Method for synchronously removing nitrogen and phosphorus in organic wastewater

Abstract

The invention provides a method for synchronously removing nitrogen and phosphorus in organic wastewater, which comprises the following steps: detecting the concentration of ammonia nitrogen and the concentration of phosphate in the organic wastewater, and adjusting the pH value of the organic wastewater to 8.0-9.5; adjusting the temperature of the organic wastewater to 20-30 DEG C; adding magnesium salt into the mixture; wherein the molar ratio of the addition amount of the magnesium ions to the ammonia nitrogen is (1.0-1.2): 1; the molar ratio of the addition amount of the magnesium ions to the phosphate is (1.0-1.2): 1. A chemical precipitation method is adopted, magnesium salt is added into the organic wastewater rich in ammonia nitrogen and phosphate to serve as an agent, magnesium ammonium phosphate precipitates are generated through a chemical reaction, and therefore the purpose of synchronously removing ammonia nitrogen and phosphate is achieved, and the problem of nitrogen and phosphorus pollution of the organic wastewater is effectively solved; the method for synchronously removing nitrogen and phosphorus in organic wastewater disclosed by the invention has the characteristics of high efficiency, economy and environmental protection, and is easy to popularize and apply.

Description

Technical Field

[0001] The present application relates to the technical field of sewage treatment, and in particular to a method for simultaneously removing nitrogen and phosphorus from organic wastewater. Background Art

[0002] With the rapid development of industrialization and urbanization, the discharge of organic wastewater is increasing. In the organic wastewater generated by many industries, there are often a lot of ammonia nitrogen and phosphate, among which ammonia nitrogen and phosphate are one of the main pollutants that cause eutrophication of water bodies.

[0003] In the related technologies, organic wastewater treatment methods often treat nitrogen and phosphorus separately, or use biological treatment methods for treatment; although some of the related technologies can remove nitrogen or phosphorus, it is difficult to achieve simultaneous and efficient removal of ammonia nitrogen and phosphates, and may also introduce new pollutants; and biological treatment methods have strict requirements on water quality, water temperature, microbial population and other conditions, the treatment effect is unstable, and the area occupied is large and the treatment cost is high. Summary of the invention

[0004] The present application aims to solve at least one of the technical problems in the related art to a certain extent. The present application adopts a chemical precipitation method, by adding magnesium salt as a reagent to organic wastewater rich in ammonia nitrogen and phosphate, and using chemical reaction to generate magnesium ammonium phosphate precipitation, thereby achieving the purpose of simultaneous removal of ammonia nitrogen and phosphate, effectively solving the nitrogen and phosphorus pollution problem of organic wastewater, and the method for simultaneous removal of nitrogen and phosphorus in organic wastewater disclosed in the present application is efficient, economical, and environmentally friendly, and is easy to promote and apply.

[0005] To achieve the above object, a method for simultaneous nitrogen and phosphorus removal in organic wastewater is proposed according to the present application, comprising the following steps:

[0006] Detecting the concentration of ammonia nitrogen and phosphate in the organic wastewater, and adjusting the pH value of the organic wastewater to 8.0-9.5;

[0007] The temperature of the organic wastewater is adjusted to 20°C-30°C; and magnesium salt is added thereto; wherein the amount of magnesium ions added is equal to that of NH4 + The molar ratio is 1.0-1.2:1; the amount of magnesium ion added is related to PO4 3- The molar ratio is 1.0-1.2:1.

[0008] In some embodiments, the concentration of ammonia nitrogen in the organic wastewater is 100-500 mg / L, and the concentration of phosphate is 50-200 mg / L.

[0009] In some embodiments, the magnesium salt includes at least one of magnesium chloride, magnesium sulfate, and magnesium nitrate.

[0010] In some embodiments, the method for adjusting the organic wastewater is to use hydrochloric acid or sodium hydroxide solution for adjustment.

[0011] In some embodiments, the amount of magnesium ions added per liter of organic wastewater is 0.1-0.2 g.

[0012] In some embodiments, after adding magnesium salt to the organic wastewater, the reaction is stirred at a speed of 20 rpm-40 rpm for 0.5-2 hours.

