A treatment method and device system for high-alkalinity wastewater pre-acidification

Abstract

The present application relates to a kind of high alkalinity wastewater pre-acidification treatment method and its processing device system, the treatment method includes: the nutrient substance is added to the wastewater to be treated and is adjusted to obtain adjusted water;Part of the adjusted water is returned to adjust and handle, another part is added to the nutrient substance and is pre-acidification treatment, obtain pre-acidification water;Pre-acidification water is treated by anaerobic purification, obtain anaerobic purification water;Anaerobic purification water is treated by aeration and sedimentation in turn, obtain treated water.The treatment method and its processing device system provided by the present application can regulate the metabolic activity of microorganism, reduce the inhibitory effect of wastewater alkalinity and metal ions on anaerobic microorganism, improve the anaerobic removal rate of anaerobic purification treatment, reduce the adding cost of acidic substance and nutrient substance.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a method and system for pre-acidification of high-alkalinity wastewater. Background Technology

[0002] With the reduction in import quotas for waste paper, high-quality waste paper resources are facing a shortage, forcing the paper industry to rely on domestic waste paper as raw material. However, due to the long-term recycling of domestic waste paper, the composition of pulping wastewater has become more complex, with a higher pH value, posing potential harm to the environment and microorganisms, and increasing the difficulty of wastewater treatment.

[0003] Highly alkaline wastewater contains various alkaline substances, such as NaOH and Na₂CO₃. The presence of these substances causes the pH value of the wastewater to be much higher than normal, generally exceeding 9, and may even reach above 12. In addition, due to the presence of alkaline substances, the wastewater may also contain heavy metal ions, organic matter, etc., further leading to the complex chemical properties of highly alkaline wastewater.

[0004] Highly alkaline wastewater, with its alkalinity and harmful substances, inhibits anaerobic bacteria in existing anaerobic treatment systems. When the pH of the water entering the anaerobic system exceeds the activity range of anaerobic bacteria, the removal rate of the anaerobic stage drops sharply, pollutants cannot be effectively degraded, and environmental hazards exist. Currently, chemical precipitation and acid-base neutralization are the main methods for treating highly alkaline wastewater. Chemical precipitation, typically using sulfides or hydroxides, adds chemical reagents to the wastewater to precipitate harmful substances and separate them from the water. However, this method easily causes secondary pollution, and sulfides have a stronger and irreversible inhibitory effect on anaerobic bacteria. Acid-base neutralization adds acidic substances, typically sulfuric acid or hydrochloric acid, to the wastewater to neutralize alkaline substances and lower the pH. However, this method cannot provide the nutrients needed for anaerobic bacteria to degrade pollutants, and adding acidic substances increases treatment costs.

[0005] Therefore, providing a method and system for pre-acidification of high-alkalinity wastewater is a technical problem that needs to be solved in this field. Summary of the Invention

[0006] To address the above problems, the present invention aims to provide a method and device system for pre-acidification of high-alkalinity wastewater. Compared with the prior art, the treatment method and device system provided by the present invention can reduce the inhibitory effect of wastewater alkalinity and metal ions on anaerobic microorganisms by regulating the metabolic activities of microorganisms, thereby improving the anaerobic removal rate of anaerobic purification treatment and reducing the cost of adding acidic substances and nutrients.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for pre-acidification of highly alkaline wastewater, the method comprising the following steps:

[0009] (1) Add nutrients to the wastewater to be treated and adjust it to obtain adjusted water;

[0010] (2) A portion of the conditioned water obtained in step (1) is returned for further conditioning, and the other portion is treated with nutrients and pre-acidified to obtain pre-acidified water.

[0011] (3) The pre-acidified water obtained in step (2) is subjected to anaerobic purification treatment to obtain anaerobic purified water;

[0012] (4) The anaerobic purified water obtained in step (3) is subjected to aeration and sedimentation treatment in sequence to obtain treated water.

[0013] This invention addresses the problems of secondary pollution and anaerobic bacteria inhibition associated with chemical precipitation in treating highly alkaline wastewater, and the increased treatment costs associated with acid-base neutralization. This invention employs a microbial treatment method, utilizing the characteristics of hydrolytic bacteria in existing wastewater treatment systems. Hydrolytic bacteria are fermentative bacteria with hydrolytic capabilities. They expend energy to hydrolyze wastewater to obtain water-soluble substrates for fermentation, acquiring energy through intracellular biochemical reactions while simultaneously excreting metabolic products. In the conditioning and pre-acidification stages, complex organic matter in the wastewater is decomposed into simpler organic matter, such as organic acids and alcohols, and inorganic substances like CO2, NH3, and H2S, by hydrolytic bacteria (or acid-producing bacteria). When organic acids accumulate to a certain level, they lower the pH of the wastewater. This hydrolytic acidification process lowers the pH of the highly alkaline wastewater and decomposes alkaline substances. Furthermore, organic acids can precipitate some metal ions, reducing the inhibitory effect of high alkalinity and metal ions on subsequent anaerobic bacteria, thus improving the anaerobic removal rate. In the treatment method provided by this invention, on the one hand, by controlling and setting nutrient addition points at the front end of the conditioning treatment and the front end of the pre-acidification treatment, the hydrolysis and acidification process of the hydrolytic bacteria can be controlled. In particular, adding nutrients at the front end of the conditioning treatment can play a role in early acidification and prolong the residence time of hydrolysis and acidification. On the other hand, by controlling the partial circulation of the water after conditioning back to the conditioning treatment, the pH value of the wastewater in the conditioning treatment can be reduced by utilizing the organic acids accumulated in the water after conditioning, so as to further make the wastewater quality before anaerobic purification treatment meet the requirements and improve the anaerobic removal rate.

