A method and system for treating fecal wastewater

Abstract

The present invention provides a method and system for treating manure wastewater, and the treatment method includes the steps of solid-liquid separation, production of carbon source and hydrogen sulfide, removal of COD pollutants, anaerobic ammonia oxidation denitrification, short-term nitrification and denitrification denitrification, etc. The treatment system includes: a solid-liquid separation unit; a CS production unit, which is mainly used to obtain carbon source and hydrogen sulfide by using acid-producing dominant bacteria and sulfur bacteria, including an acid-producing anaerobic tank, an acid-adjusting stripping tank, an absorption tower, and a neutralization tank; a biogas-producing anaerobic unit; an anaerobic ammonia oxidation unit; a short-term nitrification and denitrification unit; and also includes a clear water tank and a circulating pump. The present invention first reduces the COD concentration and ammonia nitrogen concentration in sewage through solid-liquid separation, and can remove total nitrogen by creating economic carbon sources and hydrogen sulfide by itself, and can achieve the standard discharge of COD and ammonia nitrogen in aquaculture manure wastewater with high efficiency and low cost, and at the same time can reduce the use of chemical flocculants and reduce the risk of secondary pollution.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and in particular to a method and system for treating fecal wastewater. Background Art

[0002] Livestock manure wastewater mainly includes animal feces and flushing water, which contains a large amount of organic pollutants, pathogens, and pollutants such as ammonia nitrogen and phosphorus. Among them, the organic pollutant indicators COD and ammonia nitrogen (NH3-N) are hundreds of times the concentration of domestic sewage, which is extremely difficult to treat and it is difficult to achieve standard emissions.

[0003] At present, the main difficulties in treating fecal wastewater are as follows:

[0004] 1. The high concentration of organic pollutants in raw water can reach more than 30,000 mg / L, while the standard for farmland irrigation is only below 300 mg / L. It is necessary to remove 99% of organic pollutants. Since the water contains a large amount of humic acid, lignin and other pollutants that are difficult to degrade, a large number of process treatment units need to be connected in series to achieve the COD discharge standard, which requires huge project investment;

[0005] 2. The ammonia nitrogen concentration of raw water can reach 2000-3000 mg / L. The ammonia nitrogen emission limit in the pollutant emission standard for livestock and poultry breeding is 80 mg / L. The treatment of ammonia nitrogen is not only more difficult than that of organic matter, but also requires a large amount of oxygenation power consumption and a large amount of organic carbon source consumption during the treatment process. The use of aeration will greatly increase the cost of wastewater treatment;

[0006] 3. The process routes of removing COD (anaerobic method) and removing ammonia nitrogen (oxygen consumption) are contradictory and even restrict each other. The existing technology generally adopts the following four process routes to treat fecal wastewater:

[0007] 1) Using anaerobic microorganisms to produce biogas to remove COD from high-concentration wastewater is a relatively mature technology that can save treatment costs and power consumption, and generate biogas revenue. However, the anaerobic biogas production process has no effect on the removal of ammonia nitrogen, and cannot simultaneously remove ammonia nitrogen from manure wastewater with high efficiency and low cost, and achieve simultaneous compliance with discharge standards.

[0008] 2) The raw sewage is first aerobic to remove ammonia nitrogen. During the denitrification process, a large amount of organic pollutants COD will be simultaneously oxidized in the aerobic environment of oxidizing ammonia nitrogen, thereby consuming a large amount of power for aeration and oxygenation. The electricity cost for aeration of one ton of water treatment can reach nearly 20 yuan, which requires a huge investment in aerobic systems and high operating costs.

[0009] 3) Based on route 1), firstly carry out anaerobic biogas production to remove COD, and then purchase commercial carbon source drugs to remove ammonia nitrogen pollutants. The industrial carbon sources that can be purchased include methanol, sodium acetate, etc. The cost of carbon sources for this route makes the removal of ammonia nitrogen per ton of water as high as tens of yuan.

[0010] 4) A portion of the manure and sewage raw water is retained as a carbon source for denitrification and does not enter the anaerobic unit; the other raw water is anaerobically treated to remove COD, and the wastewater containing ammonia nitrogen after anaerobic treatment is mixed with part of the raw water used as a carbon source in the front section for denitrification treatment. This method takes into account both the low-cost COD treatment at the front end and the carbon source demand for removing ammonia nitrogen in the back section. For example, the high-nitrogen and high-concentration organic wastewater treatment process disclosed in the Chinese patent document with publication number CN1762852A. However, this technical route also has shortcomings, because the concentration of COD that is difficult to degrade in the raw water is high, and part of the raw water used as a carbon source directly surpasses the aerobic section of denitrification. The treatment process units and processes of this part of the raw water are greatly reduced, so the risk of exceeding the COD index of the treated effluent is greatly increased, and it is very likely that the emission standards (such as the standard requirement for farmland irrigation is less than 300 mg / L) cannot be achieved, and the standard discharge cannot be achieved.

[0011] 4. There are very few industrial economic and reliable carbon sources for denitrification, and it is necessary to seek economical and cheap carbon sources. For example, the Chinese patent document with publication number CN106967759A discloses a method for producing volatile acid by co-fermentation of straw conditioning sludge by short-time low-temperature heat pretreatment. This method converts straw (mainly cellulose alkaline hydrolysis) and sludge into volatile acid by co-fermentation under alkaline conditions, and the volatile acid carbon source can be used for sewage treatment. However, there are also the following shortcomings in this method: First, the method obtains a high-concentration wastewater mixed with volatile acid, and the volatile acid and wastewater are difficult to separate under alkaline conditions and are difficult to be directly used by other denitrification processes; secondly, livestock and poultry need calcium supplementation, the hardness of wastewater is relatively large, and the scaling risk of feces and sewage under alkaline conditions is greatly increased, which will cause pipeline equipment blockage; thirdly, the difficult-to-degrade pollutants contained in the added straw will increase the difficulty of reaching the COD standard for sewage treatment, and it is impossible to achieve standard discharge; fourthly, raw straw is not easy to obtain, and for ordinary feces and sewage treatment stations, a series of processes such as outsourcing, storage, and crushing are required.

