CN112047563A

CN112047563A - Dairy wastewater treatment method

Info

Publication number: CN112047563A
Application number: CN202010731890.9A
Authority: CN
Inventors: 于容朴; 姚杰宇; 梁林海; 郭坤然; 齐岳
Original assignee: Beijing Huaxia Dayu Environmental Protection Co ltd; Beijing Huaxia Dayu Technology Co ltd
Current assignee: Beijing Huaxia Dayu Environmental Protection Co ltd; Beijing Huaxia Dayu Technology Co ltd
Priority date: 2020-07-27
Filing date: 2020-07-27
Publication date: 2020-12-08
Anticipated expiration: 2040-07-27
Also published as: CN112047563B

Abstract

The application provides a dairy waste water treatment method, which comprises the following steps: s1, carrying out primary oil separation on the dairy waste water, adding an extracting agent, extracting to obtain oil pollutants containing the extracting agent and waste water, and separating the oil pollutants and the waste water; s2, separating the grease pollutants containing the extracting agent in the step S1 by a distillation method, and recycling the extracting agent; s3, hydrolyzing the grease pollutants in the step S2 by using an alkali solution with the concentration of 2-20% to obtain a water-soluble product; s4, oxidizing the extracted wastewater in the step S1 and the product obtained in the step S3 into harmless water and carbon dioxide through aerobic bacteria of a biochemical system, and discharging the residual undegradable part after precipitation along with sludge. This application is through the separation mode of extractive distillation, makes more thorough of separating in the time of the grease enrichment in the dairy waste water, and the material that further utilizes alkali lye hydrolysis, biochemical treatment after the grease separation to generate can directly discharge, and no secondary pollution produces.

Description

Dairy wastewater treatment method

Technical Field

The invention belongs to the technical field of wastewater treatment, and particularly relates to a method for treating dairy wastewater.

Background

With the progress of society, people have more and more demand for dairy products, and the discharge amount of waste water generated in the production and processing processes of the dairy products also shows an increasing trend. The dairy waste water generally contains a plurality of fine particles and a large amount of grease, the grease is degraded very slowly and attached to certain waste materials, and the grease not only influences the normal operation of a water pump, but also possibly causes the sludge expansion of an aerobic system. Therefore, in the treatment of dairy waste water, oil removal is particularly important. The oil treatment of the dairy wastewater is always a difficult point of the dairy wastewater treatment process, and how to efficiently and cleanly remove the oil in the wastewater to degrade the oil and the wastewater in a biochemical manner is a problem which is currently focused on.

At present, the treatment method of the dairy wastewater mainly comprises a hydrolysis acidification and SBR combined process and an air floatation and aerobic combined process. The hydrolysis acidification technology is characterized in that the anaerobic process is controlled in a hydrolysis and acid production stage, insoluble organic matters are hydrolyzed into soluble organic matters and macromolecular substances are decomposed into micromolecular substances by utilizing the reaction of hydrolysis and acid-producing bacteria, so that the biodegradability of the wastewater is improved, and the subsequent aerobic treatment is facilitated. SBR (Sequencing Batch Reactor) is a short name for a Sequencing Batch activated sludge process or a Batch activated sludge process, and is a sewage treatment method operated in an intermittent aeration mode. The SBR process completes five basic processes of water inlet, reaction, precipitation, water drainage and standing in one reactor, realizes the removal of organic matters through the full contact of sewage and activated sludge, and ensures that a system is in anaerobic, anoxic, aerobic and other states by adjusting the time of five stages and the length of aeration time, thereby having good denitrification and dephosphorization effects.

