Preparation method of sludge alkaline hydrolysis carbon source, water treatment carbon source containing sludge alkaline hydrolysis carbon source and application of water treatment carbon source in sewage treatment

Abstract

The invention discloses a preparation method of a sludge alkaline hydrolysis carbon source, a water treatment carbon source containing the sludge alkaline hydrolysis carbon source and application of the water treatment carbon source in sewage treatment. The preparation method comprises the following steps: sequentially carrying out alkaline hydrolysis, hydrolytic acidification and solid-liquid separation treatment on the waste sludge of a sewage plant, effectively destroying the cell structure and extracellular polymeric substances of the sludge, releasing organic matters to increase the soluble chemical oxygen demand (SCOD), and carrying out medium-temperature anaerobic hydrolytic acidification to generate volatile fatty acid (VFAs) mainly containing acetic acid. Optionally, struvite precipitation may also be performed before solid-liquid separation to remove phosphorus. The finally prepared sludge alkaline hydrolysis carbon source is high in COD concentration and excellent in biodegradability and can replace an outsourced carbon source, the cost of the carbon source is reduced by more than 58% compared with that of the outsourced carbon source under the same COD amount, meanwhile, sludge reduction is achieved, and annual treatment cost is remarkably saved.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and more specifically, to a method for preparing a carbon source from sludge alkaline hydrolysis, a carbon source for water treatment containing the carbon source from sludge alkaline hydrolysis, and its application in wastewater treatment. Background Technology

[0002] With my country's ever-increasing demands for water environmental quality, wastewater treatment plant effluent must consistently meet or exceed the Class A standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB 18918-2002) (such as Class IV surface water), making nitrogen and phosphorus removal increasingly challenging. However, most urban wastewater suffers from a low carbon-to-nitrogen ratio (C / N), resulting in insufficient external carbon sources for the denitrification process and severely impacting total nitrogen (TN) removal efficiency.

[0003] Currently, wastewater treatment plants generally rely on purchasing commercial carbon sources (such as sodium acetate and methanol) to compensate for insufficient internal carbon sources. However, these purchased reagents are expensive, have high transportation costs, and unstable supply chains, resulting in a continuous increase in operating costs. In 2023, a certain plant spent as much as 53.347 million yuan on carbon source reagents, all of which was purchased from external suppliers. The procurement of carbon source reagents has become a key bottleneck restricting the company's cost reduction, efficiency improvement, and stable operation.

[0004] Meanwhile, wastewater treatment processes generate a large amount of excess sludge (with a moisture content of approximately 80%) daily, and its disposal costs are high. Traditional treatment methods mostly involve dewatering followed by incineration or landfilling, which not only consumes energy but also wastes the abundant organic matter resources in the sludge. Current technologies for directly anaerobic fermenting sludge to produce acid often suffer from problems such as difficulty in cell wall disruption, insufficient release of organic matter, long hydrolysis and acidification cycles (usually requiring several days), low yields of volatile fatty acids (VFAs), and a low proportion of acetic acid. This results in poor efficiency and economic viability of sludge-to-carbon conversion, making it difficult to stably replace purchased carbon sources.

[0005] Against this backdrop, converting waste sludge into a usable carbon source, achieving "waste treatment with waste," has become a technological direction that combines economic viability and sustainability. Therefore, this invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a carbon source from sludge alkaline hydrolysis, a carbon source for water treatment containing the carbon source from sludge alkaline hydrolysis, and its application in wastewater treatment, so as to provide a low-cost and sustainable carbon source for wastewater treatment.

[0007] This invention is implemented as follows: In a first aspect, the present invention provides a method for preparing a carbon source for sludge alkaline hydrolysis, comprising the following steps: (1) Alkali hydrolysis treatment of waste sludge from sewage treatment plants; (2) The sludge after alkaline hydrolysis is subjected to hydrolysis and acidification treatment; (3) The mixture after hydrolysis and acidification is subjected to solid-liquid separation, and the liquid phase is collected as the carbon source for the alkaline hydrolysis of the sludge.

[0008] In an optional embodiment, the alkaline hydrolysis treatment is performed at a temperature of 25-70°C, a pH of 11-12, and a time of 1-2 hours.

[0009] In an optional embodiment, the hydrolysis acidification treatment is carried out at a temperature of 33-37°C, a pH of 9.8-10.2, and a time of 9-11 hours.

[0010] In an optional embodiment, after the hydrolysis and acidification treatment and before solid-liquid separation, struvite precipitation is performed. The pH of the struvite precipitation step is 8.5-9.5, and a magnesium source is added, wherein the magnesium source is at least one of magnesium chloride, magnesium sulfate, or magnesium oxide.

[0011] In an optional embodiment, before the alkaline hydrolysis treatment, the waste sludge from the wastewater treatment plant is diluted to a total suspended solids (TSS) concentration of 75-105 g / L.

[0012] Secondly, the present invention provides a carbon source for wastewater treatment, including a sludge alkaline hydrolysis carbon source prepared by any of the preparation methods described in the foregoing embodiments.

[0013] In an optional implementation, the carbon source for wastewater treatment meets at least one of the following performance indicators: (a) B / C ratio ≥ 0.4; (b) The content of volatile fatty acids (VFAs) is ≥5g / L, of which acetic acid accounts for not less than 60%; (c) When used in the A² / O process, the carbon-to-nitrogen ratio (C:N) ≤ 2.2:1 and the total nitrogen (TN) removal rate ≥ 70%; (d) Chemical oxygen demand (COD) is 15,000-35,000 mg / L.

[0014] In an optional embodiment, a composite carbon source is also included, wherein the composite carbon source is selected from at least one of ethylene glycol, glycerol, molasses, and sludge fermentation broth.

[0015] Thirdly, the present invention provides a wastewater treatment method, which uses the A² / O process for wastewater treatment and adds the carbon source for wastewater treatment described in any of the foregoing embodiments to the anoxic section of the A² / O process.

[0016] In an optional embodiment, the carbon-to-nitrogen ratio of the anoxic section is 2.0-5.0:1, the hydraulic retention time of the anoxic section is 100-180 min, and the hydraulic retention time of the aerobic section is 180-280 min.

[0017] The present invention has the following beneficial effects: This application achieves efficient conversion and recycling of waste resources by sequentially treating sludge through alkaline hydrolysis, hydrolysis-acidification, and solid-liquid separation. First, alkaline hydrolysis effectively disrupts the sludge cell structure and extracellular polymers, promoting the dissolution and release of organic matter and significantly increasing the soluble COD (SCOD) concentration, creating favorable conditions for subsequent acid production. The subsequent hydrolysis-acidification stage is carried out under mesophilic, anaerobic conditions, further degrading macromolecular organic matter into volatile fatty acids (VFAs), primarily acetic acid, which is the most readily available and high-quality carbon source during denitrification. The final liquid phase obtained through solid-liquid separation, namely the "sludge alkaline hydrolysis carbon source," exhibits excellent biodegradability and is fully capable of replacing purchased composite carbon sources.

[0018] This application significantly reduces wastewater treatment operating costs. Compared to purchased carbon sources, the carbon source provided by this application, derived from sludge alkaline hydrolysis, offers a significantly lower cost. Simultaneously, due to optimized carbon source composition, the optimal carbon-to-nitrogen (C / N) ratio is drastically reduced, decreasing the carbon source required per unit of denitrification by nearly half, resulting in a substantial decrease in cost per ton of water treated and outstanding economic benefits. Furthermore, this process achieves significant sludge reduction; treating a certain amount of wet sludge reduces the production of oven-dried sludge, significantly lowering disposal costs. Taking a conventional-scale water plant as an example, the annual savings in disposal costs are considerable, resulting in significant overall benefits.

[0019] In terms of system operation, the carbon source in this application can be rapidly utilized in the anoxic section, effectively avoiding the impact of residual carbon source on effluent COD. After subsequent aerobic treatment, the effluent TN can reach Class A or Class IV surface water standards, with good total nitrogen removal effect and stable and reliable operation. This solution also has good engineering promotion value, as it can realize alkaline hydrolysis function by modifying existing sludge storage tanks without large-scale additional land occupation. The device has a high degree of integration and is suitable for water plants of different sizes. Overall, this technology realizes a circular economy model of "treating waste with waste and turning waste into treasure," which not only reduces operating costs and environmental burden, but also promotes the transformation and upgrading of wastewater treatment plants towards green, low-carbon, and resource self-sufficiency. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 The graph shows the change in SCOD of the sludge alkaline hydrolysis carbon source prepared in Examples 1 and 3 during long-term storage.