[0012] Based on the above, it is urgent to develop a method and system for treating livestock manure wastewater that can achieve efficient and low-cost discharge of COD and ammonia nitrogen in livestock manure wastewater in compliance with emission standards. Summary of the invention

[0013] The technical problem to be solved by the present invention is to provide a method and system for treating manure wastewater, which can achieve the standard discharge of COD and ammonia nitrogen in aquaculture manure wastewater with high efficiency and low cost, and at the same time reduce the use of chemical flocculants and reduce the risk of secondary pollution.

[0014] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0015] In a first aspect, the present invention provides a method for treating fecal wastewater, which specifically comprises the following steps:

[0016] S1, solid-liquid separation: The fecal wastewater enters the solid-liquid separation unit to remove the suspended solids in the raw water, and the filtered wastewater enters the next treatment unit;

[0017] S2. Production of carbon source and hydrogen sulfide:

[0018] S201, the sewage filtered in step S1 enters the acidogenic anaerobic tank, and acidogenic dominant bacteria and sulfate-reducing bacteria (SRB) are added at 1-10 ppm, the acidogenic dominant bacteria are used to lyse the macromolecular pollutants in the sewage and convert them into small molecular organic acid carbon sources, and the sulfate-reducing bacteria are used to convert sulfur in the water into hydrogen sulfide;

[0019] Preferably, the acid-producing dominant bacteria include: at least two of: Bacillus formigenes, propionate-eating hydrogen-producing acetogens, Clostridium butyricum, and butyrate-eating hydrogen-producing acetogens; these acid-producing dominant bacteria are used to convert macromolecular organic matter in water into small molecular acids such as formic acid, acetic acid, propionic acid, and butyric acid;

[0020] S202, a part of the wastewater from the acid-generating anaerobic tank in step S201 enters the acid-adjusting and air-stripping tank, and the pH is adjusted to 1.0-4.0. Under weakly acidic conditions, the carbon source and hydrogen sulfide in this part of the wastewater are blown out by air into the absorption tower;

[0021] S203, the absorption tower uses clean water to wash out the carbon source and hydrogen sulfide in the air, transfers the carbon source and hydrogen sulfide from the gas phase to the liquid phase, and obtains a clean water solution containing the carbon source and hydrogen sulfide; the eluted air is recycled and enters the acid stripping tank in step S202;

[0022] S204: After the carbon source and hydrogen sulfide are blown off in step S202, the wastewater enters the neutralization tank and is adjusted to weak alkalinity (to ensure the alkalinity requirements of the subsequent biological unit). The treatment conditions are: pH = 7-8, HRT = 1-5 minutes;

[0023] S3, removal of COD pollutants: the weak alkaline wastewater discharged from the neutralization tank in step S204 and the remaining acid-producing wastewater discharged from the acid-producing anaerobic tank in step S201 enter the biogas-producing anaerobic unit, and after anaerobic reaction treatment, more than 75% of the COD pollutants in the wastewater are converted into biomass energy biogas, which provides energy for its own medium-temperature anaerobic conditions; the treatment conditions are: pH = 7-8.5, T = 35-40 ° C, HRT = 1-5 days, and the effluent SS < 1000 mg / L;

[0024] S4, anaerobic ammonium oxidation denitrification: the sewage treated in step S3 enters the aerated nitrite and denitrification split anaerobic ammonium oxidation unit, and the chemoautotrophic bacteria anaerobic ammonium oxidizing bacteria are used to remove most of the total nitrogen. The remaining COD in the water is decomposed to provide the anaerobic ammonium oxidizing bacteria with carbon dioxide required for autotrophic synthesis; the treatment conditions are: pH = 7-8.5, T = 25-35 ° C, BOD < 1.5TN; under this treatment condition, part of the ammonia nitrogen is first converted into nitrite, and then the remaining ammonia and nitrite react to generate nitrogen gas to remove the total nitrogen;

[0025] S5, short-cut nitrification and denitrification: the wastewater after denitrification in step S4 enters the short-cut nitrification and denitrification unit for further denitrification, and is introduced into the aqueous solution containing carbon source and hydrogen sulfide in step S203, and the denitrification process in the unit using carbon source and hydrogen sulfide as hydrogen donors further removes total nitrogen;

[0026] S6. The water treated in step S5 enters the clean water tank and provides clean water for elution to the absorption tower in step S203 through a circulation pump, and the remaining water is discharged or reused.

[0027] The reaction principle involved in the above scheme of the present invention is:

[0028] 1. Step S4 uses anaerobic ammonium oxidation process for denitrification. The denitrification principle of this process in the present invention is as follows:

[0029] 2NH4 + +3O2→2HNO2+2H2O+2H +

[0030] NH4 + +1.32NO2 - +0.066HCO3 - +0.13H + →1.02N2+0.26NO3 - +0.066CH2O 0.5 N 0.15 +2.03H2O

[0031] The anaerobic ammonium oxidation sludge used in this process is red, also known as red bacteria. Its normal operating temperature and suspended solids concentration are relatively strict, but because the water produced by the biogas-producing anaerobic unit S3 in this process can just meet the operating conditions of the S4 anaerobic ammonium oxidation unit, the process in the method of the present invention can remove about 85% of ammonia nitrogen. However, the effluent generally still has 100-300 total nitrogen, which requires further denitrification.

