CN110746057B

CN110746057B - Artificial rapid infiltration system for improving processing capacity of nitrogen and phosphorus pollutants in rainwater through medium modification

Info

Publication number: CN110746057B
Application number: CN201911201218.2A
Authority: CN
Inventors: 王辉; 王沐晴; 卞兆勇
Original assignee: Beijing Forestry University
Current assignee: Beijing Forestry University
Priority date: 2019-11-29
Filing date: 2019-11-29
Publication date: 2022-03-11
Anticipated expiration: 2039-11-29
Also published as: CN110746057A

Abstract

The invention discloses an artificial rapid infiltration system for improving the capacity of processing pollutants such as nitrogen, phosphorus and the like in rainwater through medium modification. Aiming at the defect that the existing rapid infiltration system has poor nitrogen and phosphorus removal effect, the nitrogen and phosphorus removal capability of the system is improved by modifying vermiculite with chitosan and optimizing the technological parameters of the system. The technology mixes modified vermiculite with soil river sand in proportion, distributes water once every 48h with hydraulic load of 2m/d, feeds water for 3h once, dries for 45h, has soil layer thickness of 70-100 cm, and feeds water in segments at a ratio of 2:1 at a position 30cm below the soil layer, and realizes standard treatment of the artificial rapid infiltration system on nitrogen and phosphorus pollutants under the process condition. In general, the structure is simple, the occupied area is small, and the treatment effect is good.

Description

Artificial rapid infiltration system for improving processing capacity of nitrogen and phosphorus pollutants in rainwater through medium modification

Technical Field

The invention relates to the technical field of sewage treatment, in particular to an artificial rapid infiltration system for improving the treatment capacity of pollutants such as nitrogen and phosphorus in rainwater through medium modification.

Background

A Constructed rapid infiltration system (CRI) is a type of land treatment, which is a controlled process of putting sewage on the surface of an artificially Constructed infiltration medium, so that the sewage undergoes different physical, chemical and biological actions in the downward infiltration process, and finally the aim of purifying the sewage is achieved. On the basis of research and summary of various land treatment and rapid infiltration systems, aiming at the defects of low hydraulic load, small unit area treatment capacity and the like commonly existing in the traditional sewage land treatment system, the method develops a novel sewage treatment technology with self characteristics step by taking the advantages of the sewage rapid infiltration land treatment system and the constructed wetland system as reference, and has wide development space.

The system is characterized in that the artificial infiltration medium with better permeability is used as a material to replace natural soil, some fillers with special functions are added, and the operation is carried out in a dry-wet alternating mode, so that the system not only can ensure higher hydraulic load, but also can meet the requirement of yielding water. At present, research progresses on rainfall runoff pollution control technologies at home and abroad are different, but a land treatment system becomes one of main means for controlling and reducing rainfall runoff pollution in various countries. The technology not only solves the defects that the adoption of a sedimentation tank or a regulation and storage tank causes idle in dry days, large occupied area and poor feasibility and economical efficiency of direct utilization of rainwater; the purification capacity of the soil is fully utilized, so that the aim of reducing rainfall runoff pollution is fulfilled.

Due to the influences of climates and soil textures of different regions, optimal process parameters of all regions are different, and therefore a certain process parameter range is not provided for the application of the rapid infiltration system, in addition, the efficiency of removing pollutants such as nitrogen and phosphorus by the rapid infiltration system in the prior art is still low, the pollutants in the effluent water passing through the rapid infiltration system are not completely removed, and therefore adverse effects such as water eutrophication and black and odorous are caused after the effluent water is discharged into a natural water body, and on the basis, the rapid infiltration system in the prior art cannot achieve the purpose of rapidly and thoroughly purifying the pollutants in the rainwater runoff.

Disclosure of Invention

In order to solve the technical problems, the invention provides an artificial rapid infiltration system for improving the capacity of treating pollutants such as nitrogen and phosphorus in rainwater through medium modification, and a set of efficient nitrogen and phosphorus removal system is constructed through the matching of a proper infiltration medium proportion, process parameters and an operation mode, so that the purification of pollutants in rainwater runoff by the artificial rapid infiltration system is realized.

In order to achieve the purpose, the invention provides an artificial rapid infiltration system for improving the capacity of treating pollutants such as nitrogen, phosphorus and the like in rainwater through medium modification.