[0022] Figure 2 The graph shows the change in BOD5 of the sludge alkaline hydrolysis carbon source prepared in Examples 1 and 3 during long-term storage.

[0023] Figure 3 The graph shows the change in BOD5 / SCOD value of the sludge alkaline hydrolysis carbon source prepared in Examples 1 and 3 during long-term storage.

[0024] Figure 4 The TN change curves of the sludge alkaline hydrolysis carbon source prepared in Examples 1 and 3 during long-term storage.

[0025] Figure 5 The NH3 carbon source prepared for alkaline hydrolysis of sludge in Examples 1 and 3 was used during long-term storage. The curve showing the change in N.

[0026] Figure 6 The graph shows the change in TP during long-term storage of the sludge alkaline hydrolysis carbon source prepared in Examples 1 and 3.

[0027] Figure 7 The graph shows the change in phosphate ions during long-term storage of the sludge alkaline hydrolysis carbon source prepared in Examples 1 and 3.

[0028] Figure 8 This is a graph showing the change in total nitrogen (TN) in the effluent from the denitrification experiments using different carbon sources in Example 4.

[0029] Figure 9 This is a graph showing the variation of SCOD in the effluent from the denitrification experiments using different carbon sources in Example 4.

[0030] Figure 10 This is a graph showing the change in TP in the effluent of the denitrification experiment with different carbon sources in Example 4.

[0031] Figure 11 This is a graph showing the pH change of the effluent from the denitrification experiments using different carbon sources in Example 4.

[0032] Figure 12 The graph shows the variation of SCOD (Symptoms of Coefficient of Carbon) of the high-temperature carbon source under different C / N addition ratios in Example 5.

[0033] Figure 13 This is a graph showing the variation of SCOD (Single Scores of Carbon) under different C / N addition ratios using a room-temperature carbon source in Example 5.

[0034] Figure 14 This is a graph showing the change in TN (total nitrogen) of the high-temperature carbon source under different C / N addition ratios in Example 5.

[0035] Figure 15 This is a graph showing the change in TN (total nitrogen) under different C / N ratios using a room-temperature carbon source in Example 5.

[0036] Figure 16 In Example 5, the high-temperature carbon source NH3 was used under different C / N addition ratios. The curve showing the change in N.

[0037] Figure 17 In Example 5, NH3 was used as the carbon source at room temperature under different C / N addition ratios. The curve showing the change in N.

[0038] Figure 18 This is a graph showing the variation of TP in the high-temperature carbon source under different C / N addition ratios in Example 5.

[0039] Figure 19 This is a graph showing the variation of TP (Total Phosphorus) at different C / N ratios using a room-temperature carbon source in Example 5.

[0040] Figure 20 This is a graph showing the pH variation of the high-temperature carbon source in Example 5 under different C / N addition ratios.

[0041] Figure 21 This is a graph showing the pH variation of a room-temperature carbon source under different C / N addition ratios in Example 5.

[0042] Figure 22 This is a process flow diagram for Example 6. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0044] The following abbreviations apply to this document: Carbon-to-nitrogen ratio (C / N): The ratio of the mass concentrations of carbon to nitrogen; Total nitrogen (TN): The total amount of inorganic and organic nitrogen in water in all its forms; B / C: The ratio of BOD5 to COD (a biochemical indicator). VFAs: Volatile fatty acids; A² / O process: Anaerobic-Anoxic-Aerobic process; C / N: Carbon-to-nitrogen ratio; COD: Chemical Oxygen Demand; SCOD: Dissolved Chemical Oxygen Demand; BOD5: Five-day biochemical oxygen demand; NH3-N: ammonia nitrogen; TP: Total phosphorus.

[0045] The development of resource-based sludge treatment and disposal technologies has always been an urgent problem to be solved both domestically and internationally. By converting sludge organic matter into volatile fatty acids (VFAs) through anaerobic fermentation, and then using VFAs as chemical raw materials or supplementary carbon sources for nitrogen and phosphorus removal, "waste can be treated with waste" can be achieved, making it a technological direction that combines economic efficiency and sustainability.

[0046] This invention provides a method for preparing a carbon source for sludge alkaline hydrolysis, comprising the following steps: (1) Alkali hydrolysis treatment of waste sludge from sewage treatment plants; (2) The sludge after alkaline hydrolysis is subjected to hydrolysis and acidification treatment; (3) The mixture after hydrolysis and acidification is subjected to solid-liquid separation, and the liquid phase is collected as the carbon source for the alkaline hydrolysis of the sludge.

[0047] This application achieves efficient conversion and recycling of waste resources, and has significant technical advantages: This application achieves efficient conversion and recycling of waste resources by sequentially treating sludge through alkaline hydrolysis, hydrolysis-acidification, and solid-liquid separation. First, alkaline hydrolysis effectively disrupts the sludge cell structure and extracellular polymers, promoting the dissolution and release of organic matter and significantly increasing the soluble COD (SCOD) concentration, creating favorable conditions for subsequent acid production. The subsequent hydrolysis-acidification stage is carried out under mesophilic, anaerobic conditions, further degrading macromolecular organic matter into volatile fatty acids (VFAs), primarily acetic acid, which is the most readily available and high-quality carbon source during denitrification. The final liquid phase obtained through solid-liquid separation, namely the "sludge alkaline hydrolysis carbon source," exhibits excellent biodegradability and is fully capable of replacing purchased composite carbon sources.

[0048] This application significantly reduces wastewater treatment operating costs. Compared to purchased carbon sources, the carbon source provided by this application, derived from sludge alkaline hydrolysis, offers a significantly lower cost. Simultaneously, due to optimized carbon source composition, the optimal carbon-to-nitrogen (C / N) ratio is drastically reduced, decreasing the carbon source required per unit of denitrification by nearly half, resulting in a substantial decrease in cost per ton of water treated and outstanding economic benefits. Furthermore, this process achieves significant sludge reduction; treating a certain amount of wet sludge reduces the production of oven-dried sludge, significantly lowering disposal costs. Taking a conventional-scale water plant as an example, the annual savings in disposal costs are considerable, resulting in significant overall benefits.

[0049] In terms of system operation, the carbon source in this application can be rapidly utilized in the anoxic section, effectively avoiding the impact of residual carbon source on effluent COD. After subsequent aerobic treatment, the effluent TN can reach Class A or Class IV surface water standards, with good total nitrogen removal effect and stable and reliable operation. This scheme also has good engineering promotion value, as it can realize the alkaline hydrolysis function by modifying existing sludge storage tanks, without the need for large-scale new land occupation. The device has a high degree of integration and is suitable for water plants of different sizes. Overall, this technology realizes a circular economy model of "treating waste with waste and turning waste into treasure," which not only reduces operating costs and environmental burden, but also promotes the transformation and upgrading of sewage treatment plants towards green, low-carbon, and resource self-sufficiency. In an optional embodiment, the alkaline hydrolysis treatment temperature is 25-70℃, the pH is 11-12, and the time is 1-2 hours.

[0050] In an optional embodiment, the hydrolysis acidification treatment is carried out at a temperature of 33-37°C, a pH of 9.8-10.2, and a time of 9-11 hours.

[0051] In an optional embodiment, after the hydrolysis and acidification treatment and before solid-liquid separation, struvite precipitation is performed. The pH of the struvite precipitation step is 8.5-9.5, and a magnesium source is added, wherein the magnesium source is at least one of magnesium chloride, magnesium sulfate, or magnesium oxide.

[0052] In an optional embodiment, before the alkaline hydrolysis treatment, the waste sludge from the wastewater treatment plant is diluted to a total suspended solids (TSS) concentration of 75-105 g / L.

[0053] The present invention also provides a carbon source for wastewater treatment, including a sludge alkaline hydrolysis carbon source prepared by any of the preparation methods described in the foregoing embodiments.

