L, so it is necessary to set up a pretreatment system at the front end to reduce the concentration of organic matter in the wastewater.

Contents of the invention

The invention overcomes the deficiencies of the prior art and provides a process for treating wastewater containing nitrogen and phosphorus.

In order to achieve the above object, the technical solution adopted in the present invention is: a process for treating nitrogenous and phosphorus-containing wastewater, which is characterized in that it includes the following steps: S1: the organic nitrogen in the wastewater is converted into ammonia nitrogen through the action of aerobic bacteria, and the ammonia nitrogen is passed through Nitrifying bacteria and nitrosifying bacteria convert it into nitrate nitrogen and nitrite nitrogen; S2: return the mixed solution of the aerobic tank to the anoxic tank, and convert the nitrate nitrogen and nitrite nitrogen through the denitrifying bacteria in the anoxic tank Nitrate nitrogen denitrification is converted into nitrogen and escapes from the water; S3: The wastewater after anaerobic and anoxic treatment is then activated sludge method, so that aerobic bacteria can degrade the organic matter in the wastewater into Carbon dioxide and water, convert ammonia nitrogen into nitrate nitrogen and nitrite nitrogen, and increase the sludge concentration through the biochemical system of the MBR membrane pool, and increase the volume load of the biochemical system; S4: Pressurize the wastewater so that water molecules pass through R0 The membrane is used to collect fresh water through the fresh water collection pipe, and the salt and macromolecular organic matter in the wastewater are trapped in the concentrated water, which is collected through the concentrated water collection pipe to obtain the concentrated water.

In a preferred embodiment of the present invention, a safeguard device is installed before the wastewater enters R0 to avoid the increase of COD and SS concentrations caused by the abnormality of the MBR membrane pool.

In a preferred embodiment of the present invention, the protection device adopts an activated carbon filter to remove a part of organic matter and SS.

In a preferred embodiment of the present invention, the RO membrane is a seawater desalination membrane.

In a preferred embodiment of the present invention, the fresh water is further treated by the R0 film and then reused in the closed cooling tower.

In a preferred embodiment of the present invention, the concentrated water is further concentrated through an evaporator.

In a preferred embodiment of the present invention, the evaporator adopts three-effect evaporation, the salt content in the wastewater is concentrated after the wastewater passes through the evaporator, and the concentrated saline wastewater is crystallized into salt through a crystallization device.

The present invention solves the defect existing in the background technology, and the present invention has the following beneficial effects:

Before the waste water is concentrated, the present invention uses a biochemical method to remove organic matter, and by setting an anoxic pool in the biochemical system, the concentration of total nitrogen is reduced through the action of denitrifying bacteria, thereby reducing the concentration of organic matter in the waste water entering the membrane concentration system. The invention uses the MBR membrane tank to replace the traditional secondary sedimentation tank and biological filler to increase the sludge concentration of the biochemical system and increase the volume load of the biochemical system.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments recorded in the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work;

Figure 1 is a process flow diagram of a preferred embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Reference to a particular feature, structure, or characteristic described in connection with the embodiments is included in at least some, but not necessarily all, embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Embodiment one

The present invention is a nitrogen and phosphorus zero discharge project. The final waste water needs to be evaporated and concentrated, and the operating cost of the evaporation system is very high. Therefore, the waste water must be pretreated before entering the system to minimize the amount of waste water entering the system. Except for the evaporation process , the best concentration process is to use membrane concentration, but this process has a limitation: the concentration of organic matter entering the system must be lower than 100mg/L, so it is also necessary to set up a pretreatment system at the front end to reduce the concentration of organic matter in the wastewater .

In the wastewater of the present invention, the concentration of comprehensive organic matter is relatively high, and the operation cost of using physical and chemical means is relatively high, and the COD cannot be reduced to below 100 mg/L. The present invention uses a biochemical method to remove organic matter. Due to the high concentration of organic matter, it is necessary to remove a large part of the organic matter in the wastewater by setting up a high-load aerobic pool or an efficient anaerobic pool. Due to the factors of the previous planning and the site, it is preferred to use a high-load aerobic method. To remove part of the total nitrogen contained in the wastewater, in order to reduce the pressure of the subsequent R0 system, an anoxic pool is set in the biochemical system to reduce the concentration of total nitrogen through the action of denitrifying bacteria. The main principle is that the organic nitrogen in the wastewater is converted into ammonia nitrogen through the action of aerobic bacteria, and the ammonia nitrogen is converted into nitrate nitrogen and nitrite nitrogen through nitrifying bacteria and nitrosifying bacteria, and then the mixed solution of the aerobic tank is returned to the The anoxic tank, through the denitrifying bacteria in the anoxic tank, denitrifies nitrate nitrogen and nitrite nitrogen into nitrogen and escapes from the water, thereby reducing the total nitrogen concentration of the wastewater.

