Combined pretreatment process specifically for small-scale cattle farm wastewater

Abstract

The present invention relates to a combined pretreatment process specifically used for small-scale cattle farm sewage. The process comprises: taking cattle farm sewage for testing and blending to obtain cattle farm sewage; taking kelp foaming sewage for testing and blending to obtain kelp sewage; adding flocculant FeCl3 solution to cattle farm sewage, and then adding NaOH solution to carry out flocculation reaction; adding kelp sewage for preliminary coagulant reaction; adding cationic polyacrylamide solution for coagulant reaction; filtering the obtained mixed solution through a layer filter to separate sewage and sludge for subsequent processing. The present invention utilizes kelp foaming sewage for combined pretreatment, which can not only effectively remove suspended matter in cattle farm sewage and significantly reduce COD, but also effectively reduce the amount of coagulant aids, and can pretreat the two sewages together at the same time, which is beneficial to improving environmental protection benefits.

Description

Technical Field

[0001] The invention relates to a combined pretreatment process specially used for sewage from a small-scale cattle farm, belonging to the technical field of water treatment and environmental protection. Background Art

[0002] Cattle farm wastewater is mainly wastewater generated by flushing cow urine and cow dung in cattle farms. Cattle farm wastewater has become a difficult problem to treat because it contains high concentrations of suspended solids. If the large amount of suspended solids in cattle farm wastewater is not removed, the following major problems will occur in the wastewater treatment process: (1) If the anaerobic reactor treatment process is adopted, the suspended solids in the wastewater will occupy a large amount of anaerobic reactor volume, which is not conducive to the proliferation of anaerobic bacteria in the anaerobic reactor; (2) If the aerobic activated sludge method is used to treat the wastewater, since the suspended solids occupy a large amount of reactor volume, it is not conducive to the proliferation of nitrite bacteria and nitrifying bacteria with long generation cycles in the activated sludge, and thus is not conducive to the removal of ammonia nitrogen and total nitrogen in the wastewater; (3) If the contact oxidation method is used in the aerobic stage, a large amount of suspended solids will cause the biofilm on the filler to fall off particularly easily, which is not conducive to increasing the biomass of the contact oxidation tank. Conventional processes for removing small-scale high-concentration suspended solids wastewater include sedimentation or flotation. However, for cattle farm wastewater, since the suspended solids concentration in the wastewater is very high and the suspended solids are hydrophilic and highly dispersible, the sedimentation method can neither effectively separate the suspended solids nor obtain sludge with a low water content. The flotation equipment is relatively complex and the investment cost is relatively high, so it is not convenient to use it in small-scale cattle farm wastewater treatment projects.

[0003] After searching, it was found that the invention patent application with application number CN202310237680.8 and application publication number CN116161792A disclosed a ranch sewage treatment system, including a solid-liquid separation pretreatment device, an intermittent biological treatment device and a membrane bioreactor treatment device arranged in sequence according to the sewage treatment order; the solid-liquid separation pretreatment device includes a grid and a solid-liquid separator arranged in sequence; the intermittent biological treatment device is used to biologically treat the sewage discharged by the solid-liquid separator; the membrane bioreactor treatment device is used to filter the sewage after biological treatment again. The prior art represented by this technical solution shows that in the prior art, it is necessary to additionally design a pretreatment device to remove larger suspended matter in the sewage of the cattle farm to minimize the influence of the suspended matter on the subsequent treatment process, but the overall effect of removing suspended matter is still limited. It can be seen that if a simpler suspended matter removal technology can be developed to effectively eliminate the adverse effects of suspended matter, the technology is bound to have broad application prospects. Summary of the invention

[0004] The main purpose of the present invention is to overcome the problems existing in the prior art and propose a combined pretreatment process specifically for small-scale cattle farm sewage. By using kelp-soaked sewage for combined pretreatment, not only can the suspended matter in the cattle farm sewage be effectively removed and the COD be greatly reduced, but the amount of coagulant aid can also be effectively reduced. At the same time, the two types of sewage can be pretreated together, which is beneficial to improving environmental protection benefits.

[0005] The technical solution of the present invention to solve the above technical problems is as follows:

[0006] A combined pretreatment process specifically for small-scale cattle farm wastewater, characterized in that it comprises the following steps:

[0007] The first step is to take the sewage from the cattle farm and test its COD concentration and suspended solids concentration. The COD concentration of the sewage is adjusted to 9500-21000 mg / L, and the suspended solids concentration is 4000-12000 mg / L. The obtained sewage is recorded as cattle farm sewage for subsequent treatment.

