TW201540676A - Food industry combined wastewater treatment method - Google Patents

Abstract

The present invention provides a method for treating complex combined wastewater which is collected from various sources in the food industry. The combined wastewater contains impurities of suspended solids, organic substance, ammonia nitrogen, and total nitrogen, and may further contain total phosphorus; however, it basically contains no or little grease that will not interfere with microbial treatment. First of all, the combined wastewater is subjected to a treatment for removing suspended solids; next, conducting a decomposition treatment with anaerobic microorganisms to make the contained organic impurities partly decompose; then, conducting a decomposition treatment by combining oxygen-free or aerobic microorganisms to make the residual organic substance, ammonia nitrogen, total nitrogen and possibly existing total phosphorus further removed, followed by using a thin film for solid-liquid separation to obtain treated water capable of discharging safely or recycling. This invention further includes steps for individual treatment of grease-containing wastewater and an integration of this individually treated wastewater into the combined wastewater treatment method. This invention also provides a method for treating combined wastewater containing large amount of grease, in which an air-floatation and grease-removing means is further incorporated.

Description

Food industry comprehensive wastewater treatment method

The invention relates to a method for treating complex wastewater in the food industry, which can remove impurities such as oil, suspended solids, organic matter, ammonia nitrogen, total nitrogen, and total phosphorus in the waste water, so that the treated water can be safely discharged or recycled. The purpose.

Due to insufficient water resources and serious pollution of natural water bodies, current international environmental protection regulations are to increase or tighten the emission standards of pollutants, and at the same time improve the requirements for water recycling. China is a region with serious water scarcity and serious pollution. Green development is the focus of national governance. It aims to gradually improve environmental protection standards for key industries and key regions. In addition to national-level comprehensive emission standards and water recovery rate requirements, local regions have priority over countries. Set stricter standards to suit the characteristics of local industry. At present, priority is given to upgrading the food, chemical, paper, steel, electroplating, printing and dyeing industries, and focusing on controlling four major pollutants: chemical oxygen demand, ammonia nitrogen, total nitrogen and total phosphorus.

Wastewater in the food industry is characterized by high complexity and organic pollution. It generally contains high concentrations of organic matter (BOD, COD concentration up to several thousand ppm), high suspended solids contamination (SS usually exceeds 1,000 ppm), and also contains hundreds of ppm of concentrated Degree of oil, ammonia, total nitrogen, and even total phosphorus and other pollution. Due to the large scope of the food industry, due to different factors such as products, processes, seasons and regions, the wastewater discharged is not the same, resulting in a large difference in wastewater pollution characteristics and pollution. Table 1 illustrates the water quality range of the integrated wastewater from the food industry.

Taiwan Patent Invention 313187 discloses a wastewater treatment system containing organic pollutants, comprising an anaerobic reaction tank, an aerobic reaction tank, and a membrane separation tank; wherein the aerobic reaction tank is disposed in an anaerobic reaction tank Thereafter, the film separation tank is disposed after the aerobic reaction tank, and the system removes organic pollutants in the wastewater by biological treatment, and separates the solid-liquid two phases by a membrane. The focus of the prior invention is to solve the problem of scale and scale on the surface of the film, especially the aerobic reaction tank can increase the pH of the water to be treated, and the metal ions therein form carbonic acid crystal particles, and biogel The metal carbonate crystal particles are embedded in the rubber feathers of the aerobic microorganism to reduce the tendency of the metal crystals to form scale on the film of the membrane separation tank. The previous examples only used glucose and sodium acetate as artificial substrates for experiments. There was no mention of the ability to simultaneously treat complex wastewaters containing oils, suspended solids, organic matter, ammonia nitrogen, total nitrogen and total phosphorus.