[0032] 2. Step S5 uses a short-range nitrification and denitrification process for denitrification. The denitrification principle of the process in the present invention is as follows:

[0033] 2NH4 ++3O2→2HNO2+2H2O+2H + , 2NO2 - +6e - +8H + →N2+4H2O

[0034] The dissolved oxygen in the S5 short-range nitrification and denitrification unit is controlled within 1PPM, the internal reflow ratio is controlled at more than 10 times, the carbon source and hydrogen sulfide utilization rate is high, and the aeration power is small. This process can cultivate long-sludge autotrophic bacteria that oxidize ammonia to nitrite, and use the carbon source and hydrogen sulfide produced by S2 to provide hydrogen donors for denitrification.

[0035] The anaerobic ammonia oxidation denitrification process of step S4 is suitable for removing high-concentration total nitrogen and is suitable for denitrification under low COD concentrations; the short-range nitrification and denitrification process of step S5 is suitable for removing low-concentration total nitrogen. Step S4 uses chemoautotrophic bacteria anaerobic ammonia oxidizing bacteria to remove most of the total nitrogen, about 85% of the total nitrogen. The dissolved oxygen in the S5 reaction process is relatively high, and the carbon source will be consumed preferentially during nitrification. Therefore, step S5 is not suitable for high-concentration denitrification, and the time should not be too long. The optimal condition is that S5 supplements a new carbon source after nitrification and directly reacts with the nitric nitrogen produced by S5 to remove total nitrogen, which can further remove total nitrogen.

[0036] Further,

[0037] In step S1, the filtration accuracy of the solid-liquid separation unit is controlled within 0.05 mm to remove suspended solids in the raw water, and the generated solids are used for composting and harmless treatment.

[0038] Further,

[0039] In step S201, 5-25% of the wastewater from the acid-producing anaerobic tank enters the acid-adjusting and air-stripping tank to separate the carbon source and hydrogen sulfide; the remaining wastewater enters the biogas-producing anaerobic unit in step S3 and is mixed with the wastewater after the carbon source and hydrogen sulfide are separated for further treatment.

[0040] Preferably,

[0041] The treatment conditions of step S201 are: pH = 4.0-5.5, T = 10-35° C., HRT = 6-48 hours.

[0042] Preferably,

[0043] The processing conditions of step S203 are: pH=8-10, HRT=1-5 seconds.

[0044] Further,

[0045] In step S5, the dissolved oxygen of the short-range nitrification and denitrification unit is controlled within 1 PPM, and the internal reflux ratio is greater than 10; the treatment conditions are: pH = 6.0-8.5, T = 20-35°C.

[0046] Furthermore, small molecule organic acids are organic acids with a molecular weight less than 100, including formic acid, acetic acid, propionic acid and butyric acid.

[0047] In a second aspect, the present invention further provides a treatment system capable of implementing the above-mentioned feces wastewater treatment method, comprising:

[0048] Solid-liquid separation unit, used to remove suspended solids in raw water;

[0049] CS [Carbon Source & Hydrogen Sulfide, referred to as CS] production unit, mainly used to obtain carbon source and hydrogen sulfide by using acid-producing dominant bacteria and sulfate-reducing bacteria, including acid-producing anaerobic tank, acid-adjusting stripping tank, absorption tower, and neutralization tank;

[0050] The biogas-producing anaerobic unit is used to convert COD pollutants in water into biogas by anaerobic reaction, and the heat energy of the biogas combustion is used to meet the anaerobic temperature conditions of the unit;

[0051] Anaerobic ammonium oxidation unit, used to remove high concentrations of total nitrogen from wastewater;

[0052] Short-cut nitrification and denitrification unit, used to further denitrify the effluent from the anaerobic ammonium oxidation unit;

[0053] It also includes a clear water tank and a circulation pump, wherein the clear water tank is used to store the effluent of the short-range nitrification and denitrification unit, and the circulation pump is used to circulate the water in the clear water tank for use as elution water for the absorption tower;

[0054] The liquid outlet of the solid-liquid separation unit is connected to the water inlet of the acid-producing anaerobic tank, the water outlet of the acid-producing anaerobic tank is respectively connected to the water inlets of the acid-adjusting stripping tank and the biogas-producing anaerobic unit, the water outlet of the acid-adjusting stripping tank is connected to the neutralization tank, and its air outlet is connected to the gas inlet of the absorption tower, the gas outlet of the absorption tower is circularly connected to the air inlet of the acid-adjusting stripping tank, the water inlet of the absorption tower is connected to the clear water tank through a circulation pump, and the water outlet of the absorption tower is connected to the short-cut nitrification and denitrification unit; the biogas-producing anaerobic unit, the anaerobic ammonia oxidation unit, the short-cut nitrification and denitrification unit, and the clear water tank are connected in sequence.

[0055] Specifically, the solid-liquid separation unit is a laminated filter or a plate and frame filter press.

[0056] Specifically, the biogas-producing anaerobic unit is an anaerobic reactor with gas-liquid-solid three-phase separation function, in which granular sludge is cultivated. The anaerobic reactor is EGSB, UASB, IC, ICX, etc.

[0057] Specifically, the anaerobic ammonium oxidation unit is an aerated nitrite and denitrification split anaerobic ammonium oxidation unit, specifically an anaerobic ammonium oxidation combined pool, in which anaerobic ammonium oxidation red bacteria sludge of the order Planctomycetes is cultured. The anaerobic ammonium oxidation process of the present invention mainly includes two processes: the stage of ammonia oxidation to nitrite; and the stage of ammonia and nitrite reacting to generate nitrogen gas. Two tank bodies are connected in series to form an anaerobic ammonium oxidation combined pool, and the above two processes are divided into two tank bodies and carried out in series in sequence, which is beneficial to the degradation of excess organic matter in the anaerobic effluent in the first process of ammonia oxidation, and prevents a large amount of organic matter from competing with autotrophic ammonia oxidizing bacteria in the second stage, so that the purity of the red bacteria is reduced and the denitrification capacity is reduced. The denitrification sludge can be circulated between the two tank bodies.