[0008] The second step is to take the kelp soaked wastewater and test its COD concentration and suspended solids concentration. The COD concentration of the wastewater is adjusted to 800-1700 mg / L, and the suspended solids concentration is 20-70 mg / L. The resulting wastewater is recorded as kelp wastewater for subsequent treatment.

[0009] The third step is to take the cattle sewage obtained in the first step, and under stirring conditions, gradually add the flocculant FeCl3 solution to the cattle sewage, and then gradually add the NaOH solution to carry out flocculation reaction; the pH value of the obtained mixed solution is 7.2±0.1; in the obtained mixed solution, the flocs have clear boundaries and the water between the flocs is clear and transparent.

[0010] Step 4: Take the kelp wastewater obtained in the second step, and gradually add the kelp wastewater to the mixed solution obtained in the third step under stirring conditions to carry out a preliminary coagulation reaction, so that the equivalent particle size of the flocs in the obtained mixed solution reaches 0.8 to 1.5 mm.

[0011] Step 5: Under stirring conditions, gradually add cationic polyacrylamide solution to the mixed solution obtained in step 4 to perform a coagulant reaction, so that the equivalent particle size of the flocs in the obtained mixed solution reaches 4 to 6 mm.

[0012] Step 6: Use a layer filter with multiple layers of filter bags made of monofilament filter cloth; filter the mixed liquid obtained in step 5 through the layer filter to separate sewage and sludge for separate treatment in subsequent processes.

[0013] The introduction of kelp wastewater for joint pretreatment in this process can effectively remove suspended matter in cattle wastewater, significantly reduce COD, and effectively reduce the amount of coagulant aids used; it can not only effectively pretreat cattle wastewater, but also pretreat kelp wastewater at the same time, thereby improving environmental benefits.

[0014] The technical solution further improved by the present invention is as follows:

[0015] Preferably, in the first step, the preparation method for cattle farm sewage is as follows: for target cattle farm sewage with too high concentration (COD concentration greater than 21000 mg / L and / or suspended solids concentration greater than 12000 mg / L), cattle farm sewage and / or tap water with low concentration (COD concentration and / or suspended solids concentration less than target cattle farm sewage) is added thereto; for cattle farm sewage with too low concentration (COD concentration less than 9500 mg / L and / or suspended solids concentration less than 4000 mg / L), cattle farm sewage with high concentration (COD concentration and / or suspended solids concentration greater than target cattle farm sewage) is added thereto.

[0016] Preferably, in the second step, the preparation method for the kelp soaked sewage is as follows: for the target kelp soaked sewage with too high concentration (meaning the COD concentration is greater than 1700 mg / L and / or the suspended matter concentration is greater than 70 mg / L), add kelp soaked sewage and / or tap water with low concentration (meaning the COD concentration and / or the suspended matter concentration is less than the target kelp soaked sewage); for the kelp soaked sewage with too low concentration (meaning the COD concentration is less than 800 mg / L and / or the suspended matter concentration is less than 20 mg / L), add kelp soaked sewage with high concentration (meaning the COD concentration and / or the suspended matter concentration is greater than the target kelp soaked sewage).

[0017] Preferably, in the third step, the ratio of the mass of suspended matter in the cattle sewage to the mass of FeCl3 contained in the added flocculant is 4:1 to 18:1; the mass concentration of the FeCl3 solution is 10±0.5%; and the mass concentration of the NaOH solution is 10±0.5%.

[0018] An example of mass concentration: For example, a mass concentration of 10% means that each milliliter of solution contains 0.1 g of solute, and so on.

[0019] Preferably, in the fourth step, the volume ratio of cattle wastewater to kelp wastewater is 2:1 to 4:1.

[0020] Preferably, in the fifth step, the volume ratio of the mixed solution obtained in the fourth step to the cationic polyacrylamide solution is 15:1 to 40:1; the mass concentration of the cationic polyacrylamide solution is 0.1±0.01%; and the molecular weight of the cationic polyacrylamide is 10 million±1 million.

[0021] Preferably, after the kelp sewage is prepared in the second step, the treatments from the third step to the sixth step are completed within 1 hour, and the sludge in the filter is removed and the filter bag is cleaned within 3 hours thereafter. This can avoid the problem of kelp sewage and sludge being corrupted and stinking and the sludge disintegrating.

