CN101591064B - Anaerobic built-in zero-valent iron reactor - Google Patents

Abstract

An anaerobic built-in zero-valent iron reactor belongs to the technical field of water treatment. The reactor is provided with 2-6 zero-valent iron filling layers between the water distributor and the biological filter material layer to form a suspended sludge area between the biological filter material layer and the zero-valent iron filling layer and a sludge expansion area between the zero-valent iron filling layer and the water distributor. The suspended sludge zone is connected to a water inlet pipeline at the lower part of the anaerobic reactor through a circulating pipeline and a circulating pump. A set of hydraulic circulation pipelines is arranged outside the anaerobic reactor, so that the water flow speed in the carrier sludge layer and the suspended sludge zone is improved, and the decomposition speed of anaerobic bacteria on organic matters is improved; the reactor is reasonable in structure and good in working performance, can limit expansion and floating loss of a bottom sludge layer, can improve the degradation capacity of organic matters, achieves high organic matter removal rate, and meanwhile achieves quick start of sewage, and later-stage experiments show that successful start of chemical salt-containing wastewater can be achieved in 43 days, and stable operation can be kept in subsequent stages.

Description

Anaerobic built-in zero-valent iron reactor

technical field

The invention relates to an anaerobic built-in zero-valent iron reactor, which belongs to the technical field of water treatment.

Background technique

Anaerobic sewage treatment has strong capacity, saves energy, and produces biogas at the same time. It is one of the most promising processes in sewage treatment. After years of development, the anaerobic reactor has developed from the original septic tank to representative USAB (upflow anaerobic sludge bed), EGSB (expanded granular sludge bed), IC (internal circulation anaerobic reactor )wait. The common characteristics of these third-generation anaerobic reactors are: higher microbial holdings per unit volume, higher hydraulic load, and greatly improved reactor processing capacity.

However, the following main problems still exist in the application of these reactors: (1) The start-up time is long and the sludge granulation is slow. Generally, it takes 3-6 months to start-up, which is difficult to meet the requirements of polluting enterprises for treatment within a limited period. (2) It is difficult to control the operating conditions of the reactor, and acidification often occurs, which inhibits the growth of methanogens, resulting in the failure of anaerobic treatment.

In response to the above problems, a lot of research has been carried out at home and abroad. To solve the problem of slow start-up, many methods are currently used: inoculation of granulated sludge, addition of flocculants, optimization of water conservancy conditions, etc. The inoculation of granulated sludge from other reactors is not suitable for most polluting enterprises, it is difficult to realize, and it affects the operation of the original reactor. Add flocculants, such as aluminum salts and iron salts, whose anions (sulfate and chloride) are highly toxic to anaerobic microorganisms and inhibit treatment efficiency. Optimizing hydraulic conditions utilizes hydraulic shearing to achieve rapid granulation by controlling the flow rate and state of water and airflow. This method is generally used as an auxiliary means.

Acidification control of anaerobic reactor is a key control factor in anaerobic operation. Methanogens are sensitive to the pH of the environment. The optimum pH range is 6.8-7.2. A decrease in pH will inhibit methanogens and lead to anaerobic failure in severe cases. Therefore, the acidification of the reactor is a signal of deterioration of the anaerobic treatment effect, and effective means should be taken to increase the pH. In actual treatment, adding lime water, sodium bicarbonate, etc. is often used to stabilize the acidity.

Zero-valent iron is a reductive method for sewage treatment. It is mainly used in processes such as dechlorination, denitrification, and decolorization of pollutants in water. It utilizes the new ecology [H ] and Fe ²⁺ , which can reduce pollutants, and zero-valent iron technology is a pretreatment method commonly used in sewage treatment to improve biodegradability. Many studies regard the internal electrolysis of zero-valent iron as the front-end process of biological treatment. The biodegradability of treated sewage is improved, and the iron ions produced are also conducive to the improvement of subsequent biological treatment performance.

However, the main obstacle in the application of this method is the compaction of the iron filings bed. The zero-valent iron filler is in contact with the air, and the rate of iron oxidation by air is much greater than that of iron in the internal electrolysis. The rapid generation of rust causes adhesion and blockage between iron filings, making the sewage flow short, reducing the efficiency of sewage treatment, and at the same time rust Attached to the iron surface, preventing its further reaction, leading to the failure of the treatment. Therefore, the internal electrolysis method of zero-valent iron has not been successfully applied in practice.