The air floatation technique is a water treatment technique widely used in the treatment of oily waste water at home and abroad, and the principle is that air or other gases are introduced into water to generate micro bubbles, so that some fine suspended oil droplets and solid particles in the water are attached to the bubbles and float to the water surface along with the bubbles to form floating slag, the floating speed can be increased by nearly thousand times, and thus the solid-liquid separation is completed. Depending on the way of generating bubbles, the method can be classified into a pressurized dissolved air flotation method, an impeller flotation method and an aeration flotation method. In order to improve the flotation effect, inorganic or organic polymeric flocculant can be added into the wastewater, the oily wastewater is mainly subjected to a coagulation method, namely the flocculant is added into the oily wastewater, after hydrolysis in water, positively charged micelles and negatively charged emulsified oil generate electric neutralization, oil particles are aggregated, the particle size is increased, floccules are generated to adsorb fine oil drops, and then oil-water separation is realized by a sedimentation or air flotation method. Common flocculating agents include inorganic flocculating agents such as polyaluminium chloride (PAC), ferric chloride, aluminum sulfate, ferrous sulfate and the like, and organic polymer flocculating agents such as acrylamide, Polyacrylamide (PAM) and the like. The method is suitable for oil drops and other fine suspended matters in an emulsified state which can not be separated by gravity settling, and meanwhile, the air floatation equipment has the advantages of large occupied area, large medicament dosage, large generated scum quantity and no thorough treatment on grease.

The invention patent CN 103509611A discloses a treatment process of dairy waste water, which comprises water inlet, grating, regulation, hydrolytic acidification, an aeration biological filter, a clean water tank and water outlet, wherein the hydrolytic acidification is to degrade lactose into lactic acid under the action of lactic acid bacteria and partially hydrolyze protein. The invention can effectively remove grease substances contained in the wastewater through the hydrolysis acidification process, and meanwhile, the biological aerated filter process can effectively reduce the COD content, further improve the effluent quality, reduce the pollution to the environment and improve the quality of the living environment of people. The invention has simple process, low cost, obvious wastewater purification effect, benefit to the environment and easy mass treatment. The process has the defects that the process has certain effect on the dairy waste water with COD concentration less than 3000mg/L and can not treat the dairy waste water with COD concentration higher than 3000 mg/L.

The invention patent CN 106336083B discloses a dairy waste water integrated system and a process, wherein an oil separation adjusting tank and a coagulation air floatation tank are utilized to remove grease in waste water, and the COD content in the waste water is further removed through biochemical treatment of air floatation outlet water. The process has the disadvantages that the oil separation tank can only remove heavy oil on the surface of the dairy wastewater, can not remove grease in the wastewater, and a large amount of scum is generated when the grease is removed by using an air floatation method.

Disclosure of Invention

In order to overcome the problems in the prior art, the method for treating the dairy waste water is simple in treatment process, the grease in the dairy waste water is more thoroughly separated in an extraction distillation mode, the grease is biochemically treated into water-soluble substances after being hydrolyzed by adding the alkali liquor, no secondary pollutants are generated, and the system slag discharge in the whole treatment process can be reduced by more than 90% compared with the conventional air floatation treatment mode.

In order to achieve the purpose, the application is realized by the following technical scheme:

a dairy waste water treatment method is characterized by comprising the following steps:

s1, carrying out primary oil separation on the dairy waste water, adding an extracting agent, extracting to obtain oil pollutants containing the extracting agent and waste water, and separating the oil pollutants and the waste water;

s2, separating the grease pollutants containing the extracting agent in the step S1 by a distillation method, and recycling the extracting agent;

s3, hydrolyzing the grease pollutants in the step S2 by using an alkali solution with the concentration of 2-20% to obtain a water-soluble product;

s4, oxidizing the extracted wastewater in the step S1 and the product obtained in the step S3 into harmless water and carbon dioxide through aerobic bacteria of a biochemical system, and discharging the residual undegradable part after precipitation along with sludge.

Further, the extracting agent is one or more of kerosene, ethanol or diethyl ether.

Furthermore, the extracting agent is kerosene, and the kerosene is used for extraction, so that the extraction is more thorough.

Further, the ratio of the extracting agent to the dairy waste water in the step S1 is 1: 1-8.

Further, the extraction time in the step S1 is 0.5-1 h, the extraction temperature is 70-100 ℃, and the grease extraction amount is more than or equal to 80%.

Further, the alkali solution in step S3 is one or both of sodium hydroxide and potassium hydroxide.

Furthermore, the amount of the alkali liquor added to each ton of the wastewater in the step S3 is 50-500 ml.

Further, the pH value of the reaction solution in the step S3 is 8-10.

Further, the hydrolysis time in the step S3 is 10-20 h, and the hydrolysis rate of the grease is 80% -90%.

