Efficient treatment method of pre-prepared vegetable wastewater

Abstract

The invention relates to the technical field of sewage treatment, in particular to an efficient treatment method of pre-prepared vegetable wastewater, which comprises the following steps: pre-treating the pre-prepared vegetable wastewater through a grating and then flowing into a water inlet pump room; conveying the pretreated wastewater to an oil separation sedimentation tank; effluent of the oil separation sedimentation tank enters a regulating tank; effluent of the adjusting tank enters a dissolved air flotation tank; effluent of the dissolved air floatation tank enters a UASB anaerobic reactor; effluent of the UASB anaerobic reactor enters an AAO biochemical system; effluent of the AAO biochemical system enters a powdered activated carbon membrane bioreactor; and the effluent of the powdered activated carbon membrane bioreactor enters a disinfection tank, a disinfectant is added for disinfection, and the effluent is discharged after reaching the standard. The invention provides an efficient treatment method for wastewater discharged by a prefabricated vegetable production enterprise mainly comprising high COD (Chemical Oxygen Demand), animal and vegetable oil, suspended substances and protein, and pollutants which are difficult to treat can be separated and removed, so that the operation cost is greatly reduced, and meanwhile, possible resource utilization is realized.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and in particular to a method for efficiently treating wastewater from prepared dishes. Background Art

[0002] Pre-prepared meals (also known as pre-made dishes) are the product of food industrialization. They are made from one or more edible agricultural products and their products as raw materials, and are made through industrial pre-processing (such as stirring, pickling, tumbling, kneading, shaping, frying, deep-frying, baking, boiling, steaming, etc.). They are pre-packaged dishes that can only be eaten after heating or cooking. The pre-prepared meal industry is a new industrial model. The production wastewater and cleaning wastewater generated by pre-prepared meal manufacturers during the production process often do not meet the emission standards.

[0003] According to the production model of pre-prepared dishes, the main pollutants discharged from sewage are as follows:

[0004] 1. Production enterprises that mainly emit animal and vegetable oils; 2. Production enterprises that mainly emit salt; 3. Production enterprises that mainly emit protein; 4. Production enterprises that mainly emit COD.

[0005] The above factors lead to the high concentration of organic pollutants in pre-prepared food wastewater, great difficulty in treatment and uninterrupted discharge. Direct discharge will cause impact load on the sewage discharge network and downstream secondary sewage treatment plants, causing environmental pollution and environmental supervision problems. Summary of the invention

[0006] The purpose of the present invention is to provide a highly efficient treatment method for pre-prepared food wastewater, which can efficiently treat wastewater discharged by pre-prepared food production enterprises with high COD, animal and vegetable oils, suspended matter and protein as the main components, and can separate and remove difficult-to-treat pollutants, greatly reducing operating costs while realizing possible resource utilization.

[0007] The solution adopted by the present invention to achieve the purpose is: a highly efficient method for treating pre-prepared food wastewater, comprising the following steps:

[0008] (1) The pre-prepared food wastewater is pre-treated through a screen to separate and remove large suspended impurities before flowing into the water inlet pump room;

[0009] (2) The pre-treated wastewater is transported to the oil separation sedimentation tank through the water intake pump room to separate oily substances and easily precipitated suspended solids;

[0010] (3) The effluent from the oil separation sedimentation tank enters the regulating tank for average and volume treatment;

[0011] (4) The effluent from the regulating tank enters the dissolved air flotation tank, where flocculants are added to generate a large number of fine bubbles in the water by pressurizing it, so that the bubbles attach to the suspended particles, thereby achieving separation of water and suspended matter;

[0012] (5) The effluent from the dissolved air flotation tank enters the UASB anaerobic reactor, causing the wastewater to pass upward through the sludge bed, where anaerobic reactions occur during contact with the sludge bed;

[0013] (6) The effluent from the UASB anaerobic reactor enters the AAO (Anaerobic-Anoxic-Oxic) biochemical system, where most of the COD, BOD, ammonia nitrogen, total nitrogen, total phosphorus, and suspended matter in the sewage are removed through microorganisms in the activated sludge;

[0014] (7) The effluent from the AAO biochemical system enters the powdered activated carbon membrane bioreactor, where the powdered activated carbon is used to adsorb and remove the difficult-to-biodegrade COD in the sewage, and the saturated powdered activated carbon is separated by an immersed ultrafiltration membrane;

[0015] (8) The effluent from the powdered activated carbon membrane bioreactor enters the disinfection tank, where disinfectant is added for disinfection before being discharged in compliance with the standards.

