Rapid start biofilm suspension media and methods of making same

Abstract

The present application belongs to the field of sewage treatment technology, and relates to a functional material for sewage denitrification, in particular to a suspended filler for rapid start of biofilm enrichment and growth and a preparation method thereof. The present application is to melt and blend a PVA matrix material with biological affinity and a functional biochar with catalytic metabolism in an inorganic salt solution, to complete the foaming forming of the melt mixed solution under the action of a foaming agent by using the foamability of the PVA matrix material, to strictly control the thickness of the foaming layer by a mold to realize the control of the thickness of the biofilm growth, and to significantly improve the stability of the filler. The present application has the characteristics of simple preparation process, controllable process and high product yield, provides technical support for the popularization and application of biofilm, and also provides a new idea for the development and application of the microbial enrichment and culture type suspended filler.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sewage treatment, and relates to a functional material for sewage denitrification, in particular to a suspended filler for rapid start-up of biofilm enrichment and growth and a preparation method thereof. BACKGROUND

[0002] As a kind of sewage biological treatment technology parallel to the activated sludge method, the biofilm method is essentially a microbial immobilization technology. Microorganisms attach and grow on the surface of carrier fillers to form a biofilm. Pollutants in sewage flow through the biofilm, and through oxygen and / or mass transfer, the sewage is purified. Compared with the activated sludge method, the biofilm method has the characteristics of microbial immobilization and enrichment, which realizes the separation of microorganisms and water in the sewage treatment process. The microorganisms immobilized on the carrier fillers have the characteristics of high abundance and large biomass, and have the advantages of high treatment load, strong impact resistance, low sludge yield, and convenient management in the sewage treatment process. Suitable carrier filler design can realize simultaneous nitrification and denitrification, anaerobic ammonia oxidation, short-cut digestion denitrification, and other processes.

[0003] The moving bed biofilm reactor (MBBR) is an important process form of the biofilm method, and the suspended filler is the core of the reactor. The known MBBR suspended fillers are all prepared by extrusion, injection molding or foaming of high molecular polymer particles, and the suspended fillers prepared by using high-density polyethylene (HDPE), polypropylene (PP) and polystyrene (PS) high molecular polymers as raw materials are most widely used. These materials are relatively durable, but have the defects of poor hydrophilicity and biological affinity, which greatly restricts the adhesion performance of initial microorganisms in the start-up stage of the MBBR reactor, resulting in problems such as long biofilm formation time and slow reactor start-up during the use and promotion of the suspended filler. These factors limit the application of the biofilm method as a sewage treatment technology with significant advantages in the municipal and industrial fields.

[0004] Polyvinyl alcohol (PVA) is a high-molecular polymer with excellent hydrophilicity and biocompatibility, and is commonly used as a denitrification carrier scaffold in the water treatment field. Patent 202110787239.8 discloses a denitrification carrier packing material prepared by embedding corn cob-polycaprolactone powder within a polyvinyl alcohol-sodium alginate scaffold material. The crosslinking of polyvinyl alcohol and sodium alginate improves the strength and stability of the denitrification carrier, while also enhancing the material's affinity for microorganisms and improving the carrier's nitrogen removal efficiency. Patent 201410133395.2 discloses a method for preparing a slow-release carbon source filter media based on starch-polyvinyl alcohol. The prepared filter media meets certain mechanical strength and slow-release rate requirements, partially solving the carbon source addition problem for biological denitrification of low C / N wastewater, and providing a relatively stable carbon source and a suitable growth and metabolic environment for microbial denitrification.

[0005] The invention CN200710026215.0, entitled "A Nutrient-Release Biological Packing Material for Water Treatment and Its Preparation Method", discloses that the biological packing material formulation includes a polymer base material (polypropylene, polyethylene or polyester), while polyvinyl alcohol is used only as a very small amount of substance for controlling the slow release effect.

[0006] The invention CN202110221456.0, entitled "A Bioactive Filler for Embedding Microorganisms in Biological Wax and Its Preparation Method and Application," discloses that the filler is one or more of polyurethane, aldehyde fiber, polypropylene, polyethylene, polyester, polyester fiber, and PVC honeycomb inclined tube. Polyvinyl alcohol is used only as a very small amount of modifier.

[0007] The invention CN202210509565.7, "Biofilm Purification Device and Method for In-situ Treatment of Lake and Reservoir Water," discloses that: loofah biofilm uses polyvinyl alcohol-sodium alginate co-immobilization technology to immobilize microorganisms on the surface and internal pores of loofah; that is, polyvinyl alcohol acts as a support.

