A sewage treatment method using compounded diatomite and CASS process

Abstract

The present application provides a sewage treatment method using compounded diatomite and CASS process, biomass raw materials prepared from the agricultural and forestry wastes as raw materials are mixed with diatomite, then subjected to programmed temperature heat treatment, the biomass raw materials are converted into biochar and loaded on the diatomite to obtain compounded diatomite, then the pretreated sewage, compounded diatomite and reflux sludge refluxed from the main reaction zone are subjected to microbial cultivation and domestication in the mixing tank, so that the sewage is treated by the microorganisms with high population concentration and diversified population loaded on the compounded diatomite, and the compounded diatomite is used as the carrier of the microorganisms in the CASS reaction tank, the range of pollutants treated by the CASS reaction tank is expanded, and the sewage treatment efficiency and nitrogen and phosphorus removal rate are greatly improved by the synergistic use of biochar and diatomite, and the removal effect of pollutants in the sewage is improved in a short hydraulic retention time.

Description

TECHNICAL FIELD

[0001] The present application relates to the sewage treatment technical field, and particularly relates to a sewage treatment method using compounded diatomite and CASS process. BACKGROUND

[0002] With the development of economy, the improvement of productivity and technical level, more and more sewage is discharged, which not only brings adverse effects on people's work, life and environment, but also directly harms human health. Therefore, exploring effective new sewage treatment technology has become an important research field of environmental protection.

[0003] At present, the traditional activated sludge method, oxidation ditch, SBR and the like are generally used in the sewage treatment process in China. These mature and effective treatment processes are widely used in various places. The above processes have the disadvantages of high energy consumption and high operation cost, and the sewage treatment efficiency and the nitrogen and phosphorus removal rate need to be improved. Therefore, it is an urgent technical problem to be solved in the prior art to provide a sewage treatment method with low cost, high sewage treatment efficiency and high nitrogen and phosphorus removal rate. SUMMARY

[0004] The present application aims to provide a sewage treatment method using compounded diatomite and CASS process. The method provided by the present application cooperatively uses compounded diatomite and CASS process, reduces the cost, and improves the sewage treatment efficiency and the nitrogen and phosphorus removal rate.

[0005] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0006] The present application provides a sewage treatment method using compounded diatomite and CASS process, which comprises that the pretreated sewage sequentially enters a mixing tank and a water inlet / aeration / backflow stage, a sedimentation stage and a drainage stage of a CASS reaction tank.

[0007] The CASS reaction tank comprises a biological selection zone and a main reaction zone.

[0008] The water inlet / aeration / backflow stage is provided with a mixing tank, and the pretreated sewage, compounded diatomite and backflow sludge backflowed from the main reaction zone are mixed in the mixing tank and then enter the biological selection zone.

[0009] The preparation method of the compounded diatomite comprises the following steps:

[0010] (1) pretreating agricultural and forestry waste to obtain biomass raw materials;

[0011] (2) mixing the biomass raw materials obtained in the step (1) and diatomite, and then performing programmed temperature heat treatment to obtain compounded diatomite;

[0012] (3) The compound diatomite is obtained by compounding the diatomite and the sewage treatment microorganism obtained in step (1).

[0013] Preferably, the ratio of the mass of the compound diatomite to the volume of the pretreated sewage is (0.3-6 g):1 L.

[0014] Preferably, the agricultural and forestry waste in step (1) includes any one or more of rice straw, rice husk, wood chips, tea leaves, Chinese medicine residue and nut shell.

[0015] Preferably, the pretreatment in step (1) includes impurity removal, first drying, crushing and sieving in sequence.

[0016] Preferably, the mass ratio of the biomass raw material to the diatomite in step (2) is (0.02-0.8):(2-6).

[0017] Preferably, the programmed temperature heating treatment in step (2) includes a first stage of heating from room temperature to 320-450℃ at a heating rate of 5-10℃ / min and holding for 40-60 min, and a second stage of heating from 320-450℃ to 550-650℃ at a heating rate of 1-5℃ / min and holding for 80-200 min.

