Phosphorus-containing wastewater treatment device as well as treatment method and application thereof

Abstract

The invention discloses a phosphorus-containing wastewater treatment device and a treatment method and application thereof. The phosphorus-containing wastewater treatment device comprises a first reaction unit, comprising a first reaction cavity, a water inlet pipe for injecting phosphorus-containing wastewater into the first reaction cavity, a first chemical feeder for adding acid or alkali into the first reaction cavity, a first stirrer positioned in the first reaction cavity, and a first pH meter for detecting the pH value in the first reaction cavity; the second reaction unit comprises a second reaction cavity positioned at the downstream of the first reaction cavity, a second doser for adding polymeric ferric sulfate into the second reaction cavity, a second stirrer positioned in the second reaction cavity, and a second pH meter for detecting the pH value in the second reaction cavity; the third reaction unit comprises a third reaction cavity positioned at the downstream of the second reaction cavity, a third doser for adding a polyacrylamide solution into the third reaction cavity, and a third stirrer positioned in the third reaction cavity. By judging the pH value of the solution and controlling the adding amount of the polymeric ferric sulfate, the problem that the adding amount of ferric salt is too large or too low is solved.

Description

Technical Field

[0001] The present invention relates to the field of wastewater treatment, and in particular to a phosphorus-containing wastewater treatment device and a treatment method and application thereof. Background Art

[0002] With the continuous development of the economy and society, more and more phosphorus elements have entered wastewater and natural water bodies through various channels. After high-phosphorus substances enter the water body, they increase the nutrients in the water body, causing eutrophication of the water body, thereby causing a large number of algae and plankton to reproduce, causing a large number of aquatic plants and animals to die due to lack of oxygen, seriously affecting the ecological balance of rivers and lakes. Therefore, dephosphorization of wastewater as an important measure to prevent and control eutrophication of water bodies has also received more and more attention.

[0003] At present, the commonly used phosphorus removal methods at home and abroad include biological methods and chemical precipitation methods. Although biological phosphorus removal has the advantages of low cost and low sludge production in wastewater treatment, it also has disadvantages such as unstable treatment effect, low treatment efficiency when the phosphorus content of wastewater is high, and even the need for secondary phosphorus treatment. As a practical, efficient, economical and convenient phosphorus removal method, chemical precipitation has a high treatment efficiency for high-phosphorus wastewater and is generally welcomed by wastewater treatment plants at home and abroad. Chemical phosphorus removal agents are generally aluminum salts, iron salts, and calcium salts. Regardless of the phosphorus removal agent, its dosing endpoint is difficult to control. Adding too much will cause waste. In addition, the amount of sludge is large, and the phosphorus removal effect is not thorough if the dosage is small, resulting in excessive total phosphorus. Therefore, how to control its dosing endpoint is imminent.

[0004] In view of this, it is necessary to provide an improved phosphorus-containing wastewater treatment device and its treatment method and application to solve the above-mentioned technical problems. Summary of the invention

[0005] The invention provides a phosphorus-containing wastewater treatment device and a treatment method and application thereof, aiming to overcome the problem in the prior art that the amount of iron salt added is not accurately controlled, resulting in excessive or insufficient addition.

[0006] In order to achieve one of the above-mentioned invention objects, the present invention adopts the following technical solution:

[0007] A phosphorus-containing wastewater treatment device comprises: a first reaction unit, comprising a first reaction chamber, a water inlet pipe for injecting phosphorus-containing wastewater into the first reaction chamber, a first doser for adding acid or alkali into the first reaction chamber, a first agitator located in the first reaction chamber, and a first pH meter for detecting the pH value in the first reaction chamber; a second reaction unit, comprising a second reaction chamber located downstream of the first reaction chamber, a second doser for adding polyferric sulfate into the second reaction chamber, a second agitator located in the second reaction chamber, and a second pH meter for detecting the pH value in the second reaction chamber; and a third reaction unit, comprising a third reaction chamber located downstream of the second reaction chamber, a third doser for adding polyacrylamide solution into the third reaction chamber, and a third agitator located in the third reaction chamber.

