CN112919631A

CN112919631A - Graded biofiltration medium, preparation method thereof and graded biofiltration system

Info

Publication number: CN112919631A
Application number: CN202110133014.0A
Authority: CN
Inventors: 贺卫宁; 马晶伟; 陆先镭; 林潇; 陈世洋; 施周; 陈蕃; 邓征宇
Original assignee: Hunan University; China Machinery International Engineering Design and Research Institute Co Ltd
Current assignee: Hunan University; China Machinery International Engineering Design and Research Institute Co Ltd
Priority date: 2021-01-29
Filing date: 2021-01-29
Publication date: 2021-06-08
Anticipated expiration: 2041-01-29
Also published as: CN112919631B

Abstract

The invention discloses a graded biological filtration medium, a preparation method thereof, and a graded biological filtration system. Bioretention composite media filler for secondary treatment of primary rainwater and/or confluent overflow sewage for secondary treatment, biological filter filler includes volcanic rock; bioretention composite media filler includes the following mass percentages: 3% to 10% of water supply plant sludge, Coarse sand 50% to 60%, fine sand 10% to 15%, planting soil 20% to 25%, coconut bran 2% to 8%. The graded biological filter medium of the present invention includes a biological filter filler for primary treatment of initial rainwater and/or combined overflow sewage and a bioretention composite media filler for secondary treatment, which can not only ensure that after the treatment by the graded biological filter medium, The quality of the effluent can be improved, and the blockage of the bioretention composite medium packing due to excessive load can be avoided.

Description

Graded biofiltration medium, preparation method thereof and graded biofiltration system

Technical Field

The invention relates to the field of sponge city construction and low-impact development, in particular to a graded biofiltration medium. In addition, the invention also relates to a preparation method and a graded biofiltration system comprising the graded biofiltration medium.

Background

In recent years, the control of water pollution in China is increasing, but the trend of water pollution deterioration is not completely restrained, and simultaneously, with the effective control of point source pollution, the problem of non-point source pollution caused by initial rainwater, combined overflow sewage (CSO for short) and the like attracts more and more attention in China. Through national popularization and publicity, the concept of treating rainwater by using low-impact development technology is accepted by more and more people. At present, the methods for treating the surface source pollution of initial stage rainwater, CSO and the like can be roughly divided into three types: the method mainly comprises the following steps of source, process and tail end control, and commonly used control measures mainly comprise a biological retention facility, an overflow regulation and storage tank, first-stage treatment of chemical enhancement, an artificial wetland and the like. However, the centralized release position of the rainwater and CSO pollution sources in the initial stage of China is often limited in space, the existing conventional control measures are difficult to implement due to large occupied area or high in operation cost, the pollutant removal rate is greatly influenced by the change of seasons, water quantity and water quality, the treatment effect is unstable, and the centralized release position cannot adapt to the change characteristics of the rainwater and CSO pollution sources in China.

The biological filtering facility uses the filler as a biological membrane carrier, purifies sewage by utilizing the oxidation and decomposition action of microorganisms in the biological membrane, the adsorption and interception action of the filler and the biological membrane, the food chain graded predation action formed along the water flow direction and the denitrification action of a microenvironment and an anaerobic section inside the biological membrane, and is a biological treatment technology commonly used in sewage treatment. But the treatment effect is poor when aeration is not performed and the load is high. Meanwhile, the performance of the filler has the greatest influence on the treatment efficiency, the construction cost and the operating cost of the biological filtration facility. For many years, people have been dedicated to research and develop the filler with large specific surface area, large microorganism attachment amount, good operation effect and low price.

Bioretention facilities originated in the united states at the end of the nineties of the twentieth century and have gradually become widely used runoff rainwater treatment facilities abroad due to their ability to effectively control non-point source pollution and their flexibility in size, layout, location, etc. In recent years, along with the gradual development of sponge city construction in China, biological detention facilities gradually draw attention of related researchers in China, and the possibility of treating wastewater from various sources is discussed. One of the basic raw materials of the bioretention facility is a composite medium filler with high water retention, strong permeability and slow release of organic matters. The composite medium filler in the prior art mainly has four forms: firstly, the composite medium filler takes humus as a basic raw material; secondly, the peat is used as a composite medium filler of the basic raw material; thirdly, the sand is used as a composite medium filler of the basic raw material; and fourthly, the composite medium filler takes the planting soil as a basic raw material. However, nutrients in humus soil and planting soil are easily released to a receiving water body along with runoff, and the water permeability is poor; although the permeability of the sandy soil is good, the water retention is poor, the plant selection is limited, and the landscape effect is influenced; peat belongs to non-renewable natural resources, and peat mining is prohibited in many areas. Therefore, a composite medium filler which can fix phosphorus, remove nitrogen, reduce secondary pollution and can be developed sustainably is needed.

Disclosure of Invention

The invention provides a graded biological filter medium, a preparation method thereof and a graded biological filter system, which are used for solving the technical problems that the existing pollutant removing effect for treating initial rainwater and/or combined overflow sewage is unstable, the change characteristics of the initial rainwater and/or combined overflow sewage in China cannot be adapted, the treatment mode is single, various indexes of water quality cannot be met, the cost of used filler is high, and the popularization and the application cannot be realized.

