Activated sludge screening process using a densificant

Abstract

The present application relates to a kind of activated sludge screening treatment method using densifier, specifically: sewage removes suspended pollutants, after degradation treatment and sludge-water separation, part or all of the activated sludge obtained enters activated sludge cyclone screening device and carries out cyclone separation, the activated sludge without cyclone separation is backflowed to biological reaction tank, after cyclone separation, the heavy activated sludge with better settling performance is backflowed to biological reaction tank, the remaining light activated sludge and densifier enter activated sludge mixing device and carry out mixing reaction, after two-stage screening device screening, the activated sludge with better settling performance is backflowed to biological reaction tank, part of the remaining activated sludge is backflowed to sewage pretreatment equipment after oxidation treatment, another enters remaining activated sludge treatment system and carries out dewatering disposal.The activated sludge screening treatment method using densifier of the present application can improve activated sludge concentration and settling performance, and improve the capacity of sewage treatment system.

Description

(I) TECHNICAL FIELD

[0001] The present application relates to a sludge treatment method, in particular to an activated sludge screening treatment method using a densifying agent. (II) BACKGROUND

[0002] Activated sludge process is a biological treatment technology for wastewater and sewage that has been inherited for hundreds of years. It mainly utilizes the adsorption and oxidation of organic matter by the microbial community on the activated sludge, mainly consisting of zooglea, to decompose and remove organic pollutants in wastewater. The quality and efficiency of activated sludge directly affect the capacity and effluent level of wastewater treatment. With the acceleration of urbanization and the continuous improvement of environmental protection requirements, the wastewater treatment capacity and effluent standards of wastewater treatment plants are increasing, and most wastewater treatment plants are facing challenges in land expansion, investment, operating costs, and stable compliance.

[0003] Current activated sludge improvement technologies at home and abroad mainly focus on the cultivation of functional bacteria in activated sludge, granular activated sludge cultivation, and biological carriers, with a focus on granular activated sludge cultivation and biological carrier addition. One direction is to create granular activated sludge through specific equipment and processes, and the other direction is to add carriers in the biochemical reaction tank, such as moving bed biofilm reactors (MBBR) and powder carrier fluidized bed reactors. The latter improves the activated sludge concentration in the biochemical tank by adding a large number of porous media carriers in the reaction tank.

[0004] Existing granular activated sludge methods usually rely on specific process equipment and fillers to inoculate granular activated sludge directly into the biochemical reactor. To promote the production of granular activated sludge, calcium ions are also added to the reactor to promote the formation of granular activated sludge, or a short-term sedimentation method is used to promote the formation of granular activated sludge. The equipment investment is high, the process is relatively complex, and the resistance to load impact is low. The implementation process has a significant impact on the existing wastewater treatment main process, and usually requires water shutdown construction. For example, a 20,000-ton wastewater treatment plant uses granular activated sludge method for upgrading and reconstruction, with a total investment of 30 million yuan, of which the investment in granular activated sludge technology equipment is nearly 20 million yuan.

[0005] Existing biological carrier addition methods use magnetic powder carriers, powdered activated carbon, and other carriers, which are generally added to the overall influent and biological reaction tank. This method has the problems of large carrier addition amount, relatively high investment, easy reaction tank carrier accumulation, and high carrier loss rate. At the same time, the implementation also causes significant disturbance to the main process of wastewater treatment. (III) SUMMARY

[0006] The technical problem solved by the present application is to provide an activated sludge screening treatment method using a densifying agent, which can effectively improve the SVI (sludge volume index) of a sewage treatment system, improve the return activated sludge concentration, the activated sludge concentration in a biological reaction tank and the activated sludge settling performance, effectively reduce the sludge treatment capacity, improve the capacity and efficiency of the sewage treatment system, reduce energy consumption and save investment cost.