[0058] Specifically, the short-cut nitrification and denitrification unit is a short-cut nitrification and denitrification tank.

[0059] HRT, generally refers to hydraulic retention time, the abbreviation of Hydraulic Retention Time, a water treatment process term, which refers to the average residence time of the sewage to be treated in the reactor.

[0060] VFA generally refers to volatile fatty acids, Volatile Fatty Acid, abbreviated as VFA, generally refers to organic acids with a carbon chain of 1 to 6 carbon atoms, including formic acid, acetic acid, propionic acid, isobutyric acid, valeric acid, isovaleric acid, n-butyric acid, etc. Their common feature is that they are very volatile, so they are called volatile fatty acids.

[0061] SS generally refers to the concentration of suspended solids, the abbreviation of Suspended solid.

[0062] COD, generally refers to Chemical Oxygen Demand, the abbreviation of Chemical Oxygen Demand, which is a chemical method to measure the amount of reducing substances that need to be oxidized in a water sample.

[0063] BOD, generally refers to biochemical oxygen demand, the abbreviation of Biochemical Oxygen Demand, which refers to the amount of dissolved oxygen consumed in the biochemical reaction process of microorganisms decomposing biodegradable organic matter in water under certain conditions.

[0064] Heterotrophic denitrification: Under anaerobic conditions, due to the action of facultative denitrifying bacteria (denitrifying bacteria), nitrite nitrogen and nitrate nitrogen are reduced to nitrogen gas using hydrogen donors. In the heterotrophic denitrification process, a hydrogen donor (electron donor) is required to react with nitrate nitrogen. Common hydrogen donors include carbon sources (such as organic acids, sodium acetate, methanol) and hydrogen sulfide. In this invention, the abbreviation CS is used to represent carbon sources and hydrogen sulfide.

[0065] Beneficial effects of the present invention:

[0066] 1. It can minimize the concentration of pollutants in wastewater: The S1 solid-liquid separation unit in the method of the present invention can remove more than 90% of the suspended matter in the wastewater and separate it into a solid phase, including more than 1 / 3 of the COD in the water, which can greatly reduce the concentration of wastewater and the difficulty of treatment, and can ensure the normal operation of the three-phase separator in the subsequent unit.

[0067] Since the raw water from farm manure contains a large amount of undigested feed residues, solid-liquid separation is carried out before entering the sewage treatment system, and the resulting solids are composted and harmlessly treated. This can not only increase the solid recovery rate and the fertilizer effect of solid composting, but also reduce the release of protein and other components in the solids into the sewage, thereby reducing the COD concentration and ammonia nitrogen concentration in the sewage treatment system.

[0068] 2. It can improve the removal rate of COD: In the method of the present invention, the S201 process adopts pre-fermentation under acidic conditions, and uses acidophilic bacteria in the water to decompose the macromolecular pollutants in the raw water into small organic acid molecules, which can reduce the difficulty of decomposing macromolecular pollutants and improve the removal rate of COD in the water by subsequent biological units.

[0069] In the present invention, due to the effective solid-liquid separation in step S1, the concentration of suspended matter in the water is relatively low and can be reduced to below 500 mg / L, which can meet the requirements of 7.2.3 anaerobic biological treatment of influent water after solid-liquid separation in "Technical Specifications for Pollution Control Engineering in Livestock and Poultry Farming HJ497-2009", and 7.2.3.1 anaerobic reactor can be selected to adopt upflow anaerobic sludge blanket (UASB).

[0070] The S3 biogas-producing anaerobic unit of the present invention adopts an anaerobic reactor with a gas-liquid-solid three-phase separation function (such as EGSB, UASB, IC, ICX, etc.), which can increase the sludge concentration and reaction efficiency; the granular sludge is cultivated in the pool, the volume load is high, and the COD removal capacity is more than 3-5 times that of the flocculated sludge. In addition, the biogas produced by the S3 biogas-producing anaerobic unit can meet its own medium temperature (35-37°C) anaerobic conditions through combustion heat recovery. Its effluent contains a very small amount of suspended matter and a small amount of BOD, which ensures the smooth operation of the subsequent S4 anaerobic ammonia oxidation unit, can reduce the oxygen consumption of the aerobic unit, and reduce the processing cost. Because the red mud grows very slowly, a large amount of BOD and SS will affect the purity and denitrification effect of the red mud.

[0071] 3. It can create economic carbon source and hydrogen sulfide to remove total nitrogen: In step S201 of the present invention, the macromolecular pollutants in the raw water are converted into high-quality carbon source (organic acid) and hydrogen sulfide with a molecular weight less than 100 by using acid-producing dominant bacteria and sulfate-reducing bacteria; S202 transfers the carbon source and hydrogen sulfide to the air phase by acid adjustment and stripping; S203 uses clean water to elute the carbon source and hydrogen sulfide from the air phase to the clean water phase under the condition of pH=8-10 through the absorption tower, and adopts a circulating pump as the circulation and lifting power of the clean water. A neutralization tank is also set up to adjust the wastewater from which the carbon source and hydrogen sulfide are removed to a weak alkalinity to ensure the alkalinity requirements of the subsequent biological unit.