[0008] Currently, PVA-embedded inorganic salts, carbon sources, and biochar have not been applied in the preparation and development of biocompatible suspension fillers. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a suspended packing material for rapid biofilm formation and its preparation method; the present invention can accelerate the biofilm development process of the suspended packing material in the initial stage of addition, thereby shortening the reactor start-up time.

[0010] To address the aforementioned technical problems, this invention provides a method for preparing a rapidly initiating biofilm-forming suspended packing material, comprising the following steps:

[0011] 1) PVA is selected as the matrix material (the matrix material is in powder or granular form);

[0012] Mixing the biochar powder and soluble starch uniformly according to a mass ratio of 10-20:0-10, to obtain a mixture;

[0013] 2) Dissolve magnesium sulfate, ferric chloride, ferrous chloride, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and calcium chloride in water to prepare an inorganic salt solution;

[0014] In the inorganic salt solution, the mass concentrations of magnesium sulfate, ferric chloride, ferrous chloride, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and calcium chloride are 0.2-1.5%, 0.05-0.5%, 0.05-0.5%, 0.1-1.0%, 0.1-1.0%, and 0.1-0.5%, respectively;

[0015] 3) Pour the mixture into the inorganic salt solution and perform magnetic stirring at room temperature to obtain a mixed solution one;

[0016] 4) Pour the PVA matrix material into the inorganic salt solution in a container to obtain a mixed solution two; under the condition of magnetic stirring, increase the temperature of the mixed solution two from room temperature to a set oil bath temperature to obtain a heated mixed solution two;

[0017] 5) Continue to perform magnetic stirring, and slowly pour the mixed solution one into the heated mixed solution two according to a set volume ratio; when the obtained mixed solution is heated to a set oil bath temperature value, seal the container opening with a breathable sealing film, and perform magnetic stirring at the set oil bath temperature for 1-5 hours to obtain a mixed solution three;

[0018] That is, the magnetic stirring state is maintained throughout step 5);

[0019] 6) Add a foaming agent to the mixed solution three obtained in step 5) and perform magnetic stirring at room temperature until bubbles (small bubbles) appear; obtain a preliminarily foamed mixed solution; the mass ratio of the foaming agent to the mixed solution three is 1-5%;

[0020] Note: The sodium bicarbonate can be added to the mixed solution three while it is hot, or the mixed solution three can be cooled to room temperature and then the sodium bicarbonate is added;

[0021] 7) Pour the preliminarily foamed mixed solution into a mold, and place it in a blowing drying oven for foaming and drying;

[0022] 8) After cooling to room temperature, take out the foamed product in the mold to obtain a suspended filler with the ability to quickly start biofilm formation.

[0023] Improvements on the preparation method of the suspended filler with the ability to quickly start biofilm formation of the present application:

[0024] In step 3), the mass fraction of the mixture in the mixed solution one is 5-20%;

[0025] The magnetic stirring speed is 80-150 r / min, and the stirring time is 10-30 minutes.

[0026] As a further improvement of the preparation method of the suspended filler for quick start of biofilm formation of the present application:

[0027] In step 4), the mass fraction of the PVA matrix material in the mixed solution II is 5-20%; the set oil bath temperature is 70-120 DEG C, and the magnetic stirring speed is 80-150 r / min.

[0028] As a further improvement of the preparation method of the suspended filler for quick start of biofilm formation of the present application:

[0029] In step 1), the PVA matrix material is at least any one (i.e., one or more) of 1792, 1799, 2099, 2299 and 2699.

[0030] As a further improvement of the preparation method of the suspended filler for quick start of biofilm formation of the present application:

[0031] In step 5), the volume ratio of the mixed solution I to the mixed solution II is 2:1-1:3.

[0032] In step 6), the foaming agent is at least any one (i.e., one or more) of sodium bicarbonate and n-pentane, the magnetic stirring speed is 100-200 r / min, and the stirring time is 5-30 minutes.

[0033] As a further improvement of the preparation method of the suspended filler for quick start of biofilm formation of the present application:

[0034] In step 7), the depth of the mold is 0.01-5 mm.

[0035] Foaming and drying are carried out in a blast drying oven at 50-140 DEG C for 10-60 minutes.

[0036] As a further improvement of the preparation method of the suspended filler for quick start of biofilm formation of the present application:

[0037] The overall shape of the suspended filler is not limited.