The technical scheme adopted by the invention is as follows:

a graded biofiltration media comprising: the biological filter filler is used for carrying out primary treatment on the initial rainwater and/or combined overflow sewage, and the biological retention composite medium filler is used for carrying out secondary treatment on the initial rainwater and/or combined overflow sewage after primary treatment, and the biological filter filler comprises volcanic rock; the biological retention composite medium filler comprises the following components in percentage by mass: 3-10% of water supply plant sludge, 50-60% of coarse sand, 10-15% of fine sand, 20-25% of planting soil and 2-8% of coconut coir.

Further, the initial infiltration rate of the biological retention composite medium filler is more than or equal to 4.2 multiplied by 10^-5m/s, stable infiltration rate not less than 2.2X 10^-5m/s, pH of 5.5-6.5 and burning weight loss rate (LOI) of organic matters of 2.5-3.5 percent.

Furthermore, the average grain diameter of the coarse sand is more than or equal to 0.5mm, and the fineness modulus is 3.1-3.7; the fine sand has an average particle size of 0.25-0.35 mm and a fineness modulus of 1.6-2.2; the permeability of the planting soil is more than 3.5 multiplied by 10^-6m/s, organic matter content is more than 5%, pH value is 6-8, and cation exchange capacity is more than 5mep/100 g; the pH value of the coconut coir is 5.5-6.5, and the EC value (conductivity) of the coconut coir is 0.5-0.9.

Furthermore, the volcanic rock has an average porosity of 0.3-0.4, a mud content of less than 0.4%, and a specific surface area of more than 9.5m²The dissolubility of hydrochloric acid is less than 3 percent per gram.

According to another aspect of the present invention, there is also provided a method for preparing a bioretention composite media filler, comprising the above-mentioned method for preparing a graded biofiltration media, comprising the steps of:

s1: spreading 60% of dewatered sludge in a water supply plant for drying in the sun, turning over once a day, and continuously turning over for 5-7 days;

s2: crushing the water supply plant sludge dried in the sun in the step S1, and sieving to obtain water supply plant sludge particles;

s3: soaking the coconut coir without the coconut shell in water, draining the residual water when the volume of the coconut coir is expanded to 3-4 times, flushing the coconut coir while draining water, repeatedly cleaning for at least 3 times to remove salt, and drying in the air;

s4: stirring and mixing the sludge particles obtained in the step S2 and the coconut coir obtained in the step S3 with coarse sand, fine sand and planting soil to obtain a bioretention composite medium filler;

the preparation method of the biological filtering filler comprises the following steps: cleaning the volcanic rock, soaking the volcanic rock in water for more than 48h, taking out the volcanic rock after detecting that the concentration of pollutants in the water does not rise after soaking, and airing.

Further, the thickness of the sludge spread in the step S1 is 15 cm-20 cm; the size of the sieve holes sieved in the step S2 is 3 mm-5 mm.

According to another aspect of the present invention, there is also provided a staged biofiltration system comprising: the volcanic rock layer formed by the biological filter filler and the composite medium filler layer formed by the biological retention composite medium filler; the biological filter tank is used for filtering and biologically degrading the initial rainwater and/or the combined overflow sewage, and the biological retention tank is used for filtering, dephosphorizing and denitriding the initial rainwater and/or the combined overflow sewage after being treated by the biological filter tank; the biological filtration tank comprises: the device comprises a gravel water distribution layer, a volcanic rock layer and a first water storage layer, wherein the gravel water distribution layer is used for uniformly distributing introduced initial rainwater and/or combined overflow sewage, the volcanic rock layer is used for coarsely filtering and solidifying microorganisms to realize biodegradation of the initial rainwater and/or combined overflow sewage after uniform water distribution through the gravel rock layer, and the first water storage layer is used for retaining the initial rainwater and/or combined overflow sewage after filtration through the volcanic rock layer to enable the biological filtration tank to form a stable anoxic/anaerobic environment; the bioretention pond includes: the second water storage layer used for storing the initial rainwater overflowed by the first water storage layer and/or the combined overflow sewage, the covering layer used for preserving water for the composite medium packing layer and preventing the initial rainwater and/or the combined overflow sewage from directly impacting the composite medium packing layer, the composite medium packing layer used for filtering, dephosphorizing and denitriding the initial rainwater and/or the combined overflow sewage after passing through the covering layer and the gravel drainage layer used for quickly draining the initial rainwater and/or the combined overflow sewage after being treated by the composite medium packing layer are sequentially arranged from top to bottom along the flowing direction of the initial rainwater and/or the combined overflow sewage.

Furthermore, the thickness of the composite medium filler layer is 800 mm-1000 mm.

Furthermore, the thickness of the volcanic rock layer is 1500 mm-1800 mm.

Furthermore, volcanic rock layers adopt volcanic rock particles with non-single particle size, and the average particle size of the volcanic rock particles is 10-20 mm.

