Method for accelerating removal of COD (Chemical Oxygen Demand) in wastewater and improving nitrogen utilization rate

Abstract

The invention provides a method for accelerating removal of COD in wastewater and increasing the nitrogen utilization rate, and belongs to the technical field of sewage treatment. The hematite, the biochar and the nitrification inhibitor dicyandiamide are sequentially added into the livestock and poultry wastewater, the activity of organic pollutant degrading microorganisms and the activity of inhibiting nitrification microorganisms are enhanced by regulating and controlling the adding proportion, removal of COD in the livestock and poultry wastewater is accelerated, and meanwhile most ammonia nitrogen in the livestock and poultry wastewater is reserved; and then myriophyllum elatinoides with high tolerance to ammonium is utilized, so that most of the retained nitrogen can be recycled, the utilization efficiency of the nitrogen in the livestock and poultry wastewater is greatly improved, and the method has good practicability.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and particularly relates to a method for accelerating the removal of COD in wastewater and improving the utilization rate of nitrogen. Background Art

[0002] In recent years, people's requirements for the quality of life have been increasing day by day, and their demand for livestock and poultry products has also been increasing day by day. Therefore, the livestock and poultry breeding industry has developed rapidly. At present, the livestock and poultry breeding industry has become a pillar industry for the economic development of rural areas. The livestock and poultry wastewater generated by the livestock and poultry breeding industry is an organic wastewater with complex components, high ammonia nitrogen and high organic matter, and its treatment is extremely difficult. If the livestock and poultry wastewater is directly discharged without treatment, it will cause serious pollution to the water source in rural areas and the surrounding environment. Therefore, how to properly treat these livestock and poultry wastewaters has become an urgent problem to be solved.

[0003] The livestock and poultry wastewater contains utilizable nitrogen resources. Recycling it can not only provide data reference for preventing and controlling the pollution of livestock and poultry breeding wastewater, but also provide a theoretical basis for further resource utilization of livestock and poultry breeding wastewater. At present, the methods for recovering and treating nitrogen and phosphorus in livestock and poultry wastewater are mainly divided into physical, chemical and biological methods. Among them, physical and chemical methods are restricted by certain conditions in practical applications due to defects such as high cost and large energy consumption; the biological method uses aquatic plants for nutrient recovery. However, at present, most of the nitrogen in the wastewater is mainly degraded through the nitrification and denitrification of microorganisms, and less is absorbed and utilized by plants, resulting in a great waste of nitrogen resources. Therefore, retaining the nitrogen in the livestock and poultry wastewater for plant absorption and utilization is the key to solving the problem.

[0004] In recent years, researchers have begun to use nitrification inhibitors to retain nitrogen for plants or crops to absorb and utilize, so as to achieve the recycling of nitrogen. However, there are deficiencies such as long treatment time and low efficiency when plants and microorganisms treat COD in livestock and poultry wastewater. Therefore, researchers use chemical methods and microbial degradation methods to treat COD. However, although this method can effectively treat the organic matter in livestock and poultry wastewater, the nitrogen in the wastewater will also be removed accordingly, and the recycling of nitrogen cannot be achieved. Therefore, it is necessary to develop a method that can accelerate the removal of COD in livestock and poultry wastewater while retaining most of the nitrogen resources for plant absorption and utilization and improving the nitrogen utilization rate. Summary of the Invention

[0005] In view of some deficiencies in the prior art, the present invention provides a method for accelerating the removal of COD in wastewater and improving the nitrogen utilization rate. The present invention sequentially adds hematite, biochar, and nitrification inhibitor dicyandiamide to livestock and poultry wastewater, and enhances the activity of organic pollutant-degrading microorganisms and inhibits the activity of nitrifying microorganisms by regulating the dosing ratio. While accelerating the removal of COD in livestock and poultry wastewater, most of the ammonia nitrogen in the livestock and poultry wastewater is retained, and then water sprite with high ammonium tolerance characteristics is used, which helps to recycle most of the retained nitrogen, greatly improving the nitrogen utilization efficiency in livestock and poultry wastewater and having good practicability.

[0006] To achieve the above technical objectives, the present invention adopts the following technical means:

[0007] The present invention provides a method for accelerating the removal of COD in wastewater and improving the nitrogen utilization rate, and the method includes:

[0008] (1) Mix the wastewater stock solution and clean water to obtain diluted wastewater, and then add iron oxide minerals, biochar, and nitrification inhibitor to the diluted wastewater to obtain pretreated wastewater;

[0009] (2) Plant aquatic plants in the treated wastewater, and harvest the aquatic plants after culturing for a period of time.

