CN101792228B - Double-layer artificial wetland system for strengthening sewage denitrification and dephosphorization and operation method thereof - Google Patents

Abstract

The invention discloses a double-layer artificial wetland system for strengthening denitrification and dephosphorization of sewage and an operation method thereof. The system includes an upper wetland, a lower wetland, an inlet water distribution system, and an outlet water collection system. The upper wetland is filled with mineral fillers, and the lower wetland is filled with biological fillers that facilitate the growth of microorganisms. The inlet water distribution system is divided into two branches, one of which is Arranged above the upper wetland, the other branch is arranged at the interface between the upper wetland and the lower wetland, and the effluent collection system is arranged at the bottom of the lower wetland. The method described is that the sewage falls into the upper wetland through one branch of the water distribution system for oxygenation, falls into the upper wetland, and then vertically infiltrates into the lower wetland after removing organic matter, ammonia nitrogen and phosphorus; A small stream of sewage is introduced into the lower wetland and mixed with the sewage infiltrated from the upper wetland for denitrification and denitrification; the treated water is discharged from the effluent collection device. The invention occupies less area, is not easy to be blocked, has good nitrogen and phosphorus removal effects, and has low investment and operation costs.

Description

A double-layer constructed wetland system for strengthening nitrogen and phosphorus removal from sewage and its operation method

technical field

The invention relates to the technical field of sewage treatment, in particular to a double-layer constructed wetland system for strengthening nitrogen and phosphorus removal from sewage and an operation method thereof.

Background technique

Sewage Land Treatment Constructed Wetlands (CWs) has become a water pollution control technology that has attracted worldwide attention. Constructed wetlands were first publicly reported in 1904, but officially as a sewage treatment technology, they emerged in the United States, Australia, the Netherlands, Denmark, the United Kingdom and other countries in the 1970s, and their rapid development took place in the past two decades. In recent years, studies on the application of constructed wetlands to treat domestic sewage in villages and towns, control agricultural non-point source pollution, and eutrophication of rivers and lakes have been frequently reported.

However, the disadvantages of traditional constructed wetlands, such as low pollutant load, large floor area, easy clogging, insufficient oxygen supply, and unsatisfactory nitrogen and phosphorus removal effects, restrict the development speed and application scale of constructed wetlands.

In view of the insufficient oxygen supply of the constructed wetland sewage treatment system, the current research mainly focuses on the following aspects: (1) Screening plants with strong reoxygenation ability, but the treatment effect on sewage with high concentration and heavy load is not obvious, and cannot solve the problem. Seasonal differences in plant reoxygenation; (2) Increase the flow of constructed wetland treatment units or reduce the load; (3) Increase pre-treatment, such as increasing the nitrification section before land treatment or pre-aerating sewage to increase the dissolved oxygen in the influent, etc. (4) Combined with artificial aeration technology in the constructed wetland sewage treatment system, supplementing the dissolved oxygen inside the wetland, this method can improve the treatment effect of the land system before the plants grow and when the plant effect is weakened in winter, but it increases the energy consumption and operation (5) The water pump is lifted or the drop water is oxygenated by using the terrain drop.

In view of the poor denitrification effect of the constructed wetland sewage treatment system, the current research mainly focuses on the following aspects: (1) Segmented water intake, using raw water as a carbon source; (2) Adding a backflow system to return part of the effluent; (3) ) to control the conditions to form an aerobic zone and anoxic zone inside the medium.

In view of the poor phosphorus removal effect of constructed wetlands, the current research mainly focuses on the following aspects: (1) pretreatment of sewage by chemical methods such as flocculation and sedimentation; (2) increasing phosphorus adsorption capacity in constructed wetlands Filler; (3) followed by advanced treatment units such as land infiltration to absorb and remove phosphorus in the effluent of the constructed wetland.

In the past, there were the following problems in the research and application of constructed wetlands: wetlands dominated by soil or fine sand were easy to clog and the pollutant load was low; relying solely on plant reoxygenation had the problem of insufficient oxygen supply, and the removal effect of ammonia nitrogen was poor. Aeration also increases energy consumption and operating costs; insufficient carbon sources in the back section of the wetland lead to unsatisfactory denitrification and denitrification effects; the introduction of high-efficiency phosphorus removal fillers such as slag, steel slag, and quartz sand mainly relies on adsorption to remove phosphorus. On the one hand, the filler itself The physical and chemical properties of the wetland plants may have a negative impact on the growth of wetland plants. On the other hand, the replacement of the filler after adsorption saturation will lead to an increase in investment costs. The treatment and disposal of the filler after adsorption saturation has potential secondary pollution and other issues.

