CN114380636A

CN114380636A - Method for preparing humus liquid fertilizer by using cow breeding wastewater

Info

Publication number: CN114380636A
Application number: CN202111545116.XA
Authority: CN
Inventors: 王连杰; 彭金利; 李金河; 姜威; 赵立伟; 张麟; 王瀚卿; 刘鹏
Original assignee: TIANJIN CAPITAL ENVIRONMENTAL PROTECTION GROUP CO Ltd
Current assignee: TIANJIN CAPITAL ENVIRONMENTAL PROTECTION GROUP CO Ltd
Priority date: 2021-12-16
Filing date: 2021-12-16
Publication date: 2022-04-22

Abstract

The invention discloses a method for preparing a humus liquid fertilizer by using cow breeding wastewater, which comprises the following steps: pretreating wastewater of a dairy farm; carrying out anaerobic fermentation treatment on the pretreated wastewater; carrying out solid-liquid separation on the wastewater after anaerobic fermentation; performing secondary foam separation on the waste water obtained by centrifugation to obtain defoaming liquid, and naturally breaking foams and digesting the defoaming liquid to form concentrated liquid; and filtering the obtained concentrated liquid to obtain the liquid fertilizer. The method for extracting the humus liquid fertilizer from the wastewater has the characteristics of quick-acting, long-acting and continuous fertilizer supply, can effectively improve the soil, is favorable for fully realizing the recycling of the cow breeding wastewater, and has important significance for saving energy, reducing consumption and even increasing income; meanwhile, organic matters in the wastewater are removed before entering the biological treatment process, so that the content of foaming substances can be reduced, the stability of a biochemical system is improved, and the normal operation of the biochemical treatment process is ensured.

Description

Method for preparing humus liquid fertilizer by using cow breeding wastewater

Technical Field

The invention relates to the technical field of resource utilization of livestock breeding wastes, in particular to a method for preparing a humus liquid fertilizer by using dairy cow breeding wastewater.

Background

The large-scale livestock and poultry farm can generate a large amount of accumulated excrement and wastewater every day, and the pollution of livestock and poultry breeding becomes one of the main causes of pollution in China. The cow breeding wastewater is typical livestock breeding wastewater, belongs to high-concentration degradation-resistant organic wastewater, and often contains high-concentration organic matters and degradation-resistant substances such as soluble protein, polysaccharide, humic acid, cellulose and the like, and the cow breeding scale, breeding mode, pollution treatment mode and management mode are different, so that the water quality and water quantity change is large. These characteristics result in the characteristics of high pollution and high difficulty in treatment of the livestock and poultry breeding wastewater.

At present, the treatment process used by the dairy cow breeding industry wastewater at home and abroad roughly comprises the following steps: primary solid-liquid separation, anaerobic treatment, secondary solid-liquid separation, biochemical treatment and stable pond treatment. After the wastewater is treated in the whole process, the wastewater can be discharged up to the standard according to the discharge standard of pollutants for livestock and poultry breeding industry GB 18596, the discharged wastewater can water nearby farmlands (meeting the Standard of Water quality for Farmland irrigation (GB 5084), biogas generated by anaerobic fermentation can be used as fuel and comprehensively utilized, waste materials after solid-liquid separation are processed into granular fertilizer, and the discharged water can be reused and comprehensively utilized as flushing water after reaching the standard.

Moreover, biogas slurry after anaerobic treatment often contains a large amount of surfactants and surface active substances such as starch, protein, grease and the like, and the molecular structure of the surfactants and the surface active substances is represented as containing polar-nonpolar groups, namely, amphiphilic molecules. Under the condition of aeration, one end of a non-polar group extends into the air bubble, and the polar group is selectively adsorbed by the hydrophilic substance, so that the surface of the hydrophilic substance is converted into a hydrophobic substance to be adhered to an air bubble water film, a water body can generate a plurality of foams after entering an aerobic treatment process, the common amount of the foams is large and stable, and the foams overflow from the pool body can cause serious pollution to the external pool wall of external equipment, so that the operation condition is worsened, and the normal maintenance is influenced. In winter, the biological foam can be frozen and is difficult to clean; in summer, the wind will drift, forming bad smell and seriously affecting the surrounding environment.

The cow breeding wastewater is a pollution source and also an available resource, the nutrient content of the wastewater is rich, not only various mineral nutrients required by crops are contained, but also the mineral elements of the wastewater are mostly in quick-acting and easily-soluble forms, and if the mineral elements are simply removed as pollutants, a large amount of valuable nutrient substances are wasted in vain. Realizes the resource utilization of the culture wastewater, changes waste into valuable and is a good way for pollution treatment.

