High-cod livestock and poultry breeding wastewater treatment process

Abstract

The application discloses a high-COD livestock and poultry breeding wastewater treatment process, which comprises the following processes: a pretreatment process, which realizes preliminary treatment of wastewater by preliminarily filtering and solid-liquid separating the wastewater of a cattle farm, so that solid waste in the wastewater is discharged; and a deep biochemical treatment process, which realizes effective degradation of COD by treating the wastewater through a biochemical tank, an oxidation tank and a sedimentation tank, and further degrades COD and SS through a fixed bed. The high-COD livestock and poultry breeding wastewater treatment process adopts anaerobic treatment, and since the COD concentration of breeding wastewater is extremely high, 80%-90% of organic matter COD can be degraded in a biogas treatment unit after anaerobic treatment of high-concentration COD wastewater, so that the organic load of a subsequent treatment system is greatly reduced, and the process has the advantages that organic matter can be effectively degraded and biogas can be produced to obtain benefits. In addition, the anaerobically treated water is deeply oxidized by micro-nano ozone bubbles, so that the refractory organic matter is converted into small-molecule organic matter and part of the COD is removed, and the difficulty of the subsequent treatment system is reduced.

Description

Technical Field

[0001] This invention relates to the field of environmental engineering technology, specifically to a high-COD livestock and poultry breeding wastewater treatment process. Background Technology

[0002] Cattle farm wastewater contains a significant amount of nutrients such as nitrogen, phosphorus, and potassium. If applied properly, these nutrients can effectively improve soil fertility, enhance soil physical and chemical properties, and promote crop growth. However, direct, continuous, and excessive application without any treatment can negatively impact soil and crop growth, causing excessive vegetative growth, lodging, and significantly reducing yield. It can also delay maturity and affect subsequent crop production. The large accumulation of organic matter in the wastewater in the soil, while providing nutrients and a suitable environment for small animals, insects, fungi, and bacteria, can also lead to the proliferation of pathogens and pests. Furthermore, the accumulation of large amounts of organic matter makes the soil highly reducing. Highly reducing conditions not only affect crop root growth but also easily release harmful elements that were previously inert in the soil. The accumulation of large amounts of inorganic salts in the soil can cause salt damage to crops. Therefore, livestock and poultry farm wastewater must be treated before discharge. However, livestock wastewater is characterized by high levels of four pollutants: high COD, high NH3-N, high TP, and high SS. Its concentration is 50 to 100 times that of domestic sewage, making it extremely difficult to treat. Furthermore, livestock wastewater usually carries a large amount of feces, which greatly increases the difficulty of wastewater treatment. Therefore, livestock wastewater must be pretreated. However, even after pretreatment, the concentration of pollutants in the wastewater is still relatively high, far from meeting the standards. In addition, livestock wastewater from cattle farms contains a large amount of non-degradable cellulose, humic acid, and other substances, which greatly increases the difficulty of biological treatment, making the treatment of livestock wastewater difficult.

[0003] The addition of nZVI in the anaerobic reactor, the use of micro-nano ozone bubble oxidation, and the addition of sodium acetate in the aerobic reactor to enhance the biochemical treatment effect achieves efficient COD removal. Summary of the Invention

[0004] The purpose of this invention is to provide a high COD livestock and poultry breeding wastewater treatment process to solve the problem of difficult wastewater treatment in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a high-COD livestock and poultry breeding wastewater treatment process, comprising the following steps: The pretreatment process involves preliminary filtration and solid-liquid separation of the wastewater from the cattle farm to achieve initial treatment of the wastewater, thereby allowing the solid waste in the wastewater to be discharged. The advanced biological treatment process treats wastewater through biological treatment tanks, oxidation tanks, and sedimentation tanks, enabling effective degradation of COD. At the same time, a fixed bed further degrades COD and SS.

[0006] Preferably, the preprocessing procedure includes the following steps: S1. Wastewater from the cattle farm enters the sedimentation tank after passing through the screen, where large pieces of floating debris and clumps of manure are removed. S2. Wastewater is filtered through a screen of a solid-liquid separator. The filtered sludge and waste material from the bar filter are mechanically dewatered and then composted. S3. Wastewater flows from bottom to top through the primary anaerobic reactor.