[0018] Preferably, after the programmed temperature heating treatment in step (2), the product of the programmed temperature heating treatment is sequentially subjected to cooling, grinding, acid immersion activation, washing and second drying to obtain the compound diatomite.

[0019] The present application provides a sewage treatment method using compound diatomite and CASS process, which includes the following steps: pretreated sewage enters a water inlet / aeration / return stage of a CASS reaction tank, a sedimentation stage and a drainage stage; the CASS reaction tank includes a biological selection zone and a main reaction zone; the water inlet / aeration / return stage is provided with a mixing tank, and the pretreated sewage, the compound diatomite and the return sludge from the main reaction zone are subjected to microbial cultivation and domestication in the mixing tank and then enter the biological selection zone; the compound diatomite is prepared by the following steps: first, pretreating agricultural and forestry waste to obtain a biomass raw material, then mixing the biomass raw material with diatomite and performing programmed temperature heating treatment to obtain the compound diatomite.

[0020] This invention uses agricultural and forestry waste as raw materials to prepare biomass raw materials. These biomass raw materials are then mixed with diatomaceous earth and subjected to programmed temperature heating to convert the biomass raw materials into biochar, which is then loaded onto the diatomaceous earth to obtain a composite diatomaceous earth with well-developed pores and a high specific surface area. The pretreated wastewater, the composite diatomaceous earth, and the returned sludge from the main reaction zone are then cultured and acclimated to microorganisms in a mixing tank. This allows for the loading of wastewater treatment microorganisms onto the composite diatomaceous earth, which then enters the biological selection zone. The high concentration and diverse population of microorganisms loaded on the composite diatomaceous earth are used for wastewater treatment. Simultaneously, the biochar serves as a carrier for microorganisms in the CASS reactor, expanding the range of pollutants that the CASS reactor can treat. Furthermore, the synergistic use of biochar and diatomaceous earth significantly improves wastewater treatment efficiency and nitrogen and phosphorus removal rates, achieving higher COD levels in wastewater within a shorter hydraulic retention time. cr The method provided by this invention effectively removes pollutants such as COD5, SS, NH4-N, TN, and TP. It integrates adsorption, coagulation, filtration, and biochemical processes into a complete and practical wastewater treatment unit, shortening the hydraulic retention time, reducing the volume of the biological reactor, and improving treatment efficiency. Furthermore, the equipment requires minimal space, has a wide range of raw material sources, is low-cost, and provides excellent treatment results. It is also highly applicable, simple to operate, and capable of continuous treatment, suitable for various industrial and municipal wastewater treatment applications. The results of the embodiments show that, using the method provided in Examples 1-3 of this invention, within a shorter hydraulic retention time, the COD5 in the treated municipal wastewater is significantly reduced. cr The removal rates are as high as 98.7%, BOD5 removal rate as high as 96.1%, SS removal rate as high as 95.0%, NH4-N removal rate as high as 98.6%, TN removal rate as high as 94.3%, and TP removal rate as high as 90.5%. Attached Figure Description

[0021] Figure 1 This is a top view schematic diagram of the process equipment used in the wastewater treatment method utilizing compound diatomaceous earth and CASS process in this invention;

[0022] Attached diagrams: 1. CASS reactor; 2. Biological selection zone; 3. Main reaction zone; 4. Mixing tank; 5. Disinfection tank; 6. Sludge treatment equipment. Detailed Implementation

[0023] This invention provides a wastewater treatment method using compound diatomaceous earth and CASS process, including a pre-treated wastewater sequentially entering a mixing tank and a CASS reaction tank in an influent / aeration / recirculation stage, a sedimentation stage, and a drainage stage;

[0024] The CASS reactor includes a biological selection zone and a main reaction zone;

[0025] The water inlet / aeration / return stage sets a mixing tank, and the pretreated sewage, compounded diatomite and return sludge from the main reaction zone are mixed in the mixing tank after microbial cultivation and domestication, and then enter the biological selection zone.