Preferably, the media in the medium layer are uniformly mixed, and the soil is aired and then passes through a 2mm sieve, river sand, vermiculite and limestone with the particle sizes of 1-2 mm.

Preferably, the volume ratio of the soil to the river sand is 1:1, the doping amount of the vermiculite is 15% of the total volume of the soil and the river sand, and the doping amount of the limestone is 8% of the total volume of the soil and the river sand.

The appropriate vermiculite doping proportion can ensure the efficiency of the system for removing pollutants and the economy.

Preferably, the thickness of the medium layer is 70-100 cm, the thickness of the overflow layer is 20-30 cm, and the thickness of the drainage layer is 20-30 cm.

A layer of cobblestones with small particle size is paved on the percolation medium, which is favorable for avoiding flushing the upper-layer filler by water inflow; the bottom is provided with a bearing drainage layer, a gravel layer with large void ratio and good permeability is filled, and the layer mainly has the functions of supporting the infiltration medium on the upper part, collecting the bottom effluent and enabling the effluent to flow out of the system smoothly.

Preferably, the filling filler of the drainage layer is cobblestones, and the particle size of the cobblestones filled in the drainage layer is 2-4 cm.

Preferably, laying an iron wire net and geotextile on the medium layer and the drainage layer; the water draining layer is used for supporting the medium layer and preventing the medium in the medium layer from falling into the water draining layer.

Preferably, the vermiculite is modified vermiculite, and the modification process comprises the following steps: screening vermiculite with 2mm sieve, using 1mol/L HNO₃Stirring and soaking for 2h, taking out and washing, removing soluble impurities, drying in an oven to constant weight, taking the pretreated vermiculite and chitosan, adding 1mol/L NaOH solution into a beaker according to the mass ratio of the chitosan to the vermiculite of 1:20-50, stirring for 24h, soaking in distilled water, washing until the pH value is constant, and drying in the oven to constant weight for later use.

By HNO₃Pretreatment, on the one hand, can make K in vermiculite skeleton⁺、Mg²⁺The metal cations are dissolved out, and on the other hand, a small amount of impurities such as populus carbonate and the like attached to the surface of the vermiculite can be dissolved; and proper NaOH pretreatment can neutralize H exchanged to vermiculite in acid treatment link⁺And the influence of pH in the use process is avoided. In addition, the sodium hydroxide solution can lead Na in the modification process⁺Enter the vermiculite, thereby improving the ion exchange performance of the vermiculite and being beneficial to removing nitrogen and phosphorus.

Preferably, the water inlet pipe inside the medium layer is arranged at a position 30cm away from the upper surface of the medium layer.

According to the second technical scheme, in the method for treating pollutants such as nitrogen and phosphorus in rainwater by using the artificial rapid infiltration system, sewage to be treated simultaneously enters water from the surface of the medium layer and the water inlet pipe in the medium layer and is discharged from the water outlet arranged at one side of the water discharging layer, the entering water adopts a flooding-drying alternative operation mode, the hydraulic load is 2m/d, the hydraulic load period is 48 hours, the water distribution time is 3 hours, the drying time is 45 hours, and the system outlet water is discharged from the water outlet at one side of the water discharging layer.

Preferably, the ratio of the water inlet on the surface of the dielectric layer to the water inlet in the dielectric layer is 2: 1.

Compared with the prior art, the invention has the following beneficial effects:

the invention provides an artificial rapid infiltration system suitable for rainwater treatment, wherein a filler with a proper proportion is filled in the system, water is fed in by adopting a segmented water feeding mode to construct a high-efficiency nitrogen and phosphorus removal system, and the modified vermiculite further improves the adsorption and interception capacity of the system on pollutants and improves the adsorption effect of the system on the pollutants. The ammonia nitrogen is converted into nitrate nitrogen through the nitration reaction of the upper aerobic section, organic matters required by the lower anaerobic section are provided in a sectional water inlet mode, the nitrate nitrogen is removed through the denitrification reaction of the lower anaerobic section, cations in vermiculite and limestone can be adsorbed and precipitated with phosphate ions, and therefore nitrogen and phosphorus in rainwater can be removed. The invention operates under higher hydraulic load, the mixed filling of the medium improves the porosity and the adsorption capacity of the system, and the reasonable soil layer thickness and the selection of the sectional water inlet position further improve the removal effect of the system on pollutants, particularly nitrogen. And the structure is simple, the operation is simple, the occupied area is small, the operation cost is low, and the treatment effect is good.