Contents of the invention

In order to overcome the problems existing in the prior art, the present invention provides an anaerobic built-in zero-valent iron reactor, and an outlet water circulation is set outside the anaerobic reactor to enhance the fluidity of sewage and improve its ability to withstand high loads At the same time, a zero-valent iron filling layer is added inside the anaerobic reactor, and the micro-electrolysis of iron filings and activated carbon and the promotion of ferrous iron to the activity of anaerobic microorganisms are used to achieve faster granulation of the sludge, thereby improving the overall anaerobic The start-up time of the oxygen reactor; at the same time, it can neutralize the anaerobic acidification, and solve the problems of rust and hardening in the electrolysis of zero-valent iron, so as to realize its efficient and stable operation.

The technical scheme adopted in the present invention is: an anaerobic built-in zero-valent iron reactor mainly includes a cylindrical anaerobic reactor, and a water distributor, a biological filter, and a water distributor are sequentially arranged in the anaerobic reactor Material layer and a three-phase separator, the space above the biological filter material layer is a gas-liquid-solid separation zone, and the lower part of the anaerobic reactor is connected to the water inlet pump through the water inlet pipe. In the anaerobic reactor, 2 to 6 zero-valent iron filling layers are arranged between the water distributor and the biological filter material layer to form a suspended sludge area between the biological filter material layer and the zero-valent iron filling layer and The sludge bulking zone located between the zero-valent iron filling layer and the water distributor; the suspended sludge zone is connected to the water inlet pipeline at the lower part of the anaerobic reactor through a circulation pipeline and a circulation pump. The lowest point of the zero-valent iron filling layer is located at 1/2 of the height of the anaerobic reactor, and the height of the zero-valent iron filling layer is 5% to 10% of the effective height H of the anaerobic reactor. Sieve holes are arranged on the bottom plate and the surrounding wall; 2/3 of the height of the zero-valent iron granular material is filled in the zero-valent iron filling layer.

The height of the biological filter material layer and the three-phase separator is 5%-15% of the effective height H of the anaerobic reactor.

The guiding ideology of the above-mentioned technical solution is: the accessory part of the device includes a sewage return system and a sludge sedimentation system. The sewage return system pumps the sewage from the upper end of the zero-valent iron filling layer into the sewage pipeline at the lower end of the reactor, mixes with the raw sewage, and enters the sludge expansion area of the reactor through the water distribution pipe. Its purpose is to increase the water passing speed through the zero-valent iron filling area, thereby enhancing the coupling effect of anaerobic and zero-valent iron technologies. At the same time, the expansion effect of the lower sludge area is improved, and the contact between sewage and sludge is improved. The main function of the sludge sedimentation system outside the reactor is to further separate sewage and sludge. Since the discharged sewage contains a certain amount of iron ions, it will precipitate into Fe(OH) ₃ when exposed to air. The coagulation formed in this process can remove the colloid in the sewage and improve the efficiency of sewage treatment. The system includes sewage pipes, sedimentation tanks, sewage discharge pipes, etc. The starting point of the system is the sewage outlet of the three-phase separator, after sedimentation, the supernatant is discharged.

Setting a zero-valent iron layer in the middle of the anaerobic reactor is not a simple superposition of anaerobic reactor and zero-valent iron technology, but can form the following coupling effects: 1) the role of iron neutralizes anaerobic acidification; 2) The reduction of zero-valent iron reduces the anaerobic redox potential, enhances the anaerobic atmosphere, and is beneficial to the growth of methanogens; 3) The flocculation of iron is beneficial to the growth of granular sludge, and at the same time reduces the loss of sludge; 4) Absorption Carbon dioxide increases the alkalinity and increases the proportion of methane in the biogas; 5) The enzymatic action of biological iron improves bioavailability. At the same time, due to the isolation from the air, the corrosion of iron is slow, and divalent iron ions are evenly released, completely solving the problem of hardening of iron-carbon electrodes in the air.