The processing principle is as follows: after the dairy waste water is extracted, oil pollutants containing an extracting agent and the waste water are layered after standing, the oil pollutants and the waste water are separated, the oil pollutants containing the extracting agent are distilled, the extracting agent can be recycled after being distilled, the processes of extraction and distillation are equivalent to the process of grease enrichment, the grease pollutants after enrichment are hydrolyzed by using alkali liquor, the oil pollutants comprise about 80% of grease and 20% of protein, the principle that reaction can be carried out between the alkali liquor and the grease and the alkali liquor catalyzes proteolysis is utilized, the grease is decomposed into higher fatty acid and glycerin after the alkali liquor is added, the protein is decomposed into amino acid, finally the waste water separated after extraction and the higher fatty acid, the glycerin and the amino acid generated after the alkali liquor hydrolysis are oxidized into harmless water and carbon dioxide by aerobic bacteria of an existing biochemical system, and the residual undegradable part is discharged along with the sludge.

The invention has the following beneficial effects:

(1) although the oil content of the dairy waste water subjected to primary treatment is higher, the contrast water amount is larger and can be several orders of magnitude, and the oil is enriched by means of extraction and distillation, so that the problems of equipment and transportation cost generated when concentration is carried out independently are solved. After the dairy wastewater is extracted and distilled, grease pollutants and wastewater are separated more thoroughly while enriching. The separated oil pollutants can be hydrolyzed by alkali liquor to generate micromolecular water-soluble substances such as higher fatty acid, glycerol, amino acid and the like which are easy to decompose, and the micromolecular water-soluble substances which are easy to decompose are subjected to biochemical treatment, so that the biochemical treatment load is small and the water outlet effect is better compared with the method for directly performing biochemical treatment on oil and protein. The substances generated after biochemical treatment can be directly discharged without generating secondary pollution.

(2) Although the oil content of the dairy waste water subjected to primary treatment is higher, the difference of the oil content and the water content is larger, and the difference can be several orders of magnitude, firstly, the existing lactobacillus hydrolysis acidification and aeration biofilter combination is directly utilized to treat the dairy waste water, and only the dairy waste water with the COD (Chemical Oxygen Demand) concentration of less than 3000mg/L can be treated to a certain extent; secondly, the alkali liquor is directly used for treatment, the amount of the added alkali liquor is very large, and the treatment effect is not good. Therefore, after the grease is separated out in an extractive distillation mode, the grease is directly decomposed by using the alkali liquor, the using amount of the alkali liquor is reduced, the treatment effect is improved, and the experimental result shows that the application of the method can treat dairy wastewater with COD concentration of less than 50000 mg/L.

(3) Compared with the existing air floatation method, the method for treating the dairy wastewater can reduce the system slag discharge amount by more than 90% after the treatment compared with the existing treatment mode.

(4) In the application, the extractant can be recycled, so that resources are saved, and sludge obtained by precipitation after biochemical treatment can be returned for secondary utilization.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments.

1. Treatment method of dairy wastewater

Example 1

The treatment method of the invention is used for treating the milk processing plant with the wastewater treatment capacity of 150 tons/day, and comprises the following steps:

1. after the primary oil separation of the wastewater, the temperature of an extraction tank is about 80 ℃, oil and a small amount of protein are extracted by kerosene, after the reaction is carried out for 1.0h, an extracting agent is separated from the wastewater, the wastewater enters a biochemical treatment unit, and oil pollutants containing the extracting agent enter distillation treatment;

2. grease containing the extracting agent and a small amount of protein are separated from the extracting agent in a distillation mode, the extracting agent is recycled after refluxing, and the grease and the small amount of protein are decomposed;

3. the decomposition part contains 50ml of 2% sodium hydroxide solution, the grease and a small amount of protein are subjected to hydrolysis reaction under the action of the sodium hydroxide solution, the reaction time is 10 hours, and water-soluble substances of higher fatty acid, glycerol and amino acid are generated after the reaction;

4. after the hydrolysis is finished, water-soluble substances (higher fatty acid, glycerin and amino acid) enter a biochemical system after pH adjustment, are oxidized into harmless water and carbon dioxide under the action of aerobic bacteria in the biochemical system, and the undegradable part after precipitation is discharged along with residual sludge.

