CN102249498B - Biochemical treatment method for waste water from small and medium-sized starch factories - Google Patents

Abstract

The invention discloses a biochemical treatment method for wastewater from small and medium starch factories. First, organic flocculant and inorganic flocculant are added to the wastewater for stirring, and flocs are formed in the mixed solution, and then the stirred mixed solution is separated by air flotation in an air flotation tank, and the suspended solids in the wastewater are separated, and the separated effluent Carry out filtration and dehydration, obtain starch protein and filtrate after dehydration; import the filtrate into IC reactor for biochemical treatment, import the liquid after biochemical treatment into MBR membrane bioreactor for separation, and dry the sludge obtained after separation Reuse, the obtained supernatant meets the national sewage discharge standard, and can be directly discharged or recycled. A large amount of starch wastewater can be effectively treated by the method of the invention, and starch protein and biogas can be recovered during the wastewater treatment process, so that resources can be utilized to the greatest extent, thereby achieving remarkable economic and environmental benefits.

Description

Biochemical treatment method of wastewater from small and medium starch factories

technical field

The invention relates to a wastewater treatment method, in particular to a biochemical treatment method for medium and small starch factory wastewater.

Background technique

Starch is an important industrial raw material. In addition to food and processed food, starch is widely used in industries such as textile, papermaking, medicine, fermentation, casting, adhesive, chemical industry, machinery and drilling. However, in the process of starch processing, a large amount of high-concentration acidic organic wastewater will be produced. The organic wastewater contains a large amount of residual starch, glucose, fructose, maltose and other carbohydrates, protein and organic acids, etc., which is easy to be corrupted and smelly, and the chemical oxygen demand COD The content is usually between 1000-30000mg/L; in addition, the concentration of total nitrogen and phosphate in starch wastewater is high, which is one of the most polluted wastewater in the food industry.

At present, China produces more than 3 million tons of starch annually. According to the existing processing technology, an average of 1 ton of starch produced produces ^10-20m3 of wastewater. Starch wastewater itself is non-toxic, and its pollutants are mainly carbohydrates, proteins, fats, etc. Naturally generated organic matter is easily corrupted and fermented, making the water black and smelly. Dissolved oxygen in the water will be consumed when discharged into the river, which will promote the reproduction of algae and aquatic plants. When the amount of starch wastewater is large, the river will be severely hypoxic and anaerobic. It emits a foul odor, which may suffocate aquatic animals such as fish, shrimp, and shellfish. Therefore, the treatment of starch wastewater has become a very serious problem faced by starch manufacturers in my country.

At present, the existing methods for the treatment of starch wastewater at home and abroad mainly include physical and chemical methods and biological methods.

1. Physicochemical method: mainly includes flocculation precipitation method and combined process method consisting of flocculation and adsorption. Although the physical and chemical method has a small investment, the operating cost is high, and it is difficult for the effluent to meet the discharge standard.

2. Biological method: mainly includes aerobic biological method, anaerobic biological method and photosynthetic bacteria method, etc. Biological treatment method has attracted the attention of environmental engineering circles because of its advantages of low cost, low energy consumption, and less residual sludge. .

Aspect the treatment starch wastewater, main prior art is as follows:

In 1999, relevant technicians of the Food Machinery Research Institute of the my country Agricultural Machinery Research Institute put forward "A Brief Discussion on the Sewage Treatment Scheme of Small and Medium-sized Potato Starch Plants". The level and wastewater discharge situation, the anaerobic-aerobic biochemical treatment method was proposed, and the technical scheme and process flow of the sewage treatment for the wastewater discharge of the potato starch factory with an annual output of 5000 tons were introduced. The starch wastewater treatment method is outdated, and the treated wastewater may cause secondary pollution; and the treated wastewater still contains some valuable resources, and the discharge of the wastewater causes a waste of valuable resources.

In addition, in the existing wastewater treatment technology, the sediment from the cornstarch wastewater is used to feed pigs, chickens, etc. after being precipitated by the grid, and the wastewater is discharged into the oxidation pond for natural fermentation for 1 to 2 days, and then discharged into the water hyacinth pond for purification for 7 days , and then discharged into the Xiluping Pond for purification for 7 days to meet the water quality standard for farmland irrigation. This part of the water is used to irrigate rice fields, fruit trees and vegetables, etc. Through this process, resources are reused. This treatment method has low technical content, and some resources in the waste water are still wasted.