[0007] The technical scheme of the present application is as follows:

[0008] An activated sludge screening treatment method using a densifying agent comprises the following steps:

[0009] Step 1: first, the sewage enters a sewage pretreatment device to remove suspended pollutants in the sewage, and then enters a biological reaction tank; after the mixed sewage enters the biological reaction tank, a large number of microorganisms in the activated sludge absorb and degrade organic pollutants; the activated sludge concentration in the conventional biological reaction tank is 3500-4500 mg / L;

[0010] Step 2: the sewage treated by degradation in the biological reaction tank enters a secondary sedimentation tank for sludge-water separation, and the obtained clear water is discharged to a river after disinfection; the activated sludge concentration at the bottom of the secondary sedimentation tank is generally 6000-8500 mg / L, and part or all of the activated sludge obtained at the bottom of the secondary sedimentation tank enters an activated sludge cyclone screening device for cyclone separation; the activated sludge not entering the activated sludge cyclone screening device is returned to the biological reaction tank as return activated sludge, thereby ensuring the activated sludge concentration in the biological reaction tank;

[0011] Step 3: the heavy activated sludge with good settling performance discharged from the lower port of the activated sludge cyclone screening device is returned to the biological reaction tank as return activated sludge, and this part of activated sludge includes granular activated sludge and flocculent activated sludge; the light activated sludge with poor settling performance and the densifying agent discharged from the upper port of the activated sludge cyclone screening device enter an activated sludge mixing device together;

[0012] Step 4: the light activated sludge and the densifying agent are fully mixed and reacted in the activated sludge mixing device, the mixing and reaction time is 5-30 minutes, the filamentous bacteria and the densifying agent are fully combined by means of hydraulic action, the activated sludge is modified by the densifying agent, the settling performance of the activated sludge is improved, and the light activated sludge after the mixing and reaction enters an activated sludge secondary screening device;

[0013] The activated sludge secondary screening device is composed of an activated sludge diversion area, an activated sludge agitator and a partition plate, and is a gravity screening device by means of hydraulic agitation disturbance;

[0014] Step 5, the mixed light-weight activated sludge after reaction enters the activated sludge secondary screening device, and is preliminarily divided by the partition plate; the activated sludge with good settling performance enters the activated sludge stirring area through the lower part, and the activated sludge with poor settling performance enters through the upper part of the partition plate overflow; the activated sludge entering through the lower part is screened under the action of the activated sludge stirrer, and the stirring speed of the activated sludge stirrer in the pool is adjusted to realize the circulating stirring, cut the suspended solids in the water, re-form the large flocculation body easy to settle, and the screening rate is improved by the setting of the middle partition plate; after the secondary screening, the activated sludge meeting the screening requirements, i.e. the recombined dense improved activated sludge with good settling performance, sinks to the bottom of the pool as the return activated sludge, the concentration of the return activated sludge is increased from 6000-8000 mg / L in the traditional way to 10000-13000 mg / L, and the light-weight activated sludge after the mixing reaction and with poor adsorption and settling performance after the preliminary division and the division by the activated sludge stirrer and the partition plate is used as the residual activated sludge (also called aged activated sludge);

[0015] The activated sludge discharged from the lower part of the activated sludge secondary screening device is returned to the biological reaction tank, and is mixed with the sewage treated by the sewage pretreatment equipment in step 1; the activated sludge concentration in the biological reaction tank is increased from 3500-5000 mg / L to 6500-10000 mg / L; and the residual activated sludge discharged from the upper part of the activated sludge secondary screening device enters the residual activated sludge treatment system for dewatering treatment.

[0016] In step 5, part of the residual activated sludge discharged from the upper part of the activated sludge secondary screening device enters the residual activated sludge treatment system for dewatering treatment; another part of the residual activated sludge discharged from the upper part of the activated sludge secondary screening device enters the activated sludge oxidation device for oxidation treatment, and then is returned to the sewage pretreatment equipment to provide a carbon source for the biological reaction tank; the activated sludge oxidation device is an optional device, and the production of the residual activated sludge can be appropriately controlled.

[0017] The activated sludge cyclone screening device contains at least one set of hydrocyclone separator, and the concentration of the return activated sludge is generally between 1.004-1.006 g / cm 3 ; in combination with the laboratory optimization test, the hydrocyclone separator is selected as a small-cone-angle long-cone-cylinder hydrocyclone separator, the daily treatment scale of a single device is 400-2000 tons, the cone angle is 1-3°, the cylinder diameter is 100-200 mm, the cylinder length is 500-1000 mm, the overflow port hole diameter is 6-35 mm, the underflow port hole diameter is 6-20 mm, the overflow activated sludge density of the activated sludge cyclone screening device is required to be between 1.004-1.02 g / cm 3 , the heavy activated sludge density in the underflow area is between 1.06-1.3 g / cm 3 , and the underflow flocculation body density is between 1.05-1.10 g / cm3 The active sludge mixing device is a long-flow channel self-rotating flow stirring mixing device or a multi-stage stirring device with not less than two stages, the light-weight active sludge is stirred with the densifying agent in the active sludge mixing device, and the stirring power is 3-4 W / m 3 The active sludge secondary screening device is a QDE type active sludge stirrer.

