CN115477386A

CN115477386A - Anaerobic fermentation method for mixing wastewater and vinasse

Info

Publication number: CN115477386A
Application number: CN202210892216.8A
Authority: CN
Inventors: 何荣玉; 张自强; 杨琦; 詹余福; 刘笃一
Original assignee: Cecep Green Carbon Zunyi Environment Protection Co ltd; Cecep Green Carbon Environment Protection Co ltd
Current assignee: Cecep Green Carbon Zunyi Environment Protection Co ltd; China National Environmental Protection Group Co ltd
Priority date: 2022-07-27
Filing date: 2022-07-27
Publication date: 2022-12-16

Abstract

The application provides a waste water and lees mixed anaerobic fermentation method, which comprises the following steps: mixing the first biogas slurry with wastewater to obtain a first mixed solution; wherein the feeding COD volume load of the wastewater meets a first preset condition; mixing the first mixed solution with vinasse to obtain a second mixed solution; carrying out anaerobic fermentation on the second mixed solution, collecting biogas generated in the anaerobic fermentation process, and continuously measuring process parameters in the anaerobic fermentation process until the process parameters meet second preset conditions; stopping anaerobic fermentation, and filtering the fermented second mixed solution to obtain second biogas slurry; wherein the second biogas slurry can be used as the first biogas slurry to be mixed with the wastewater. Use first natural pond liquid to inoculate waste water to increase the microorganism in the fermentation system, improve the pH and the stability of system simultaneously, mix first mixed liquid and lees and carry out anaerobic fermentation, both can handle high concentration waste water, reduce waste water discharge capacity, can increase the gas production, increase the income.

Description

Anaerobic fermentation method for mixing wastewater and vinasse

Technical Field

The application relates to the technical field of anaerobic fermentation, in particular to a waste water and vinasse mixed anaerobic fermentation method.

Background

The vinasse is a byproduct in the brewing process, has high organic matter content and high water content, is extremely easy to decay, and causes potential risks to the environment, the organic matter in the vinasse can be degraded through anaerobic fermentation treatment, the methane generated in the anaerobic fermentation process can be recovered, the energy is recycled, and the method is an excellent treatment mode.

High concentration waste water (COD content exceeds 50000 mg/L) is because of its COD content is higher, uses conventional processing means to handle, dilutes high concentration waste water through adding water or adding low concentration waste water, discharges after COD content reduces to accord with the standard, owing to need add a large amount of water, leads to the treatment cost very high, greatly increased the emission of waste water moreover, and high concentration waste water cost is higher to present conventional means handles.

Therefore, how to treat high-concentration wastewater economically and environmentally is a technical problem to be solved urgently in the industry.

Disclosure of Invention

In view of the above, the present application aims to provide a method for anaerobic fermentation of wastewater and distiller's grains by mixing, which solves or partially solves the problems of the background art.

Based on the above purpose, the application provides a method for anaerobic fermentation by mixing wastewater and distiller's grains, which comprises the following steps:

mixing the first biogas slurry with wastewater to obtain a first mixed solution; wherein the feeding COD volume load of the wastewater meets a first preset condition;

mixing the first mixed solution with vinasse to obtain a second mixed solution;

carrying out anaerobic fermentation on the second mixed solution, collecting biogas generated in the anaerobic fermentation process, and continuously measuring process parameters in the anaerobic fermentation process until the process parameters meet second preset conditions;

filtering the fermented second mixed solution to obtain second biogas slurry; wherein the second biogas slurry can be used as the first biogas slurry to be mixed with the wastewater.

The waste water mainly refers to high-concentration waste water (COD content exceeds 50000 mg/L). Can produce a large amount of high COD waste water in chemical production processes such as wine making and brewing, bio-pharmaceuticals, petrochemical refining, heavy metal smelting, these high COD waste water conventional means treatment costs are high, consequently use this application the method carry out the coprocessing, improve the utilization level of the resource of lees and waste water.

Wherein, the vinasse is residue left after brewing wine such as rice, wheat, sorghum and the like.

The first biogas slurry is brown bright liquid formed by anaerobic fermentation of organic substances.

Further, the anaerobic fermentation adopts medium-temperature fermentation, and the fermentation temperature is 35-42 ℃.

Further, the temperature of the anaerobic fermentation was 37 ℃.

Further, the first preset condition is that: the feeding COD volume load of the wastewater is less than or equal to 3-4 kg COD/(m) ³ ·d)。

Further, the first preset condition is that: the feed COD volume load of the wastewater is less than or equal to 3.28kg COD/(m) ³ ·d)。

The volume load is the amount of contaminants that the fermentation apparatus can withstand per unit of effective volume per unit time. In the present application, the COD content of wastewater that can be tolerated per unit effective volume of a fermentation apparatus per unit time is expressed as a COD volume load.