[0038] The present application also simultaneously provides the suspended filler for quick start of biofilm formation prepared by any one of the above methods.

[0039] In view of the problem that the commercially available MBBR suspended filler has poor hydrophilicity and biological affinity, resulting in a too long biofilm formation period, the present application provides a suspended filler for quick start of biofilm formation and a preparation method thereof.

[0040] Culture medium has been applied in the in vitro directed culture process of microorganisms to obtain and study the characteristics of target microorganisms. The principle of culture medium is to provide specific carbon source and / or nitrogen source according to the needs of target microorganisms, and to supplement a series of inorganic salts for rapid enrichment and directed growth of microorganisms. At present, the principle has not been applied in the in-situ running system. According to the water-soluble characteristics of polyvinyl alcohol at a specific temperature and the stability characteristics of the high polymer material after drying, the inorganic salts and carbon sources and other substances promoting the growth of microorganisms are embedded in the polyvinyl alcohol to prepare a suspended filler with high biological affinity. At the same time, in order to accelerate the adhesion speed of microorganisms to the suspended filler in the early stage of use, biochar with positive charge characteristics is embedded to further accelerate the biological affinity of the prepared suspended filler. The biochar used in the present application is prepared according to the patent CN202011069720.5. At present, PVA embedding inorganic salts, carbon sources and biochar has not been applied in the preparation and development of suspended fillers with biological affinity.

[0041] Compared with the prior art, the present application has the following beneficial effects:

[0042] 1. In order to realize the rapid start-up of the suspended filler, the present application selects PVA high molecular polymer with biological affinity as the base material, and further modifies the biological affinity of the base material to meet the selection and enrichment of functional bacteria.

[0043] By studying the culture and domestication characteristics of nitrifying / denitrifying bacteria, functional biochar and inorganic salts required for nitrifying / denitrifying bacteria metabolism are added to the PVA matrix. On the one hand, biochar can increase the surface roughness and provide the basis for metabolic catalysis. On the other hand, the prepared filler has a contact surface with the properties of culture medium suitable for the growth of nitrifying / denitrifying bacteria. Nitrifying / denitrifying bacteria use pollutants in wastewater as nutrient sources, and use the carbon source slow-release characteristics of inorganic salts and part of starch on the surface of the filler to meet the metabolic needs of the bacterial community, greatly accelerating the enrichment and growth rate of the digestion / denitrifying bacteria on the surface of the filler. This has not been achieved in the current market and research field of suspended fillers.

[0044] 2. The filler prepared by foaming the PVA matrix meets the use characteristics of the suspended filler. At the same time, the thickness of the foaming layer is strictly controlled by the mold to effectively control the thickness of the biofilm growth, which avoids the risk of anaerobic or dead zones formed inside the foaming structure. In addition, the foaming structure produces a large contactable specific surface area for microbial attachment and growth, which greatly increases the biomass of the biochemical reaction system, and has significant benefits in improving system processing load and reducing sludge production. That is, the specific properties of PVA make it possible to embed "nutrient sources" in the suspended filler.

[0045] 3、The inorganic salt is applied to the development of the suspended filler for the first time, so that the biological affinity of the suspended filler is increased, and the microbial biofilm formation speed in the start-up period of the MBBR is accelerated; and a basis for accelerating the biofilm formation of the suspended filler is provided.

[0046] 4、The positive charge characteristics of the embedded biochar accelerate the attraction of the suspended filler to the microorganisms, so that the biological affinity characteristics of the suspended filler are further improved.

[0047] 5、The suspended filler prepared by the method has the characteristics of simple preparation process, controllable process and high product yield, which lays an industrialization foundation for the present application, and also provides a new idea for the development and application of the microbial enrichment culture type suspended filler.

[0048] In summary, the present application provides a suspended filler for rapid start-up of biofilm formation and a preparation method thereof, a high-biological-affinity suspended filler is prepared by using the water solubility, foamability and biological affinity of the PVA high-molecular polymer. The prepared suspended filler is applied to the MBBR system, so that the biofilm formation can be rapidly started, and the start-up time of the reactor is greatly shortened.