[0072] The present invention can create carbon source and hydrogen sulfide by itself without adding additional carbon source, which can greatly reduce the cost. In addition, the carbon source and hydrogen sulfide created are small molecular acids with a molecular weight of less than 100, which have good terminal deep denitrification effect, high microbial decomposition utilization rate, and no adverse effect on effluent COD; and can also reduce the content of hydrogen sulfide in biogas and reduce the difficulty of biogas desulfurization. In addition, the acid adjustment and elution process is carried out under acidic conditions. Since ammonia is not easy to volatilize in acidic solutions, the carbon source and hydrogen sulfide produced by the present invention will not be mixed with ammonia pollutants.

[0073] 4. Able to achieve low-cost denitrification

[0074] The method of the present invention adopts two processes of anaerobic ammonia oxidation process and short-range nitrification and denitrification process for denitrification, wherein the anaerobic ammonia oxidation process of step S4 is first used for denitrification. The temperature and suspended solids concentration of the normal operation of the anaerobic ammonia oxidation process for denitrification are relatively strict, but in this process, since the water produced by the biogas-producing anaerobic unit of step S3 can just meet the operating conditions of step S4, the process can remove about 85% of ammonia nitrogen. In the anaerobic ammonia oxidation process, only about 50% of the ammonia nitrogen needs to be oxidized, and the oxidation product is nitrite, which saves 62.5% of oxygen and more than half of the carbon source compared with conventional AO denitrification technology. This unit makes full use of the water temperature and waste heat of the effluent from the anaerobic unit, and there is no need to heat the sewage.

[0075] Then, the short-range nitrification and denitrification process in step S5 is used for further denitrification, and the aeration power is small; and the process can cultivate long-sludge autotrophic bacteria that oxidize ammonia into nitrite, and use the carbon source and hydrogen sulfide produced by S2 for denitrification. Ammonia nitrogen is oxidized into nitrite nitrogen, so compared with the traditional denitrification process, 1 / 4 of the aeration volume and 2 / 5 of the carbon source dosage can be saved; and the remaining 15% of total nitrogen can be removed.

[0076] 5. No chemical flocculants are added during the whole treatment process, and no chemical sludge is produced. A small amount of acid and alkali is consumed during the whole process, and the final product is dissolved in the wastewater to form a small amount of salt that is carried out with the effluent. In addition, the air used for stripping and the elution water of the absorption tower in the method of the present invention can be recycled, and no pollutants are discharged, which is green and environmentally friendly.

[0077] In summary, the present invention can achieve the standard discharge of COD and ammonia nitrogen in aquaculture wastewater with high efficiency and low cost, while reducing the use of chemical flocculants and reducing the risk of secondary pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0079] Figure 1 The figure is a schematic diagram of the process of treating fecal wastewater according to an embodiment of the present invention. DETAILED DESCRIPTION

[0080] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0081] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0082] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0083] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; "connection" can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0084] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0085] Example 1

[0086] This embodiment provides a feces wastewater treatment system, comprising:

[0087] The solid-liquid separation unit is used to remove suspended solids in the raw water; as a preferred embodiment, the solid-liquid separation unit adopts a laminated filter or a plate and frame filter press, and the filtration accuracy can be controlled within 0.05mm.

[0088] The CS production unit is mainly used to obtain carbon sources and hydrogen sulfide by using acid-producing dominant bacteria and sulfate-reducing bacteria, including an acid-producing anaerobic tank, an acid-adjusting air stripping tank, an absorption tower, and a neutralization tank;

[0089] The biogas-producing anaerobic unit is used to convert COD pollutants in water into biogas by anaerobic reaction, and the biogas is used to meet its own anaerobic temperature conditions; as a preferred embodiment, the biogas-producing anaerobic unit is an anaerobic reactor with gas-liquid-solid three-phase separation function, and granular sludge is cultivated in the pool; more preferably, the anaerobic reactor is an upflow anaerobic sludge blanket (UASB), EGSB, IC, ICX, etc.

[0090] The anaerobic ammonium oxidation unit is used to remove high-concentration total nitrogen in wastewater; as a preferred embodiment, the anaerobic ammonium oxidation unit is an aerated nitrite and denitrification split anaerobic ammonium oxidation unit, specifically an anaerobic ammonium oxidation combined pool, in which anaerobic ammonium oxidation red bacteria sludge of the order Planctomycetes is cultivated.

[0091] The short-cut nitrification and denitrification unit is used to further denitrify the effluent of the anaerobic ammonium oxidation unit using the aqueous solution containing carbon source and hydrogen sulfide eluted from the absorption tower of the CS production unit; as a preferred embodiment, the short-cut nitrification and denitrification unit is a short-cut nitrification and denitrification tank.

[0092] It also includes a clear water tank and a circulation pump, wherein the clear water tank is used to store the effluent of the short-range nitrification and denitrification unit, and the circulation pump is used to circulate the water in the clear water tank for use as elution water for the absorption tower;

[0093] The liquid outlet of the solid-liquid separation unit is connected to the water inlet of the acid-producing anaerobic tank, the water outlet of the acid-producing anaerobic tank is respectively connected to the water inlets of the acid-adjusting stripping tank and the biogas-producing anaerobic unit, the water outlet of the acid-adjusting stripping tank is connected to the neutralization tank, and its air outlet is connected to the gas inlet of the absorption tower, the gas outlet of the absorption tower is circularly connected to the air inlet of the acid-adjusting stripping tank, the water inlet of the absorption tower is connected to the clear water tank through a circulation pump, and the water outlet of the absorption tower is connected to the short-cut nitrification and denitrification unit; the biogas-producing anaerobic unit, the anaerobic ammonia oxidation unit, the short-cut nitrification and denitrification unit, and the clear water tank are connected in sequence.