[0018] The multi-stage stirring device is a three-stage series mixing reaction tank, the tank body is made of reinforced concrete structure or steel structure, the light-weight active sludge is subjected to hydraulic mixing reaction in the three-stage series mixing reaction tank for a mixing time of 5-30 minutes, and then enters the active sludge secondary screening device, each mixing reaction tank is provided with a double-stage six-blade stirrer, or other stirrers can be used.

[0019] In the second step, the part of the active sludge obtained at the bottom of the secondary sedimentation tank accounts for A% of the total active sludge, A% is greater than or equal to 15% and less than 100%; in the third step, the dosing amount of the densifying agent is generally controlled to be between 4-20 mg per 1 liter of light-weight active sludge, and the specific amount can be determined through on-site beaker stirring test.

[0020] In the fourth step, the densifying agent enters the active sludge mixing device through the active sludge densifying agent dosing device, the active sludge densifying agent dosing device is a mature powder filler dosing device on the market, generally using a vibration motor to drive a powder vibration oscillator to make the powder flow smoothly to a quantitative feeder, and using a variable frequency screw conveyor to uniformly and quantitatively feed the powder into the stirring tank.

[0021] The active sludge oxidation device has a tank body made of reinforced concrete structure, and the main equipment is an ozone generator or an electromagnetic wall breaking device, and the ozone dosing specification is 40-60 mg / L.

[0022] The densifying agent is a mixed agent composed of various powdered porous medium materials, and the densifying agent is prepared from 55-75 parts of diatomite powder, 10-25 parts of perlite powder, 3-8 parts of sodium silicate powder and 2-5 parts of iron sulfide powder, according to the proportion, various raw materials are weighed and mixed uniformly to obtain the densifying agent.

[0023] The particle size of the diatomite powder is 200-400 mesh, the particle size of the perlite powder is 200-400 mesh, and the particle size of the iron sulfide powder is 300-400 mesh; the content of silicon dioxide in the diatomite powder is not less than 80%, the purity of the sodium silicate powder is not less than 85%, and the purity of the iron sulfide powder is not less than 85%.

[0024] The densifying agent can also be powdered activated carbon with a particle size of 300-400 mesh, and the dosing amount of the powdered activated carbon is 1%-8% of the dosing amount of the densifying agent of the above formula under the same dosing amount of the densifying agent.

[0025] Advantages of the present application:

[0026] 1. The activated sludge screening treatment method using the densifier of the present application is not limited to the cultivation of granular activated sludge, and focuses on the adsorption and settling performance of activated sludge. By performing cyclone screening on activated sludge, fully mixing and reacting the light activated sludge with the densifier, and secondary screening of activated sludge, the activated sludge with good settling performance is returned to the biological reaction tank, which can effectively improve the concentration and settling performance of activated sludge in the biological reaction tank of the newly built and existing sewage treatment system, effectively improve the SVI of the sewage treatment system, and stabilize the SVI value at about 80-120. The concentration of the returned activated sludge is increased from the traditional 6000-8000 mg / L to 10000-13000 mg / L, and the concentration of activated sludge in the biological reaction tank is increased from 3500-5000 mg / L to 6500-10000 mg / L. On the basis of ensuring the effluent quality, the sewage treatment capacity is increased by 15%-40%, and the impact resistance of the sewage treatment system is improved.

[0027] 2. The activated sludge screening treatment method using the densifier of the present application, the activated sludge enters the activated sludge cyclone screening device for cyclone separation, and part of the heavy activated sludge with good settling performance is directly returned to the biological reaction tank, which effectively reduces the sludge treatment capacity, improves the efficiency of the sewage treatment system, and reduces the load of the sewage treatment equipment and energy consumption. When the concentration of activated sludge is increased, the concentration of microorganisms in activated sludge can be increased, the biological treatment process is stable and reliable, and the efficiency of biological treatment is improved.

[0028] 3. The present application focuses on "sludge road", that is, the settling performance of activated sludge and the return to the biological reaction tank. The process route is relatively simple, the required equipment is basically general equipment, no additional land is occupied, and the engineering investment cost can be reduced.