[0007] S4. The effluent from the primary anaerobic reactor enters the secondary anaerobic reactor; S5. The effluent from the secondary anaerobic reactor enters the oxidation tank. S6. The effluent from the secondary anaerobic reactor enters the primary oxidation tank; S7. The effluent from the primary oxidation tank is allowed to stand for 1 day before entering the aerobic reactor; S8. The effluent from the aerobic reactor enters the sedimentation tank. The sludge in the sedimentation tank is returned to the aerobic reactor. Excess sludge is discharged to the sludge thickening tank. The sludge in the sludge thickening tank is mechanically dewatered and then composted into sludge cakes. S9. Check whether the COD of the sedimentation tank effluent meets the standard; S10. Substandard effluent from the sedimentation tank enters the secondary oxidation tank; S11. The effluent from the secondary oxidation tank and the effluent from the sedimentation tank that meet the standards enter the fixed bed for further treatment and removal of suspended solids. S12. Water from the fixed bed enters the disinfection tank.

[0008] Preferably, the bottom of the primary anaerobic reactor is provided with a high-concentration and highly active granular sludge layer, and the upper part of the anaerobic reactor is provided with a three-phase separator.

[0009] Preferably, the bottom of the secondary anaerobic reactor is provided with a high-concentration and highly active granular sludge layer and 2 g / L of nZVI with a particle size of 100 nm is added, and a three-phase separator is provided at the top of the anaerobic reactor.

[0010] Preferably, the primary oxidation tank is equipped with an ozone generator and a nanobubble generator to produce 100 nm-10 m-nanometer ozone bubbles.

[0011] Preferably, the aerobic reactor is an SBR reactor, and sodium acetate is added to the influent to make the C / N ratio 5.

[0012] Preferably, the sedimentation tank adopts a vertical flow sedimentation method, and a sludge pump is installed inside the sedimentation tank.

[0013] Preferably, the secondary oxidation tank is equipped with an ozone generator and a nanobubble generator to produce 100 nm-10 m-nanometer ozone bubbles.

[0014] Preferably, the fixed bed is filled with powdered activated carbon.

[0015] Compared with the prior art, the beneficial effects of the present invention are: the high COD livestock and poultry breeding wastewater treatment process: 1. Compared to traditional anaerobic reactors, this scheme incorporates nZVI into the reactor. The significance of adding nZVI lies in the fact that extracellular electron transfer (IET) is a core metabolic pathway for microorganisms, and regulating its rate can affect pollutant degradation and methane generation. In anaerobic systems, interspecies electron transfer is a key mechanism of microbial symbiotic metabolism, especially helping acid-producing bacteria and archaea overcome thermodynamic limitations. Currently, IET mainly includes two forms: mediated electron transfer (IET) and direct interspecies electron transfer (DIET). The proposed DIET mechanism reveals that microorganisms do not need to rely on hydrogen or formic acid transfer but can achieve energy cooperation through direct electron exchange, thereby improving metabolic efficiency and reducing energy loss.

[0016] Further research indicates that conductive materials are crucial mediators for enhancing DIET. Iron-based materials have attracted widespread attention due to their environmental friendliness, excellent conductivity, and surface activity, and can serve as electron bridges to accelerate electron exchange between microorganisms. Among them, nano-zero-valent iron stands out due to its nanoscale size, high specific surface area, and unique core. The shell structure exhibits excellent reactivity: the iron core acts as an electron source and plays a reducing role, while the surface oxide promotes adsorption and surface complexation, and allows electron tunneling transport, thereby effectively promoting energy conversion and resource recovery during anaerobic digestion.

[0017] The results showed that the COD removal rate increased from 78.18% to 84.45% after adding nZVI, achieving efficient COD removal.

[0018] 2. Compared to traditional advanced oxidation methods, this solution employs micro-nano ozone bubble oxidation, which not only avoids secondary pollution similar to iron sludge but also effectively oxidizes recalcitrant high-molecular-weight organic compounds into smaller organic molecules. The significance of micro-nano ozone bubble oxidation lies in the fact that while ozone's powerful oxidizing ability and lack of secondary pollution make it widely used in the degradation of various difficult-to-treat wastewaters, its instability and easy decomposition in water result in poor pollutant degradation and high energy consumption. MNBs (micro-nano bubbles) can improve mass transfer efficiency and promote the formation of ·OH. Therefore, combining ozone and MNBs processes results in the ozone micro-nano bubble process (O3-MNBs), which improves ozone mass transfer capacity, increases ozone utilization efficiency, and enhances the degradation effect of the ozone process through MNBs. Attached Figure Description

