Treatment system and method for municipal sewage

Abstract

The treatment system comprises a crystallization and granulation fluidized bed, a particle collection device and a solid-liquid separation fluidized bed, the upper portion of the crystallization and granulation fluidized bed is provided with a feeding port and a circulating water outlet, and the lower portion of the crystallization and granulation fluidized bed is provided with a sewage inlet. The particle collecting device is connected with the crystallization and granulation fluidized bed, the lower part of the solid-liquid separation fluidized bed is provided with a circulating water inlet and a sludge discharge port, and the upper part of the solid-liquid separation fluidized bed is provided with a flocculant feeding port and a circulating water discharge port. According to the method, the seed crystal and the medicament are added into the municipal sewage, so that calcium ions in water are subjected to chemical reaction to generate calcium carbonate crystals and are recycled, the waste of resources is reduced, the output of sludge is reduced after the calcium carbonate is recycled, and the treatment cost of the sludge is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of municipal sewage treatment, and in particular to a system and method for treating municipal sewage. Background Art

[0002] At present, the hardness of municipal sewage in some cities in China has reached 800 mg / L. According to the national standard "Integrated Discharge Standard for Urban Sewage" (GB 18918-2002), the hardness of municipal sewage must be controlled below 500 mg / L. At present, lime softening and filtration process is often used in municipal sewage treatment. By adding lime milk, coagulant and coagulant aid in the mechanical accelerated clarification tank, lime slurry is used to react chemically with carbonate in water to convert soluble carbonate in water into precipitable calcium carbonate, which will eventually form chemical sludge with high water content, difficult to handle, and cannot be recycled. The lime treatment system in lime softening filtration occupies a large area, and the generated calcium carbonate is discharged in the form of sludge, causing waste of resources. In addition, the lime dosing system is prone to leakage and pipeline blockage during operation. In addition, the amount of sludge generated by the system due to the addition of lime is large, which increases the cost of sludge disposal. Summary of the invention

[0003] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0004] To this end, an embodiment of the present invention provides a system and method for treating municipal sewage.

[0005] In a first aspect, the present invention provides a system for treating municipal sewage, comprising:

[0006] A crystallization granulation fluidized bed, wherein a feed port and a circulating water outlet are arranged at the upper portion of the crystallization granulation fluidized bed, and a sewage inlet is arranged at the lower portion of the crystallization granulation fluidized bed;

[0007] A particle collecting device, the particle collecting device is connected to the crystallization granulation fluidized bed;

[0008] A solid-liquid separation fluidized bed is arranged downstream of the crystallization granulation fluidized bed, a circulating water inlet and a mud discharge port are arranged at the lower part of the solid-liquid separation fluidized bed, and a flocculant addition port and a circulating water discharge port are arranged at the upper part of the solid-liquid separation fluidized bed.

[0009] Furthermore, the sewage inlet is connected to a sewage source, and a delivery pump is arranged on the pipeline between the sewage source and the sewage inlet.

[0010] Furthermore, the seed crystals and the reagents enter the crystallization and granulation fluidized bed through the feed port.

[0011] Furthermore, the seed crystals include one or more of calcium sulfate whiskers, garnet crystal particles, and quartz sand crystal particles.

[0012] Furthermore, the reagent includes sodium hydroxide and / or sodium carbonate, and the added amount of the reagent is 0 to 20 g / L.

[0013] Furthermore, the particle collecting device is used to collect calcium carbonate produced by granulation and softening.

[0014] Furthermore, the flocculant enters the solid-liquid separation fluidized bed through the flocculant addition port.

[0015] Furthermore, the flocculant includes polyaluminium chloride.

[0016] Furthermore, the added amount of the flocculant is 0 to 500 mg / L.

[0017] In a second aspect, the present invention proposes a method for treating municipal sewage using the system proposed in the first aspect, comprising the following steps:

[0018] In the crystallization granulation fluidized bed, the crystal seeds and the reagents are added to the sewage, stirred and purified, and the obtained calcium carbonate crystals enter the particle collection device, and the produced magnesium hydroxide and the unprecipitated part of the calcium carbonate enter the solid-liquid separation fluidized bed from the circulating water outlet along with the circulating water;

[0019] In the solid-liquid separation fluidized bed, flocculants are added to the circulating water, sludge particles are formed through circulating flocculation and discharged from the sludge outlet, and the treated water is discharged through the circulating water outlet.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] The present invention adds crystal seeds and reagents to municipal sewage, so that calcium ions in the water undergo a chemical reaction to generate calcium carbonate crystals for recycling, thereby reducing waste of resources. After calcium carbonate is recycled, the amount of sludge generated is reduced, thereby reducing the cost of sludge treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0023] Figure 1 It is a schematic diagram of a treatment system for municipal sewage according to the present invention;

[0024] Figure 2 The present invention is a flow chart of the method for treating municipal sewage.