[0029] 4. In the present application, the light activated sludge and the densifier are fully mixed and reacted in the activated sludge mixing device. The densifier directly acts on the light activated sludge, which is highly targeted and has a concentrated range of action. The dosage of the reagent is relatively small. The amount of residual activated sludge after secondary screening of activated sludge is about 10%-25% of the amount of returned activated sludge, which is about 1%-8% of the influent amount of the sewage treatment system. Under the same dosage of the densifier, the dosage of the densifier of the present application is 1%-8% of the dosage of the powdered activated carbon. Moreover, when the activated sludge system is stable, the dosage of the densifier can be reduced or even eliminated, which is very cost-effective.

[0030] 5、In the upgrading and reconstruction of existing sewage treatment project, the granular activated sludge method has a long water stop construction period, which will have a great impact on the existing sewage treatment, the biological carrier adding method will have a great disturbance to the main process of sewage treatment, the activated sludge screening treatment method using the densifier of the present application can realize non-water stop, non-reduction of standard, non-influence on the normal production of the existing water plant, small disturbance to the existing process, and can effectively solve the problems of large biological carrier adding amount, carrier accumulation in the reaction tank and high carrier loss rate. (Four), brief description of the drawings:

[0031] Figure 1 The activated sludge screening treatment method using the densifier of the present application Figure 1

[0032] Figure 2 The activated sludge screening treatment method using the densifier of the present application Figure 2 (Five), specific implementation:

[0033] Example one: an activated sludge screening treatment method using a densifier, see Figure 1 , containing the following steps:

[0034] Step 1, first make the sewage enter the sewage pretreatment equipment 1, remove the suspended pollutants in the sewage, and then enter the biological reaction tank 2; after the mixed sewage enters the biological reaction tank 2, a large number of microorganisms in the activated sludge absorb and degrade organic pollutants; the activated sludge concentration in the conventional biological reaction tank 2 is 3500-4500 mg / L;

[0035] Step 2, make the sewage treated in the biological reaction tank 2 enter the secondary sedimentation tank 3 for mud-water separation, and the clear water obtained after separation is discharged to the river 4 after disinfection, the activated sludge concentration at the bottom of the secondary sedimentation tank 3 is generally 6000-8500 mg / L, part of the activated sludge obtained at the bottom of the secondary sedimentation tank 3 enters the activated sludge cyclone screening device 5 for cyclone separation, and the activated sludge not entering the activated sludge cyclone screening device 5 is returned to the biological reaction tank 2 as return activated sludge, to ensure the activated sludge concentration in the biological reaction tank 2;

[0036] Step 3, the heavy activated sludge with good settling performance discharged from the lower port 6 of the activated sludge cyclone screening device 5 is returned to the biological reaction tank 2 as return activated sludge, and this part of activated sludge includes granular activated sludge and flocculent activated sludge, and the light activated sludge with poor settling performance and the densifier discharged from the upper port 7 of the activated sludge cyclone screening device 5 enter the activated sludge mixing device 8 together;

[0037] ​​Step 4: The light-weighted activated sludge is mixed with the densifier in the activated sludge mixing device 8 for 5-30 minutes, so that the filamentous bacteria and the densifier are combined by the hydraulic action, and the activated sludge is modified by the densifier, so that the settling performance of the activated sludge is improved. The light-weighted activated sludge after the mixing reaction enters the activated sludge secondary screening device 9 again.

[0038] The activated sludge secondary screening device 9 is composed of an activated sludge diversion area 10, an activated sludge agitator 11 and a partition 12, and is a gravity screening device through the disturbance caused by the hydraulic agitation.

[0039] Step 5: After the light-weighted activated sludge after the mixing reaction enters the activated sludge secondary screening device 9, the activated sludge is preliminarily diverted by the partition 12. The activated sludge with good settling performance enters the activated sludge stirring area through the lower part, and the activated sludge with poor settling performance enters from the upper part through overflow. The activated sludge entering through the lower part is screened under the action of the activated sludge agitator 11. The circulating stirring is realized by adjusting the rotating speed of the activated sludge agitator 11 in the pool, the suspended solids in the water are sheared, and large flocculation bodies easy to settle are reformed. The screening rate is improved by the setting of the middle partition 12. After the secondary screening, the activated sludge that meets the screening requirements, i.e. the recombined and densified improved activated sludge with good settling performance, sinks to the bottom of the pool as the return activated sludge. The concentration of the return activated sludge is increased from 6000-8000 mg / L in the traditional process to 10000-13000 mg / L. The light-weighted activated sludge after the mixing reaction with poor adsorption and settling performance is preliminarily diverted and then diverted by the activated sludge agitator 11 and the partition 12, and is used as the residual activated sludge (also called aged activated sludge).