The invention has the following beneficial effects:

the graded biofiltration medium comprises a biofiltration filler for primary treatment of initial rainwater and/or combined overflow sewage and a bioretention composite medium filler for secondary treatment, wherein the biofiltration filler comprises volcanic rock, and the bioretention composite medium filler comprises: water supply plant sludge, coarse sand, fine sand, planting soil and coconut coir. The biological filter filler adopts a volcanic filter material which is rich in mineral reserves, easy to mine, low in price, large in specific surface area, light in specific gravity, not easy to block, corrosion-resistant, high in film forming speed, good in mechanical strength and chemical stability as the biological filter filler, and has strong adaptability to CSO with different water qualities and water amounts. The bioretention composite medium filler comprises water plant sludge, and the filler medium required by low-influence development is manufactured by using sludge which is difficult to treat by a town water supply plant, so that the sludge produced by the town water supply plant which is difficult to treat is changed into valuable, and the removal of total phosphorus by a bioretention facility can be improved. The biological filtering filler for the first-stage treatment and the biological retention composite medium filler for the second-stage treatment can ensure the quality of effluent treated by the graded biological filtering medium and avoid the blockage of the biological retention composite medium filler caused by overhigh load.

The invention relates to a graded biofiltration medium, wherein a bioretention composite medium filler comprises water supply plant sludge, coarse sand, fine sand, planting soil and coconut coir. Coconut coir in the bioretention composite medium filler can expand to 3-4 times of the original volume after meeting water, the original volume can be restored after water transpiration, the porosity in the bioretention composite medium filler is changed due to expansion and contraction, aerobic and anaerobic processes are formed, nitrification and denitrification conditions are provided for biological nitrogen removal, and nitrogen in initial rainwater and/or combined overflow sewage can be generated into nitrogen for removal; and meanwhile, the coconut coir has good water absorption and water retention, so that the water retention effect of the bioretention composite medium filler is effectively improved, and a good environment is provided for the growth of plants. The coarse sand has the filtering and adsorbing effects, and can also enable the permeability of the bioretention composite medium filler to reach 150mm/h, and the permeability of soil is only 20 mm/h-30 mm/h generally. The water plant sludge is rich in metal oxides or hydroxides, has strong adsorption effect on phosphorus, does not generate secondary release pollution, also plays a role in fertilizer retention, prevents nutrients from being released along with rainwater, and can meet the growth conditions of various landscape plants. The biological retention composite medium filler is prepared by mixing the components in proportion, taking coarse sand as a main framework, fine sand as a polymer, planting soil as a plant and microorganism growth organic matter maintenance body, taking coconut coir as a bridge to build the components to form a good environment for the growth of plants and microorganisms, and removing phosphorus from sludge of a water supply plant in a reinforcing way. The formed biological retention composite medium filler has good permeability, stable filtering performance, good adsorption capacity and good pollutant treatment effect, and is suitable for growth of plants and microorganisms due to proper organic matter content and good water retention.

In addition to the objects, features and advantages described above, other objects, features and advantages of the present invention are also provided. The present invention will be described in further detail below with reference to the accompanying drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is a schematic view of a staged biofiltration system according to a preferred embodiment of the present invention.

The reference numbers illustrate:

1. a biological filtration tank; 2. a bioretention pond;

11. gravel water distribution layer; 12. a volcanic rock formation; 13. a first aquifer;

21. a second aquifer; 22. a cover layer; 23. a composite medium filler layer; 24. and (4) a gravel drainage layer.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

The graded biofiltration media of the present embodiment comprises: the biological filter filler is used for carrying out primary treatment on the initial rainwater and/or combined overflow sewage, and the biological retention composite medium filler is used for carrying out secondary treatment on the initial rainwater and/or combined overflow sewage after primary treatment, and the biological filter filler comprises volcanic rock; the biological retention composite medium filler comprises the following components in percentage by mass: 3-10% of water supply plant sludge, 50-60% of coarse sand, 10-15% of fine sand, 20-25% of planting soil and 2-8% of coconut coir.

50% -60% of coarse sand, the coarse sand is used as the main framework of the biological retention composite medium filler, on one hand, the porosity of the biological retention composite medium filler is kept in a proper range, good water permeability of the biological retention composite medium filler is guaranteed, on the other hand, the biological retention composite medium filler has good filtering and adsorbing effects, and removal of pollutants is facilitated.

10-15% of fine sand, and the fine sand is adopted to ensure good polymerizability of each component particle in the composite medium filler.

20% -25% of planting soil, and by adopting the planting soil in the proportion, on one hand, the planting soil has good polymerizability with other component particles, and on the other hand, the planting soil can provide and maintain organic matters and nutrition suitable for growth of plants and microorganisms in the composite medium filler, so that an environment suitable for growth of plant roots and microorganisms is constructed.

2-8% of coconut coir, the coconut coir can expand to 3-4 times of the original volume after meeting water, the original volume can be restored after water transpiration, the coconut coir with the proportion of 2-8% is uniformly dispersed in the biological retention composite medium filler, the porosity in the biological retention composite medium filler is changed due to expansion and contraction, aerobic and anaerobic processes are formed, nitrification and denitrification conditions are provided for biological nitrogen removal, and nitrogen in initial rainwater and/or combined overflow sewage is generated into nitrogen for removal; and the coconut coir has good water absorption and water retention, effectively improves the water retention of the bioretention composite medium filler, and provides a good environment for the growth of plants.

2% -8% of water supply plant sludge, which is rich in metal oxides or hydroxides, has strong adsorption effect on phosphorus, does not produce secondary release pollution, and also plays a role in fertilizer preservation, so that nutrients are not released along with initial rainwater and/or combined overflow sewage, and the growth conditions of various landscape plants can be met.