Contents of the invention

One of the objectives of the present invention is to provide a double-layer constructed wetland system for enhanced nitrogen and phosphorus removal from sewage, which is small in floor area, not easy to block, good in nitrogen and phosphorus removal, and low in investment and operation costs. The system provides an effective way for decentralized sewage treatment in villages and towns.

Another object of the present invention is to provide an operation method for a double-layer constructed wetland system that strengthens nitrogen and phosphorus removal from sewage.

For realizing above-mentioned purpose of the invention, technical scheme of the present invention is:

A double-layer constructed wetland system that strengthens denitrification and phosphorus removal of sewage, including an upper wetland placed inside the pool body, a lower wetland, an inlet water distribution system and an outlet water collection system that provide water for the upper wetland and the lower wetland, said The effluent collection pipe of the effluent collection system is placed at the bottom of the lower wetland, the upper wetland is filled with mineral fillers whose main purpose is to remove suspended solids, organic matter, ammonia nitrogen and phosphorus, and the lower wetland is filled with the main purpose of removing total nitrogen A biological filler that is conducive to the growth of microorganisms.

An overflow pipe is provided on the pool body above the upper wetland, and plants are planted in the upper wetland.

The water inlet water distribution system includes an upper water distribution pipe with perforations placed above the upper wetland and a lower water distribution system placed at the interface between the upper wetland and the lower wetland; the upper water distribution pipe and the lower water distribution system pass through straight pipes are connected, and a flow control valve is provided at the intersection.

Coarse pebbles and fine pebbles are filled between the mineral filler in the upper wetland and the biological filler in the lower wetland, and the lower water distribution system is placed between the coarse pebbles and fine pebbles.

The lower water distribution system includes a perforated lower water distribution pipe, a sawtooth overflow distribution water tank and a water distribution tank cover placed above the overflow distribution water tank, and the lower water distribution pipe is placed in the overflow distribution water tank.

Coarse pebbles are filled under the biological filler, and the effluent collection pipe of the effluent collection system is placed among the coarse pebbles.

The water outlet collection system includes a water outlet collection pipe with water inlet holes, a water outlet main pipe and a U-shaped pipe for controlling the liquid level of the upper wetland, and a vent valve is provided at the bottom of the water outlet main pipe.

The height ratio of the mineral filler in the upper wetland to the biological filler in the lower wetland is 4:1˜1:2.

The biological filler is a polyhedral ball with a diameter of 25-50 mm, and its material is polyethylene (PE), polypropylene (PP), reinforced polypropylene (RPP), polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC) and one or more of polyvinylidene fluoride (PVDF), the biological filler is multi-faceted spherical.

The mineral filler is zeolite with a particle diameter of 4-8 mm, or limestone, or a mixture of zeolite and limestone, and the mixing volume ratio of the zeolite and limestone is 4:1-1:4.

An operation method of a double-layer constructed wetland system for strengthening denitrification and dephosphorization of sewage, comprising the following steps:

Step a. The sewage enters the upper wetland and the lower wetland in the pool body through the water inlet distribution system;

Step b. The sewage entering the upper wetland enters the lower wetland after being adsorbed by mineral fillers in the upper wetland, degraded by microorganisms, and absorbed by plants, and mixed with the sewage entering the lower wetland to form mixed water injection;

Step c. The mixed water injection is degraded by the attached and grown microorganisms on the biological filler placed in the lower wetland, and finally enters the effluent collection pipe at the bottom of the lower wetland, and is discharged out of the pool by the effluent collection system.

In the step a, the flow ratio of the sewage entering the upper wetland and the lower wetland is 20:1-1:1. .