[0010] Preferably, in step (1), the wastewater stock solution includes but is not limited to livestock and poultry wastewater, domestic sewage, food processing wastewater, etc.; preferably livestock and poultry wastewater.

[0011] Preferably, in step (1), the COD concentration in the diluted wastewater is less than 5000 mg / L, the total nitrogen concentration is less than 500 mg / L, and the ammonia nitrogen concentration is less than 400 mg / L.

[0012] Preferably, in step (1), the iron oxide minerals include one or more of hematite, goethite, magnetite, ferrihydrite, and chamosite; preferably hematite.

[0013] Preferably, in step (1), the raw materials of the biochar include wheat straw, rice straw, corn straw, and sawdust.

[0014] Preferably, in step (1), the nitrification inhibitor includes one or more of dicyandiamide, 3,4-dimethylpyrazole phosphate, 2-chloro-6-trichloromethylpyridine, or acetylene, and preferably dicyandiamide.

[0015] Preferably, in step (1), the mass ratio of the iron oxide minerals to the biochar is 4:1; the dosage ratio of the mixture of the iron oxide minerals and the biochar to the diluted wastewater is 0 - 250 g and not 0 g:3 L; preferably 200 g:3 L;

[0016] The addition amount of the nitrification inhibitor is less than 10 wt% of the total nitrogen content in the diluted wastewater.

[0017] Preferably, in step (2), the aquatic plants are aquatic plants with high tolerance to ammonium; preferably Myriophyllum verticillatum.

[0018] Preferably, in step (2), the planting density of the aquatic plants is less than 2 kg / m 2 ; and the cultivation time is less than 30 days.

[0019] Preferably, in step (2), the harvested aquatic plants are used to prepare silage.

[0020] The present invention also provides the application of the aquatic plants obtained by the above method for accelerating the removal of COD in wastewater and improving the nitrogen utilization rate in the preparation of silage. Preferably, the aquatic plants include Myriophyllum verticillatum.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] The present invention designs a method for synchronously strengthening the removal of COD and nitrogen utilization in livestock and poultry wastewater by Myriophyllum verticillatum. By regulating the dosing ratios of biochar, hematite, and nitrification inhibitor in the wastewater, the activity of organic pollutant-degrading microorganisms is enhanced and the activity of nitrifying microorganisms is inhibited. While accelerating the removal of COD in livestock and poultry wastewater, most of the ammonia nitrogen in the livestock and poultry wastewater is retained. Then, Myriophyllum verticillatum with high tolerance to ammonium is used, which helps to recycle most of the retained nitrogen, and greatly improves the nitrogen utilization efficiency in livestock and poultry wastewater.

[0023] The method of the present invention effectively overcomes the problem that when treating livestock and poultry wastewater in the prior art, while accelerating COD, it also accelerates the removal of nitrogen by microorganisms, resulting in the inability to retain nitrogen for plant absorption and utilization, reducing the nitrogen utilization rate and causing waste of nitrogen resources. The core principle of the method of the present invention is to add an electron shuttle medium in addition to providing an additional electron acceptor, so that the reducing bacteria that cannot directly contact with the iron oxide mineral use the electron shuttle as a medium for electron transfer, thereby achieving the acceleration of COD removal and the COD removal rate in livestock and poultry wastewater reaching 96%.

[0024] In the method of the present invention, the nitrification of nitrifying bacteria is inhibited after the addition of nitrification inhibitors, so that the nitrogen in the wastewater exists in the form of ammonia nitrogen for Myriophyllum verticillatum to utilize, without affecting the microorganisms that degrade organic pollutants. Therefore, in livestock and poultry wastewater, while COD is efficiently treated by microorganisms with enhanced electron transfer, the nitrifying bacteria with inhibited activity lose their nitrification function, so that most of the nitrogen is retained and thus absorbed and utilized by Myriophyllum verticillatum. The utilization rate of nitrogen in livestock and poultry wastewater by Myriophyllum verticillatum reaches 72%, greatly improving the nitrogen utilization efficiency in livestock and poultry wastewater.

