Light suspended filter material for sulfur autotrophic denitrification nitrogen removal as well as preparation method and application of light suspended filter material

Abstract

The invention discloses a sulfur autotrophic denitrification nitrogen removal light suspension filter material and a preparation method and application thereof. The filter material is prepared from the following raw materials in parts by weight: 10-90 parts of polystyrene, 5-30 parts of elemental sulfur, 0.5-50 parts of an alkalinity supplement, 5-10 parts of a foaming agent and 0.5-20 parts of an auxiliary agent. The elemental sulfur is 100-300-mesh sulfur powder or particles with the purity of 90% or above; the diameter of the filter material is 2-15mm, the density is 55-900kg / m, the porosity is greater than 45%, and the specific surface area is greater than 1000m < 2 > / m < 3 >. According to the application, the composite material is used as a filter material to be applied to a denitrification light-weight filter tank; or is applied to a filter dam. The filter material disclosed by the invention has the characteristics of large specific surface area, high biological loading capacity, good biocompatibility, high mechanical property strength, high denitrification efficiency and stable effluent.

Description

Technical Field

[0001] The present invention belongs to the field of sewage treatment, and particularly relates to a light suspended filter material for sulfur autotrophic denitrification nitrogen removal, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, the aquaculture industry has become one of the important sources of agricultural non-point source pollution. The aquaculture tail water mainly contains pollutants such as ammonia nitrogen, nitrite, organic pollutants, organic phosphorus, as well as some feed, drug residues, fecal residues, etc. Denitrification and phosphorus removal are the key points in the treatment of aquaculture tail water. In the current situation of traditional aquaculture tail water pollution prevention and control technologies, simple sedimentation tanks and sedimentation ditches have the highest proportion, and the treatment effect is relatively low. The treatment of factory aquaculture tail water mainly adopts treatment technologies with "physical filtration + biological filtration + deep purification" as the main body, such as simple one-pool two-dike facilities, standard "three-pool two-dam" treatment facilities, and "zero-emission" continuous-flow aquaculture tail water treatment equipment, etc. These mainly use natural sedimentation, filtration, aeration, and aquatic plants to remove pollutants in the water. They have a large floor area and a long process flow. The filter dam is a hollow structure, and a ceramsite filter material layer, a volcanic rock filter material layer, and a quartz sand filter material layer are sequentially arranged from bottom to top inside. After being used for a period of time, the bottom of the filter dam is prone to fouling and cannot be cleaned, and it is necessary to directly replace the filler or turn the material and then wash it with a large amount of water. Therefore, in the field of aquaculture tail water treatment, how to improve the tail water treatment efficiency, reduce the pollutant emission concentration, shorten the treatment process, reduce the facility floor area, simplify the operation and maintenance operation process, and reduce the operation cost is an urgent problem to be solved in the field of aquaculture tail water treatment in the aquaculture industry.

[0003] The commonly used denitrification nitrogen removal process is a biological denitrification filter, and the selection of the filter material is the key. Denitrification nitrogen removal is divided into heterotrophic denitrification nitrogen removal and autotrophic denitrification nitrogen removal.

[0004] Currently, there is a common problem of insufficient carbon source in sewage treatment. The heterotrophic denitrification nitrogen removal process has poor adaptability, requires additional carbon source input, and has a large amount of sludge production during the process. There are problems such as high economic cost of carbon source, carbon source breakthrough, and high sludge treatment cost during application.

[0005] Heterotrophic heavy filter material: Common biological filter fillers include quartz sand, ceramsite, etc. The specific gravity of these filter materials is greater than that of water, and they are heavy filter materials. A large amount of backwashing power and backwashing water volume are required during the backwashing process. Quartz sand is broad-spectrum and easy to obtain, but it is prone to fouling, has a high backwashing frequency, and the filler will be stratified after backwashing; the surface of the ceramsite filter material is rough, which is conducive to the attachment of microorganisms, but the filler is prone to caking, has a large head loss, and the backwashing is more difficult. When applied, the disadvantage is that a supporting layer needs to be set at the bottom of the biological denitrification filter. Due to the gravity of the filler itself, the equipment cannot be made too high. The backwashing of the equipment will have a cleaning dead angle due to the obstruction of the supporting bracket; the influent also has a large influent resistance and high water loss due to the existence of the supporting bracket.

[0006] Heterotrophic lightweight filter media: To solve the problems of the above-mentioned heterotrophic heavyweight filter media, some researchers used polystyrene as the main raw material to prepare lightweight filter media for use in biological filters. While such fillers have the function of denitrification and nitrogen removal, they can intercept suspended solids in sewage. However, such lightweight filter media have problems such as brittle physical properties, easy deformation, easy cracking, and low resistance to impact loads. Patent No. CN 105621606 A, "A Novel Lightweight Filter Media Denitrifying Biological Filter", mentions a modified polystyrene filler that solves the problems of the above-mentioned lightweight filter media, enhances the impact resistance of the filler, reduces the loss of the filter media, and improves the denitrification effect. However, an external carbon source needs to be added during use, and the problems of "unaffordable carbon source" and carbon source penetration have not been solved.

[0007] In recent years, under the guidance of the "dual carbon" policy, the autotrophic denitrification and nitrogen removal technology based on sulfur has become a research hotspot.

[0008] Sulfur autotrophic denitrification refers to the process in which certain obligate inorganic chemolithoautotrophic sulfur bacteria genera such as Thiobacillus denitrificans use reduced sulfur (S2-, S, S2O32-, etc.) as an electron donor and inorganic carbon as a carbon source to reduce nitrate to nitrogen under anaerobic or anoxic conditions.

[0009]

[0010] S2O3 2- +1.6NO3 - +0.2H2O→2SO4 2- +0.8N2+0.4H +

[0011]

[0012] Autotrophic denitrification and nitrogen removal do not require an external organic carbon source, and have technical advantages such as reducing the cost of the denitrification process, having no risk of residual organic matter in the effluent, low biomass production during the reaction, less sludge production, reduced subsequent sludge treatment, and low microbial pollution in the effluent. It can be seen from the above chemical formula that the sulfur autotrophic denitrification process consumes alkalinity. Through research, it has been found that the suitable pH for the survival of sulfur autotrophic denitrifying bacteria is 6-8. Therefore, additional alkalinity needs to be supplemented to maintain the system pH.