[0094] Example 2

[0095] As attached Figure 1 As shown, this embodiment provides a method for treating feces and wastewater in a feces and wastewater treatment system of embodiment 1, which specifically includes the following steps:

[0096] S1. Solid-liquid separation: The fecal wastewater enters the solid-liquid separation unit, and the filtration accuracy of the solid-liquid separation unit is controlled within 0.05mm to remove suspended solids in the raw water. The filtered wastewater enters the next treatment unit; the generated solids are used for composting and harmless treatment.

[0097] In this method, the solid-liquid separation unit can remove more than 90% of the suspended matter in the wastewater and separate it into the solid phase, including more than 1 / 3 of the COD in the water, which can greatly reduce the concentration and treatment difficulty of the wastewater, and can ensure the normal operation of the three-phase separation in the subsequent units. Since the raw water of farm manure contains a large amount of undigested feed residues, solid-liquid separation is performed before entering the sewage treatment system, and the generated solids are composted and harmlessly treated, which can not only increase the solid recovery rate and the fertilizer effect of solid composting, but also reduce the release of components such as protein in the solids into the sewage, and reduce the COD concentration and ammonia nitrogen concentration of the sewage treatment system.

[0098] S2. Production of carbon source and hydrogen sulfide, specifically including:

[0099] S201, the sewage filtered in step S1 enters the acidogenic anaerobic tank, and the acidogenic dominant bacteria and sulfate-reducing bacteria SRB bacteria are added at 1-10ppm, and the acidogenic dominant bacteria are used to lyse the macromolecular pollutants in the sewage and convert them into small-molecule organic acid carbon sources, and sulfate-reducing bacteria are used to convert sulfur elements in the water into hydrogen sulfide; the converted carbon source and hydrogen sulfide are used as hydrogen donors required for subsequent denitrification reactions; as a preferred embodiment, the treatment conditions are: pH = 4.0-5.5, T = 10-35°C, HRT = 6-48 hours; the carbon source is a small-molecule organic acid, specifically an organic acid with a molecular weight of less than 100. The acidogenic dominant bacteria include: at least two of Bacillus formigenes, propionate-eating hydrogen-producing acetogenic bacteria, Clostridium butyricum, and butyrate-eating hydrogen-producing acetogenic bacteria. These acidogenic dominant bacteria are used to convert macromolecular organic matter in the water into small-molecule acids such as formic acid, acetic acid, propionic acid, and butyric acid.

[0100] The process of step S201 uses pre-fermentation under acidic conditions, and uses acidophilic bacteria in the water to decompose the macromolecular pollutants in the raw water into small organic acid molecules, which can reduce the difficulty of decomposing the macromolecular pollutants and improve the removal rate of COD in the water by subsequent biological units.

[0101] S202, a part of the sewage from the acid-generating anaerobic tank in step S201, specifically 5-25% of the sewage, enters the acid-adjusting and air-stripping tank, adjusts the pH to 1.0-4.0, and uses air to blow out the carbon source and hydrogen sulfide in this part of the sewage into the absorption tower under acidic conditions;

[0102] S203, the absorption tower uses clean water to wash out the carbon source and hydrogen sulfide in the air, and transfers the carbon source and hydrogen sulfide from the gas phase to the liquid phase to obtain an aqueous solution containing the carbon source and hydrogen sulfide; as a preferred embodiment, the treatment conditions are: pH = 8-10, HRT = 1-5 seconds; the eluted air is recycled and enters the acid stripping tank in step S202;

[0103] S204: After the carbon source and hydrogen sulfide are blown off in step S202, the wastewater enters the neutralization tank and is adjusted to a weak alkalinity to ensure the alkalinity requirements of the subsequent biological unit. The treatment conditions are: pH = 7-8, HRT = 1-5 minutes;

[0104] The present invention can create carbon source and hydrogen sulfide by itself through step S2, without adding additional carbon source, which can greatly reduce costs. The produced carbon source is a high-quality carbon source with a molecular weight of less than 100, mainly including formic acid, acetic acid, propionic acid, butyric acid, etc., with good denitrification effect, high microbial decomposition utilization rate, and no adverse effect on effluent COD; and it can also reduce the content of hydrogen sulfide in biogas and reduce the difficulty of biogas desulfurization. In addition, the acid adjustment and elution process is carried out under acidic conditions. Since ammonia is not easy to volatilize in acidic solutions, the carbon source and hydrogen sulfide produced by the present invention will not be mixed with ammonia pollutants.

[0105] S3. Removal of COD pollutants: The weak alkaline wastewater discharged from the neutralization tank in step S204 and the remaining 75-95% of the acid-producing wastewater discharged from the acid-producing anaerobic tank in step S201 enter the biogas-producing anaerobic unit, and are treated by anaerobic reaction to convert more than 75% of the COD pollutants in the wastewater into biomass energy biogas. The heat energy from the biogas combustion is used to provide energy for its own medium-temperature anaerobic conditions; the treatment conditions are: pH = 7-8.5, T = 35-40°C, HRT = 1-5 days, and the effluent SS < 1000mg / L;

[0106] In the present invention, due to the effective solid-liquid separation in step S1, the concentration of suspended matter in the water is relatively low and can be reduced to below 500 mg / L, which can meet the requirements of 7.2.3 anaerobic biological treatment of influent water after solid-liquid separation in "Technical Specifications for Pollution Control Engineering in Livestock and Poultry Farming HJ497-2009", and 7.2.3.1 anaerobic reactor can be selected to adopt upflow anaerobic sludge blanket (UASB).