[0049] In summary, the present application is to melt and blend the PVA matrix material with biological affinity characteristics and the functional biochar with catalytic metabolism in the inorganic salt solution, to complete the foaming molding of the melt mixed solution under the action of the foaming agent by using the foamability of the PVA matrix material, to strictly control the thickness of the foaming layer through the mold to realize the control of the growth thickness of the biofilm, and to significantly improve the stability of the filler. The biochar in the prepared suspended filler has the functions of increasing the surface roughness and providing the basis for metabolic catalysis, and the inorganic salt system lays the foundation for the contact surface of the filler to be suitable for the growth and metabolism of nitrifying / denitrifying bacteria. The nitrifying / denitrifying bacteria use the pollutants in the wastewater as a nutrient source, use the inorganic salt and part of the starch on the surface of the filler to meet the metabolic demand of the bacterial population, accelerate the enrichment and growth speed of the digestion / denitrifying bacteria on the surface of the filler, shorten the biofilm formation time by nearly 10 times, and greatly improve the start-up speed of the reactor. The present application has the characteristics of simple preparation process, controllable process and high product yield, provides technical support for the popularization and application of the biofilm, and also provides a new idea for the development and application of the microbial enrichment culture type suspended filler. BRIEF DESCRIPTION OF DRAWINGS

[0050] The specific embodiments of the present application will be further described in detail below with reference to the accompanying drawings.

[0051] Figure 1 A suspended filler schematic diagram of the embodiment 1 of the present application is shown.

[0052] Figure 2 A suspended filler schematic diagram of the embodiment 2 of the present application is shown.

[0053] Figure 3 A schematic diagram of the suspended filler of embodiment 3 of the present application is shown. DETAILED DESCRIPTION

[0054] The present application is further described below in conjunction with specific embodiments, but the scope of protection of the present application is not limited thereto: the present application aims to provide a suspended filler capable of quickly starting biofilm formation and a preparation method thereof, by using municipal sewage treatment plant activated sludge in the aerobic tank for inoculation, fluidization and biofilm formation test, the biofilm formation amount of the MBBR suspended filler is 3-5 times that of the commercial rigid suspended filler, has excellent hydraulic characteristics and biological affinity characteristics, the density is 0.98-1.01 g / cm3, and the biofilm can be formed in 1-2 days and start to gradually stabilize and function.

[0055] In the present application: the biochar is the iron-modified carbon microsphere / carbon nanosheet composite porous carbon prepared according to CN202011069720.5 “Preparation method of iron-modified carbon microsphere / carbon nanosheet composite porous carbon based on moso bamboo hydrothermal carbonization and application thereof”, for example, can be obtained in Example 1 thereof.

[0056] The air-permeable sealing film may, for example, be selected from BKMAM.

[0057] Embodiment 1: a suspended filler capable of quickly starting biofilm formation and a preparation method thereof, the specific steps are as follows:

[0058] 1) Select PVA powder with grades 1799 and 2099, mix them uniformly according to a mass ratio of 4:1 to obtain a PVA matrix material;

[0059] Mix the biochar and soluble starch according to a mass ratio of 10:1 to obtain a mixture.

[0060] 2) Dissolve magnesium sulfate, ferric chloride, ferrous chloride, potassium dihydrogen phosphate, dipotassium hydrogen phosphate and calcium chloride in water to configure an inorganic salt solution;

[0061] In the inorganic salt solution, the mass fractions of magnesium sulfate, ferric chloride, ferrous chloride, potassium dihydrogen phosphate, dipotassium hydrogen phosphate and calcium chloride are 0.5%, 0.1%, 0.1%, 0.5%, 0.5% and 0.2%, respectively.

[0062] 3) Add the mixture to the inorganic salt solution and stir on a magnetic stirrer for 15 minutes at a speed of 100 r / min, and after stirring, obtain a mixture liquid one; the mass fraction of the mixture in the mixture liquid one is 5%.

[0063] 4) In a container, add the PVA matrix material to the inorganic salt solution to obtain a mixture liquid two; the mass fraction of the PVA matrix material in the mixture liquid two is 5%.

[0064] Put the mixed liquid two into the oil bath magnetic stirrer, start stirring at room temperature, set the oil bath temperature to 90℃, and the magnetic stirring speed to 120r / min. When the temperature rises from room temperature to the set oil bath temperature, the mixed liquid two after heating is obtained (i.e. the temperature of the mixed liquid two after heating is 90℃, the set oil bath temperature).

[0065] 5) Continue to stir under magnetic stirring conditions, pour the mixed liquid one into the mixed liquid two after heating at a volume ratio of 1:1. When the obtained mixed liquid is heated to the set oil bath temperature value (90℃), seal the container opening with a breathable sealing film, and stir magnetically at the set oil bath temperature (90℃) for 2.5 hours to obtain mixed liquid three;

[0066] Note: The whole process of step 5) is kept under magnetic stirring.