Disclosure of Invention

The invention aims to solve the technical problems and provides a method for preparing a humus liquid fertilizer by using cow breeding wastewater.

The invention adopts the following technical scheme.

A method for preparing a humus liquid fertilizer by using cow breeding wastewater comprises the following steps:

s1, pretreating wastewater of a dairy farm;

s2, carrying out anaerobic fermentation treatment on the pretreated wastewater;

s3, performing solid-liquid separation on the wastewater after anaerobic fermentation;

s4, performing secondary foam separation on the waste water obtained by centrifugation to obtain defoaming liquid, and naturally breaking foams and digesting the defoaming liquid to form concentrated liquid;

and S5, filtering the obtained concentrated liquid to obtain the liquid fertilizer.

Further, in step S1, the preprocessing method includes: removing suspended solids and feces in the wastewater by adopting a 5-20 mm grid or a solid-liquid separator, then carrying out precipitation treatment to remove suspended matters with specific gravity larger than that of water, and enabling the wastewater after the precipitation treatment to enter an adjusting tank, wherein the hydraulic retention time of the adjusting tank is 0.5-2.5 h.

Furthermore, in step S2, SS in the influent water of the anaerobic reaction is controlled to be 1000-2500 mg/L.

Further, in step S3, after the anaerobic reaction, the product is sent to a 50-200 mesh centrifugal solid-liquid separator, and the centrifugal speed is 2500-3500 rpm.

Further, in the step S4, the gas-water ratio of the primary foam separation is 10-50, the temperature is 5-40 ℃, the hydraulic retention time is 1-5 hours, the pH of the reaction system is controlled at 5-8, and the concentrated solution accounts for 15% -20%; the gas-water ratio of the secondary foam separation is 60-100, the temperature is 5-40 ℃, the hydraulic retention time is 1-5 hours, the pH of the reaction system is controlled at 5-8, and the concentrated solution accounts for 25-80%.

Further, in step S5, carrying out plate-and-frame filtration on concentrated liquid with an organic matter concentration ratio of 5-15 to obtain the liquid fertilizer.

Further, the plate-and-frame filtration conditions are as follows: the starting pressure is controlled to be 0.1-0.15 MPa, the pressure in a filter pressing stage after normal operation is controlled to be 0.15-0.2 MPa, and the filtering area is 100-500 square.

Further, the solid obtained after pretreatment, the solid obtained after anaerobic reaction centrifugation and the solid obtained after plate-frame filtration are subjected to livestock bedding preparation or aerobic composting treatment.

The present invention obtains the following advantageous effects.

1. Simple equipment and easy separation conditions

The method adopts the foam separation technology, does not need to add other solvents in the separation process, only needs to introduce redundant gas sources in the normal sewage treatment process into the separation equipment, and has the advantages of simple equipment structure, low energy consumption, low cost, convenient operation and maintenance, capability of operating at normal temperature and low temperature and the like;

2. low cost and high efficiency for producing concentrated liquid fertilizer

The livestock and poultry breeding wastewater after anaerobic treatment contains a large amount of soluble protein, polysaccharide, humic acid, cellulose and the like, foams have the functions of trapping and concentrating the substances, and defoaming solution after foam coalescence contains high-concentration protein and polysaccharide, also contains 17 amino acids, various types of humic acid, polybasic organic acid, various relatively healthy plant growth regulators, B vitamins and the like, and has the effects of promoting the growth of crops and inhibiting organic matters caused by plant diseases and insect pests. The method for extracting the humus liquid fertilizer from the wastewater has the characteristics of quick-acting, long-acting and continuous fertilizer supply, can effectively improve the soil, is favorable for fully realizing the recycling of the cow breeding wastewater, and has important significance for saving energy, reducing consumption and even increasing income;

3. reduce foam and ensure normal operation of biochemical treatment process

Organic matters in the wastewater are removed before entering the biological treatment process, so that the content of foaming substances can be reduced, the stability of a subsequent biochemical system is improved, and the normal operation of the biochemical treatment process is ensured.

Drawings

FIG. 1 is a flow diagram of the production of a humic liquid fertilizer of the invention;

FIG. 2 is a schematic diagram of the structure of a two-stage foam separation column of the present invention.

