CN114835297A

CN114835297A - Automatic nitrogen and phosphorus recovery equipment and method for low-concentration aquaculture wastewater

Info

Publication number: CN114835297A
Application number: CN202210532528.8A
Authority: CN
Inventors: 万智强; 史传叶; 徐德福; 李冰
Original assignee: Nanjing Chuan Ye Environmental Protection Technology Co ltd
Current assignee: Nanjing Chuan Ye Environmental Protection Technology Co ltd
Priority date: 2022-05-17
Filing date: 2022-05-17
Publication date: 2022-08-02

Abstract

The invention discloses automatic nitrogen and phosphorus recovery equipment for low-concentration aquaculture wastewater, which relates to the technical field of sewage treatment and comprises a reactor; a water inlet device comprising a first vessel in communication with the reactor; the alkali adding device comprises a second container, and the second container is communicated with the first container; a magnesium salt addition device comprising a third vessel in communication with the reactor; an aeration device; and the struvite collecting device comprises a struvite pumping pipe, a pump body connected to the struvite pumping pipe and a fourth container used for collecting struvite. The invention not only improves the purity of the struvite and ensures the recovery of nitrogen and phosphorus in the sewage, but also realizes the automatic collection of the struvite, avoids the problem that the reactor needs to be stopped for the traditional gravity collection of the struvite, realizes the continuous operation of the reactor and improves the working efficiency.

Description

Automatic nitrogen and phosphorus recovery equipment and method for low-concentration aquaculture wastewater

Technical Field

The invention relates to the technical field of sewage treatment, in particular to automatic nitrogen and phosphorus recovery equipment and method for low-concentration aquaculture wastewater.

Background

With the rapid development of national economy, the demand for phosphorite resources is increasing. Phosphorite is a scarce resource, which is irreplaceable and non-renewable. Since 2002, the national resources department ranks phosphate rock as one of 20 important mineral resources urgently needed by national economic development. On one hand, the continuous exhaustion of phosphorus resources, and on the other hand, a large amount of phosphorus-containing wastewater is discharged into a water environment to cause environmental pollution such as water eutrophication and the like. The contradiction between the depletion of the phosphorite resource and the waste of the phosphorus resource makes the phosphorus recovery process increasingly receive attention from people. In recent decades, phosphorus recovery processes have been extensively studied and advanced to some extent, mainly including chemical precipitation, biological processes, desorption, struvite crystallization, etc.

The traditional chemical precipitation method is mainly used for recovering or removing phosphorus by adding chemical substances such as iron salt or aluminum salt into a phosphorus-rich solution and reacting with phosphate radical in the solution to form precipitate. Although this reaction can rapidly remove phosphorus from the solution, the removal effect of low-concentration wastewater is not ideal, and a large amount of sludge generated during the precipitation process increases the treatment cost. The biological phosphorus removal technology is phosphorus release of phosphorus-accumulating bacteria under anaerobic condition and excessive phosphorus absorption under aerobic condition, and the phosphorus removal method is realized by alternately operating aerobic and anaerobic conditions. The method has low cost, simple process and no secondary pollution, but the stability of the method is influenced by environmental conditions and other microorganisms in the sewage. The adsorption method is to recover phosphorus from phosphorus-rich wastewater by physical adsorption with an adsorbent. Although the method is low in cost and high in adsorption speed, the traditional adsorbents such as iron oxide and activated carbon are low in selectivity to phosphate ions, and the application of the traditional adsorbents in phosphorus recovery is limited.

Struvite crystallization is a phosphorus recovery process that has attracted attention in recent years. The method mainly comprises the steps of regulating Mg: p: n molar ratio and solution pH, a magnesium source is added to the nitrogen and phosphorus containing wastewater to precipitate struvite (MAP). The method has high phosphorus content, and the recovered MAP product can be used as a slow release fertilizer in agricultural production to realize resource utilization of phosphorus. The reactor is of great importance to the recovery of nitrogen and phosphorus by a struvite crystallization method, and a reactor with excellent design can not only improve the removal rate of nitrogen and phosphorus in wastewater, but also has remarkable help on the purity and particle size of the generated struvite. The reactors that have been developed so far are roughly classified into stirred reactors and fluidized bed reactors according to hydraulic characteristics. The stirring type crystallization reactor has simple structure and convenient operation, can improve the recovery rate of phosphorus, but has serious scaling phenomenon in the production process and has stirring speed which is difficult to match the growth and the quality of crystals. The fluidized bed has simple equipment and compact structure, but has the defect that the alkali addition and the struvite recovery cannot be automatically controlled.