Wherein, the experiment proves that when the feeding COD volume load of the wastewater is more than 3.28kg COD/(m) ³ D), the COD content in the first mixed liquid is too high due to too large volume load of the feeding COD of the wastewater, so that the acidification of a fermentation system is easily caused, and the gas production capacity is reduced and even stopped.

Further, the process parameters include: anaerobic fermentation hydraulic retention time, unit gas production of the biogas, methane content in the biogas, and/or pH of the second mixed liquor.

Further, the second preset condition includes: the anaerobic fermentation hydraulic retention time reaches a preset time, the first difference ratio of the unit gas production rates of two adjacent anaerobic fermentation hydraulic retention time is not more than 10%, the methane content in the biogas is not less than 50%, and the pH of the second mixed solution is = 6-8.

The second preset condition comprises the four conditions, when the parameters in the anaerobic fermentation process of the second mixed liquid meet the four conditions, the anaerobic fermentation process of the second mixed liquid is stable and meets the actual requirements, and the anaerobic fermentation of the second mixed liquid is completed at the moment.

The anaerobic fermentation hydraulic retention time is the optimal time for anaerobic fermentation of the second mixed liquor. When the anaerobic fermentation time is too short, the fermentation of the second mixed solution is insufficient, and organic matters in the second mixed solution are not sufficiently fermented and are not sufficiently utilized, so that the waste of resources is caused; when the time of anaerobic fermentation is too long, the cost of fermentation reaction is increased, and the loss is greatly increased.

Wherein the preset time is 30-60 days.

Wherein the preset time is preferably 40 days.

In the anaerobic fermentation process, the unit gas production and the methane content in the biogas are direct indexes for representing the operation stability of the fermentation system, and the fermentation tank which keeps the unit gas production and the methane content in the biogas stable at the same time has practical significance. Wherein, the first difference ratio of two adjacent unit gas production rates is not more than 10 percent, which proves that the unit gas production rates are kept stable; the content of methane in the biogas is more than or equal to 50 percent, which proves that the content of methane in the biogas is kept stable, and the fermentation process can be kept stable only when the two conditions are met, so that the fermentation has practical significance.

Wherein the first difference ratio Q is calculated by the formula: q = (w 1-w 2)/w 1, wherein w1 is the larger value of the adjacent two unit gas production rates, and w2 is the smaller value of the adjacent two unit gas production rates.

Wherein the pH of the second mixed solution is 6 to 8.5. The pH value directly influences the metabolism and reproduction of microorganisms in the anaerobic fermentation process. Generally, the pH value of anaerobic fermentation is normally 6-8.5, and the generation of biogas is not favorable when the pH value is lower than 6 or higher than 8.5. When the pH value is lower than 6, acidification reaction is easy to occur in the anaerobic fermentation tank, which is not beneficial to the fermentation of the second mixed solution, and when the pH value is higher than 8.5, ammonia nitrogen concentration accumulation is easy to occur, so that gas production is inhibited.

Further, the pH of the second mixed solution =6.8 to 8.

Further, the formula for calculating the feed volume of the wastewater is as follows: v1= (V) ₀ *a)/n，

Wherein V1 is the feed volume of the wastewater; v ₀ Is the effective volume of the fermentation device; a is the feed COD volumetric load of the wastewater; n is the COD content of the wastewater.

Further, the formula for calculating the dry matter feeding quality of the vinasse is as follows: m2= b V,

wherein m2 is the dry matter feeding mass of the vinasse; b is the dry matter concentration of the second mixed solution; v is the total volume of the second mixed solution.

And calculating the dry matter feeding quality of the vinasse according to the total volume of the second mixed liquor and the dry matter concentration of the second mixed liquor. From the mass of the dry matter feed of the whole stillage and the mass of the dry matter of the raw stillage, the total feed volume of the whole stillage (i.e. V2 described below) can be calculated.

When the anaerobic fermentation is a continuous feeding and discharging process, the total volume of the second mixed liquor obtained by each fermentation = the effective volume of the fermentation device/the hydraulic retention time of the anaerobic fermentation; when the anaerobic fermentation is discontinuous feeding and discharging, the total volume of the second mixed liquor of each fermentation is less than or equal to the effective volume of the fermentation device.

Further, the dry matter concentration of the second mixed solution is not more than 15%.

Further, the dry matter concentration of the second mixed solution is 6-10%.