[0013] Autotrophic heavy filter media: People often use a mixture of elemental sulfur and limestone particles as filter media in the biological denitrification filter process. Such a filler has a low porosity, which is not conducive to enriching dominant strains, has a low biological loading, and a poor denitrification effect. Sulfur particles do not have a strong filler skeleton with good wear resistance, and their quality gradually decreases during use due to gradual consumption. They are easily washed away by hydraulic scouring. In addition, as the mechanical strength of the filter media gradually decreases, under the action of gravity, the filter media layer is prone to breakage and collapse. Moreover, during the autotrophic denitrification reaction process of sulfur, acid is produced, and the alkalinity supplement material calcium carbonate in the filler will be dissolved out. The slightly soluble substances block the filler, exacerbating the hardening of the filter media layer, affecting the flow pattern distribution and kinetic energy loss in the system, and affecting contact mass transfer. It is necessary to regularly backwash the filter, which increases the operating cost, control complexity, maintenance workload, etc., and affects the process applicability.

[0014] Patent No. CN 113860518 A, "A Sulfur Autotrophic Composite Filter Media and Its Preparation Method and Application", mixes boron mud and sulfur and cures them to form a sulfur autotrophic composite filter media, which is a heavy spherical or columnar filler and is applied to a packed bed or fixed bed filter or applied to an artificial wetland. Although the filler solves the problems of hardening of the denitrification filter layer and excessive sulfur, there are still problems such as low filler utilization rate, large backwashing head loss, incomplete backwashing, high backwashing frequency, poor backwashing effect, and short filler replacement cycle.

[0015] Patent No. CN 111285462 B, "Synergistic Denitrification Composite Suspended Packing, Its Preparation Method and Application", mentions an autotrophic-heterotrophic synergistic denitrification composite suspended packing, which contains elemental sulfur, calcium carbonate and coal powder, and its specific gravity is 0.9 - 1.1 g / cm3. The filler utilizes the synergistic effect of autotrophic-heterotrophic denitrification, and has a high denitrification efficiency and a high filler utilization rate. However, with the domestication of microorganisms, microorganisms form a biofilm on the surface of the filler, and the specific gravity of the filter media gradually increases. The filter media will sink due to gravity, and external force is needed to keep the filler in a sulfide or suspended state. Moreover, after research, when both carbon source and sulfur source exist in the filler, because heterotrophic bacteria have a fast growth rate, the carbon source will be preferentially utilized, and heterotrophic bacteria will become the dominant strains, and autotrophic denitrification of sulfur will be inhibited, which is not conducive to autotrophic denitrification.

[0016] Therefore, it is urgent to solve the problems of poor mechanical strength of the filler, easy hardening and fouling blockage in heterotrophic or autotrophic denitrification, as well as the problems of the process requiring an external carbon source, long process flow, and low treatment efficiency. Summary of the Invention

[0017] The object of the present invention is to solve the above technical problems, and to provide a light suspended filter material for sulfur autotrophic denitrification and its preparation method and application. By using the sulfur in the sulfur autotrophic denitrification filter material as an electron donor, nitrate nitrogen in water is converted into nitrogen gas, thereby reducing the nitrogen content in sewage. Combined with its application equipment, a long-term stable denitrification effect can be achieved, and the application problems existing in heterotrophic denitrification or autotrophic denitrification, such as poor mechanical strength of the packing, easy caking and fouling, large consumption of backwashing power and backwashing water volume during the backwashing process, the need for an external carbon source in the process, long process flow, low treatment efficiency, high operating cost, complex control, large maintenance workload, and low process applicability, can be solved.

[0018] The technical solution adopted to achieve the object of the present invention is as follows:

[0019] A light suspended filter material for sulfur autotrophic denitrification, the filter material is made of the following raw materials in parts by weight: 10-90 parts of polystyrene, 5-30 parts of elemental sulfur, 0.5-50 parts of alkalinity supplement, 5-10 parts of foaming agent, and 0.5-20 parts of auxiliary agent; the elemental sulfur is sulfur powder or particles with a purity of more than 90% and a mesh size of 100-300; the diameter of the filter material is 2-15 mm, the density is 55-900 kg / m3, the porosity > 45%, and the specific surface area > 1000 m 2 / m 3 .

[0020] Preferably, the polystyrene is polymerized from styrene resin or recycled EPS recycled material is selected; the alkalinity supplement is one or two of sodium silicate and calcium carbonate.

[0021] Preferably, the foaming agent is one or two of pentane and butane, or the foaming agent is petroleum ether containing pentane or one or more of propane, butane, pentane, isopentane, neopentane, propylene, butene and butadiene.

[0022] Preferably, the auxiliary agent is an initiator, a flame retardant, a cell size regulator, an anti-caking agent and a pigment; the initiator is one or more of 0.5% of tetrabromoethane plus 0.5% of diisopropylbenzene peroxide, 1,2-dibromotetrachloroethane or tris(2,3-dibromopropyl) phosphate; the flame retardant is one or more of brominated hydrocarbons, phosphate esters and aluminum hydroxide; the cell size regulator is one or more of sodium dodecylbenzenesulfonate and silicone oil; the anti-caking agent can be one or more of soap powder, calcium fatty acid, talc powder, sodium aluminosilicate and ferric thiocyanate; the pigment can be one or more of masterbatch, iron red, chrome yellow, titanium white, carbon black.

[0023] The present invention also provides a preparation method of a light suspended filter material for sulfur autotrophic denitrification, including the following steps:

[0024] S1. Weigh each raw material according to the parts by weight;

[0025] S2. Mix the raw materials and recast into pellets: Adjust the reaction kettle to isolate air, make the working temperature exceed 110 °C, put polystyrene, sulfur, alkalinity supplement, and additives into the reaction kettle, fully stir and mix for a certain time, then lower the temperature to below 100 °C, transfer the material to a granulator, the granulator extrudes bead pellets, the bead pellets are air-cooled to below 40 °C and then solidify and form. After screening, the same-grade bead pellets are obtained for standby;

[0026] S3. Add blowing agent: Adjust the dissolving pot, make the working temperature exceed 80 °C, the working pressure is above 1 Mpa, stir, add the same-grade bead pellets from step S2 into the dissolving pot, and at the same time add the blowing agent, keep the temperature and pressure constant in the dissolving pot, stir for 4 - 12 h to make the blowing agent penetrate into the bead pellets, then lower the temperature to below 40 °C, discharge, wash with tap water, filter, dry, and store in the warehouse for refrigeration for standby, the refrigeration temperature is 10 - 15 °C;

[0027] S4. Pre-expand and form, and the finished product is for standby: Adjust the pre-expander, make the working temperature exceed 90 °C, stir, put the bead pellets from step S3 into the pre-expander, the bead pellets expand at a constant temperature, control the density after expansion to be 55 - 900 kg / m3, the diameter is 2 - 15 mm, the porosity > 45%, and the specific surface area > 1000 m 2 / m 3 , then the material can be discharged. The foam beads are formed after screening and air-cooling to below 40 °C for curing, and after being dried and cured, they are bagged to obtain the finished product.