Through a large number of experiments, the components are subjected to synergistic interaction, so that the bioretention composite medium filler can remove initial rainwater and/or combined overflow sewage pollution, can retain water and fertilizer, ensures that nutrients are not released along with the initial rainwater and/or combined overflow sewage, and has sufficient permeability. If the proportion is adjusted, the pollutant removal effect, the infiltration rate and the plant growth are all adversely affected.

In this example, the initial infiltration rate of the bioretention composite media filler is not less than 4.2X 10^-5m/s, stable infiltration rate not less than 2.2X 10^-5m/s, pH of 5.5-6.5 and burning weight loss rate (LOI) of organic matters of 2.5-3.5 percent. The initial infiltration rate of the biological retention composite medium filler is more than or equal to 4.2 multiplied by 10^-5m/s, stable infiltration rate not less than 2.2X 10^-5The permeability of m/s is good, the rainwater and/or combined overflow sewage in the initial stage can stably seep downwards, the treatment effect is stable, and the growth of plants and microorganisms can be facilitated. The pH value is 5.5-6.5, which is the most suitable pH value range for the growth of plants with good effect of reducing common pollutants. The burning weight loss rate (LOI) of the organic matters is 2.5-3.5%, and the organic matters contained in the bioretention composite medium in the interval are most suitable for the growth of plants and microorganisms.

In the embodiment, the average grain diameter of the coarse sand is more than or equal to 0.5mm, and the fineness modulus is 3.1-3.7. The fine sand has an average particle size of 0.25-0.35 mm and a fineness modulus of 1.6-2.2; the permeability of the planting soil is more than 3.5 multiplied by 10^-6m/s, organic matter content more than 5%, pH value of 6-8, and cation exchange capacity more than 5mep/100 g. The pH value of the coconut coir is 5.5-6.5, and the EC value (conductivity) of the coconut coir is 0.5-0.9.

In the embodiment, the volcanic rock has an average porosity of 0.3-0.4, a mud content of less than 0.4%, and a specific surface area of more than 9.5m²The dissolubility of hydrochloric acid is less than 3 percent per gram. The biological filter filler uses volcanic rock, has corrosion resistance and inertia, and does not participate in biochemical reaction of a biological film in the environment. The volcanic rock surface has positive charges, is beneficial to the fixation and growth of microorganisms, and has strong hydrophilicity, a large amount of attached biological films and high speed. As a biomembrane carrier, the volcanic biofiltration filler has no harm and inhibition effect on the immobilized microorganisms and does not influence the activity of the microorganisms. The volcanic rock has the advantages of large specific surface area, high aperture ratio, contribution to contact biofilm formation and growth of microorganisms, maintenance of more microorganism amount, contribution to mass transfer process of oxygen, nutrient substances and wastes generated by metabolism in the microbial metabolism process, low production cost, good use effect, no toxicity, no harm and long service life.

The preparation method of the graded biofiltration medium comprises the steps of dehydrating, drying and crushing sludge in a water supply plant to form sludge particles in the water supply plant, removing coconut coir from coconut shells to avoid caking, ensuring that the coconut coir is fully mixed with other components, repeatedly cleaning and removing the salt of the coconut coir, and avoiding the influence of high salinity on the growth of plants and microorganisms. The average grain diameter of the coarse sand is more than or equal to 0.5mm, and the fineness modulus is 3.1-3.7. The fine sand has an average particle size of 0.25-0.35 mm and a fineness modulus of 1.6-2.2. The permeability of the planting soil is more than 3.5 multiplied by 10^-6m/s, organic matter content more than 5%, pH value of 6-8, and cation exchange capacity more than 5mep/100 g. The corresponding performance index is reached by carrying out pretreatment on each component; and then the components are fully mixed to form the bioretention composite medium filler, so that the pollution of initial rainwater and/or combined overflow sewage can be removed, water and fertilizer can be preserved, nutrient substances are not released along with the initial rainwater and/or the combined overflow sewage, and the bioretention composite medium filler has enough permeability. Cleaning volcanic rock filled with biofiltration filler, soaking, and detecting pollution of soaking waterAnd (5) performing physical indexes, and airing.

In this example, the thickness of the sludge spread in step S1 was 15cm to 20 cm. The size of the sieve holes sieved in the step S2 is 3 mm-5 mm. And step S1, spreading the dewatered sludge of the water supply plant to form a sludge layer with the thickness of 15-20 cm, and continuously turning the sludge layer for 5-7 days by using a turning machine, so as to increase the contact oxidation of the sludge of the water supply plant and air and accelerate the stabilization and deodorization of the sludge of the water supply plant. In step S2, the dried sludge of the water supply plant enters a crusher to be crushed, the crushed sludge is sent to a vibrating screen to be screened, the size of the screen hole is 3 mm-5 mm, and the sludge particles of the water supply plant larger than 5mm are sent back to the crusher to be crushed so as to ensure that the sludge particles are fully and uniformly mixed with other components.