[0008] In one embodiment, the first pH meter is communicatively connected to the first doser so that when the pH in the first reaction chamber reaches a first pH value, the first doser is closed to stop adding acid or alkali; the second pH meter is communicatively connected to the second doser so that when the pH in the second reaction chamber reaches a second pH value, the second doser is closed to stop adding polyferric sulfate.

[0009] In one embodiment, the first pH value is greater than the second pH value; or the first pH value is 7.5 to 8.0; and the second pH value is 6.5 to 7.0.

[0010] In one embodiment, the speed of the first stirrer is greater than the stirring speeds of the second stirrer and the third stirrer; and / or the stirring time of the third stirrer and the second stirrer is greater than the stirring time of the first stirrer.

[0011] A method for treating phosphorus-containing wastewater based on the phosphorus-containing wastewater treatment device comprises the following steps: injecting phosphorus-containing wastewater into a first reaction chamber through a water inlet pipe, starting a first agitator, and starting a first doser to add acid or alkali into the first reaction chamber until the pH in the first reaction chamber is adjusted to a first pH value; starting a second agitator, and starting a second doser to inject polyferric sulfate into a second reaction chamber until the pH in the second reaction chamber reaches a second pH value; starting a third agitator, and starting a third doser to inject a polyacrylamide solution into the third reaction chamber.

[0012] In one embodiment, the first pH value is greater than the second pH value; or the first pH value is 7.5 to 8.0; and the second pH value is 6.5 to 7.0.

[0013] In one embodiment, after the pH in the second reaction chamber reaches the second pH value, stirring is continued for a preset time.

[0014] In one embodiment, the stirring speed of the first stirrer is greater than the stirring speeds of the second stirrer and the third stirrer; and / or the stirring time of the second stirrer and the third stirrer is greater than the stirring time of the second stirrer.

[0015] In one embodiment, the amount of polyacrylamide solution added is 1.5-2 mg / L.

[0016] Application of the above-mentioned phosphorus-containing wastewater treatment device or phosphorus-containing wastewater treatment method in phosphorus-containing wastewater treatment.

[0017] The beneficial effects of the present invention are as follows: the phosphorus-containing wastewater treatment device and treatment method of the present invention first adjust the pH of the phosphorus-containing wastewater to a first pH value in a first reaction unit as a benchmark; then add polyferric sulfate under stirring, and judge and control the amount of polyferric sulfate added by the pH of the solution, thereby overcoming the problem of inaccurate control of the amount of iron salt added in the prior art, resulting in excessive or too low an amount of addition. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the phosphorus-containing wastewater treatment device of the present invention.

[0019] 100-phosphorus-containing wastewater treatment device, 1-first reaction unit, 11-first reaction chamber, 12-water inlet pipe, 13-first doser, 14-first agitator, 15-first pH meter; 2-second reaction unit, 21-second reaction chamber, 22-second doser, 23-second agitator, 24-second pH meter; 3-third reaction unit, 31-third reaction chamber, 32-third doser, 33-third agitator. DETAILED DESCRIPTION

[0020] The present invention will be described in detail below in conjunction with the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present invention, and any structural, methodological, or functional changes made by a person skilled in the art based on these embodiments are all within the scope of protection of the present invention.

[0021] In the various drawings of the present invention, for the convenience of illustration, some sizes of structures or parts are exaggerated relative to other structures or parts, and thus, they are only used to illustrate the basic structure of the subject matter of the present invention.

[0022] like Figure 1 As shown, the present invention provides a phosphorus-containing wastewater treatment device 100, comprising a first reaction unit 1, a second reaction unit 2 and a third reaction unit 3 which are arranged in sequence, and are respectively used to adjust the pH of the phosphorus-containing wastewater, add polyferric sulfate to the wastewater, and add polyacrylamide (PAM) to the wastewater, so as to effectively treat the phosphorus-containing wastewater.

[0023] The first reaction unit 1 includes a first reaction chamber 11, a water inlet pipe 12 for injecting phosphorus-containing wastewater into the first reaction chamber 11, a first doser 13 for adding acid or alkali into the first reaction chamber 11, a first agitator 14 located in the first reaction chamber 11, and a first pH meter 15 for detecting the pH value in the first reaction chamber 11.