[0028] Preferably, in step S2, the working temperature is 115 - 120 °C, the stirring speed is 10 - 100 r / min, the stirring time is 3 - 5 h, the temperature is lowered to 80 - 100 °C, and the granulator extrudes bead pellets with a diameter of 3 - 6 mm.

[0029] Preferably, in step S3, the working temperature is 80 - 90 °C, the stirring speed is 10 - 55 r / min; in step S4, the working temperature is 90 - 105 °C, and the stirring speed is 10 - 55 r / min.

[0030] The present invention also provides an application of the sulfur autotrophic denitrification and nitrogen removal lightweight suspended filter material as described above in the sewage treatment of nitrate - contaminated municipal, industrial, surface water, groundwater or aquaculture fields.

[0031] Preferably, it includes equipment for sewage treatment. The equipment includes a denitrification light filter. One side at the lower end of the denitrification light filter is connected to a feed water pump through a hose, and one side close to the feed water pump is connected to a backwash aeration fan through an air pipe; at the upper end inside the denitrification light filter, there is a pressure-bearing filter plate filter head, and the filter media described in claim 1 is placed below the pressure-bearing filter plate filter head; at the upper end of the denitrification light filter and above the pressure-bearing filter plate filter head, there is a backwash water inlet, and the backwash water inlet is connected to a backwash water storage tank through a pipeline; at the lower end of the denitrification light filter and on the opposite side of the feed water pump, there is a backwash water outlet; at the upper end of the denitrification light filter and on the opposite side of the backwash water inlet, there is a filter tank process water outlet.

[0032] Preferably, the specific steps of sewage treatment are as follows:

[0033] (1) Filling the filter media: Add the filter media to the denitrification light filter, with a filling ratio of 50 - 60%, and domesticate the filler microorganisms in the denitrification light filter system for 15 - 20 days.

[0034] (2) Water inlet: Start the feed water pump, and the feed water pump sends the aquaculture tail water from bottom to top into the denitrification light filter, including the water distribution and air distribution area, the filter media reaction area, and the clear water area in the denitrification light filter; a pressure-bearing filter plate filter head is arranged in the upper-middle part of the denitrification light filter. Under the action of the pressure-bearing filter plate filter head, the filter media is intercepted in the denitrification light filter, and the tightly pressed filter media layer will have a blocking effect, removing the suspended solids and total phosphorus in the sewage; the treated aquaculture tail water overflows from the water outlet at one end of the upper part of the denitrification light filter to the next process section by means of self-flow.

[0035] (3) When there is a fouling phenomenon in the denitrification light filter and the pressure detector below the tightly pressed filter media layer detects that the pressure reaches a certain level, the automatic control system starts the backwashing process. First step, stop the feed water pump from feeding water, and simultaneously open the backwash water outlet. The water stored in the backwash water storage tank flows downward under the action of gravity, and the liquid level in the denitrification light filter drops. The solid suspended matter intercepted at the bottom of the filter media first drains out from the backwash water outlet under the action of gravity, thus removing the fouling blocked at the bottom of the filter media; Second step, when the liquid level drops to a certain height, it can be controlled by time or liquid level. Close the backwash water outlet, simultaneously start the feed water pump to feed water, and at the same time turn on the backwash aeration fan for pulsed intermittent aeration to wash the filter media layer. The filter media layer is dispersed, and the solid suspended matter and aging biofilm attached to the surface of the filter media are washed off by air and sink to the bottom of the tank; Third step, when the liquid level in the denitrification light filter rises to the initial state, stop the feed water pump from feeding water, and simultaneously open the backwash water outlet. The water stored in the backwash water storage tank flows downward under the action of gravity, and the liquid level in the denitrification light filter drops. The solid suspended matter and aging biofilm intercepted by the filter media drain out from the backwash water outlet under the action of gravity. Repeat steps one to three several times in this way.

[0036] A lightweight suspended filter material for sulfur autotrophic denitrification nitrogen removal according to the present invention is conducive to enriching special dominant bacteria for sulfur autotrophic denitrification, and has the characteristics of large specific surface area, high biological load, high denitrification efficiency, good biological affinity, high mechanical property strength, no sinking of the filler after biological film formation, low backwashing power consumption, stable effluent, and strong process adaptability; during use, due to the S source contained in the filler itself, sulfur autotrophic denitrification can be carried out under low dissolved oxygen conditions without adding external carbon sources and with less sludge production; it has the functions of denitrification, phosphorus removal, and suspended solid removal, integrating the functions of "denitrification + filtration", which can shorten the treatment process flow and reduce the floor area of facilities. It can be used as a filler or filter material in a denitrification lightweight filter pool, solving the technical problems of carbon source addition, insufficient carbon source, high carbon source cost, carbon source penetration, easy clogging of the filler, many supporting electromechanical devices, and high operating cost in the traditional heterotrophic denitrification nitrogen removal process; it can be applied to the deep treatment field of aquaculture tail water, removing phosphorus and some feed, residual bait, feces, etc. in the water while removing nitrate nitrogen, which can shorten the process and floor area and has low operating cost; it can also be applied to the filter dam of the "three-pond two-dam technology" to prevent clogging at the bottom of the filter dam and improve the denitrification treatment efficiency; at the same time, it can also be applied to the deep denitrification treatment of sewage in other nitrate-polluted municipal, industrial, surface water, groundwater, aquaculture and other fields.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] The main raw materials adopted in the embodiments of the present invention are formed by foaming after mixing polystyrene, sulfur, an alkalinity supplement, a foaming agent, and other auxiliaries, and the raw materials are simple, easy to obtain, and prepare.