[0054] In an optional implementation, the carbon source for wastewater treatment meets at least one of the following performance indicators: (a) B / C ratio ≥ 0.4; (b) The content of volatile fatty acids (VFAs) is ≥5g / L, of which acetic acid accounts for not less than 60%; (c) When used in the A² / O process, the carbon-to-nitrogen ratio (C:N) ≤ 2.2:1 and the total nitrogen (TN) removal rate ≥ 70%; (d) Chemical oxygen demand (COD) is 15,000-35,000 mg / L.

[0055] In an optional embodiment, a composite carbon source is also included, wherein the composite carbon source is selected from at least one of ethylene glycol, glycerol, molasses, and sludge fermentation broth.

[0056] Specifically, the composite carbon source can be selected from waste refrigerant from wind farms, waste glycerol, waste molasses, fermentation broth, etc. In some embodiments, the composite carbon source is prepared with a ratio of 40% glycerol, 30% molasses, 10% wind turbine coolant, and 20% water, resulting in a density of 1.21 g / cm³. 3 The COD equivalent is approximately 730,000 mg / L.

[0057] The present invention also provides a wastewater treatment method, which uses the A² / O process for wastewater treatment and adds the carbon source for wastewater treatment described in any of the foregoing embodiments to the anoxic section of the A² / O process.

[0058] In an optional embodiment, the carbon-to-nitrogen ratio of the anoxic section is 2.0-5.0:1, the hydraulic retention time of the anoxic section is 100-180 min, and the hydraulic retention time of the aerobic section is 180-280 min.

[0059] This application involves sequentially performing alkaline hydrolysis, hydrolysis acidification, and solid-liquid separation on waste sludge from wastewater treatment plants. The resulting liquid phase serves as the carbon source for the alkaline hydrolysis of the sludge. This application achieves efficient conversion and recycling of waste resources, demonstrating significant technical benefits.

[0060] First, alkaline hydrolysis effectively disrupts the sludge cell structure and extracellular polymers, promoting the dissolution and release of organic matter and significantly increasing the soluble COD (SCOD) concentration, creating favorable conditions for subsequent acid production. The subsequent hydrolysis and acidification stage is conducted under mesophilic, anaerobic conditions, further degrading macromolecular organic matter into volatile fatty acids (VFAs), primarily acetic acid, with a VFA concentration reaching 8.39 g / L. Acetic acid accounts for over 62% of this, and acetic acid is the most readily available and high-quality carbon source during denitrification. Finally, the liquid phase obtained through solid-liquid separation methods such as plate and frame filter press—the "sludge alkaline hydrolysis carbon source"—has a COD concentration exceeding 18,000 mg / L and a B / C ratio as high as 0.42, indicating excellent biodegradability and the ability to completely replace purchased composite carbon sources.

[0061] This application significantly reduces wastewater treatment operating costs. The price of purchased carbon sources is 1960 yuan / ton (COD equivalent of 1 million), while the cost of providing the same COD using the carbon source applied in this application is only 819.61 yuan / ton, a reduction of over 58%. Simultaneously, due to the optimized carbon source composition, the optimal C / N dosage ratio is reduced from the traditional 4:1 to 2.08:1, reducing the carbon source usage per unit of nitrogen removal by nearly half, and lowering the cost per ton of water treated from 0.153 yuan to 0.033 yuan, demonstrating significant economic benefits. Furthermore, this process achieves a 16.19% reduction in sludge volume; treating 1 ton of sludge with 80% moisture content reduces the production of oven-dried sludge, significantly lowering off-site disposal costs. Taking a water plant producing 60,000 tons of wet sludge annually as an example, the annual savings in disposal costs exceed 720,000 yuan, resulting in substantial overall benefits.

[0062] In terms of system operation, the carbon source in this application can be rapidly utilized in the anoxic section, with SCOD essentially depleted within 2 hours, avoiding residual carbon source affecting effluent COD. After subsequent aerobic treatment, the effluent TN can reach Class A or Class IV surface water standards, with a total nitrogen removal rate exceeding 70%, and the operation is stable and reliable. This solution also has good engineering promotion value, as it can achieve alkaline hydrolysis function by modifying existing sludge storage tanks without requiring large-scale additional land occupation. The pilot-scale device has a high degree of integration and is suitable for water plants of different sizes. Overall, this technology realizes a circular economy model of "treating waste with waste and turning waste into treasure," which not only reduces operating costs and environmental burden but also promotes the transformation and upgrading of wastewater treatment plants towards green, low-carbon, and resource self-sufficiency.

[0063] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0064] Example 1 This embodiment provides a method for preparing a carbon source for sludge alkaline hydrolysis, specifically including the following steps: Conditioning: Add water to the waste sludge from the sewage treatment plant and stir evenly to obtain a sludge slurry with a solid content of 8%; Alkaline hydrolysis was performed by adding sodium hydroxide to the sludge at a concentration of 0.1 mol / L, followed by a reaction at 25°C for 60 minutes to obtain an alkaline hydrolysate. Hydrolysis and acidification: The alkaline hydrolysate was placed at (35±2)℃ and a stirring speed of 48 rpm, and the pH of the slurry was adjusted to 10±0.2, and the hydraulic retention time (SRT) was set to 10 days to obtain the hydrolyzed and acidified slurry. The hydrolyzed acidified slurry is filtered by pressure, and the resulting liquid phase is the carbon source for the alkaline hydrolysis of sludge.

[0065] The sludge alkaline hydrolysis carbon source described in this embodiment has a COD of 18960 mg / L and a B / C ratio of 0.42, exhibiting high biodegradability and possessing the attributes of being an external carbon source for wastewater treatment systems.

[0066] Example 2 This embodiment provides a method for preparing a carbon source for sludge alkaline hydrolysis. The only difference from Embodiment 1 is that the alkaline hydrolysis step is carried out at a temperature of 70°C, the pH is adjusted to 12, and the thermal alkaline hydrolysis time is 2 h.

[0067] In this embodiment, after alkaline hydrolysis, the average SCOD in the sludge reached 31102.58 mg / L; after hydrolysis, acidification, and solid-liquid separation, the SCOD of the resulting filtrate reached 28284.52 mg / L; the average VFA concentration was 8.39 g / L, with acetic acid being the most abundant organic acid, accounting for 62.10%; the average concentrations of TN, TP, and ammonia nitrogen reached 2101.82, 230.36, and 459.25 mg / L, respectively; and the degradation rates of TSS and VSS were 28.70% and 48.21%, respectively. The cost-benefit analysis of this embodiment is shown in Table 1.

[0068] Table 1 Cost-benefit analysis of sludge thermal alkaline hydrolysis + hydrolysis acidification project

[0069] According to Table 1, when the sludge treatment volume is 100 m³ with a moisture content of 80%, 3 At a rate of / d, the net benefit of acid production from anaerobic fermentation of sludge is 81.9 yuan / m³. 3 The annual net income is 2.989 million yuan.

[0070] Example 3 This embodiment provides a method for preparing a carbon source for sludge alkaline hydrolysis. The only difference from Embodiment 1 is that sodium hydroxide is added to the sludge slurry at a concentration of 0.15 mol / L in the alkaline hydrolysis step, followed by a reaction at 50°C for 60 min.

[0071] Test Example 1 The changes in SCOD, BOD5, TN, NH3-N, TP, and phosphate of the sludge alkaline hydrolysis carbon sources prepared in Examples 1 and 3 above were detected on day 0, day 7, and day 14 after preparation. The detection items and methods are shown in Table 2, and the detection results are shown in Table 3.

[0072] Table 2 Test Items and Methods

[0073] Table 3. Changes in the properties of carbon sources from sludge alkaline hydrolysis over long-term storage.

[0074] Based on the data in Table 3, draw... Figure 1-7 Analysis showed that the carbon sources prepared in Examples 1 and 3 had high SCOD and BOD5 values, with BOD5 / SCOD values ​​≥0.38, indicating good biodegradability. Based on comprehensive analysis of these indicators, it is recommended that the carbon source be stored for approximately 7 days.