[0025] The present invention mixes iron-oxidizing mineral hematite and biochar in a certain proportion to obtain a hematite-biochar mixture for accelerating the removal of COD in livestock and poultry wastewater; mixes the original livestock and poultry wastewater and clear water in a certain proportion, and then adds the nitrification inhibitor dicyandiamide in a certain proportion according to the total nitrogen concentration in the mixed livestock and poultry wastewater to ensure that while effectively retaining the nitrogen in the livestock and poultry wastewater, no phytotoxicity is produced; adds the hematite and biochar in a certain addition amount and the prepared dicyandiamide to the mixed livestock and poultry wastewater according to the addition method. Under the condition of adding more than 0 g of hematite and biochar, the COD removal rate in livestock and poultry wastewater increases. Under the condition of adding more than 150 g of the hematite-biochar mixture, the COD removal rate is the highest. Under the condition of adding less than 10% of the total nitrogen content in the wastewater of dicyandiamide, most of the nitrogen in the wastewater can be effectively retained and no toxicity to plants is produced. Through condition control, the COD in livestock and poultry wastewater can be efficiently removed by microorganisms that degrade organic pollutants, most of the nitrogen is retained, and through the utilization of Myriophyllum verticillatum, the COD in livestock and poultry wastewater can be acceleratedly removed while the nitrogen utilization rate is improved.

[0026] The Myriophyllum verticillatum obtained by harvesting according to the method of the present invention has high nutritional value, contains a large amount of protein, and has good application in the preparation of silage feed. Description of the Drawings

[0027] Figure 1 Shows the influence of adding different proportions of hematite-biochar mixture on the removal rate of organic matter in livestock and poultry wastewater.

[0028] Figure 2 Shows the influence of adding different proportions of hematite-biochar mixture on the total nitrogen removal rate in livestock and poultry wastewater.

[0029] Figure 3 Shows the influence of adding different proportions of hematite-biochar mixture on the ammonia nitrogen removal rate in livestock and poultry wastewater.

[0030] Figure 4 Shows the influence of adding hematite-biochar mixture and dicyandiamide on the removal rate of organic matter in livestock and poultry wastewater.

[0031] Figure 5To study the effects of adding hematite-biochar mixture and dicyandiamide on nitrogen utilization in livestock and poultry wastewater. Detailed implementation mode

[0032] The present invention is specifically described below through examples, aiming to better understand the technical connotation of the present invention. However, the protection scope of the present invention is not limited to the following implementation scope.

[0033] The steps of the method for synchronously enhancing the removal of COD and nitrogen utilization in livestock and poultry wastewater by Myriophyllum verticillatum described in the present invention are as follows:

[0034] (1) Mix the wastewater stock solution and clean water to obtain diluted wastewater, and then add iron oxide minerals, biochar, and nitrification inhibitors to the diluted wastewater to obtain pretreated wastewater.

[0035] (2) Plant aquatic plants in the treated wastewater, and harvest the aquatic plants after culturing for a period of time.

[0036] Among them, the iron oxide minerals include one or more of hematite, goethite, magnetite, ferrihydrite, and chamosite; preferably hematite; the raw materials of biochar include wheat straw, rice straw, corn straw, and sawdust; the nitrification inhibitors include one or more of dicyandiamide, 3,4-dimethylpyrazole phosphate, 2-chloro-6-trichloromethylpyridine, or acetylene, preferably dicyandiamide. The wastewater stock solution includes but is not limited to livestock and poultry wastewater, domestic sewage, food processing wastewater, etc.; preferably livestock and poultry wastewater.

[0037] The aquatic plants are aquatic plants with high ammonium tolerance characteristics, preferably Myriophyllum verticillatum; the planting density of the aquatic plants is less than 2 kg / m 2 ; The cultivation time is less than 30 days

[0038] In the following examples, the combination of hematite, biochar, and dicyandiamide is used to elaborate on the method described in the present invention in detail, but the protection scope of the present invention is not limited thereto.