[0039] One of the main components of the filler is polystyrene, which is the filler skeleton, light in texture, hydrophobic, with a density less than that of water. After foaming, it forms porous foam balls, which can lift other heavier raw materials. Under the action of buoyancy, the filler is in a suspended state in water. Under the synergistic action of other preparations, the filler has high mechanical property strength, is not easy to deform, is not easy to crack, and has a high impact load resistance, solving the technical problems of easy clogging of the traditional heavy filler for denitrification nitrogen removal, many supporting electromechanical devices, and high operating cost.

[0040] The filler itself contains a sulfur source. Under anaerobic or anoxic conditions, certain obligate chemolithoautotrophic sulfur bacteria such as Thiobacillus denitrificans use reduced sulfur as an electron donor and inorganic carbon as a carbon source to reduce nitrate to nitrogen gas, solving the technical problems of carbon source addition, insufficient carbon source, high carbon source cost, and carbon source penetration in the traditional heterotrophic denitrification nitrogen removal process.

[0041] The filler itself contains an alkalinity supplement. Firstly, it provides alkalinity during the sulfur autotrophic denitrification process, enabling the sulfur autotrophic denitrifying bacteria in the entire reaction system to survive in an environment with a pH of 6 - 8 without the need to adjust the pH, which is conducive to enriching the special dominant bacteria of sulfur autotrophic denitrification. Secondly, preferably, the alkalinity supplement is one or more of sodium silicate and calcium carbonate. Utilizing its stable and hard lattice structure, it adjusts the hardness of the filler and further improves the mechanical properties of the filler.

[0042] The foaming agent can cause the granular polystyrene mixed filler to foam into a spherical porous lightweight filter material under specific constant temperature and pressure conditions. The diameter of the foamed filler is 2 - 15 mm, and the density is 50 - 900 kg / m 3 , with a porosity > 45% and a specific surface area > 1000 ㎡ / m3. It has a large specific surface area, can remove phosphorus while having efficient deep denitrification, has a high biological loading capacity, and good biological affinity. After biological film formation, the filler will not sink, enriching a large number of sulfur autotrophic denitrifying bacteria, with a high denitrification efficiency, resulting in good effluent treatment effect and stable effluent.

[0043] The embodiment of the present invention can be used as a filler or filter material in a denitrification lightweight filter tank, without the need to add new mechanical and electrical equipment, and can reduce the carbon source dosing system, solving the problems of carbon source dosing, "unaffordable carbon source", and carbon source penetration in the traditional heterotrophic denitrification lightweight filter tank process.

[0044] The embodiment of the present invention can be used as a filler or filter material in the filter dam of the "three - pond two - dam technology". While removing nitrate nitrogen, it can also remove organic phosphorus in water, as well as some feeds, residual baits, feces, etc. The functions of "denitrification + filtration" are integrated, shortening the treatment process flow, reducing the facility footprint, and having low operating costs, solving the problems of easy fouling and low treatment efficiency at the bottom of the traditional filter dam.

[0045] The present invention has a wide range of applications and can also be applied to the advanced denitrification treatment of sewage in other nitrate - contaminated municipal, industrial, surface water, groundwater, aquaculture and other fields.

[0046] The above description is only an overview of the technical solution of the present invention. In order to understand the technical means of the present invention more clearly and to implement it according to the content of the specification, the following are the preferred embodiments of the present invention and are described in detail with the attached drawings as follows. The specific implementation manner of the present invention is given in detail by the following embodiments and their attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a physical diagram of a sulfur autotrophic denitrification denitrification lightweight suspension filter material of the present invention;

[0048] Figure 2 It is a simplified process flow diagram for the preparation of a sulfur autotrophic denitrification denitrification lightweight suspension filter material of the present invention;

[0049] Figure 3 It is the process flow diagram of the denitrification light filter tank;

[0050] Figure 4 It is the curve graph of the operation nitrate nitrogen removal load of the sulfur autotrophic denitrification light suspended filter material and the traditional denitrification filter material changing with time;

[0051] Figure 5 It is the schematic diagram of the application of a sulfur autotrophic denitrification light suspended filter material provided by the present invention in the filtration dam of the "three-pond and two-dam technology".

[0052] Reference numerals: Figure 3 In it, 1 - inlet water pump; 2 - front-end water inlet of the denitrification light filter tank process; 3 - backwashing aeration fan; 4 - backwashing water storage tank; 5 - water outlet of the denitrification light filter tank process; 6 - denitrification light filter tank; 7 - backwashing water outlet; 8 - filter material; 9 - backwashing water inlet; 10 - pressure-bearing filter plate filter head;

[0053] Figure 5 In it, 11 - circulating water pump; 12 - ecological ditch; 13 - sedimentation tank; 14 - filtration dam 1; 15 - aeration tank; 16 - filtration dam 2; 17 - ecological purification tank; 18 - control valve 1; 19 - control valve 2; 20 - control valve 3; 21 - control valve 4; 22 - control valve 5; 23 - air distribution pipe. Specific embodiments

[0054] To make the purpose, technical solutions and advantages of the present invention clearer and more understandable, the following gives preferred embodiments with reference to the attached drawings and further elaborates on the present invention in detail. However, it should be noted that many details listed in the specification are only for enabling the reader to have a thorough understanding of one or more aspects of the present invention, and these aspects of the present invention can be implemented even without these specific details.

[0055] Example 1 Preparation of sulfur autotrophic denitrification light suspended filter material

[0056] This example provides a sulfur autotrophic denitrification light suspended filter material for denitrification and phosphorus removal in the biological denitrification filter in the denitrification process section of aquaculture wastewater treatment. The filter material is a spherical porous light filter material.