Taiwan Patent No. 316,923 discloses a wastewater treatment system for removing carbon, nitrogen and phosphorus pollutants from waste water, the process comprising a multifunctional biological reaction tank, an anaerobic reaction tank, an aerobic reaction tank, and a membrane separation tank; The patent utilizes a combination of specific bacterial phases in a biological tank to remove carbon, nitrogen and phosphorus contaminants in low to medium concentrations in domestic sewage. The constituent bacteria phase defined by the first tank multifunctional biological tank comprises denitrifying bacteria, phosphorus accumulating bacteria and methanogens, and the gas-solid liquid three-phase separator is not required in the anaerobic reaction tank, and the source of the microbial sludge is It is obtained by refluxing the mixture of the fourth tank film tank. Since the mixture of the fourth tank membrane tank is from the third tank aerobic nitrification tank which needs sufficient aeration, the operating conditions and functions of the multifunctional biological tank and the UASB The anaerobic reaction tank is different.

The main purpose of the present invention is to provide a comprehensive wastewater for food industry The treatment method is for the purpose of safe discharge or recycling. The integrated wastewater contains impurities such as suspended solids, organic matter, ammonia nitrogen, and total nitrogen, and may further contain total phosphorus but substantially no or only a small amount of oil that does not interfere with microbial treatment.

The wastewater treatment method provided by the invention comprises the following steps: a) treating a comprehensive wastewater containing suspended solids, organic matter, ammonia nitrogen and total nitrogen to remove suspended solids, wherein the comprehensive wastewater selectively further contains total phosphorus or a small amount. The following steps b) and c) microbial treated oils and fats; b) the anaerobic microbial decomposition treatment of the waste water having a reduced suspended solid content from step a), such that the organic impurities contained therein are partially decomposed; Treating waste water having reduced organic matter content from step b) in a manner of anaerobic microbial decomposition and aerobic microbial decomposition, so that impurities remaining therein are further degraded; and d) using a membrane filtration device for step c The outflow water is subjected to solid-liquid separation, so that the microbial sludge is trapped in the membrane filtration device, and the water is discharged or discharged from the membrane filtration device, wherein the water containing the microbial sludge trapped in the membrane filtration device is Returning to the tank of the anaerobic microorganism decomposition at a ratio of 0.5-15 times (preferably 3-7 times) to the outflow water of step b) The main microbial sludge source of step c) for the decomposition of anaerobic microorganisms and aerobic microbial decomposition.

Depending on the purpose of water resource recycling and reuse, the recovered or discharged water discharged from the above step d) may be subjected to reverse osmosis (RO) equipment. Recycling water quality refining treatment.

Preferably, the anaerobic microbial decomposition of step b) is carried out in an upflow anaerobic microbial reaction tank (UASB), and the UASB anaerobic microbial reaction tank is equipped with a gas-liquid-solid three-phase separator to trap microorganisms. The sludge bed having the characteristics of granulated sludge formed under the tank is used as an anaerobic microbial reaction zone, and is not required to be provided by the back membrane filtration device to return sludge. The wastewater from which the suspended solids content of step a) is reduced is retained in the anaerobic microbial reaction tank for a period of time, so that the organic impurities in the wastewater are decomposed by the microorganisms in the anaerobic sludge reaction zone during the residence time. The biological sludge in the reaction tank is liquefied after being trapped by the gas-liquid-solid three-phase separator.

Preferably, the step c) is carried out in the form of an anaerobic microbial decomposition and aerobic microbial decomposition followed by a series connection in an anaerobic microbial reaction tank and an aerobic microbial reaction tank, respectively, from step b). The wastewater with reduced organic matter content is retained in the anaerobic microbial reaction tank and the aerobic microbial reaction tank for a period of time, so that impurities such as organic carbon, oil, ammonia, total nitrogen, and total phosphorus (if present) remain in the wastewater. During this residence time, it is decomposed by the biochemical metabolism of the anaerobic microorganisms and aerobic microorganisms in the biological tank.

The integrated wastewater of step a) can be collected from a number of food industry process wastewaters, but the integrated wastewater contains no or only a small amount of oil that does not interfere with microbial treatment. If the food industry process simultaneously produces another waste water containing a high amount of oil, preferably the process of the present invention further comprises the step of separately treating the simultaneously produced another grease-containing wastewater.

The grease-containing wastewater is subjected to an air flotation treatment, including After adding a proper amount of flocculant to the oil-containing wastewater, a gas-floating (DAF) device is used to reduce the oil content in the oil-containing wastewater by dissolved air flotation, and the waste water having the reduced oil content and the suspended solids discharged from the aforementioned step a) are The reduced wastewater is combined with steps b), c) and d).