[0022] Preferably, in the sixth step, the layer filter has a pool body with an opening at the top, and the interior of the pool body includes an inlet storage area and an outlet storage area that are formed by partitions and isolated from each other; a water inlet pipe is provided on the top of the water inlet storage area, and a solenoid valve for controlling the on and off of the water inlet pipe and a water inlet regulating valve for adjusting the amount of inlet water are provided on the water inlet pipe; a water outlet hose is provided in the water outlet storage area, and the water inlet of the water outlet hose is arranged vertically upward and a buoy is fixed around it, so that the water inlet floats on the liquid surface in the water outlet storage area and remains connected with the liquid; the water outlet hose passes through the lower side wall of the water outlet storage area and is sealed with the side wall, and the water outlet of the water outlet hose is located outside the pool body and connected to the outside; the water outlet hose is provided with a water outlet regulating valve for adjusting the amount of outflow water.

[0023] At least one layer of filter bags is arranged horizontally in the water outlet storage area of ​​the pool body, and the filter bags are made of monofilament filter cloth; a water inlet is provided at one end of the filter bag, and the water inlet is connected with the water outlet end of the water inlet main pipe through a transition pipe, the water inlet main pipe passes through the partition and is sealed to the partition, and the water inlet end of the water inlet main pipe is fixed to the lower part of the water inlet storage area; a differential pressure gauge is provided at the bottom of the partition for measuring the liquid level difference between the water inlet storage area and the water outlet storage area.

[0024] More preferably, during filtration, when the liquid level difference is greater than a first set value, the solenoid valve is closed to stop water inlet, and when the liquid level difference is less than a second set value, the solenoid valve is opened to start water inlet.

[0025] When the thickness of the filter cake reaches or approaches the thickness limit value, the water inlet volume is gradually reduced by controlling the water inlet regulating valve, and at the same time, the water outlet regulating valve is controlled to keep the liquid level difference smaller than the first set value until the water inlet stops completely; when the water inlet stops completely and the lowest water level in the outlet water storage area is lower than the vertical distance of the lowest point of all filter bags by more than the third set value, all filter bags are kept to continue filtering water, and the water flows to the lowest point of the outlet water storage area, and the water continues to be drained through the outlet hose until no water is filtered out of the filter bags.

[0026] More preferably, a height difference is formed between the lowest point of the filter bag and the bottom of the water outlet storage area, and the height difference is greater than the third set value; a water-permeable filter aid plate is provided above and / or below the filter bag; the filter bag is also provided with a water-sealed zipper for mud discharge and / or filter bag cleaning; a filter bag positioning piece is also provided in the water outlet storage area; when the mesh number of the monofilament filter cloth is 150-250 mesh, the first set value is 20±1mm, the second set value is 14±1mm, and the average liquid level difference is controlled at 15±1mm; the third set value is at least 20mm; the thickness limit value is 8±1mm.

[0027] By adopting the above preferred scheme, the specific technical characteristics of each step of the process can be further improved.

[0028] Compared with the prior art, the present invention utilizes kelp-soaked wastewater for joint pretreatment, which can not only effectively remove suspended matter in cattle-raising wastewater and significantly reduce COD, but also effectively reduce the amount of coagulant aids used. At the same time, the two types of wastewater can be pretreated together, which is beneficial to improving environmental protection benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a processing flow chart of Example 2 of the present invention.

[0030] Figure 2 This is a processing flow chart of Example 3 of the present invention.

[0031] Figure 3 It is the molecular formula of the laminarin mentioned in Example 3 of the present invention.

[0032] Figure 4 This is a structural diagram of a 4-layer filter according to an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The combined pretreatment process specifically used for small-scale cattle farm sewage implemented in the present invention comprises the following steps:

[0034] The first step is to take the sewage from the cattle farm and test its COD concentration and suspended solids concentration. The COD concentration of the sewage is adjusted to 9500-21000 mg / L, and the suspended solids concentration is 4000-12000 mg / L. The obtained sewage is recorded as cattle farm sewage for subsequent treatment.

[0035] Among them, the allocation method for cattle farm wastewater is as follows: for target cattle farm wastewater with too high concentration (COD concentration greater than 21000mg / L and / or suspended solids concentration greater than 12000mg / L), add cattle farm wastewater with low concentration (COD concentration and / or suspended solids concentration less than target cattle farm wastewater) and / or tap water; for cattle farm wastewater with too low concentration (COD concentration less than 9500mg / L and / or suspended solids concentration less than 4000mg / L), add cattle farm wastewater with high concentration (COD concentration and / or suspended solids concentration greater than target cattle farm wastewater).

[0036] The second step is to take the kelp soaked wastewater and test its COD concentration and suspended solids concentration. The COD concentration of the wastewater is adjusted to 800-1700 mg / L, and the suspended solids concentration is 20-70 mg / L. The resulting wastewater is recorded as kelp wastewater for subsequent treatment.