When the dry matter concentration of the second mixed solution is too large, the concentration of the vinasse in the second mixed solution is too high, so that the stirring in the anaerobic fermentation process is difficult, and the more difficult the stirring, the poorer the homogenization effect of the second mixed solution is, and the poorer the anaerobic fermentation effect is.

Further, the calculation formula of the feeding volume of the first biogas slurry is as follows: v3= V-V1-V2,

wherein, V3 is the feeding volume of first natural pond liquid, and V is the total volume of second mixed liquid, and V1 is the feeding volume of waste water, and V2 is the feeding total volume of lees.

Further, the first biogas slurry and the second biogas slurry are non-aerated biogas slurries.

Experiments prove that if the first biogas slurry or the second biogas slurry is subjected to aeration reflux, the gas production of a fermentation system is negatively influenced, so that the unit gas production is reduced, and anaerobic fermentation is not facilitated.

From the above, according to the method for mixed anaerobic fermentation of wastewater and vinasse, the wastewater is mixed with the first biogas slurry to obtain a first mixed solution meeting a first preset condition, the first biogas slurry is used for inoculating the wastewater to increase microorganisms in a fermentation system and accelerate the fermentation reaction, and meanwhile, the alkaline first biogas slurry can neutralize the acidic wastewater to improve the pH and stability of the system, so that the wastewater cannot generate too much impact on the fermentation process, and the phenomenon that the fermentation system is acidified due to too high COD in the wastewater and finally the gas production capacity is reduced or even stopped is avoided; the first mixed liquor and the vinasse are mixed and then subjected to anaerobic fermentation, so that high-concentration wastewater can be treated, the discharge amount of the wastewater is reduced, the gas production rate can be increased, and the income is increased; meanwhile, the second biogas slurry obtained after anaerobic fermentation can be recycled as the first biogas slurry, so that the discharge amount of wastewater is reduced, the treatment cost is greatly reduced, and economic and environment-friendly treatment of high-concentration wastewater is realized.

Drawings

In order to more clearly illustrate the technical solutions in the present application or related technologies, the drawings required for the embodiments or related technologies in the following description are briefly introduced, and it is obvious that the drawings in the following description are only the embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a graph showing the daily gas production at different COD volumetric loads of wastewater feeds in example 1 of the present application;

FIG. 2 is a graph showing the variation of methane concentration under COD volumetric load for different wastewater feeds in example 1 of the present application;

FIG. 3 is a graph showing the pH change of a second mixed solution under different COD volumetric loads of wastewater feeds in example 1 of the present application;

FIG. 4 is a graph showing the change in methane concentration during the fermentation in comparative example 1 of the present application;

FIG. 5 is a graph showing the daily gas production change during the fermentation process in comparative example 1 of the present application;

FIG. 6 (a) is a graph showing the daily gas production at a lower volumetric load of COD in the wastewater feed in comparative example 2 of the present application;

FIG. 6 (b) is a graph showing the daily gas production under the condition of higher volumetric load of COD in the wastewater feed in comparative example 2;

FIG. 7 (a) is a graph showing the change of methane concentration under the condition of lower volumetric load of COD in the wastewater feed in comparative example 2 of the present application;

FIG. 7 (b) is a graph showing the change of methane concentration under the condition of higher volumetric load of COD in the wastewater feed in comparative example 2 of the present application;

FIG. 8 is a graph showing the pH change of a second mixed solution under different COD volumetric loads of wastewater feeds in comparative example 2 of the present application;

FIG. 9 is a graph showing the daily gas production at different volumetric loads of wastewater feedstock COD in comparative example 3;

FIG. 10 is a graph showing the variation of methane concentration under COD volumetric load for different wastewater feeds in comparative example 3 of the present application;

FIG. 11 is a graph showing the pH change of a second mixed liquor at different COD volumetric loads for the wastewater feed of comparative example 3;

FIG. 12 is a graph showing the daily gas production at different volumetric loads of wastewater feedstock COD in comparative example 4 of the present application;

FIG. 13 is a graph showing the variation of methane concentration under COD volumetric load for different wastewater feeds in comparative example 4 of the present application;

FIG. 14 is a graph showing the pH change of a second mixed liquor at different COD volumetric loads for the wastewater feed of comparative example 4;

FIG. 15 is a schematic view of the structure of a fermenter according to example 2 of the present application.

In the figure: 1. a tank body; 2. a water bath jacket; 3. a discharge port; 4. a water outlet; 5. a water inlet; 6. stirring blades; 7. a stirring rod; 8. a timer; 9. a feed inlet; 10. a motor; 11. air bags; 12. a wet gas flow meter; 13. an exhaust valve; 14. detecting a pipeline; 15. a biogas pipeline.