[0067] 6) Take the mixed liquid three out of the container, add 1% sodium bicarbonate based on the mass fraction of the mixed liquid three, and stir magnetically at room temperature at 100r / min for 15 minutes. At this time, the mixed liquid three appears small bubbles; obtain the mixed liquid after preliminary foaming.

[0068] Note: The sodium bicarbonate can be added while the mixed liquid three is hot, or the mixed liquid three can be cooled to room temperature before adding the sodium bicarbonate.

[0069] 7) Pour the preliminary foaming mixed liquid into a mold with a depth of 1mm, and put it into a forced air drying oven (air volume about 30m 3 / h) to foam at 100℃ for 30 minutes.

[0070] 8) Take the mold out of the forced air drying oven and cool it to room temperature, then take out the foaming product obtained in the mold, to obtain a suspended filler with the ability to quickly start biofilm formation.

[0071] Figure 1 The suspended filler obtained under the preparation conditions of this embodiment 1 has an apparent density of 0.99g / cm3, a filler porosity of more than 85%, and a swelling rate of about 15% after being immersed and swollen in the MBBR reactor (as described in Experiment 1 below) to form a disc shape. After 3-5 minutes, complete aeration fluidization can be achieved in the wastewater. The surface interface observation results show that the internal support structure of the suspended filler is a wall-like rib plate, which greatly increases the attachable surface of microorganisms. The biomass measurement results show that after one week of fluidization biofilm formation, the biofilm formation amount of the filler under this embodiment is 15kg / m3. Compared with the traditional filler K5 (Veolia, France), the biofilm formation amount is nearly 30 times that of the traditional filler. After a long period of fluidization biofilm formation (more than one month), the biofilm formation of the filler of this embodiment and the traditional filler both tend to be stable, and the biofilm formation amount of this embodiment is 25kg / m3, which is nearly 10 times that of the traditional filler.

[0072] Example 2: A rapid-start biofilm-forming suspension packing material and its preparation method, the specific steps of which are as follows:

[0073] 1) Select powdered PVA matrix materials of grades 1792 and 2099, mix them evenly at a mass ratio of 10:1 to obtain PVA matrix materials;

[0074] Biochar and soluble starch were mixed evenly at a mass ratio of 20:1 to obtain a mixture.

[0075] 2) Dissolve magnesium sulfate, ferric chloride, ferrous chloride, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and calcium chloride in water to prepare an inorganic salt solution;

[0076] In the inorganic salt solution, the mass concentrations of magnesium sulfate, ferric chloride, ferrous chloride, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and calcium chloride are 1.0%, 0.2%, 0.2%, 0.2%, 0.2%, and 0.3%, respectively.

[0077] 3) Add the mixture to the inorganic salt solution and stir on a magnetic stirrer for 20 minutes at a speed of 100 r / min. After stirring, the first mixture is obtained; the mass fraction of the mixture in the first mixture is 10%.

[0078] 4) In a container, add the PVA matrix material to the inorganic salt solution to obtain mixture two; the mass fraction of the PVA matrix material in mixture two is 10%.

[0079] Place the second mixture into an oil bath magnetic stirrer and start stirring at room temperature. Set the oil bath temperature to 100℃ and the magnetic stirring speed to 140r / min. When the temperature rises from room temperature to the set oil bath temperature, the second mixture after heating is obtained (that is, the temperature of the second mixture after heating is the set oil bath temperature of 100℃).

[0080] 5) Continue stirring with magnetic force, pour mixture one into mixture two after heating at a volume ratio of 2:1. When the resulting mixture is heated to the set oil bath temperature (100℃), seal the container opening with a breathable sealing film and stir magnetically for 2.0 hours at the set oil bath temperature (100℃) to obtain mixture three.

[0081] Note: Maintain magnetic stirring throughout step 5).

[0082] 6) Remove the mixture from the container, add 0.5% sodium bicarbonate and 1% n-pentane (by mass fraction of the mixture), and stir magnetically at 100 r / min for 20 minutes at room temperature. At this time, tiny bubbles will appear in the mixture; the mixture after preliminary foaming is obtained.

[0083] 7) The preliminary foaming mixture is poured into a mold with a depth of 1.1 mm, and placed in a forced air drying oven to foam at 120°C for 15 minutes.

[0084] 8) After the mold is removed from the oven and cooled to room temperature, the foam obtained after foaming is removed from the mold to obtain a suspended filler with the ability to quickly start biofilm formation.