As shown in fig. 1, according to another aspect of the present invention, there is also provided a classified biofiltration system comprising: a volcanic rock layer 12 formed by the biological filter filler and a composite medium filler layer 23 formed by the biological retention composite medium filler; a biological filter tank 1 for filtering and biologically degrading the initial rainwater and/or combined overflow sewage, and a biological retention tank 2 for filtering, dephosphorizing and denitrating the initial rainwater and/or combined overflow sewage treated by the biological filter tank 1; the biological filtration tank 1 includes: a gravel water distribution layer 11 for uniformly distributing introduced initial rainwater and/or combined overflow sewage, a volcanic rock layer 12 for coarsely filtering and solidifying microorganisms after uniform distribution of the initial rainwater and/or the combined overflow sewage on the gravel layer to realize biodegradation, and a first water storage layer 13 for retaining the initial rainwater and/or the combined overflow sewage after filtration on the volcanic rock layer 12 to enable the biological filter tank 1 to form a stable anoxic/anaerobic environment are sequentially arranged from bottom to top along the flowing direction of the initial rainwater and/or the combined overflow sewage; the bioretention tank 2 includes: the second aquifer 21 for accumulating the initial rainwater overflowed by the first aquifer 13 and/or the combined overflow sewage, the covering layer 22 for retaining water for the composite medium packing layer 23 and preventing the initial rainwater and/or the combined overflow sewage from directly impacting the composite medium packing layer 23, the composite medium packing layer 23 for filtering, dephosphorizing and denitriding the initial rainwater and/or the combined overflow sewage after passing through the covering layer 22, and the gravel drainage layer 24 for rapidly draining the initial rainwater and/or the combined overflow sewage after passing through the composite medium packing layer 23 are sequentially arranged from top to bottom along the flowing direction of the initial rainwater and/or the combined overflow sewage.

The invention relates to a graded biofiltration system, which comprises a biofiltration tank 1 and a bioretention tank 2. The biological filter tank 1 comprises a gravel water distribution layer 11, a volcanic rock layer 12 and a first water storage layer 13 from bottom to top. The initial rainwater and/or combined overflow sewage are introduced into the gravel water distribution layer 11 to realize uniform water distribution of the initial rainwater and/or the combined overflow sewage, and then are subjected to coarse filtration and microorganism solidification through the volcanic rock layer 12 to realize biodegradation, and then pass through the first water storage layer 13. The gravel water distribution layer 11 can uniformly distribute the initial rainwater and/or the combined overflow sewage, so that pollutants in the initial rainwater and/or the combined overflow sewage can enter the volcanic rock layer 12 and then fully contact with the biological filter filler to be biodegraded so as to purify the sewage, and the sewage flows into the first water storage layer 13. Biological detention pond 2 is including from top to bottom including water-storage layer 21, overburden 22, composite medium packing layer 23 and gravel layer 24, the initial stage rainwater after 1 processing of biological filtration pond and/or confluence system overflow sewage are introduced in second water-storage layer 21, it keeps water for composite medium packing layer 23 to pass through overburden 22, filter through composite medium packing layer 23 again, denitrogenation and dephosphorization are handled, and, composite medium packing layer 3 has appropriate organic matter content, the suitable plant of better adsorption capacity and water retention and microorganism grow, rethread gravel layer 4 carries out quick discharge with the initial stage rainwater after purifying and/or confluence system overflow sewage. Above-mentioned initial stage rainwater and/or confluence system overflow sewage filter layer upon layer through hierarchical biofiltration system, when guaranteeing that the high efficiency gets rid of the suspended solid, can not only ensure 3 difficult blockings of composite medium packing layer to make 3 more effective performances of composite medium packing layer to the absorption and the filtration of pollutant, and then improve the pollutant and get rid of purifying effect, need not frequent change biological delay composite medium and pack.

The invention relates to a graded biofiltration system, which comprises a biofiltration tank 1 and a bioretention tank 2. In view of the characteristics of the quality and the quantity of the initial rainwater and the combined overflow sewage, the initial rainwater and/or the combined overflow sewage pollution are controlled by combining the biological filter tank 1 and the low-impact biological retention tank 2 so as to deal with the initial rainwater and/or the combined overflow sewage pollution under different bedding surfaces and meteorological conditions, the biological filter tank 1 is used for primary treatment, and the biological retention tank 2 is used for secondary treatment, so that the quality of the effluent can be ensured, and the blockage of the biological retention tank 2 caused by overhigh load can be avoided.

In this embodiment, the thickness of the composite dielectric filler layer 23 is 800mm to 1000 mm.

In this embodiment, the thickness of the volcanic rock layer 12 is 1500mm to 1800 mm.

In this embodiment, the volcanic rock layer 12 is formed of volcanic rock particles having a non-uniform particle size, and the average particle size of the volcanic rock particles is 10mm to 20 mm.

In this embodiment, vegetation can be planted between the upper part of the composite medium filler layer 23 and the covering layer 22. The composite medium filler layer 23 has the functions of water retention and fertilizer retention, so that nutrient substances are not released along with initial rainwater, and the generation conditions of various landscape plants can be met.

Examples

Example 1

A graded biofiltration media comprising: the biological filter filler comprises volcanic rock, the average particle size of the volcanic rock is 15mm, the mud content is less than 0.4%, and the specific surface area is more than 9.5m²The dissolubility of hydrochloric acid is less than 3 percent; the biological retention composite medium filler comprises the following components in percentage by mass: 5% of water supply plant sludge, 54% of coarse sand, 13.5% of fine sand, 22.5% of planting soil, 5% of coconut husk and the initial infiltration rate of the bioretention composite medium filler is more than or equal to 4.2 multiplied by 10^-5m/s, stable infiltration rate not less than 2.2X 10^-5m/s, pH 6.3, organic matter burning weight loss rate (LOI) 3.2%, coarse sand average particle size 0.8mm, fineness modulus 3.5; the average grain diameter of the fine sand is 0.3mm, and the fineness modulus is 2; the permeability of the planting soil is more than 3.5 multiplied by 10^-6m/s, organic matter content > 5%,the pH value is 7.1, and the cation exchange capacity is more than 5mep/100 g; the pH value of the coconut coir is 5.5, and the EC value (conductivity) of the coconut coir is 0.6.

