Sewage treatment process

Abstract

The invention discloses a sewage treatment process, and relates to the technical field of wastewater treatment. The process comprises the following steps: collecting and homogenizing enterprise wastewater through a new water collecting tank and a homogenizing tank; physicochemical pretreatment is performed through a primary flocculation tank and a primary sedimentation tank; after being buffered by the intermediate water tank, the wastewater enters an efficient hydrolysis acidification tower to improve the biodegradability of the wastewater; then carrying out biodegradation through a first-stage aerobic tank, a second-stage aerobic tank and a contact oxidation tank in sequence; and finally, carrying out deep treatment through a secondary flocculation tank and a final sedimentation tank. According to the invention, a multi-stage physicochemical-biological combined process is adopted, and process parameters and unit configuration are optimized, so that efficient and stable treatment of complex wastewater in the industrial park is realized, the effluent quality is stable and reaches the first-grade A standard, and the impact resistance is relatively high. In addition, the invention also comprises a perfect sludge treatment system and an emergency treatment mechanism, so that the reliability and the safety of system operation are ensured.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a comprehensive treatment process for wastewater from enterprises in industrial parks, and more particularly to a wastewater treatment process that combines physicochemical treatment, biological treatment, and advanced treatment. Background Technology

[0002] With rapid industrial development, the discharge of industrial wastewater is increasing daily, causing serious pollution to the water environment. Traditional wastewater treatment processes mostly employ single biological or physicochemical treatment methods, which have limited effectiveness in treating wastewater from complex industrial parks, especially for recalcitrant organic matter and high-concentration wastewater. Existing technologies for general industrial wastewater treatment generally suffer from the following problems:

[0003] For industrial wastewater with complex composition and large fluctuations in pollutant concentration, conventional treatment processes are difficult to consistently meet emission standards.

[0004] Traditional biological treatment systems have low efficiency in removing recalcitrant organic matter and are susceptible to system collapse due to shock loads.

[0005] A single treatment unit cannot effectively remove multiple pollutants such as COD, BOD, SS, ammonia nitrogen, and total phosphorus simultaneously;

[0006] Inadequate sludge treatment and disposal can easily cause secondary pollution;

[0007] The lack of an effective emergency response mechanism means that the quality of the effluent cannot be guaranteed when faced with sudden water quality abnormalities or equipment failures.

[0008] For example, Chinese patent CN105293665A discloses an industrial wastewater treatment system. Although it adopts a process route of "pretreatment + biochemical treatment + deep treatment", it fails to solve the problem of efficient removal of high-concentration recalcitrant organic matter. Chinese patent CN107935273A discloses a sewage treatment process. Although it improves the biological treatment unit, it is not adaptable to industrial wastewater with large fluctuations in water quality and lacks a sound emergency treatment mechanism.

[0009] Therefore, there is an urgent need to develop a wastewater treatment process that can stably treat industrial wastewater with complex composition, and has high treatment efficiency and shock resistance. Summary of the Invention

[0010] The purpose of this invention is to provide a wastewater treatment process to solve the problems of low efficiency, poor stability and weak shock resistance in the treatment of industrial wastewater in the prior art, so as to achieve efficient and stable treatment of wastewater from enterprises in industrial parks and ensure that the effluent quality meets the discharge standards.

[0011] To achieve the above objectives, the present invention provides a wastewater treatment process, comprising the following steps:

[0012] S1: Collect the enterprise's wastewater into a new collection tank, and then transport it to a homogenization and equalization tank using a submersible pump;

[0013] S2: In the homogenization and equalization tank, the wastewater is uniformly mixed and the water volume is adjusted using a submersible mixer;

[0014] S3: The homogenized and equalized wastewater is introduced into the primary flocculation tank, and flocculant is added to cause the suspended solids in the wastewater to form complexes.