[0024] Acid or alkali is added into the first reaction chamber 11 through the first dosing device 13 to adjust the pH of the phosphorus-containing wastewater to a first pH value, thereby achieving the conditions for the reaction of polyferric sulfate with the phosphorus-containing wastewater and facilitating accurate control of the amount of polyferric sulfate added.

[0025] The first pH meter 15 is in communication connection with the first doser 13 , so that when the pH in the first reaction chamber 11 reaches a first pH value, the first doser 13 is closed to stop adding acid or alkali.

[0026] In one embodiment, the first pH value is 7.5 to 8.0, which provides a good basis for phosphorus removal and adjusts the pH of the solution to a reference value to prevent the pH of the wastewater from affecting the precise control of the amount of polyferric sulfate added.

[0027] When the first pH value is low, the total phosphorus removal rate in the wastewater is low. This is because when the first pH value is low, the wastewater is highly acidic. At this time, the phosphorus in the wastewater is mainly in the form of H 3 PO 4 They are difficult to react with coagulants. At the same time, polyferric sulfate is mainly Fe after hydrolysis under acidic conditions. 3+ It exists in the form of and cannot play an adsorption and bridging role during the coagulation process, resulting in a low total phosphorus removal rate in the wastewater.

[0028] As the first pH value increases, the total phosphorus removal rate increases rapidly. When the first pH value is 7.5-8, the total phosphorus removal rate reaches the maximum value. Under this pH condition, the wastewater is neutral or weakly alkaline, and the phosphorus in the wastewater begins to be H 2 PO 4 - and HPO 4 2- It exists in the form of polyferric sulfate, and the hydrolysis products of polyferric sulfate are mainly highly charged high-polymer complexes. At this time, the phosphorus in the wastewater can react with the coagulant to form insoluble metal phosphate complexes. The phosphorus in the wastewater can be removed under the action of net capture, sweeping and adsorption bridging, thereby improving the total phosphorus removal rate.

[0029] The first pH value continues to increase, and the total phosphorus removal rate begins to decrease. Specifically, the wastewater is highly alkaline, causing a large amount of OH in the wastewater to - Preferentially react with Fe in coagulant 3+The reaction generates insoluble iron hydroxide precipitate, which reduces the adsorption and capture effect of the coagulant and leads to a decrease in the total phosphorus removal efficiency.

[0030] The second reaction unit 2 includes a second reaction chamber 21 located downstream of the first reaction chamber 11 , a second doser 22 for adding polyferric sulfate into the second reaction chamber 21 , a second agitator 23 located in the second reaction chamber 21 , and a second pH meter 24 for detecting the pH value in the second reaction chamber 21 .

[0031] The wastewater after pH adjustment in the first reaction chamber 11 flows into the second reaction chamber 21 , polyferric sulfate is added to the wastewater, and the pH value of the wastewater is detected by the second pH meter 24 .

[0032] The second pH meter 24 is connected to the second doser 22 for communication, so that when the pH in the second reaction chamber 21 reaches the second pH value, the second doser 22 is closed to stop adding polyferric sulfate. The present invention can accurately control the amount of polyferric sulfate added by detecting the pH value in the second reaction chamber 21 and controlling the amount of polyferric sulfate added thereby to avoid overdosage or underdosage.

[0033] In one embodiment, the second pH value is less than the first pH value to ensure that a sufficient amount of polyferric sulfate is added to ensure the phosphorus removal effect.

[0034] The second pH value is 6.5-7.0. If the second pH value is too high, phosphorus removal will be incomplete, and if the second pH value is too low, excessive amount of polyferric sulfate will be added. In a preferred embodiment, the second pH value is 6.8.

[0035] The third reaction unit 3 includes a third reaction chamber 31 located downstream of the second reaction chamber 21 , a third doser 32 for adding polyacrylamide solution into the third reaction chamber 31 , and a third agitator 33 located in the third reaction chamber 31 .