[0085] Figure 2 For the suspended filler obtained under the preparation conditions of this embodiment 2, the apparent density of the suspended filler is 1.01 g / cm3, the filler porosity is more than 95%, after being soaked and swollen, the suspended filler is stably formed into a disc shape, the swelling rate is about 10%, and complete aeration fluidization in sewage can be achieved after 2-3 minutes. The results of surface interface observation show that the internal support structure of the suspended filler is also a wall-shaped rib plate, which greatly increases the attachable surface of microorganisms. The results of biomass determination show that after one week of fluidization and biofilm formation, the biofilm formation amount of the filler under this embodiment is 13 kg / m3. Compared with the traditional filler, the biofilm formation amount is nearly 25 times that of the traditional filler. After a long period of fluidization and biofilm formation (more than one month), the biofilm formation of the filler and the traditional filler tends to be stable. At this time, the biofilm formation amount of this embodiment is 23 kg / m3, which is nearly 9 times that of the traditional filler.

[0086] Embodiment 3, a suspended filler for quickly starting biofilm formation and a preparation method thereof, the specific steps are as follows:

[0087] 1) Select a PVA base material with a grade of 1799 in granular form;

[0088] Mix the biochar and soluble starch in a mass ratio of 15:1 to obtain a mixture.

[0089] 2) Dissolve magnesium sulfate, ferric chloride, ferrous chloride, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and calcium chloride in water to prepare an inorganic salt solution.

[0090] In the inorganic salt solution, the mass fractions of magnesium sulfate, ferric chloride, ferrous chloride, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and calcium chloride are 1.5%, 0.3%, 0.3%, 0.8%, 0.8%, and 0.5%, respectively.

[0091] 3) Add the mixture to the inorganic salt solution and stir on a magnetic stirrer for 15 minutes at a speed of 100 r / min. After stirring, a mixture solution one is obtained. The mass fraction of the mixture in the mixture solution one is 15%.

[0092] 4) In a container, add the PVA base material to the inorganic salt solution to obtain a mixture solution two. The mass fraction of the PVA base material in the mixture solution two is 15%.

[0093] Put the mixed liquid two into the oil bath magnetic stirrer, start stirring at room temperature, set the oil bath temperature to 95℃, and the magnetic stirring speed to 150r / min. When the temperature rises from room temperature to the set oil bath temperature, the obtained mixed liquid two after heating (i.e. the temperature of the mixed liquid two after heating is the set oil bath temperature 95℃) is obtained.

[0094] 5), continue to pour the mixed liquid one into the mixed liquid two after heating under the condition of magnetic stirring, according to the volume ratio of 1:2, when the obtained mixed liquid is heated to the set oil bath temperature value (95℃), seal the container opening with a breathable sealing film, and magnetically stir for 4.0 hours at the set oil bath temperature (95℃), to obtain mixed liquid three;

[0095] Note: The whole process of step 5) is kept under magnetic stirring.

[0096] 6), take out the mixed liquid three from the container, add 1% sodium bicarbonate based on the mass fraction of the mixed liquid three, and magnetically stir at room temperature at 150r / min for 20 minutes, at which time the mixed liquid three appears small bubbles; obtain the mixed liquid after preliminary foaming.

[0097] 7), pour the preliminary foaming mixed liquid into a mold with a depth of 0.9mm, and put it into a forced air drying oven at 105℃ for foaming for 30 minutes.

[0098] 8), take out the mold from the oven and cool it to room temperature, then take out the obtained foam from the mold, to obtain a suspended filler with the ability to quickly start biofilm formation.

[0099] Figure 3 The suspended filler obtained under the preparation conditions of this embodiment 3 has an apparent density of 1.01g / cm3, a filler porosity of more than 95%, and a swelling rate of about 8% after being added to the MBBR reactor and being soaked and swollen to form a disc shape. It can be completely aerated and fluidized in sewage within 1 minute. The surface interface observation result shows that the internal support structure of the suspended filler is also a wall-shaped rib plate, which greatly increases the attachable surface of microorganisms. The biomass measurement result shows that after one week of fluidized biofilm formation, the biofilm formation amount of the filler under this embodiment is 12kg / m3, which is nearly 24 times that of the traditional filler. After a long period of fluidized biofilm formation (more than one month), the biofilm formation of the filler under this embodiment and the traditional filler tends to be stable, and the biofilm formation amount of this embodiment is 26kg / m3, which is nearly 10 times that of the traditional filler.