[0014] In this invention, the pre-acidification treatment, anaerobic purification treatment, and aeration treatment are all based on conventional wastewater treatment systems in the field. Specifically, pre-acidification treatment involves hydrolysis and acidification using hydrolytic bacteria (or acid-producing bacteria). During hydrolysis, polymers such as polysaccharides, polypeptides, and fats are broken down into monomers such as sugars, amino acids, and fatty acids. During acidification, these monomers are converted into organic acids, alcohols, aldehydes, ammonia, hydrogen sulfide, and carbon dioxide. Anaerobic purification treatment removes chemical and biological impurities from the water through the action of anaerobic bacteria. Anaerobic purification requires the addition of anaerobic granular sludge bacteria (VSS / TSS meeting ±65%). Anaerobic purification is generally performed at a temperature of 38-41℃ to optimize bacterial activity, and the influent pH is generally required to be 6.5-7.5. Aeration treatment introduces air into the water, utilizing dissolved oxygen to provide oxygen for the survival and metabolism of aerobic bacteria, thereby improving the degradation of organic matter.

[0015] Preferably, the pH value of the wastewater to be treated in step (1) is ≥9, for example, it can be 9, 10, 11 or 12, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0016] Preferably, the Fe in the wastewater to be treated 3+ The concentration is 1-3 mg / L, for example, it can be 1 mg / L, 1.2 mg / L, 1.5 mg / L, 1.8 mg / L, 2 mg / L, 2.2 mg / L, 2.5 mg / L, 2.8 mg / L or 3 mg / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] Preferably, the Ca in the wastewater to be treated 2+ The concentration is 300-700 mg / L, for example, it can be 300 mg / L, 320 mg / L, 350 mg / L, 380 mg / L, 400 mg / L, 420 mg / L, 450 mg / L, 480 mg / L, 500 mg / L, 520 mg / L, 550 mg / L, 580 mg / L, 600 mg / L, 620 mg / L, 650 mg / L, 680 mg / L or 700 mg / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] Preferably, the COD concentration of the wastewater to be treated is 6000-30000 mg / L, for example, it can be 6000 mg / L, 8000 mg / L, 10000 mg / L, 12000 mg / L, 15000 mg / L, 18000 mg / L, 20000 mg / L, 22000 mg / L, 25000 mg / L, 28000 mg / L or 30000 mg / L, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0019] Preferably, the temperature of the wastewater to be treated is 30-70℃, for example, it can be 30℃, 32℃, 35℃, 38℃, 40℃, 42℃, 45℃, 48℃, 50℃, 52℃, 55℃, 58℃, 60℃, 62℃, 65℃, 68℃ or 70℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0020] Preferably, the nutrients include a nitrogen source and / or a phosphorus source.

[0021] In this invention, the nitrogen or phosphorus source can be any nitrogen or phosphorus source commonly used as a nutrient in the art. For example, the nitrogen source can be nitrogen from urea and / or phosphate fertilizer, and the phosphorus source can be monoammonium phosphate. Furthermore, based on the residual nitrogen and phosphorus in the wastewater, the amount of auxiliary materials added can be reduced.

[0022] Preferably, in the conditioning process, the ratio of COD concentration, nitrogen addition, and phosphorus addition in the wastewater is (250-500):5:1, for example, it can be 250:5:1, 280:5:1, 300:5:1, 320:5:1, 350:5:1, 380:5:1, 400:5:1, 420:5:1, 450:5:1, 480:5:1, or 500:5:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] Preferably, in the pre-acidification treatment, the ratio of COD concentration, nitrogen addition, and phosphorus addition in the wastewater is (250-500):5:1, for example, it can be 250:5:1, 280:5:1, 300:5:1, 320:5:1, 350:5:1, 380:5:1, 400:5:1, 420:5:1, 450:5:1, 480:5:1, or 500:5:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] In this invention, by optimizing the ratio of COD concentration (mg / L), nitrogen addition (mg / L), and phosphorus addition (mg / L) during the treatment and pre-acidification processes, sufficient nutrients can be provided for the growth and metabolism of hydrolytic bacteria, ensuring that the hydrolytic bacteria can effectively carry out metabolic activities, thereby effectively reducing the pH value of highly alkaline wastewater.

[0025] Preferably, the pH value of the water after adjustment in step (1) is 6-8.9, for example, it can be 6, 6.2, 6.5, 6.8, 7, 7.2, 7.5, 7.8, 8, 8.2, 8.4, 8.6 or 8.9, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] Preferably, the regulated water is subjected to filtration and heat exchange treatment in sequence.

[0027] Preferably, the filter screen aperture is 1-3mm, for example, it can be 1mm, 1.5mm, 2mm, 2.5mm or 3mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] Preferably, the temperature of the wastewater undergoing pre-acidification treatment is 38-40℃, for example, it can be 38℃, 38.5℃, 39℃, 39.5℃ or 40℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] In this invention, because the wastewater temperature is high and the treatment process also generates heat, controlling the temperature of the wastewater undergoing pre-acidification is crucial for the growth and activity of hydrolyzing bacteria. This invention, by optimally controlling the aforementioned temperature range, can control the biochemical reaction rate of the hydrolyzing bacteria, avoid inhibiting their metabolic activity, and improve the pH reduction and metal ion removal effects. In this invention, the temperature of the wastewater entering the pre-acidification treatment is controlled according to changes in ambient temperature. When the ambient temperature is high, such as in summer, cooling is achieved through sequential filtration and heat exchange processes to meet the requirements for pre-acidification. When the ambient temperature is low, such as in winter, filtration and heat exchange devices are not required; heat exchange between the pipelines and the external environment is used to achieve the required wastewater temperature for pre-acidification.