[0016] The integrated flotation process can select an economical dosage of reagents according to the concentration of suspended matter in the water and the TP (total phosphorus) requirements of the effluent.

[0017] The high-efficiency treatment method of UASB anaerobic reactor can greatly reduce the cost of treating high-concentration wastewater from pre-prepared food, while ensuring that the subsequent processes can meet the discharge standards;

[0018] The use of powdered activated carbon membrane bioprocess can effectively reduce COD, improve the system's resistance to shock loads, reduce the amount of difficult-to-degrade or degradable pollutants, and ensure that the effluent meets the standards stably.

[0019] Preferably, in step (1), the grid bar gap of the grid is selected to be 1-3 mm.

[0020] Preferably, in step (1), the water pump in the water intake pump room is selected to be a submersible sewage pump, and the typical residence time in the water intake pump room is 0.05-1h.

[0021] Preferably, in step (2), the typical value of the designed surface hydraulic load of the oil separation sedimentation tank is 1-2m 3 / m 2 ·h, the residence time is 1-2h, and the generated precipitated sludge enters the sludge storage tank.

[0022] Preferably, in step (3), the hydraulic retention time of the regulating pond is adjusted to 8-10 hours.

[0023] Preferably, in step (4), the flocculants are PAC (polyaluminium chloride) and PAM (polyacrylamide), the typical dosage of PAC is 50-450 mg / L, the alumina content is ≥28%, the typical dosage of PAM is 1-6 mg / L, and the generated flotation sludge enters the sludge storage tank.

[0024] Preferably, in step (5), the typical value of the residual sludge yield is 0.07-0.1 kg MLSS / kg COD, the effluent COD value is 600-100 mg / L, SS ≤ 100 mg / L, and the residual sludge produced enters the sludge storage tank.

[0025] Preferably, in step (6), the operating parameters of the AAO biochemical system are: anoxic tank residence time: 4-10h; aerobic tank residence time: 10-15h; anoxic tank DO index ≤0.5mg / L, aerobic tank DO index>2mg / L, sludge yield: 0.3-0.6kgSS / kgBOD5; biochemical system BOD5 load: 0.05-0.15kgBOD5 / kgMLSS.d; biochemical system NH3-N load: 0.02-0.05kgNH3-N / kgMLSS.d; biochemical system TN load: 0.03-0.04kgTN / kgMLSS.d; sludge return ratio>67%; mixed liquor return ratio>65%; sludge age: 10-14.5 days; sludge concentration: 2500-4500mg / L; SVI: 100-150mL / g.

[0026] Preferably, in step (7), the process parameters of powdered activated carbon are: 100-400 mesh, methylene blue value ≥12 ml / 0.1 g, iodine value ≥800 mg / g, ash content ≤8%, the ratio of activated carbon dosage to influent water volume is 100-300 mg / L, and the activated carbon concentration in the bioreactor pool is within 30,000 mg / L.

[0027] Preferably, in step (7), the average flux of the immersed ultrafiltration membrane during process operation is 12-18 L / ㎡.h, the gas-water ratio during operation is 10-15:1, water production is 6-10 min, backwashing is 1-3 min, and online chemical washing is performed by adding 100-500 mg / L of effective chlorine sodium hypochlorite and 0.5% sodium citrate to recover the flux.

[0028] The present invention has the following advantages and beneficial effects:

[0029] The present invention provides a highly efficient method for treating wastewater discharged by pre-prepared food production enterprises, which is mainly composed of high COD, animal and vegetable oils, suspended matter and protein. The method can separate and remove the pollutants that are difficult to treat, greatly reduce the operating costs and realize possible resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the method flow of the present invention. DETAILED DESCRIPTION

[0031] For a better understanding of the present invention, the following examples are provided to further illustrate the present invention, but the present invention is not limited to the following examples.