Detailed Description

To make the objects, technical solutions and advantages of the present disclosure more apparent, the present disclosure is further described in detail below with reference to specific embodiments.

It should be noted that, unless otherwise defined, technical terms used in the following examples have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, were all conventional biochemical reagents; the experimental methods are conventional methods unless otherwise specified.

The lees in the following examples and comparative examples were lees from a certain brewery, and the physical and chemical index analysis of lees is shown in Table 1. Where TS% is the solids content and VS (% TS) is the volatile solids content.

TABLE 1 physical and chemical indexes of distiller's grains

Name(s)	pH	TS/％	VS/(％TS)	Organic carbon/%)	Total nitrogen/%)
						Vinasse	3.04	47.02	93.20	44.03	3.88

The wastewater sources referred to in the following examples and comparative examples are winery wastewater. As the quality of the wastewater in the winery fluctuates greatly (the COD range of the incoming water is 80000-320000 mg/L) along with the production stage, the ammonia nitrogen content and COD index analysis is needed to be carried out on the wastewater taken each time. The physical and chemical indexes of the wastewater used in the following examples are analyzed as shown in Table 2.

TABLE 2 physicochemical indices of wastewater

Name(s)	pH	Ammonia nitrogen/(mg/L)	COD/(mg/L)
				Waste water	3.35	1540	272250

The first biogas slurry involved in the following examples and comparative examples is biogas slurry obtained after anaerobic fermentation treatment of distiller's grains, and the analysis of physicochemical indexes of the first biogas slurry is shown in table 3.

TABLE 3 first biogas slurry physicochemical index

Name (R)	pH	VS/％	Ammonia nitrogen/(mg/L)	COD/(mg/L)
					First biogas slurry	8.03	74.29	5875.00	54875

It should be noted that, since the sources of the distiller's grains, the wastewater and the first biogas slurry are different, the basic physicochemical indexes thereof are different. Therefore, the physicochemical indexes listed in tables 1, 2 and 3 above are used only in the following examples and comparative examples, and are not limited to any physical and chemical indexes of the distiller's grains, the wastewater and the first biogas slurry.

Comparative example 1

The same lees as in example 1 below were used to perform anaerobic fermentation under the same experimental conditions, and the hydraulic retention time of anaerobic fermentation in the whole anaerobic fermentation process, the unit gas production rate of the biogas, and the methane content in the biogas were measured, and the measurement results are shown in fig. 4 and 5.

Referring to fig. 4 and 5, the anaerobic fermentation was performed using only distillers grains, the daily average gas production was 43.6L, the first difference ratio between the daily gas production of two adjacent distillers grains was not more than 10%, and the average methane content in the daily average gas production was about 50%, which proved that the entire fermentation system was operated smoothly.

Comparative example 2

A method for anaerobic fermentation of spent grain and wastewater is provided, which differs from the following example 1 in that the first biogas slurry is not added. Anaerobic fermentation is performed under the same experimental conditions, the hydraulic retention time of the anaerobic fermentation in the whole anaerobic fermentation process, the unit gas production rate of the biogas, the methane content in the biogas and the pH of the lees are measured, and the measurement results are shown in FIG. 6 (a), FIG. 6 (b), FIG. 7 (a), FIG. 7 (b) and FIG. 8.

Referring to FIGS. 6 (a) and 7 (a), the initial load of the pot and the pot life were 0.835kg COD/(m) ³ D) mixing the high-concentration waste water, and then carrying out anaerobic fermentation, wherein the daily gas production is gradually increased and stabilized at 70-80L/d, and meanwhile, the methane content is stabilized at more than 50%. The wastewater feed COD volumetric load was then increased to 1.62kg COD/(m) ³ D), the daily gas production shows a rapid increasing trend, reaches a high peak value of 110L/d at 30 days of fermentation, then rises again after slightly decreasing, and is stabilized at about 100L, and the methane content still maintains higher water at this stageAnd on the other hand, the first difference ratio of the gas production in two adjacent days is not more than 10%, and the average methane concentration is stabilized at about 50%, so that the whole fermentation system is proved to run stably.

Meanwhile, as shown in fig. 8, after the fermentation is started, the pH value of the fermentation liquid gradually and slowly decreases, and when the fermentation is performed for 42 days, the pH value decreases from 8 to 7.41, and decreases by 0.6 pH unit, the pH basically keeps stable, and the method is suitable for the normal operation of anaerobic fermentation reaction.