[0036] The water from the second reaction chamber 21 enters the third reaction chamber 31 and is added with polyacrylamide solution for flocculation.

[0037] Among them, the stirring speed of the first agitator 14 is greater than the stirring speed of the second agitator 23 and the stirring speed of the third agitator 33, that is, the first reaction unit 1 is a rapid mixing and stirring, and the second reaction unit 2 and the third reaction unit 3 are slow reaction stirring. Rapid stirring allows the wastewater in the first reaction chamber 11 to be quickly stirred and evenly, improves the treatment efficiency, and provides a basis for subsequent accurate measurement of pH and accurate control of the amount of polyferric sulfate added. The second reaction chamber 21 and the third reaction chamber 31 are locally slowly stirred, which is conducive to the full reaction and flocculation of chemicals and improves the phosphorus removal effect.

[0038] In one embodiment, the stirring time of the second agitator 23 and the third agitator 33 is greater than the stirring time of the second agitator 23, so that the phosphorus in the wastewater is fully precipitated and separated.

[0039] Based on the phosphorus-containing wastewater treatment device 100, the present invention also provides a phosphorus-containing wastewater treatment method, comprising the following steps:

[0040] Inject phosphorus-containing wastewater into the first reaction chamber 11 through the water inlet pipe 12, start the first agitator 14, and start the first dosing device 13 to add acid or alkali into the first reaction chamber 11 until the pH in the first reaction chamber 11 is adjusted to a first pH value;

[0041] Start the second agitator 23, and start the second dosing device 22 to inject polyferric sulfate into the second reaction chamber 21 until the pH in the second reaction chamber 21 reaches a second pH value;

[0042] The third agitator 33 is started, and the third dosing device 32 is started to inject the polyacrylamide solution into the third reaction chamber 31 .

[0043] The stirring speed of the first stirrer 14 is 120 r / min to 200 r / min. If the stirring speed is too fast, the energy consumption is too large and it is unsafe; if the stirring speed is too slow, it is impossible to mix quickly.

[0044] In the first reaction unit 1, the first pH value is 7.5-8.0, which provides a good basis for phosphorus removal and adjusts the pH of the solution to a benchmark to avoid the pH of the wastewater affecting the precise control of the amount of polyferric sulfate added.

[0045] Polyferric sulfate is added into the second reaction chamber 21 under stirring, and the amount of polyferric sulfate added is timely determined and controlled by detecting the pH of the solution.

[0046] Polyferric sulfate is a positively charged polymer coagulant. It neutralizes negatively charged ions in phosphorus-containing wastewater, causing the colloid in the wastewater to destabilize and form a large number of flocs. As these flocs grow, the adsorption, bridging and precipitation netting effects of the coagulant are enhanced, thereby removing the total phosphorus in the wastewater and generating precipitates. These precipitates are insoluble metal phosphate complexes and will hydrolyze to generate H + ions, affecting the pH value of the water body. At the same time, the excess polyferric sulfate itself will undergo hydrolysis reaction to generate H + Ions affect the pH value of water, so we can determine whether the polyferric sulfate is excessively added by monitoring the pH value of the water after the reaction. The second pH value is less than the first pH value in step S1, in order to ensure the phosphorus removal effect.

[0047] In the present invention, the second pH value is 6.5 to 7.0. At this time, the polyferric sulfate and the phosphorus in the water body generate a sparingly soluble metal phosphate complex, and the polyferric sulfate is not excessive.

[0048] In the third reaction unit 3, the amount of polyacrylamide solution added is calculated based on the amount of polyferric sulfate added. The amount of polyacrylamide solution added is 1.5-2 mg / L.

[0049] The phosphorus-containing wastewater treatment device 100 and the treatment method of the present invention will be described in detail below with reference to specific embodiments.

[0050] Embodiment 1:

[0051] In this embodiment, phosphorus-containing wastewater from Maoming is treated, and polyferric sulfate and polyacrylamide solution are on-site preparation reagents. When the total phosphorus in the influent is 3.2 mg and the dosage of polyferric sulfate is 50 mg / L, the relationship between the effluent pH of the second reaction chamber 21, the phosphorus removal rate and the pH in the first reaction chamber 11 are tested, and the test results are shown in Table 1.