[0040] The activated sludge discharged from the lower part 17 of the activated sludge secondary screening device 9 is returned to the biological reaction tank 2 and mixed with the sewage treated by the sewage pretreatment device 1 in step 1. The concentration of the activated sludge in the biological reaction tank 2 is increased from 3500-5000 mg / L to 6500-10000 mg / L. The residual activated sludge discharged from the upper part 18 of the activated sludge secondary screening device 9 enters the residual activated sludge treatment system 16 for dewatering treatment.

[0041] In step 5: part of the residual activated sludge discharged from the upper part 18 of the activated sludge secondary screening device 9 enters the residual activated sludge treatment system 16 for dewatering treatment; another part of the residual activated sludge discharged from the upper part 18 of the activated sludge secondary screening device 9 enters the activated sludge oxidation device 15 for oxidation treatment, and then is returned to the sewage pretreatment device 1 to provide a carbon source for the biological reaction tank 2. The activated sludge oxidation device 15 can appropriately control the yield of the residual activated sludge.

[0042] The activated sludge cyclone screening device 5 contains one set of hydrocyclone separator, aiming at the backflow activated sludge concentration generally between 1.004-1.006 g / cm 3 3, combined with laboratory optimization test, the hydrocyclone separator selects a small cone angle long cone cylinder hydrocyclone separator, single device daily processing scale 400-2000 tons, cone angle 1-3°, cylinder diameter 100-200 mm, cylinder length 500-1000 mm, overflow hole diameter 6-35 mm, underflow hole diameter 6-20 mm, the activated sludge cyclone screening device 5 requires the overflow activated sludge density to be low level between 1.004-1.02 g / cm 3 3, the heavy activated sludge density in the underflow zone is between 1.06-1.3 g / cm 3 3, and the underflow floc density is between 1.05-1.10 g / cm 3 3; the activated sludge mixing device 8 is a three-stage series mixing reaction tank, the light activated sludge and the densifying agent are stirred in the activated sludge mixing device 8, and the stirring power is 3-4 W / m 3 3; the activated sludge mixing device 8 is a three-stage series mixing reaction tank, the light activated sludge and the densifying agent are stirred in the activated sludge mixing device 8, and the stirring power is 3-4 W / m

[0043] The three-stage series mixing reaction tank adopts reinforced concrete structure, the light activated sludge is subjected to hydraulic mixing reaction in the three-stage series mixing reaction tank for 5-30 minutes, and then enters the activated sludge secondary screening device 9, and each mixing reaction tank is provided with a double-stage six-blade stirrer 13.

[0044] In the second step, the activated sludge obtained at the bottom of the secondary sedimentation tank 3 accounts for 15% of the total activated sludge in percentage by weight;

[0045] In the third step, the dosing amount of the densifying agent is 4 mg per 1 liter of light activated sludge.

[0046] In the fourth step, the densifying agent enters the activated sludge mixing device 8 through the activated sludge densifying agent dosing device 14, the activated sludge densifying agent dosing device 14 is a powder filler dosing device, the powder is smoothly flowed to the quantitative feeder by means of the unloading oscillator driven by the oscillation motor, and the powder is uniformly and quantitatively fed into the stirring tank by the variable frequency screw conveyor.

[0047] The activated sludge oxidation device 15 is an ozone generator, and the ozone dosing specification is 40-60 mg / L.

[0048] The densifying agent is a mixed agent composed of various powdered porous medium materials, and the densifying agent is prepared from 70 parts of diatomite powder, 20 parts of perlite powder, 5 parts of sodium silicate powder and 5 parts of iron sulfide powder in weight parts, the various raw materials are weighed according to the proportion, and all the raw materials are uniformly mixed to obtain the densifying agent.

[0049] The particle size of diatomite powder is 300 mesh, the particle size of perlite powder is 300 mesh, and the particle size of iron sulfide powder is 350 mesh; the content of silicon dioxide in diatomite powder is 85%, the purity of sodium silicate powder is 90%, and the purity of iron sulfide powder is 90%.