Disclosure of Invention

The invention aims to solve the technical problem of overcoming the defects of the prior art and provides automatic nitrogen and phosphorus recovery equipment and method for low-concentration aquaculture wastewater.

In order to solve the technical problems, the technical scheme of the invention is as follows:

an automatic nitrogen and phosphorus recovery device for low-concentration aquaculture wastewater comprises,

a reactor;

the water inlet device comprises a first container for containing sewage, and the first container is communicated with the reactor through a sewage conveying pipe and a pump body connected to the sewage conveying pipe;

the alkali adding device comprises a second container for containing alkali liquor, and the second container is communicated with the first container through an alkali liquor conveying pipe and a pump body connected to the alkali liquor conveying pipe;

the magnesium salt adding device comprises a third container for containing a magnesium salt solution, and the third container is communicated with the reactor through a magnesium salt conveying pipe and a pump body connected to the magnesium salt conveying pipe;

an aeration device disposed within the reactor; and the number of the first and second groups,

struvite collection device takes out the pipe, connects the pump body on the struvite takes out the pipe and is used for collecting the fourth container of struvite including struvite, the one end that the guan was taken out to the struvite extends in the reactor, the other end that the guan was taken out to the struvite extends in the fourth container.

As an optimized scheme of the automatic nitrogen and phosphorus recovery equipment for the low-concentration aquaculture wastewater, the method comprises the following steps: the device comprises a reactor, a phosphate adding device and a pump body, wherein the reactor is used for storing phosphate solution, the phosphate adding device comprises a fifth container used for containing the phosphate solution, and the fifth container is communicated with the reactor through a phosphate solution conveying pipe and the pump body connected to the phosphate solution conveying pipe.

As an optimized scheme of the automatic nitrogen and phosphorus recovery equipment for the low-concentration aquaculture wastewater, the method comprises the following steps: still include the EDTA and add the device, the EDTA adds the device including the sixth container that is used for splendid attire EDTA solution, the sixth container pass through EDTA solution conveyer pipe and connect the pump body on EDTA solution conveyer pipe with the reactor intercommunication.

As an optimized scheme of the automatic nitrogen and phosphorus recovery equipment for the low-concentration aquaculture wastewater, the method comprises the following steps: still include pH controlling means, pH controlling means includes pH detection device and pH controller, pH detection device sets up in the first container, pH detection device with the pH controller electricity is connected for with the pH value signal transmission who detects extremely the pH controller, the pH controller is connected with the pump body electricity of connecting on the alkali lye conveyer pipe for the control opening and close of pump body.

As an optimized scheme of the automatic nitrogen and phosphorus recovery equipment for the low-concentration aquaculture wastewater, the method comprises the following steps: the aeration devices are arranged in at least two groups, and the at least two groups of aeration devices are sequentially distributed along the height direction of the reactor.

As an optimized scheme of the automatic nitrogen and phosphorus recovery equipment for the low-concentration aquaculture wastewater, the method comprises the following steps: the aeration device comprises a blower and a microporous diffuser connected with the blower, and the microporous diffuser is fixedly arranged in the reactor.

As an optimized scheme of the automatic nitrogen and phosphorus recovery equipment for the low-concentration aquaculture wastewater, the method comprises the following steps: the struvite collection device further comprises a filter screen, wherein the filter screen is fixedly arranged in the fourth container, the filter screen is arranged along the horizontal direction, and the inner partition of the fourth container is a struvite collection cavity above the filter screen and a sewage collection cavity below the filter screen.

As an optimized scheme of the automatic nitrogen and phosphorus recovery equipment for the low-concentration aquaculture wastewater, the method comprises the following steps: the upper end of the reactor is fixedly provided with a triangular weir plate.