[0013] In some embodiments, the chemical reaction formula for simultaneous nitrogen and phosphorus removal in organic wastewater is:

[0014] Mg 2+ +NH4 + +PO4 3- +6H2O=MgNH4PO4·6H2O↓.

[0015] In some embodiments, the ammonia nitrogen concentration in the treated organic wastewater does not exceed 50 mg / L; the phosphate concentration does not exceed 10 mg / L.

[0016] Compared with the prior art, this application has the following advantages:

[0017] The present application adopts a chemical precipitation method, by adding magnesium salt as a reagent to organic wastewater rich in ammonia nitrogen and phosphate, and utilizing chemical reaction to generate magnesium ammonium phosphate precipitate, thereby achieving the purpose of simultaneously removing ammonia nitrogen and phosphate. The organic wastewater treated by the method of the present application has an ammonia nitrogen removal rate of more than 90%, and a phosphate removal rate of more than 95%. The ammonia nitrogen concentration in the treated organic wastewater can be reduced to below 50 mg / L; the phosphate concentration can be reduced to below 10 mg / L, which can meet the national sewage discharge standards.

[0018] In addition, the magnesium ammonium phosphate precipitate generated by the present application is stable in nature and can be easily separated from organic wastewater by conventional solid-liquid separation methods such as precipitation and filtration. The precipitate can also be recycled as a high-quality slow-release fertilizer to achieve the recycling of resources without causing secondary pollution to the environment. At the same time, in the process of removing ammonia nitrogen and phosphate, the process also has a certain adsorption and co-precipitation removal effect on some organic matter in organic wastewater, which helps to improve the overall water quality of organic wastewater.

[0019] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0021] Figure 1 This is a flow chart of a method for simultaneous removal of nitrogen and phosphorus from organic wastewater in one embodiment of the present application. DETAILED DESCRIPTION

[0022] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be construed as limiting the present application. On the contrary, the embodiments of the present application include all changes, modifications and equivalents that fall within the spirit and connotation of the appended claims.

[0023] like Figure 1 To achieve the above purpose, the present application proposes a method for simultaneously removing nitrogen and phosphorus from organic wastewater, comprising the following steps:

[0024] S1: Detect the concentration of ammonia nitrogen and phosphate in organic wastewater, and adjust the pH value of organic wastewater to 8.0-9.5;

[0025] S2: adjusting the temperature of the organic wastewater to 20°C-30°C; and adding magnesium salt thereto; wherein the molar ratio of the added amount of magnesium ions to ammonia nitrogen is 1.0-1.2:1; and the molar ratio of the added amount of magnesium ions to phosphate is 1.0-1.2:1.

[0026] In S1, the concentration of ammonia nitrogen and the concentration of phosphate in organic wastewater are detected. The organic wastewater in this application includes organic wastewater generated in the fields of food processing, pharmaceuticals, and aquaculture, which often contains a large amount of ammonia nitrogen and phosphate. Ammonia nitrogen and phosphate are one of the main pollutants that cause eutrophication of water bodies. Excessive ammonia nitrogen and phosphate are discharged into the water body, which will cause algae and other plankton to reproduce rapidly, the dissolved oxygen content of the water body will decrease, the water quality will deteriorate, and fish and other organisms will die in large numbers, seriously damaging the water ecological balance. Generally speaking, the concentration of ammonia nitrogen in organic wastewater is 100-500mg / L, and the concentration of phosphate is 50-200mg / L.

[0027] In this step, the pH value of the organic wastewater can be adjusted to 8.0-9.5 using hydrochloric acid or sodium hydroxide solution by a pH meter to ensure that the pH value of the reaction system is stable within the optimal range. For example, the pH value of the organic wastewater is 8.0, 8.1, 8.3, 8.4, 8.5, 8.6, 8.8, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, etc.; when the pH value is lower than 8.0, the hydrogen ion concentration in the organic wastewater is high, which will inhibit the hydrolysis and reaction activity of phosphate ions, which is not conducive to the formation of magnesium ammonium phosphate precipitation, resulting in a reduction in the removal rate of ammonia nitrogen and phosphate. When the pH value is higher than 9.5, the alkalinity in the organic wastewater is too strong, which may cause magnesium ions to form magnesium hydroxide precipitation, consume magnesium ions, reduce the chance of reacting with ammonium ions and phosphate ions to form magnesium ammonium phosphate precipitation, and also affect the removal effect.