A method of making a graded biofiltration media comprising the steps of:

the biological retention composite medium filler comprises the following steps:

s1: spreading 60% dewatered sludge of water supply plant to form a sludge layer with a thickness of 20cm, drying in the sun, and continuously turning over the sludge layer once a day for 7 days by using a rooter;

s2: feeding the water supply plant sludge dried in the sun in the step S1 into a crusher for crushing, feeding the crushed sludge into a vibrating screen for screening, wherein the size of the screen hole is 4mm, and obtaining water supply plant sludge particles;

s3: soaking the coconut coir without the coconut shell in water, draining the residual water when the volume of the coconut coir is expanded to 3-4 times, flushing the coconut coir while draining, repeatedly cleaning for 3 times to remove salt, and drying in the air;

s4: and (4) stirring and mixing the sludge particles of the water supply plant obtained in the step S2 and the coconut coir obtained in the step S3 with coarse sand, fine sand and planting soil to obtain the biological retention composite medium filler.

The preparation method of the biological filtering filler comprises the following steps: cleaning the volcanic rock, soaking the volcanic rock in water for more than 48 hours, and spreading the volcanic rock on the field to naturally dry the volcanic rock after the concentration of pollutants in the water is not increased according to the basic project indexes of the environmental quality Standard of surface Water (GB 3838).

A staged biofiltration system comprising: a volcanic rock layer 12 formed by the biological filter filler and a composite medium filler layer 23 formed by the biological retention composite medium filler; a biological filter tank 1 for filtering and biologically degrading the initial rainwater and/or combined overflow sewage, and a biological retention tank 2 for filtering, dephosphorizing and denitrating the initial rainwater and/or combined overflow sewage treated by the biological filter tank 1; the biological filtration tank 1 includes: a 300mm gravel water distribution layer 11 for uniformly distributing introduced initial rainwater and/or combined overflow sewage, a 1600mm volcanic rock layer 12 for roughly filtering and solidifying microorganisms to realize biodegradation after the initial rainwater and/or the combined overflow sewage are uniformly distributed on the gravel rock layer, and a 200mm first water storage layer 13 for retaining the initial rainwater and/or the combined overflow sewage after being filtered by the volcanic rock layer 12 to enable the biological filter tank 1 to form a stable anoxic/anaerobic environment are sequentially distributed from bottom to top along the flowing direction of the initial rainwater and/or the combined overflow sewage; the bioretention tank 2 includes: the 300mm second water storage layer 21 for storing the initial rainwater overflowed by the first water storage layer 13 and/or the combined overflow sewage, the 100mm covering layer 22 for retaining water for the composite medium packing layer 23 and preventing the initial rainwater and/or the combined overflow sewage from directly impacting the composite medium packing layer 23, the 800mm composite medium packing layer 23 for filtering, dephosphorizing and denitriding the initial rainwater and/or the combined overflow sewage filtered by the covering layer 22, and the 400mm gravel drainage layer 24 for realizing rapid drainage of the initial rainwater and/or the combined overflow sewage treated by the composite medium packing layer 23 are sequentially arranged from top to bottom along the flowing direction of the initial rainwater and/or the combined overflow sewage.

Example 2

A graded biofiltration media comprising: the biological filter filler comprises volcanic rock, the average particle size of the volcanic rock is 13mm, the mud content is less than 0.4%, and the specific surface area is more than 9.5m²The dissolubility of hydrochloric acid is less than 3 percent; the biological retention composite medium filler comprises the following components in percentage by mass: the biological retention composite medium filler comprises the following components in percentage by mass: 5% of water supply plant sludge, 54% of coarse sand, 13.5% of fine sand, 22.5% of planting soil, 5% of coconut husk and the initial infiltration rate of the bioretention composite medium filler is more than or equal to 4.2 multiplied by 10^-5m/s, stable infiltration rate not less than 2.2X 10^-5m/s, pH 6.3, organic matter burning weight loss rate (LOI) 3.2%, coarse sand average particle size 0.8mm, fineness modulus 3.5; the average grain diameter of the fine sand is 0.3mm, and the fineness modulus is 2; the permeability of the planting soil is more than 3.5 multiplied by 10^-6m/s, organic matter content is more than 5 percent, pH value is 7.1, and cation exchange capacity is more than 5mep/100 g; pH value of coconut husk of 6The EC value (conductivity) was 0.75.

The preparation method of the graded biofiltration medium was the same as in example 1.

The fractionated biofiltration system was the same as in example 1.