The invention also discloses an automatic nitrogen and phosphorus recovery method of the low-concentration aquaculture wastewater, which comprises the following steps,

detecting the pH value of the sewage contained in the first container through a pH detection device, comparing the detected pH value with a preset pH value range, controlling a pump body connected to an alkali liquor conveying pipe to start by a pH controller if the detected pH value is not in the preset pH value range, conveying the alkali liquor contained in the second container into the first container until the detected pH value is in the preset pH value range, standing for 10-30 min, and conveying the sewage in the first container into a reactor;

adding a magnesium salt solution into the reactor through a magnesium salt adding device;

adding an EDTA solution into the reactor through an EDTA adding device;

starting an aeration device, and conveying air into the microporous diffuser through a blower to fully mix sewage, magnesium salt, EDTA solution and alkali liquor in the reactor to promote the generation of struvite;

when the struvite is accumulated to a certain amount, the struvite in the reactor is extracted through a struvite extraction pipe and conveyed to a fourth container.

As an optimal scheme of the method for automatically recovering nitrogen and phosphorus from the low-concentration aquaculture wastewater, the method comprises the following steps: after the magnesium salt solution is added into the reactor through the magnesium salt adding device, the method also comprises the following steps,

phosphate solution was added to the reactor through a phosphate addition device.

The invention has the beneficial effects that:

(1) according to the invention, the aeration device is arranged in the reactor, so that the purpose of stirring the solution in the reactor is achieved, the problem of serious scaling phenomenon in the production process of the stirring type reactor is effectively avoided, and the stirring speed can be matched with the growth and quality of crystals.

(2) According to the invention, the pH of the sewage is adjusted by the alkali adding device, so that the pH value of the sewage is in a preset pH range, and the removal rate of nitrogen and phosphorus in the sewage by the reactor can be effectively improved.

(3) According to the invention, the struvite collecting device is arranged, and the struvite pumping pipe is used for collecting struvite, so that the automatic collection of struvite is realized, the problem that the operation of the reactor needs to be stopped when the struvite is collected by gravity in the prior art is solved, the continuous operation of the reactor is realized, and the working efficiency is improved.

(4) The invention is also provided with an EDTA adding device, EDTA solution can be added into the reactor through the EDTA adding device, and Ca can be reduced through the complexation reaction of ETDA ²⁺ And the effect of heavy metals on the purity of struvite.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.

FIG. 1 is a schematic structural diagram of an automatic nitrogen and phosphorus recovery device for low-concentration aquaculture wastewater provided by the invention;

FIG. 2 is a statistical plot of phosphorus removal rate at different pH's in example 1;

FIG. 3 is a statistical chart of the removal rate of ammonia nitrogen at different pH values in example 1;

FIG. 4 is an XRD pattern of the product recovered in example 1;

FIG. 5 is a statistical chart of the removal rate of ammonia nitrogen with the addition of magnesium salts and phosphates in example 2;

FIG. 6 is a statistical plot of the phosphorus removal rate with the addition of magnesium salts and phosphates in example 2;

FIG. 7 is the XRD pattern of the product recovered in example 2;

wherein: 1. a reactor; 2. a first container; 3. a pump body; 4. a second container; 5. a third container; 6. a fourth container; 7. a struvite extraction pipe; 8. a fifth container; 9. a sixth container; 10. a pH controller; 11. a pH detection device; 12. a blower; 13. a microporous diffuser; 14. filtering with a screen; 15. a triangular weir plate; 16. a water outlet; 17. and an evacuation valve.

Detailed Description

In order that the present invention may be more readily and clearly understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings.

FIG. 1 is a schematic structural diagram of an automatic nitrogen and phosphorus recovery device for low-concentration aquaculture wastewater provided by an embodiment of the application. The device comprises a reactor 1, a water inlet device, an alkali adding device, a magnesium salt adding device, a phosphate adding device, an EDTA adding device, an aerating device and a struvite collecting device.

In particular, the reactor 1 as a whole is a fluidized bed made of plexiglass. The upper part of the reactor 1 is provided with a water outlet 16, and the bottom of the reactor 1 is provided with an emptying valve 17. Preferably, a triangular weir plate 15 is fixedly installed at the upper end of the reactor 1, and the function of the triangular weir plate is to uniformly discharge water and prevent the generated struvite from being flushed out by the water flow.