The soil, sand, vermiculite and limestone are mixed and filled, so that the porosity of the system is improved, the reoxygenation effect and the anti-blocking performance of the system are improved, the adsorption and interception effect of the system on pollutants such as nitrogen, phosphorus and the like can be further improved by using the modified vermiculite, and the concentration of TN and TP in the discharged water is reduced; along with the extension of water inlet time, the microorganisms in the system breed by utilizing nutrient substances intercepted by the medium, and the limestone can effectively supplement the alkalinity consumed by the system during the nitration reaction, so that the system is kept in a pH range suitable for the growth and the breeding of the microorganisms, and the effluent of the system is prevented from appearingAnd (4) acidity. The adoption of a larger hydraulic load cycle and a lower wet-dry ratio is beneficial to fully degrading the pollutants adsorbed and intercepted by the medium in the dry-falling period of the system, and leaves enough adsorption sites for the next water inlet, thereby ensuring the removal effect of the system on the pollutants. Along with the extension of the running time of the system, the upper part of the system is fully contacted with the outside to form an aerobic section, the lower part of the system is gradually changed into an anaerobic section, the nitrification reaction is completed in the aerobic section at the upper part of the system, and the denitrification reaction is completed under the anaerobic condition through the action of denitrifying bacteria, namely, the bacteria convert Nitrate (NO)₃ ^-) Nitrogen (N) in (A) is passed through a series of intermediates (NO)₂ ^-、NO、N₂O) reduction to nitrogen (N)₂) The biochemical process of (2) and the denitrification reaction are completed in the lower half section of the system, and the water inlet pipe is arranged at a position 30cm away from the surface layer for step water inlet, so that the carbon source required by the denitrification reaction in the anaerobic section of the system can be effectively supplemented, the denitrification reaction intensity of the section is improved, and the conditions of nitrate nitrogen in the effluent and overhigh TN concentration caused by insufficient denitrification reaction due to insufficient carbon source in the section are avoided. The soil layer range is selected to be 85cm, so that the economical efficiency of the system on pollutant removal can be ensured, and meanwhile, the economical efficiency of the system can be ensured. The cobblestones with large particle size filled in the drainage layer can play the roles of quickly collecting water, draining water and resisting blockage

Drawings

Fig. 1 is a schematic structural view of an artificial rapid infiltration system of the present invention, wherein 1 is an overflow layer, 2 is a medium layer, 3 is a drainage layer, 4 is a water inlet pipe, 5 is a water inlet pipe, and 6 is a water outlet.

Detailed Description

Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The specification and examples are exemplary only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.

Example 1

The artificial rapid infiltration system is prepared according to the structural schematic diagram of fig. 1, a device is made of PVC plastics, the whole body is a cylinder, the height is 130cm, the length and the width are 60cm, a medium layer 2 is 85cm, an overflow layer 1 is 25 cm, a water outlet layer 3 is 20cm, water distribution pipes are arranged on the surface of the medium layer and at a position 30cm away from the surface, the medium layer is formed by uniformly mixing soil, river sand, vermiculite and limestone with the particle size of less than 2cm, the adding ratio of the soil to the river sand is 1:1, the doping amount of the vermiculite is 15% of the total volume of the soil and the river sand, the doping amount of the limestone is 8% of the total volume of the soil and the river sand, and the particle size of cobbles filled in the water drainage layer is 2-4 cm.

The initial concentrations of COD, ammonia nitrogen, TP and TN in the sewage are respectively 173-185 mg/L, 7-8 mg/L, 0.3-0.4 mg/L and 7.8-9.5 mg/L, the sewage is subjected to sewage treatment by adopting the artificial rapid infiltration system, the inflow water adopts a flooding-falling dry alternate operation mode, the hydraulic load is 2m/d, the hydraulic load cycle is 48 hours, the water distribution time is 3 hours, the falling dry time is 45 hours, the system effluent is discharged from a water outlet 6 on the right side of a drainage layer 3, and the average effluent concentrations of COD, ammonia nitrogen, TP and TN in the sewage at a detection drainage port are respectively 32.8mg/L, 1.35mg/L, 0.151mg/L and 5.62 mg/L.