Referring to fig. 6 (b) and 7 (b), the COD volume load of the wastewater in the feed is increased continuously as the fermentation process is stabilized. The COD volume load of the wastewater in the feeding is increased to 2.27 kg/(m) ³ D), the daily gas production increases rapidly and reaches a peak 138L on day 52, but after the peak it shows a continuous and rapid decline, the gas production being less than 100L and already less than the average value before the load increase. Meanwhile, the methane content is still more than 50 percent, but the obvious decline trend exists, and the daily gas production and the methane content both have the continuous decline trend. Referring also to FIG. 8, when the volumetric COD load of the feed material is increased to 2.27kg COD/(m) ³ And d) after the fermentation liquid is rapidly reduced to below 7, the operation is continued, the pH value of the fermentation liquid is still continuously reduced, the pH value of the fermentation liquid is proved to be unstable, and the acidification phenomenon of the fermentation liquid is proved to be started by combining the continuous reduction of the daily gas production and the methane content. The COD volume load of the feed wastewater under the condition is less than or equal to 1.62kg COD/(m) COD ³ D), the fermentation process can only be run smoothly.

Comparative example 3

The only difference between the method and the comparative example 1 is that the added first biogas slurry is the aerated biogas slurry. Anaerobic fermentation is carried out under the same experimental conditions, the hydraulic retention time of the anaerobic fermentation in the whole anaerobic fermentation process, the unit gas production of the methane, the methane content in the methane and the pH value of vinasse are measured, and the measurement results are shown in figures 9, 10 and 11.

Referring to fig. 9, gas production was substantially maintained stable under the conditions of the first biogas slurry direct reaction and the first biogas slurry post-aeration reaction. In the whole fermentation period, under the condition that the first biogas slurry directly reacts, the average daily gas production of the substrate is higher than the average daily gas production of the first biogas slurry after gas explosion, and the average daily gas production is respectively 64L and 57L.

Referring to fig. 10, in both conditions, the methane content in the biogas is stable after an initial rise. In the whole fermentation period, under the conditions that the first biogas slurry is directly reacted and the first biogas slurry is reacted after being exploded, the average methane concentration in the biogas is 50 percent and 49.1 percent respectively.

Referring to fig. 11, under the two fermentation conditions of the first biogas slurry direct reaction and the first biogas slurry post-aeration reaction, the change trends of the pH values were similar and both fluctuated within a reasonable range of 7.7-8. In the initial stage of fermentation, organic matters in the vinasse are rapidly hydrolyzed to generate soluble organic matters, acid-producing bacteria convert hydrolysis products into volatile fatty acids, a more obvious pH reduction process occurs, and then, with the stabilization of the methanogenesis process, the pH rises back and tends to be stable. After the first biogas slurry is aerated, ammonia nitrogen in the first biogas slurry is degraded due to aeration, so that the pH value of the second mixed liquid is reduced after reaction, and in the whole fermentation period, the pH value of the first biogas slurry under the aeration part is lower than that of the first biogas slurry under the non-aeration condition.

From the above analysis, the daily gas production and methane concentration of the first biogas slurry under the aeration condition are lower than those of the first biogas slurry under the non-aeration condition for direct reaction. Because part of the reaction liquid is directly subjected to aerobic degradation in the aeration process, the total amount of degradable substances after reaction is reduced, and the gas yield is reduced; the first biogas slurry is aerated for 12 hours, wherein the number of active anaerobic methanogenic floras is reduced, and the degradation activity of the floras is influenced.

Comparative example 4

A method for mixing waste water and vinasse for anaerobic fermentation is provided, which is different from the method in example 1 in that: after the reaction step of example 1, the feed COD volumetric load of the wastewater was increased further to 4.6kg COD/(m) ³ D). The hydraulic retention time of anaerobic fermentation in the whole anaerobic fermentation process, the unit gas production of the methane, the methane content in the methane and the vinasseThe pH was measured, and the measurement results are shown in fig. 12, 13, and 14.

Referring to FIGS. 12 and 13, the initial stage of the experiment was carried out with a COD load of 1.30kg of COD/(m) ³ D), the daily gas production is gradually increased and stabilized to 110-120L/d; the wastewater feed COD volume load in the feed was then increased to 3.28kg COD/(m) ³ D), the daily gas production continuously rises to 160-170L/d, the average methane concentration is 60.63%, and the fermentation tank operates stably. When the COD volume load of the wastewater in the feeding is continuously increased to 4.60kg COD/(m) ³ D), the daily gas production of the fermenter decreases continuously, and the methane content also decreases. Referring to FIG. 14, the pH of the fermentation broth was increased to 3.28kg COD/(m) at the volumetric load of wastewater feeding COD ³ D) is maintained constant, while the COD volume load of the wastewater in the feed is raised to 4.6kg COD/(m) ³ After d), the pH drops rapidly from 7.82 to 7.10, with a warning that there will be a risk of acidification due to an increase in the feed load. Proves that the COD volume load of the wastewater is increased to 4.6kg COD/(m) ³ D), the COD content in the first mixed liquor is too high due to too large volume load of the feed COD of the wastewater, so that acidification of a fermentation system is caused, and the gas production capacity is obviously reduced.