[0075] (1) such as Figure 1As shown, the SCOD degradation rate of the room-temperature alkaline hydrolysis carbon source during a 14-day storage period (17.30%) was significantly higher than that of the high-temperature alkaline hydrolysis carbon source (4.33%). This indicates that the high-temperature carbon source has better SCOD stability. Based on the degradation rate analysis, it is recommended that the storage time for room-temperature carbon sources should not exceed 7 days, and for high-temperature carbon sources, it should not exceed 14 days.

[0076] (2) According to Figure 2 It can be seen that the BOD5 value of the carbon source from room temperature alkaline hydrolysis continuously decreased from day 0 to day 14, with an overall change rate of 2.57%, showing relatively little decay. The change range from 0 to 7 days was slightly lower than that from 7 to 14 days, indicating that the BOD5 composition was relatively stable. Similarly, the BOD5 value of the carbon source from high temperature alkaline hydrolysis continuously decreased from day 0 to day 14, with an overall change rate of 3.70%, showing relatively little decay. Furthermore, the change range of the carbon source from high temperature alkaline hydrolysis filtrate from 0 to 7 days was slightly higher than that from 7 to 14 days, indicating that the BOD5 composition was also relatively stable.

[0077] (3) According to Figure 3 It can be seen that the BOD5 / SCOD values ​​of both ambient and high-temperature alkaline hydrolysis carbon sources show a trend of first decreasing and then increasing, with a relatively high BOD5 / SCOD on day 14. The BOD5 / SCOD of the ambient temperature carbon source even reaches as high as 0.4948 on day 14, indicating good biodegradability. The higher BOD5 / SCOD of the ambient temperature alkaline hydrolysis carbon source compared to the high-temperature alkaline hydrolysis carbon source suggests that the ambient temperature alkaline hydrolysis carbon source is more likely to be used as an auxiliary carbon source in wastewater treatment systems.

[0078] (4) According to Figure 4 It can be seen that from 0 to 14 days, the TN value gradually decreased, and the TN (room temperature alkaline hydrolysis carbon source) decay rate was less than the TN (high temperature alkaline hydrolysis carbon source) decay rate. The TN (room temperature alkaline hydrolysis carbon source) decay amount of 135 mg / L was less than the TN (high temperature alkaline hydrolysis carbon source) decay amount of 155 mg / L. Among them, the TN of the high temperature carbon source was 380 mg / L on the 14th day, with a decrease of 28.97%, which is of positive significance for the possibility of the sludge alkaline hydrolysis filtrate having the potential to be an auxiliary carbon source. Overall, the C / N ratio of high-temperature alkaline carbon sources (change from 0 to 7 to 14 days: 51.77 → 55.28 → 69.73) is greater than that of normal-temperature alkaline hydrolysis carbon sources (change from 0 to 7 to 14 days: 27.69 → 30.67 → 28.71), indicating a more significant increasing trend in the C / N ratio of high-temperature carbon sources. If the TN introduced by sludge alkaline hydrolysis is considered at a C / N ratio of 5:1, then the effective SCOD of high-temperature alkaline hydrolysis carbon sources changes from 0 to 7 to 14 days: 25025 mg / L → 24740 mg / L → 24600 mg / L, while the effective SCOD of low-temperature alkaline hydrolysis carbon sources changes from 0 to 7 to 14 days: 15160 mg / L → 15400 mg / L → 12635 mg / L. The decrease in effective SCOD of high-temperature carbon sources is smaller and more stable, suggesting that the decrease in SCOD may be more due to the degradation of organic nitrogen.

[0079] (5) According to Figure 5 It can be seen that NH3-N showed a trend of first decreasing and then increasing from 0 to 14 days, and NH3-N (room temperature alkaline hydrolysis carbon source) > NH3-N (high temperature alkaline hydrolysis carbon source). This may be because the room temperature alkaline hydrolysis carbon source originally contained a high amount of NH3-N and TN. With the longer the storage time, some TN may also be converted into NH3-N. Both the room temperature alkaline hydrolysis carbon source and the high temperature alkaline hydrolysis carbon source showed a large decrease in NH3-N on the 7th day. This may be related to the cycle of TN conversion into NH3-N and NH3-N dissipation from the carbon source. Therefore, it is considered to set the storage period of the carbon source to no more than 7 days.

[0080] (6) According to Figure 6 It can be seen that, from the TP changes over 0-14 days, the TP value of the room-temperature alkaline hydrolysis carbon source first increased and then decreased, while the TP value of the high-temperature alkaline hydrolysis carbon source gradually decreased. The largest decreases were observed on day 14 for both the room-temperature and high-temperature alkaline hydrolysis carbon sources, at 15.50% and 15.25% respectively. The room-temperature carbon source had the lowest TP value on day 14, at 545 mg / L. The changes in TP may also be due to the degradation of organophosphorus compounds.

[0081] (6) According to Figure 7 It can be seen that from 0 to 14 days, the phosphate content of the room temperature alkaline hydrolysis carbon source first decreased and then remained unchanged, while the phosphate content of the high temperature alkaline hydrolysis carbon source decreased continuously. The decrease of the high temperature alkaline hydrolysis carbon source was the largest on the 14th day. After 14 days, the phosphate content of the room temperature alkaline hydrolysis carbon source was the lowest, at 23.8 mg / L. The change in phosphate content may be due to the precipitation of phosphate and other substances.

[0082] Based on a comprehensive analysis of the various indicators of the carbon source in Examples 1 and 3, it is recommended that the carbon source be placed for about 7 days. After standing for 14 days, both COD and BOD decreased.

[0083] Example 4: Denitrification Experiment Using Carbon Source This embodiment provides a comparative experiment on the denitrification performance of a carbon source, specifically including: selecting A 2 The aerobic end-of-pipe mixed liquor in the / O process has the following concentrations: total nitrogen 4 mg / L, SCOD 36 mg / L, NH3-N 0.6 mg / L, TP 1.9 mg / L, and MLSS 9600 mg / L (water plant test values). Objective: To increase the total nitrogen (TN) of the aerobic terminal mixed liquor to 30 mg / L by adding potassium nitrate; the carbon source should be provided at a C / N ratio of 5:1. The denitrification experiment using the carbon source will be set up in five groups as follows: a. Blank: SCOD was 36 mg / L, NH3-N was 3.5 mg / L, and TP was 1.9 mg / L; b. Composite Carbon Source: This embodiment uses a composite carbon source with a specific ratio and an SCOD of 1,000,000 mg / L. This composite carbon source can be selected from ethylene glycol, glycerol, molasses, fermentation broth, etc., as described in the instructions. This embodiment specifically uses a mixture of waste glycerol (derived from chemical by-product glycerol, COD approximately 1,200,000 mg / L) and waste molasses (derived from sugar factory waste liquid, COD approximately 800,000 mg / L). The SCOD value may vary depending on the source and ratio of the raw materials. c. Sodium acetate: SCOD = 165000 mg / L; d. Carbon source at room temperature (Example 1): SCOD=18960mg / L, TN=1440mg / L, NH4-N=250mg / L, TP=668mg / L, active phosphorus=85mg / L; e. High-temperature carbon source: Prepared according to the alkaline hydrolysis and hydrolysis-acidification method in Example 2 (70℃, pH 12, alkaline hydrolysis for 2 h; 35℃, pH 10, hydrolysis-acidification for 10 h), and the final liquid product was obtained by centrifugation. The measured parameters of this batch of carbon source are: SCOD=30850 mg / L, TN=2125 mg / L, NH4+ + -N=215mg / L, TP=944mg / L, active phosphorus=101mg / L; Comparing the high-temperature carbon source in this example with that in Example 2, it can be seen that centrifugation is more conducive to the retention of organic matter in the high-temperature carbon source than pressure filtration. Therefore, the SCOD of the high-temperature carbon source in this example is higher than that in Example 2. The specific experimental method included: adding the following carbon source to 1.5L of aerobic terminal mixture: [5×(30-10)-36]×1.5=96mg; the calculated carbon source addition volumes for the five groups of carbon source denitrification experiments are as follows: a. Blank: Carbon source dosage 0 mL; b. The amount of composite carbon source added = 96 / 1000000 = 0.096 mL; c. Sodium acetate dosage = 96 / 165000 = 0.582 mL; d. Carbon source dosage at room temperature = 96 / 18960 = 5.063 mL; e. High-temperature carbon source dosage = 96 / 30850 = 3.112 mL.