[0037] Among them, the preparation method for kelp soaked sewage is as follows: for target kelp soaked sewage with too high concentration (COD concentration greater than 1700 mg / L and / or suspended matter concentration greater than 70 mg / L), add kelp soaked sewage and / or tap water with low concentration (COD concentration and / or suspended matter concentration less than the target kelp soaked sewage); for kelp soaked sewage with too low concentration (COD concentration less than 800 mg / L and / or suspended matter concentration less than 20 mg / L), add kelp soaked sewage with high concentration (COD concentration and / or suspended matter concentration greater than the target kelp soaked sewage).

[0038] The third step is to take the cattle sewage obtained in the first step, and under stirring conditions, gradually add the flocculant FeCl3 solution to the cattle sewage, and then gradually add the NaOH solution to carry out flocculation reaction; the pH value of the obtained mixed solution is 7.2±0.1; in the obtained mixed solution, the flocs have clear boundaries and the water between the flocs is clear and transparent.

[0039] The ratio of the mass of suspended matter in the cattle sewage to the mass of FeCl3 contained in the added flocculant is 4:1-18:1; the mass concentration of the FeCl3 solution is 10±0.5%; and the mass concentration of the NaOH solution is 10±0.5%.

[0040] Step 4: Take the kelp wastewater obtained in the second step, and gradually add the kelp wastewater to the mixed solution obtained in the third step under stirring conditions to carry out a preliminary coagulation reaction, so that the equivalent particle size of the flocs in the obtained mixed solution reaches 0.8 to 1.5 mm.

[0041] Among them, the volume ratio of cattle wastewater to kelp wastewater is 2:1 to 4:1.

[0042] Step 5: Under stirring conditions, gradually add cationic polyacrylamide solution to the mixed solution obtained in step 4 to perform a coagulant reaction, so that the equivalent particle size of the flocs in the obtained mixed solution reaches 4 to 6 mm.

[0043] The volume ratio of the mixed solution obtained in the fourth step to the cationic polyacrylamide solution is 15:1 to 40:1; the mass concentration of the cationic polyacrylamide solution is 0.1±0.01%; and the molecular weight of the cationic polyacrylamide is 10 million±1 million.

[0044] Step 6: Use a layer filter with multiple layers of filter bags made of monofilament filter cloth; filter the mixed liquid obtained in step 5 through the layer filter to separate sewage and sludge for separate treatment in subsequent processes.

[0045] Since kelp wastewater is easy to spoil and stink, after the kelp wastewater is prepared in the second step, the third to sixth steps are completed within 1 hour, and the sludge in the filter is removed and the filter bag is cleaned within the next 3 hours to avoid the problem of sludge spoilage and odor and sludge disintegration.

[0046] The present invention is further described in detail below in conjunction with the examples, but the present invention is not limited to the examples given.

[0047] Example 1

[0048] This embodiment is to analyze the water quality characteristics of the sewage after mixing. The specific mixing method is shown in the technical solution of the specific implementation of the present invention above.

[0049] (1) Cattle farm wastewater

[0050] The prepared cattle farm sewage (referred to as cattle farm sewage) was taken and, while being stirred as evenly as possible, its pH was measured to be 7.3, COD concentration to be 15500 mg / L, and suspended solids SS concentration to be 8500 mg / L.

[0051] After the sewage had been statically settled for 24 hours, there was scum on the water surface, and the sewage under the scum did not become clear, and the sewage was turbid as a whole.

[0052] (2) Kelp soaking wastewater

[0053] The pH of the prepared kelp foaming wastewater (referred to as kelp wastewater) was measured to be 7.2, the COD concentration was 1600 mg / L, the water was clear and transparent, and the suspended matter concentration was 25 mg / L.

[0054] The source of kelp soaking wastewater is: in the factory, kelp is soaked in water (the water used complies with relevant regulations), the soaking temperature is controlled between 15℃ and 25℃, and the soaking time is controlled within 3.5 hours; after the soaking is completed, the kelp is separated and the wastewater is discharged, which is the kelp soaking wastewater. The wastewater has a noticeable sticky feeling when touched by hand.

[0055] Example 2

[0056] This embodiment is a pretreatment process for kelp wastewater involved in the research process of the present invention.

[0057] The specific contents of this embodiment are as follows:

[0058] 1. Flocculation and flocculant screening test

[0059] (1) Experiment using flocculant AlCl3

[0060] Take 10L of cattle sewage in Example 1, and gradually add 69.5mL of 10% AlCl3 solution while stirring continuously, and then gradually add 62mL of 10% NaOH solution. The pH is measured to be 7.3, and the generated flocs are observed to be loose, and the water between the flocs is turbid; take an appropriate amount of sample, continue to add 10% NaOH solution until the pH is 8.0, and the water between the flocs is still turbid.