After the acidification of the system is confirmed, the gas production rate of the fermentation system can be adjusted by reducing the COD volume load. The COD volume load of the wastewater in the feed is reduced to 3.94kg COD/(m) ³ D) the daily gas production is still obviously reduced, the pH value also shows an obvious reduction trend, and then the volume load of the wastewater feeding COD in the feeding material is reduced to 3.28kg COD/(m) again ³ D), the daily gas production reaches stability at 140L/d, and the fermentation system continues to run stably.

From the above analysis, it can be seen that the maximum COD volume load of the wastewater should not exceed 3.28 COD/(m) in order to keep the fermenter running smoothly ³ ·d)。

Example 1

Provides a method for anaerobic fermentation by mixing waste water and vinasse, which comprises the following steps:

(1) Mixing the first biogas slurry with wastewater to obtain a first mixed solution, wherein the feed COD volume load of the wastewater is 3.28kg COD/(m) ³ D). The first biogas slurry is non-aerated biogas slurry.

(2) And mixing the first mixed solution with vinasse to obtain a second mixed solution.

(3) And carrying out anaerobic fermentation on the second mixed liquor, collecting biogas generated in the anaerobic fermentation process, and continuously measuring process parameters in the anaerobic fermentation process until the process parameters meet second preset conditions.

The process parameters include: anaerobic fermentation hydraulic retention time, unit gas production of the biogas, methane content in the biogas, and/or pH of the second mixed liquor.

The second preset condition includes: the anaerobic fermentation hydraulic retention time reaches a preset time, the first difference ratio of the unit gas production rates of two adjacent anaerobic fermentation hydraulic retention time is not more than 10%, the methane content in the biogas is not less than 50%, and the pH of the second mixed solution is = 6-8.

(4) Filtering the fermented second mixed solution to obtain second biogas slurry; wherein the second biogas slurry can be used as the first biogas slurry to be mixed with the wastewater.

Wherein, the formula for calculating the feeding volume of the wastewater is as follows: v1= (V a)/n, V1 is the feed volume of wastewater; v is the total volume of the second mixed solution; a is the feed COD volumetric load of the wastewater; and n is the COD content of the wastewater.

Wherein, the calculation formula of the dry matter feeding quality of the vinasse is as follows: m2= b V, m2 being the dry matter feed mass of the vinasse; b is the dry matter concentration of the second mixed solution; v is the total volume of the second mixed solution; b is less than or equal to 15 percent.

Wherein, the formula for calculating the feeding volume of the first biogas slurry is as follows: v3= V-V1-V2, V3 is the feeding volume of first natural pond liquid, V is the total volume of second mixed liquid, V1 is the feeding volume of waste water, and V2 is the feeding total volume of lees.

In this example, the anaerobic fermentation reaction was carried out in a fermenter having an effective volume of 60L (i.e., V) ₀ = 60L), the temperature of anaerobic fermentation is 37 ℃, and the time of anaerobic fermentation is 40-60 days. The dry matter concentration b of the second mixed solution is 6 percent, and the feeding COD capacity of the wastewaterThe volume load a is 3.28kg COD/(m) ³ D) calculating the feed volume of the wastewater, the dry matter feed mass of the vinasse and the feed volume of the first biogas slurry based on the above formulas.

In this example, in order to better observe the variation of each parameter during the reaction process, the initial wastewater feed COD volume load is less than 3.28kg COD/(m) at the initial stage of the reaction ³ D) ensuring that the fermentation reaction can run smoothly at a lower COD volume load, and then continuing to increase the COD volume load to 3.28kg COD/(m) ³ D). In practice, the initial wastewater feed may have a feed COD volumetric load of 3.28kg COD/(m) ³ D), the processing capacity can be improved with maximum efficiency, and the processing cost can be reduced.

The hydraulic retention time of the anaerobic fermentation, the unit gas production rate of the biogas, the methane content of the biogas and the pH value of the second mixed solution in the whole anaerobic fermentation process are measured, and the measurement results are shown in figures 1, 2 and 3.