Example 2

1. after the wastewater is subjected to primary oil separation, the temperature of an extraction tank is about 90 ℃, oil and a small amount of protein are extracted by ethanol, after the reaction is carried out for 0.5h, an extracting agent is separated from the wastewater, the wastewater enters a biochemical treatment unit, and oil pollutants containing the extracting agent enter distillation treatment;

3. the decomposition part contains 200mL of 10% potassium hydroxide solution, the grease and a small amount of protein are subjected to hydrolysis reaction under the action of the potassium hydroxide solution, the reaction time is 10h, and high-grade fatty acid, glycerol and amino acid water-soluble substances are generated after the reaction;

Example 3

In a yoghourt processing plant, the waste milk treatment capacity is 150 tons/month, and the processing is carried out according to the processing method of the invention, and the steps are as follows:

1. after the primary oil separation of the wastewater, the temperature of an extraction tank is about 80 ℃, oil and a small amount of protein are extracted by kerosene, after the reaction for 1h, an extracting agent is separated from the wastewater, the wastewater enters a biochemical treatment unit, and oil pollutants containing the extracting agent enter a distillation treatment;

3. the decomposition part contains 300mL of 20% sodium hydroxide solution, the grease and a small amount of protein are subjected to hydrolysis reaction under the action of the sodium hydroxide solution, the reaction time is 20h, and water-soluble substances of higher fatty acid, glycerol and amino acid are generated after the reaction;

Example 4

3. the decomposition part contains 500mL of 10% potassium hydroxide solution, the grease and a small amount of protein are subjected to hydrolysis reaction under the action of the potassium hydroxide solution, the reaction time is 20h, and high-grade fatty acid, glycerol and amino acid water-soluble substances are generated after the reaction;

Comparative example 1

In a certain milk processing plant, the wastewater treatment capacity is 150 tons/day, and the treatment method comprises the following steps:

1. after the wastewater is subjected to primary oil separation, 500mL of 20% sodium hydroxide solution is added, and the grease and a small amount of protein are subjected to hydrolysis reaction under the action of the sodium hydroxide solution for 20 hours;

2. after the hydrolysis is finished, water-soluble substances (higher fatty acid, glycerin and amino acid) enter a biochemical system after pH adjustment, are oxidized into harmless water and carbon dioxide under the action of aerobic bacteria in the biochemical system, and the undegradable part after precipitation is discharged along with residual sludge.

Comparative example 2

3. sending the grease and a small amount of protein into a hydrolysis acidification tank, and performing degradation treatment for 10 hours under the action of lactic acid bacteria;

Reference 3

In a certain milk processing plant, the treatment capacity of the waste water is 150 tons/day, the waste water is treated by adopting the existing air floatation method, and the treatment method comprises the following steps:

1. the dairy waste water is collected and enters a water collecting tank, and is lifted by a pump to enter an air floatation treatment system after primary oil separation;

2. the air flotation system adds PAC solution with the concentration of 7.5 percent and PAM agent with the concentration of 2 per mill, and scum generated by grease in the wastewater is discharged out of the system through a slag scraper;

3. the effluent of the air floatation system automatically flows into a biochemical unit, is oxidized into harmless water and carbon dioxide under the action of aerobic bacteria of the biochemical system, and the undegradable part reflows to the biochemical treatment part along with the residual sludge to be continuously treated.

2. Performance detection

Measuring suspended matters (SS) before and after the treatment of the dairy wastewater and comparing the suspended matters with Chemical Oxygen Demand (COD), wherein the suspended matters (SS) are measured according to GB 11901-1989; chemical Oxygen Demand (COD) was determined with reference to HJ/T399-2007.