[0019] Figure 1 Schematic diagram of the entire processing flow of this invention Figure 2 Graph showing COD removal efficiency in an anaerobic reactor Figure 3 COD removal effect diagram in primary oxidation tank Figure 4 Full-process COD removal effect diagram Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Please refer to Figure 1. This invention provides a technical solution: a high-COD livestock and poultry breeding wastewater treatment process, comprising the following steps: The pretreatment process involves preliminary filtration and solid-liquid separation of the wastewater from the cattle farm to achieve initial treatment of the wastewater, thereby allowing the solid waste in the wastewater to be discharged. The advanced biological treatment process treats wastewater through biological treatment tanks, oxidation tanks, and sedimentation tanks, enabling effective degradation of COD. At the same time, a fixed bed further degrades COD and SS.

[0022] In the pretreatment process, the wastewater from the cattle farm enters the sedimentation tank after passing through the screen. This tank is mainly used to collect the sewage from the cattle farm, and plays a role in concentrating, regulating, and homogenizing the quality and quantity. After being stirred evenly, the wastewater is lifted to the solid-liquid separator. The wastewater is filtered through the screen of the solid-liquid separator, and most of the manure in the wastewater is intercepted in the inclined screen. The manure residue is then squeezed out by the screw pump, realizing the separation of manure and water. The separated manure is transported off-site or composted.

[0023] The anaerobic reactor is a double-layered cylinder with a height of 830 mm and a diameter of 140 mm, and an effective volume of 10.0 L. An inlet (50 mm from the bottom) and an outlet (120 mm from the top) are vertically positioned on the reactor wall. A water bath heating device is provided to ensure a constant temperature environment. The sludge inoculated into the reactor is from the Taobao seller "Little Sea Cow" anaerobic granular sludge, with a particle diameter of 0.3~3 mm, a VSS / TSS ≥ 0.75, and an effective particle size ≥ 80%.

[0024] In the advanced biological treatment process, the pretreated wastewater flows from bottom to top through a primary anaerobic reactor. Passing through a high-concentration, highly active granular sludge layer at the bottom of the reactor, most of the organic matter is converted into CH4 and CO2. The agitation of the gaseous products and the adhesion of bubbles to the sludge form a suspended sludge layer. A three-phase separator is installed at the top of the reactor to separate the gas, liquid, and solid phases. The separated gas is discharged from the top, while the separated sludge automatically slides down to the suspended sludge layer. The effluent flows out from the overflow weir. Due to the reactor's excellent water distribution, mixing, water flow agitation, three-phase separation, and sludge discharge systems, the reactor has advantages such as high load capacity, high organic matter degradation efficiency, short residence time, and high gas production efficiency.

[0025] The effluent from the primary anaerobic reactor is pumped from bottom to top into the secondary anaerobic reactor. Passing through the high-concentration, highly active granular sludge layer at the bottom of the reactor, the portion of BOD and recalcitrant COD that could not be removed by the primary anaerobic reactor at this stage is further converted into CH4 and CO2 with the assistance of nZVI. The agitation of the gaseous products and the adhesion of bubbles to the sludge form a sludge suspension layer. A three-phase separator is installed at the top of the reactor to separate the gas, liquid, and solid phases. The separated gas is discharged from the top, while the separated sludge automatically slides down to the suspended sludge layer, and the effluent flows out from the overflow weir.

[0026] The effluent from the secondary anaerobic reactor enters the primary oxidation tank, which is equipped with a nanobubble generator. This device uses a built-in water pump to transport wastewater to the generator, and injects ozone generated by a connected ozone generator into the wastewater at a pressure of 0.4 MPa. Subsequently, the wastewater is released through specific nozzles, where, under the combined action of high-speed shearing and high-frequency pressure changes, micron and nano-sized bubbles are formed, thereby generating a strong oxidizing effect and achieving the degradation and transformation of organic pollutants (COD) in the wastewater.

[0027] After the effluent from the primary oxidation tank is allowed to stand for 1 day to remove residual ozone, it enters the aerobic reactor. Before that, the pH is adjusted to neutral and the C / N ratio is adjusted to 5 using glacial acetic acid (AR ≥ 99.5%) and sodium hydroxide solution (1 mol / L).