[0015] S4: The wastewater after primary flocculation is introduced into a radial flow primary sedimentation tank for solid-liquid separation;

[0016] S5: The effluent from the primary sedimentation tank is introduced into the intermediate water tank for buffering;

[0017] S6: The effluent from the intermediate water tank is introduced into the high-efficiency hydrolysis acidification tower to convert the recalcitrant organic matter into readily biodegradable organic matter;

[0018] S7: The hydrolyzed and acidified wastewater is sequentially introduced into the primary aerobic tank and the secondary aerobic tank, and aeration is carried out by blower, utilizing microorganisms to digest and degrade the organic matter in the wastewater;

[0019] S8: The effluent from the secondary aerobic tank is introduced into the secondary sedimentation tank for mud-water separation;

[0020] S9: The effluent from the secondary sedimentation tank is introduced into the contact oxidation tank, and the organic matter is further degraded by blower aeration.

[0021] S10: The effluent from the contact oxidation tank is introduced into the secondary flocculation tank, and flocculants are added to cause COD and SS to react.

[0022] S11: The wastewater after secondary flocculation is introduced into the final sedimentation tank, where COD and SS are reduced through adsorption and sedimentation.

[0023] S12: Detect the water quality of the effluent from the final sedimentation tank. If it meets the standards, it will be discharged; otherwise, it will be returned to the treatment system.

[0024] Furthermore, the flocculants added in steps S3 and S10 are PAC and PAM, wherein the dosage of PAC is 20-50 mg / L and the dosage of PAM is 0.5-2 mg / L.

[0025] Furthermore, in step S6, the hydraulic residence time of the high-efficiency hydrolysis acidification tower is 8-12 hours, the temperature is controlled at 30-35℃, and the pH value is controlled at 6.0-7.5.

[0026] Furthermore, in step S7, the dissolved oxygen concentrations in the primary aerobic tank and the secondary aerobic tank are controlled at 2-3 mg / L and 2-4 mg / L, respectively, and the sludge concentrations are controlled at 3000-4000 mg / L and 2500-3500 mg / L, respectively.

[0027] Furthermore, the present invention also includes a sludge treatment system, which collects the sludge generated from the primary sedimentation tank, secondary sedimentation tank and final sedimentation tank into a physicochemical sludge tank and a biological sludge tank, respectively, and then performs sludge dewatering and drying treatment, and finally entrusts a professional organization to dispose of it.

[0028] Furthermore, the present invention also includes a sludge return step, in which part of the sludge from the secondary sedimentation tank is returned to the primary aerobic tank, with the return ratio controlled at 50%-100%.

[0029] Furthermore, the present invention also includes an ozone treatment step, wherein an ozone buffer tank and an ozone reaction tank are added after the contact oxidation tank to use ozone for deep oxidation treatment of wastewater.

[0030] Furthermore, the present invention also includes an emergency treatment system that, when water quality is abnormal or equipment malfunctions, directs wastewater into an emergency pool for temporary storage until the system returns to normal before further treatment.

[0031] The wastewater treatment process of the present invention has the following beneficial effects:

[0032] (1) The design of the homogenization and equalization tank effectively buffers the fluctuations in the quality and quantity of enterprise wastewater, and improves the stability and treatment efficiency of subsequent treatment units.

[0033] (2) The physical and chemical pretreatment process of “one-time flocculation + primary sedimentation” effectively removes most of the suspended solids and macromolecular organic matter in the wastewater, reduces the load on the subsequent biological treatment system, and improves the biodegradability of the wastewater.

[0034] (3) The design of the high-efficiency hydrolysis acidification tower is specifically designed for the recalcitrant organic matter in industrial park wastewater. Through hydrolysis and acidification, it transforms the recalcitrant organic matter into easily degradable low-molecular-weight organic matter, which greatly improves the biodegradability of the wastewater.

[0035] (4) The three-stage biological treatment process of “primary aerobic + secondary aerobic + contact oxidation” is adopted to gradually reduce the concentration of pollutants, avoid excessive load on a single biological treatment unit, and improve the stability and shock resistance of the system.

[0036] (5) Through the deep treatment process of "secondary flocculation + final sedimentation", residual pollutants that are difficult to degrade by biological treatment are effectively removed, ensuring that the effluent quality consistently meets the discharge standards.

[0037] (6) A complete sludge treatment system has been established, which has achieved the reduction, stabilization and harmless treatment of sludge, and avoided secondary pollution;

[0038] (7) An emergency treatment system was designed. When the water quality is abnormal or the equipment fails, it can be switched to the emergency treatment mode in a timely manner to ensure the reliability of the system operation and the safety of the effluent water quality.