[0028] It should be explained that the pH meter has been monitoring the pH value of the organic wastewater in real time to ensure that the pH value of the reaction system is always stable within the optimal range.

[0029] Among them, in S2, the temperature of organic wastewater is adjusted to 20 ℃-30 ℃, for example, the temperature of organic wastewater can be adjusted by heat exchange device. The temperature of exemplary organic wastewater is 20 ℃, 21 ℃, 22 ℃, 23 ℃, 24 ℃, 25 ℃, 26 ℃, 27 ℃, 28 ℃, 29 ℃, 30 ℃, etc. In this temperature range, the chemical reaction rate is moderate, which is conducive to the reaction between magnesium ions, ammonium ions and phosphate ions, and the generation efficiency and quality of magnesium ammonium phosphate precipitation can be guaranteed. Among them, when the temperature is lower than 20 ℃, the chemical reaction rate slows down, the precipitation generation speed slows down, the processing efficiency decreases, and a longer reaction time may be required to achieve the desired removal effect. When the temperature is higher than 30 ℃, although the reaction rate will accelerate, the excessively high temperature may cause the solubility of magnesium ammonium phosphate precipitation to increase slightly, and also increase energy consumption and processing costs.

[0030] It should be explained that the thermometer has been monitoring the temperature of the organic wastewater in real time to ensure that the temperature of the reaction system is always stable within the optimal range of 20℃-30℃.

[0031] Wherein in this step, it is necessary to add magnesium salt to organic wastewater, and magnesium salt includes at least one of magnesium chloride, magnesium sulfate, and magnesium nitrate, and the addition of magnesium salt needs to be determined according to the concentration of ammonia nitrogen and phosphate in organic wastewater;Wherein the mol ratio of the addition of magnesium ion to ammonia nitrogen is 1.0-1.2:1;The mol ratio of the addition of magnesium ion to phosphate is 1.0-1.2:1;For example, if magnesium chloride is used as magnesium salt, it is converted according to the molar mass, and the magnesium chloride addition per liter of organic wastewater is about 0.1-0.2g (in terms of magnesium ion). In addition, if the concentration of ammonia nitrogen and phosphate in organic wastewater is too high, the amount of magnesium salt can be appropriately increased, but it should be noted to avoid excessive addition, and excessive magnesium salt will not only cause waste of reagents, increase processing costs, but also may cause the residual magnesium ions in the treated organic wastewater to exceed the standard.

[0032] After adding magnesium salt to the organic wastewater, the reaction is stirred at a speed of 20rpm-40rpm for 0.5-2h. After adding magnesium salt to the organic wastewater in the example, the stirring rate during the stirring reaction is 20rpm, 22rpm, 23rpm, 24rpm, 25rpm, 27rpm, 28rpm, 29rpm, 30rpm, 31rpm, 35rpm, 40rpm, etc., and the reaction is carried out for 1h or 2h.

[0033] When magnesium salt is added to organic wastewater, the magnesium salt is ionized in the water. Taking magnesium chloride as an example, its ionization equation is: MgCl2=Mg 2+ +2Cl - , producing magnesium ions (Mg 2+ The ammonia nitrogen in organic wastewater is mainly in the form of ammonium ions (NH4 + ) exists in the form of organic wastewater, and organic wastewater contains phosphate ions (PO4 3- ). Under certain conditions, magnesium ions (Mg 2+ ), ammonium ion (NH4 + ) and phosphate ions (PO4 3- ) to undergo a chemical reaction. The reaction formula is: Mg 2+ +NH4 + +PO4 3- +6H2O=MgNH4PO4·6H2O↓, generating magnesium ammonium phosphate (MgNH4PO4) precipitation, also known as struvite precipitation. Through this chemical reaction, ammonia nitrogen and phosphate in organic wastewater are removed from the water in the form of precipitation, achieving the effect of simultaneous nitrogen and phosphorus removal.