The beneficial effects of the present invention are: the anaerobic built-in zero-valent iron reactor is provided with 2 to 6 zero-valent iron filling layers between the water distributor and the biological filter material layer to form a The suspended sludge area between the filling layers and the sludge expansion area between the zero-valent iron filling layer and the water distributor; the suspended sludge area is connected to the water inlet pipe at the lower part of the anaerobic reactor through a circulation pipeline and a circulation pump. The anaerobic reactor has a reasonable structure and good working performance, and overcomes the defects of the upflow anaerobic sludge bed. At the same time, it is simpler in structure and less difficult to design than the internal circulation reactor. Granulation, to achieve rapid start-up of anaerobic reactor, cost-effective and stable operation. The anaerobic reactor can be successfully started within one and a half months by using actual factory wastewater, and can run stably at high concentrations.

Description of drawings

The present invention will be further described below in conjunction with drawings and embodiments.

Figure 1 is a schematic diagram of the structure of an anaerobic built-in zero-valent iron reactor.

Fig. 2 is a schematic diagram of a zero-valent iron filled layer.

Fig. 3 is a comparison curve of the chemical oxygen demand (COD) of the inlet and outlet water during the start-up stage using actual chemical wastewater. The abscissa is the days of stable operation of the anaerobic reactor, and the ordinate is the value of COD. The three curves are the COD value change curves of the influent, reactor and effluent respectively.

Fig. 4 is a comparison curve of the chemical oxygen demand (COD) of the inlet and outlet water in the stable stage of the actual chemical wastewater. The abscissa is the days of stable operation of the anaerobic reactor, and the ordinate is the value of COD. The three curves are the COD value change curves of the influent, reactor and effluent respectively.

Fig. 5 is a comparison curve of sludge particle size change in the anaerobic reactor. The abscissa is the size of the sludge in the anaerobic reactor, and the ordinate is the percentage of solids. The three curves are respectively the change curves of the solid content on the first day, the 42nd day (height 60cm), and the 42nd day (height 10cm).

In the figure: 1. Anaerobic reactor, 1a, gas-liquid-solid separation zone, 1b, hot water jacket, 1c, suspended sludge zone, 1d, sludge expansion zone, 2, three-phase separator, 3, biological filter material layer, 4, zero-valent iron filling layer, 4a, bottom plate, 4b, sieve hole, 4c, upper cover plate, 5, hot water heater, 6, water distributor, 7, hot water circulating pump, 8, base, 9 , water inlet pump, 10, air collecting pipe, 11, water outlet pipe, 12, circulation pipeline, 13, circulation pump; a, sewage, b, biogas, c, clear water, d, sludge.

Detailed ways

Figure 1 shows a schematic structural diagram of an anaerobic built-in zero-valent iron reactor. The device mainly includes a cylindrical anaerobic reactor 1. In the anaerobic reactor 1, a water distributor 6, three zero-valent iron filling layers 4, a biological filter layer 3 and a The three-phase separator 2 divides the inner chamber of the anaerobic reactor 1 into a gas-liquid solid separation zone 1a located above the biological filter material layer 3, a suspension zone located between the biological filter material layer 3 and the zero-valent iron filling layer 4 A sludge zone 1c and a sludge expansion zone 1d between the zero-valent iron filling layer 4 and the water distributor 6 . The shell of the anaerobic reactor 1 is made of plexiglass or FRP, with an inner diameter of 90 cm, a height of 120 cm, and an effective volume of 6.36 L. The height of the biological filter material layer 3 and the three-phase separator 2 is 10% of the effective height of the anaerobic reactor 1 . The sewage a enters the water distributor 6 through the water inlet pump 9, and at the same time, the sludge circulating water flows back through the circulating pump 13. The water distributor 6 mixes the sewage a and the sludge circulating water and distributes water evenly at the bottom. The biological filter material layer 3 Retention of rising sludge. A circulation pipe 12 is provided at the lower end of the suspended sludge area 1c to connect with a circulation pump 13 . The anaerobic reactor 1 is provided with a hot water jacket 1b on the outer wall of the part below the gas-liquid-solid separation zone 1a, and a hot water heater 5 and a hot water circulation pump 7 are connected to the upper and lower parts of the hot water jacket 1b through pipelines.