[0032] Example 1

[0033] An efficient method for treating wastewater from prepared dishes comprises the following steps:

[0034] (1) The pre-prepared food wastewater is pre-treated through a screen to separate and remove large suspended impurities in the wastewater before flowing into the water inlet pump room;

[0035] (2) The pre-treated wastewater is further transported to the oil separation sedimentation tank through the pumping action of the water intake pump room, and the oil and fat substances in the water are floated by gravity, so that the precipitated suspended substances are precipitated and removed;

[0036] (3) The effluent from the oil separation sedimentation tank enters the regulating tank, where it is treated with average value and quantity;

[0037] (4) The effluent from the regulating tank enters the dissolved air flotation tank, where flocculants are added to generate a large number of fine bubbles in the water by pressurizing it. The bubbles adhere to the suspended particles and float to the water surface due to their low density, thus achieving separation of water and suspended matter.

[0038] (5) The effluent from the dissolved air flotation tank enters the UASB anaerobic reactor. The UASB anaerobic reactor allows the evenly distributed wastewater to pass upward through the sludge bed, and anaerobic reaction occurs during the contact with the sludge bed;

[0039] (6) The effluent from the UASB anaerobic reactor enters the AAO biochemical system, where the microorganisms in the activated sludge remove most of the COD, BOD, ammonia nitrogen, total nitrogen, total phosphorus, and suspended matter in the sewage;

[0040] (7) The effluent from the AAO biochemical system enters the powdered activated carbon membrane bioreactor, where the powdered activated carbon is used to adsorb and remove the difficult-to-biodegrade COD in the sewage, and the saturated powdered activated carbon is separated by an immersed ultrafiltration membrane;

[0041] (8) The effluent from the powdered activated carbon membrane bioreactor enters the disinfection tank, where sodium hypochlorite solution is added for disinfection before being marked and discharged;

[0042] The sludge produced in each step enters the sludge storage tank and is then centrally dehydrated.

[0043] Specific:

[0044] Screen: Through the mechanical blocking effect of the screen, large particles of suspended impurities in the pre-prepared food industrial wastewater are separated and removed. Usually, the screen bar gap of this step is selected to be 1-3mm;

[0045] Inlet pump room: This step mainly provides hydraulic elevation for subsequent processes. Usually, the pump selected for this step is a submersible sewage pump. The typical value of the residence time in the inlet pump room is generally 0.05-1h;

[0046] Oil separator sedimentation tank: This step uses gravity to float the oil and fat in the water, and removes the suspended matter that is easy to settle. This step can be used to reuse the floating oil according to the process requirements of the enterprise. This step can remove a large amount of suspended matter and grease. The typical surface hydraulic load of the oil separator sedimentation tank is 1-2m 3 / (m 2 h), the stay time is 1-2h;

[0047] The regulating tank regulates the production wastewater of the pre-prepared food enterprise and homogenizes and equalizes the discharged wastewater to ensure the stable operation of the subsequent process. Usually, the hydraulic retention time of the regulating tank step is 8-10 hours. The regulating tank can be used as an emergency pool for accidents. The typical retention time of the regulating tank is 6-10 hours.

[0048] Dissolved air flotation tank: A large number of fine bubbles are generated in the water by pressurizing, so that the bubbles are attached to the suspended particles. Due to the low density of the adhesive body, they can float to the water surface to separate the water and suspended matter. The dissolved air flotation in this step uses an integrated skid-mounted equipment. In the flotation treatment process of the wastewater from the pre-prepared food enterprise, it is necessary to add coagulant PAC and flocculant PAM. The dosage of the agent is selected according to the suspended matter and total phosphorus concentration of the incoming water. Usually, the typical dosage of PAC in the wastewater of the pre-prepared food production enterprise is 50-450mg / L, and the typical dosage of PAM is 1-6mg / L. The choice of PAM is the first-class national standard product, with an alumina content of ≥28%. PAM is the first-class national standard product;