[0084] The specific experimental steps are as follows: (1) Take 7.5L of the sludge-water mixture at the end of the aerobic tank, take 5 beakers, fill each beaker with 1500 mL of the mixture and label them. The first beaker is the blank control group without any carbon source, the second is the experimental group of composite carbon source effect, the third is the experimental group of sodium acetate effect, the fourth is the experimental group of sludge room temperature alkaline hydrolysis filtrate effect, and the fifth is the experimental group of sludge high temperature alkaline hydrolysis filtrate effect. These are respectively recorded as: blank experiment, composite carbon source experiment, sodium acetate experiment, room temperature carbon source experiment, and high temperature carbon source experiment. (2) Stir thoroughly for 120 min; take samples every 60 min to measure pH, dissolved chemical oxygen demand (SCOD), total nitrogen (TN), and ammonia nitrogen (NH3-N), and record the results.

[0085] (3) The experimental data analysis of denitrification with multiple carbon sources as auxiliary carbon sources is as follows: A. The amounts of SCOD, TN, TP, and NH3-N carried by the carbon source in the sludge alkaline hydrolysis filtrate are as follows: For carbon sources in sludge alkaline hydrolysis at room temperature: The calculated SCOD(0h) value is: (5.063*18960) / 1505.063=64mg / L (ignoring the influence of the SCOD of 36mg / L of the aerobic end mixture itself); The calculated value of TN(0h) is: (5.063*1440+30*1500) / 1505.063=35mg / L; The calculated value of NH3-N(0h) is: (5.063*215+3.5*1500) / 1505.063=4.2mg / L; The calculated value of TP(0h) is: (5.063*668+1.9*1500) / 1505.063=4.1mg / L; For carbon sources in high-temperature alkaline hydrolysis of sludge: The calculated SCOD(0h) value is: (3.112*30850) / 1503.112=64mg / L (ignoring the influence of the SCOD of 36mg / L of the aerobic end mixture itself); The calculated value of TN(0h) is: (3.112*2125+30*1500) / 1503.112=34mg / L; The calculated value of NH3-N(0h) is: (3.112*215+3.5*1500) / 1503.112=3.9mg / L; The calculated value of TP(0h) is: (3.112*944+1.9*1500) / 1503.112=3.9mg / L.

[0086] B. Ignoring the effect of the SCOD of the aerobic terminal mixture (36 mg / L), the actual C / N ratio after 2 hours of carbon source addition is: ②The C / N ratio of the composite carbon source is: [64-(34-36)] / (30-10) = 3.3; ③ The C / N ratio of the carbon source added to sodium acetate is = [64-(36-36)] / (30-11) = 3.4; ④ The C / N ratio of the carbon source added at room temperature is = [64-(47-36)] / (35-17) = 2.94; ⑤ The C / N ratio of the carbon source added at high temperature is = [64-(43-36)] / (34-15) = 3.

[0087] The water composition was measured before, during, and after the five experiments, and the results are shown in Table 4.

[0088] Table 4

[0089] Specifically, plotted based on the data in Table 4. Figure 8-11 : (1) According to Figure 8 It can be seen that without the addition of any external carbon source, the effluent TN can be reduced from 30 mg / L to 21 mg / L. The nitrification liquid itself can remove 9 mg / L of TN, but it still cannot meet the effluent discharge standard, so an external carbon source is needed to ensure that the effluent meets the standard. Through experimental comparison and analysis of the denitrification effect of the above-mentioned carbon sources, except for the group with TN added at room temperature (17 mg / L), the effluent TN of the other four groups of experiments all meet the Class IV standard of the "Surface Water Environmental Quality Standard" (GB 3838-2002) with TN≤15 mg / L.

[0090] From the perspective of TN removal rate, the TN removal rate (1h) > TN removal rate (2h). The TN removal rate decreases after 2h. The carbon source required for the anoxic reaction generally comes from three sources: influent BOD, BOD released by microbial endogenous reactions, and external carbon source. It is speculated that this is because the easily biodegradable organic matrix is ​​gradually consumed, and microorganisms turn to utilize relatively difficult-to-utilize, particulate, and complex slowly degradable organic matrix, further reducing the denitrification rate. The degree to which the above carbon sources are easily utilized by denitrifying bacteria in 0-1h is: sodium acetate > composite carbon source > room temperature carbon source > high temperature carbon source. The main reasons are as follows: ① Sodium acetate is more easily utilized by denitrifying bacteria than composite carbon source; ② According to the test report of Shandong Shengyang Testing Co., Ltd., the B / C ratio of room temperature carbon source (0.42) > that of high temperature carbon source (0.39). Therefore, the TN removal rate of adding room temperature carbon source is better than that of high temperature carbon source, which is consistent with the results of the test report. Analyzing the TN removal efficiency, at 1-2 hours: composite carbon source > high-temperature carbon source > sodium acetate > room-temperature carbon source. This suggests that at this time, the relatively readily usable substances in the carbon sources extracted from the nitrification liquor and sludge have been consumed. This indicates that among the remaining SCOD components, the high-temperature carbon source contains more readily usable components than sodium acetate and room-temperature carbon sources, but sodium acetate is more effective than the room-temperature carbon source. Overall, the TN removal efficiency at 0-2 hours is: composite carbon source > sodium acetate > high-temperature carbon source > room-temperature carbon source. From a denitrification perspective, the carbon sources obtained from sludge alkaline hydrolysis are slightly less effective than sodium acetate and composite carbon sources, but the high-temperature carbon source shows a more significant advantage over the room-temperature carbon source.

[0091] (2) By Figure 9 Analysis shows that the SCOD removal rate (1h) > SCOD removal rate (2h), presumably because the carbon source that is easily utilized by microorganisms is relatively abundant in the initial reaction to 1h. The SCOD removal rates of the five groups of experiments are: sodium acetate > composite carbon source > ambient temperature carbon source > high temperature carbon source; the SCOD removal efficiency is: composite carbon source > sodium acetate > high temperature carbon source > ambient temperature carbon source. Except for the blank group, the SCOD (29mg / L) of the effluent from the five groups of experiments is ≤30mg / L, which does not meet the Class IV standard requirements of the "Surface Water Environmental Quality Standard" (GB 3838-2002).

[0092] From the perspective of SCOD, ignoring the influence of the SCOD of 36 mg / L of the aerobic end mixed liquor itself, the SCOD of the experimental group with added composite carbon source and the experimental group with added sodium acetate were ≤36 mg / L in 0-2 h. This shows that the composite carbon source and sodium acetate were completely utilized by microorganisms, while the carbon source of the sludge filtrate at room temperature and high temperature was not completely depleted by denitrification.

[0093] (3) By Figure 10Analysis shows that the theoretical TP removal rate was 68.29%~73.68% during the 0-2h period. Except for the composite carbon source (0.5mg / L) ≤0.5mg / L, it meets the requirements of Class IV standard of "Surface Water Environmental Quality Standard" (GB 3838-2002). The blank, sodium acetate, room temperature carbon source, and high temperature carbon source groups did not meet the standard requirements. It is recommended to add a phosphate removal step to the subsequent sludge thermal alkaline hydrolysis carbon source. The phenomenon of anaerobic phosphorus absorption is obvious, especially for high and low temperature carbon sources. The anaerobic phosphorus absorption phenomenon is very significant. The high temperature carbon source decreased from 4.1 to 1.3mg / L, and the low temperature carbon source decreased from 3.9 to 1.2mg / L.

[0094] (4) By Figure 11 Analysis shows that the pH of the group with sodium acetate and compound carbon source first decreased and then increased, while the pH of the group with sludge alkaline carbon source increased. Under similar initial pH conditions, the pH of the five groups increased during the 2-hour denitrification process. This indicates that during this stage, denitrifying bacteria absorb a large amount of easily degradable organic matter to reduce nitrates, carry out denitrification, and produce alkalinity, which is manifested as a rapid increase in pH.

[0095] In summary, based on the analysis of effluent compliance, denitrification rate, biodegradability, and removal effect, the carbon source of sludge alkaline hydrolysis filtrate is recommended as an auxiliary carbon source to be added to the anoxic tank.