[0057] This example provides a preparation method of a sulfur autotrophic denitrification light suspended filter material. The process flow is shown in Figure 2 , and the detailed steps are as follows:

[0058] S1. Weigh the following raw materials by mass parts:

[0059] (1) Polystyrene: 60 parts, meeting the standard of "Polystyrene (PS) Resin" (GB / T 12671 - 2008), PS, MLN, 090 - 04 first - class technical requirements;

[0060] (2) Sulfur: 10 parts, sulfur powder meeting the standard of "National Food Safety Standard Food Additive Sulfur" (GB / 3150 - 2010), S(W) ≥ 99.9%, 100 mesh;

[0061] (3) Alkalinity supplement: 20 parts of sodium silicate, modulus n = SiO2 / Na2O (molar ratio) = 1.5;

[0062] (4) Foaming agent: 5 parts of pentane;

[0063] (5) Initiator: 1 part of 0.5% tetrabromoethane plus 0.5% dicumyl peroxide;

[0064] (6) Flame retardant: 1 part of brominated hydrocarbon;

[0065] (7) Cell size regulator: 1 part of sodium dodecylbenzenesulfonate;

[0066] (8) Anti - caking agent: 1 part of soap powder;

[0067] (9) Pigment: 1 part of chrome yellow.

[0068] S2. Mixing raw materials and re - casting into pellets: Adjust the reaction kettle, introduce nitrogen to isolate air, and the working temperature is 115°C; Put 60 parts of polystyrene, 10 parts of sulfur, 20 parts of sodium silicate, 1 part of 0.5% tetrabromoethane plus 0.5% dicumyl peroxide, 1 part of brominated hydrocarbon, 1 part of sodium dodecylbenzenesulfonate, 1 part of soap powder, and 1 part of chrome yellow from the raw materials in S1 into the reaction kettle. The rotation speed of the stirring paddle is 25 revolutions / min, and stir and mix well for 3 h until the material becomes sticky paste. Then cool down to 95°C, transfer the sticky paste material to the granulator, and the granulator extrudes beads with a diameter of about 4 mm. After the beads are air - cooled to below 40°C, they are solidified and formed. Sieve out the 4 mm beads with a 4 mm diameter filter screen and set aside for use.

[0069] S3. Adding the foaming agent to the same - level beads: Adjust the dissolving pot, with a working temperature of 83°C and a working pressure of 1 Mpa, and the rotation speed of the stirring paddle is 20 revolutions / min. Add 95 parts of the 4 mm same - level beads from step S2 to the dissolving pot, and at the same time add 5 parts of the foaming agent pentane from S1. Keep the constant working temperature in the dissolving pot at 83°C and the constant pressure at 1 Mpa, and stir for 8 h to make the foaming agent penetrate into the beads. Then cool down to below 40°C, and then discharge. After washing with tap water, filtering, and drying, store in the warehouse for cold storage and set aside for use. The cold storage temperature is 12°C.

[0070] S4. Pre-foaming and preparing the finished product for use: Adjust the pre-foaming machine to a working temperature of 90 °C and a stirring paddle speed of 40 revolutions per minute. Put 100 parts of the S3 beads after weighing into the pre-foaming machine. The beads are foamed at a constant temperature, and the density after foaming is 800 kg / m 3 , with a porosity of 50%, and a specific surface area of 1100 m² / m 3 . Then it can be discharged. The foam beads are screened through an 8 mm mesh screen and air-cooled to below 40 °C for curing. After the sulfur autotrophic denitrification light suspended filter material is dried and cured, it can be bagged and used with a diameter of 8 mm.

[0071] Example 2

[0072] This example provides a preparation method for a sulfur autotrophic denitrification light suspended filter material. The process flow is shown in Figure 2 , and the detailed steps are as follows:

[0073] S1. Weigh the following raw materials by mass:

[0074] (1) Select recycled EPS material: 90 parts;

[0075] (2) Sulfur: 20 parts, sulfur powder meeting the standard of "National Food Safety Standard Food Additive Sulfur" (GB / 3150 - 2010), S(W) ≥ 99.9%, 200 mesh;

[0076] (3) Alkalinity supplement: 40 parts of calcium carbonate;

[0077] (4) Foaming agent: 10 parts of petroleum ether containing pentane;

[0078] (5) Initiator: 2 parts of 0.5% tetrabromoethane plus 0.5% 1,2 - dibromotetrachloroethane;

[0079] (6) Flame retardant: 1 part of phosphate ester;

[0080] (7) Cell size regulator: 1.5 parts of silicone oil;

[0081] (8) Anti - caking agent: 2 parts of talcum powder;

[0082] (9) Pigment: 1 part of masterbatch.

[0083] S2. Mix raw materials and recast and granulate: Adjust the reaction kettle, introduce nitrogen to isolate air, and the working temperature is 115°C; select 90 parts of recycled EPS, 20 parts of sulfur, 40 parts of calcium carbonate, 2 parts of 0.5% tetrabromoethane plus 0.5% 1,2-dibromotetrachloroethane, 1 part of phosphate ester, 1 part of silicone oil, 1.5 parts of soap powder, and 1 part of masterbatch powder from the recycled materials in S1 above and put them into the reaction kettle. The stirring paddle rotates at 25 revolutions per minute, and stir and mix fully for 3 hours until the material becomes a viscous paste. Then cool it down to 95°C, transfer the viscous paste material to a granulator, and the granulator extrudes beads with a diameter of about 4 mm. After the beads are air-cooled to below 40°C, they are solidified and formed. After screening out 4-mm beads with a 4-mm diameter filter screen, they are ready for use.

[0084] S3. Add blowing agent to beads of the same grade: Adjust the dissolving pot, with a working temperature of 83°C and a working pressure of 1 Mpa, and the stirring paddle rotates at 20 revolutions per minute. Add 95 parts of 4-mm beads of the same grade from step S2 to the dissolving pot, and at the same time add 10 parts of petroleum ether containing pentane from S1. Keep the constant working temperature in the dissolving pot at 83°C and the constant pressure at 1 Mpa, and stir for 8 hours to make the blowing agent penetrate into the beads. Then cool it down to below 40°C, and then it can be discharged. After washing, filtering, and drying with tap water, it is stored in the warehouse for refrigeration and standby. The refrigeration temperature is 12°C.

[0085] S4. Pre-expand and form, and the finished product is ready for use: Adjust the pre-expander, with a working temperature of 90°C and the stirring paddle rotates at 40 revolutions per minute. Put 100 parts of the beads from S3 after weighing into the pre-expander. The beads are foamed at a constant temperature. After foaming, the density is 800 kg / m 3 , the porosity is 50%, and the specific surface area is 1100 m² / m 3 Then it can be discharged. The foam beads are screened through an 8-mm mesh screen and air-cooled to below 40°C for curing. After the sulfur autotrophic denitrification and nitrogen removal lightweight suspended filter material is dried and cured, it can be used after being bagged with a diameter of 8 mm.