[0030] Preferably, sludge is also produced after the conditioning treatment.

[0031] Preferably, the sludge generated during the conditioning process enters the sludge treatment unit via a sludge discharge pipeline.

[0032] Preferably, the amount of water returned for adjustment in step (2) accounts for 25-35% of the total amount of water after adjustment. For example, it can be 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34% or 35%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] In this invention, by optimizing the percentage of water returned for conditioning treatment to the total amount of water after conditioning, the pH value of the wastewater during conditioning treatment can be effectively controlled, thereby ensuring that the influent water quality meets the operational requirements of anaerobic purification treatment and improving the anaerobic removal rate.

[0034] Preferably, the pH value of the pre-acidified water in step (2) is 6-7, for example, it can be 6, 6.2, 6.5, 6.8 or 7, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the Fe in the pre-acidified water 3+ The concentration is 0-1.1 mg / L, for example, it can be 0 mg / L, 0.1 mg / L, 0.2 mg / L, 0.3 mg / L, 0.4 mg / L, 0.5 mg / L, 0.8 mg / L, 1 mg / L or 1.1 mg / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, the Ca in the pre-acidified water 2+ The concentration is 250-440 mg / L, for example, it can be 250 mg / L, 260 mg / L, 270 mg / L, 280 mg / L, 290 mg / L, 300 mg / L, 310 mg / L, 320 mg / L, 330 mg / L, 340 mg / L, 350 mg / L, 380 mg / L, 400 mg / L, 420 mg / L or 440 mg / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] Preferably, sludge is also produced after the pre-acidification treatment.

[0038] Preferably, the sludge generated from the pre-acidification treatment enters the sludge treatment unit via a sludge discharge pipeline.

[0039] In this invention, since organic acids and metal ions in the equalization tank and pre-acidification tank react to produce precipitation, long-term operation will reduce the effective treatment space of the tank. In this invention, the bottom sludge of the equalization tank and pre-acidification tank is preferably sent to the sludge treatment unit through the sludge discharge pipeline. This can avoid the sludge from affecting the effective volume of the tank, thereby further ensuring the removal effect of the subsequent anaerobic purification treatment.

[0040] Preferably, the pH value of the treated water in step (4) is 7-9, for example, it can be 7, 7.2, 7.4, 7.6, 7.8, 8, 8.2, 8.5, 8.8 or 9, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] Preferably, the COD concentration of the treated water is 150-250 mg / L, for example, it can be 150 mg / L, 160 mg / L, 170 mg / L, 180 mg / L, 190 mg / L, 200 mg / L, 210 mg / L, 220 mg / L, 230 mg / L, 240 mg / L or 250 mg / L, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0042] As a preferred embodiment of the first aspect of the present invention, the processing method includes the following steps:

[0043] (1) With pH value ≥ 9, Fe 3+ The concentration is 1-3 mg / L, Ca 2+ The wastewater to be treated has a concentration of 300-700 mg / L, a COD concentration of 6000-30000 mg / L, and a temperature of 30-70℃. Nutrients are added and the treatment is carried out. The nutrients include nitrogen sources and / or phosphorus sources. In the treatment, the ratio of COD concentration, nitrogen addition and phosphorus addition in the wastewater is (250-500):5:1. The resulting water has a pH value of 6-8.9.

[0044] (2) The conditioned water obtained in step (1) is filtered, with a filter screen pore size of 1-3 mm. Then, heat exchange is performed to bring the temperature of the pre-acidified wastewater to 38-40℃. A portion of this wastewater is returned for further conditioned treatment, accounting for 25-35% of the total conditioned water volume. The other portion is treated with nutrients and pre-acidified to obtain a pH of 6-7 and Fe... 3+ The concentration is 0-1.1 mg / L, Ca 2+ Pre-acidified water with a concentration of 250-440 mg / L;

[0045] Sludge is generated after the conditioning and pre-acidification treatments, and the sludge enters the sludge treatment unit through the sludge discharge pipeline.

[0046] (3) The pre-acidified water obtained in step (2) is subjected to anaerobic purification treatment to obtain anaerobic purified water;

[0047] (4) The anaerobic purified water obtained in step (3) is subjected to aeration and sedimentation treatment in sequence to obtain treated water with a pH value of 7-9 and a COD concentration of 150-250 mg / L.

[0048] In a second aspect, the present invention provides a treatment device system for pre-acidification of highly alkaline wastewater, the treatment device system being used in the treatment method for pre-acidification of highly alkaline wastewater described in the first aspect of the present invention.

[0049] The treatment system includes an equalization tank, a pre-acidification tank, an anaerobic reactor, an aeration tank, a secondary sedimentation tank, and a secondary sedimentation effluent tank, which are connected sequentially along the wastewater flow direction.

[0050] The inlet of the equalization tank is connected to the wastewater pipeline to be treated and the nutrient dosing pipeline, respectively.