Wherein, 1, foam reflux pipe; 2. a water inlet pump; 3. a water inlet; 4. a foam separation column; 5. an inner rectifying sleeve; 6. a separation tower ear mount; 7. a foam outlet; 8. a liquid level meter; 9. a gas distributor; 10. a raffinate outlet valve; 11. a raffinate discharge pipe valve; 12. a raffinate discharge pipe; 13. emptying the pipe; 14. an evacuation valve; 15. an air blowing valve; 16. a gas flow meter; 17. a stirring motor; 18. a gas compressor; 19. a centrifugal pump; 20. a foam separation raffinate outlet; 21. a feed tank; 22. and (5) a defoaming pool.

Detailed Description

The present invention will be further described with reference to examples.

The invention provides a recycling process for preparing liquid fertilizer by using cow breeding wastewater, which effectively reduces the content of foaming substances under the conditions of low energy consumption and no use of a chemical defoaming agent, is beneficial to improving the stability of a subsequent biochemical system, and is more beneficial to fully realizing the recycling of the cow breeding wastewater. The specific process flow is as follows:

1. suspended solids and excrement residues are removed by adopting a coarse grating and a special cow dung wastewater solid-liquid separator, then suspended solids heavier than water are separated from the water by adopting a primary sedimentation tank, and the large-particle-size forage scraps, animal hair and excrement residues filtered by the grating (5-20 mm), the primary sedimentation tank and a solid-liquid separation/centrifugal process can be used as a livestock bedding or aerobic compost for recycling after drying.

2. And (4) enabling the effluent of the primary sedimentation tank to enter an adjusting tank, wherein the hydraulic retention time of the adjusting tank is 0.5-2 h.

3. The effluent of the regulating tank enters anaerobic fermentation, and an anaerobic reactor used for fermentation does not need mixing and stirring equipment, and not only ensures that the sludge on the upper part of a sludge bed is in a suspended state, but also is beneficial to the degradation of organic matters by depending on the rising motion of the methane generated in the process of water flow and fermentation; SS in the inlet water of the anaerobic reactor is controlled to be 1000-2000 mg/L. The methane generated by the anaerobic reactor is used as a sewage treatment system for heating.

4. Anaerobic effluent needs to be treated by a centrifugal solid-liquid separation means, a centrifuge is selected from 50-200 meshes, the centrifugal rotating speed is 2500-3500 rpm, solid matters in sewage are further filtered, and the filtered matters can be recycled as a cowshed bedding or fertilizer after being dried.

5. And the anaerobic effluent after centrifugal separation enters foam separation equipment. The foam separation equipment is divided into two stages, wherein defoaming liquid generated by the first stage foam separation is used for preparing liquid fertilizer, and first stage residual liquid is conveyed to second stage foam separation equipment; and defoaming liquid generated by secondary foam separation is combined with primary foam separation liquid and then enters primary foam separation equipment again, and secondary residual liquid is conveyed to a biochemical sewage treatment process.

The specific foam separation process is as follows:

A. the anaerobic effluent after centrifugal separation enters a feeding pool 21, the feeding speed is about 5-8 times of the target production energy of the intermediate product of the humic acid liquid fertilizer, and the mixture is stirred and homogenized by a stirring motor 17 and then is pumped into a primary foam separation tower through a water inlet 3 by a water inlet pump 2;

B. a rectification inner sleeve 5 is arranged in the foam separation tower 4, and the outer diameter of the rectification inner sleeve 5 is 65-85% of the inner diameter of the foam separation tower 4. The foam separation tower 4 is provided with a separation tower ear seat 6 for fixing, the upper end is provided with a foam outlet 7, the tower body is provided with a liquid level meter 8, the tower bottom is provided with a gas distributor 9, the gas distributor 9 is connected with a gas pipeline, the gas pipeline is provided with a gas flow meter 16 and a gas blowing valve 15, the gas pipeline is also connected with an emptying pipe 13, and the emptying pipe 13 is provided with an emptying valve 14. The residual liquid is discharged out of the separation tower through a residual liquid discharge pipeline at the bottom of the tower, a residual liquid outlet valve 10 is arranged on the residual liquid discharge pipeline at the bottom of the tower, the residual liquid discharge pipeline at the bottom of the tower is also connected with a residual liquid discharge pipe 12, and a residual liquid discharge pipe valve 11 is arranged on the residual liquid discharge pipe 12;