[0061] (2) Experiment using flocculant FeCl3

[0062] Take 50L of cattle sewage from Example 1, and gradually add 425mL of 10% FeCl3 solution (Note: the total molar concentration added is the same as AlCl3 in (1)) under continuous stirring, and then gradually add 310mL of 10% NaOH solution. After measuring the pH value at 7.3, it is observed that the flocs produced have clear boundaries and the water between the flocs is clear and transparent; take an appropriate amount of sample and continue to add 10% NaOH solution until the pH value is 8.0, and the water between the flocs is still clear and transparent.

[0063] By comparing the test results of (1) and (2) above, it can be seen that the treatment effect of using FeCl3 as a flocculant is significantly better than that of AlCl3.

[0064] (3) Other flocculants tests and conclusions

[0065] Polyaluminium sulfate and polyaluminium chloride were used as flocculants respectively. According to the requirements of the corresponding flocculation tests, the same Al as (1) and (2) was added. 3+ (or Fe 3+ ) molar concentration condition, the cattle wastewater of Example 1 was subjected to a flocculation test. The test results showed that the flocculation effect was obviously inferior to that of FeCl3. Therefore, FeCl3 was used as a flocculant in subsequent tests.

[0066] 2. Coagulation aid test

[0067] Take the mixed solution obtained in (2) of the above 1, and gradually add 0.1% cationic polyacrylamide (PAM) solution with a molecular weight of 10 million while constantly stirring at a stirring speed of 1 rpm. In the process of adding an amount from 0 to 2600 mL, the equivalent particle size of the floccules gradually increases from about 0.5 mm to 4-6 mm, completing the coagulation process.

[0068] 3. Filtration test

[0069] A layer filter with multiple layers of filter bags is used, and the filter bags are made of monofilament filter cloth; the mixed liquid obtained in the above 2 is filtered through the layer filter, and the effluent is clear and transparent. The final filtered water sample is tested for COD of 12500mg / L and suspended solids of 20mg / L.

[0070] Summarize:

[0071] The above treatment process using FeCl3 as flocculant and cationic polyacrylamide with a molecular weight of 10 million as coagulant aid (such as Figure 1 As shown), it can effectively remove suspended solids in cattle wastewater and remove part of the COD.

[0072] Example 3

[0073] This embodiment adopts a combined pretreatment process of kelp wastewater.

[0074] The specific contents of this embodiment are as follows:

[0075] 1. Preliminary coagulation test

[0076] Take 50L of cattle sewage of Example 1, and gradually add 425mL of 10% FeCl3 solution and 310mL of 10% NaOH solution under continuous stirring. The pH is measured to be 7.3, and the generated flocs have clear boundaries and the water between the flocs is clear and transparent. Under rapid stirring, 15L of kelp sewage of Example 1 is quickly added to the flocculated water. During the addition process, the equivalent particle size of the flocs gradually increases from about 0.3mm to 0.8-1.5mm, completing the initial coagulation process.

[0077] 2. Coagulation aid test

[0078] Take the mixed solution obtained in 1 above, gradually add 0.1% cationic polyacrylamide (PAM) solution with a molecular weight of 10 million, and in the process of adding amount from 0 to 1820 mL, the equivalent particle size of flocs gradually increases from 0.8-1.5 mm to 4-6 mm, completing the coagulation process.

[0079] 3. Filtration test

[0080] A layer filter with multiple layers of filter bags is used, and the filter bags are made of monofilament filter cloth; the mixed liquid obtained in the above 2 is filtered through the layer filter, and the effluent is clear and transparent. The final filtered water sample is tested for COD of 9600mg / L and suspended solids of 20mg / L.

[0081] Summarize:

[0082] The processing technology of this embodiment (such as Figure 2 The introduction of kelp wastewater for joint pretreatment can effectively remove suspended solids in cattle wastewater, significantly reduce COD, and effectively reduce the dosage of coagulant PAM; it can not only effectively pretreat cattle wastewater, but also pretreat kelp wastewater at the same time, thereby improving environmental benefits.

[0083] It is speculated that the principle is that kelp wastewater contains a large amount of kelp polysaccharide, which is a high molecular weight organic substance with the molecular formula Figure 3 As shown; kelp polysaccharide is rich in hydroxyl groups, which will adsorb charged particles in the water. After the charged particles are adsorbed to the hydroxyl groups in kelp polysaccharide, they will play an adsorption and bridging role in flocculation and coagulant reactions.