[0051] The inlet of the pre-acidification tank is also connected to a nutrient dosing pipeline;

[0052] The main outlet pipe of the equalization tank is connected to the inlet of the pre-acidification tank and the equalization tank, respectively.

[0053] The secondary sedimentation tank is connected to the treated water drainage pipeline.

[0054] In the treatment system provided by this invention, nutrient dosing pipelines are installed at the front end of the equalization tank and the front end of the pre-acidification tank, providing sufficient nutrient elements for the hydrolysis and acidification by hydrolytic bacteria. This, in turn, generates organic acids to reduce the pH value and metal ion content of highly alkaline wastewater. Furthermore, by connecting the effluent main pipe of the equalization tank to the inlet of the equalization tank, partial recirculation of the regulated water is achieved. The organic acid content in the regulated water can be utilized to further reduce the pH value of the wastewater in the equalization treatment, thereby further ensuring the quality of the influent water for anaerobic purification.

[0055] Preferably, the drain pipe of the regulating tank is connected to the first outlet pipe and the second outlet pipe respectively.

[0056] Preferably, the first outlet pipeline is connected to the filtration device and the heat exchange device in sequence along the wastewater flow direction.

[0057] In this invention, the filtration device and heat exchange device can be any commonly used device in the art for filtering wastewater or exchanging heat. For example, the filtration device can be a fully automatic brush filter, and the heat exchange device can be a heat exchanger.

[0058] Preferably, the outlet of the heat exchange device and the outlet of the second water outlet pipeline are respectively connected to the main water outlet pipe of the regulating tank.

[0059] In this invention, by optimizing the design of the drainage pipe, the first outlet pipe, the second outlet pipe, the filtration device, the heat exchange device, the main outlet pipe, and their connection methods, the temperature of the wastewater entering the pre-acidification treatment can be controlled according to changes in ambient temperature. When the ambient temperature is high, such as in summer, the second outlet pipe is closed, and the wastewater passes through the filtration device and the heat exchange device in sequence to meet the requirements for pre-acidification treatment. When the ambient temperature is low, such as in winter, the first outlet pipe is closed, and there is no need to use the filtration and heat exchange devices. The wastewater passes directly through the second outlet pipe, and the temperature of the wastewater reaches the requirements for pre-acidification treatment by relying on the heat exchange between the pipe and the external environment.

[0060] Preferably, the main outlet pipe of the equalization tank is connected to the equalization tank via a return pipeline.

[0061] Preferably, the bottom sludge outlet of the equalization tank and the bottom sludge outlet of the pre-acidification tank are respectively connected to the sludge treatment unit via sludge discharge pipelines.

[0062] In this invention, by optimizing the sludge discharge pipeline and sludge treatment unit, the impact of sedimentation on the tank volume can be avoided, further ensuring the hydrolysis and acidification effect of the hydrolytic bacteria.

[0063] Preferably, the wastewater pipeline to be treated is also connected to the inlet of the emergency pool.

[0064] Preferably, the outlet of the accident pool is connected to the regulating pool.

[0065] In this invention, by preferably setting up an emergency pool, it can temporarily store wastewater in case of emergencies such as equipment failure or power outage in the treatment device system.

[0066] In this invention, the conveying pipeline of the processing device system is generally also equipped with components such as electric valves, flow meters, and pumps for the control, monitoring, and conveying of fluids.

[0067] Compared with the prior art, the present invention has the following beneficial effects:

[0068] (1) The treatment method provided by the present invention utilizes the hydrolysis and acidification effect of hydrolytic bacteria to reduce the pH value and metal ion content of highly alkaline wastewater by using the organic acids produced by them. Furthermore, the present invention, on the one hand, extends the residence time of the water body in the hydrolysis and acidification process by controlling the addition site of nutrients, thereby playing a role in early acidification; on the other hand, by controlling the partial circulation of the regulated water back to the regulated treatment, the pH value of the wastewater in the regulated treatment can be reduced by using the organic acids accumulated in the regulated water, further regulating the water quality of the wastewater entering the anaerobic purification treatment, ensuring the normal operation of the anaerobic purification treatment, and increasing the anaerobic removal rate to more than 59%. Under optimal conditions, the anaerobic removal rate can be increased to more than 80%.

[0069] (2) The treatment device system provided by the present invention has a simple structure, is easy to maintain, can effectively regulate the influent water quality of anaerobic purification treatment, avoids inhibition of anaerobic bacteria, and is conducive to industrial application.

[0070] (3) The treatment method provided by the present invention can reduce the cost of adding acidic substances. Compared with the existing treatment methods for highly alkaline wastewater, the present invention can save about RMB1,512,560 per year in the cost of acidic substance HCl. Although the present invention adds nutrients in the treatment process, the addition of some nutrients in the treatment process can accelerate the activity frequency of biological strains, so that the total amount of nutrients added calculated based on the COD concentration in the wastewater is significantly reduced compared with the existing methods. On the contrary, it can save RMB228,160 per year in the cost of adding nutrients (calculated based on urea and monoammonium phosphate). In the end, it can save a total of RMB1,740,720 per year in total reagent costs (cost of acidic substances and nutrients). Attached Figure Description

[0071] Figure 1 This is a schematic diagram of the processing device system described in Embodiment 1 of the present invention;