Contents of the invention

The technical problem to be solved by the present invention is to provide a biochemical treatment method for wastewater from small and medium-sized starch factories. Through the method of the invention, a large amount of starch wastewater can be effectively treated, and its resources can be utilized to the greatest extent, thereby achieving remarkable economic and environmental benefits.

In order to solve the above problems, the technical solution adopted in the present invention is:

The present invention provides a kind of biochemical treatment method of wastewater from small and medium-sized starch factories, and described biochemical treatment method comprises the following steps:

a. First, add organic polymer flocculant polyacrylamide aqueous solution and inorganic flocculant polyaluminum chloride aqueous solution to starch wastewater, then stir and mix evenly to obtain a mixed solution, in which stable flocs are formed; the polypropylene The addition of the amide aqueous solution accounts for 2 to 4% of the total weight of the starch wastewater, and the addition of the polyaluminum chloride aqueous solution accounts for 1 to 2% of the total weight of the starch wastewater;

b. Import the uniform mixed solution in step a into the air flotation tank for air flotation separation. After the air flotation separation, separate the suspended matter flocs floating in the mixed solution to obtain the effluent, which is protein liquid. The effluent obtained through the separation of the air flotation tank That is, the protein liquid is dehydrated by filter press with a plate and frame filter press, and starch protein and filtrate are obtained after dehydration, and the obtained starch protein is dried by a tube bundle dryer to make protein feed;

c, the filtrate obtained after step b pressure filtration and dehydration is introduced into the IC anaerobic reactor for biochemical treatment, the filtrate to be obtained enters the first reaction zone of the reactor from the bottom of the IC anaerobic reactor, and passes through the bottom of the reactor The incoming water will dilute the imported filtrate, so that the organic matter in the filtrate can be fully reacted and degraded, and a large amount of biogas will be generated at the same time. Part of the generated biogas is collected by the three-phase separator in the lower layer of the IC anaerobic reactor; the other part of the biogas is entrained The filtrate and the sludge in the filtrate enter the second reaction zone, and the filtrate enters the gas-liquid separator in the second reaction zone under the entrainment of the biogas, and through the gas-liquid separation, the biogas is separated from the filtrate and collected. The remaining filtrate and sludge enter the bottom of the first reaction zone through the return pipe under the action of gravity;

d. The filtrate and sludge that enter the bottom of the first reaction zone after step c is treated by the IC anaerobic reactor are introduced into the MBR membrane bioreactor for separation, and the residence time in the MBR membrane bioreactor is 4 to 6 hours. During the separation process, the dissolved oxygen DO content is controlled to be 2-4 mg/L; the sludge obtained after separation by the MBR membrane bioreactor is dried and reused, and the supernatant obtained after separation is directly discharged or recycled.

According to the above biochemical treatment method for wastewater from small and medium-sized starch factories, the mass percent concentration of the polyacrylamide aqueous solution in step a is 0.05-0.1%; the mass percent concentration of the polyaluminum chloride aqueous solution is 5-10% .

According to the above-mentioned biochemical treatment method of wastewater from small and medium-sized starch factories, when the obtained starch protein is dried into a protein feed through a tube bundle dryer as described in step b, the drying conditions are normal pressure, a drying temperature of 40 to 50°C, and a drying time of 4～6h.

According to the biochemical treatment method of the above-mentioned small and medium-sized starch factory wastewater, the suspended matter flocculation floating in the mixed liquid is separated as described in step b, and the suspended matter SS and the chemical oxygen demand COD _cr in the starch wastewater after the suspended matter are separated The removal rates of those reached ≥80% and ≥30%, respectively.

According to the biochemical treatment method of the above-mentioned small and medium-sized starch factory wastewater, the IC anaerobic reactor described in step c adopts a tower reactor with a height-to-diameter ratio of 4～8:1; Downstream operation, the volume load is 17.0-22.0 kg COD _Cr /(m ³ ·d), the surface load in the sedimentation zone is 0.6 m ³ /(m ² ·h), and the hydraulic retention time in the reaction zone is 5-7 h.

According to the above biochemical treatment method for wastewater from small and medium-sized starch factories, the MBR membrane bioreactor in step d uses polypropylene hollow fiber membranes with a pore size of 0.1-0.45 μm.