[0039] (8) By optimizing process parameters (such as the hydraulic retention time of the hydrolysis acidification tower, the dissolved oxygen concentration of the aerobic tank, and the sludge return ratio), the treatment efficiency has been significantly improved and the operating energy consumption has been reduced. Attached Figure Description

[0040] Figure 1 This is a process flow diagram of the wastewater treatment process of the present invention. Detailed Implementation

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The following embodiments are explanations of the present invention, but the present invention is not limited to the following embodiments.

[0042] System composition:

[0043] The wastewater treatment system of this invention includes a new collection tank, a homogenization and equalization tank, a primary flocculation tank, a primary sedimentation tank, an intermediate tank, a high-efficiency hydrolysis acidification tower, a primary aerobic tank, a secondary aerobic tank, a secondary sedimentation tank, a contact oxidation tank, a secondary flocculation tank, a final sedimentation tank, an ozone buffer tank, an ozone reaction tank, a physicochemical sludge tank, a biological sludge tank, and related auxiliary facilities. All treatment units are connected by pipelines to form a complete wastewater treatment process line.

[0044] Process flow:

[0045] S1: The company's wastewater first enters the new collection tank, and is then transported to the subsequent equalization and equalization tank by a submersible pump installed at the bottom of the tank. The new collection tank is designed with a volume of 200m³, which can meet the wastewater collection needs for 2-4 hours.

[0046] S2: In the homogenization and equalization tank, the incoming water is uniformly mixed using submersible mixers, and the inflow rate to subsequent treatment units is adjusted. The homogenization and equalization tank has a designed volume of 500 m³, a hydraulic retention time of 4–6 hours, and is equipped with two submersible mixers, each with a power of 3 kW and a rotation speed of 1450 rpm.

[0047] S3: After homogenization and equalization, the wastewater flows into the primary flocculation tank. PAC (polyaluminum chloride) and PAM (polyacrylamide) are added through metering pumps, causing suspended solids in the wastewater to react and form complexes. These complexes remove suspended solids and large molecular organic matter through adsorption and sedimentation, reducing the SS content of the wastewater and improving its biodegradability. The PAC dosage is 30-40 mg / L, and the PAM dosage is 1-1.5 mg / L.

[0048] S4: Wastewater after primary flocculation enters a radial flow primary sedimentation tank for solid-liquid separation. The primary sedimentation tank is designed with a surface loading rate of 1.0 m³ / (m²·h) and a hydraulic retention time of 2.0 hours. The settled sludge is collected in a sludge hopper by a scraper and periodically discharged into a physicochemical sludge tank.

[0049] S5: The effluent from the primary sedimentation tank enters the intermediate water tank as a transitional buffer unit to ensure stable system operation. The intermediate water tank is designed with a volume of 150m³ and a hydraulic retention time of 1.0 hour.

[0050] S6: The effluent from the intermediate water tank enters the high-efficiency hydrolysis acidification tower. Through the action of hydrolytic and acidifying bacteria, the recalcitrant organic matter (such as aromatic compounds and heterocyclic compounds) in the wastewater is converted into readily biodegradable organic matter, significantly improving the biodegradability of the wastewater. The hydrolysis acidification tower adopts an upflow anaerobic sludge blanket (UASB) structure, with a designed hydraulic retention time of 10 hours, a temperature controlled at 30-35℃, a pH value controlled at 6.5-7.0, a COD removal rate of 20%-30%, and a B / C ratio increase of 0.15-0.25.

[0051] S7: The hydrolyzed and acidified wastewater sequentially enters the primary and secondary aerobic tanks, where it is aerated by blowers. Microorganisms in the activated sludge digest and degrade the organic matter in the wastewater. The primary aerobic tank is designed with a volumetric loading rate of 0.6 kg COD / (m³·d), a dissolved oxygen concentration controlled at 2.5 mg / L, and a sludge concentration controlled at 3500 mg / L. The secondary aerobic tank is designed with a volumetric loading rate of 0.4 kg COD / (m³·d), a dissolved oxygen concentration controlled at 3.0 mg / L, and a sludge concentration controlled at 3000 mg / L. The blower system uses variable frequency control, automatically adjusting the fan frequency based on signals from the online DO monitoring instrument to achieve energy-saving operation.