[0039] Example 1: Effects of different dosages of hematite-biochar mixture on the degradation effect of pollutants in wastewater

[0040] In this example, a mixture without adding hematite and biochar is used as the control group to investigate the degradation effect of different dosages of hematite and biochar on pollutants in wastewater. The wastewater is livestock and poultry wastewater with a COD concentration of 900-1000 mg / L, a total nitrogen concentration of 300-400 mg / L, and an ammonia nitrogen concentration of 200-300 mg / L. The specific steps are as follows:

[0041] Mix hematite and biochar with a mass ratio of 4:1 to obtain a hematite-biochar mixture, and then add the hematite-biochar mixture to livestock and poultry wastewater. Among them, the total addition amounts of the hematite-biochar mixture are 150 g, 200 g, and 250 g respectively, and then transfer it to a round plastic bucket (height: 190 mm, inner diameter of the bucket mouth: 252 mm). The treatment period is 30 days, and the COD removal rate, total nitrogen removal rate, and ammonia nitrogen removal rate of the wastewater are investigated. The investigation results are as Figures 1 to 3 shown in Table 1.

[0042] Table 2. Analysis table of the removal rate of pollutants in livestock and poultry wastewater with different addition amounts of hematite-biochar mixture

[0043]

[0044] Combined with Table 1 and Figures 1 to 3 it can be seen that the removal efficiency of pollutants in livestock and poultry wastewater is higher than that of the control group without addition. With the increase of the addition amount of the hematite-biochar mixture, the removal rate of pollutants in livestock and poultry wastewater also increases, and when adding 200 g and 250 g, the removal rate of pollutants in livestock and poultry wastewater is higher than that when adding 150 g of the hematite-biochar mixture, indicating that the hematite-biochar mixture has the best sewage treatment effect when the addition amount is 200 g and 250 g. However, when adding 200 g and 250 g of the hematite-biochar mixture, the removal rate of pollutants tends to be the same, indicating that when the hematite-biochar mixture is added to a certain amount, the removal of pollutants in livestock and poultry wastewater reaches saturation.

[0045] Example 2: Effect of different addition amounts of nitrification inhibitor dicyandiamide on nitrogen retention in wastewater

[0046] In this example, without adding nitrification inhibitor dicyandiamide as the control group, the effect of different addition amounts of nitrification inhibitor dicyandiamide on nitrogen retention in wastewater is investigated. The wastewater is livestock and poultry wastewater with a COD concentration of 900 - 1000 mg / L, a total nitrogen concentration of 300 - 400 mg / L, and an ammonia nitrogen concentration of 200 - 300 mg / L. The specific steps are as follows:

[0047] Add the purchased nitrification inhibitor dicyandiamide to livestock and poultry wastewater. Among them, the addition amounts of nitrification inhibitor dicyandiamide are 1%, 5%, and 10% of the total nitrogen content in the wastewater respectively, and then transfer it to a round plastic bucket (height: 190 mm, inner diameter of the bucket mouth: 252 mm). Cultivate Myriophyllum aquaticum in the round plastic bucket, and plant 20 Myriophyllum aquaticum plants in each bucket. The treatment period is 30 days, and the total nitrogen removal rate and ammonia nitrogen removal rate of the wastewater are investigated. The investigation results are shown in Table 2.

[0048] Table 2. Analysis table of the nitrogen removal rate of livestock and poultry wastewater with different addition amounts of nitrification inhibitor dicyandiamide

[0049]

[0050] As can be seen from Table 2, with the increase in the dosage of the nitrification inhibitor dicyandiamide, the nitrogen removal rate in livestock and poultry wastewater decreases, indicating that the nitrification inhibitor dicyandiamide can effectively promote the retention of nitrogen in livestock and poultry wastewater, and the more the dosage of the nitrification inhibitor dicyandiamide, the better the nitrogen retention effect.

[0051] Example 3: Effect of adding hematite-biochar mixture and dicyandiamide on the degradation of pollutants in wastewater

[0052] In this example, without adding the hematite-biochar mixture and dicyandiamide as the control group (Treatment 1), the effect of adding the hematite-biochar mixture and dicyandiamide (Treatment 2) on the degradation of pollutants in wastewater was investigated. The wastewater was livestock and poultry wastewater with a COD concentration of 900 - 1000 mg / L, a total nitrogen concentration of 300 - 400 mg / L, and an ammonia nitrogen concentration of 200 - 300 mg / L. The investigation steps were basically the same as those in Example 1. Myriophyllum aquaticum was cultivated in a round plastic bucket, with 20 plants of Myriophyllum aquaticum planted in each bucket. After a treatment period of 30 days, the COD removal rate, total nitrogen removal rate, and ammonia nitrogen removal rate of the wastewater were investigated. The investigation results are as Figures 4 to 5 and Table 3 show.