[0049] UASB anaerobic reactor: UASB anaerobic reactor allows evenly distributed wastewater to pass upward through the sludge bed, and anaerobic reaction occurs during the contact with the sludge bed. One of the most important equipment in the UASB reactor is the three-phase separator. The separation function of the three-phase separator is to separate water, gas and solid, collect and treat the gas, recycle the solid, and proceed to the next step after the liquid treatment. This step is the first key step in the treatment of pre-prepared food wastewater. This step is the key to removing pollutants and can efficiently and save land to treat high-concentration organic wastewater generated by pre-prepared food companies. According to the incoming water and process requirements, the influent COD value of this step is usually 1000-15000mg / L, SS≤500mg / L, and the COD removal rate through the UASB anaerobic reactor is typically ≥75%, and the volumetric load is typically 3-9kgCOD / (m3 ·d), the typical value of the excess sludge yield of this step is 0.07-0.1kgMLSS / kgCOD, and the effluent COD value of this step is usually 600-100mg / L, SS≤100mg / L. The use of this step is the key to efficiently treat pollutants in pre-prepared food wastewater.

[0050] AAO biochemical system: removes most of the COD, BOD, ammonia nitrogen, total nitrogen, total phosphorus, suspended matter and other pollutants in the sewage through the microorganisms in the activated sludge. After this step, the COD index in the pre-prepared food wastewater can be reduced to below 50mg / L, with a typical value of 40mg / L, the BOD index can be reduced to below 15mg / L, with a typical value of 8mg / L, the ammonia nitrogen index can be reduced to below 1mg / L, with a typical value of 0.5mg / L, the total nitrogen index can be reduced to below 20mg / L, with a typical value of 10mg / L, and the total phosphorus index can be reduced to below 3mg / L, with a typical value of 1mg / L. The operating parameters of the biochemical system may include: anoxic pool retention time: 8.5h; aerobic pool retention time: 13h; anoxic pool DO index ≤ 0.5mg / L typical The typical value is 0.3mg / L, the DO index of the aerobic pool is greater than 2mg / L, and the typical value is 2.5mg / L. The sludge yield is 0.6kgSS / kgBOD5; the BOD load of the biochemical system is 0.1409kgBOD5 / kgMLSS.d; the NH3-N load of the biochemical system is 0.044kgNH3-N / kgMLSS.d; the TN load of the biochemical system is 0.038kgTN / kgMLSS.d; the sludge return ratio is 67%, the maximum is 100%; the mixed liquor return ratio is 65.93%: the maximum is 150%; the sludge age is 14.5d; the sludge concentration is 2500-4500mg / L; SVI=150mL / g. If denitrification is required, the denitrification effect can be increased by adding an appropriate amount of carbon source.

[0051] Powdered activated carbon membrane bioreactor; Powdered activated carbon membrane bioreactor, using powdered activated carbon to adsorb and remove the difficult-to-biodegrade COD in sewage, using immersed ultrafiltration membrane to separate the saturated powdered activated carbon. After this step, the COD index in coal chemical wastewater can be reduced to below 20mg / L, and the typical value is 12mg / L. If the effluent index considers the total phosphorus index, coagulation and sedimentation can be added according to the process requirements to remove the total phosphorus. Powdered activated carbon process parameter selection; 100 mesh, methylene blue value> 12ml / 0.1g, iodine value> 800mg / g, ash content ≤ 8%. The ratio of activated carbon dosage to influent water volume is 100-300mg / L, and the activated carbon concentration in the bioreactor pool is within 30000mg / L. According to the changes in the incoming water quality, increasing the activated carbon concentration is beneficial to the anti-shock load of the pool body and the attachment of microorganisms. After the activated carbon adsorption is saturated, it can be discharged to the biological pool according to demand, improving the treatment load of the biochemical system and the sedimentation performance of the activated sludge, and finally it can be discharged from the system with the residual sludge. The submerged ultrafiltration membrane in the above-mentioned carbon membrane bioreactor is composed of multiple groups of membranes and stainless steel frames, aeration systems, and water inlet and outlet systems. The average flux during process operation is 15L / ㎡.h, and the gas-water ratio during operation is 10-15:1, which is mainly used for gas disturbance to wash away the activated carbon on the membrane surface. The above-mentioned submerged ultrafiltration membrane produces water for 8 minutes, backwashes for 2 minutes, and adds 100-500mg / L of effective chlorine sodium hypochlorite and 0.5% sodium citrate for online chemical washing to restore flux.