[0072] The components are as follows: 1-Equalization tank; 2-Pre-acidification tank; 3-Anaerobic reactor; 4-Aeration tank; 5-Secondary sedimentation tank; 6-Secondary sedimentation effluent tank; 7-Wastewater pipeline to be treated; 8-Nutrient dosing pipeline; 9-Treatment water drainage pipeline; 10-Drainage pipe; 11-First effluent pipeline; 12-Second effluent pipeline; 13-Main effluent pipe; 14-Return pipeline; 15-Sludge discharge pipeline; 16-Sludge treatment unit; 17-Emergency tank; 18-Electric valve; 19-Pump; 20-Nutrient storage tank; 21-One-way pump; 22-Filter device; 23-Heat exchange device; 24-Flow meter. Detailed Implementation

[0073] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0074] Example 1

[0075] This embodiment provides a method for pre-acidification of highly alkaline wastewater, the method comprising the following steps:

[0076] (1) Set the pH value to 10, Fe 3+ The concentration is 2 mg / L, Ca 2+The wastewater to be treated, with a concentration of 500 mg / L, a COD concentration of 20000 mg / L, and a temperature of 50°C, was treated with nutrients (specifically urea and monoammonium phosphate) and regulated. In the regulation treatment, the ratio of COD concentration, nitrogen addition, and phosphorus addition in the wastewater was 300:5:1, resulting in regulated water with a pH value of 7.95.

[0077] (2) The conditioned water obtained in step (1) is filtered with a filter screen having a pore size of 2 mm. Then, heat exchange is applied to bring the temperature of the pre-acidified wastewater to 39°C. A portion of this pre-acidified wastewater is returned for further conditioning, accounting for 30% of the total conditioned water volume. The remaining portion is treated with added nutrients and pre-acidified. The ratio of COD concentration, nitrogen addition, and phosphorus addition in the wastewater is 300:5:1, resulting in a pH of 6.15 and Fe... 3+ The concentration was 0.8 mg / L, Ca 2+ Pre-acidified water with a concentration of 380 mg / L;

[0078] Sludge is generated after the conditioning and pre-acidification treatments, and the sludge enters the sludge treatment unit through the sludge discharge pipeline.

[0079] (3) The pre-acidified water obtained in step (2) is subjected to anaerobic purification treatment to obtain anaerobic purified water;

[0080] (4) The anaerobic purified water obtained in step (3) is subjected to aeration and sedimentation treatment in sequence to obtain treated water with a pH value of 7.54 and a COD concentration of 178 mg / L.

[0081] This embodiment also provides a pre-acidification treatment device system for high-alkalinity wastewater, which is used in the above-mentioned pre-acidification treatment method for high-alkalinity wastewater. Figure 1As shown, the treatment system includes an equalization tank 1, a pre-acidification tank 2, an anaerobic reactor 3, an aeration tank 4, a secondary sedimentation tank 5, and a secondary sedimentation effluent tank 6, connected sequentially along the wastewater flow direction. The inlet of the equalization tank 1 is connected to the wastewater pipeline 7 and the nutrient addition pipeline 8, respectively. An electric valve 18 is installed on the wastewater pipeline 7. The inlet of the nutrient addition pipeline 8 is connected to the nutrient storage tank 20. The inlet of the pre-acidification tank 2 is also connected to the nutrient addition pipeline 8. The drain pipe 10 of the regulating tank 1 is connected to the first outlet pipe 11 and the second outlet pipe 12 respectively. The first outlet pipe 11 is connected to the filter device 22 and the heat exchange device 23 in sequence along the wastewater flow direction. The outlet of the heat exchange device 23 and the outlet of the second outlet pipe 12 are connected to the main outlet pipe 13 of the regulating tank 1 respectively. The main outlet pipe 13 of the regulating tank 1 is connected to the regulating tank 1 via the return pipe 14. A flow meter 24 is installed on the return pipe 14. When the ambient temperature is high, such as in summer, the second outlet water line 12 is closed. After adjustment, the water flows through the drain pipe 10, the first outlet water line 11, the filter device 22, and the heat exchange device 23 into the main outlet water line 13. The temperature is controlled to meet the pre-acidification treatment conditions. Then, it partially flows back through the return pipe 14. Both the return pipe 14 and the drain pipe 10 are equipped with flow meters 24. When the ambient temperature is low, such as in winter, the first outlet water line 11 is closed. After adjustment, the water flows through the drain pipe 10, the second outlet water line 12 into the main outlet water line 13. The temperature is controlled to meet the pre-acidification treatment conditions by utilizing the heat exchange between the ambient temperature and the pipe. Then, it partially flows back through the return pipe 14.

[0082] The bottom sludge outlets of the equalization tank 1 and the pre-acidification tank 2 are respectively connected to the sludge treatment unit 16 via the sludge discharge pipeline 15. The wastewater pipeline 7 to be treated is also connected to the inlet of the emergency tank 17. The outlet of the emergency tank 17 is connected to the equalization tank 1. The secondary sedimentation effluent tank 6 is connected to the treated water drainage pipeline 9.

[0083] In this embodiment, the fluid transport in each pipeline is powered by pump 19 or unidirectional pump 21.

[0084] Example 2

[0085] This embodiment provides a method for pre-acidification of highly alkaline wastewater, the method comprising the following steps:

[0086] (1) Set the pH value to 11, Fe 3+ The concentration is 1 mg / L, Ca 2+The wastewater to be treated, with a concentration of 300 mg / L, a COD concentration of 30000 mg / L, and a temperature of 30°C, was treated by adding nutrients (specifically urea and monoammonium phosphate) and conditioning. In the conditioning treatment, the ratio of COD concentration, nitrogen addition and phosphorus addition in the wastewater was 480:5:1, resulting in conditioned water with a pH value of 8.86.