If the food industry process produces a solid waste-containing wastewater containing suspended solids, organic matter, ammonia nitrogen, total nitrogen, and high oil content, and may further contain total phosphorus, the present invention also provides a large amount of oil and fat. A method for treating integrated wastewater, which is subjected to an air flotation method before or at the same time as step a).

Figure 1. Block diagram of the integrated wastewater treatment and discharge system (wastewater discharge) of the present invention.

Figure 2 is a block diagram of the integrated wastewater recovery and treatment system (water recovery) of the present invention.

Fig. 3 is a block diagram showing the process of the recovery and treatment system (water recovery) of the integrated wastewater containing a large amount of oil and fat according to the present invention.

The food industry process integrated wastewater treatment system of the invention is used for the purpose of wastewater discharge (also can be recycled and reused for a specific use with a loose water quality standard), as shown in Fig. 1, mainly including a gas floatation and degreasing device, Suspended solids device, an anaerobic microbial reaction tank, an anaerobic microbial tank, an aerobic Microbial tank, and a membrane filtration device.

The integrated wastewater can be made up of several food industry process wastewaters. The integrated wastewater contains impurities such as suspended solids, organic matter, ammonia nitrogen, and total nitrogen, and may further contain total phosphorus but substantially no or only a small amount of oil that does not interfere with microbial treatment. The integrated wastewater is introduced into the de-suspended solids unit for the purpose of removing non-dissolving particulate contamination from the wastewater, reducing the load on subsequent biological systems, and avoiding the risk of clogging of the membrane filtration device. The desuspended solids device is different depending on the specific gravity of the suspended solids: if only a solid having a large specific gravity (specific gravity > 1) is used, a gravity settling tank is used; if only a solid having a small specific gravity (specific gravity < 1) is used, A pressurized air flotation device is used; if a solid having a specific gravity of less than 1 to more than 1 is simultaneously used, the pressurized air flotation device is used first and then the gravity sedimentation tank is used.

The effluent water of the desuspended solids device is introduced into the anaerobic microbial reaction tank, and the purpose of the anaerobic microbial reaction tank is to metabolically decompose organic pollutants in the wastewater, and the anaerobic microorganisms are removed through the degreasing and de-suspending solid waste water. The reaction tank stays for a period of time, so that the macromolecules and the longer-chain organic matter in the wastewater are broken down by the broken bonds. Preferably, the anaerobic microbial decomposition is carried out in an upflow anaerobic microbial reaction tank (UASB) having the characteristics of granulated sludge.

The effluent water of the anaerobic microbial reaction tank is then passed through the anaerobic microbial tank and the aerobic microbial tank, wherein the residual organic carbon, oil, ammonia, total nitrogen, total phosphorus and other impurities are completely degraded by the anaerobic microorganism treatment. Remove. After the aerobic microbial tank is equipped with a membrane filtration device or the membrane filtration device is disposed in the outlet of the aerobic microbial tank, the treated wastewater is subjected to solid-liquid separation to trap the microbial sludge in the membrane filtration device or Oxygen microorganism In the tank, the trapped concentrated sludge water must be refluxed to the anaerobic microbial tank at a specific ratio to maintain high microbial density and reactivity in the microbial tank. The outflow water treated by the microbial tank is filtered by the membrane device and discharged to recover or discharge water.

The food industry process also produces another wastewater containing high oil content. When the oily wastewater contains the amount of oil pollution (concentration x water volume), the anaerobic microorganisms, anaerobic microorganisms and aerobic microorganisms are decomposed relative to the comprehensive wastewater. When the method cannot be undertaken, the grease-containing wastewater is separately subjected to a gas floatation and degreasing treatment, as shown in Fig. 1, which is introduced into the air flotation and degreasing device, wherein an appropriate amount of flocculating agent is added to the grease-containing wastewater and an air flotation is used. (DAF) device, which uses dissolved air to reduce the amount of oil in the waste water. The waste water having a reduced oil content is introduced into the desuspended solids apparatus, and the same desuspended solids treatment and subsequent treatment are simultaneously performed with the integrated wastewater.

