Application of kitchen waste resource treatment water as carbon source in sewage treatment plant

Abstract

This invention discloses a resource-based treatment process for kitchen waste wastewater, belonging to the technical field of kitchen waste resource utilization. The treatment process provided by this invention includes: adding a ferrate composite oxidant to the kitchen waste wastewater for simultaneous alkali adjustment and oxidation; adding bio-iron or chemically produced polyferric sulfate for reaction; and then adding denitrifying bacteria for nitrogen removal. The treatment process provided by this invention has simple operation steps and low treatment costs, representing a resource-based treatment process for kitchen waste that turns waste into treasure. After treatment, the kitchen waste wastewater has a COD ≥ 50000 mg / L, significantly reduced total nitrogen and total phosphorus content, increased content of small-molecule organic matter, and increased biodegradability, meeting the carbon source requirements of wastewater treatment plants and can be used as a carbon source for wastewater treatment plant carbon replenishment.

Description

Technical Field

[0001] This invention belongs to the field of food waste resource utilization technology, specifically relating to a food waste wastewater resource treatment process. Background Technology

[0002] Food waste refers to the waste generated in daily life, as well as from food processing, catering services, and institutional meal services. It includes waste cooking oil and kitchen waste. Waste cooking oil refers to inedible animal and vegetable oils and various oil-water mixtures, while kitchen waste refers to food scraps and food processing waste, primarily consisting of solid residues. Compared to other types of waste, food waste is more prone to fermentation, spoilage, and rotting, producing large amounts of toxins. If not treated promptly, it not only affects urban environmental sanitation but also spreads diseases and harms human health.

[0003] Food waste has a unique composition, characterized by high levels of moisture, organic matter, grease, and salt. Its moisture content is typically between 80-90%, resulting in substantial wastewater generation during its subsequent treatment. This wastewater is a highly concentrated organic wastewater, rich in nutrients such as nitrogen, phosphorus, potassium, and amino acids. It exhibits good biodegradability, with COD concentrations generally between 70,000-120,000 mg / L and BOD5 concentrations between 35,000-70,000 mg / L. Depending on the treatment process, the total nitrogen and total phosphorus (TN) content in the wastewater will vary. For example, in traditional food waste treatment processes, the TN concentration is 1500-2500 mg / L, and the TP concentration is 50-1200 mg / L. In contrast, in the fermentation broth produced by food waste fermentation processes, the TN concentration is 3000-6000 mg / L, and the TP concentration is 600-1200 mg / L.

[0004] Food wastewater is a valuable resource, but current conventional treatment methods involve biological treatment followed by membrane filtration. These methods are not only costly but also only achieve harmless discharge, resulting in a waste of resources. For example, patent document CN111302559A discloses a method and system for treating food waste fermentation liquid. The method involves first adjusting the water quality and quantity of the fermentation liquid, then centrifuging and dehydrating the adjusted liquid. The resulting liquid undergoes demulsification and flocculation treatment, flotation treatment, primary denitrification, primary nitrification, secondary denitrification, and secondary nitrification followed by flocculation and sedimentation. A disinfectant is then added to the supernatant after flocculation and sedimentation for oxidation. The oxidized liquid is then aerated to remove the disinfectant, followed by biological aeration treatment. Finally, the aerated biologically treated liquid is disinfected again before being discharged. The current technical method involves numerous steps and complex processes, making low-cost treatment impossible. Furthermore, the primary purpose of this technical solution is the harmless treatment of fermentation liquid from food waste, rather than resource utilization, thus resulting in resource waste. Currently, there is no method for the resource-based treatment of such food waste wastewater.

[0005] In fact, with the generation of a large amount of kitchen waste in my country every day, a large amount of kitchen waste wastewater is also generated. Providing a low-cost, high-efficiency, and waste-to-treasure resource treatment method for kitchen waste wastewater is an effective way to utilize the nutrients in kitchen waste wastewater and is also a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] Based on the above background, this invention provides an economical and efficient practical process for the resource-based treatment of kitchen waste wastewater. The process is simple to operate, has low treatment costs, and produces kitchen waste wastewater with a COD ≥ 50000 mg / L, meeting the carbon source requirements for wastewater treatment plants. Furthermore, the ratios of BOD5 / COD, BOD5 / TN, and BOD5 / TP are significantly improved, indicating an increase in the content of small-molecule organic matter and further enhanced biodegradability after treatment. The total nitrogen and total phosphorus contents are significantly reduced, as is the NH3-N content, meaning that wastewater discharge will not have a significant impact on the water quality of wastewater treatment plants. Therefore, kitchen wastewater treated by the process provided by this invention can serve as a carbon source to meet the carbon source utilization needs of wastewater treatment plants.