The present invention has the following beneficial effects:

a. The mineral filler in the upper layer of the wetland adopts zeolite with a particle size of 4-8mm, or limestone, or a mixture of zeolite and limestone. The particle size is appropriate, and the pollutant load is increased by nearly 50% compared with the traditional artificial wetland method. At the same time, it is not easy to block, because The upper and lower layers of vertical flow artificial wetland are adopted, and the area occupied is reduced by about 50%;

b. Nitrogen and phosphorus nutrients adsorbed by mineral fillers such as zeolite and limestone can be biologically regenerated through microbial degradation and plant absorption, and will not cause secondary pollution due to replacement fillers;

c. The biological carrier filler filled in the lower wetland is easy to attach and grow microorganisms, which strengthens the denitrification effect and improves the denitrification effect of the wetland;

d. The upper water distribution pipes use the terrain drop to oxygenate the falling water, cooperate with the reoxygenation of plants, and jointly provide sufficient dissolved oxygen for the nitrification of the upper wetland, so that there is no energy consumption and operating costs are saved;

e. The lower water distribution system introduces small streams of water into the lower wetlands to supplement carbon sources for denitrification and denitrification in the lower wetlands;

f. The whole system also has the advantages of no excess sludge, simple process flow, easy operation and maintenance, and plants with ornamental and economic value.

Description of drawings

The present invention will be further described below in conjunction with accompanying drawing and specific embodiment:

Fig. 1 is a schematic diagram of a double-layer constructed wetland system for enhancing denitrification and dephosphorization of sewage according to the present invention.

Figure 2 is a side sectional view of the system of Figure 1 .

In the picture:

I. Upper wetland II. Lower wetland

1. Tank body 2. Inlet main pipe 3. Flow control valve

4. Upper water distribution pipe 5. Lower water distribution pipe 6. Sawtooth overflow distribution sink

7. Water outlet collection pipe 8. Water outlet main pipe 9. Vent valve

10. U-shaped pipe 11. Overflow pipe 12. Fine pebbles

12′coarse pebbles 13. Biological filler 14. Mineral filler

15. Plant 16. Straight pipe 17. Cloth sink cover.

Detailed ways

Refer to Figure 1 and Figure 2

The present invention provides a double-layer constructed wetland system for strengthening sewage denitrification and phosphorus removal. Its structure is shown in FIG. II provides an inlet water distribution system and an outlet water collection system. The outlet water collection pipe 7 of the outlet water collection system is placed at the bottom of the lower wetland II, and the upper wetland I is filled to remove suspended solids, organic matter, ammonia nitrogen and phosphorus. The purpose of the mineral filler 14 is to fill the lower wetland II with the biological filler 13 that is conducive to the growth of microorganisms and whose main purpose is to remove total nitrogen. Among them, the mineral filler 14 in the upper wetland is a mixture of limestone and zeolite, its particle size is 4-8mm, the mixing volume ratio is 4:1-1:4, and the filling height is 350-800mm; the biological filler 13 in the lower wetland II It is multi-faceted spherical, with a diameter of 25-50mm, a specific surface area of 460-236m ² /m ³ , a porosity of about 90%, a stack weight of 96-76kg/m ³ , and a compressive strength of ≥6.0N/mm. The filling height is 250-500 mm, and the filling height ratio of the upper mineral filler 14 and the lower biological filler 13 is 4:1-1:2. Biofiller 13 can be made of polyethylene (PE), polypropylene (PP), reinforced polypropylene (RPP), polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC) and polyvinylidene fluoride (PVDF), etc. The purpose of filling the biological filler 13 is to increase the quantity and activity of denitrifying bacteria in the wet ground floor, and strengthen denitrification and denitrification.

The water distribution devices in the upper wetland I and the lower wetland II both use perforated water distribution pipes for water distribution, and the upper wetland I can also use other falling water and oxygenation devices to distribute water. The top of the water distribution device has holes at a certain distance. Small holes of 5-10mm, the upper water distribution pipe 4 is arranged above the upper wetland I, 0.2-1.5m away from the liquid surface of the upper wetland I; the interface between the upper wetland I and the lower wetland II is filled with fine pebbles 12 and coarse pebbles 12 ′, the lower water distribution system is located between the fine cobblestones 12 and the coarse cobblestones 12′, wherein the upper part of the lower water distribution system is covered with fine cobblestones 12 with a particle size of 6-25 mm, and the filling height of the fine cobblestones 12 is 80-200 mm. Supported by coarse pebbles 12' with a particle size of 10-35 mm, the filling height is 80-200 mm. The lower water distribution system includes the lower water distribution pipe 5 with perforations, the sawtooth overflow distribution water tank 6 and the water distribution tank cover 17, wherein the lower water distribution pipe 5 is placed in the sawtooth overflow distribution water tank 6, which can prevent the small holes on the lower water distribution pipe 5 from being surrounded Particle clogging. The upper water distribution pipe 4 and the lower water distribution pipe 5 are connected through a straight pipe 16, and a flow control valve 3 is installed at the intersection, and the flow control valve 3 is used to control the water flow ratio of the upper wetland and the lower wetland to 20:1~ 1:1.