[0052] Disinfection pool effluent: Sodium hypochlorite solution is added to the disinfection pool for disinfection. The specific dosage can be selected based on the economic dosage according to the requirements of indicators such as effluent Escherichia coli.

[0053] Sludge dewatering: After the sludge in the sludge pool is dewatered, it is entrusted to a third-party unit with sludge treatment qualifications for disposal. A plate and frame filter press or a high-pressure belt filter press is selected to make the solid content of the sludge greater than or equal to 30% in order to save treatment costs.

[0054] Example 2

[0055] Taking the wastewater from a certain pre-prepared food industrial park as an example, the method of the present invention is used for treatment:

[0056] 1. The designed inlet and outlet water quality is as follows:

[0057]

[0058]

[0059] 2. Process parameters

[0060] Grid machine b = 3mm

[0061] The water intake pump room residence time is 0.5h, and K (peak factor) is 1.8.

[0062] The hydraulic load on the surface of the oil separation sedimentation tank is 1.5m 3 / (m 2 ·h), residence time 1h.

[0063] The dissolved air flotation tank is added with coagulant PAC and flocculant PAM, with a PAC dosage of 200 mg / L and a PAM dosage of 3 mg / L. The PAC is a first-class product according to national standards, with an alumina content of ≥28%, and the PAM is a first-class product according to national standards.

[0064] Retention time in equalization tank: 8.2h.

[0065] The UASB anaerobic reactor has a removal rate of 70% and a sludge production coefficient of 0.075 kg MLSS / kg COD.

[0066] AO anoxic pool retention time: 5.5h; aerobic pool retention time: 10.7h; total retention time: 16.2h; sludge yield: 0.5kgSS / kgBOD5; biochemical system BOD5 load: 0.107kgBOD5 / kgMLSS.d; biochemical system NH3-N load: 0.0374kgNH3-N / kgMLSS.d; biochemical system TN load: 0.0356kgTN / kgMLSS.d; sludge return ratio: 218%, the maximum can be greater than 300%, the MBR membrane pool returns to the aerobic pool, and the sludge return volume can be used to form a completely mixed aerobic pool; mixed liquor return ratio: 69.92%, the maximum is 100%, the denitrification mixed liquor return volume is 1608.16m 3 / d, the return mode is from the aerobic tank to the anoxic tank; sludge age: 11.9-14.5d; designed sludge concentration of the biochemical system: 4000mg / L; maximum oxygen demand for biochemical reaction: 1007.85kgO2 / d; required air volume: 19461.89m 3 / d, gas-water ratio 8.5:1.

[0067] SVI=150mL / g.

[0068] 3. Powdered activated carbon membrane pool

[0069] Wood powder activated carbon iodine value ≥ 800mg / g, methylene blue value ≥ 14ml / 0.1g, particle size 200-325 mesh, ash content ≤ 10%, COD adsorption value 0.2-0.25gCOD / activated carbon g. Immersed ultrafiltration membrane flux ≥ 15L / m 2 .h. Retention time 3.2h. Effluent COD ≤ 50mg / L.

[0070] The above is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and changes can be made without departing from the principle of the present invention, and these improvements and changes are also regarded as the protection scope of the present invention.