According to the above-mentioned biochemical treatment method for wastewater from small and medium-sized starch factories, the removal rates of suspended matter SS and biochemical oxygen demand BOD ₅ in the supernatant obtained after step d is separated by MBR membrane bioreactor reach ≥90% and ≥85% respectively .

Positive beneficial effect of the present invention:

1. In the treatment method of the present invention, an organic flocculant and an inorganic flocculant are first added to the starch wastewater. Adding the inorganic flocculant can produce an electrical neutralization effect, so that the flocs in the wastewater are easy to agglomerate into larger flocs. The flocculant can make the flocs form relatively stable large flocs through adsorption and bridging, which is conducive to air flotation separation, so that the suspended solids SS and chemical oxygen demand COD _cr in the wastewater can be effectively separated. The present invention uses organic flocculant and inorganic flocculant in combination, not only has good flocculation effect, but also can greatly reduce the dosage of flocculant.

2. In the treatment process of the present invention, the waste water added with the flocculant is mixed evenly, separated by the air flotation tank, and the effluent obtained after the air flotation separation is filtered and dehydrated, and protein feed can be obtained after filtration. The suspended matter SS and The removal rates of COD _cr are over 80% and 30% respectively. According to calculations, at this stage, 5kg of protein feed can be extracted from each cubic meter of waste water, calculated at 1150 yuan/ton, and the benefit can be generated at 5.75 yuan per cubic meter of waste water; calculated on the basis of 5kg of protein feed extracted from waste water per cubic meter, protein feed can be extracted every year 3969 tons. In the process of biochemical treatment in the IC anaerobic reactor, 1.90 ^m3 of biogas can be recovered per cubic meter of waste water. Therefore, the present invention not only effectively treats a large amount of starch wastewater, but also obtains additional economic benefits. Therefore, the present invention has remarkable economic benefit and social benefit.

3. After the starch wastewater is treated by the method of the present invention, the suspended solids SS, chemical oxygen demand COD _cr and biochemical oxygen demand BOD ₅ in the starch wastewater are respectively reduced from the original content of 6862 mg/L, 14467 mg/L and 8672 mg/L To 86 mg/L, 127 mg/L and 22.5 mg/L, the effluent obtained after the final MBR membrane bioreactor separation, that is, the supernatant, can fully meet the "Sewage Comprehensive Discharge Standard" (GB8978-1996, first-level discharge standard). Therefore, the treatment method of the present invention not only effectively solves the problem of starch wastewater pollution, but also extracts protein feed and obtains biogas during the wastewater treatment process, and additionally obtains economic benefits. Therefore, the present invention has remarkable effects both in terms of economic benefits and social and environmental benefits.

4. After the starch wastewater is treated by adding flocculants, air flotation separation, IC anaerobic biochemical treatment and MBR membrane bioreactor, the final effluent quality of high-concentration starch wastewater can be better than the first-level discharge standard of GB8978-1996 , the final effluent can be reused for factory flushing water, toilet flushing water, greening water, and landscape water, which not only achieves the purpose of protecting the environment, but also saves conventional water resources, achieves good ecological benefits, and reduces fresh water. Reduced corporate water costs. Therefore, the present invention has significant economic benefits.

Fourth, the specific implementation method:

The following examples are only for further illustrating the present invention, and do not limit the content of the present invention.

Example 1:

A kind of biochemical treatment method of waste water of small and medium-sized starch factory of the present invention, the detailed steps of described biochemical treatment method are as follows:

a. First, add organic polymer flocculant polyacrylamide aqueous solution and inorganic flocculant polyaluminum chloride aqueous solution to starch wastewater, then stir and mix evenly to obtain a mixed solution, in which stable flocs are formed; the polypropylene The mass percent concentration of the amide aqueous solution is 0.08%, and the addition of the polyacrylamide aqueous solution accounts for 3% of the total weight of the starch wastewater; the mass percent concentration of the polyaluminum chloride aqueous solution is 8%, and the addition of the polyaluminum chloride aqueous solution The amount accounts for 1.5% of the total weight of starch wastewater;

b. Import the uniformly mixed liquid in step a into the air flotation tank for air flotation separation. After air flotation separation, separate the suspended matter flocs floating in the mixed liquid (suspended matter SS and chemical Oxygen demand, COD _cr , and the removal rates of the two are ≥80% and ≥30% respectively), and the effluent is the protein liquid; the effluent, which is the protein liquid, obtained through the separation of the air flotation tank is filtered and dehydrated by a plate and frame filter press. Finally, starch protein and filtrate are obtained, and the obtained starch protein is dried by a tube bundle dryer to make protein feed; when dried by a tube bundle dryer, the drying conditions are normal pressure, a drying temperature of 40°C, and a drying time of 6 hours;