[0107] The present invention preferably adopts an anaerobic reactor with a three-phase separation function in the biogas-producing anaerobic unit, which can increase the sludge concentration and reaction efficiency; the granular sludge is cultivated in the pool, the volume load is high, and the COD removal capacity is more than 3-5 times that of the flocculated sludge. In addition, the biogas produced by the S3 biogas-producing anaerobic unit can meet its own medium temperature (35-37°C) anaerobic conditions through combustion heat recovery. Its effluent contains very small amounts of suspended matter and a small amount of BOD, which ensures the smooth operation of the subsequent S4 anaerobic ammonia oxidation unit, can reduce the oxygen consumption of the aerobic unit, and reduce the processing cost.

[0108] S4, anaerobic ammonium oxidation denitrification: the sewage after the treatment in step S3 to remove COD pollutants enters the aerated nitrite and denitrification split anaerobic ammonium oxidation unit, and the chemoautotrophic bacteria anaerobic ammonium oxidizing bacteria are used to remove most of the total nitrogen. The remaining COD in the water is decomposed to provide the anaerobic ammonium oxidizing bacteria with carbon dioxide required for autotrophic synthesis; the treatment conditions are: pH = 7-8.5, T = 25-35 ° C, BOD < 1.5TN; under this treatment condition, part of the ammonia nitrogen is first converted into nitrite, and then the remaining ammonia and nitrite react to generate nitrogen gas to remove the total nitrogen;

[0109] S5. Short-cut nitrification and denitrification: The wastewater after denitrification in step S4 enters the short-cut nitrification and denitrification unit for further denitrification, and is introduced into the aqueous solution containing carbon source and hydrogen sulfide in step S203, and the denitrification process in the unit using carbon source and hydrogen sulfide as hydrogen donors further removes total nitrogen; as a preferred embodiment, the treatment conditions are: pH = 6.0-8.5, T = 20-35°C; the dissolved oxygen in the short-cut nitrification and denitrification unit is controlled within 1PPM, and the internal reflux ratio is greater than 10.

[0110] S6. The water treated in step S5 enters the clean water tank and provides clean water for elution to the absorption tower in step S203 through a circulation pump, and the remaining water is discharged or reused.

[0111] The method of the present invention adopts two processes, anaerobic ammonia oxidation process and short-range nitrification and denitrification process, to achieve low-cost denitrification. The anaerobic ammonia oxidation process of step S4 is first used for denitrification. The temperature and suspended solids concentration of the normal operation of the anaerobic ammonia oxidation process for denitrification are relatively strict. However, in this process, the water produced by the biogas-producing anaerobic unit of step S3 can just meet the operating conditions of step S4, and the remaining COD in the water is decomposed to provide the anaerobic ammonia-oxidizing bacteria with the carbon dioxide required for autotrophic synthesis, which can remove about 85% of ammonia nitrogen. In the anaerobic ammonia oxidation process, only about 50% of the ammonia nitrogen needs to be oxidized, and the oxidation product is nitrite, which saves 62.5% of oxygen and more than half of the carbon source compared with conventional AO denitrification technology. This unit makes full use of the water temperature and waste heat of the effluent from the anaerobic unit, and there is no need to heat the sewage twice.

[0112] Then, the short-range nitrification and denitrification process in step S5 is used for further denitrification, and the aeration power is small; and this process can cultivate long-sludge-age autotrophic bacteria that oxidize ammonia into nitrite, and use the carbon source and hydrogen sulfide produced in S2 for denitrification. Ammonia nitrogen is oxidized into nitrite nitrogen, so compared with the traditional denitrification process, 1 / 4 of the aeration volume and 2 / 5 of the carbon source dosage can be saved, and the remaining 15% of total nitrogen can be removed.

[0113] The whole treatment process of the present invention does not involve the addition of chemical flocculants, nor does it produce chemical sludge. A small amount of acid and alkali is consumed in the whole process, and the final product is dissolved in the wastewater to form a small amount of salt that is carried out with the effluent. In addition, the air used for stripping and the elution water of the absorption tower in the method of the present invention can be recycled, and no pollutants are discharged, which is green and environmentally friendly.

[0114] In summary, the present invention can achieve the standard discharge of COD and ammonia nitrogen in aquaculture wastewater with high efficiency and low cost, while reducing the use of chemical flocculants and reducing the risk of secondary pollution.

[0115] The above descriptions are only some preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for treating fecal wastewater, characterized in that: The steps include: S1. Solid-liquid separation: The fecal wastewater enters the solid-liquid separation unit to remove suspended solids in the raw water to reduce the COD and ammonia nitrogen concentrations and treatment difficulty of the wastewater. The filtered wastewater enters the next treatment unit; S2. Production of carbon source and hydrogen sulfide: S201, the sewage filtered in step S1 enters the acidogenic anaerobic tank, and the acidogenic dominant bacteria and sulfate-reducing bacteria are added at 1-10ppm, the acidogenic dominant bacteria are used to lyse the macromolecular pollutants in the sewage and convert them into small molecule organic acid carbon sources, and the sulfate-reducing bacteria are used to convert sulfur in the water into hydrogen sulfide; the small molecule organic acid carbon source is an organic acid with a molecular weight of less than 100; the treatment conditions are: pH = 4.0-5.5, T = 10-35°C, HRT = 6-48 hours; S202, a part of the wastewater from the acid-generating anaerobic tank in step S201 enters the acid-adjusting and air-stripping tank, and the pH is adjusted to 1.0-4.