[0050] Example two: an activated sludge screening treatment method using a densifier, see Figure 1 The same parts as in example one will not be repeated, and the differences are:

[0051] In step 2: all of the activated sludge obtained at the bottom of the secondary sedimentation tank 3 enters the activated sludge cyclone screening device 5 for cyclone separation;

[0052] In step 3: the dosage of the densifier in each 1 liter of light activated sludge is 20 mg;

[0053] The densifier is prepared from raw materials diatomite powder 75 parts, perlite powder 10 parts, sodium silicate powder 3 parts and iron sulfide powder 4 parts, and various raw materials are weighed according to the proportion, and then all the raw materials are mixed uniformly to obtain the densifier.

[0054] The particle size of diatomite powder is 400 mesh, the particle size of perlite powder is 200 mesh, and the particle size of iron sulfide powder is 300 mesh; the content of silicon dioxide in diatomite powder is 80%, the purity of sodium silicate powder is 85%, and the purity of iron sulfide powder is 85%.

[0055] Example three: an activated sludge screening treatment method using a densifier, see Figure 2 The same parts as in example one will not be repeated, and the differences are:

[0056] In step 2: according to the weight percentage, part of the activated sludge obtained at the bottom of the secondary sedimentation tank 3 accounts for 35% of the total activated sludge, which enters the activated sludge cyclone screening device 5 for cyclone separation;

[0057] In step 3: the dosage of the densifier in each 1 liter of light activated sludge is 8 mg;

[0058] In step 5: make all the remaining activated sludge discharged from the upper port 18 of the activated sludge secondary screening device 9 enter the remaining activated sludge treatment system 16 for dewatering disposal;

[0059] The densifier is prepared from raw materials diatomite powder 55 parts, perlite powder 25 parts, sodium silicate powder 8 parts and iron sulfide powder 2 parts, and various raw materials are weighed according to the proportion, and then all the raw materials are mixed uniformly to obtain the densifier.

[0060] The particle size of diatomite powder is 200 mesh, the particle size of perlite powder is 400 mesh, and the particle size of iron sulfide powder is 400 mesh; the content of silicon dioxide in diatomite powder is 90%, the purity of sodium silicate powder is 93%, and the purity of iron sulfide powder is 94%.

[0061] Example four: an activated sludge screening treatment method using a densifier, see Figure 1 The same part as example one, not described again, the difference is:

[0062] In the second step: according to the weight percentage, the part of activated sludge obtained at the bottom of the secondary sedimentation tank 3 accounts for 60% of the total activated sludge, which enters the activated sludge cyclone screening device 5 for cyclone separation;

[0063] In the third step: the dosage of the densifier is 12 mg per 1 liter of light activated sludge;

[0064] The activated sludge oxidation device 15 is an electromagnetic wall breaking device;

[0065] The densifier is prepared by raw materials diatomite powder 61 parts, perlite powder 14 parts, sodium silicate powder 7 parts and iron sulfide powder 3 parts, and various raw materials are weighed according to the ratio, and then all the raw materials are mixed uniformly to obtain the densifier.

[0066] The particle size of diatomite powder is 260 mesh, the particle size of perlite powder is 240 mesh, and the particle size of iron sulfide powder is 380 mesh; the content of silicon dioxide in diatomite powder is 94%, the purity of sodium silicate powder is 98%, and the purity of iron sulfide powder is 88%.

[0067] Example five: an activated sludge screening treatment method using a densifier, see Figure 2 The same part as example one, not described again, the difference is:

[0068] In the second step: according to the weight percentage, the part of activated sludge obtained at the bottom of the secondary sedimentation tank 3 accounts for 60% of the total activated sludge, which enters the activated sludge cyclone screening device 5 for cyclone separation;

[0069] In the third step: the dosage of the densifier is 12 mg per 1 liter of light activated sludge;

[0070] In the fifth step: all the remaining activated sludge discharged from the upper port 18 of the activated sludge secondary screening device 9 enters the remaining activated sludge treatment system 16 for dewatering treatment;

[0071] The densifier is prepared by raw materials diatomite powder 67 parts, perlite powder 22 parts, sodium silicate powder 6 parts and iron sulfide powder 4 parts, and various raw materials are weighed according to the ratio, and then all the raw materials are mixed uniformly to obtain the densifier.

[0072] The particle size of diatomite powder is 340 mesh, the particle size of perlite powder is 350 mesh, and the particle size of iron sulfide powder is 330 mesh; the content of silicon dioxide in diatomite powder is 82%, the purity of sodium silicate powder is 87%, and the purity of iron sulfide powder is 97%.