The concentration of organic matter in the wastewater after anaerobic and anoxic treatment is still high, and the wastewater needs to be further treated, followed by aerobic treatment. Preferably, the aerobic process adopts the activated sludge method. The main principle is that aerobic bacteria degrade the organic matter in the wastewater into carbon dioxide and water under the condition of oxygen, and convert ammonia nitrogen into nitrate nitrogen and nitrite nitrogen.

In some embodiments where the site is limited, the present invention subsequently uses MBR membrane tanks to replace traditional secondary sedimentation tanks and biological fillers to increase the sludge concentration of the biochemical system and increase the volume load of the biochemical system.

After being treated by the biochemical system, the COD concentration is lower than 100mg/L, and the wastewater needs to pass through the RO membrane to concentrate the concentration of salt and organic matter in the wastewater to reduce the amount of wastewater entering the evaporation system. In order to ensure the service life of RO and the stability of operation, a safeguard device needs to be installed before the wastewater enters R0 to avoid the abnormal operation of the R0 system caused by the sudden increase of COD and SS concentrations due to abnormal conditions in the MBR membrane pool. What needs to be explained Yes, COD is chemical oxygen demand, SS is suspended solids, and the composition of SS above 0.1 micron is generally very complex: sediment, protozoa, baths, bacteria, etc.

The present invention adopts activated carbon filter to filter waste water to remove a part of organic matter and SS.

Due to the high salt content of the waste water, it is difficult for ordinary R0 membranes to separate a large amount of fresh water, so the present invention uses desalination membranes to concentrate the waste water. The working principle is: the waste water is pressurized so that the water molecules pass through the R0 membrane and are collected through the fresh water collection pipe to obtain fresh water. The salt and macromolecular organic matter in the waste water are trapped in the concentrated water and collected through the concentrated water collection pipe. Strong water. After the fresh water is further treated by the R0 membrane, the quality of the fresh water is better than that of tap water, which meets the requirements for reuse and can be reused in closed cooling towers. Concentrated water is further concentrated by evaporator.

The evaporator of the present invention adopts three-effect evaporation, the salt content in the waste water is concentrated after the waste water passes through the evaporator, and the concentrated saline waste water is crystallized into salt through a crystallization device.

The sludge formed by the system is discharged to the sludge concentration tank for concentration, and the concentrated sludge is further dehydrated through a filter press. It should be noted that the treatment of crystallized salt and sludge after dehydration will not be further described here.

In addition, it needs to be additionally explained that for waste water that does not contain nitrogen and phosphorus, the main pollutants of this waste water are organic matter, which does not contain nitrogen and phosphorus, and its biochemical properties are good, and the concentration of pollutants is not high. The concentration of organic matter in wastewater can be treated up to the standard.

The wastewater has a high concentration of organic matter and good biodegradability. First, most of the BOD is degraded through the aerobic pool, and the remaining part of the organic matter that is difficult to degrade is hydrolyzed into small molecular organic matter through the hydrolytic acidification pool to further improve the biodegradability of the waste water. Biochemical, and then set up an aerobic pool to further remove the organic matter of the wastewater through aerobic bacteria. The organic matter in the wastewater is mainly decomposed into carbon dioxide and water by the aerobic bacteria in the aerobic tank. After aerobic treatment, the organic matter in the wastewater can be discharged up to the standard.

When the site is limited, it is necessary to increase the pollutant load per unit pool volume. In this case, the sludge concentration is increased by installing fillers in the biochemical pool and MBR pools at the end, thereby increasing the pollutant load per unit pool volume.