[0052] Specifically, after adding polyferric sulfate, stirring and reacting for 60 seconds, then adding 0.1% PAM and continuing stirring and reacting for 300 seconds, after the reaction is completed, settling for 1 hour, taking the supernatant, and detecting the total phosphorus content in the water.

[0053] Table 1

[0054]

[0055] When the dosage of polyferric sulfate is 50 mg / L, by controlling the pH in the first reaction chamber 11 to 8, the minimum total phosphorus content in the effluent is 0.15 mg / L, the total phosphorus removal rate reaches 95.31%, and the corresponding pH of the effluent from the second reaction chamber 21 is 6.8.

[0056] It can be seen from Example 1 that the pH of the first reaction chamber 11 will affect the pH of the effluent from the second reaction chamber 21, and when the first pH value is 7.5-8.0, it can provide a good basis for phosphorus removal and adjust the pH of the solution to a benchmark to avoid the pH of the wastewater affecting the precise control of the amount of polyferric sulfate added.

[0057] Embodiment 2:

[0058] In this embodiment, phosphorus-containing wastewater from Maoming is treated, and polyferric sulfate and polyacrylamide solution are on-site prepared reagents. When the total phosphorus in the influent is 3.2 mg, the relationship between the pH of the effluent from the second reaction chamber 21 and a series of polyferric sulfate dosages and phosphorus removal rates is tested, and the test results are shown in Table 1.

[0059] Specifically, after adding polyferric sulfate with contents of 30 mg / L, 42 mg / L, 50 mg / L, 58 mg / L, 66 mg / L, 74 mg / L, 83 mg / L and 90 mg / L respectively, the reaction was stirred for 60 seconds, and then 0.1% PAM was added and the reaction was continued with stirring for 300 seconds. After the reaction was completed, the mixture was precipitated for 1 hour, and the supernatant was taken to detect the total phosphorus content in the water.

[0060] After the above process, the indicators are shown in Table 2.

[0061] Table 2

[0062]

[0063] When the total phosphorus in the inlet water is 3.2 mg and the pH of the effluent from the second reaction chamber 21 is 6.5-6.8, the dosage of polyferric sulfate is 50 mg / L-66 mg / L, and the dosage of PAM is 1.5 mg / L-2 mg / L, the total phosphorus in the biochemical effluent is reduced to 0.18 mg / L or less, and the total phosphorus removal rate can reach more than 94%.

[0064] Embodiment 3:

[0065] The difference from Example 2 is that the total phosphorus in the inlet water is 15.36 mg, and the relationship between the pH of the outlet water from the second reaction chamber 21 and a series of polyferric sulfate dosages and phosphorus removal rates is tested. The test results are shown in Table 3.

[0066] Table 3

[0067]

[0068] When the total phosphorus in the inlet water is 15.36 mg and the pH is 6.5-7.0, the dosage of polyferric sulfate is 240 mg / L~317 mg / L, and the dosage of PAM is 1.5 mg / L~2 mg / L, the total phosphorus in the biochemical effluent is reduced to 0.50 mg / L~0.53 mg / L, and the total phosphorus removal rate can reach more than 96%.

[0069] It can be seen from Examples 2 and 3 that when the pH in the first reaction chamber 11 is constant, the pH of the water outlet from the second reaction chamber 21 has a high correspondence with the amount of polyferric sulfate added and the phosphorus removal treatment, and the amount of polyferric sulfate added can be controlled by the pH of the water outlet from the second reaction chamber 21 to prevent it from being excessive or insufficient.

[0070] The phosphorus-containing wastewater treatment device 100 and the phosphorus-containing wastewater treatment method of the present invention can accurately control the amount of polyferric sulfate used, and can control the total phosphorus of the effluent to below 0.5 mg / L, the total phosphorus removal rate reaches more than 94%, the total phosphorus of the effluent is far below the emission limit, and the entire device is simple to operate and low in cost. The phosphorus-containing wastewater treatment device 100 and the phosphorus-containing wastewater treatment method of the present invention can be used to treat phosphorus-containing wastewater, especially dye wastewater, pesticide wastewater, printing and dyeing wastewater, petroleum zeolite and the like.