The bottom of the lower wetland II is filled with coarse pebbles 12' supporting biological fillers, the particle size of the coarse pebbles 12' is 10-35 mm, and the filling height is 70-150 mm. The water outlet collection system includes an outlet water collection pipe 7 with water inlet holes, a water outlet main pipe 8 and a U-shaped pipe 10 for controlling the liquid level of the upper wetland. The small hole is placed in the middle of the coarse pebbles 12'. The bottom of the water outlet main pipe 8 is provided with a vent valve 9. The water treated by the wetland is finally collected by the bottom water outlet collection pipe 7, merged into the water outlet main pipe 8, and passed through the water outlet U-shaped pipe 10 emissions. In case of special circumstances, the sewage in the system can be completely emptied directly through the vent valve 9. Wherein, the internal water level of the wetland can be above or below the filling surface, following the principle of "shallow in spring, deep in summer, and dry in autumn".

An overflow pipe 11 is arranged on the wall of the pool body 1 at a certain distance from the upper wetland 1 to the top of the pool. If the system does not operate normally and causes blockage, the sewage can overflow through the overflow pipe 11, so as to prevent sewage from overflowing from the upper edge of the system and pollute the surrounding environment .

The main purpose of the upper wetland I is to remove suspended matter, organic matter, ammonia nitrogen and phosphorus, and plants 15 are also planted in the upper wetland I. The mineral filler limestone can adsorb phosphorus and zeolite can adsorb ammonia nitrogen, making full use of the different adsorption characteristics of the two. The nitrogen and phosphorus nutrients adsorbed on the filler can be removed from the wetland through microbial degradation and plant absorption, so as to realize the filler The biological regeneration avoids the investment cost of replacing the filler and the possible secondary pollution. The plants 15 to be planted can be emergent plants such as reeds and cattails, or phytoplankton such as duckweed, or ornamental flowers, etc., and the specific needs can be selected according to the local climate and environment.

The present invention provides a double-layer constructed wetland system and its operating method for strengthening sewage denitrification and dephosphorization, which mainly includes the following steps:

Step a. Sewage enters the upper wetland I and the lower wetland II in the pool body 1 through the water distribution system. The water enters the upper wetland I through the upper water distribution pipe 4 for falling water and oxygenation, and cooperates with the reoxygenation of plants to provide sufficient dissolved oxygen for the removal of organic matter and nitrification in the upper wetland I. The lower water is mainly for the denitrification of the lower wetland II. Nitrogen supplements carbon source;

Step b. The sewage entering the upper wetland I enters the lower wetland II after being adsorbed by the mineral filler 14 in the upper wetland I, degraded by microorganisms, and absorbed by plants, and mixed with the sewage entering the lower wetland II to form mixed water injection;

Step c. After the mixed water injection is degraded by the attached and grown microorganisms on the biological filler 13 in the lower wetland II, it finally enters the effluent collection pipe 7 at the bottom of the lower wetland II and is discharged from the effluent collection system.

Apply the present invention to the treatment of domestic sewage in a certain village, the designed influent flow rate is 10m ³ /d, the sewage water quality is: SS: 20-40mg/L, COD: 100-200mg/L, BOD ₅ : 50-100mg/L , NH ₃ -N: 15-40 mg/L, TN: 25-50 mg/L, TP: 2.0-5.0 mg/L.

The sewage first flows into the wetland system inlet main pipe 2, and then through the flow control valve 3, is distributed to the upper water distribution pipe 4 and the lower water distribution pipe 5 in a ratio of 3:1. The water in the upper layer falls to the upper layer of the upper wetland I evenly through the small holes at the top of the upper layer water distribution pipe 4, and the sewage that has been oxygenated by the falling water vertically infiltrates into the limestone and zeolite filling area of the upper layer, and the residence time is 2 days. And plant absorption and other functions, effectively remove suspended solids, organic matter, ammonia nitrogen, phosphorus and other pollutants. The water in the lower layer overflows through the straight pipe 16 from the lower water distribution pipe 5 through the lower layer sawtooth overflow distribution water tank 6, and after mixing with the upper layer effluent in the cobblestone filling area of the middle layer, it flows evenly into the lower layer biofilling area 13, and stays in the lower wetland II for 1 day. Remove nitrate nitrogen. After the final treatment, the water is collected by the water outlet collection pipe 7 at the bottom of the lower wetland II and merged into the water outlet main pipe 8, and then discharged through the outlet U-shaped pipe 10.