[0007] This invention includes the following technical solutions:

[0008] In a first aspect, the present invention provides an application of wastewater from the resource recovery of kitchen waste as a carbon source in a wastewater treatment plant. The wastewater is obtained by treating it with a treatment agent composition according to a wastewater resource recovery treatment process. The treatment agent composition consists of a ferrate composite oxidant, bio-iron, and denitrifying bacteria.

[0009] The ferrate composite oxidant was prepared by the following method:

[0010] a1) Control the temperature of the reactor to 40-45℃, stir and mix 50% liquid alkali with 12% liquid sodium hypochlorite, and the mass ratio of liquid alkali to sodium hypochlorite is (2-3):1.

[0011] a2) Slowly add 40% liquid ferric chloride to the reactor at a stirring speed of 1000-1500 rpm. The volume of liquid ferric chloride added is 1 / 3-1 / 2 of the volume of liquid sodium hypochlorite. Stir for 1-2 hours to prepare ferrate composite oxidant.

[0012] Unless otherwise specified, the term "concentration" in this invention refers to mass concentration.

[0013] The bio-iron was prepared by the following method:

[0014] b1) Add industrial-grade solid ferrous sulfate and water to the bioreactor to form an aqueous solution with a concentration of 400-450 g / L. Add inorganic salts to ensure that the final concentrations in the solution meet the following requirements: (NH4)2SO4 1-1.5 g / L, KCl 0.1-0.2 g / L, K2HPO4 0.2-0.3 g / L, MgSO4·7H2O 0.2-0.3 g / L. Introduce bacterial strains to prepare a microbial reaction solution. The bacterial strains are a combination of *Thiobacillus ferrooxidans* and acidophilic bacteria, with a strain ratio of (6-9):1.

[0015] b2) Control the dissolved oxygen in the solution to 4-5 ppm, the reaction temperature to 20-40℃, and after 24 hours of reaction, when the Fe in the solution... 2+ When the concentration is below 0.1%, 30% of the liquid in the bioreactor is discharged and allowed to stand for aging to obtain bio-iron;

[0016] b3) Add the raw material described in step S1 to the bioreactor and repeat the reaction in step S2 to continuously obtain bio-iron.

[0017] The bio-iron prepared by the above method has a total iron content of 1-9%, a basicity of 10-22%, and an appearance of a brown viscous liquid. The bio-iron described in this invention can be replaced with chemically produced polyferric sulfate of the same iron content. Therefore, chemically produced polyferric sulfate is an equivalent replacement for the bio-iron provided by this invention, and treatment compositions that replace bio-iron with chemically produced polyferric sulfate also fall within the scope of this invention.

[0018] Theoretically, the denitrifying bacteria described in this invention are all denitrifying bacteria conventionally used in the art that have denitrification functions. In a preferred embodiment of this invention, the denitrifying bacteria are selected from one or more combinations of denitrifying bacilli, Stellaria media, Fibroblastella fluorescens, Micrococcus denitrifying, and Pseudomonas denitrifyingis; most preferably, it is a combination of denitrifying bacilli and Stellaria media, with the bacterial species accounting for 50-90% and 10-50%, respectively.

[0019] Unless otherwise specified, the food waste mentioned in this invention refers to food scraps generated during food processing, catering services, and institutional meal services, especially food scraps generated by restaurants, canteens, and similar establishments. These food scraps include waste cooking oil and kitchen waste.

[0020] The food waste wastewater described in this invention includes wastewater generated from food waste through traditional treatment processes and / or fermentation processes. The concentration of COD in the food waste wastewater is 70,000-120,000 mg / L, the concentration of BOD5 is 35,000-70,000 mg / L, the concentration of TN is 1,500-6,000 mg / L, and the concentration of TP is 50-1,200 mg / L.