Referring to FIGS. 1 and 2, at the initial stage of the reaction, the COD load of the feed wastewater was 1.30kg COD/(m) ³ D), the daily gas production is gradually increased and stabilized to 110-120L/d; the wastewater feed COD volume load in the feed was then increased to 3.28kg COD/(m) ³ D), the highest daily gas production is increased to about 170L/d, the daily gas production is between 140 and 170L/d after the reaction is stable, the first difference ratio of the two adjacent daily gas production is not more than 10 percent, the average methane concentration is 60.63 percent, and the fermentation reaction is proved to run stably.

Referring to FIG. 3, the pH of the second mixed solution was changed as shown in FIG. 3, and the pH was kept constant throughout the fermentation, which confirmed that the reaction conditions were good throughout the fermentation reaction.

Compared with the comparative example 1 and the comparative example 2, the comparative example 1 only uses the vinasse for anaerobic fermentation, the daily average gas production is 43.6L, and the average methane content in the daily average gas production is about 50 percent; comparative example 2 anaerobic fermentation was carried out using only distillers' grains and wastewater, the average gas production was stabilized at about 100L, and the methane concentration was stabilized at about 50%; in the embodiment, the wastewater, the first biogas slurry and the vinasse are cooperatively fermented, the daily gas production is 140-170L/d, and the average methane concentration is 60.63%. Therefore, in the application, the gas production rate can be obviously improved by adopting the wastewater, the first biogas slurry and the vinasse to perform synergistic fermentation, and the methane concentration in the biogas is improved.

Compared with the comparative example 2, under the condition of not adding the first biogas slurry, when only the vinasse and the wastewater are used for anaerobic fermentation, the COD volume load of the feeding wastewater is less than or equal to 1.62kg COD/(m) ³ D) the fermentation process can be run smoothly; in the application, the first biogas slurry is used for inoculating the wastewater, so that the COD content of the wastewater and the pH of the wastewater are reduced, and the COD volume load of the feeding wastewater reaches 3.28kg COD/(m) of ³ D), the processing ability and the processing effect are good.

In summary, the method for mixed anaerobic fermentation of wastewater and distillers' grains provided by the application mixes the wastewater with the first biogas slurry to obtain a first mixed solution meeting a first preset condition, inoculates the wastewater with the first biogas slurry to reduce the COD content of the wastewater and the pH of the wastewater, ensures that the wastewater does not generate too much impact on the fermentation process, and avoids acidification of a fermentation system caused by too high COD in the wastewater, which finally causes reduction and even stop of gas production capacity; the first mixed liquor and the vinasse are mixed and then subjected to anaerobic fermentation, so that high-concentration wastewater can be treated, the discharge amount of the wastewater is reduced, the gas production rate can be increased, and the income is increased; meanwhile, the second biogas slurry obtained after anaerobic fermentation can be recycled as the first biogas slurry, so that the discharge amount of wastewater is reduced, the treatment cost is greatly reduced, and economic and environment-friendly treatment of high-concentration wastewater is realized.

It should be noted that, during actual operation, the whole anaerobic fermentation process may be a discontinuous feeding and discharging process, the total volume of the second mixed solution for each fermentation is less than or equal to the effective volume of the fermentation device, at this time, the first biogas slurry, the wastewater and the distiller's grains obtained by calculation may be added into the fermentation device for feeding according to the effective volume of the fermentation device, and after the fermentation reaction meets the preset conditions, the fermentation solution is discharged and then fed for the next time.

The whole anaerobic fermentation process can also be a continuous feeding and discharging process, the total volume of the second mixed liquor of each fermentation = the effective volume of the fermentation device/the anaerobic fermentation hydraulic retention time, the first biogas slurry, the wastewater and the vinasse obtained by calculation are all added into the fermentation device for feeding in the first batch according to the effective volume of the fermentation device and the anaerobic fermentation hydraulic retention time, the feeding in the next batch is continued at the same feeding amount after a certain time (for example, one day) interval, the feeding is continued in this way, meanwhile, after the fermentation reaction of the first batch meets the preset conditions, the reaction liquid of the first batch is discharged, after a certain time interval, after the fermentation reaction of the second batch meets the preset conditions, the reaction liquid of the second batch is continuously discharged, and then the feeding and discharging are continued.

Example 2

Referring to fig. 15, the present application also provides an anaerobic fermenter comprising: jar body 1, it is used for holding and gives the cavity of material reaction, is provided with the stirring subassembly that is used for the material stirring mixing in it, and 1 top one end of jar body is provided with the feed inlet 9 that is used for the material to get into, is equipped with sealed lid on the

feed inlet

9, and 1 one side bottom of jar body still is equipped with and is used for material exhaust discharge gate 3.