[0053] Table 3. Analysis table of the removal rate of pollutants in livestock and poultry wastewater by adding hematite-biochar mixture and dicyandiamide

[0054]

[0055]

[0056] Combined with Figures 4 to 5 and Table 3, it can be seen that within the concentration range of the organic matter concentration of 900 - 1000 mg / L, the total nitrogen concentration of 300 - 400 mg / L, and the ammonia nitrogen concentration of 200 - 300 mg / L in livestock and poultry wastewater, the present invention can well degrade the organic matter concentration in livestock and poultry wastewater, and can effectively retain nitrogen and recycle it using Myriophyllum aquaticum. The removal rate of COD reaches more than 96%, and the nitrogen utilization rate is significantly improved.

[0057] In summary, the present invention successively adds hematite, biochar, and the nitrification inhibitor dicyandiamide to livestock and poultry wastewater, enhances the activity of organic pollutant-degrading microorganisms and inhibits the activity of nitrifying microorganisms by regulating the dosing ratio, retains most of the ammonia nitrogen in livestock and poultry wastewater while accelerating the removal of COD in livestock and poultry wastewater, and then uses Myriophyllum aquaticum with high ammonium tolerance characteristics, which helps to recycle most of the retained nitrogen, greatly improving the nitrogen utilization efficiency in livestock and poultry wastewater and having good practicability.

[0058] The described embodiments are the preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Without departing from the substantial content of the present invention, any obvious improvements, substitutions or modifications that can be made by those skilled in the art all fall within the protection scope of the present invention.

Claims

1. A method for accelerating the removal of COD in wastewater and improving the utilization rate of nitrogen, characterized in that, The method includes: (1) Mix the original wastewater and clean water to obtain diluted wastewater, and then add iron oxide minerals, biochar, and nitrification inhibitors to the diluted wastewater to obtain pretreated wastewater; (2) Plant aquatic plants in the treated wastewater, and harvest the aquatic plants after culturing for a period of time.

2. The method for accelerating the removal of COD in wastewater and improving the nitrogen utilization rate according to claim 1, characterized in that, In step (1), the original wastewater includes livestock and poultry wastewater, domestic sewage, and food processing wastewater.

3. The method for accelerating the removal of COD in wastewater and improving the nitrogen utilization rate according to claim 2, characterized in that, The original wastewater is livestock and poultry wastewater.

4. The method for accelerating the removal of COD in wastewater and improving the nitrogen utilization rate according to claim 1, wherein In step (1), the COD concentration in the diluted wastewater is less than 5000 mg / L, the total nitrogen concentration is less than 500 mg / L, and the ammonia nitrogen concentration is less than 400 mg / L.

5. The method for accelerating the removal of COD in wastewater and improving the nitrogen utilization rate according to claim 1, wherein In step (1), the iron oxide minerals include one or more of hematite, goethite, magnetite, ferrihydrite, and chamosite; The raw materials of the biochar include wheat straw, rice straw, corn straw, and sawdust; The nitrification inhibitors include one or more of dicyandiamide, 3,4-dimethylpyrazole phosphate, 2-chloro-6-trichloromethylpyridine, or acetylene.

6. The method for accelerating the removal of COD in wastewater and improving the utilization rate of nitrogen according to claim 5, characterized in that, The iron oxide mineral is hematite; The nitrification inhibitor is dicyandiamide.

7. The method for accelerating the removal of COD in wastewater and improving the nitrogen utilization rate according to claim 1, characterized in that, In step (1), the mass ratio of the iron oxide minerals to the biochar is 4:1; the dosage ratio of the mixture of the iron oxide minerals and the biochar to the diluted wastewater is 0 - 250 g (not 0 g): 3 L; The addition amount of the nitrification inhibitor is less than 10 wt% of the total nitrogen content in the diluted wastewater.

8. The method for accelerating the removal of COD from wastewater and improving the nitrogen utilization rate according to claim 1, characterized in that In step (2), the aquatic plant is an aquatic plant with high ammonium tolerance characteristics; the planting density of the aquatic plant is less than 2 kg / m 2 ; and the cultivation time is less than 30 days.

9. The method for accelerating the removal of COD in wastewater and improving the nitrogen utilization rate according to claim 1, wherein In step (2), the harvested aquatic plants are used to prepare silage feed.

10. Use of the aquatic plants obtained by the method for accelerating the removal of COD in wastewater and improving the nitrogen utilization rate according to any one of claims 1 - 9 in the preparation of silage feed.

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