c, the filtrate obtained after step b pressure filtration and dehydration is introduced into the IC anaerobic reactor for biochemical treatment, the filtrate to be obtained enters the first reaction zone of the reactor from the bottom of the IC anaerobic reactor, and passes through the bottom of the reactor The incoming water will dilute the imported filtrate, so that the organic matter in the filtrate can be fully reacted and degraded, and a large amount of biogas will be generated at the same time. Part of the generated biogas is collected by the three-phase separator in the lower layer of the IC anaerobic reactor; the other part of the biogas is entrained The filtrate and the sludge in the filtrate enter the second reaction zone, and the filtrate enters the gas-liquid separator in the second reaction zone under the entrainment of the biogas, and through the gas-liquid separation, the biogas is separated from the filtrate and collected. The remaining filtrate and sludge enter the bottom of the first reaction zone through the return pipe under the action of gravity;

The IC anaerobic reactor adopts a tower reactor with a height-to-diameter ratio of 4-8:1; the IC anaerobic reactor operates under normal temperature conditions, and the volume load is 17.0-22.0 kg COD _Cr /(m ³ d), the surface load in the sedimentation zone is 0.6 m ³ /(m ² h), and the hydraulic retention time in the reaction zone is 5-7 h;

d, the filtrate and the sludge that enter the bottom of the first reaction zone after step c is treated by the IC anaerobic reactor are introduced into the MBR membrane bioreactor for separation (the MBR membrane bioreactor adopts a polypropylene hollow fiber membrane , the pore size of the membrane is 0.1-0.45 μm), the residence time in the MBR membrane bioreactor is 4-6h, and the content of dissolved oxygen DO is controlled to be 2-4 mg/L during the separation process; after passing through the MBR membrane bioreactor The sludge obtained after separation is dried and reused, and the supernatant obtained after separation is directly discharged or recycled; the removal rate of suspended matter SS and biochemical oxygen demand BOD ₅ in the supernatant obtained after separation by MBR membrane bioreactor Reach ≥90% and ≥85% respectively.

Embodiment 2: basically the same as Embodiment 1, the difference is:

In step a: the mass percent concentration of the polyacrylamide aqueous solution is 0.05%, and the addition amount of the polyacrylamide aqueous solution accounts for 4% of the total weight of the starch wastewater; the mass percent concentration of the polyaluminum chloride aqueous solution is 10% , the addition of polyaluminum chloride aqueous solution accounts for 1.0% of the total weight of starch wastewater;

In step b: when drying by a tube bundle dryer, the drying conditions are normal pressure, a drying temperature of 50° C., and a drying time of 4 hours.

Embodiment 3: basically the same as Embodiment 1, the difference is:

In step a: the mass percent concentration of the polyacrylamide aqueous solution is 0.1%, and the addition amount of the polyacrylamide aqueous solution accounts for 2% of the total weight of the starch wastewater; the mass percent concentration of the polyaluminum chloride aqueous solution is 5% , the addition of polyaluminum chloride aqueous solution accounts for 2% of starch wastewater gross weight;

In step b: the drying condition is normal pressure, the drying temperature is 45° C., and the drying time is 5 hours when drying by the tube bundle dryer.

Embodiment 4: basically the same as Embodiment 1, the difference is:

In step a: the mass percent concentration of the polyacrylamide aqueous solution is 0.065%, and the addition amount of the polyacrylamide aqueous solution accounts for 3.5% of the total weight of the starch wastewater; the mass percent concentration of the polyaluminum chloride aqueous solution is 9% , the addition of the polyaluminum chloride aqueous solution accounts for 1.2% of the total weight of the starch wastewater.

Embodiment 5: basically the same as Embodiment 1, the difference is:

In step a: the mass percent concentration of the polyacrylamide aqueous solution is 0.09%, the addition of the polyacrylamide aqueous solution accounts for 2.5% of the total weight of the starch wastewater; the mass percent concentration of the polyaluminum chloride aqueous solution is 6% , the addition of the polyaluminum chloride aqueous solution accounts for 1.8% of the total weight of the starch wastewater.