Example 3

A graded biofiltration media comprising: the biological filter filler comprises volcanic rock, the average particle size of the volcanic rock is 15mm, the mud content is less than 0.4%, and the specific surface area is more than 9.5m²The dissolubility of hydrochloric acid is less than 3 percent; the biological retention composite medium filler comprises the following components in percentage by mass: the biological retention composite medium filler comprises the following components in percentage by mass: the biological retention composite medium filler comprises the following components in percentage by mass: 5% of water supply plant sludge, 54% of coarse sand, 13.5% of fine sand, 22.5% of planting soil, 5% of coconut husk and the initial infiltration rate of the bioretention composite medium filler is more than or equal to 4.2 multiplied by 10^-5m/s, stable infiltration rate not less than 2.2X 10^-5m/s, pH of 6.3, burning weight loss rate (LOI) of organic matters of 3.2 percent, average grain diameter of coarse sand of 0.8mm and fineness modulus of 3.5; the average grain diameter of the fine sand is 0.3mm, and the fineness modulus is 2; the permeability of the planting soil is more than 3.5 multiplied by 10^-6m/s, organic matter content is more than 5 percent, pH value is 7.1, and cation exchange capacity is more than 5mep/100 g; the pH value of the coconut coir is 6.2, and the EC value (conductivity) of the coconut coir is 0.8.

The fractionated biofiltration system was the same as in example 1.

Comparative example 1

The bioretention composite medium filler comprises 100% planting soil.

A bioretention tank comprising: the 300mm second water storage layer for storing the initial rainwater overflowed by the first water storage layer and/or the combined overflow sewage, the 100mm covering layer for preserving water and preventing the initial rainwater and/or the combined overflow sewage from directly impacting the composite medium packing layer, the 800mm composite medium packing layer for filtering, dephosphorizing and denitriding the initial rainwater and/or the combined overflow sewage after being filtered by the covering layer, and the 400mm gravel drainage layer for quickly draining the initial rainwater and/or the combined overflow sewage after being treated by the composite medium packing layer are sequentially arranged from top to bottom along the flowing direction of the initial rainwater and/or the combined overflow sewage.

Comparative example 2

The bioretention composite medium filler comprises 60% of coarse sand, 15% of fine sand and 25% of planting soil, and the bioretention pond is the same as the comparative example 1.

Comparative example 3

The biological retention composite medium filler comprises 58% of coarse sand, 14% of fine sand, 23% of planting soil and 5% of coconut coir, and the biological retention tank is the same as the comparative example 1.

Comparative example 4

The biological filter filler comprises volcanic rock with average particle diameter of 15mm, mud content of less than 0.4%, and specific surface area of more than 9.5m²The dissolubility of hydrochloric acid is less than 3 percent per gram.

A biofiltration tank comprising: the 300mm gravel water distribution layer for uniformly distributing the introduced initial rainwater and/or combined overflow sewage, the 1600mm volcanic rock layer for roughly filtering and solidifying microorganisms to realize biodegradation after the initial rainwater and/or combined overflow sewage is uniformly distributed on the gravel rock layer, and the 200mm first water storage layer for retaining the initial rainwater and/or combined overflow sewage after being filtered by the volcanic rock layer to enable the biological filter tank to form a stable anoxic/anaerobic environment are sequentially distributed from bottom to top along the flowing direction of the initial rainwater and/or the combined overflow sewage.

Comparative example 5

The biofiltration packing included 100% gravel and the biofiltration tank was the same as in comparative example 4.

Comparative example 6

The biofiltration filler comprises 100 percent of ceramsite, and the biofiltration tank is the same as the biofiltration tank in the comparative example 4.

Comparative example 7

The biofiltration packing comprised 100% zeolite and the biofiltration basin was the same as in comparative example 4.

Introducing CSO (I), CSO (II) and CSO (III) into the bioretention facilities of the above examples 1 to 3, introducing inlet water (I) into the bioretention facilities of the comparative examples 1 to 3, introducing CSO (IV) and CSO (V) into the biological filter tank of the comparative example 4, introducing inlet water (II) into the biological filter tank of the comparative examples 5 to 7, performing water quality detection on water which is not treated by the bioretention facilities or the biological filter tank and water which is treated by the bioretention facilities or the biological filter tank, and determining COD (chemical oxygen demand), SS (suspended solids), NH (NH) of the water quality₃N (ammonia nitrogen), TN (total nitrogen), TP (total phosphorus).

TABLE 1 Water quality of CSO of the examples

TABLE 2 Water quality conditions of comparative examples 1, 2 and 3

TABLE 3 Water quality in comparative example 4

TABLE 4 Water quality conditions of comparative examples 5, 6 and 7

As is clear from tables 1, 2, 3 and 4, COD, SS and NH in the bioretention facilities of examples 1 to 3 of the present invention₃The removal effects of-N, TN and TP are obvious, although the SS removal rate of the comparative example 1 is high, the removal rates of COD and TP are low, the SS removal rate of the comparative example 2 is high, but the removal rates of TN and TP are low, the removal rate of each index of the biological filter tank of the comparative example 4 is low, the filter effect is poor, and the removal rates of each index of the biological filter tanks of the comparative examples 5-7 are also low. Therefore, all indexes of the filtered water quality of the bioretention facility reach the standard, and the bioretention composite medium filler in the bioretention facility has proper organic matter content and good water retention property, and is suitable for the growth of plants and microorganisms.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A graded biological filter medium is characterized in that,

Including: biological filter packing for primary treatment of primary rainwater and/or combined overflow sewage, and secondary treatment of primary rainwater and/or combined overflow wastewater after the primary treatment Bioretention composite media fillers,

the biological filter packing comprises volcanic rock;

The bioretention composite medium filler includes the following mass percentages: 3% to 10% of water supply plant sludge, 50% to 60% of coarse sand, 10% to 15% of fine sand, 20% to 25% of planting soil, and 2% of coconut bran. ~8%.