[0034] After the organic wastewater is treated by the method of this application, the removal rate of ammonia nitrogen can reach more than 90%, and the removal rate of phosphate can reach more than 95%. The concentration of ammonia nitrogen in the treated organic wastewater can be reduced to below 50 mg / L; the concentration of phosphate can be reduced to below 10 mg / L, which can meet the national sewage discharge standards. Therefore, through the unique chemical precipitation reaction and precise control of process parameters, the efficient and simultaneous removal of ammonia nitrogen and phosphate in organic wastewater is achieved, which brings new technological breakthroughs to the field of sewage treatment and has important economic and environmental benefits.

[0035] Example 1

[0036] Take 10L of organic wastewater discharged from a food processing plant and test its initial NH4 + The concentration is 80mg / L (about 0.04mol), PO4 3- The concentration is 400 mg / L (0.04 mol), the pH value is 7.0, and the temperature is 18°C. First, add an appropriate amount of sodium hydroxide solution to the organic wastewater to adjust the pH value to 8.0. Then, the wastewater temperature is raised to 20°C through a heat exchanger. Next, add 4 g (0.04 mol) of magnesium chloride, equivalent to 1.02 g of magnesium ions, to the organic wastewater, and stir the reaction for 60 minutes to allow the magnesium chloride to fully react with the ammonia nitrogen and phosphate in the organic wastewater.

[0037] After the reaction, the solid-liquid separation was carried out by precipitation and filtration. After testing, the ammonia nitrogen concentration in the treated organic wastewater was 15 mg / L and the phosphate concentration was 5 mg / L, achieving a good treatment effect.

[0038] Example 2

[0039] Take 10L of organic wastewater from a farm, the initial NH4 + The concentration is 75mg / L (0.04mol), PO4 3- The concentration is 420mg / L (0.04mol), the pH value of the organic wastewater is adjusted to 7.5, the temperature is 25℃, and magnesium sulfate, 5.5g (0.04mol), equivalent to 1.11g of magnesium ions, is directly added to the organic wastewater, and the reaction is stirred for 45 minutes. After the reaction is completed, precipitation and filtration operations are performed. After testing, the ammonia nitrogen concentration in the treated wastewater is 20mg / L, and the phosphate concentration is 6mg / L, and the treatment effect is satisfactory.

[0040] The above examples fully demonstrate that the method of the present application has the advantages of simple operation, good treatment effect, low cost and resource recycling, has broad application prospects, and can provide an efficient and reliable technical solution for the treatment of nitrogen and phosphorus pollution in organic wastewater.

[0041] It should be noted that, in the description of this application, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of this application, unless otherwise specified, the meaning of "plurality" is two or more.

[0042] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0043] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0044] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for simultaneous removal of nitrogen and phosphorus from organic wastewater, characterized in that: The following steps are involved: Detecting the concentration of ammonia nitrogen and phosphate in the organic wastewater, and adjusting the pH value of the organic wastewater to 8.0-9.5; The temperature of the organic wastewater is adjusted to 20°C-30°C; and magnesium salt is added thereto; The amount of magnesium ions added is similar to that of NH4 + The molar ratio is 1.0-1.2:1; the amount of magnesium ion added is related to PO4 3- The molar ratio is 1.0-1.2:

1.

2. The method according to claim 1, characterized in that The concentration of ammonia nitrogen in the organic wastewater is 100-500 mg / L, and the concentration of phosphate is 50-200 mg / L.

3. The method according to claim 1 or 2, characterized in that The magnesium salt includes at least one of magnesium chloride, magnesium sulfate and magnesium nitrate.

4. The method according to claim 3, characterized in that The method for adjusting the organic wastewater is to use hydrochloric acid or sodium hydroxide solution for adjustment.

5. The method according to claim 3, characterized in that The amount of magnesium ions added per liter of organic wastewater is 0.1-0.2g.

6. The method according to claim 3, characterized in that After adding magnesium salt into the organic wastewater, the mixture is stirred at a speed of 20 rpm to 40 rpm for reaction for 0.5 to 2 hours.

7. The method according to claim 3, characterized in that The chemical reaction formula for simultaneous nitrogen and phosphorus removal in organic wastewater is: Mg 2+ +NH4 + +PO4 3- +6H2O=MgNH4PO4·6H2O↓。 8. The method according to claim 3, characterized in that The ammonia nitrogen concentration in the treated organic wastewater does not exceed 50 mg / L; the phosphate concentration does not exceed 10 mg / L.

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