[0096] For wastewater with a low carbon-to-nitrogen ratio, the denitrification process in general engineering is carried out in an anaerobic + anoxic environment for 1 + 3 hours. A denitrification time of 2 hours is insufficient / lacking in the hydrolysis of the anaerobic zone, and is not enough to verify the performance of the sludge carbon source. Because the sludge carbon source contains many biomass macromolecules such as proteins, polysaccharides, and lipids, which need to be anaerobic hydrolyzed into rbCOD or VFA before they can be utilized by anoxic bacteria, the denitrification time can be extended to 3 hours.

[0097] Example 5: Denitrification + Aeration Experiment with Auxiliary Carbon Source.

[0098] This embodiment investigates the effects of carbon source in high-temperature and ambient-temperature sludge thermal alkaline hydrolysis filtrate on effluent COD, TN, and NH3-N by adjusting the carbon source dosage and carbon-nitrogen ratio. Based on the 2-hour denitrification experiment in Example 3, a 4-hour aeration experiment was conducted using an oxygenation pump. Specifically, the following steps were taken: sludge-water mixture from the end of the aerobic tank was collected, and 1500 mL of the mixture was added to five beakers, each labeled. High-temperature and ambient-temperature sludge alkaline hydrolysis filtrate were added, considering C / N ratios of 5:1, 4:1, 3:1, and 2:1, as well as a blank control group without any added carbon source. Using a rotor to stir, samples were taken every 60 minutes under anoxic conditions to measure pH, chemical oxygen demand (SCOD), total nitrogen (TN), and ammonia nitrogen (NH3-N). After 2 hours, an oxygen pump was added to the beaker for aeration to control the dissolved oxygen (DO) concentration in the water to be maintained at 2.0-4.0 mg / L so that the dissolved oxygen in the water reaches or is close to saturation. Samples were taken every 60 minutes for 4 consecutive hours, and the changes in various indicators were recorded.

[0099] (1) Experimental data of denitrification + aeration using the sludge high-temperature alkaline hydrolysis filtrate prepared by the method of Example 3 as an auxiliary carbon source: The final mixed liquor of the aerobic tank after TN adjustment had the following concentrations: total nitrogen 30 mg / L, SCOD 36 mg / L, and NH3-N 3.5 mg / L. High-temperature carbon source C / N = 5:1. Carbon source dosage: [5 × (30-10) - 36] × 1.5 / 30850 = 3.1 ml; High-temperature carbon source C / N = 4:1. Carbon source dosage: [4 × (30-10) - 36] × 1.5 / 30850 = 2.1 ml; High-temperature carbon source C / N = 3:1. Carbon source dosage: [3 × (30-10) - 36] × 1.5 / 30850 = 1.2 ml; High-temperature carbon source C / N=2:1 Carbon source dosage: [2×(30-10)-36]×1.5 / 30850=0.2ml.

[0100] When a high-temperature carbon source is added with a C / N ratio of 5:1: The calculated SCOD value of the mixed solution is: (3.1*30850) / 1503.1=64mg / L (ignoring the influence of the SCOD of the aerobic end mixed solution itself of 36mg / L). The calculated TN value for the mixed solution is: (3.1*2125+30*1500) / 1503.1=34mg / L; The calculated value of NH3-N in the mixed solution is: (3.1*215+3.5*1500) / 1503.1=3.9mg / L; The calculated TP value for the mixed solution is: (3.1*944+1.9*1500) / 1503.1=3.9mg / L; Ignoring the influence of the SCOD of 36 mg / L in the aerobic end mixture itself, the actual C / N ratio after 2 hours of carbon source addition is: actual C / N ratio: [64-(43-36)] / (34-15) = 3; When a high-temperature carbon source is added with a C / N ratio of 4:1: The calculated SCOD value of the mixed solution is: (2.1*30850) / 1502.1=44mg / L (ignoring the influence of the SCOD of the aerobic end mixed solution itself of 36mg / L). The calculated TN value for the mixed solution is: (2.1*2125+30*1500) / 1502.1=33mg / L; The calculated value of NH3-N in the mixed solution is: (2.1*215+3.5*1500) / 1502.1=3.8mg / L; The calculated TP value for the mixed solution is: (2.1*944+1.9*1500) / 1502.1=3.2mg / L; Ignoring the influence of the SCOD of 36 mg / L in the aerobic end mixture, the C / N ratio after 2 hours of actual carbon source addition is: Actual C / N ratio: [44-(41-36)] / (33-19) = 2.79; When a high-temperature carbon source is added with a C / N ratio of 3:1: The calculated SCOD value of the mixed solution is: (1.2*30850) / 1501.2=25mg / L (ignoring the influence of the SCOD of the aerobic end mixed solution itself of 36mg / L). The calculated TN value for the mixed solution is: (1.2*2125+30*1500) / 1501.2=32mg / L; The calculated value of NH3-N in the mixed solution is: (1.2*215+3.5*1500) / 1501.2=3.7mg / L; The calculated TP value for the mixed solution is: (1.2*944+1.9*1500) / 1501.2=2.7mg / L; Ignoring the influence of the SCOD of 36 mg / L in the aerobic end mixture, the C / N ratio of the actual carbon source added for 2 hours is: Actual C / N ratio: [25-(40-36)] / (32-20) = 1.75.

[0101] When a high-temperature carbon source is added with a C / N ratio of 2:1: The calculated SCOD value of the mixed solution is: (0.2*30850) / 1500.2=4mg / L (ignoring the influence of the SCOD of the aerobic end mixed solution itself of 36mg / L). The calculated TN value for the mixed solution is: (0.2*2125+30*1500) / 1500.2=30mg / L; The calculated value of NH3-N in the mixed solution is: (0.2*215+3.5*1500) / 1500.2=3.5mg / L; The calculated TP value for the mixed solution is: (0.2*944+1.9*1500) / 1500.2=2mg / L; Ignoring the effect of the SCOD of the aerobic end-stage mixture (36 mg / L), the actual C / N ratio after 2 hours of carbon source addition is: Actual C / N ratio added: [4-(30-36) / (30-20)=1.

[0102] The experimental data for high-temperature carbon source denitrification + aeration are shown in Table 5: Table 5

[0103] (2) Experimental data on denitrification + aeration using sludge room temperature alkaline hydrolysis filtrate (Example 1) as an auxiliary carbon source: At room temperature, the carbon source C / N ratio is 5:1. The carbon source dosage is: [5 × (30-10) - 36] × 1.5 / 18960 = 5.1 ml; At room temperature, the carbon source C / N ratio is 4:1. The carbon source dosage is: [4 × (30-10) - 36] × 1.5 / 18960 = 3.5 ml; At room temperature, the carbon source C / N ratio is 3:1. The carbon source dosage is: [3×(30-10)-36]×1.5 / 18960=1.9ml; At room temperature, the carbon source C / N ratio is 2:1. The amount of carbon source added is: [2×(30-10)-36]×1.5 / 18960=0.3ml; When the carbon source at room temperature has a C / N ratio of 5:1: The calculated SCOD value of the mixed solution is: (5.1*18960) / 1505.1=64mg / L (ignoring the influence of the SCOD of the aerobic end mixed solution itself of 36mg / L). The calculated TN value for the mixed solution is: (5.1*1440+30*1500) / 1505.1=35mg / L; The calculated value of NH3-N in the mixed solution is: (5.1*215+3.5*1500) / 1505.1=4.2mg / L; The calculated TP value for the mixed solution is: (5.1*668+1.9*1500) / 1505.1=4.1mg / L; Ignoring the effect of the SCOD of the aerobic end-stage mixed solution (36 mg / L), the actual C / N ratio after 2 hours of carbon source addition is: Actual C / N ratio added: [64-(47-36)] / (35-17) = 2.94.

[0104] When the carbon source at room temperature has a C / N ratio of 4:1: The calculated SCOD value for the mixed solution is: (3.5*18960) / 1503.5=44mg / L; The calculated TN value for the mixed solution is: (3.5*1440+30*1500) / 1503.5=33mg / L; The calculated value of NH3-N in the mixed solution is: (3.5*215+3.5*1500) / 1503.5=4mg / L; The calculated TP value for the mixed solution is: (3.5*668+1.9*1500) / 1503.5=3.5mg / L; Ignoring the effect of the SCOD of the aerobic end-stage mixed solution (36 mg / L), the actual C / N ratio after 2 hours of carbon source addition is: Actual C / N ratio added: [44-(39-36)] / (33-17)=2.56.