[0021] Traditional food waste treatment processes produce wastewater from food waste pulping, steam heating, and oil-water separation; food waste fermentation treatment processes produce wastewater from food waste pulping, steam heating, fermentation, and oil-water separation. In a specific embodiment of this invention, the food waste fermentation treatment process specifically refers to the combined food waste recycling and biological processing process, abbreviated as CBP process.

[0022] Furthermore, the TN concentration in the wastewater from the aforementioned food waste fermentation treatment process is 3000-6000 mg / L, the TP concentration is 600-1200 mg / L, and the pH is 2-4. The wastewater has extremely high total nitrogen and total phosphorus content, posing a significant obstacle to its resource utilization. As those skilled in the art know, total nitrogen and total phosphorus consume BOD5, reducing the amount of organic matter available for microbial use and lowering the wastewater's biodegradability. Therefore, properly treating total nitrogen and total phosphorus in wastewater while ensuring its biodegradability is crucial for the resource utilization of food waste wastewater. This invention, through the combined use of the aforementioned treatment agent composition, achieves a COD ≥ 50000 mg / L in the treated food waste wastewater, a significant decrease in TN and TP concentrations, a pH of 6-9, and a significant increase in the ratios of BOD5 / COD, BOD5 / TN, and BOD5 / TP. This significantly reduces total nitrogen and total phosphorus content while improving the wastewater's biodegradability. Therefore, the kitchen waste wastewater treated by the treatment agent composition provided by the present invention can be used as a carbon source for the carbon source replenishment of the wastewater treatment plant, truly achieving the transformation from harmless discharge of kitchen waste wastewater to resource reuse.

[0023] This invention provides a process for the resource-based treatment of kitchen waste wastewater, the process comprising:

[0024] c1) Add ferrate compound oxidant to kitchen waste wastewater for simultaneous alkali adjustment and oxidation treatment;

[0025] c2) Add bio-iron or chemically produced polyferric sulfate to the reaction system of the previous step and stir for 5-200 minutes;

[0026] c3) Continue to add denitrifying bacteria to the reaction system for denitrification treatment, and the supernatant is the wastewater from the resource recovery of kitchen waste.

[0027] This invention does not specify the denitrification time of denitrifying bacteria, but generally requires more than 0.5 hours. The longer the action time, the better. Preferably, it is 0.5-24 hours, but 48, 72 or 96 hours are also acceptable. There is no limit to the maximum time.

[0028] In the aforementioned treatment process, the preparation method of the ferrate composite oxidant is as described in the first aspect of the present invention. The amount of ferrate composite oxidant added is 1-100 kg / ton of kitchen waste wastewater, and the preferred amount for kitchen waste wastewater generated by the CBP process is 10-25 kg / ton of kitchen waste wastewater, with the most preferred amount being 20 kg / ton of kitchen waste wastewater.

[0029] In the aforementioned treatment process, the preparation method of the bio-iron is as described in the first aspect of this invention, and the chemically produced polyferric sulfate can be obtained commercially. The amount of bio-iron or chemically produced polyferric sulfate (calculated based on an iron content of 1%) added is 10-1000 kg / ton of food waste wastewater, and for food waste wastewater generated by the CBP process, the preferred addition amount is 100-200 kg / ton of food waste wastewater, and the most preferred amount is 200 kg / ton of food waste wastewater.

[0030] In the treatment process, the denitrifying bacteria refer to all denitrifying bacteria with nitrogen removal function; preferably, the denitrifying bacteria are selected from one or more combinations of denitrifying bacilli, Stellaria media, Fibrobacterium fluorescens, Micrococcus denitrifying, and Pseudomonas denitrifyingis; most preferably, the denitrifying bacteria are a combination of denitrifying bacilli and Stellaria media, with the bacterial species accounting for 50-90% and 10-50%, respectively. The amount of denitrifying bacteria added is 0.01-10 kg / ton of kitchen waste wastewater, and for kitchen waste wastewater generated by the CBP process, the preferred addition amount is 0.2-0.5 kg / ton of kitchen waste wastewater, and the most preferred amount is 0.2 kg / ton of kitchen waste wastewater.