[0052] S8: The effluent from the secondary aerobic tank enters the secondary sedimentation tank for sludge-water separation. The secondary sedimentation tank adopts a radial flow structure with a central inlet and peripheral outlet, designed with a surface loading rate of 0.8 m³ / (m²·h) and a hydraulic retention time of 3.0 hours. Part of the settled sludge is returned to the primary aerobic tank, with the return ratio controlled at 70%, and the remaining sludge is discharged into the biological sludge tank.

[0053] S9: The effluent from the secondary sedimentation tank enters the contact oxidation tank for further degradation of residual organic matter. The contact oxidation tank is filled with biological packing material with a specific surface area of ​​300 m² / m³, a filling rate of 60%, a dissolved oxygen concentration controlled at 3.5 mg / L, and a hydraulic retention time of 3.0 hours.

[0054] S10: The effluent from the contact oxidation tank enters the secondary flocculation tank, where PAC and PAM are added to react with the residual COD and SS in the water to form flocs. The dosage of PAC is 25-35 mg / L, and the dosage of PAM is 0.8-1.2 mg / L.

[0055] S11: Wastewater after secondary flocculation enters the final settling tank, where adsorption and sedimentation further reduce COD and SS levels. The final settling tank is designed with a surface loading rate of 0.6 m³ / (m²·h) and a hydraulic retention time of 2.5 hours.

[0056] S12: The effluent from the final sedimentation tank is tested by the online water quality monitoring system. When COD≤50mg / L, BOD5≤10mg / L, SS≤10mg / L, ammonia nitrogen≤5mg / L, and total phosphorus≤0.5mg / L, it is considered to meet the standards and is discharged through the discharge outlet; water that does not meet the standards is returned to the intermediate water tank for retreatment.

[0057] Sludge treatment system:

[0058] Sludge from the primary sedimentation tank, secondary sedimentation tank, and final sedimentation tank is collected into a physicochemical sludge tank and a biological sludge tank, respectively. The physicochemical sludge collected in the physicochemical sludge tank has a moisture content of approximately 98%, while the biological sludge collected in the biological sludge tank has a moisture content of approximately 99.2%. Both types of sludge undergo dewatering treatment using a plate and frame filter press at an operating pressure of 1.5 MPa, reducing the moisture content of the dewatered sludge to below 60%. The dewatered sludge then undergoes sludge drying treatment to further reduce the moisture content to below 40%, followed by sludge storage, and finally, sludge disposal is entrusted to a qualified unit.

[0059] Ozone deep treatment system:

[0060] To further improve effluent quality, an ozone buffer tank and an ozone reaction tank can be added after the contact oxidation tank. After ozone oxidation, the effluent from the final sedimentation tank can further degrade recalcitrant organic matter, improve effluent transparency, and kill pathogenic microorganisms. The ozone dosage is 10-15 mg / L, and the contact time is 15-20 minutes.

[0061] Emergency response system:

[0062] In the event of abnormal water quality (such as high-concentration shocks) or equipment malfunction, the system automatically directs wastewater to an emergency storage tank for temporary storage. The emergency tank has a designed volume of 800 m³, capable of holding 4-6 hours' worth of wastewater. Once the system returns to normal, the wastewater in the emergency tank is slowly returned to the treatment system via a booster pump, preventing any impact on the normally operating system.

[0063] Running example:

[0064] A wastewater treatment plant in an industrial park uses the process of this invention to treat enterprise wastewater, with a designed treatment capacity of 2000 m³ / d. The influent water quality is as follows: COD 800-1000 mg / L, BOD5 300-400 mg / L, SS 300-350 mg / L, ammonia nitrogen 50-60 mg / L, and total phosphorus 8-10 mg / L. After treatment by this process, the effluent water quality stably reaches: COD 35-45 mg / L, BOD5 5-8 mg / L, SS 5-8 mg / L, ammonia nitrogen 2-3 mg / L, and total phosphorus 0.3-0.4 mg / L, fully meeting the Class A standard requirements of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918-2002).