[0105] When the carbon source at room temperature has a C / N ratio of 3:1: The calculated SCOD value for the mixed solution is: (1.9 * 18960) / 1501.9 = 24 mg / L; The calculated TN value for the mixed solution is: (1.9*1440+30*1500) / 1501.9=32mg / L; The calculated value of NH3-N in the mixed solution is: (1.9*215+3.5*1500) / 1501.9=3.8mg / L; The calculated TP value for the mixed solution is: (1.9*668+1.9*1500) / 1501.9=2.7mg / L; Ignoring the effect of the SCOD of the aerobic end-stage mixed solution (36 mg / L), the actual C / N ratio after 2 hours of carbon source addition is: Actual C / N ratio added: [24-(35-36)] / (32-20)=2.08.

[0106] When the carbon source at room temperature has a C / N ratio of 2:1: The calculated SCOD value for the mixed solution is: (0.3*18960) / 1500.3 = 4 mg / L; The calculated TN value for the mixed solution is: (0.3*1440+30*1500) / 1500.3=30mg / L; The calculated value of NH3-N in the mixed solution is: (0.3*215+3.5*1500) / 1500.3=3.5mg / L; The calculated TP value for the mixed solution is: (0.3*668+1.9*1500) / 1500.3=2mg / L; Ignoring the effect of the SCOD of the aerobic end-stage mixed solution (36 mg / L), the actual C / N ratio after 2 hours of carbon source addition is: Actual C / N ratio added: [4-(28-36)] / (30-21)=1.33.

[0107] The experimental data for room temperature carbon source denitrification + aeration are shown in Table 6: Table 6

[0108] (3) Analysis of experimental data on denitrification + aeration using high-temperature and room-temperature alkaline hydrolysis filtrate of sludge as auxiliary carbon source; analyze Figure 12 and Figure 13 The SCOD data and charts show that, considering both the change in amount and removal rate, the SCOD removal efficiency gradually decreases with decreasing C / N ratio, regardless of whether the carbon source is at room temperature or high temperature. Except for the effluent SCOD (31 mg / L) with a C / N ratio of 5:1 using a room temperature carbon source, the effluent SCOD of other C / N ratios treated with sludge thermal alkaline hydrolysis carbon sources all meet the Class IV effluent standard. The SCOD decreases more significantly during the anoxic stage and slightly during the aeration stage, indicating that a large amount of carbon source is consumed during the anoxic denitrification stage. The addition of carbon source to the sludge alkaline hydrolysis filtrate significantly improves the SCOD removal rate.

[0109] analyze Figure 14 and Figure 15 TN Removal Efficiency: Data shows that for both high-temperature and ambient-temperature carbon sources, the trend is that increasing the C / N ratio of the added carbon source leads to an increase in TN removal rate. Without an external carbon source, the control group achieved only 30% TN removal within 2 hours; however, under sufficient carbon source conditions (high-temperature carbon source with a C / N ratio of 5:1), the TN removal rate reached 55.88% within 2 hours. This indicates that the addition of sludge alkaline hydrolysis carbon source increased the denitrification rate. With increasing C / N ratio, denitrification became more thorough, resulting in better TN removal. Specifically, when the ambient-temperature carbon source C / N ratio decreased to 3:1, the TN of the effluent after nitrification and denitrification met the effluent standard; when the C / N ratio was 2:1, it did not meet the standard. Furthermore, the 2-hour effluent showed that the added ambient-temperature alkaline hydrolysis carbon source was completely consumed. With a high-temperature carbon source, the effluent with a C / N ratio of 3:1 did not meet the effluent standard, while other C / N ratios met the standard. TN decreased in both the anoxic and aeration stages. The removal rate was higher in the anoxic stage, and TN removal in 2 hours of anoxic conditions could reach more than 50% of the total TN removal in the entire 6 hours of anoxic + aeration process. TN reduction could also be achieved in the aeration stage, which may indicate simultaneous nitrification and denitrification.

[0110] The TN removal rate of the high-temperature carbon source with a C / N ratio of 5:1 was 64.71%, and that of the high-temperature carbon source with a C / N ratio of 4:1 was 57.58%. The TN removal rate of the room-temperature carbon source with a C / N ratio of 5:1 was 65.71%, and that of the high-temperature carbon source with a C / N ratio of 4:1 was 60.61%. The TN removal rate of the room-temperature carbon source was slightly higher than that of the high-temperature carbon source. This may be because the B / C ratio of the room-temperature carbon source (0.42) is greater than that of the high-temperature carbon source (0.39), indicating that the room-temperature carbon source has better biodegradability than the high-temperature carbon source. Therefore, when adding the same SCOD equivalent of carbon source, the room-temperature carbon source is more effective than the high-temperature carbon source.

[0111] In summary, based on the experimental results obtained so far, the sludge alkaline hydrolysis carbon source is feasible as an external carbon source. Comparing high-temperature carbon sources and room-temperature carbon sources, the room-temperature alkaline hydrolysis carbon source with an actual C / N ratio of 2.08:1 is selected for use.

[0112] Meanwhile, economic considerations must also be taken into account: a. Sludge room temperature alkaline hydrolysis filtrate: Using a theoretical dosage of room temperature sludge alkaline hydrolysis filtrate C / N = 2.08:1, with a sludge solids content of 8%, NaOH dosage of 0.1 mol / L, reaction conditions of 25℃ and 60 min, the cost of producing 1 kg of SCOD from the sludge room temperature alkaline hydrolysis filtrate is 1.0655 yuan / kg. In 2 hours, the sludge room temperature alkaline hydrolysis filtrate actually consumes 25 mg / L of SCOD to remove 12 mg / L of TN. The actual C / N ratio is 2.08. Removing 1 kg of TN requires 2.08 kg of SCOD, and the cost is: 2.08 * 1.0655 = 2.21624 yuan; b. Cost per ton of water treated: The TN concentration in the wastewater is 30 mg / L. According to the Class IV effluent standard, the TN concentration is 15 mg / L. Therefore, the amount of TN that needs to be removed from 1 ton of water is 15 g, or 0.015 kg. So the cost per ton of water treated by adding a room temperature carbon source is 0.015 * 2.21624 = 0.0333 yuan.

[0113] Therefore, the filtrate from the alkaline hydrolysis of sludge at room temperature is economical. Considering both effluent compliance and economic efficiency, room temperature carbon source is more advantageous as an external carbon source, and the actual addition ratio of C / N can be 2.08:1.

[0114] analyze Figure 16 and Figure 17NH3-N removal efficiency: Data shows that the NH3-N removal rate of high-temperature carbon sources is 65.79%–69.23%, while that of room-temperature carbon sources is 71.05%–77.14%, indicating similar removal efficiency between room-temperature and high-temperature carbon sources. As shown in the graph, a certain amount of NH3-N is removed in the anoxic zone, originating from the assimilation by denitrifying bacteria, but the removal amount is small. After aeration and entering the aerobic zone, NH3-N begins to degrade rapidly under nitrification. In the above experiments, the effluent from different types and proportions of sludge alkaline hydrolysis filtrate all met the Class A effluent standard. The reduction in NH3-N is mainly related to the nitrification reaction in the aerobic zone, decreasing continuously as nitrification progresses. Different carbon-to-nitrogen ratios and different types of carbon sources have no significant effect on the ammonia nitrogen removal rate in the system.

[0115] analyze Figure 18 and Figure 19 It can be seen that the TP removal rate of high-temperature carbon sources is 81.48%–89.74%, while that of ambient-temperature carbon sources is 75%–90.24%. The removal effects of ambient-temperature and high-temperature carbon sources on TP are quite similar. In the above experiments, the effluent TP of different types and proportions of sludge alkaline hydrolysis filtrate all met the Class IV effluent standard. In the aerobic stage, TP decreased rapidly due to absorption by polyphosphate-accumulating bacteria. Different carbon-to-nitrogen ratios and different types of carbon sources had no significant effect on the TP removal rate within the system.