[0031] The ferrate composite oxidant provided by this invention is a pre-prepared and ready-to-use treatment agent that can simultaneously adjust the alkali and oxidize kitchen waste wastewater, decomposing large organic molecules into smaller VFAs and removing some phosphorus. The inventors refer to this as advanced oxidation treatment. Those skilled in the art know that conventional kitchen wastewater is acidic, with a pH typically between 2 and 4. Although wastewater oxidation is a routine procedure, it is necessary to first adjust the pH of the solution to 6-9 with alkali before the oxidation reaction can begin. This invention, by adding a self-prepared ferrate composite oxidant, achieves simultaneous alkali adjustment and oxidation, significantly reducing costs and improving treatment efficiency. Furthermore, the ferrate composite oxidant provided by this invention can also remove some NH3-N, converting it into nitrite or nitrate nitrogen, facilitating subsequent denitrification treatment with denitrifying bacteria and creating favorable conditions for improving the BOD5 / TN ratio. In addition, the wastewater from kitchen waste is quite smelly. Ferrate, as an oxidant, can also deodorize it. The principle is that it can oxidize odorous substances such as hydrogen sulfide, thiols and skatole, while killing the microorganisms that produce odorous substances, thus greatly improving the working environment for employees.

[0032] The bio-iron provided by this invention is microbial polyferric sulfate generated from microorganisms and ferrous sulfate heptahydrate. In this invention, it primarily functions to remove phosphorus. Simultaneously, due to the good flocculation effect of bio-iron on large molecules, its addition after alkali-adjusting oxidation can flocculate and precipitate some of the recalcitrant COD in the water. Recalcitrant COD refers to COD that is not easily utilized by microorganisms; flocculating and precipitating it indirectly improves the biodegradability of kitchen waste wastewater. Furthermore, this invention specifically chooses to add bio-iron before denitrification by denitrifying bacteria because microorganisms absorb phosphorus during denitrification, which consumes a large amount of BOD5 (1P: 10-20 BOD ratio), leading to a reduction in the valuable BOD5 in kitchen waste wastewater. Therefore, the treatment method provided by this invention first selects to add bio-iron for effective phosphorus removal before denitrification, avoiding the consumption of valuable BOD5 during the denitrification stage. In addition, the inventors have also discovered that the bio-iron provided by this invention has a significant water purification effect on kitchen waste wastewater.

[0033] Because the ferrate composite oxidant converts some of the NH3-N in wastewater into nitrite or nitrate nitrogen, it creates favorable conditions for denitrification treatment using denitrifying bacteria. This invention selects denitrifying bacteria for denitrification treatment, effectively reducing the total nitrogen concentration in wastewater, significantly increasing the BOD5 / TN ratio, and enhancing the biodegradability of the wastewater. The denitrifying bacteria provided by this invention can be selected from one or more combinations of denitrifying bacilli, Stellaria media, *Aeromonas fluorescens*, *Micrococcus denitrifying*, and *Pseudomonas denitrifyingus*, and can be purchased commercially or obtained through in-house cultivation and screening. Through screening and optimization by the inventors, the optimal denitrifying bacteria obtained is a combination of denitrifying bacilli and Stellaria media.

[0034] This invention provides a method for treating kitchen waste wastewater using kitchen waste wastewater as raw material and a treatment agent composition provided by this invention, and for treating kitchen waste wastewater using a resource recovery treatment process provided by this invention.

[0035] The concentrations of COD in the water from the food waste resource recovery treatment are ≥50000mg / L, BOD5 concentration ≥27000mg / L, NH3-N concentration ≤200mg / L, TN concentration ≤1500mg / L, and TP concentration ≤60mg / L.

[0036] The COD concentration of the wastewater obtained through the process provided by this invention is ≥50000 mg / L, meeting the carbon source requirements for wastewater treatment plants. The BOD5 / COD ratio is ≥0.5, BOD5 / TN is ≥18, and BOD5 / TP is ≥450. Compared with untreated wastewater, its biodegradability is significantly improved. Although the wastewater still contains a certain concentration of total nitrogen and total phosphorus, wastewater treatment plants typically add carbon source at a ratio of 0.01%, equivalent to adding 0.1 kg of carbon source per 1.0 t of water. After addition, without considering the removal of total nitrogen and total phosphorus, the concentrations of total nitrogen and total phosphorus are reduced to very low levels, having little impact on the water quality of the wastewater treatment plant. Therefore, the wastewater obtained through the process provided by this invention can be used as a carbon source for wastewater treatment plant carbon source replenishment.

[0037] This invention provides an application of the water from the resource-based treatment of kitchen waste as a carbon source in wastewater treatment plants.