[0087] (2) The conditioned water obtained in step (1) is filtered with a filter screen having a pore size of 1 mm. Then, heat exchange is applied to bring the temperature of the pre-acidified wastewater to 38°C. A portion of this pre-acidified wastewater is returned for further conditioning, accounting for 25% of the total conditioned water volume. The remaining portion is treated with added nutrients and pre-acidified. The ratio of COD concentration, nitrogen addition, and phosphorus addition in the wastewater is 480:5:1, resulting in a pH of 6.44 and Fe... 3+ The concentration was 1.1 mg / L, Ca 2+ Pre-acidified water with a concentration of 440 mg / L;

[0088] Sludge is generated after the conditioning and pre-acidification treatments, and the sludge enters the sludge treatment unit through the sludge discharge pipeline.

[0089] (3) The pre-acidified water obtained in step (2) is subjected to anaerobic purification treatment to obtain anaerobic purified water;

[0090] (4) The anaerobic purified water obtained in step (3) is subjected to aeration and sedimentation treatment in sequence to obtain treated water with a pH value of 7.66 and a COD concentration of 182 mg / L.

[0091] This embodiment also provides a pre-acidification treatment device system for high alkalinity wastewater, which is used in the above-mentioned pre-acidification treatment method for high alkalinity wastewater, and the treatment device system is the same as that in Embodiment 1.

[0092] Example 3

[0093] This embodiment provides a method for pre-acidification of highly alkaline wastewater, the method comprising the following steps:

[0094] (1) Set the pH value to 9, Fe 3+ The concentration is 3 mg / L, Ca 2+ The wastewater to be treated, with a concentration of 700 mg / L, a COD concentration of 6000 mg / L, and a temperature of 70°C, was treated with nutrients (specifically urea and monoammonium phosphate) and regulated. In the regulation treatment, the ratio of COD concentration, nitrogen addition, and phosphorus addition in the wastewater was 250:5:1, resulting in regulated water with a pH value of 7.32.

[0095] (2) The conditioned water obtained in step (1) is filtered with a filter screen having a pore size of 3 mm. Then, heat exchange is applied to bring the temperature of the pre-acidified wastewater to 40°C. A portion of this pre-acidified wastewater is returned for further conditioning, accounting for 25% of the total conditioned water volume. The remaining portion is treated with added nutrients and pre-acidified. The ratio of COD concentration, nitrogen addition, and phosphorus addition in the wastewater is 250:5:1, resulting in a pH of 6.01 and Fe... 3+ The concentration was 0.32 mg / L, Ca 2+ Pre-acidified water with a concentration of 310 mg / L;

[0096] Sludge is generated after the conditioning and pre-acidification treatments, and the sludge enters the sludge treatment unit through the sludge discharge pipeline.

[0097] (3) The pre-acidified water obtained in step (2) is subjected to anaerobic purification treatment to obtain anaerobic purified water;

[0098] (4) The anaerobic purified water obtained in step (3) is subjected to aeration and sedimentation treatment in sequence to obtain treated water with a pH value of 7.45 and a COD concentration of 153 mg / L.

[0099] This embodiment also provides a pre-acidification treatment device system for high alkalinity wastewater, which is used in the above-mentioned pre-acidification treatment method for high alkalinity wastewater, and the treatment device system is the same as that in Embodiment 1.

[0100] Example 4

[0101] This embodiment provides a method for pre-acidification of high alkalinity wastewater. The only difference from Embodiment 1 is that in the adjustment process, the ratio of COD concentration, nitrogen addition, and phosphorus addition in the wastewater is 150:5:1.

[0102] Example 5

[0103] This embodiment provides a pre-acidification treatment method for high alkalinity wastewater. The only difference from Embodiment 1 is that in the adjustment treatment, the ratio of COD concentration, nitrogen addition, and phosphorus addition in the wastewater is 600:5:1.

[0104] Example 6

[0105] This embodiment provides a pre-acidification treatment method for high alkalinity wastewater. The only difference from Embodiment 1 is that in the pre-acidification treatment, the ratio of COD concentration, nitrogen addition, and phosphorus addition in the wastewater is 150:5:1.

[0106] Example 7

[0107] This embodiment provides a method for pre-acidification of high-alkalinity wastewater. The only difference from Embodiment 1 is that in the pre-acidification treatment, the ratio of COD concentration, nitrogen addition, and phosphorus addition in the wastewater is 600:5:1.

[0108] Example 8

[0109] This embodiment provides a method for pre-acidification of high-alkalinity wastewater. The only difference from Embodiment 1 is that the temperature of the wastewater undergoing pre-acidification is 30°C.

[0110] Example 9

[0111] This embodiment provides a method for pre-acidification of high-alkalinity wastewater. The only difference from Embodiment 1 is that the temperature of the wastewater undergoing pre-acidification is 50°C.

[0112] Example 10

[0113] This embodiment provides a method for pre-acidification of high-alkalinity wastewater. The only difference from Embodiment 1 is that the amount of water returned for conditioning treatment accounts for 10% of the total amount of water after conditioning.

[0114] Example 11

[0115] This embodiment provides a method for pre-acidification of high-alkalinity wastewater. The only difference from Embodiment 1 is that the amount of water returned for conditioning treatment accounts for 45% of the total amount of water after conditioning.

[0116] Comparative Example 1

[0117] This comparative example provides a method for pre-acidification of high-alkalinity wastewater, which differs from Example 1 only in that no nutrients are added during the conditioning process.