[0084] Example 4

[0085] This embodiment is a specific example of the layer filter used in Embodiment 2 and Embodiment 3.

[0086] like Figure 4 As shown, the layer filter has a pool body with an opening at the top, and the inside of the pool body includes an inlet water storage area 01 and an outlet water storage area 02 which are separated and isolated from each other by a partition 21. A water inlet pipe 03 is provided at the top of the water inlet water storage area 01, and a solenoid valve 04 and a water inlet regulating valve 05 are provided on the water inlet pipe 03. The solenoid valve 04 is used to control the on and off of the water inlet pipe 03, and the water inlet regulating valve 05 is used to adjust the amount of water in the water inlet. The outlet water storage area 02 is provided with an outlet hose 06, and the water inlet 07 of the outlet hose 06 is arranged vertically upward and a buoy 08 is fixed around it, so that the water inlet 07 floats on the liquid surface in the outlet water storage area 02 and maintains communication with the liquid; the outlet hose 06 passes through the lower side wall of the outlet water storage area 02 and is sealed and connected to the side wall, and the outlet 09 of the outlet hose 06 is located outside the pool body and communicates with the outside. The water outlet hose 06 is provided with a water outlet regulating valve 10 for adjusting the amount of water outlet.

[0087] At least one layer of filter bags 11 is arranged horizontally in the outlet water storage area 02 of the pool body. The filter bags 11 are made of monofilament filter cloth. A height difference is formed between the lowest point of the filter bag 11 and the bottom of the water collection area, and the height difference can be greater than 20 mm. A water inlet 12 is provided at one end of the filter bag 11. The water inlet 12 is connected to the outlet end of the water inlet main pipe 14 through a transition pipe 13. The water inlet main pipe 14 passes through the partition 21 and is sealed to the partition 21. The water inlet end 15 of the water inlet main pipe 14 is fixed to the lower part of the water inlet water storage area 01. A permeable filter aid plate 16 is provided above and / or below the filter bag 11. A differential pressure gauge 17 is provided at the bottom of the partition 21 to measure the liquid level difference between the water inlet water storage area 01 and the water outlet water storage area 02 (Note: the water pressure in the filter bag 11 is determined by the liquid level difference). In addition, the filter bag 11 is also provided with a water-sealed zipper 18 for mud discharge and / or cleaning of the filter bag 11 ; a filter bag positioning piece 19 is also provided in the water outlet storage area 02 .

[0088] Since the filter bag 11 is arranged horizontally, the filter bag 11 is mainly filtered through the upper side monofilament filter cloth and the lower side monofilament filter cloth. During the filtering process of the upper side monofilament filter cloth, the size of the flocs continues to increase, and the gravity it is subjected to increases at the same time. Under the condition of controlling the water pressure at a low level and the floc concentration is not high, the flocs will automatically separate from the filter cloth, so that the upper side monofilament filter cloth has a self-cleaning function. At the same time, for the entire filter bag 11, due to the control of a relatively small water pressure, the flocs and interstitial water in the filter bag 11 are separated from each other, and a tight filter layer connected by the flocs will not be formed. The interstitial water is interconnected, directly contacts the filter cloth and is discharged, thereby achieving continuous and rapid discharge of the interstitial water of the flocs.

[0089] The basic process of using the filter of this embodiment to filter sewage is as follows: the water to be filtered enters the water inlet storage area 01 from the water inlet pipe 03, and then enters each filter bag 11 through the water inlet main pipe 14 and the transition pipe 13 for filtration, and the filtered water of the filter bag 11 enters the water outlet storage area 02 and is finally discharged through the water outlet hose 06. After that, the sludge filter cake in the filter bag 11 is taken out for sludge disposal, and the filter bag is cleaned for reuse.

[0090] After systematic test research, it was determined that the control points of the filter in this embodiment are:

[0091] (1) The liquid level difference between the inlet water storage area 01 and the outlet water storage area 02 should be controlled during filtration. When the liquid level difference is greater than the first set value, the solenoid valve 04 is closed to stop the water inlet; when the liquid level difference is less than the second set value, the solenoid valve 04 is opened to start the water inlet. Among them, when the mesh number of the monofilament filter cloth is 150-250 mesh, the first set value can be 20±1mm, and the second set value can be 14±1mm, so that the average liquid level difference is controlled at 15±1mm. Since the water pressure in the filter bag 11 is determined by the liquid level difference between the inlet water storage area 01 and the outlet water storage area 02, the above-mentioned control points can maintain a moderate and relatively constant filtration pressure in the filter bag 11.