[0073] Example six: an activated sludge screening treatment method using a densifier, see Figure 1 The same parts as in example one are not repeated, and the differences are:

[0074] In the second step: according to the weight percentage, the part of the activated sludge obtained at the bottom of the secondary sedimentation tank 3 accounts for 93% of the total activated sludge, which enters the activated sludge cyclone screening device 5 for cyclone separation;

[0075] In the third step: the dosage of the densifier is 10 mg per 1 liter of light activated sludge;

[0076] The densifier is powdered activated carbon with a particle size of 300 mesh.

Claims

1. A method for screening and treating activated sludge using a densifying agent. Its characteristics include the following steps: Step 1: First, the wastewater enters the wastewater pretreatment equipment to remove suspended pollutants from the wastewater, and then it enters the biological reactor. Step 2: The wastewater after degradation treatment in the biological reactor enters the secondary sedimentation tank for sludge-water separation. The clear water obtained after separation is disinfected and discharged into the river. Part or all of the activated sludge obtained at the bottom of the secondary sedimentation tank enters the activated sludge cyclone screen device for cyclone separation. The activated sludge that does not enter the activated sludge cyclone screen device is returned to the biological reactor. Step 3: The heavy activated sludge discharged from the lower port of the activated sludge cyclone screener is returned to the biological reactor, while the light activated sludge discharged from the upper port of the activated sludge cyclone screener and the densifying agent enter the activated sludge mixing device together. The densifying agent, expressed in parts by weight, is prepared from 55-75 parts of diatomaceous earth powder, 10-25 parts of perlite powder, 3-8 parts of sodium silicate powder and 2-5 parts of iron sulfide powder. The various raw materials are weighed according to the proportions and then mixed evenly to obtain the densifying agent. Step 4: Mix the light activated sludge and the densifying agent in the activated sludge mixing device for 5 to 30 minutes. After the mixing reaction, the light activated sludge enters the activated sludge secondary screening device. Step 5: Return the activated sludge discharged from the lower part of the activated sludge secondary screening device to the biological reactor, and allow a portion of the remaining activated sludge discharged from the upper port of the activated sludge secondary screening device to enter the remaining activated sludge treatment system for dewatering. Another portion of the remaining activated sludge discharged from the upper port of the activated sludge secondary screening device enters the activated sludge oxidation device for oxidation treatment, and then flows back to the wastewater pretreatment equipment; The activated sludge oxidation device is either an ozone generator or an electromagnetic cell disruptor.

2. The activated sludge screening and treatment method using a densifying agent according to claim 1, characterized in that: The activated sludge hydrocyclone screening device includes at least one set of hydrocyclone separators; the activated sludge mixing device is a long-channel self-rotating mixing device or a multi-stage mixing device with no less than two stages, wherein the light activated sludge and the thickening agent are mixed in the activated sludge mixing device, and the mixing power is 3~ 4W / m3 ; The secondary screening device for activated sludge is a QDE type activated sludge mixer.

3. The activated sludge screening and treatment method using a densifying agent according to claim 2, characterized in that: The multi-stage stirring device is a three-stage series mixing reaction tank. After 5 to 30 minutes of hydraulic mixing reaction in the three-stage series mixing reaction tank, the light activated sludge enters the activated sludge secondary screening device.

4. The activated sludge screening and treatment method using a densifying agent according to claim 1, characterized in that: In step 2: by weight percentage, the activated sludge obtained from the bottom of the secondary sedimentation tank accounts for A% of the total activated sludge, which is greater than or equal to 15% and less than 100%; In step 3: the amount of densifying agent added to each liter of light activated sludge is controlled between 4 and 20 mg.

5. The activated sludge screening and treatment method using a densifying agent according to claim 1, characterized in that: In step 4: the densifying agent enters the activated sludge mixing device through the activated sludge densifying agent dosing device, which is a powder filler dosing device.

6. The activated sludge screening and treatment method using a densifying agent according to claim 1, characterized in that: The diatomaceous earth powder has a particle size of 200-400 mesh, the perlite powder has a particle size of 200-400 mesh, and the iron sulfide powder has a particle size of 300-400 mesh; the silica content in the diatomaceous earth powder is not less than 80%, the purity of the sodium silicate powder is not less than 85%, and the purity of the iron sulfide powder is not less than 85%.

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