The working process of the above-mentioned anaerobic reactor is as follows: the sewage a enters the sludge expansion zone 1d of the anaerobic reactor 1 through the inlet pump 9, and at the same time, it is fully mixed with the sludge circulating water at the bottom, and is mixed with the granular sludge during the rising process of the sewage. When fully contacting the organisms, when passing through the zero-valent iron filling layer 4 to reach the sludge circulating water outlet of the suspended sludge zone 1c, most of them flow back to the bottom through the circulation pipeline 12 to continue to react, and a small part reaches the biological filter material layer 3. Most of the suspended sludge in the sewage is intercepted to form a carrier sludge layer, which avoids the rapid accumulation of sludge particles on the three-phase separator 2 and ensures the normal separation function of the three-phase separator 2; a small part rises to three The phase separator 2 separates the suspended organisms from water and gas, and the separated anaerobic sludge is deposited into the anaerobic reactor 1, and the purified clean water c is discharged and received through the outlet pipe 11, while the sewage reacts with the organisms to produce The biogas b is discharged and received through the gas header 10, and the sludge d can be discharged and received from the suspended sludge area 1c.

Fig. 2 shows a schematic diagram of a zero-valent iron filling layer. Three zero-valent iron filling layers 4 are arranged in the anaerobic reactor 1 , and the lowest point of the three superimposed zero-valent iron filling layers 4 is located at 1/2 of the effective height H of the anaerobic reactor 1 . Its filling frame is a glass fiber reinforced plastic cylinder with an upper opening, and its height is 7% of the effective height H of the anaerobic reactor 1. Many evenly distributed sieve holes 4b are arranged on the cylinder surface and the bottom plate 4a, and the aperture of the sieve holes 4b is 5mm. The hole spacing is 15mm. Each filling layer is filled with a certain amount of zero-valent iron granular materials, and the filling height is 2/3 of the actual height of each layer, leaving 1/3 of the upper gap for uniform water distribution. The uppermost filling layer is covered with the upper cover plate 4c of the same sieve hole 4b, so as to avoid the loss of the zero-valent iron filler.

The above-mentioned anaerobic reactor was started and domesticated with sludge from a municipal sewage treatment plant and wastewater from a spice chemical factory. It can be seen from Figure 3 that in the wastewater start-up stage, when the wastewater concentration reaches 5%, the COD removal rate reaches 90%, and when the influent COD is 20,000 mg/L in 43 days of operation, the successful startup has been achieved, and the COD removal rate reaches More than 80%. It can be seen from Figure 4 that when the influent water is completely industrial wastewater, the reactor can achieve stable operation, the effluent COD is basically stable at about 5000mg/L, and the removal rate remains above 75%. It can be seen from Figure 5 that with the operation of the reactor, the sludge particle size of the reactor with zero-valent iron particles gradually increases, from the main particle size of 100 microns at the beginning to about 200 microns at the end of the start-up, indicating that the zero-valent iron The addition of the sludge has a better effect on the granulation of the sludge.

Claims (3)

1. anaerobic built-in zero-valent iron reactor, it mainly comprises a columnar anaerobic reactor (1), in anaerobic reactor (1), be provided with a water distributor (6), a biofilter material layer (3) and a triphase separator (2) from bottom to top successively, the superjacent air space that is positioned at biofilter material layer (3) is a gas-liquid solids constituent abscission zone (1a), is connected with intake pump (9) by inlet channel in the bottom of anaerobic reactor (1); It is characterized in that: in described anaerobic reactor (1), be positioned between water distributor (6) and the biofilter material layer (3) 2～6 Zero-valent Iron packing layers (4) be set, form be positioned at the suspended sludge area (1c) between biofilter material floor (3) and the Zero-valent Iron packing layer (4) and be positioned at Zero-valent Iron packing layer (4) and water distributor (6) between sludge bulking district (1d); Described suspended sludge area (1c) is connected to the inlet channel of anaerobic reactor (1) bottom through circulating line (12) and recycle pump (13).

2. according to the described anaerobic built-in zero-valent iron reactor of claim 1, it is characterized in that: the lowest part of described Zero-valent Iron packing layer (4) is positioned at 1/2 place of anaerobic reactor (1) height, the height of Zero-valent Iron packing layer (4) is 5%～10% of anaerobic reactor (1) virtual height H, and the base plate (4a) and the leg of Zero-valent Iron packing layer (4) are provided with sieve aperture (4b); In Zero-valent Iron packing layer (4), be filled with the Zero-valent Iron granulated material of 2/3 height.

3. according to the described anaerobic built-in zero-valent iron reactor of claim 1, it is characterized in that: the height of described biofilter material layer (3) and triphase separator (2) is 5%～15% of anaerobic reactor (1) virtual height H.

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