Claims (1)

1. a kind of biochemical treatment method of medium and small starch factory waste water, it is characterized in that, described biochemical treatment method comprises the following steps: a. First, add organic polymer flocculant polyacrylamide aqueous solution and inorganic flocculant polyaluminum chloride aqueous solution to starch wastewater, then stir and mix evenly to obtain a mixed solution, in which stable flocs are formed; the polypropylene The addition of the amide aqueous solution accounts for 2 to 4% of the total weight of the starch wastewater, and the addition of the polyaluminum chloride aqueous solution accounts for 1 to 2% of the total weight of the starch wastewater; b. Import the uniform mixed solution in step a into the air flotation tank for air flotation separation. After the air flotation separation, separate the suspended matter flocs floating in the mixed solution to obtain the effluent, which is protein liquid. The effluent obtained through the separation of the air flotation tank That is, the protein liquid is dehydrated by filter press with a plate and frame filter press, and starch protein and filtrate are obtained after dehydration, and the obtained starch protein is dried by a tube bundle dryer to make protein feed; c, the filtrate obtained after step b pressure filtration and dehydration is introduced into the IC anaerobic reactor for biochemical treatment, the filtrate to be obtained enters the first reaction zone of the reactor from the bottom of the IC anaerobic reactor, and passes through the bottom of the reactor The incoming water will dilute the imported filtrate, so that the organic matter in the filtrate can be fully reacted and degraded, and a large amount of biogas will be generated at the same time. Part of the generated biogas is collected by the three-phase separator in the lower layer of the IC anaerobic reactor; the other part of the biogas is entrained The filtrate and the sludge in the filtrate enter the second reaction zone, and the filtrate enters the gas-liquid separator in the second reaction zone under the entrainment of the biogas, and through the gas-liquid separation, the biogas is separated from the filtrate and collected. The remaining filtrate and sludge enter the bottom of the first reaction zone through the return pipe under the action of gravity; d. The filtrate and sludge that enter the bottom of the first reaction zone after step c is treated by the IC anaerobic reactor are introduced into the MBR membrane bioreactor for separation, and the residence time in the MBR membrane bioreactor is 4 to 6 hours. During the separation process, the dissolved oxygen DO content is controlled to be 2-4 mg/L; the sludge obtained after separation by the MBR membrane bioreactor is dried and reused, and the supernatant obtained after separation is directly discharged or recycled. 2. The method for biochemical treatment of wastewater from small and medium-sized starch factories according to claim 1, characterized in that: the mass percent concentration of the polyacrylamide aqueous solution in step a is 0.05-0.1%; the polyaluminum chloride aqueous solution The mass percent concentration is 5-10%. 3. The method for biochemical treatment of waste water from small and medium-sized starch factories according to claim 1, characterized in that: in step b, when the obtained starch protein is dried by a tube bundle dryer to make protein feed, the drying conditions are normal pressure, dry The temperature is 40-50°C, and the drying time is 4-6 hours. 4. The method for biochemical treatment of wastewater from small and medium-sized starch factories according to claim 1, characterized in that: in step b, the suspended matter flocculation floating in the mixed solution is separated, and the suspended matter in the starch wastewater after the suspended matter is separated The removal rates of SS and COD _cr reached ≥80% and ≥30%, respectively. 5. The method for biochemical treatment of wastewater from small and medium-sized starch factories according to claim 1, characterized in that: the IC anaerobic reactor described in step c adopts a tower reactor with an aspect ratio of 4 to 8:1; The above-mentioned IC anaerobic reactor is operated at normal temperature, the volume load is 17.0-22.0 kg COD _Cr /(m ³ ·d), the surface load in the sedimentation zone is 0.6 m ³ /(m ² ·h), and the hydraulic retention time in the reaction zone is 5-7 hours. 6. The method for biochemical treatment of wastewater from small and medium-sized starch factories according to claim 1, characterized in that: the MBR membrane bioreactor in step d uses a polypropylene hollow fiber membrane with a pore size of 0.1-0.45 μm . 7. The method for biochemical treatment of wastewater from small and medium-sized starch factories according to claim 1, characterized in that: the removal of suspended matter SS and biochemical oxygen demand BOD ₅ in the supernatant obtained after step d is separated by MBR membrane bioreactor The rates reached ≥90% and ≥85%, respectively.