[0038] This invention provides an application of the food waste wastewater resource utilization process described herein in at least one of the following:

[0039] d1) Application in the resource utilization treatment of kitchen waste and wastewater;

[0040] d2) Application in the preparation of water for the resource-based treatment of kitchen waste.

[0041] The advantages of the technical solution provided by this invention are as follows:

[0042] The proposed treatment process for kitchen waste wastewater is simple, easy to operate, inexpensive, and easy to maintain, providing an economical and efficient solution to the problem of difficult kitchen waste wastewater treatment. After treatment using the process provided by this invention, the kitchen waste wastewater is no longer sewage to be discharged, but rather a carbon source needed by wastewater treatment plants. It can be sold as a commodity to various wastewater treatment plants for carbon source replenishment.

[0043] Currently, the carbon sources commonly used in wastewater treatment plants include methanol, sodium acetate, and glucose-based products. Methanol is a Class A hazardous chemical, and microorganisms respond slowly to it; sodium acetate has a low equivalent COD and is expensive; glucose-based products have poor dosing precision and are more likely to cause sludge bulking. The technical solution provided by this invention can solve the above problems. Using food waste wastewater as raw material, the carbon source required by wastewater treatment plants can be prepared through a simple process and low treatment cost. Even with the continuous increase in food waste production, the amount of carbon source prepared by this method remains stable.

[0044] This invention successfully transforms the current situation of harmless treatment of kitchen waste wastewater into resource utilization, not only solving the problem of kitchen waste wastewater treatment, but also turning waste into treasure, with high economic, social and environmental benefits. Attached Figure Description

[0045] Figure 1 A schematic diagram of the resource recovery process.

[0046] Figure 2 Comparison of samples of food wastewater generated by the CBP process before and after treatment: Left: before treatment; Right: after treatment.

[0047] Figure 3 Samples of food wastewater generated by the CBP process were submitted for testing before and after treatment. Left: after treatment; Right: before treatment. Detailed Implementation

[0048] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] Terminology Explanation

[0050] COD: Chemical Oxygen Demand (COD) is a chemical measurement of the amount of reducing substances in a water sample that need to be oxidized. Under certain conditions, it is measured by the amount of oxidant consumed to oxidize the reducing substances in 1 liter of water sample, and converted into the number of milligrams of oxygen required per liter of water sample to be completely oxidized, expressed in mg / L.

[0051] BOD5: Biochemical Oxygen Demand (BOD) refers to the amount of dissolved oxygen consumed by microorganisms in decomposing certain oxidizable substances, especially organic matter, in a certain volume of water within a certain period, expressed in mg / L.

[0052] TN: Total Nitrogen (TN) is the total amount of inorganic and organic nitrogen in water, including NO. 3- NO 2- and NH 4+ Inorganic nitrogen and organic nitrogen such as proteins, amino acids and organic amines are calculated in milligrams per liter of water.

[0053] TP: Total Phosphorus (TP) is the sum of phosphorus in wastewater in both inorganic and organic forms.

[0054] VFAs: Volatile fatty acids.

[0055] The technical solution of the present invention and the technical effects achieved by the technical solution will be described below with reference to specific embodiments.

[0056] S1: Control the temperature of the reactor to 40-42℃, add 200 kg of 50% liquid alkali and 70 kg of 12% liquid sodium hypochlorite to the reactor, and stir to mix the liquid alkali and sodium hypochlorite thoroughly.

[0057] S2: At the same temperature, the stirrer speed in the reactor was controlled at 1200 rpm, and 30 kg of liquid ferric chloride with a mass concentration of 40% was slowly added. After stirring for 1 hour, stirring was stopped, and 300 kg of ferrate composite oxidant was prepared. The liquid was a translucent purple-red liquid. Ultraviolet spectrophotometry detected that 30% of the ferric trivalent iron in the liquid system was converted to ferric hexavalent iron.

[0058] S1: Add industrial-grade solid ferrous sulfate and water to the bioreactor to form a ferrous sulfate aqueous solution with a concentration of 450 g / L. Add (NH4)2SO4, KCl, K2HPO4 and MgSO4·7H2O to make the final concentrations in the solution meet the following requirements: (NH4)2SO4 1 g / L, KCl 0.1 g / L, K2HPO4 0.2 g / L and MgSO4·7H2O 0.2 g / L. Mix ferrooxidizobacillus and acidophilic bacteria at a ratio of 9:1 and introduce the mixed bacterial strain into the bioreactor to prepare the microbial reaction solution.