C. the gas compressor 18 pumps compressed air into the foam separation tower 4, the compressed air generates bubbles in the foam separation tower 4 through the gas distributor 9, the generated bubbles rise along the rectification inner sleeve 5 to be separated from the separation liquid level, and the liquid level, the rectification inner sleeve 5 and the water inlet 3 are controlled to be at the same height;

D. the gas-water ratio of the primary foam separation is 10-50, the temperature is 5-40 ℃, the hydraulic retention time is 1-5 hours, the pH of a reaction system is controlled at 5-8, and the concentrated solution accounts for 15-20%. The foam enters a defoaming pool 22 through a foam outlet 7, and is broken into foam after 1-2 hours under the stirring of a stirring motor 17 to form a concentrated solution. And (3) carrying out plate-frame filtration treatment after the concentration ratio of organic matters in the concentrated solution reaches 5-15, controlling the starting pressure of the plate-frame filtration to be 0.1-0.15 MPa, and controlling the pressure of a filter pressing stage to be 0.15-0.2 MPa after normal operation and the filtration area to be 100-500 square. And (3) filtering by a plate frame to separate scum and suspended matters from the liquid, wherein the liquid is a prepared liquid fertilizer intermediate product, and the scum and suspended matters can be dried and then can be used as a livestock and poultry bedding or aerobic compost for recycling.

E. The residual liquid of the first-stage foam separation enters the water inlet 3 of the second-stage foam separation tower from a residual liquid discharge pipeline at the bottom of the tower through a centrifugal pump 19, and the second-stage separation process is started. The second-stage feeding speed is 80-90% of the first-stage feeding speed;

F. the gas-water ratio of the secondary foam separation is 60-100, the temperature is 5-40 ℃, the hydraulic retention time is 1-5 hours, the pH of the reaction system is controlled at 5-8, and the concentrated solution accounts for 25-80%. The foam obtained by the secondary foam separation enters a feeding tank 21 through a foam return pipe 1, is broken under the stirring of a stirring motor 17, is fully and uniformly mixed with the anaerobic effluent, and enters the water inlet of the primary foam separation tower again;

G. the residual liquid of the separation process is discharged from a foam separation residual liquid outlet 20 at the bottom of the secondary foam separation tower into the next stage biological treatment process for further treatment. The residual liquid discharge speed is about 55-75% of the secondary feeding speed.

Example 1

The water quality indexes of the cow breeding wastewater are as follows:

COD(mg/L)	SS(mg/L)	NH3-N(mg/L)	TN(mg/L)	TP(mg/L)	viscosity (mPa. S)
						42300	34200	1760	3800	450	9

(1) Firstly, filtering forage scraps, animal hairs and the like with large particle sizes from the wastewater of a dairy farm by a 15-20 mm grid/solid-liquid separator, preliminarily removing silt and organic matters with large specific gravity from the wastewater by a primary sedimentation tank, feeding the effluent of the primary sedimentation tank into an adjusting tank, enabling the hydraulic retention time of the adjusting tank to be 1.5-2.5 hours, and conveying the effluent to an anaerobic reactor through a pipeline;

(2) organic matters are fully degraded after anaerobic fermentation treatment of the anaerobic reactor, the generated methane can be used as a sewage treatment system for heating, and the redundant methane can be used as clean energy for comprehensive utilization; feeding waste materials in the anaerobic reactor into a 100-200-mesh centrifugal solid-liquid separator to obtain separated solid and liquid, wherein the solid is used as a composting material, and the liquid enters a subsequent treatment process;

the effluent indexes of the anaerobic reactor are as follows:

total nitrogen/%)	Total phosphorus/%)	Organic matter/%	Humic acid/%
				0.253	0.0448	3.130	0.140

(3) The gas-water ratio of the primary foam separation is 15-20, the temperature is 25-30 ℃, the hydraulic retention time is 3-4 hours, the pH of a reaction system is controlled at 7-8, and the concentrated solution accounts for 15-20%. The gas-water ratio of the secondary foam separation is 60-85, the temperature is 25-30 ℃, the hydraulic retention time is 1.5-2 h, the pH of the reaction system is controlled at 6-7, and the concentrated solution accounts for 25-45%;

the indexes of the concentrated solution of the foam separation equipment are as follows:

total nitrogen/%)	Total phosphorus/%)	Organic matter/%	Humic acid/%
				0.115	0.058	10.016	0.480

Example 2

The water quality indexes of the cow breeding wastewater are as follows:

COD(mg/L)	SS(mg/L)	NH3-N(mg/L)	TN(mg/L)	TP(mg/L)	viscosity (mPa. S)
						43600	32000	1980	3600	460	9