The water inlet device comprises a first container 2 for containing contaminated water. The first container 2 is in communication with the reactor 1 through a sewage conduit. The sewage conveying pipe is also provided with a pump body 3, and the pump body 3 can convey the sewage in the first container 2 to the interior of the reactor 1 through the sewage conveying pipe when in work.

The alkali adding device comprises a second container 4 for containing alkali liquor. The second container 4 is communicated with the first container 2 through an alkali liquor conveying pipe. The alkali liquor conveying pipe is also provided with a pump body 3, and the pump body 3 can convey the alkali liquor in the second container 4 to the first container 2 through the alkali liquor conveying pipe when in work. In this example, NaOH solution was used as the alkali solution.

Preferably, a pH detection device 11 for detecting the pH value of the sewage in the first container 2 is further fixedly installed inside the first container 2. The pH detecting device 11 is electrically connected to the pH controller 10, and is configured to transmit a detected pH signal to the pH controller 10. The pH controller 10 is also electrically connected with the pump body 3 connected with the alkali liquor conveying pipe and used for controlling the opening and closing of the pump body 3.

The magnesium salt adding device comprises a third container 5 for containing a magnesium salt solution. The third vessel 5 is in communication with the reactor 1 via a magnesium salt transfer line. A pump body 3 is also mounted on the magnesium salt delivery pipe, and the pump body 3 can deliver the magnesium salt solution in the third container 5 to the interior of the reactor 1 when in operation.

The device also comprises a phosphate adding device, which comprises a fifth container 8 for containing phosphate solution, wherein the fifth container 8 is communicated with the reactor 1 through a phosphate solution conveying pipe and a pump body 3 connected to the phosphate solution conveying pipe

The EDTA adding means includes a sixth container 9 for holding an EDTA solution. The fourth container 6 is in communication with the reactor 1 through an EDTA solution delivery pipe. A pump body 3 is also arranged on the EDTA solution delivery pipe, and the pump body 3 can deliver the EDTA solution in the fourth container 6 to the inside of the reactor 1 when in work.

The aeration device is fixedly arranged in the reactor 1. In this embodiment, the aeration devices are provided in two sets, two sets being provided at different heights inside the reactor 1. Each set of aeration devices comprises a blower 12 and a microporous diffuser 13 connected to the blower 12. Wherein, micropore diffuser 13 fixed mounting is inside reactor 1, and air-blower 12 sets up outside reactor 1, through gas-supply pipe and micropore diffuser 13 intercommunication. The blower 12 is operated to deliver air to the microporous diffuser 13 and then to discharge the air from the microporous diffuser 13 into the reactor 1, thereby stirring the solution in the reactor 1.

The struvite collecting device comprises a struvite pumping pipe 7, a pump body 3 and a fourth container 6. The fourth vessel 6 is located outside the reactor 1. One end of the struvite pumping pipe 7 extends to the bottom in the reactor 1, and the other end extends to the open end of the fourth container 6. The pump body 3 is arranged on a struvite pumping pipe 7. The pump body 3 during operation accessible guanite pump tube 7 takes out the guanite that reactor 1 internal generation was taken out to carry to in the fifth container 8, realize the automatic collection of guanite.

Preferably, a filter screen 14 is fixedly installed inside the fourth container 6, and the filter screen 14 is horizontally arranged in the middle of the fourth container 6 to divide the inside of the fourth container 6 into an upper struvite collecting cavity and a lower sewage collecting cavity. One end of the struvite suction pipe 7 extends to the upper part of the filter screen 14. After the struvite and the sewage collected by the struvite suction pipe 7 are delivered to the filter screen 14, the struvite is accumulated above the filter screen 14, and the sewage discharged is accumulated in the sewage collection chamber at the lower part of the fourth container 6 through the filter screen 14.

The embodiment also provides an automatic nitrogen and phosphorus recovery method for the low-concentration aquaculture wastewater, which comprises the following steps of S101-S105:

step S101: the pH value of the sewage contained in the first container 2 is detected through the pH detection device 11, the detected pH value is compared with a preset pH value range, if the detected pH value is not in the preset pH value range, the pH controller 10 controls the pump body 3 connected to the alkali liquor conveying pipe to be started, the alkali liquor contained in the second container 4 is conveyed into the first container 2 until the detected pH value is in the preset pH value range, then the first container 2 is kept still for 10-30 min to precipitate in the first container 2, and then the sewage in the first container 2 is conveyed into the reactor 1.