[0025] Description of reference numerals:

[0026] 1. Fluidized bed for crystallization and granulation; 2. Fluidized bed for solid-liquid separation; 3. Particle collection device. DETAILED DESCRIPTION

[0027] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0028] The following describes the system and method for treating municipal sewage proposed by the present invention in conjunction with the accompanying drawings.

[0029] like Figure 1 As shown, the municipal sewage treatment system of the present invention comprises a crystallization granulation fluidized bed 1 , a particle collecting device 3 and a solid-liquid separation fluidized bed 2 .

[0030] In some embodiments, a sewage inlet is provided at the lower part of the crystallization granulation fluidized bed 1, the sewage inlet is connected to a sewage source, a delivery pump is provided on the pipeline between the sewage source and the sewage inlet, and the sewage enters the crystallization granulation fluidized bed 1 under the action of the delivery pump.

[0031] In some embodiments, a feeding port is provided at the top of the crystallization granulation fluidized bed 1, and the seed crystals and the reagent enter the crystallization granulation fluidized bed 1 through the feeding port, the seed crystals include one or more of calcium sulfate whiskers, garnet crystal particles, and quartz sand crystal particles, the reagent includes sodium hydroxide and / or sodium carbonate, and the added amount of the reagent is 0 to 20 g / L. It is understandable that the added amount of the reagent is determined according to the hardness of the sewage.

[0032] In the crystallization granulation fluidized bed 1, by adding crystal seeds and reagents, calcium carbonate is circulated, crystallized and discharged. In this stage, most of the calcium ions are removed (about 80% removal efficiency). At the same time, in this stage, hydroxide reacts with magnesium ions to form magnesium hydroxide precipitates, which enter the solid-liquid separation fluidized bed 2 from the circulating water outlet arranged at the upper part of the crystallization granulation fluidized bed 1 along with the circulating water.

[0033] The particle collecting device 3 is connected to the crystallization granulation fluidized bed 1, and is used to collect the calcium carbonate produced by granulation and softening. The calcium carbonate collected here can be recycled.

[0034] In some embodiments, the recovered calcium carbonate is used as a desulfurization agent in a power plant.

[0035] In some embodiments, the solid-liquid separation fluidized bed 2 is arranged downstream of the crystallization granulation fluidized bed 1, and a circulating water inlet is arranged at the lower part of the solid-liquid separation fluidized bed 2. The circulating water after crystallization granulation enters the solid-liquid separation fluidized bed 2 through the circulating water inlet. In addition, the magnesium hydroxide generated in the crystallization granulation fluidized bed 1 stage and a part of the fine calcium carbonate that cannot be effectively precipitated enter the solid-liquid separation fluidized bed 2 together with the circulating water.

[0036] In some embodiments, a flocculant addition port is provided at the upper portion of the solid-liquid separation fluidized bed 2, and the flocculant enters the solid-liquid separation fluidized bed 2 through the flocculant addition port. Under the action of the flocculant, magnesium hydroxide and calcium carbonate are precipitated to form high-density sludge particles through circulating flocculation, and finally are discharged from the sludge discharge port provided at the lower portion of the solid-liquid separation fluidized bed 2 together with fine calcium carbonate particles.

[0037] In some embodiments, the flocculant is polyaluminum chloride.

[0038] In some embodiments, the amount of flocculant added is 0-500 mg / L. It is understood that the amount of flocculant added is determined according to the turbidity of the sewage.

[0039] In some embodiments, a circulating water outlet is provided on the upper part of the solid-liquid separation fluidized bed 2, and the treated sewage is discharged from the circulating water outlet. The turbidity of the treated sewage outlet can reach below 5NTU, which meets the discharge standard.