In addition, for R&D wastewater, the main pollutants of this wastewater are total nitrogen and total phosphorus. The total phosphorus is mainly separated and removed from the wastewater by forming phosphate precipitates through the precipitation of the dosing reaction. A phosphorus removal reaction sedimentation tank is installed at the front end and the end respectively to ensure that the total phosphorus discharge of the system meets the standard. The removal of total nitrogen mainly considers the biological denitrification method, which has a low operating cost. It mainly converts ammonia nitrogen into nitrate nitrogen through nitrifying bacteria in the aerobic tank, and then converts nitrate nitrogen through denitrifying bacteria in the anoxic tank. It is nitrogen, which escapes from the wastewater to achieve the purpose of biological denitrification. The total nitrogen concentration in this case is high, and it is difficult to ensure that the total nitrogen in the effluent reaches the standard through the first-level A/0 (anoxic + aerobic). Therefore, two levels are set. The way of A/0 series is used for biological denitrification. Considering that part of the total nitrogen exists in the wastewater in the form of organic nitrogen (such as protein, etc.), after the first-level A/0 treatment, part of the protein has not been degraded. The hydrolysis of protein into small molecular nitrogen-containing organic matter is beneficial to the subsequent aerobic pool to convert it into nitrate nitrogen, ensuring that the final total nitrogen of wastewater can meet the discharge standard.

With the biochemical treatment process, sludge cracking will occur during the operation, which will cause the COD index of the system effluent to exceed the standard. Another function of setting up the last reaction sedimentation tank is to flocculate this part of the cell lysate suspended in the effluent by adding a small amount of chemicals. Formed into agglomerates, they settle at the bottom of the sedimentation tank through their own gravity to ensure that the final organic matter in the effluent is discharged stably and up to standard.

The above is inspired by the ideal embodiment of the present invention. Through the above description, relevant personnel can make various changes and modifications within the scope of not departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the content in the specification, and must be determined according to the scope of the claims.

Claims (7)

1. The nitrogen and phosphorus containing wastewater treatment process is characterized by comprising the following steps of:

s1: the organic nitrogen in the wastewater is converted into ammonia nitrogen through the action of aerobic bacteria, and the ammonia nitrogen is converted into nitrate nitrogen and nitrite nitrogen through nitrifying bacteria and nitrosating bacteria;

s2: the mixed solution of the aerobic tank is returned to the anoxic tank, and nitrate nitrogen and nitrite nitrogen are denitrified and converted into nitrogen gas which escapes from water through denitrifying bacteria in the anoxic tank;

s3: the anaerobic and anoxic treated wastewater is reused by an activated sludge method, so that aerobic bacteria degrade organic matters in the wastewater into carbon dioxide and water under the condition of oxygen, ammonia nitrogen is converted into nitrate nitrogen and nitrite nitrogen, and the sludge concentration is increased through an MBR membrane tank biochemical system, so that the volume load of the biochemical system is enhanced;

s4: the wastewater is pressurized, so that water molecules pass through the R0 membrane and are collected through a fresh water collecting pipeline to obtain fresh water, salt and macromolecular organic matters in the wastewater are trapped in concentrated water, and the concentrated water is collected through a concentrated water collecting pipe to obtain concentrated water.

2. The process for treating wastewater containing nitrogen and phosphorus according to claim 1, wherein the process comprises the following steps: a guarantee device is arranged before wastewater enters R0, so that the increase of COD and SS concentration caused by the abnormality of an MBR membrane tank is avoided.

3. The process for treating wastewater containing nitrogen and phosphorus according to claim 2, wherein the process comprises the following steps: the guarantee device adopts an activated carbon filter for removing a part of organic matters and SS.

4. The process for treating wastewater containing nitrogen and phosphorus according to claim 1, wherein the process comprises the following steps: the R0 membrane adopts a seawater desalination membrane.

5. The process for treating wastewater containing nitrogen and phosphorus according to claim 1, wherein the process comprises the following steps: the fresh water is reused in the closed cooling tower after being further treated by the R0 film.

6. The process for treating wastewater containing nitrogen and phosphorus according to claim 1, wherein the process comprises the following steps: the concentrate is further concentrated by an evaporator.

7. The process for treating wastewater containing nitrogen and phosphorus according to claim 6, wherein the process comprises the following steps: the evaporator adopts triple effect evaporation, salt in the wastewater is concentrated after the wastewater passes through the evaporator, and the concentrated salt-containing wastewater is crystallized into salt through the crystallization device.

Images