Wherein, the stirring subassembly includes puddler 7 to and even annular array sets up stirring leaf 6 at puddler 7 outer wall, and the top of stirring subassembly still is connected with its pivoted timing actuating mechanism of drive. The timing driving mechanism comprises a motor 10 and a timer 8 for controlling the motor 10 to work regularly, the motor 10 is fixedly installed at the center of the top of the tank body 1, and the bottom output end of the motor 1 is connected with the top end of the stirring rod 7.

Specifically, the outer wall of the tank body 1 is also provided with a water bath jacket 2, the water bath jacket 2 heats the tank body 1 through a heat conducting medium, the bottom end of one side of the water bath jacket 2 is provided with a water inlet 5, and the top end of the other side is provided with a water outlet 4.

Specifically, the top of the tank body 1 is further provided with a biogas pipeline 15 for outputting biogas outwards, and a detection pipeline 14 for monitoring COD volume load, daily gas production, methane content, pH and the like in the fermentation tank. The gas outlet end of the biogas pipeline 15 is connected with the gas bag 11, and the biogas pipeline 15 is sleeved with a wet gas flowmeter 12 for measuring the volume of the output biogas. The gas bag 11 is also provided with an exhaust valve 13 for discharging the stored biogas.

It should be noted that, all the cover is equipped with the on-off valve on discharge gate 3 and the detection pipeline 14 to guarantee the leakproofness of jar body 1 in the fermentation process.

Those of ordinary skill in the art will understand that: the discussion of any embodiment above is meant to be exemplary only, and is not intended to intimate that the scope of the disclosure, including the claims, is limited to these examples; within the idea of the present disclosure, also technical features in the above embodiments or in different embodiments may be combined, steps may be implemented in any order, and there are many other variations of the different aspects of the embodiments of the present disclosure as described above, which are not provided in detail for the sake of brevity.

The disclosed embodiments are intended to embrace all such alternatives, modifications and variances which fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalents, improvements, and the like that may be made without departing from the spirit or scope of the embodiments of the present disclosure are intended to be included within the scope of the disclosure.

Claims

1. The anaerobic fermentation method for mixing the wastewater and the vinasse is characterized by comprising the following steps of:

mixing the first mixed solution with vinasse to obtain a second mixed solution;

carrying out anaerobic fermentation on the second mixed liquor, collecting biogas generated in the anaerobic fermentation process, and continuously measuring process parameters in the anaerobic fermentation process until the process parameters meet second preset conditions;

2. The method of claim 1, wherein the first pre-fermentation step comprises mixing the wastewater with the distiller's grainsThe conditions are as follows: the feeding COD volume load of the wastewater is less than or equal to 3-4 kg COD/(m) ³ ·d)。

3. The method of anaerobic fermentation of wastewater mixed with distillers grains according to claim 1, wherein the process parameters comprise: anaerobic fermentation hydraulic retention time, unit gas production of the biogas, methane content in the biogas, and/or pH of the second mixed liquor.

4. The method for anaerobic fermentation of wastewater mixed with distiller's grains according to claim 3, wherein the second preset condition comprises: the anaerobic fermentation hydraulic retention time reaches a preset time, the first difference ratio of the unit gas production rates of two adjacent units is not more than 10%, the methane content in the methane is not less than 50%, and the pH of the second mixed solution is = 6-8.

5. The method for anaerobic fermentation of wastewater mixed with distiller's grains according to claim 1, wherein the feed volume of wastewater is calculated by the formula: v1= (V) ₀ *a)/n，

Wherein V1 is the feed volume of the wastewater; v ₀ Is the effective volume of the fermentation device; a is the feed COD volume load of the wastewater; and n is the COD concentration of the wastewater.

6. The method for anaerobic fermentation of wastewater mixed with distiller's grains according to claim 1, wherein the dry matter feed quality of the distiller's grains is calculated by the following formula: m2= b V,

7. The method of claim 6, wherein the concentration of dry matter in the second mixed solution is 15% or less.

8. The method for anaerobic fermentation of wastewater mixed with distiller's grains according to claim 6, wherein the concentration of dry matter in the second mixed solution is 6-10%.

9. The method for anaerobic fermentation of wastewater mixed with distiller's grains according to claim 1, wherein the calculation formula of the feed volume of the first biogas slurry is as follows: v3= V-V1-V2,

10. The method of mixed anaerobic fermentation of wastewater and distillers grains according to claim 1, wherein the first biogas slurry and the second biogas slurry are non-aerated biogas slurries.