[0086] Application and effect of the filler in the denitrification lightweight filter tank in Example 3

[0087] Apply the sulfur autotrophic denitrification and nitrogen removal lightweight suspended filter material prepared in Example 1 to Figure 3 the denitrification lightweight filter tank for denitrification and phosphorus removal in the biological denitrification filter tank in the denitrification process section of aquaculture tail water treatment. The specific implementation is as follows:

[0088] Add the 8-sulfur autotrophic denitrification and nitrogen removal lightweight suspended filter material to the 6-denitrification lightweight filter tank, and the filling ratio is 50-60%. Without adding an external carbon source, the filler in the 6-denitrification lightweight filter tank system is domesticated by microorganisms for 15-20 days to make the surface of the filter material covered with sulfur autotrophic denitrification microbial film, and then start normal water inlet.

[0089] Water inlet process: 1 - The inlet water pump starts. The 1 - inlet water pump sends the aquaculture tail water at the front end of the 2 - denitrification light filter process to the 6 - denitrification light filter. The aquaculture tail water flows from bottom to top and successively passes through the water distribution and gas distribution area, the filter media reaction area, and the clear water area in the 6 - denitrification light filter. In the filter media reaction area, the biofilm on the surface of the filter media undergoes denitrification with the nitrate nitrogen in the sewage, and the nitrogen in the sewage is removed. Under the action of the 10 - pressure - bearing filter plate filter head, the 8 - sulfur autotrophic denitrification light - weight suspended filter media is intercepted in the 6 - denitrification light filter. The tightly pressed filter media layer will have a blocking effect, and the suspended solids and total phosphorus in the sewage are removed. The treated aquaculture tail water overflows from the 5 - outlet of the denitrification light filter process to the next process section by gravity flow.

[0090] Backwashing process: When there is a fouling phenomenon in the 6 - denitrification light filter and the pressure detected by the pressure detector below the tightly pressed filter media layer reaches a certain level, the automatic control system starts the backwashing process. First step, the 1 - inlet water pump stops water inlet, and simultaneously the 7 - backwash water outlet opens. The water stored in the 4 - backwash water storage tank flows downward under the action of gravity, and the liquid level in the 6 - denitrification light filter drops. The solid suspended solids intercepted at the bottom of the 8 - sulfur autotrophic denitrification light - weight suspended filter media are first discharged from the 7 - backwash water outlet, thereby removing the fouling blocked at the bottom of the 8 - sulfur autotrophic denitrification light - weight suspended filter media. Second step, when the liquid level drops to a certain height, it can be controlled by time or liquid level. The 7 - backwash water outlet closes, and simultaneously the 1 - inlet water pump starts water inlet, and at the same time the 3 - backwash aeration fan starts pulse - type intermittent aeration to wash the 8 - sulfur autotrophic denitrification light - weight suspended filter media layer. The filter media layer is dispersed, and the solid suspended solids and aged biofilm attached to the surface of the filter media are washed off by gas and sink to the bottom of the pool. Third step, when the liquid level in the 6 - denitrification light filter rises to the initial state, the 1 - inlet water pump stops water inlet, and simultaneously the 7 - backwash water outlet opens. The water stored in the 4 - backwash water storage tank flows downward under the action of gravity, and the liquid level in the 6 - denitrification light filter drops. The solid suspended solids and aged biofilm intercepted by the 8 - sulfur autotrophic denitrification light - weight suspended filter media are discharged from the 7 - backwash water outlet under the action of gravity. These steps one to three are repeated several times. Adopting the counter - current water - gas alternating backwashing technology can effectively remove solid suspended solids and aged biofilm, with a small gas washing intensity, low energy consumption, and no need for a backwash water pump; the water washing is thorough, and the pollutants are discharged to the bottom by gravity along with the backwash water flow, and the cleaning effect is better; intelligent control, the program is adjustable, the operation is simple, and the cost is reduced and the efficiency is increased.

[0091] Inlet water quality of aquaculture tail water: Suspended solids = 216 mg / L, PH = 7.4, CODMn = 50 mg / L, Total phosphorus = 3.6 mg / L, Total nitrogen = 20.0 mg / L, Nitrate nitrogen = 6.5 mg / L.

[0092] Effluent quality of aquaculture tail water: suspended solids ≤ 100 mg / L, pH = 7 - 7.5, CODMn ≤ 25 mg / L, total phosphorus ≤ 1.0 mg / L, total nitrogen ≤ 5.0 mg / L, nitrate nitrogen ≤ 0.5 mg / L.

[0093] The following examples are for the treatment of aquaculture tail water in a certain aquaculture area in Guangxi. It is a data comparison of the application of 8-sulfur autotrophic denitrifying lightweight suspended filter media in a denitrifying lightweight filter tank and the application of traditional denitrifying filter media in a denitrifying lightweight filter tank. For details, see Figure 4 , Results: (1) The denitrification efficiency of the present invention is high, and the nitrate nitrogen removal load is about 1 kg(NO3--N) / (m3 / d), which is twice that of traditional denitrifying filter media. (2) The stable time of the effluent treated by the present invention is longer. (3) After backwashing at the same time, the recovery of the filter media effluent in the system of the present invention is shorter. (4) There is no need to supplement alkali to adjust pH = 6 - 9.

[0094] Application of the three-pond two-dam in Example 4

[0095] Apply the sulfur autotrophic denitrifying lightweight suspended filter media prepared in Example 1 to Figure 5 the filtration dam of the "three-pond two-dam technology" as an upgrade of the "three-pond two-dam technology" in the existing aquaculture tail water treatment field. The specific implementation is as follows:

[0096] (1) Process flow of the new "three-pond two-dam technology" in the example: aquaculture tail water in the aquaculture area → ecological ditch (original) → sedimentation tank (original) → filtration dam 1 (technological transformation) → aeration tank (original) → filtration dam 2 (technological transformation) → ecological purification tank

[0097] (2) Application of the sulfur autotrophic denitrifying lightweight suspended filter media in the filtration dam of the "three-pond two-dam technology": Usually, the filtration dam is surrounded by pond bottom reinforcement or brick-concrete structure, with bottom water inlet, upper water outlet, and a hollow structure in the middle. The external wall is built with hollow bricks, and the direction of the holes in the hollow bricks is consistent with the water flow direction. The dam body is filled with filter media of different sizes, and the filter media is selected from volcanic stones, ceramsites, gravels, palm fibers, and activated carbons, etc., to further filter out suspended solids in the water body. First step, replace the filler in the original filtration dam with the sulfur autotrophic denitrifying lightweight suspended filter media prepared in Example 1, and the filling volume is about 50 - 60%; second step, add 10 - pressure-bearing filter plate filter heads at the upper water outlet of the filtration dam; third step, use the blower of the original aeration tank as the 3 - backwashing aeration blower, and add a gas-washing backwashing 23 - air distribution pipe at the bottom of the filtration dam; fourth step, use the original 11 - circulating water pump, and add pipelines and 18 - control valve 1, 19 - control valve 2, 20 - control valve 3, 21 - control valve 4, 22 - control valve 5 according to the diagram.