If the food industry process does not produce another wastewater containing high oil content, or the oil pollution amount (concentration x water volume) of the oil-containing wastewater is as small as the anaerobic microorganism, the anaerobic microorganism and the aerobic When the microbial decomposition mode can bear, it can be combined with the integrated wastewater. At this time, the air flotation and degreasing device in Fig. 1 may not be set or omitted.

Figure 2 shows the treatment system for the integrated wastewater industry of the food industry of the present invention for wastewater recovery, which has the same structure as Figure 1 except that a reverse osmosis system is added. For the purpose of recycling and reuse of water resources, the water discharged from the membrane filtration device can be purified by a reverse osmosis (RO) system. If the recovered water is used in high-end applications such as process water, the outflow water treated by the reverse osmosis system may be subjected to further refining treatment. The refining system may AOP, the system comprising a UV ozone UV or H ₂ O ₂ system; and means for selectively and placed in a final active carbon.

If the food industry process produces a waste containing solids such as suspended solids, organic matter, ammonia nitrogen, total nitrogen, and high oil and fat, and may further contain total phosphorus containing grease, the present invention also provides a large amount of oil and fat. The method of treating integrated wastewater. Figure 3 shows a wastewater treatment system suitable for use in this treatment process.

If the specific gravity of the suspended solids contained in the oil-containing integrated wastewater is <1, the oil-containing integrated wastewater is introduced into the air-floating oil-removing and suspended solid-state device of FIG. The anaerobic microbial reaction tank was subjected to the same treatment procedure as shown in Fig. 2. In the air flotation degreasing and suspending solids device, an appropriate amount of flocculating agent is added to the oil-containing integrated wastewater, and an air flotation (DAF) device is used to reduce the content of oil and suspended solids in the wastewater by dissolved air flotation.

If the specific gravity of the suspended solids contained in the oil-containing integrated wastewater is greater than 1, the oil-containing integrated wastewater is degassed after being introduced into the air-floating degreasing and suspended solids device of FIG. 3, and the discharged water is introduced into a gravity sedimentation device. . The gravity sedimentation device is retained for a period of time to precipitate a solid having a specific gravity greater than 1 in the wastewater, and the upper layer of the outflow water is introduced into the anaerobic microorganism reaction tank, and the same treatment flow as shown in FIG. 2 is performed. In the air flotation degreasing and suspending solid device, an appropriate amount of flocculating agent is added to the oil-containing integrated wastewater, and a gas floating (DAF) device is used to reduce the oil content in the wastewater by dissolving air flotation.

If the specific gravity of the suspended solids contained in the oil-containing integrated wastewater is greater than 1 or from less than 1 to more than 1, the comprehensive wastewater containing the grease is The air flotation degreasing and the suspended solids device introduced in Fig. 3 are simultaneously degreased and suspended, and the outflow water is introduced into a gravity sedimentation device. The gravity sedimentation device is retained for a period of time to precipitate a solid having a specific gravity greater than 1 in the wastewater, and the upper layer of the outflow water is introduced into the anaerobic microorganism reaction tank, and the same treatment flow as shown in FIG. 2 is performed.

The invention is further understood by the following examples, which are intended to be illustrative only and not to limit the scope of the invention.

Example 1: Testing wastewater to a test that meets emission standards

Wastewater source: A food factory wastewater, the main products are dairy and ice products. The wastewater source includes process wastewater and domestic sewage in the plant. The actual wastewater of the plant is shown in Table 2.

After adjusting the pH and adding flocculant, the original waste water is used to remove grease and suspended solids by pressurized air floatation unit; the outlet liquid of the air floatation unit is introduced into the anaerobic microbial tank, and the anaerobic microbial tank has a residence time of 16 hours; the anaerobic microbial tank is discharged. The running water is then introduced into the anaerobic/aerobic microbial tank for a total residence time of 20 hours. Finally, the MBR membrane unit is used for solid-liquid separation, and the membrane tank is refluxed 4~5Q to the anaerobic/aerobic microbial tank. This test uses continuous inflow operation.