The phosphate radical and calcium ions form hydroxyapatite precipitate when the pH value is 9.0-10.5, and the magnesium phosphate precipitate is easily generated when the pH value is higher than 10. In addition, Cu-OH and Cu-PO are easily generated under alkaline conditions ₄ 、Cu-NH ₃ 、 Zn-PO ₄ And Zn-OH, etc. Thus, the addition of lye in the first vessel 2, rather than directly into the reactor 1, allows these precipitates to be precipitated in the pretreatment tank, preventing the precipitates from being precipitated in the reactor 1, thereby increasing the purity of struvite.

Step S102: magnesium salt is added into the reactor through a magnesium salt adding device.

Step S103: an EDTA solution was added to the reactor by an EDTA adding device. Reduction of Ca by complex reaction of ETDA ²⁺ And the effect of heavy metals on the purity of struvite.

Step S104: and starting the aeration device, and conveying air into the microporous diffuser through the air blower to fully mix the sewage, the magnesium salt, the EDTA solution and the alkali liquor in the reactor to promote the generation of struvite.

Step S105: when the struvite is accumulated to a certain amount, the struvite in the reactor is extracted through a struvite extraction pipe and conveyed to a fourth container.

It should be noted that when only magnesium salt is added into the reactor, the removal rate of phosphorus in the wastewater is high, but the removal rate of ammonia nitrogen in the wastewater is low. When it is necessary to increase the removal rate of ammonia nitrogen in the sewage, a phosphate solution may be added to the reactor through a phosphate adding device in step S102.

The following is illustrated by two specific examples:

example 1:

when the ammonia nitrogen of the aquaculture wastewater entering the reactor is 185 Mg/g, and the phosphate is 20-50 Mg/g, adding magnesium salt, and adjusting the ratio of Mg: p = 1.3: 1, adjusting the pH value of the reactor to 8.5, 9, 9.5 and 10 by an alkali adding device, and then starting an aeration system for a retention time of 90 min. The reactor has a phosphorus removal rate of between 50% and 80%, see fig. 2. The removal rate of the reactor to ammonia nitrogen is between 15% and 30%, see figure 3. The crystal form of the precipitate was the same as struvite at pH 8.5, 9, 9.5 and 10, respectively, see fig. 4, indicating that the recovered product was struvite.

The struvite purity at different pH is shown in table 1, from which it can be seen that the struvite purity can reach up to 86.7%.

pH	8.5	9	9.5	10
					Purity of	83.7	84.5	86.9	76.5

TABLE 1 struvite purity

Example 2

When the ammonia nitrogen of the aquaculture wastewater entering the reactor is 185 mg/g, and the phosphate is 20-50 mg/g, adding magnesium salt and phosphate, and adjusting the ratio of N: mg =1:0.8:0.8, the pH of the reactor was adjusted to 9.5, then the aeration system was turned on for a residence time of 90 min. The phosphorus removal rate of the reactor on the aquaculture wastewater reaches 50 percent, see figure 5, and the ammonia nitrogen removal rate reaches 52 percent, see figure 6. In the different N: mg the crystal form of the precipitate is the same as struvite, see FIG. 7, indicating that the product recovered is struvite.

Different N: under the condition of P: Mg, the purity of the struvite is shown in Table 2, and the purity of the struvite can reach 88.5 percent at most.

N：P：Mg	1	1:0.9:0.9	1:0.8:0.8	1:0.7:0.7
					Purity of	88.5	87.5	88.5	86.5

TABLE 2 struvite purity

From this, the technical scheme of this application has not only improved the purity of struvite, has guaranteed the recovery to nitrogen phosphorus in the sewage, has realized the automatic collection of struvite moreover, has avoided the tradition to collect the problem that the struvite need stop the reactor operation through gravity, has realized the continuous operation of reactor, has improved work efficiency.

In addition to the above embodiments, the present invention may have other embodiments; all technical solutions formed by adopting equivalent substitutions or equivalent transformations fall within the protection scope of the claims of the present invention.