Example 2

The difference from the example 1 is that the added vermiculite is modified vermiculite, and the modification method comprises the following steps: sieving natural vermiculite with 2mm sieve, and adopting 1mol/L HNO₃Stirring and soaking for 2h, taking out and washing, removing soluble impurities, drying in an oven to constant weight, then taking 10g of the pretreated vermiculite and chitosan, placing the pretreated vermiculite and chitosan into a beaker according to the mass ratio of the chitosan to the vermiculite of 1:40, adding 100ml of 1mol/L NaOH solution, stirring for 24h, soaking in distilled water, washing until the pH value is constant, and drying in the oven to constant weight for later use.

The average effluent concentrations of COD, ammonia nitrogen, TP and TN in the sewage of the drainage are respectively detected to be 15.29mg/L, 0.81mg/L, 0.018mg/L and 4.21 mg/L.

Example 3

The difference from the example 2 is that only the water inlet pipe is arranged on the surface of the medium layer, the water outlet is arranged on the water drainage layer, and the average outlet water concentration of COD, ammonia nitrogen, TP and TN in the sewage at the detected water drainage position is respectively 13.42mg/L, 0.46 mg/L, 0.0141mg/L and 6.06 mg/L.

Claims

1. An artificial rapid infiltration system for improving the treatment capacity of nitrogen and phosphorus pollutants in rainwater through medium modification is characterized by comprising an overflow layer at the upper end, a middle medium layer and a drainage layer at the bottom, wherein the medium layer comprises soil, river sand, vermiculite and limestone, water inlet pipes are respectively arranged on the surface of the medium layer and in the medium layer, and a water outlet is arranged at one side of the bottom of the drainage layer;

the media in the medium layer are uniformly mixed, and the soil is aired and then passes through a 2mm sieve, and the particle sizes of the river sand, the vermiculite and the limestone are all 1-2 mm;

the volume ratio of the soil to the river sand is 1:1, the doping amount of the vermiculite is 15% of the total volume of the soil and the river sand, and the doping amount of the limestone is 8% of the total volume of the soil and the river sand;

the thickness of the medium layer is 70-100 cm, the thickness of the overflow layer is 20-30 cm, and the thickness of the drainage layer is 20-30 cm;

the vermiculite is modified vermiculite, and the modification process comprises the following steps: screening vermiculite with 2mm sieve, using 1mol/L HNO₃Stirring and soaking for 2h, taking out and washing, removing soluble impurities, drying in an oven to constant weight, taking the pretreated vermiculite and chitosan, adding 1mol/L NaOH solution into a beaker according to the mass ratio of the chitosan to the vermiculite of 1:20-50, stirring for 24h, soaking in distilled water, washing until the pH value is constant, and drying in the oven to constant weight for later use.

2. The artificial rapid infiltration system for improving the treatment capacity of nitrogen and phosphorus pollutants in rainwater through medium modification according to claim 1, wherein the filling filler of the drainage layer is cobblestones, and the particle size of the cobblestones filled in the drainage layer is 2-4 cm.

3. The rapid infiltration system for improving the treatment capacity of nitrogen and phosphorus pollutants in rainwater through medium modification according to claim 1, wherein a wire mesh and a geotextile are laid on the medium layer and the drainage layer.

4. The system of claim 1, wherein the inlet pipe is positioned 30cm from the top surface of the medium layer.

5. The method for treating nitrogen and phosphorus pollutants in rainwater by using the artificial rapid infiltration system according to any one of claims 1 to 4, wherein the sewage to be treated simultaneously enters from the water inlet pipe on the surface of the medium layer and in the medium layer and is discharged from the water outlet arranged on one side of the water discharging layer, the entering water adopts a flooding-drying alternative operation mode, the hydraulic load is 2m/d, the hydraulic load period is 48h, the water distribution time is 3h, the drying time is 45h, and the system outlet water is discharged from the water outlet on one side of the water discharging layer.

6. The method for processing nitrogen and phosphorus pollutants in rainwater by using the artificial rapid infiltration system according to claim 5, wherein the ratio of the water inlet on the surface of the medium layer to the water inlet inside the medium layer is 2: 1.