After the whole plant wastewater is treated by the above process, the suspended solids (SS) outflow concentration is <1 mg/L (removal rate >99%), and the oil (Oil) outflow concentration is 5-8 mg/L (removal rate >96.4%). Chemical oxygen demand (COD) outflow concentration 25~56mg/L (removal rate >98.8%), ammonia nitrogen (NH ₄ ⁺ -N) outflow concentration 2.5~6.8mg/L (removal rate >94.5%), total ammonia The (TKN) outflow concentration was 25.6~27.5mg/L (removal rate >80%), and the phosphate (PO ₄ ^3- ) outflow concentration was <1.5mg/L (removal rate >96.7%). The key water quality projects of the membrane filtration out of the water can meet the GB 1978-1996 first-class standard for comprehensive wastewater discharge.

Example 2: Testing Wastewater to Recycling and Recycling

Wastewater source: A food factory wastewater, the main products are dairy and ice products. The wastewater source includes process wastewater and domestic sewage in the plant. The actual wastewater of the plant is shown in Table 2. The test procedure is to add a reverse osmosis (RO) device after the system used in the first embodiment, and the membrane is filtered out of water and further purified by RO reverse osmosis, so that the treated water quality can achieve high-order recycling and reuse purposes.

After adjusting the pH and adding flocculant, the original waste water is used to remove grease and suspended solids by pressurized air floatation unit; the outlet liquid of the air floatation unit is introduced into the anaerobic microbial tank, and the anaerobic microbial tank has a residence time of 16 hours; the anaerobic microbial tank is discharged. The running water is then introduced into the anaerobic/aerobic microbial tank for a total residence time of 20 hours; The MBR membrane unit is subjected to solid-liquid separation; the water produced by the MBR membrane unit is further introduced into a reverse osmosis (RO) unit for further purification. This test uses continuous inflow operation.

After the actual wastewater treatment in the factory is treated by the above process, the water quality of RO water production is as follows: suspended solids (SS) and turbidity are not detected, chemical oxygen demand (CODcr) is not detected, and total organic carbon (TOC) is 0.58 mg/L. The concentration of ammonia nitrogen (NH ₄ ⁺ -N) was 0.5 mg/L, the concentration of total ammonia (TKN) was 1.8 mg/L, the concentration of nitrate nitrogen (NO ₃ ^- -N) was <0.8 mg/L, and the conductivity was 184 μS/cm. According to the test data, after the treatment process, the water quality can obtain better water quality than the general municipal tap water, and can be used as a tap water supplement water source.

Claims (11)