0. Under weakly acidic conditions, the carbon source and hydrogen sulfide in this part of the wastewater are blown out by air into the absorption tower; S203, the absorption tower uses clean water to wash out the carbon source and hydrogen sulfide in the air, and transfers the carbon source and hydrogen sulfide from the gas phase to the liquid phase. The treatment conditions are: pH = 8-10, HRT = 1-5 seconds, and an aqueous solution containing the carbon source and hydrogen sulfide is obtained; the eluted air is recycled and enters the acid stripping tank in step S202; S204: After the carbon source and hydrogen sulfide are blown off in step S202, the wastewater enters the neutralization tank and is adjusted to weak alkalinity. The treatment conditions are: pH = 7-8, HRT = 1-5 minutes; S3. Removal of COD pollutants: The weak alkaline wastewater discharged from the neutralization tank in step S204 and the remaining acid-producing wastewater discharged from the acid-producing anaerobic tank in step S201 enter the biogas-producing anaerobic unit, and are treated by anaerobic reaction to convert more than 75% of the COD pollutants in the wastewater into biomass energy biogas, which provides energy for its own medium-temperature anaerobic conditions; the treatment conditions are: pH = 7-8.5, T = 35-40°C, HRT = 1-5 days, and effluent SS < 1000mg / L; In step S201, 5-25% of the wastewater from the acid-producing anaerobic tank enters the acid-adjusting air stripping tank to separate the carbon source and hydrogen sulfide; the remaining wastewater enters the biogas-producing anaerobic unit in step S3 and is mixed with the wastewater after the carbon source and hydrogen sulfide are separated for further treatment; S4, anaerobic ammonium oxidation denitrification: the sewage treated in step S3 enters the aerated nitrite and denitrification split anaerobic ammonium oxidation unit, and the chemoautotrophic bacteria anaerobic ammonium oxidizing bacteria are used to remove most of the total nitrogen. The remaining COD in the water is decomposed to provide the anaerobic ammonium oxidizing bacteria with carbon dioxide required for autotrophic synthesis; the treatment conditions are: pH = 7-8.5, T = 25-35 ° C, BOD < 1.5TN; under this treatment condition, part of the ammonia nitrogen is first converted into nitrite, and then the remaining ammonia and nitrite react to generate nitrogen gas to remove the total nitrogen; S5, short-cut nitrification and denitrification: the wastewater after denitrification in step S4 enters the short-cut nitrification and denitrification unit for further denitrification, and is introduced into the clear water solution containing carbon source and hydrogen sulfide in step S203, and the carbon source and hydrogen sulfide are used as hydrogen donors for the denitrification process in the unit to remove total nitrogen; the dissolved oxygen in the short-cut nitrification and denitrification unit is controlled within 1PPM, and the internal reflux ratio is greater than 10; the treatment conditions are: pH = 6.0-8.5, T = 20-35°C; S6. The water treated in step S5 enters the clean water tank and provides clean water for elution to the absorption tower in step S203 through a circulation pump, and the remaining water is discharged or reused.

2. The method for treating fecal wastewater according to claim 1, characterized in that: In step S1, the filtration accuracy of the solid-liquid separation unit is controlled within 0.05 mm to remove suspended solids in the raw water, and the generated solids are used for composting and harmless treatment.

3. The method for treating fecal wastewater according to claim 1 or 2, characterized in that: The small molecule organic acid carbon source includes formic acid, acetic acid, propionic acid and butyric acid.

4. A feces and wastewater treatment system capable of implementing the feces and wastewater treatment method according to any one of claims 1 to 3, characterized in that: include: Solid-liquid separation unit, used to remove suspended solids in raw water; The CS production unit is mainly used to obtain carbon sources and hydrogen sulfide by using acid-producing dominant bacteria and sulfate-reducing bacteria, including an acid-producing anaerobic tank, an acid-adjusting air stripping tank, an absorption tower, and a neutralization tank; The biogas-producing anaerobic unit is used to convert COD pollutants in water into biogas by anaerobic reaction, and the heat energy of the biogas combustion is used to meet the anaerobic temperature conditions of the unit; Anaerobic ammonium oxidation unit, used to remove high concentrations of total nitrogen from wastewater; Short-cut nitrification and denitrification unit, used to further denitrify the effluent from the anaerobic ammonium oxidation unit; It also includes a clear water tank and a circulation pump, wherein the clear water tank is used to store the effluent of the short-range nitrification and denitrification unit, and the circulation pump is used to circulate the water in the clear water tank for use as elution water for the absorption tower; The liquid outlet of the solid-liquid separation unit is connected to the water inlet of the acid-producing anaerobic tank, the water outlet of the acid-producing anaerobic tank is respectively connected to the water inlets of the acid-adjusting stripping tank and the biogas-producing anaerobic unit, the water outlet of the acid-adjusting stripping tank is connected to the neutralization tank, the air outlet thereof is connected to the gas inlet of the absorption tower, the gas outlet of the absorption tower is cyclically connected to the air inlet of the acid-adjusting stripping tank, the water inlet of the absorption tower is connected to the clear water tank through a circulation pump, and the water outlet of the absorption tower is connected to the short-range nitrification and denitrification unit; The biogas-producing anaerobic unit, the anaerobic ammonium oxidation unit, the short-range nitrification and denitrification unit, and the clear water tank are connected in sequence.

5. The feces and wastewater treatment system according to claim 4, characterized in that: The solid-liquid separation unit is a laminated filter or a plate and frame filter press.

6. The feces and wastewater treatment system according to claim 4, characterized in that: The biogas-producing anaerobic unit is an anaerobic reactor with a gas-liquid-solid three-phase separation function, in which granular sludge is cultivated; The anaerobic ammonium oxidation unit is an aerated nitrite and denitrification split type anaerobic ammonium oxidation unit, specifically an anaerobic ammonium oxidation combined pool, in which anaerobic ammonium oxidation red bacteria sludge of the order Planctomycetes is cultivated; The short-cut nitrification and denitrification unit is a short-cut nitrification and denitrification tank.

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