[0092] (2) The thickness of the filter cake formed in the filter bag 11 should be below the thickness limit value, so as to facilitate the discharge of interstitial water in the flocs. A filter layer that is too thick is not conducive to the discharge of interstitial water in the flocs. The thickness limit value may be 8±1 mm.

[0093] (3) When the thickness of the filter cake reaches or approaches the thickness limit value, the water inlet amount is gradually reduced by controlling the water inlet regulating valve 05, and at the same time, the liquid level difference is always less than the first set value by controlling the water outlet regulating valve 10 until the water inlet stops completely; when the water inlet stops completely, and the water level at the lowest point of the outlet water storage area 02 is more than 20 mm lower than the vertical distance of the lowest point of all the filter bags 11, all the filter bags 11 are kept to continue to filter out water (Note: you can wait for the filter bags to filter out by themselves, or you can add additional weights for pressure filtration), and the water flows to the lowest point of the outlet water storage area 02, and the water continues to be drained by the outlet hose 06 until there is no water filtered out of the filter bags; this can effectively reduce the moisture content of the sludge in the filter bags 11, thereby reducing the final disposal amount of the sludge.

[0094] In Example 2 and Example 3, the filter of this embodiment was used and controlled according to the above control points. The filter filtered out 90% of the water sample within 1 minute, and the effluent was clear and transparent.

[0095] The filter of this embodiment can achieve ultra-low and moderate filtering pressure, and the pressure applied to the formed flocs is very small. During the filtration process, the flocs and the interstitial water of the flocs are still retained independently, so that the interstitial water of the flocs can smoothly flow from the gaps to the filter cloth and be filtered out.

[0096] The filter equipment of this embodiment has low investment, low filtration pressure, fast filtration speed, clear effluent, and moderate moisture content of the formed filter cake; compared with the filter press method and the centrifugal method, it can greatly save the amount of coagulant aid, with the saving rate exceeding 80%; at the same time, the filter of this embodiment has a simple structure and a moderate single processing volume, and is particularly suitable for small-scale cattle farm sewage treatment projects.

[0097] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A combined pretreatment process for small-scale cattle farm wastewater, characterized in that: The following steps are involved: The first step is to take the wastewater from the cattle farm and test its COD concentration and suspended solids concentration. The COD concentration of the wastewater is adjusted to 9500~21000mg / L and the suspended solids concentration is adjusted to 4000~12000mg / L. The wastewater obtained is recorded as cattle farm wastewater for subsequent treatment. The second step is to take the kelp soaking wastewater and detect its COD concentration and suspended solids concentration, and adjust the COD concentration of the wastewater to 800-1700 mg / L and the suspended solids concentration to 20-70 mg / L; the resulting wastewater is recorded as kelp wastewater for subsequent treatment; Step 3: Take the cattle sewage obtained in the first step, and gradually add the flocculant FeCl3 solution and then the NaOH solution to the cattle sewage under stirring conditions to carry out flocculation reaction; the pH of the obtained mixed solution is 7.2±0.1; in the obtained mixed solution, the flocs have clear boundaries and the water between the flocs is clear and transparent; Among them, the ratio of the mass of suspended matter in cattle wastewater to the mass of FeCl3 contained in the added flocculant is 4:1~18:1; the mass concentration of FeCl3 solution is 10±0.5%; the mass concentration of NaOH solution is 10±0.5%; Step 4: Take the kelp wastewater obtained in the second step, and gradually add the kelp wastewater to the mixed solution obtained in the third step under stirring conditions to carry out a preliminary coagulation reaction, so that the equivalent particle size of flocs in the obtained mixed solution reaches 0.8-1.5 mm; Among them, the volume ratio of cattle wastewater to kelp wastewater is 2:1~4:1; Step 5: under stirring conditions, gradually add cationic polyacrylamide solution to the mixed solution obtained in step 4 to perform coagulation-aiding reaction, so that the equivalent particle size of flocs in the obtained mixed solution reaches 4-6 mm; The volume ratio of the mixed solution obtained in the fourth step to the cationic polyacrylamide solution is 15:1-40:1; the mass concentration of the cationic polyacrylamide solution is 0.1±0.01%; the molecular weight of the cationic polyacrylamide is 10 million±1 million; Step 6: Using a layer filter with multiple layers of filter bags made of monofilament filter cloth; filtering the mixed liquid obtained in step 5 through the layer filter to separate sewage and sludge for subsequent processing; The layer filter has a pool body with an opening at the top, and the inside of the pool body includes a water inlet storage area and a water outlet storage area which are separated by partitions and isolated from each other; a water inlet pipe is arranged at the top of the water inlet storage area, and a solenoid valve for controlling the on and off of the water inlet pipe and a water inlet regulating valve for adjusting the amount of water inlet are arranged on the water inlet pipe; a water outlet hose is arranged in the water outlet storage area, and the water inlet of the water outlet hose is arranged vertically upward and a buoy is fixed around it, so that the water inlet floats on the liquid surface in the water outlet storage area and keeps in communication with the liquid; the water outlet hose passes through the lower side wall of the water outlet storage area and is sealed and connected to the side wall, and the water outlet of the water outlet hose is located outside the pool body and is in communication with the outside; the water outlet hose is provided with a water outlet regulating valve for adjusting the amount of water in the water outlet; The filter bag is arranged transversely in the outlet water storage area of ​​the pool body; a water inlet is provided at one end of the filter bag, the water inlet is connected to the outlet end of the water inlet main pipe through a transition pipe, the water inlet main pipe passes through the partition and is sealed to the partition, and the water inlet end of the water inlet main pipe is fixed to the lower part of the water inlet water storage area; a differential pressure gauge is provided at the bottom of the partition for measuring the liquid level difference between the water inlet water storage area and the water outlet water storage area; During filtration, when the liquid level difference is greater than a first set value, the solenoid valve is closed to stop water inflow, and when the liquid level difference is less than a second set value, the solenoid valve is opened to start water inflow; When the thickness of the filter cake reaches or approaches the thickness limit value, the water inlet amount is gradually reduced by controlling the water inlet regulating valve, and the water outlet regulating valve is controlled at the same time to make the liquid level difference always smaller than the first set value until the water inlet stops completely; when the water inlet stops completely and the water level in the outlet water storage area is lower than the lowest point of all filter bags by more than the third set value, all filter bags are kept to continue filtering water, and the water flows to the lowest point of the outlet water storage area, and the water continues to be drained by the outlet hose until there is no water filtered out of the filter bags; When the mesh number of the monofilament filter cloth is 150-250 mesh, the first setting value is 20±1mm, the second setting value is 14±1mm; the third setting value is at least 20 mm; the thickness limit value is 8±1mm; A height difference is formed between the lowest point of the filter bag and the bottom of the outlet water storage area, and the height difference is greater than the third set value.