The invention relates to a method for treating comprehensive wastewater, comprising the steps of: a) treating a comprehensive wastewater containing suspended solids, organic matter, ammonia nitrogen and total nitrogen to remove suspended solids, wherein the comprehensive wastewater selectively further contains total phosphorus or a small amount does not hinder The following steps b) and c) microbial treated oil; b) treating the wastewater having a reduced suspended solids content from step a) in an anaerobic microbial decomposition such that the organic impurities contained therein are partially decomposed; and c) The anaerobic microbial decomposition and the aerobic microbial decomposition are successively connected in series to treat the waste water having reduced organic matter content from the step b), so that the impurities remaining therein are further degraded; and d) the membrane filtration device is directed to the step c) The outflow water is subjected to solid-liquid separation, so that the microbial sludge is trapped in the membrane filtration device, and the water is discharged or discharged from the membrane filtration device, wherein the water containing the microbial sludge trapped in the membrane filtration device is 0.5. -15 times the proportion of the outflow water of step b) is returned to the tank of the anaerobic microorganism decomposition to serve as the anaerobic microbial of step c) The main source of microbial sludge for decomposition and aerobic microbial decomposition. The method of claim 1, wherein the ratio is 3-7 times. The method of claim 1, further comprising: e) reverse osmosis treating the recovered or discharged water discharged by the aforementioned step d). The method of claim 1, wherein the anaerobic microbial decomposition of step b) is carried out in an upflow anaerobic microbial reaction tank (UASB), and the UASB anaerobic microbial reaction tank is equipped with a gas-liquid-solid three-phase separator. The sludge is trapped under the tank to form a sludge bed having the characteristics of granulated sludge as an anaerobic microbial reaction zone. The method of claim 1, wherein the integrated wastewater of step a) is collected from a plurality of food industry process wastewater. The method of claim 1, further comprising the step of performing an individual air flotation treatment on the other grease-containing wastewater, comprising adding an appropriate amount of flocculating agent to the oil-containing wastewater, and using an air flotation (DAF) device to dissolve The air flotation reduces the oil content in the grease-containing wastewater, and the wastewater having the reduced oil content is combined with the waste water having the reduced suspended solid content flowing out in the above step a) to carry out steps b), c) and d). The method of claim 1, wherein the removing the suspended solids in step a) comprises: if the integrated wastewater contains only solids having a specific gravity > 1 , a gravity settling tank is used; if the integrated wastewater contains only solids having a specific gravity of <1, A pressurized air flotation device is used; if the integrated wastewater contains solids having a specific gravity of less than 1 to more than 1, the pressurized air flotation device is used first and then the gravity sedimentation tank is used. A method for treating a comprehensive wastewater containing fats and oils, comprising the steps of: a1) if the specific gravity of the suspended solids contained in the comprehensive wastewater containing oil and fat is <1, then The oil-containing integrated wastewater is simultaneously subjected to degreasing and suspended solids treatment, and comprises adding a flocculating agent to the oil-containing comprehensive wastewater and using an air flotation device to reduce the content of oil and suspended solids in the waste water by dissolving air flotation, the grease and suspension The outflow water having a reduced solid content is introduced into the step b) for the anaerobic microbial decomposition treatment; a2) if the specific gravity of the suspended solids contained in the oil-containing integrated wastewater is greater than 1, the flocculant is added to the grease-containing integrated wastewater and one gas is used. The floating device reduces the oil content in the waste water by dissolved air flotation, and the outflow water whose oil content is reduced is introduced into a gravity sedimentation device, and the gravity sedimentation device is retained for a period of time to cause the solids having a specific gravity greater than 1 in the wastewater to settle, and the upper layer is discharged. The flowing water is introduced into the step b) for the anaerobic microbial decomposition treatment; or a3) if the specific gravity of the suspended solids contained in the oil-containing integrated wastewater is from less than 1 to more than 1, the oil-containing integrated wastewater is simultaneously degreased. In addition to the suspended solids treatment, the flocculant is added to the synthetic wastewater containing grease and an air flotation device is used to dissolve the air flotation The content of oil and suspended solids in the water is reduced, and the outflow water with reduced oil and suspended solid content is introduced into a gravity sedimentation device, and the gravity sedimentation device is retained for a period of time to precipitate solids having a specific gravity greater than 1 in the wastewater, and the upper layer of the outflow water is introduced into the step. b) performing anaerobic microbial decomposition treatment; b) treating waste water having a reduced suspended solid content from step a) in an anaerobic microbial decomposition manner, so that organic impurities contained therein are partially decomposed; and c) anaerobic The microbial decomposition and the aerobic microbial decomposition are successively connected in series to treat the wastewater from which the organic matter impurity content of step b) is reduced, so that the impurities remaining therein are further degraded; and d) the membrane filtration device for the outflow water from step c) Solid solution Separating, the microbial sludge is trapped in the membrane filtration device, and the water is discharged or discharged from the membrane filtration device, wherein the water containing the microbial sludge trapped in the membrane filtration device is 0.5-15 times The proportion of b) outflow water is returned to the tank in which the anaerobic microorganism is decomposed as a source of main microbial sludge for the decomposition of anaerobic microorganisms and aerobic microbial decomposition of step c). The method of claim 8, wherein the ratio is 3-7 times. The method of claim 8, further comprising: e) reverse osmosis treating the recovered or discharged water discharged by the aforementioned step d). The method of claim 8, wherein the anaerobic microbial decomposition of step b) is carried out in an upflow anaerobic microbial reaction tank (UASB), and the UASB anaerobic microbial reaction tank is equipped with a gas-liquid-solid three-phase separator. The sludge is trapped under the tank to form a sludge bed having the characteristics of granulated sludge as an anaerobic microbial reaction zone.