Claims

1. An efficient method for treating wastewater from prepared food, characterized in that: The following steps are involved: (1) The pre-prepared food wastewater is pre-treated through a screen to separate and remove large suspended impurities before flowing into the water inlet pump room; (2) The pre-treated wastewater is transported to the oil separation sedimentation tank through the water intake pump room to separate oily substances and easily precipitated suspended solids; (3) The effluent from the oil separation sedimentation tank enters the regulating tank for average and volume treatment; (4) The effluent from the regulating tank enters the dissolved air flotation tank, where flocculants are added to generate a large number of fine bubbles in the water by pressurizing it, so that the bubbles attach to the suspended particles, thereby separating the water and the suspended matter; (5) The effluent from the dissolved air flotation tank enters the UASB anaerobic reactor, causing the wastewater to pass upward through the sludge bed, where anaerobic reactions occur during contact with the sludge bed; (6) The effluent from the UASB anaerobic reactor enters the AAO biochemical system, where the microorganisms in the activated sludge remove most of the COD, BOD, ammonia nitrogen, total nitrogen, total phosphorus, and suspended matter in the sewage; (7) The effluent from the AAO biochemical system enters the powdered activated carbon membrane bioreactor, where the powdered activated carbon is used to adsorb and remove the difficult-to-biodegrade COD in the sewage, and the saturated powdered activated carbon is separated by an immersed ultrafiltration membrane; (8) The effluent from the powdered activated carbon membrane bioreactor enters the disinfection tank, where disinfectant is added for disinfection before being discharged in compliance with the standards.

2. The efficient treatment method for pre-prepared food wastewater according to claim 1 is characterized in that: In step (1), the grid bar gap of the grid is selected to be 1-3 mm.

3. The efficient treatment method for pre-prepared food wastewater according to claim 1 is characterized in that: In step (1), the water pump of the water inlet pump room is selected as a submersible sewage pump, and the typical value of the water inlet pump room residence time is 0.05-1h.

4. The efficient treatment method for pre-prepared food wastewater according to claim 1 is characterized in that: In step (2), the typical hydraulic load of the designed surface of the oil separation sedimentation tank is 1-2m 3 / m 2 ·h, the residence time is 1-2h, and the generated precipitated sludge enters the sludge storage tank.

5. The efficient treatment method for pre-prepared food wastewater according to claim 1 is characterized in that: In step (3), the hydraulic retention time of the regulating pond is adjusted to 8-10 hours.

6. The efficient method for treating wastewater from prepared food according to claim 1, characterized in that: In step (4), the flocculants are PAC and PAM, the typical dosage of PAC is 50-450 mg / L, the alumina content is ≥28%, the typical dosage of PAM is 1-6 mg / L, and the generated flotation sludge enters the sludge storage tank.

7. The efficient treatment method for pre-prepared food wastewater according to claim 1 is characterized in that: In step (5), the typical value of the residual sludge yield is 0.07-0.1kgMLSS / kgCOD, the effluent COD value is 600-100mg / L, SS≤100mg / L, and the residual sludge produced enters the sludge storage tank.

8. The efficient method for treating wastewater from prepared food according to claim 1, characterized in that: In step (6), the operating parameters of the AAO biochemical system are: anoxic tank residence time: 4-10h; aerobic tank residence time: 10-15h; anoxic tank DO index ≤ 0.5mg / L, aerobic tank DO index > 2mg / L, sludge yield: 0.3-0.6kgSS / kgBOD5; biochemical system BOD5 load: 0.05-0.15kgBOD5 / kgMLSS.d; biochemical system NH3-N load: 0.02-0.05kgNH3-N / kgMLSS.d; biochemical system TN load: 0.03-0.04kgTN / kgMLSS.d; sludge return ratio > 67%; mixed liquor return ratio > 65%; sludge age: 10-14.5 days; sludge concentration: 2500-4500mg / L; sludge volume index SVI: 100-150mL / g.

9. The efficient method for treating wastewater from prepared food according to claim 1, characterized in that: In step (7), the process parameters of powdered activated carbon are: 100-400 mesh, methylene blue value ≥12 ml / 0.1 g, iodine value ≥800 mg / g, ash content ≤8%, the ratio of activated carbon dosage to influent water volume is 100-300 mg / L, and the activated carbon concentration in the bioreactor pool is within 30000 mg / L.

10. The efficient treatment method for pre-prepared food wastewater according to claim 1, characterized in that: In step (7), the average flux of the immersed ultrafiltration membrane during process operation is 12-18 L / ㎡.h, the gas-water ratio during operation is 10-15:1, water production is 6-10 min, backwashing is 1-3 min, and online chemical washing is performed by adding 100-500 mg / L of effective chlorine sodium hypochlorite and 0.5% sodium citrate to recover the flux.

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