[0065] Operational data show that the process of this invention achieves average removal rates of 95.5%, 98.2%, 97.8%, 95.0%, and 95.5% for COD, BOD5, SS, ammonia nitrogen, and total phosphorus, respectively. It operates stably, has strong resistance to shocks, and reduces sludge production by 15%–20% compared to traditional processes.

[0066] The above description is merely illustrative of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, as long as they do not depart from the content of this specification or exceed the scope defined by the claims, all of which should fall within the protection scope of this invention.

Claims

1. A wastewater treatment process, characterized in that, Includes the following steps: S1: Collect the enterprise's wastewater into a new collection tank, and then transport it to a homogenization and equalization tank using a submersible pump; S2: In the homogenization and equalization tank, the wastewater is uniformly mixed and the water volume is adjusted using a submersible mixer; S3: The homogenized and equalized wastewater is introduced into the primary flocculation tank, and flocculant is added to cause the suspended solids in the wastewater to form complexes. S4: The wastewater after primary flocculation is introduced into a radial flow primary sedimentation tank for solid-liquid separation; S5: The effluent from the primary sedimentation tank is introduced into the intermediate water tank for buffering; S6: The effluent from the intermediate water tank is introduced into the high-efficiency hydrolysis acidification tower to convert the recalcitrant organic matter into readily biodegradable organic matter; S7: The hydrolyzed and acidified wastewater is sequentially introduced into the primary aerobic tank and the secondary aerobic tank, and aeration is carried out by blower, utilizing microorganisms to digest and degrade the organic matter in the wastewater; S8: The effluent from the secondary aerobic tank is introduced into the secondary sedimentation tank for mud-water separation; S9: The effluent from the secondary sedimentation tank is introduced into the contact oxidation tank, and the organic matter is further degraded by blower aeration. S10: The effluent from the contact oxidation tank is introduced into the secondary flocculation tank, and flocculants are added to cause COD and SS to react. S11: The wastewater after secondary flocculation is introduced into the final sedimentation tank, where COD and SS are reduced through adsorption and sedimentation. S12: Detect the water quality of the final sedimentation tank effluent. If it meets the standards, it will be discharged; otherwise, it will be returned to the treatment system.

2. The wastewater treatment process according to claim 1, characterized in that: The flocculants added in steps S3 and S10 are PAC and PAM, wherein the dosage of PAC is 20-50 mg / L and the dosage of PAM is 0.5-2 mg / L.

3. A wastewater treatment process according to claim 1 or 2, characterized in that: In step S6, the hydraulic residence time of the high-efficiency hydrolysis acidification tower is 8-12 hours, the temperature is controlled at 30-35℃, and the pH value is controlled at 6.0-7.

5.

4. The wastewater treatment process according to claim 1, characterized in that: In step S7, the dissolved oxygen concentrations in the primary aerobic tank and the secondary aerobic tank are controlled at 2-3 mg / L and 2-4 mg / L, respectively, and the sludge concentrations are controlled at 3000-4000 mg / L and 2500-3500 mg / L, respectively.

5. The wastewater treatment process according to claim 1, characterized in that: It also includes a sludge treatment system, which collects the sludge generated from the primary sedimentation tank, secondary sedimentation tank and final sedimentation tank into the physicochemical sludge tank and biological sludge tank respectively, and then performs sludge dewatering and drying treatment, and finally entrusts professional institutions to dispose of it.

6. The wastewater treatment process according to claim 5, characterized in that: It also includes a sludge return step, in which part of the sludge from the secondary sedimentation tank is returned to the primary aerobic tank, with the return ratio controlled at 50%-100%.

7. The wastewater treatment process according to claim 1, characterized in that: It also includes an ozone treatment step, which adds an ozone buffer tank and an ozone reaction tank after the contact oxidation tank to use ozone for deep oxidation treatment of wastewater.

8. The wastewater treatment process according to claim 1, characterized in that: It also includes an emergency treatment system that, in the event of abnormal water quality or equipment failure, directs wastewater into an emergency pool for temporary storage until the system is restored to normal before further treatment.

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