2. The graded biological filter medium of claim 1, wherein

The initial infiltration rate of the bioretention composite medium filler is ≥4.2× ^10-5 m/s, the stable infiltration rate is ≥2.2× ^10-5 m ^/ s, the pH is 5.5-6.5, and the organic matter loss on ignition (LOI) is 2.5% to 3.5%.

3. The graded biological filter medium of claim 1, wherein

The average particle size of the coarse sand is greater than or equal to 0.5 mm, and the fineness modulus is 3.1 to 3.7;

The average particle size of the fine sand is 0.25mm-0.35mm, and the fineness modulus is 1.6-2.2;

The osmotic capacity of the planting soil is greater than 3.5×10 ^-6 m/s, the organic matter content is greater than 5%, the pH value is 6-8, and the cation exchange capacity is greater than 5mep/100g;

The pH value of the coconut bran is 5.5-6.5, and the EC value (conductivity) of the coconut bran is 0.5-0.9.

4. The graded biological filter medium of claim 1, wherein

The average porosity of the volcanic rock is 0.3-0.4, the mud content is less than 0.4%, the specific surface area is more than 9.5 m ² /g, and the hydrochloric acid solubility is less than 3%.

5. A method for preparing a graded biological filter medium according to any one of claims 1 to 4, characterized in that,

The preparation method of the bioretention composite medium filler comprises the following steps:

S1: Spread out the water supply plant sludge dewatered to 60% and dry it, turn it once a day, and turn it continuously for 5 to 7 days;

S2: pulverize and sieve the water supply plant sludge dried in step S1 to obtain water supply plant sludge particles;

S3: Soak the coconut bran that has been removed from the coconut shell in water, remove the remaining water when the volume expands to 3 to 4 times, and then rinse the coconut bran while draining the water, wash it repeatedly for at least 3 times to remove the salt, and dry it;

S4: stirring and mixing the water supply plant sludge particles obtained in step S2 and the coconut bran obtained in step S3 with coarse sand, fine sand and planting soil to obtain a bioretention composite medium filler;

The preparation method of the biological filtration filler includes the following steps: cleaning the volcanic rock, immersing the volcanic rock in water for more than 48 hours, and taking out the volcanic rock after immersing it to detect that the concentration of pollutants in the water does not increase, and drying it.

6. The method for preparing a graded biological filter medium according to claim 5, characterized in that,

The thickness of the sludge spread in step S1 is 15cm～20cm;

The mesh size of the sieve in step S2 is 3 mm to 5 mm.

7. A graded biological filtration system, characterized in that it comprises: a volcanic rock layer (12) formed by the biological filtration filler according to any one of claims 1 to 4 and a composite media filler layer (23) formed by a bioretention composite media filler );

A biological filter tank (1) for filtration and biodegradation of primary rainwater and/or combined overflow sewage, and for the primary rainwater and/or combined overflow wastewater treated by the biological filter tank (1) Bioretention ponds (2) for filtration, phosphorus and nitrogen removal from flowing sewage;

The biological filtration tank (1) comprises: along the flow direction of the initial rainwater and/or the confluent overflow sewage from bottom to top, gravel for uniform water distribution in the introduced initial rainwater and/or the confluent overflow sewage is arranged in sequence. A water distribution layer (11), a volcanic rock layer (12) used for coarsely filtering and solidifying microorganisms to achieve biodegradation of the initial rainwater and/or confluent overflow sewage after uniform water distribution through the gravel layer, and a volcanic rock layer (12) used for The first aquifer (13) of the first aquifer (13) in which the primary rainwater and/or the confluent overflow sewage filtered by the volcanic rock layer (12) is retained so that the biological filter pool (1) forms a stable anoxic/anaerobic environment;

The bioretention pond (2) comprises: along the flow direction of the initial rainwater and/or the confluent overflow sewage, sequentially arranged from top to bottom for accumulating the initial rainwater and/or overflowing from the first aquifer (13). or the second aquifer (21) of the confluent overflow sewage, used to retain water for the composite medium packing layer (23) and prevent the initial rainwater and/or the confluent overflow sewage from directly impacting the composite medium packing layer (23) covering layer (22), a composite medium packing layer (23) used for filtering, phosphorus and nitrogen removal of the initial rainwater and/or confluent overflow sewage after passing through the covering layer (22), A gravel drainage layer (24) for realizing rapid drainage of the initial rainwater and/or the confluent overflow sewage treated by the composite medium packing layer (23).

8. The hierarchical biofiltration system of claim 7, wherein

The thickness of the composite medium filler layer (23) is 800mm˜1000mm.

9. The graded biofiltration system of claim 7, wherein

The thickness of the volcanic rock layer (12) is 1500mm˜1800mm.

10. The hierarchical biofiltration system of claim 7, wherein:

The volcanic rock layer (12) adopts volcanic rock particles of non-single particle size, and the average particle size of the volcanic rock particles is 10 mm˜20 mm.