[0100] Experiment 1: In order to further illustrate the performance of the prepared suspended filler, the suspended fillers prepared under the conditions of Examples 1, 2 and 3 and the traditional filler K5 were subjected to MBBR continuous water feeding test. The MBBR reactor unit was a laboratory scale with a total working volume of 14.4 L, and the length, width and height were 600 mm, 120 mm and 200 mm, respectively. The sewage used in the test was taken from the total sewage outlet of Shangkun Ecological Creative Park, No. 10 Xiyuan Road, Xihu District, Hangzhou, Zhejiang Province, China. The physicochemical indexes thereof were as follows: chemical oxygen demand 410-710 mg / L, ammonia nitrogen 80-150 mg / L, total nitrogen 100-180 mg / L and total phosphorus 7-15 mg / L. By adjusting the pool to adjust the chemical oxygen demand to 200-250 mg / L, the ammonia nitrogen to 40-50 mg / L, the total nitrogen to 50-60 mg / L and the total phosphorus to 3-5 mg / L, the test was run. The activated sludge was inoculated from the Chengxi Sewage Treatment Plant in Hangzhou, China, and the sludge concentration was adjusted to 2 g / L. The sludge inoculation was only carried out on the first day (24 h) with an inoculation concentration of 1 g / L, and the first day (24 h) was carried out by smothering. The continuous flow feeding mode was adopted afterwards, the hydraulic retention time was controlled at 8 h, and the internal and external reflux ratios were controlled at 150% and 100%, respectively. The results are shown in Table 1.

[0101] Table 1

[0102] Biomass (kg / m3) Start-up time (days) COD removal rate (%) Total nitrogen removal rate (%) Example 1 7.5 2 87.5 90.2 Example 2 6.2 1 82.9 89.1 Example 3 6.0 1 82.1 88.5 Conventional K5 packing 1.1 12 74.2 68.6

[0103] As shown in Table 1, compared with the traditional filler K5, the biofilm formation time of the suspended filler of the application was greatly shortened under the condition of completing more than 80% removal rate of COD and ammonia nitrogen. After two days of biofilm formation, the COD removal rate of Examples 1-3 was stably above 82%, while the COD removal rate of K5 was only 74.2% after 12 days of biofilm formation. After two days of biofilm formation, the total nitrogen removal rate of Examples 1-3 was stably above 88%, while the total nitrogen removal rate of the control group was 68.6% after 12 days of biofilm formation. Therefore, the suspended filler of the application has a significant effect on the enrichment and growth of the biofilm in the initial stage of use, and the biofilm formation time is shortened by nearly 10 times, which greatly accelerates the start-up of the reactor under the condition of effective pollutant removal.

[0104] In addition, the thickness of the suspended filler of the application can be strictly controlled according to the depth of the mold, which is different from the commercially available sponge filler. Under the condition that the thickness of the suspended filler of the application is controlled, the thickness of the biofilm is also strictly controlled. In the MBBR reactor, the suspended filler is fluidized, collided, sheared and extruded in the reactor under the action of aeration, which promotes the biofilm growing inside the suspended filler to be in a dynamic updating state, and the activity of the biofilm is maintained in the long-term operation process.

[0105] Comparative Example 1-1, cancel the use of inorganic salt, that is, the inorganic salt solution in Example 2 is changed to water, specifically: the mixture is poured into water and stirred magnetically at room temperature to obtain a mixed solution one; the PVA matrix material is poured into water to obtain a mixed solution two; the rest is the same as Example 2.

[0106] Comparative Example 1-2, cancel the use of biochar, that is, directly replace the mixture with soluble starch; the rest is the same as Example 2.

[0107] Comparative Example 1-3, cancel the use of inorganic salt and soluble starch at the same time, that is, directly replace the mixture with biochar in Example 2, and change the inorganic salt solution to water; the rest is the same as Example 2.