[0071] In summary, the phosphorus-containing wastewater treatment device 100 and treatment method of the present invention first adjust the pH of the phosphorus-containing wastewater to a first pH value in the first reaction unit 1 as a benchmark; then add polyferric sulfate under stirring, and timely detect, judge and control the amount of polyferric sulfate added by the pH of the solution, thereby overcoming the problem of inaccurate control of the amount of iron salt added in the prior art, resulting in excessive or too low an amount of addition.

[0072] It should be understood that although this specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation mode may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

[0073] The series of detailed descriptions listed above are only specific descriptions of feasible implementation methods of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A phosphorus-containing wastewater treatment device, characterized in that: include: The first reaction unit comprises a first reaction chamber, a water inlet pipe for injecting phosphorus-containing wastewater into the first reaction chamber, a first doser for adding acid or alkali into the first reaction chamber, a first stirrer located in the first reaction chamber, and a first pH meter for detecting the pH value in the first reaction chamber; The second reaction unit includes a second reaction chamber located downstream of the first reaction chamber, a second doser for adding polyferric sulfate into the second reaction chamber, a second agitator located in the second reaction chamber, and a second pH meter for detecting the pH value in the second reaction chamber; The third reaction unit comprises a third reaction chamber located downstream of the second reaction chamber, a third doser for adding polyacrylamide solution into the third reaction chamber, and a third stirrer located in the third reaction chamber.

2. The phosphorus-containing wastewater treatment device according to claim 1, characterized in that: The first pH meter is communicatively connected to the first doser, so that when the pH in the first reaction chamber reaches a first pH value, the first doser is closed to stop adding acid or alkali; The second pH meter is communicatively connected with the second doser, so that when the pH in the second reaction chamber reaches a second pH value, the second doser is closed and the addition of polyferric sulfate is stopped.

3. The phosphorus-containing wastewater treatment device according to claim 2, characterized in that: The first pH value is greater than the second pH value; or The first pH value is 7.5-8.0; the second pH value is 6.5-7.

0.

4. The phosphorus-containing wastewater treatment device according to claim 1, characterized in that: The first agitator speed is greater than the agitation speeds of the second agitator and the third agitator; and / or The stirring time of the third stirrer and the second stirrer is greater than the stirring time of the first stirrer.

5. A method for treating phosphorus-containing wastewater based on the phosphorus-containing wastewater treatment device according to any one of claims 1 to 4, characterized in that: The steps include: Injecting phosphorus-containing wastewater into the first reaction chamber through the water inlet pipe, starting the first agitator, and starting the first dosing device to add acid or alkali into the first reaction chamber until the pH in the first reaction chamber is adjusted to a first pH value; Starting the second agitator, and starting the second dosing device to inject polyferric sulfate into the second reaction chamber until the pH in the second reaction chamber reaches a second pH value; The third agitator is started, and the third doser is started to inject the polyacrylamide solution into the third reaction chamber.

6. The method for treating phosphorus-containing wastewater according to claim 5, characterized in that: The first pH value is greater than the second pH value; or The first pH value is 7.5-8.0; the second pH value is 6.5-7.

0.

7. The method for treating phosphorus-containing wastewater according to claim 5, characterized in that: After the pH in the second reaction chamber reaches the second pH value, stirring is continued for a preset time.

8. The method for treating phosphorus-containing wastewater according to claim 5, characterized in that: The stirring speed of the first stirrer is greater than the stirring speeds of the second stirrer and the third stirrer; and / or the stirring time of the second stirrer and the third stirrer is greater than the stirring time of the second stirrer.

9. The method for treating phosphorus-containing wastewater according to claim 5, characterized in that: The amount of polyacrylamide solution added is 1.5-2 mg / L.

10. Use of the phosphorus-containing wastewater treatment device according to any one of claims 1 to 4 or the phosphorus-containing wastewater treatment method according to any one of claims 5 to 9 in the treatment of phosphorus-containing wastewater.

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