[0026] In the present application, the pretreated sewage is preferably obtained by sequentially treating industrial sewage and / or municipal sewage by coarse grid filtration, fine grid filtration and sand removal by sand grit chamber.

[0027] In the present application, the mass ratio of the compounded diatomite to the volume of the pretreated sewage is preferably (0.3-6 g):1 L, and more preferably (0.35-5 g):1 L. The present application controls the mass ratio of the compounded diatomite to the volume of the pretreated sewage in the above range, so as to facilitate the full play of the compounded diatomite in sewage treatment and improve the sewage treatment efficiency.

[0028] The present application does not have special limitations on the way of microbial cultivation and domestication, and any microbial cultivation and domestication technical solution known in the art can be used to achieve the purpose of loading sewage treatment microorganisms on the compounded diatomite.

[0029] The present application loads sewage treatment microorganisms on the compounded diatomite by treating the pretreated sewage, compounded diatomite and return sludge from the main reaction zone in the mixing tank after microbial cultivation and domestication, and then entering the biological selection zone. The pretreated sewage, compounded diatomite and return sludge from the main reaction zone are loaded with sewage treatment microorganisms on the compounded diatomite, and then enter the biological selection zone. The sewage treatment microorganisms loaded on the compounded diatomite have high population concentration and population diversity, and can be used for sewage treatment. At the same time, the compounded diatomite can be used as a carrier of microorganisms in the CASS reaction tank, which expands the range of pollutants treated by the CASS reaction tank. The synergistic use of biochar and diatomite greatly improves the sewage treatment efficiency and nitrogen and phosphorus removal rate, and improves the removal effect of COD cr , BOD5, SS, NH4-N, TN, TP and other pollutants in sewage in a short hydraulic retention time.

[0030] In the present application, the preparation method of the compounded diatomite comprises the following steps:

[0031] (1) pretreating agricultural and forestry waste to obtain biomass raw material;

[0032] (2) mixing the biomass raw material obtained in step (1) and diatomite, and then performing programmed temperature heat treatment to obtain compounded diatomite.

[0033] In the present application, agricultural and forestry waste is pretreated to obtain biomass raw material.

[0034] In the present application, the agricultural and forestry wastes preferably include any one or more of rice straw, rice hull, wood chips, tea leaves, Chinese medicine residue, and nut shell. The present application uses agricultural and forestry wastes as raw materials to prepare biomass raw materials, and then mixes the biomass raw materials with diatomite, and then performs programmed temperature heat treatment, so that the biomass raw materials are converted into biochar and loaded on diatomite to obtain compounded diatomite.

[0035] In the present application, the pretreatment includes impurity removal, first drying, crushing, and sieving in sequence. The present application does not have special limitations on the temperature and time of the first drying, and only the purpose of removing water is achieved. The present application converts the agricultural and forestry wastes into powder or granular biomass raw materials through pretreatment, which is beneficial to the subsequent preparation of compounded diatomite with developed pores and high specific surface area.

[0036] After obtaining the biomass raw materials, the present application mixes the biomass raw materials with diatomite, and then performs programmed temperature heat treatment to obtain compounded diatomite.

[0037] In the present application, the mass ratio of the biomass raw materials to diatomite is preferably (0.02-0.8):(2-6), and more preferably (0.05-0.5):(3-5). The present application controls the mass ratio of the biomass raw materials to diatomite in the above range to adjust the content of biochar in the subsequently prepared compounded diatomite, so as to obtain compounded diatomite with developed pores and high specific surface area, and improve the wastewater treatment efficiency thereof.