[0098] (3) Normal operation process of the system: Before the system operates normally, the filter media in the filter dam need to be inoculated with sludge and domesticated in advance for 15 - 20 days. After the surface of the 8 - sulfur autotrophic denitrification light - weight suspended filter media is covered with a microbial film, the system starts to receive normal influent water. The aquaculture tail water in the aquaculture area enters the sedimentation tank through the ecological ditch. In the sedimentation tank, large - particle substances in the aquaculture tail water sink to the bottom of the tank under the action of gravity. The effluent from the sedimentation tank enters Filter Dam 1. The water passes through the bottom of Filter Dam 1 and then through the 8 - sulfur autotrophic denitrification light - weight suspended filter media layer from bottom to top. Solid suspended substances in the water are intercepted. Without adding a carbon source, under the action of the sulfur source in the filter media itself, sulfur - autotrophic bacteria on the surface of the filter media react with nitrate nitrogen, and then turn into nitrogen gas and escape from the water body. Some solid phosphorus in the water is intercepted by the filter media or organic phosphorus is utilized by the growth of microorganisms and thus removed. The effluent flows by gravity from the top of the filter dam into Aeration Tank 1. Aeration is carried out in Aeration Tank 1. Using aerobic dominant microorganisms such as nitrifying bacteria and Bacillus in the sewage, organic matters such as COD in the water are removed, and ammonia nitrogen is oxidized to nitrate nitrogen. The effluent enters Filter Dam 2 from the bottom. In Filter Dam 2, the water passes through the 8 - sulfur autotrophic denitrification light - weight suspended filter media layer from bottom to top. Solid suspended substances in the water are further intercepted. Sulfur - autotrophic denitrification occurs on the surface of the filter media, and nitrate nitrogen in the sewage is deeply removed. The effluent from Filter Dam 2 flows by gravity from the top of the dam into Ecological Purification Pond 1. In Ecological Purification Pond 1, aquatic plants are planted to continue absorbing and utilizing residual nutrients such as nitrogen and phosphorus in the water body. The effluent treated by Ecological Purification Pond 1 can be discharged or pumped to the front - end aquaculture area for recycling through the 11 - circulating water pump.

[0099] (4) Air - water combined backwashing process of the filter dam: Start the 3 - backwashing aeration fan. The 3 - backwashing aeration fan operates in a pulsed manner. The 8 - sulfur autotrophic denitrification light - weight suspended filter media layer in the filter dam is loosened, and the intercepted solid suspended substances and aged biofilm fall off to the bottom of the tank. The control valve can be controlled in a time - or liquid - level - controlled interlock. Close Control Valve 2, Control Valve 1, and Control Valve 5, open Control Valve 3 and Control Valve 4, start the 11 - circulating water pump. The solid suspended substances intercepted at the bottom of the 8 - sulfur autotrophic denitrification light - weight suspended filter media layer in the filter dam are discharged. The solid suspended substances enter the sedimentation tank through the ecological ditch and then precipitate. The clear water enters the filter dam from the bottom of the filter dam, and the liquid level returns to the normal height. The backwashing ends.

[0100] (5) Application effect:

[0101] This embodiment is applied to the filter dam in the "three - pond two - dam technology" for treating the tail water of a bullfrog aquaculture area in Guangxi. The influent water of the "three - pond two - dam" is the tail water of the bullfrog aquaculture area.

[0102] Inlet water quality: suspended solids > 400 mg / L, pH = 7 - 7.8, CODMn = 150 - 200 mg / L, total phosphorus = 4.6 - 5.0 mg / L, total nitrogen = 35.0 - 40.0 mg / L, nitrate nitrogen = 10.0 - 15.0 mg / L;

[0103] Outlet water quality: suspended solids ≤ 100 mg / L, pH = 7 - 7.5, CODMn ≤ 25 mg / L, total phosphorus ≤ 1.0 mg / L, total nitrogen ≤ 5.0 mg / L, nitrate nitrogen ≤ 0.5 mg / L.

[0104] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A light suspended filter material for sulfur autotrophic denitrification and nitrogen removal, characterized in that, The filter material is made of the following raw materials in parts by weight: 10-90 parts of polystyrene, 5-30 parts of elemental sulfur, 0.5-50 parts of alkalinity supplement, 5-10 parts of foaming agent and 0.5-20 parts of auxiliary agent; the elemental sulfur is 100-300 mesh sulfur powder or granules with a purity of more than 90%; the filter material has a diameter of 2-15 mm, a density of 55-900 kg / m3, a porosity of more than 45%, and a specific surface area of more than 1000 m 2 / m 3 .

2. A light suspended filter medium for sulfur autotrophic denitrification nitrogen removal according to claim 1, characterized in that The polystyrene is polymerized from styrene resin or recycled EPS recycled material is selected; the alkalinity supplement is one or two of sodium silicate and calcium carbonate.

3. A light suspended filter medium for sulfur autotrophic denitrification and nitrogen removal according to claim 1, characterized in that, The foaming agent is one or two of pentane and butane, or the foaming agent is petroleum ether containing pentane or one or more of propane, butane, pentane, isopentane, neopentane, propylene, butene and butadiene.