[0059] S2: Turn on the aeration device, control the dissolved oxygen in the solution to 4 ppm, maintain the reaction temperature at 38-40℃, and detect the Fe content in the solution after 24 hours of reaction. 2+ Concentration, when Fe in solution 2+ When the concentration is below 0.1%, 30% of the liquid in the bioreactor is discharged and allowed to stand for aging to obtain bio-iron;

[0060] S3) Add the raw material described in step S1 to the bioreactor and repeat the reaction in step S2 to continuously produce bio-iron.

[0061] Purchase denitrifying bacteria and Stellate bacteria, mix them in a 1:1 ratio, and use them as denitrifying bacteria for later use. Example

[0062] This embodiment uses the wastewater generated by the combined bioprocessing technology (CBP process) for recycling kitchen waste from Sichuan Lixinglong Environmental Protection Technology Co., Ltd. as the treatment object. The water quality monitoring data of the wastewater is shown in Table 1:

[0063] Table 1. CPB process water quality monitoring data

[0064]

[0065] The resource recovery process for the wastewater is as follows:

[0066] S1: Take the ferrate composite oxidant prepared in Example 1 and add it to the wastewater at a ratio of 15 kg / ton of kitchen waste wastewater, and react for 1 hour;

[0067] S2: The iron content of the bio-iron prepared in Example 2 was 1%, and it was added at a ratio of 100 kg / ton of kitchen waste wastewater and reacted for 0.5 hours.

[0068] S3: Add the denitrifying bacteria prepared in Example 3 to the reaction system at a ratio of 0.2 kg / ton of kitchen waste wastewater. React for 6 hours to obtain treated water. The water quality monitoring report of the treated water is shown in Table 2.

[0069] The appearance comparison results of the CBP process wastewater from food waste before and after treatment in this embodiment are as follows: Figure 2 As shown in the image, the left side of the figure shows the sample before treatment, and the right side shows the sample after treatment. It can be seen that the water before treatment was turbid and dark gray, while the water after treatment was clearer and lighter in color, appearing orange-yellow. The samples were sent for testing, and the results are shown below. Figure 3 As shown. The samples in the following examples and comparative examples do not differ significantly from those in Example 1 in appearance. Therefore, specific images are not presented here. All samples obtained in the experiment were submitted for testing in the packaging condition described above. Example

[0070] The wastewater source is as described in Example 1, and the resource utilization treatment process for the wastewater is the same as in Example 1, except that the addition ratio of ferrate composite oxidant is 20 kg / ton of kitchen waste wastewater, and the addition ratio of bio-iron is 200 kg / ton of kitchen waste wastewater. Example

[0071] The wastewater source is as described in Example 1, and the resource utilization treatment process for the wastewater is the same as in Example 1, except that the addition ratio of ferrate composite oxidant is 20 kg / ton of kitchen waste wastewater, and the addition ratio of bio-iron is 300 kg / ton of kitchen waste wastewater. Example

[0072] The wastewater source is as described in Example 1, and the resource utilization treatment process for the wastewater is the same as in Example 1, except that the addition ratio of ferrate composite oxidant is 25 kg / ton of kitchen waste wastewater, and the addition ratio of bio-iron is 200 kg / ton of kitchen waste wastewater.

[0073] Table 2. Water quality monitoring report of influent and effluent of the treatment process in the example.

[0074]

[0075] In the table, B / C, B / TN, and B / TP represent the ratios of BOD5 / COD, BOD5 / TN, and BOD5 / TP.

[0076] As can be seen from the monitoring data in Table 2, the COD concentration of the treated water obtained by the process provided by the present invention is ≥50000mg / L, which meets the requirements of the wastewater treatment plant for supplementing carbon source. In Example 1, the BOD5 / COD ratio is slightly higher than that of the wastewater, with BOD5 / TN=18.5 and BOD5 / TP=497.3. The biodegradability of the treated water is significantly improved compared to the wastewater, indicating that the biodegradability of the wastewater obtained by the present invention is improved and can be used as a carbon source in the wastewater treatment plant.