[0118] Comparative Example 2

[0119] This comparative example provides a method for pre-acidification of high-alkalinity wastewater. The only difference between this method and Example 1 is that no nutrients are added during the pre-acidification treatment.

[0120] Comparative Example 3

[0121] This comparative example provides a method for pre-acidification of high-alkalinity wastewater. The only difference from Example 1 is that the water after adjustment is not returned to the equalization tank, but enters the pre-acidification tank for pre-acidification treatment.

[0122] Comparative Example 4

[0123] This comparative example provides a method for pre-acidification of high-alkalinity wastewater. The only difference from Example 1 is that no nutrients are added during the conditioning process, and the water after conditioning is not returned to the conditioning tank, but enters the pre-acidification tank for pre-acidification treatment.

[0124] Taking Example 1 and Comparative Example 4 as examples, Comparative Example 4 is a conventional treatment method for treating highly alkaline wastewater. In Comparative Example 4, in order to ensure the normal activity of anaerobic bacteria, approximately 16.3 t / d of acidic substance HCl needs to be added. However, in Example 1, no HCl needs to be added. Compared with Comparative Example 4, Example 1 can save approximately RMB 1,512,560 per year in cost of acidic substance HCl.

[0125] In Example 1, the addition of some nutrients during the conditioning treatment accelerated the activity frequency of the microbial strains. The total amount of nutrient salts required (conditioning treatment and pre-acidification treatment) was reduced by approximately 10% compared to Comparative Example 4. Phosphate (calculated as monoammonium phosphate) salt was reduced by 0.05 t / d, and nitrogen (calculated as urea) salt was reduced by 0.15 t / d. Based on the price of phosphate salt at 5209 yuan / t and nitrogen salt at 2431 yuan / t, Example 1 reduced the cost of nutrients, resulting in a saving of 151.256 + 22.816 = 174.072 million yuan / year in reagent costs (saving on acidic substances and nutrient costs) compared to Comparative Example 4.

[0126] The anaerobic removal rate of anaerobic purification treatment in Examples 1-11 and Comparative Examples 1-4 was detected by rapid spectrophotometry, and the results are shown in Table 1.

[0127] Table 1

[0128] Anaerobic removal rate / % Example 1 81 Example 2 80 Example 3 80 Example 4 72 Example 5 74 Example 6 70 Example 7 71 Example 8 66 Example 9 59 Example 10 78 Example 11 77 Comparative Example 1 57 Comparative Example 2 59 Comparative Example 3 72 Comparative Example 4 45

[0129] The following points can be observed from the data in Table 1:

[0130] (1) As can be seen from the data of Examples 1-11, the treatment method provided by the present invention can ensure the normal operation of anaerobic purification treatment while increasing the anaerobic removal rate to more than 59%, and under better conditions, it can increase the anaerobic removal rate to more than 80%.

[0131] (2) A comprehensive comparison of the data from Examples 1, 4-5, and 6-7 shows that the only difference between Examples 4-5 and Example 1 is that the ratio of COD concentration, nitrogen addition, and phosphorus addition in the wastewater during the adjustment treatment is not within the preferred range of this invention. The only difference between Examples 6-7 and Example 1 is that the ratio of COD concentration, nitrogen addition, and phosphorus addition in the wastewater during the pre-acidification treatment is not within the preferred range of this invention. The anaerobic removal rate in Example 1 is significantly higher than that in Examples 4-7. Therefore, this invention can further adjust the wastewater quality entering the anaerobic purification treatment and improve the anaerobic removal rate by optimizing the control of the ratio of COD concentration, nitrogen addition, and phosphorus addition in the wastewater during the adjustment treatment and pre-acidification treatment.

[0132] (3) A comprehensive comparison of the data from Example 1 and Examples 8-9 shows that the only difference between Examples 8-9 and Example 1 is that the temperature of the pre-acidified wastewater is not within the preferred range of the present invention. The anaerobic removal rate in Example 1 is significantly higher than that in Examples 8-9. Therefore, the present invention can further improve the anaerobic removal rate in subsequent stages by optimally controlling the temperature of the pre-acidified wastewater.

[0133] (4) A comprehensive comparison of the data from Example 1 and Examples 10-11 shows that the only difference between Example 10-11 and Example 1 is that the percentage of water returned for conditioning treatment is not within the preferred range of the present invention. The anaerobic removal rate in Example 1 is significantly higher than that in Example 10-11. Therefore, the present invention can reduce the pH value of the wastewater in the conditioning treatment by utilizing the organic acids accumulated in the conditioned water by optimizing the percentage of water returned for conditioning treatment to the total amount of conditioned water, thereby further improving the subsequent anaerobic removal rate.

[0134] (5) A comprehensive comparison of the data from Example 1 and Comparative Examples 1-4 shows that the only difference between Comparative Examples 1-2 and Example 1 is that no nutrients are added during the conditioning or pre-acidification treatment. The only difference between Comparative Example 3 and Example 1 is that the water after conditioning is not returned to the conditioning tank. The only difference between Comparative Example 4 and Example 1 is that no nutrients are added during the conditioning treatment and the water after conditioning is not returned to the conditioning tank (Comparative Example 4 corresponds to the conventional treatment method). Example 1 can achieve a high anaerobic removal rate, and Example 1 can significantly save 1,740,720 yuan / year in reagent costs compared to Comparative Example 4. Therefore, the treatment method provided by the present invention can reduce the adverse effects of highly alkaline wastewater on anaerobic purification treatment, improve the anaerobic removal rate, and reduce reagent addition costs.