Claims

1. The utility model provides an automatic recovery plant of nitrogen phosphorus of waste water is bred to low concentration which characterized in that: comprises the steps of (a) preparing a mixture of a plurality of raw materials,

a reactor (1);

the water inlet device comprises a first container (2) for containing sewage, and the first container (2) is communicated with the reactor (1) through a sewage conveying pipe and a pump body (3) connected to the sewage conveying pipe;

the alkali adding device comprises a second container (4) for containing alkali liquor, and the second container (4) is communicated with the first container (2) through an alkali liquor conveying pipe and a pump body (3) connected to the alkali liquor conveying pipe;

the magnesium salt adding device comprises a third container (5) for containing a magnesium salt solution, wherein the third container (5) is communicated with the reactor (1) through a magnesium salt conveying pipe and a pump body (3) connected to the magnesium salt conveying pipe;

an aeration device arranged in the reactor (1); and the number of the first and second groups,

struvite collection device takes out pipe (7), connects pump body (3) on struvite takes out pipe (7) and fourth container (6) that are used for collecting the struvite including the struvite, the one end of struvite taking out pipe (7) extends in reactor (1), the other end of struvite taking out pipe (7) extends in fourth container (6).

2. The automatic nitrogen and phosphorus recovery equipment for low-concentration aquaculture wastewater according to claim 1, characterized in that: still include phosphate and add the device, including the fifth container (8) that is used for splendid attire phosphate solution, fifth container (8) through phosphate solution conveyer pipe and connect pump body (3) on the phosphate solution conveyer pipe with reactor (1) intercommunication.

3. The automatic nitrogen and phosphorus recovery equipment for low-concentration aquaculture wastewater according to claim 1, characterized in that: still include the EDTA and add the device, the EDTA adds the device and includes sixth container (9) that are used for splendid attire EDTA solution, sixth container (9) pass through EDTA solution conveyer pipe and connect pump body (3) on EDTA solution conveyer pipe with reactor (1) intercommunication.

4. The automatic nitrogen and phosphorus recovery equipment for low-concentration aquaculture wastewater according to claim 1, characterized in that: still include pH controlling means, pH controlling means includes pH detection device (11) and pH controller (10), pH detection device (11) set up in first container (2), pH detection device (11) with pH controller (10) electricity is connected for with the pH value signal transmission who detects extremely pH controller (10), pH controller (10) are connected with pump body (3) electricity of connecting on the alkali liquor conveyer pipe for the opening and close of control pump body (3).

5. The automatic nitrogen and phosphorus recovery equipment for low-concentration aquaculture wastewater according to claim 1, characterized in that: the aeration devices are arranged in at least two groups, and the at least two groups of aeration devices are sequentially distributed along the height direction of the reactor (1).

6. The automatic nitrogen and phosphorus recovery equipment for low-concentration aquaculture wastewater according to claim 1 or 5, characterized in that: the aeration device comprises a blower (12) and a microporous diffuser (13) connected with the blower (12), wherein the microporous diffuser (13) is fixedly arranged in the reactor (1).

7. The automatic nitrogen and phosphorus recovery equipment for low-concentration aquaculture wastewater according to claim 1, characterized in that: struvite collection device still includes filter screen (14), filter screen (14) are fixed to be set up in fourth container (6), filter screen (14) set up along the horizontal direction, and will the sewage collection chamber of chamber and lower part is collected to the internal partitioning of fourth container (6) for the struvite of top.

8. The automatic nitrogen and phosphorus recovery equipment for low-concentration aquaculture wastewater according to claim 1, characterized in that: the upper end of the reactor (1) is fixedly provided with a triangular weir plate (15).

9. The automatic nitrogen and phosphorus recovery method for the low-concentration aquaculture wastewater is characterized by comprising the following steps of: comprises the steps of (a) preparing a mixture of a plurality of raw materials,

adding an EDTA solution into the reactor through an EDTA adding device;

10. The automatic nitrogen and phosphorus recovery method for low-concentration aquaculture wastewater according to claim 9, characterized by comprising the following steps: after the magnesium salt solution is added into the reactor through the magnesium salt adding device, the method also comprises the following steps,