[0028] The aerobic biological treatment experiment was conducted in a 5 L effective volume SBR reactor made of plexiglass with a microporous aeration disc at the bottom. During the experiment, the pH of the SBR reactor was controlled at 7.0–8.0, dissolved oxygen (DO) at 2.0–4.0 mg / L, and the temperature at room temperature (in winter, the laboratory temperature was controlled at around 25 ℃ using air conditioning). One operating cycle of the SBR reactor was 24 h, with 22 h of aeration and approximately 2 h of settling. Sampling, water exchange, sludge removal, and chemical dosing times were very short and negligible. The inoculum sludge for the SBR reactor was taken from the activated sludge of the aerobic tank of a wastewater treatment plant in Nanjing. It appeared as yellowish-brown flocculent sludge with an initial MLSS concentration of approximately (3000±20) mg / L and an average particle size of 57.65 μm.

[0029] To achieve targeted acclimatization of the inoculated sludge, the initial influent was prepared by diluting raw water (after oxidation) at a volume ratio of 10:90. Subsequently, the system followed a predetermined acclimatization procedure: every 5 (3) days, the proportion of raw water (after oxidation) was increased by 10%. This gradual replacement strategy aimed to smoothly guide the microbial community to adapt to the physicochemical properties of the target substrate, ultimately enabling it to maintain excellent metabolic activity and system stability even when raw water (after oxidation) was used as the sole influent.

[0030] When the COD of the effluent from the sedimentation tank fails to meet the standard, the effluent enters the secondary oxidation tank for deep degradation of organic pollutants. The reaction mechanism of the secondary oxidation tank is the same as that of the primary oxidation tank.

[0031] After degradation in the secondary oxidation tank and the treated effluent from the sedimentation tank, the effluent enters a fixed bed for activated carbon adsorption and suspended solids removal. 10.0 mL (wet volume) of cleaned activated carbon is added to a custom-made quartz glass adsorption column (10.0 mm in diameter, 130.0 mm in length), and air bubbles are removed from the bed. The treated livestock and poultry wastewater is used as the loading solution for the adsorption column, and is passed through the column at a constant flow rate (5 BV / h) using a variable-speed peristaltic pump. The empty bed contact time (EBCT) is 12 min. An automatic fraction collector is used to periodically collect effluent samples from the adsorption column, and the COD and SS concentrations in the treated effluent are tested.

[0032] Table 1: Treatment Results

[0033] As shown in Table 1: The solid-liquid separation equipment separates solids, liquids, and gases, separating insoluble impurities and gaseous pollutants from wastewater. This process mainly removes solid impurities and gaseous pollutants, but has no effect on removing pollutants dissolved in wastewater. After wastewater treatment in the anaerobic reactor, the effluent COD decreased to 2000-2500 mg / L, corresponding to a COD removal rate of 77.3%-81.8%. This indicates that the anaerobic microbial community within the UASB reactor achieved efficient conversion of biodegradable components in the wastewater. The brown appearance of the effluent indicates that the wastewater still contains lignin and its derivatives, as well as humic substances, which are difficult to biodegrade anaerobically and constitute the main part of the remaining COD. Simultaneously, the pH value increased from 6.5-7.7 in the influent to 7.0-8.0, and the odor significantly decreased. This phenomenon confirms that volatile fatty acids and other acidic intermediates in the system were effectively converted into methane and carbon dioxide, while sulfur-containing organic matter was also reduced and removed. After adding nZVI, the effluent COD decreased to approximately 1600 mg / L, representing an approximately 6% increase in COD removal rate compared to the effluent without nZVI, demonstrating the enhancing effect of nZVI on the anaerobic treatment process. Furthermore, SS decreased by 93.6% during this process. During the micro-nano ozone bubble oxidation process, a significant gradient change in water color was observed: from an initial brown to a yellow color, eventually achieving a colorless and transparent state. Simultaneously, the COD concentration decreased to 800-1000 mg / L, with a removal rate of 54.5%-63.6%. When nZVI was added to the anaerobic reactor, the effluent concentration was approximately 1600 mg / L. After micro-nano ozone bubble oxidation, the COD concentration decreased to 500-700 mg / L, with a removal rate of 62.5%. After wastewater treatment in the aerobic reactor, the effluent COD decreased to 600 mg / L, corresponding to a COD removal rate of 33.3%. This indicates that the aerobic microbial community within the SBR reactor achieved efficient conversion of biodegradable components in the wastewater. After adding nZVI, the effluent COD decreased to approximately 400 mg / L, but the SS slightly increased during this process, primarily due to suspended microbial flocs. During the secondary micro-nano ozone bubble oxidation process, the COD concentration decreased to 400 mg / L, and the removal rate reached 33.3% (the COD of the nZVI group decreased to 200 mg / L, and the removal rate was 50%). After final treatment with activated carbon, the COD concentration of the wastewater decreased from 400 mg / L in the influent to 330 mg / L, achieving a removal rate of 17.5% (the COD in the group with added nZVI decreased to 180 mg / L, with a removal rate of 10%). This data confirms that activated carbon has a certain adsorption and removal capacity for recalcitrant COD components, indicating that it can serve as an effective physicochemical enhancement method in advanced treatment, and further reduced the SS concentration to 10 mg / L.