During operation, the internal water level of the wetland is 0-100mm above the surface of the filler in spring, 100-200mm above the surface of the filler in summer, and 50-100mm below the surface of the filler in winter. The water level is adjusted by adjusting the height of the outlet U-shaped pipe 10; The unit is functioning normally with no clogging or need to be emptied.

The treatment results show that during stable operation, the effluent quality is as follows: SS: 5-10mg/L, COD: 25-60mg/L, BOD5: 5-20mg/L, NH ₃ -N: 5-15mg/L, TN: 8～20mg/L, TP: 0.5～1.0mg/L, pH: 6～9, the turbidity is stable below 5NUT, and the effluent water quality meets the first-class B standard of "Pollutant Discharge Standards for Urban Sewage Treatment Plants" (GB18918-2002) .

The above description is only an embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention within.

Claims (2)

1. the double-layer artificial wetland system of a strengthening sewage denitrification and dephosphorization is characterized in that: comprise the upper strata wetland (I) that places pond body (1) inner, lower floor's wetland (II), the water inlet water distribution system of water into be provided and go out water collection system for upper strata wetland (I) and lower floor's wetland (II);

Fill the biologic packing material (13) that is beneficial to attached growth of microorganisms in the filling mineral filler (14) in the said upper strata wetland (I), lower floor's wetland (II), be filled with pebbles between the mineral filler (14) of upper strata wetland (I) and the biologic packing material (13) of lower floor's wetland (II);

Mineral filler (14) in the described upper strata wetland (I) and biologic packing material (13) aspect ratio in lower floor's wetland (II) are 4: 1～1: 2, and biologic packing material (13) below is filled with thick pebbles (12 ');

Said mineral filler (14) is zeolite or the Wingdale of 4～8mm for particle diameter, or the mixture of Wingdale and zeolite;

Said biologic packing material (13) is the many-sided ball of diameter 25～50mm, and its material is one or more in Vilaterm (PE), Vestolen PP 7052 (PP), RPP (RPP), SE (PVC), chlorinated polyvinyl chloride (CPVC) and the pvdf (PVDF);

Said water inlet water distribution system comprises the upper strata water distributor (4) that has perforation that places upper strata wetland (I) top and places upper strata wetland (I) and lower floor's water distribution system of lower floor's wetland (II) interface; Upper strata water distributor (4) and lower floor's water distribution system are connected through straight tube (16); Its intersection is provided with flowrate control valve (3); Lower floor's water distribution system comprises lower floor's water distributor (5), the sawtooth overflow cloth tank (6) that has perforation and places the cloth sink cover (17) of overflow cloth tank (6) top; Lower floor's water distributor (5) places in the said overflow cloth tank (6), and lower floor's water distribution system places between the pebbles;

Saidly go out water collection system and comprise the U-shaped pipe (10) that goes out water collection pipe (7), outfall sewer (8) and control upper strata wetland liquid level that has the prosopyle; Outfall sewer (8) bottom is provided with blow-off valve (9), goes out water collection pipe (7) and places the thick pebbles (12 ') of lower floor's wetland (II) bottom middle.

2. the double-layer artificial wetland system of strengthening sewage denitrification and dephosphorization according to claim 1, it is characterized in that: the working method of said artificial wet land system may further comprise the steps:

Step a. sewage gets into pond body (1) interior upper strata wetland (I) and lower floor's wetland (II) through the water inlet water distribution system, and the flooding velocity ratio that sewage gets into upper strata wetland (I) and lower floor's wetland (II) is 20: 1～1: 1;

Step b. gets into lower floor's wetland (II) after getting into mineral filler (14) absorption, microbiological deterioration and the plant absorbing effect of sewage in the wetland of upper strata in the upper strata wetland (I), and mixes water filling with mixed formation of sewage that gets in lower floor's wetland (II);

Step c is mixed the biologic packing material (13) of water filling through placing lower floor's wetland (II), after the Degradation of adhering to the mikrobe of growth on it is handled, finally gets into the water collection pipe that of lower floor's wetland (II) bottom, discharges by going out water collection system.

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