2. A combined pretreatment process for small-scale cattle farm wastewater according to claim 1, Its characteristic is that, in the first step, the method for dispensing the wastewater from the cattle farm is: For target cattle farm sewage with too high concentration, add cattle farm sewage with low concentration and / or tap water; wherein, too high concentration means COD concentration greater than 21000mg / L and / or suspended solids concentration greater than 12000mg / L, and low concentration means COD concentration and / or suspended solids concentration less than target cattle farm sewage; For target cattle farm wastewater with too low concentration, cattle farm wastewater with high concentration is added thereto; wherein, too low concentration means that the COD concentration is less than 9500 mg / L and / or the suspended solids concentration is less than 4000 mg / L, and high concentration means that the COD concentration and / or the suspended solids concentration is greater than the target cattle farm wastewater.

3. A combined pretreatment process for small-scale cattle farm wastewater according to claim 2, characterized in that: In the second step, the preparation method for kelp soaking wastewater is: For target kelp foaming wastewater with too high concentration, add kelp foaming wastewater with low concentration and / or tap water thereto; wherein, too high concentration means COD concentration greater than 1700 mg / L and / or suspended matter concentration greater than 70 mg / L, and low concentration means COD concentration and / or suspended matter concentration less than the target kelp foaming wastewater; For target kelp soaked wastewater with too low concentration, add kelp soaked wastewater with high concentration into it; wherein, too low concentration means COD concentration is less than 800 mg / L and / or suspended matter concentration is less than 20 mg / L, and high concentration means COD concentration and / or suspended matter concentration is greater than target kelp soaked wastewater.

4. A combined pretreatment process for small-scale cattle farm wastewater according to claim 3, characterized in that: After the kelp wastewater is prepared in the second step, the treatment of the third to sixth steps is completed within 1 hour, and the removal of the sludge in the filter and the cleaning of the filter bag are completed within the next 3 hours.

5. A combined pretreatment process for small-scale cattle farm wastewater according to any one of claims 1 to 4, characterized in that: A water-permeable filter-aiding plate is arranged above and / or below the filter bag; the filter bag is also provided with a water-sealed zipper for mud discharge and / or filter bag cleaning; a filter bag positioning piece is also arranged in the water outlet and water storage area.

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