[0116] analyze Figure 20 and Figure 21 It can be seen that the pH value continuously increases during both the denitrification and aeration stages. The denitrification reaction equation is: 5C (organic C) + 2H2O + 4NO3 → 5CO2 + 2N2 + 4OH- － Denitrification increases alkalinity. Nitrification occurs during the aeration stage; the nitrification reaction is as follows: NH4+ ＋ +2O2→NO3 － +2H ＋ The reaction ⇌ H₂O generates acid and consumes alkalinity. The possible reasons for the continued increase in pH during the aeration stage in this experiment are: 1. Insufficient dissolved oxygen concentration, which inhibited nitrification to some extent; 2. Denitrification was stronger than nitrification, thus increasing alkalinity; 3. Hydrolysis of organic nitrogen in the carbon source: Organic nitrogen hydrolysis produces ammonia nitrogen, which (such as ammonia water) is weakly alkaline, thus increasing the pH during the reaction; 4. Phosphorus uptake during the aerobic stage produces OH⁻, increasing the system pH. In summary, the carbon source in the sludge thermal alkaline hydrolysis filtrate can effectively remove COD and TN from the system, significantly improving COD and TN removal efficiency compared to the control group, and can be considered an effective carbon source.

[0117] Conclusion: Based on the above experimental results, it is recommended to use the sludge alkaline hydrolysis filtrate at room temperature as an auxiliary carbon source. The reaction conditions are: sludge solids content 8%, NaOH dosage 0.1 mol / L, 25℃, 60 min. The optimal conditions are a carbon source addition ratio of 2.08:1 at room temperature. After 2 hours of anoxic treatment, the added SCOD is completely consumed, and the use of sludge alkaline hydrolysis carbon source will not increase the SCOD in the aerobic terminal mixed liquor. After 4 hours of aerobic treatment following anoxic treatment, the TN and SCOD of the treated aerobic terminal mixed liquor both meet the requirements of Class IV discharge standards of the "Surface Water Environmental Quality Standard" (GB 3838-2002) and can be used as a carbon source. The cost of generating 1 kg of SCOD from the sludge alkaline hydrolysis filtrate at room temperature is 1.0655 yuan / kg, and the treatment cost per ton of water (considering an influent TN of 30 mg / L and an effluent discharge standard of 15 mg / L based on Class IV discharge standards) is 0.0333 yuan. This is significantly better than the 0.099 yuan / ton water treatment cost of a purchased composite carbon source under the same dosing conditions (purchased composite carbon source with a COD equivalent of 1 million and a price of 2000 yuan / m³). 3 ).

[0118] Example 6 This embodiment provides a method for preparing a carbon source from sludge alkaline hydrolysis. The only difference from Embodiment 1 is that sludge discharged from the sludge storage tank is directly used as the raw sludge for thermal alkaline hydrolysis. The reaction temperature of the alkaline hydrolysis step is 50℃, the alkali dosage is 0.03 mol / L, and the reaction time is 40, 80, and 120 min, respectively. The obtained carbon source from sludge alkaline hydrolysis is analyzed and measured to examine the COD release. The results are shown in Table 7.

[0119] Table 7. Effect of sludge alkaline hydrolysis at different reaction times

[0120] When the reaction time was 80 min, the release of SCOD reached a maximum of 4740 mg / L, and the release rate of SCOD from sludge thermal alkaline hydrolysis was 31.78%.

[0121] Example 7 This embodiment provides a method for preparing a carbon source from sludge alkaline hydrolysis. The only difference from Example 6 is that the reaction temperature of the alkaline hydrolysis step is selected as 50, 60, and 70℃, the amount of alkali added is 0.03 mol / L, the reaction time is 120 min, and the solid-liquid separation method is centrifugation. The obtained carbon source from sludge alkaline hydrolysis is analyzed and measured. The results are shown in Table 8.

[0122] Table 8

[0123] Note: SCOD0 (20μm) refers to the initial dissolved chemical oxygen demand in the filtrate after filtration through a 20μm filter membrane.

[0124] As shown in the table above, after solid-liquid separation by centrifuge, the SCOD of sludge after thermal alkaline hydrolysis at 50℃ was 22250 mg / L. Under the same experimental conditions, the SCOD of sludge after thermal alkaline hydrolysis separated by filter paper was 15920 mg / L. This indicates that centrifuge facilitates the release of SCOD released after thermal alkaline hydrolysis into the liquid phase. For future engineering applications, mechanical dewatering is recommended for solid-liquid separation. The recovery rate of the filtrate volume after centrifugation was approximately 50%.

[0125] Example 8 This embodiment provides a method for preparing a carbon source from sludge alkaline hydrolysis. The only difference from Example 7 is that the solid content of the sludge in the conditioning step is selected as 8%, 9%, 10%, and 11%, respectively, and the reaction temperature in the alkaline hydrolysis step is 50℃, the alkali dosage is 0.05 mol / L, and the reaction time is 120 min. The obtained carbon source from sludge alkaline hydrolysis is analyzed and measured, and the results are shown in Table 9.

[0126] Table 9

[0127] Example 9 This embodiment provides a wastewater treatment method, the specific process of which is as follows: Figure 22 As shown, including the use of A 2 Wastewater treatment is carried out using the / O process, with the carbon source for wastewater treatment described in Examples 1-3 added to A. 2 The anoxic and aerobic stages of the / O process are controlled with reference to the denitrification and aeration experimental conditions described in Example 5.

[0128] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon source for sludge alkaline hydrolysis, characterized in that, Includes the following steps: (1) Alkali hydrolysis treatment of waste sludge from sewage treatment plants; (2) The sludge after alkaline hydrolysis is subjected to hydrolysis and acidification treatment; (3) The mixture after hydrolysis and acidification is subjected to solid-liquid separation, and the liquid phase is collected as the carbon source for the alkaline hydrolysis of the sludge.

2. The method for preparing the carbon source from sludge alkaline hydrolysis according to claim 1, characterized in that, The alkaline hydrolysis treatment is performed at a temperature of 25-70℃, a pH of 11-12, and a time of 1-2 hours.

3. The method for preparing the carbon source from sludge alkaline hydrolysis according to claim 1, characterized in that, The hydrolysis acidification treatment is carried out at a temperature of 33-37℃, a pH of 9.8-10.2, and a time of 9-11 hours.

4. The method for preparing the carbon source for sludge alkaline hydrolysis according to claim 1, characterized in that, After the hydrolysis and acidification treatment and before solid-liquid separation, struvite precipitation is performed. The pH of the struvite precipitation step is 8.5-9.5, and a magnesium source is added. The magnesium source is at least one of magnesium chloride, magnesium sulfate, or magnesium oxide.

5. The method for preparing the carbon source for sludge alkaline hydrolysis according to claim 1, characterized in that, Before the alkaline hydrolysis treatment, the waste sludge from the wastewater treatment plant is diluted to a total suspended solids concentration of 75-105 g / L.

6. A carbon source for wastewater treatment, characterized in that, This includes sludge alkaline hydrolysis carbon sources prepared by the preparation method described in any one of claims 1 to 5.

7. The carbon source for wastewater treatment according to claim 6, characterized in that, The carbon source used for wastewater treatment meets at least one of the following performance indicators: (a) B / C ratio ≥ 0.4; (b) The content of volatile fatty acids is ≥5g / L, of which acetic acid accounts for not less than 60%; (c) When used in the A² / O process, the carbon-to-nitrogen ratio is ≤2.2:1 and the total nitrogen removal rate is ≥70%; (d) Chemical oxygen demand is 15,000-35,000 mg / L.

8. The carbon source for wastewater treatment according to claim 6, characterized in that, It also includes a composite carbon source, which is selected from at least one of ethylene glycol, glycerol, molasses and fermentation broth.

9. A method for wastewater treatment, characterized in that, Wastewater treatment is carried out using the A² / O process, and the carbon source for wastewater treatment as described in any one of claims 6 to 8 is added to the anoxic section of the A² / O process.

10. The wastewater treatment method according to claim 9, characterized in that, The carbon-to-nitrogen ratio in the anoxic section is 2.0-5.0:1, the hydraulic retention time in the anoxic section is 100-180 min, and the hydraulic retention time in the aerobic section is 180-280 min.

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