[0108] The above comparative examples are tested synchronously with the above Experimental Example 1 method, and the comparison with the experimental results corresponding to Example 2 is as follows:

[0109] Table 2

[0110] Biomass (kg / m3) Start-up time (days) COD removal rate (%) Total nitrogen removal rate (%) Comparative Example 1-1 4.5 5 72.2 68.2 Comparative Example 1-2 3.2 5 62.1 69.1 Comparative Example 1-3 2.8 12 75.6 70.7 Example 2 6.2 1 82.9 89.1

[0111] As shown in Table 2, the addition of inorganic salt and biochar has a significant effect on the start-up of the MBBR reactor. Comparative Example 1-1 shows that the biomass after 5 days of biofilm formation is only 73% of that in Example 2 after 1 day of biofilm formation, and the COD and total nitrogen removal rates are only 87% and 77% of those in Example 2, respectively, indicating that inorganic salt has a significant effect on the enrichment and cultivation of microorganisms. Comparative Example 1-2 shows that the biomass after 5 days of biofilm formation is only 52% of that in Example 2 after 1 day of biofilm formation, and the COD and total nitrogen removal rates are only 75% and 78% of those in Example 2, respectively, indicating that biochar also has a significant effect on the enrichment of microorganisms in the early stage of filler start-up. Comparative Example 1-3 shows that the biomass after 12 days of biofilm formation is only 45% of that in Example 2 after 1 day of biofilm formation, and the COD and total nitrogen removal rates are only 91% and 79% of those in Example 2, respectively, indicating that inorganic salt and soluble starch together form a suspension filler with culture medium properties, which has a synergistic effect on the enrichment of microorganisms in the early stage of filler start-up, and the effect is significant.

[0112] Finally, it should be noted that the main features of the present application have been described in detail in the above examples, but are not limited to the specific forms described above. The scope of the present application is defined by the claims, and other embodiments may also be within the scope of the claims in addition to the specific embodiments described above. Improvements and innovations made on the basis of the present application should be included in the protection scope defined by the claims of the present application.

Claims

1. A method for preparing a rapidly initiating biofilm-forming suspended packing material, characterized in that, Includes the following steps: 1) PVA was selected as the matrix material; Biochar powder and soluble starch are mixed evenly at a mass ratio of 10~20:1~10 to obtain a mixture. The PVA matrix material grade is at least one of 1792, 1799, 2099, 2299, and 2699; 2) Dissolve magnesium sulfate, ferric chloride, ferrous chloride, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and calcium chloride in water to prepare an inorganic salt solution; In the inorganic salt solution, the mass concentrations of magnesium sulfate, ferric chloride, ferrous chloride, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and calcium chloride are 0.2-1.5%, 0.05-0.5%, 0.05-0.5%, 0.1-1.0%, 0.1-1.0%, and 0.1-0.5%, respectively. 3) Pour the mixture into an inorganic salt solution and stir magnetically at room temperature to obtain mixture one; 4) Pour the PVA matrix material into the inorganic salt solution in a container to obtain mixture two; under magnetic stirring, heat mixture two from room temperature to the set oil bath temperature to obtain heated mixture two. The mass fraction of PVA matrix material in mixture two is 5~20%; the set oil bath temperature is 70~120℃, and the magnetic stirring speed is 80~150r / min; 5) Continue stirring with magnetic force, and pour mixture one into mixture two after heating according to the set volume ratio. When the resulting mixture is heated to the set oil bath temperature, seal the container opening with a breathable sealing film and stir magnetically for 1 to 5 hours at the set oil bath temperature to obtain mixture three. The volume ratio of the first mixture to the second mixture is 2:1 to 1:3; 6) Add foaming agent to the mixture obtained in step 5), and stir magnetically at room temperature until bubbles appear; to obtain a pre-foamed mixture; the mass ratio of the foaming agent to the mixture is 1~5%; 7) Pour the pre-foamed mixture into a mold, place it in a forced-air drying oven to foam and dry; 8) After cooling to room temperature, remove the foamed material from the mold to obtain a suspension filler that can quickly start film formation.

2. The method for preparing the rapid-start biofilm-forming suspended packing material according to claim 1, characterized in that: In step 3), the mass fraction of the mixture in the first mixture is 5-20%; The magnetic stirring speed is 80~150 r / min, and the stirring time is 10~30 minutes.

3. The method for preparing a rapid-start biofilm-forming suspended packing material according to claim 2, characterized in that: In step 6), the foaming agent is at least one of sodium bicarbonate and n-pentane, the magnetic stirring speed is 100~200 r / min, and the stirring time is 5~30 minutes.

4. The method for preparing a rapid-start biofilm-forming suspended packing material according to claim 3, characterized in that, In step 7), the depth of the mold is 0.01~5mm; Place in a forced-air drying oven at 50~140℃ for foaming and drying for 10~60 minutes.

5. A method for preparing a rapid-start biofilm-forming suspended packing material according to any one of claims 1 to 4, characterized in that: The overall shape of the suspended packing is not limited.

Images