Claims

1. A high-COD livestock and poultry breeding wastewater treatment process, characterized in that: The process includes the following steps: The pretreatment process involves preliminary filtration and solid-liquid separation of the wastewater from the cattle farm to achieve initial treatment of the wastewater, thereby allowing the solid waste in the wastewater to be discharged. The advanced biological treatment process treats wastewater through biological treatment tanks, oxidation tanks, and sedimentation tanks, enabling effective degradation of COD. At the same time, a fixed bed further degrades COD and SS.

2. The high COD livestock and poultry breeding wastewater treatment process according to claim 1, characterized in that: The preprocessing procedure includes the following steps: S1. Wastewater from the cattle farm enters the sedimentation tank after passing through the screen, where large pieces of floating debris and clumps of manure are removed. S2. Wastewater is filtered through a screen of a solid-liquid separator. The filtered sludge and waste material from the bar filter are mechanically dewatered and then composted. S3. Wastewater flows from bottom to top through the primary anaerobic reactor.

3. The high-COD livestock and poultry breeding wastewater treatment process according to claim 1, characterized in that: The deep biochemical treatment process includes the following steps: S1. The effluent from the primary anaerobic reactor enters the secondary anaerobic reactor; S2. The effluent from the secondary anaerobic reactor enters the oxidation tank; S3. The effluent from the secondary anaerobic reactor enters the primary oxidation tank; S4. The effluent from the primary oxidation tank is allowed to stand for 1 day before entering the aerobic reactor; S5. The effluent from the aerobic reactor enters the sedimentation tank. The sludge in the sedimentation tank is returned to the aerobic reactor. Excess sludge is discharged to the sludge thickening tank. The sludge in the sludge thickening tank is mechanically dewatered and then composted into sludge cakes. S6. Check whether the COD of the sedimentation tank effluent meets the standard; S7. Substandard effluent from the sedimentation tank enters the secondary oxidation tank; S8. The effluent from the secondary oxidation tank and the effluent from the sedimentation tank that meet the standards enter the fixed bed for further treatment and removal of suspended solids. S9. Water from the fixed bed enters the disinfection tank.

4. The high-COD livestock and poultry breeding wastewater treatment process according to claim 2, characterized in that: The bottom of the primary anaerobic reactor is equipped with a high-concentration and highly active granular sludge layer, and the upper part of the anaerobic reactor is equipped with a three-phase separator.

5. The high-COD livestock and poultry breeding wastewater treatment process according to claim 3, characterized in that: The bottom of the secondary anaerobic reactor is equipped with a high-concentration and highly active granular sludge layer and 2 g / L of 100 nm nano iron powder nZVI is added. A three-phase separator is installed at the top of the anaerobic reactor.

6. The high-COD livestock and poultry breeding wastewater treatment process according to claim 3, characterized in that: The primary oxidation tank is equipped with an ozone generator and a nanobubble generator to produce 100nm-10 m-nanometer ozone bubbles.

7. The high-COD livestock and poultry breeding wastewater treatment process according to claim 3, characterized in that: The aerobic reactor is an SBR reactor, and sodium acetate is added to the influent to make the C / N ratio 5.

8. The high-COD livestock and poultry breeding wastewater treatment process according to claim 3, characterized in that: The sedimentation tank adopts a vertical flow sedimentation method, and a sludge pump is installed inside the sedimentation tank.

9. The high-COD livestock and poultry breeding wastewater treatment process according to claim 3, characterized in that: The secondary oxidation tank is equipped with an ozone generator and a nanobubble generator to produce 100 nm-10 m-nano ozone bubbles.

10. The high-COD livestock and poultry breeding wastewater treatment process according to claim 3, characterized in that: The fixed bed is filled with powdered activated carbon.

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