[0135] In summary, the treatment method and its device system provided by this invention can reduce the inhibitory effect of wastewater alkalinity and metal ions on anaerobic microorganisms by regulating the metabolic activities of microorganisms, thereby improving the anaerobic removal rate of anaerobic purification treatment and reducing the cost of adding acidic substances and nutrients.

[0136] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for pre-acidification of high-alkalinity wastewater, characterized in that, The processing method includes the following steps: (1) Add nutrients to the wastewater to be treated and adjust it to obtain adjusted water; (2) A portion of the regulated water obtained in step (1) is returned for further regulated treatment, and the other portion is treated with nutrients and pre-acidified to obtain pre-acidified water; (3) The pre-acidified water obtained in step (2) is subjected to anaerobic purification treatment to obtain anaerobic purified water; (4) The anaerobic purified water obtained in step (3) is subjected to aeration and sedimentation treatment in sequence to obtain treated water; Wherein, the pH value of the wastewater to be treated in step (1) is ≥9; The nutrients include nitrogen and / or phosphorus sources; In the aforementioned conditioning treatment, the ratio of COD concentration, nitrogen addition, and phosphorus addition in the wastewater is (250-500):5:

1. In the pre-acidification treatment, the ratio of COD concentration, nitrogen addition, and phosphorus addition in the wastewater is (250-500):5:

1. In step (2), the amount of water returned for adjustment treatment accounts for 25-35% of the total amount of water after adjustment.

2. The processing method according to claim 1, characterized in that, Fe in the wastewater to be treated 3+ The concentration is 1-3 mg / L.

3. The processing method according to claim 1, characterized in that, Ca in the wastewater to be treated 2+ The concentration is 300-700 mg / L.

4. The processing method according to claim 1, characterized in that, The COD concentration of the wastewater to be treated is 6000-30000 mg / L.

5. The processing method according to claim 1, characterized in that, The temperature of the wastewater to be treated is 30-70℃.

6. The processing method according to claim 1, characterized in that, The pH value of the water after adjustment in step (1) is 6-8.

9.

7. The processing method according to claim 1, characterized in that, The regulated water is then subjected to filtration and heat exchange treatment in sequence.

8. The processing method according to claim 7, characterized in that, The filter screen has a pore size of 1-3 mm.

9. The processing method according to claim 1, characterized in that, The temperature of the wastewater undergoing pre-acidification treatment is 38-40℃.

10. The processing method according to claim 1, characterized in that, The conditioning process also produces sludge.

11. The processing method according to claim 10, characterized in that, The sludge generated during the conditioning process enters the sludge treatment unit via a sludge discharge pipeline.

12. The processing method according to claim 1, characterized in that, The pH value of the pre-acidified water in step (2) is 6-7.

13. The processing method according to claim 1, characterized in that, Fe in the pre-acidified water 3+ The concentration is 0-1.1 mg / L.

14. The processing method according to claim 1, characterized in that, The Ca in the pre-acidified water 2+ The concentration is 250-440 mg / L.

15. The processing method according to claim 1, characterized in that, The pre-acidification treatment also produces sludge.

16. The processing method according to claim 15, characterized in that, The sludge generated from the pre-acidification treatment enters the sludge treatment unit via a sludge discharge pipeline.

17. The processing method according to claim 1, characterized in that, The pH value of the treated water in step (4) is 7-9.

18. The processing method according to claim 1, characterized in that, The COD concentration of the treated water is 150-250 mg / L.

19. A pre-acidification treatment system for highly alkaline wastewater, characterized in that, The treatment device system is used in the pre-acidification treatment method for high-alkalinity wastewater according to any one of claims 1-18; The treatment system includes an equalization tank, a pre-acidification tank, an anaerobic reactor, an aeration tank, a secondary sedimentation tank, and a secondary sedimentation effluent tank, which are connected sequentially along the wastewater flow direction. The inlet of the equalization tank is connected to the wastewater pipeline to be treated and the nutrient dosing pipeline, respectively. The inlet of the pre-acidification tank is also connected to a nutrient dosing pipeline; The main outlet pipe of the equalization tank is connected to the inlet of the pre-acidification tank and the equalization tank, respectively. The secondary sedimentation tank is connected to the treated water drainage pipeline.

20. The processing apparatus system according to claim 19, characterized in that, The drainage pipes of the regulating tank are connected to the first and second outlet water pipes, respectively.

21. The processing apparatus system according to claim 20, characterized in that, The first outlet pipeline is connected to the filtration device and the heat exchange device in sequence along the wastewater flow direction.

22. The processing apparatus system according to claim 21, characterized in that, The outlet of the heat exchange device and the outlet of the second water outlet pipeline are respectively connected to the main water outlet pipe of the regulating tank.

23. The processing apparatus system according to claim 19, characterized in that, The main outlet pipe of the equalization tank is connected to the equalization tank via a return pipeline.

24. The processing apparatus system according to claim 19, characterized in that, The bottom sludge outlets of the equalization tank and the pre-acidification tank are respectively connected to the sludge treatment unit via sludge discharge pipelines.

25. The processing apparatus system according to claim 19, characterized in that, The wastewater pipeline to be treated is also connected to the inlet of the emergency pool.

26. The processing apparatus system according to claim 25, characterized in that, The outlet of the accident pool is connected to the regulating pool.

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