(1) Firstly, passing the wastewater of a dairy farm through a 10-20 mm grid/solid-liquid separator, and conveying the liquid to an anaerobic reactor through a pipeline;

(2) feeding the discharged material in the anaerobic reactor into a 150-200 mesh centrifugal solid-liquid separator to obtain separated solid and liquid, wherein the solid is used as a composting material, and the liquid enters a subsequent treatment process;

the effluent indexes of the anaerobic reactor are as follows:

total nitrogen/%)	Total phosphorus/%)	Organic matter/%	Humic acid/%
				0.282	0.0421	3.220	0.110

(3) The gas-water ratio of the primary foam separation is 15-20, the temperature is 25-35 ℃, the hydraulic retention time is 4-4.5 h, the pH of a reaction system is controlled at 7-8, and the concentrated solution accounts for 15-18%. The gas-water ratio of the secondary foam separation is 62-88, the temperature is 25-30 ℃, the hydraulic retention time is 1.5-2.5 h, the pH of the reaction system is controlled at 6-7, and the concentrated solution accounts for 25-45%;

total nitrogen/%)	Total phosphorus/%)	Organic matter/%	Humic acid/%
				0.122	0.051	13.048	0.502

The embodiments of the present invention are preferred embodiments of the present invention, and the scope of the present invention is not limited by these embodiments, so: all equivalent changes made according to the structure, shape and principle of the invention are covered by the protection scope of the invention.

Claims

1. A method for preparing a humus liquid fertilizer by using cow breeding wastewater is characterized by comprising the following steps: the method comprises the following steps:

s1, pretreating wastewater of a dairy farm;

s2, carrying out anaerobic fermentation treatment on the pretreated wastewater;

2. The method for preparing the humic liquid fertilizer by using the dairy cow breeding wastewater as claimed in claim 1, which is characterized in that: in step S1, the preprocessing method includes: removing suspended solids and feces in the wastewater by adopting a 5-20 mm grid or a solid-liquid separator, then carrying out precipitation treatment to remove suspended matters with specific gravity larger than that of water, and enabling the wastewater after the precipitation treatment to enter an adjusting tank, wherein the hydraulic retention time of the adjusting tank is 0.5-2.5 h.

3. The method for preparing the humic liquid fertilizer by using the dairy cow breeding wastewater as claimed in claim 1, which is characterized in that: in step S2, SS in the influent water of the anaerobic reaction is controlled to be 1000-2500 mg/L.

4. The method for preparing the humic liquid fertilizer by using the dairy cow breeding wastewater as claimed in claim 1, which is characterized in that: in step S3, after the anaerobic reaction, the product is sent to a 50-200 mesh centrifugal solid-liquid separator, and the centrifugal speed is 2500-3500 rpm.

5. The method for preparing the humic liquid fertilizer by using the dairy cow breeding wastewater as claimed in claim 1, which is characterized in that: in the step S4, the gas-water ratio of primary foam separation is 10-50, the temperature is 5-40 ℃, the hydraulic retention time is 1-5 h, the pH of a reaction system is controlled at 5-8, and the concentrated solution accounts for 15% -20%; the gas-water ratio of the secondary foam separation is 60-100, the temperature is 5-40 ℃, the hydraulic retention time is 1-5 hours, the pH of the reaction system is controlled at 5-8, and the concentrated solution accounts for 25-80%.

6. The method for preparing the humic liquid fertilizer by using the dairy cow breeding wastewater as claimed in claim 1, which is characterized in that: in the step S5, carrying out plate-and-frame filtration on concentrated liquid with an organic matter concentration ratio of 5-15 to obtain the liquid fertilizer.

7. The method for preparing the humic liquid fertilizer by using the dairy cow breeding wastewater as claimed in claim 6, wherein the method comprises the following steps: the plate-frame filtration conditions were: the starting pressure is controlled to be 0.1-0.15 MPa, the pressure in a filter pressing stage after normal operation is controlled to be 0.15-0.2 MPa, and the filtering area is 100-500 square.

8. The method for preparing the humic liquid fertilizer by using the dairy cow breeding wastewater as claimed in claim 7, wherein the method comprises the following steps: and (3) carrying out livestock bedding manufacture or aerobic composting treatment on the solid matters obtained after pretreatment, the solid matters obtained after anaerobic reaction centrifugation and the solid matters obtained by plate-and-frame filtration.