[0038] In the present application, the programmed temperature heat treatment preferably includes a first stage of heating from room temperature to 320-450℃ at a heating rate of 5-10℃ / min, and holding for 40-60min; and a second stage of heating from 320-450℃ to 550-650℃ at a heating rate of 1-5℃ / min, and holding for 80-200min, and more preferably includes a first stage of heating from room temperature to 350-430℃ at a heating rate of 6-9℃ / min, and holding for 50-55min; and a second stage of heating from 350-430℃ to 580-630℃ at a heating rate of 2-4℃ / min, and holding for 100-180min. The present application promotes the complete conversion of the biomass raw materials into biochar with developed pores and high specific surface area through programmed temperature heat treatment, and loads the biochar on diatomite, and at the same time activates diatomite, so as to finally obtain compounded diatomite.

[0039] After the programmed temperature heat treatment, the present application preferably sequentially performs cooling, grinding, acid immersion activation, washing, and second drying on the product of the programmed temperature heat treatment to obtain compounded diatomite.

[0040] The present application obtains the compound diatomite with high specific surface area by adjusting the particle size through grinding. In the present application, the acid used for the acid immersion activation is preferably hydrochloric acid or sulfuric acid. The present application removes the impurities on the surface of the product of the programmed temperature heat treatment through the acid immersion activation and washing, which is beneficial to obtain the compound diatomite with high specific surface area.

[0041] The technical solutions in the present application will be described clearly and completely below in combination with the embodiments in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0042] Figure 1 The top view schematic diagram of the process equipment used for the sewage treatment method using the compound diatomite and the CASS process in the present application is specifically as follows: the pretreated sewage, the added compound diatomite and the backflow sludge backflowed from the main reaction zone are first introduced into the biological selection zone 2 of the CASS reaction tank 1 after the microbial cultivation domestication in the mixing tank 4, and then introduced into the main reaction zone 3. The water after the sewage treatment is discharged after the disinfection treatment in the disinfection tank 5, and the sludge at the bottom of the main reaction zone is formed into a sludge cake after the sludge treatment in the sludge treatment equipment 6 and then is transported out.

[0043] Example 1

[0044] The sewage treatment method using the compound diatomite and the CASS process is as follows: Figure 1 The CASS reaction tank is divided into the biological selection zone and the main reaction zone according to the top view schematic diagram, the effective volume of the main reaction zone of the CASS reaction tank is 36m×20m×5.9m=4248m 3 , the water inlet ratio is about 1 / 3.5, i.e. 1214m 3 , the mixed liquid sludge concentration (MLSS) in the CASS reaction tank is controlled at 4000-6000mg / L. The CASS reaction tank adopts a 5h cycle operation mode (i.e. the hydraulic retention time is 5h): the water inlet is 60min, the aeration is about 120min, the sedimentation is about 60min, and the water discharge is about 60min;

[0045] The mixing tank is arranged in the water inlet / aeration / backflow stage, the pretreated sewage, the compound diatomite and the backflow sludge backflowed from the main reaction zone are introduced into the biological selection zone of the CASS reaction tank after the microbial cultivation domestication in the mixing tank, and sequentially undergo the water inlet / aeration / backflow stage, the sedimentation stage and the water discharge stage; the mass ratio of the compound diatomite to the volume of the pretreated sewage is 0.35g:1L;

[0046] Animal manure is periodically added into the mixing tank during the microbial cultivation domestication to promote the growth of microorganisms;

[0047] Urban sewage is sequentially treated by coarse screen filtration, fine screen filtration and grit removal in a grit chamber to obtain pretreated sewage. The pretreated sewage is then fed into the CASS reactor for influent / aeration / recirculation, sedimentation and drainage stages.

[0048] The preparation method of the compound diatomaceous earth is as follows:

[0049] (1) The rice husks are cleaned, dried, crushed and sieved to obtain biomass raw materials;

[0050] (2) After mixing the biomass raw materials and diatomaceous earth obtained in step (1), perform programmed temperature heat treatment, and then cool, grind, activate by acid leaching with hydrochloric acid, wash and dry in sequence to obtain compound diatomaceous earth.