4. A light suspended filter medium for sulfur autotrophic denitrification and nitrogen removal according to claim 1, characterized in that, The auxiliary agents are initiator, flame retardant, cell size regulator, anti-caking agent and pigment; the initiator is one or more of 0.5% tetrabromoethane plus 0.5% dicumyl peroxide, 1,2-dibromotetrachloroethane or tris(2,3-dibromopropyl) phosphate; the flame retardant is one or more of brominated hydrocarbons, phosphate esters and aluminum hydroxide; the cell size regulator is one or more of sodium dodecylbenzenesulfonate and silicone oil; the anti-caking agent can be one or more of soap powder, calcium fatty acid, talc powder, sodium aluminosilicate and ferric thiocyanate; the pigment can be one or more of masterbatch, iron red, chrome yellow, titanium white and carbon black.

5. The preparation method of a light suspended filter material for sulfur autotrophic denitrification nitrogen removal according to claim 1, characterized in that It includes the following steps: S1. Weigh each raw material according to parts by weight. S2. Mix the raw materials and re-cast and granulate: Adjust the reaction kettle, isolate the air, make the working temperature exceed 110 °C, put the polystyrene, sulfur, alkalinity supplement and auxiliary agent into the reaction kettle, fully stir and mix for a certain time, then lower the temperature to below 100 °C, transfer the material to the granulator, the granulator extrudes bead particles, the bead particles are air-cooled to below 40 °C and then solidified and formed, and after screening, the same-level bead particles are obtained for use. S3. Add the foaming agent: Adjust the dissolving pot, make the working temperature exceed 80 °C, the working pressure is above 1 Mpa, stir, add the same-level bead particles in step S2 into the dissolving pot, and at the same time add the foaming agent, keep the temperature and pressure constant in the dissolving pot, stir for 4 - 12 h to make the foaming agent penetrate into the bead particles, then lower the temperature to below 40 °C, discharge the material, wash it with tap water, filter, dry, and store it in the warehouse for refrigeration for use, and the refrigeration temperature is 10 - 15 °C. S4. Pre-expanded molding, and the finished product is ready for use: Adjust the pre-expander, with the working temperature exceeding 90 °C, stir, and put the beads in step S3 into the pre-expander. The beads are foamed at a constant temperature, and the density after foaming is controlled to be 55 - 900 kg / m3, the diameter is 2 - 15 mm, the porosity > 45%, and the specific surface area > 1000 m 2 / m 3 , then the material can be discharged. The foam beads are formed by screening and air-cooling to below 40 °C for curing, and after being dried and cured, they are bagged to obtain the finished product.

6. The preparation method of a sulfur autotrophic denitrification light suspended filter medium according to claim 5, characterized in that, In step S2, the working temperature is 115 - 120 °C, the stirring speed is 10 - 100 r / min, the stirring time is 3 - 5 h, the temperature is lowered to 80 - 100 °C, and bead particles with a diameter of 3 - 6 mm are extruded by the granulator.

7. The preparation method of a light suspended filter material for sulfur autotrophic denitrification and nitrogen removal according to claim 5, characterized in that, In step S3, the working temperature is 80 - 90 °C, the stirring speed is 10 - 55 r / min; in step S4, the working temperature is 90 - 105 °C, and the stirring speed is 10 - 55 r / min.

8. Application of the sulfur autotrophic denitrification light suspended filter material according to claims 1 - 7 in the sewage treatment of nitrate-polluted municipal, industrial, surface water, groundwater or aquaculture fields.

9. The application according to claim 8, wherein Equipment including sewage treatment, the equipment includes a denitrification light filter. One side of the lower end of the denitrification light filter is connected to a water inlet pump through a hose, and one side close to the water inlet pump is connected to an anti-washing aeration fan through an air pipe; at the upper end inside the denitrification light filter, there is a pressure-bearing filter plate filter head, and the filter material described in claim 1 is placed below the pressure-bearing filter plate filter head; at the upper end of the denitrification light filter and above the pressure-bearing filter plate filter head, there is an anti-washing water inlet, and the anti-washing water inlet is connected to an anti-washing water storage tank through a pipeline; at the lower end of the denitrification light filter and on the opposite side of the water inlet pump, there is an anti-washing water outlet; at the upper end of the denitrification light filter and on the opposite side of the anti-washing water inlet, there is a filter tank process water outlet.

10. The application according to claim 9, wherein The specific steps of sewage treatment are as follows: (1) Filling the filter material: Add the filter material to the denitrification light filter, with a filling ratio of 50 - 60%, and carry out filler microorganism domestication on the denitrification light filter system for 15 - 20 days. (2) Water inlet: Start the water inlet pump, and the water inlet pump sends the aquaculture tail water from bottom to top into the denitrification light filter, including the water distribution and air distribution area, the filter material reaction area, and the clear water area in the denitrification light filter; a pressure-bearing filter plate filter head is arranged in the upper middle part of the denitrification light filter. Under the action of the pressure-bearing filter plate filter head, the filter material is intercepted in the denitrification light filter, and the tightly pressed filter material layer will have a blocking effect, removing the suspended solids and total phosphorus in the sewage; the treated aquaculture tail water overflows from the water outlet at one end of the upper part of the denitrification light filter to the next process section by means of self-flow. (3) When there is a fouling phenomenon in the denitrification light filter and the pressure detected by the pressure detector below the tightly pressed filter material layer reaches a certain level, the automatic control system starts the backwashing process. First step, stop the water inlet of the water inlet pump, and at the same time open the anti-washing water outlet. The water stored in the anti-washing water storage tank flows downward under the action of gravity, and the liquid level in the denitrification light filter drops. The solid suspended solids intercepted at the bottom of the filter material are first discharged from the anti-washing water outlet under the action of gravity, thus removing the fouling blocked at the bottom of the filter material; Second step, when the liquid level drops to a certain height, it can be controlled by time or liquid level. Close the anti-washing water outlet, start the water inlet of the water inlet pump at the same time, and at the same time turn on the anti-washing aeration fan to carry out pulsed intermittent aeration to wash the filter material layer. The filter material layer is broken up, and the solid suspended solids and aging biofilm attached to the surface of the filter material are washed off by air and sink to the bottom of the tank; Third step, when the liquid level in the denitrification light filter rises to the initial state, stop the water inlet of the water inlet pump, and at the same time open the anti-washing water outlet. The water stored in the anti-washing water storage tank flows downward under the action of gravity, and the liquid level in the denitrification light filter drops. The solid suspended solids and aging biofilm intercepted by the filter material are discharged from the anti-washing water outlet under the action of gravity. Repeat steps one to three several times in this way.

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