The results of comparing examples 1-4 with comparative examples 1-3 are shown in Table 1:

TABLE 1

Examples 1-4 are dairy waste waters treated by the method of the present application, comparative example 1 is a method without extractive distillation but directly treated with alkali lye, comparative example 2 is a method with extractive distillation without alkali lye treatment, treated by the current hydrolytic acidification bacteria method, and comparative example 3 is a method with air float. As can be seen from Table 1, in the treatment of suspended matters, compared with examples 1-4, comparative example 1 has the advantages that the treatment rate is only 53.7% and the treatment amount is only half even if 500mL of 20% sodium hydroxide solution is added, the treatment rate is directly performed on the dairy wastewater without enriching the grease by an extractive distillation method; in the comparison document 2, no alkali liquor treatment is used after enrichment, the treatment capacity is only 21.1% by using lactobacillus and biochemical treatment, which indicates that hydrolysis acidification bacteria and aeration tank treatment are directly performed on macromolecular substances such as grease and protein, and for hydrolysis acidification bacteria and biochemical treatment bacteria, the biochemical treatment load is large and the treatment effect is poor. The treatment amounts of the examples 1 to 4 are all more than 90%, which shows that the grease and protein in the dairy waste water are hydrolyzed into micromolecular soluble higher fatty acid, glycerol, amino acid and the like by using the alkali liquor, and the biochemical treatment load is small, the biodegradability is high and the treatment effect is good when the biochemical treatment is used. In comparison document 3, in order to use the air float process which is often used at present, although the throughput is increased, the amount of scum is increased.

As for the treatment of COD, as can be seen from table 1, in comparative example 1, compared with examples 1 to 4, the treatment effect is limited in the case of a large amount of wastewater because the COD concentration is high in the primarily treated dairy wastewater, even if 500mL of 20% sodium hydroxide solution is added after the alkaline treatment of dairy wastewater without the oil and fat enrichment; in the comparison document 2, no alkali liquor is used for treatment after enrichment, the treatment capacity is only 9%, which shows that hydrolysis acidification bacteria and aeration tank treatment are directly performed on macromolecular substances such as grease and protein, the biochemical treatment load is large and the treatment effect is poor for hydrolysis acidification bacteria and biochemical treatment bacteria, and the treatment capacities of the examples 1 to 4 are all more than 88%, which shows that grease and protein in dairy waste water are hydrolyzed into soluble high-grade fatty acid, glycerin, amino acid and the like of small molecules by using alkali liquor, and the biochemical treatment load is small, the biochemical property is high and the treatment effect is better. The reference 3 is a reference which uses the air float process which is often used at present, and generates much scum although the processing amount is relatively large.

The amount of scum produced after the treatments of examples 1-4 and comparative example 3 was compared and the results are shown in table 2:

TABLE 2

In comparative example 3, the oil is treated by using PAM and PAC as flocculants, the reaction comprises two processes of coagulation and flocculation, and the principle is that the colloid double electric layer in the water is compressed and destabilized to form smaller particles in the coagulation stage, the particles are mutually coagulated in the flocculation stage or form large particle flocs by the adsorption and bridging action of macromolecular substances, and the flocs can be separated and removed from the water under certain precipitation conditions. In examples 1 to 4, the treatment of fats and oils by the alkali treatment method of the present application is shown in table 2, and it is understood that the amount of scum in the dairy wastewater treated by the present application is much less than that in the treatment process of comparative example 3.

The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and is not intended to limit the practice of the invention to these embodiments. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.

Claims

1. A dairy waste water treatment method is characterized by comprising the following steps:

2. The method for treating dairy waste water according to claim 1, wherein the extractant is one or more of kerosene, ethanol or diethyl ether.

3. The method for treating dairy waste water according to claim 2, wherein the extracting agent is kerosene.

4. The dairy waste water treatment method according to claim 1, wherein the ratio of the extracting agent to the dairy waste water in the step S1 is 1: 1-8.

5. The dairy wastewater treatment method according to claim 1, wherein the extraction time in the step S1 is 0.5-1 h, the extraction temperature is 70-100 ℃, and the grease extraction amount is not less than 80%.

6. The method for treating dairy waste water according to claim 1, wherein the alkali solution in step S3 is one or both of sodium hydroxide and potassium hydroxide.

7. The dairy waste water treatment method according to claim 1, wherein the amount of the alkali added to each ton of the waste water in step S3 is 50-500 ml.

8. The dairy wastewater treatment method according to claim 1, wherein the reaction solution in step S3 has a pH of 8-10.

9. The dairy wastewater treatment method according to claim 1, wherein the hydrolysis time in step S3 is 10-20 h, and the oil hydrolysis rate is 80-90%.