[0051] The programmed temperature rise heat treatment includes the following stages: a first stage: heating from room temperature to 400°C at a heating rate of 8°C / min and holding at that temperature for 50 min; and a second stage: heating from 400°C to 600°C at a heating rate of 3°C / min and holding at that temperature for 120 min.

[0052] The mass ratio of the biomass raw material to diatomaceous earth is 0.5:5.

[0053] The testing methods for each water quality indicator are as follows: COD cr (mg / L), potassium dichromate method; BOD5 (mg / L), dilution and inoculation method; SS (mg / L), gravimetric method; NH4-N (mg / L), Nessler's reagent spectrophotometric method; TN (mg / L), alkaline potassium persulfate digestion UV-Vis spectrophotometric method; TP (mg / L), ammonium molybdate spectrophotometric method. Following the above methods, the water quality of urban wastewater before and after treatment was tested, and the results are shown in Table 1.

[0054] Example 2

[0055] The same method was used to treat urban sewage of the same quality as in Example 1. The difference from Example 1 was that the mass ratio of the biomass raw material and diatomaceous earth was 0.5:4. The water quality before and after urban sewage treatment was tested using the same method as in Example 1. The test results are shown in Table 1.

[0056] Example 3

[0057] The same method was used to treat urban sewage of the same quality as in Example 1. The difference from Example 1 was that the mass ratio of the biomass raw material and diatomaceous earth was 0.5:2. The water quality before and after urban sewage treatment was tested using the same method as in Example 1. The test results are shown in Table 1.

[0058] Table 1 Statistics of urban sewage water quality before and after treatment by the method provided in Examples 1-3

[0059]

[0060] As can be seen from the above, by the method provided in Examples 1-3, the removal rates of COD, BOD5, SS, NH4-N, TN and TP in the treated urban sewage are 98.7%, 96.1%, 95.0%, 98.6%, 94.3% and 90.5% respectively, the method provided in the present application greatly improves the sewage treatment efficiency and the removal rates of nitrogen and phosphorus, and realizes the removal effect of COD, BOD5, SS, NH4-N, TN and TP in the sewage in a short hydraulic retention time. cr cr

[0061] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the protection scope of the present application.​​

Claims

1. A wastewater treatment method utilizing compound diatomaceous earth and CASS process, comprising a pretreated wastewater sequentially entering a mixing tank and a CASS reaction tank in an influent / aeration / recirculation stage, a sedimentation stage, and a drainage stage; The CASS reactor includes a biological selection zone and a main reaction zone; The influent / aeration / return stage is equipped with a mixing tank. The pretreated wastewater, compound diatomaceous earth and return sludge from the main reaction zone are cultured and acclimated to microorganisms in the mixing tank before entering the biological selection zone. The mass ratio of the compounded diatomaceous earth to the volume of the pretreated wastewater is (0.3-6g):1L; The preparation method of the compound diatomaceous earth includes the following steps: (1) Pre-treat agricultural and forestry waste to obtain biomass raw materials; The agricultural and forestry waste in step (1) includes any one or more of rice straw, rice husks, sawdust, tea leaves, Chinese medicine residue, and nut shells; (2) after mixing the biomass raw materials obtained in step (1) with diatomaceous earth, perform programmed heating heat treatment to obtain compound diatomaceous earth. In step (2), the mass ratio of biomass raw materials to diatomaceous earth is (0.02-0.8):(2-6); After the programmed temperature heat treatment in step (2), the product of the programmed temperature heat treatment is further subjected to cooling, grinding, acid leaching activation, washing and second drying in sequence to obtain compound diatomaceous earth. The programmed temperature rise heat treatment in step (2) includes the following stages: first stage: heating from room temperature to 320-450℃ at a heating rate of 5-10℃ / min and holding for 40-60min; second stage: heating from 320-450℃ to 550-650℃ at a heating rate of 1-5℃ / min and holding for 80-200min.

2. The preparation method according to claim 1, characterized in that, The pretreatment in step (1) includes sequentially removing impurities, first drying, crushing, and sieving.

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