[0040] Treatment methods for municipal wastewater, such as Figure 2 As shown, the system utilizing the present invention comprises the following steps:

[0041] (a) adding crystal seeds and reagents to sewage in a crystallization and granulation fluidized bed 1, stirring and purifying the sewage, and the obtained calcium carbonate crystals enter a particle collecting device 3, and the produced magnesium hydroxide and unprecipitated calcium carbonate enter a solid-liquid separation fluidized bed 2 from a circulating water outlet along with the circulating water;

[0042] (b) A flocculant is added to the circulating water in the solid-liquid separation fluidized bed 2, and sludge particles are formed through circulating flocculation and discharged from the sludge discharge port. The treated water is discharged through the circulating water discharge port.

[0043] In step (a), by adding crystal seeds and reagents in the crystallization granulation fluidized bed 1, calcium ions in the sewage react chemically with the reagents to generate calcium carbonate crystals, which are discharged and collected by the particle collection device 3. At this stage, most of the calcium ions are removed. At the same time, at this stage, hydroxide reacts with magnesium ions to generate magnesium hydroxide precipitates, which enter the solid-liquid separation fluidized bed 2 along with the circulating water. On the other hand, a part of the fine calcium carbonate particles cannot be effectively precipitated and will flow from the crystallization granulation fluidized bed 1 into the solid-liquid separation fluidized bed 2 along with the sewage.

[0044] In step (b), a flocculant is added to the solid-liquid separation fluidized bed 2, and through the circulation flocculation, the precipitate forms high-density sludge particles, and finally the sludge is discharged from the sludge outlet of the solid-liquid separation fluidized bed 2 together with fine calcium carbonate particles. The turbidity of the effluent can reach below 5NTU, meeting the discharge standard. The sludge generated in the solid-liquid separation fluidized bed 2 is discharged from the sludge outlet, and the effluent is discharged from the circulating water outlet.

[0045] The present invention adds crystal seeds and reagents to municipal sewage, so that calcium ions in the water undergo a chemical reaction to generate calcium carbonate crystals for recycling, thereby reducing waste of resources. After calcium carbonate is recycled, the amount of sludge generated is reduced, thereby reducing the cost of sludge treatment.

[0046] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. 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 invention. In this specification, the schematic representations of the above terms may be for different embodiments or examples. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0047] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0048] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A system for treating municipal sewage, characterized in that: include: A crystallization granulation fluidized bed, wherein a feed port and a circulating water outlet are arranged at the upper portion of the crystallization granulation fluidized bed, and a sewage inlet is arranged at the lower portion of the crystallization granulation fluidized bed; A particle collecting device, the particle collecting device is connected to the crystallization granulation fluidized bed; A solid-liquid separation fluidized bed is arranged downstream of the crystallization granulation fluidized bed, a circulating water inlet and a mud discharge port are arranged at the lower part of the solid-liquid separation fluidized bed, and a flocculant addition port and a circulating water discharge port are arranged at the upper part of the solid-liquid separation fluidized bed.

2. The system according to claim 1, characterized in that The sewage inlet is connected to a sewage source, and a delivery pump is arranged on a pipeline between the sewage source and the sewage inlet.

3. The system according to claim 1, characterized in that The seed crystals and the reagents enter the crystallization and granulation fluidized bed through the feed port.

4. The system according to claim 3, characterized in that The seed crystals include one or more of calcium sulfate whiskers, garnet crystal particles, and quartz sand crystal particles.

5. The system according to claim 3, characterized in that The reagent includes sodium hydroxide and / or sodium carbonate, and the added amount of the reagent is 0-20 g / L.

6. The system according to claim 1, characterized in that The particle collecting device is used to collect the calcium carbonate produced by granulation and softening.

7. The system according to claim 1, characterized in that The flocculant enters the solid-liquid separation fluidized bed through the flocculant addition port.

8. The system according to claim 7, characterized in that The flocculant includes polyaluminium chloride.

9. The system according to claim 7, characterized in that The added amount of the flocculant is 0 to 500 mg / L.

10. A method for treating municipal sewage, characterized in that: Using the system according to any one of claims 1 to 9, comprising the following steps: In the crystallization granulation fluidized bed, the crystal seeds and the reagents are added to the sewage, stirred and purified, and the obtained calcium carbonate crystals enter the particle collection device, and the produced magnesium hydroxide and the unprecipitated part of the calcium carbonate enter the solid-liquid separation fluidized bed from the circulating water outlet along with the circulating water; In the solid-liquid separation fluidized bed, flocculants are added to the circulating water, and sludge particles are formed through circulating flocculation and discharged from the sludge discharge port. The treated water is discharged through the circulating water discharge port.

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