[0077] Compared to Example 1, Example 2 increased the dosage of ferrate composite oxidant and bio-iron. The effluent data showed that the BOD5 / COD ratio increased to 0.5632, further improving the biodegradability of the wastewater. Example 3 further increased the dosage of bio-iron based on Example 2. The effluent data showed that the improvement in each data point was not significant compared to Example 2. Considering the significantly increased cost, the preferred bio-iron dosage of this invention is 200 kg / ton of kitchen waste wastewater. Example 4 increased the dosage of ferrate composite oxidant based on Example 2. The effluent data showed a decrease in the BOD5 concentration in the water, indicating that increasing the oxidant was not conducive to improving the biodegradability of the treated water. Therefore, the preferred ferrate composite oxidant dosage of this invention is 20 kg / ton of kitchen waste wastewater.

[0078] Wastewater from the same source as in Example 1 was used as the treatment target. Sodium hydroxide was added to adjust the pH of the wastewater to 6-9, without oxidation. Bio-iron obtained in Preparation Example 2 was added at a ratio of 200 kg / ton of wastewater and reacted for 0.5 hours. Denitrifying bacteria prepared in Preparation Example 3 were added to the reaction system at a ratio of 0.2 kg / ton of wastewater and reacted for 6 hours to obtain treated water. The water quality monitoring report of the treated water is shown in Table 3.

[0079] Wastewater from the same source as in Example 1 was used as the treatment target. Sodium hydroxide was added to adjust the pH of the wastewater to 6-9, and then ozone was added for oxidation. The amount of oxidant added was 5 kg / ton of wastewater. Bio-iron obtained in Preparation Example 2 was added at a ratio of 200 kg / ton of wastewater, and the reaction was carried out for 0.5 hours. Denitrifying bacteria prepared in Preparation Example 3 were added to the reaction system at a ratio of 0.2 kg / ton of wastewater, and the reaction was carried out for 6 hours to obtain treated water. The water quality monitoring report of the treated water is shown in Table 3.

[0080] Wastewater from the same source as in Example 1 was used as the treatment target. Ferrate composite oxidant prepared in Preparation Example 1 was added to the wastewater at a ratio of 20 kg / ton of wastewater and reacted for 1 hour. In this example, ferric chloride was used to replace bio-iron and was added at a ratio of 20 kg / ton of wastewater (calculated based on a ferric chloride mass concentration of 40%) and reacted for 0.5 hours. Denitrifying bacteria prepared in Preparation Example 3 were added to the reaction system at a ratio of 0.2 kg / ton of wastewater and reacted for 6 hours to obtain treated water. The water quality monitoring report of the treated water is shown in Table 3.

[0081] Wastewater from the same source as in Example 1 was used as the treatment target. Ferrate composite oxidant prepared in Preparation Example 1 was added to the wastewater at a ratio of 20 kg / ton of wastewater and reacted for 1 hour. In this example, chemically produced polyferric sulfate was used to replace bio-iron, and the reaction was carried out at a ratio of 20 kg / ton of wastewater (calculated based on the iron content of 10% of chemically produced polyferric sulfate) for 0.5 hours. Denitrifying bacteria prepared in Preparation Example 3 were added to the reaction system at a ratio of 0.2 kg / ton of wastewater and reacted for 6 hours to obtain treated water. The water quality monitoring report of the treated water is shown in Table 3.

[0082] Using kitchen waste wastewater from the same source as in Example 1 as the treatment object, the resource recovery process for the wastewater is the same as in Example 1, except that the order of steps S2 and S3 is reversed. The resource recovery process for the wastewater is as follows:

[0083] S1: Take the ferrate composite oxidant prepared in Example 1 and add it to the wastewater at a ratio of 20 kg / ton of kitchen waste wastewater, and react for 1 hour;

[0084] S2: Add the denitrifying bacteria prepared in Example 3 to the reaction system at a ratio of 0.2 kg / ton of kitchen waste wastewater, and react for 6 hours;

[0085] S3: Take the bio-iron prepared in Preparation Example 2 and react it with 200 kg / ton of kitchen waste wastewater for 0.5 hours to obtain treated water. The water quality monitoring report of the treated water is shown in Table 3.

[0086] Table 3. Water quality monitoring report of influent and effluent from the comparative treatment process

[0087]

[0088] As can be seen from the effluent data of Comparative Example 1, without oxidation, the COD concentration did not change significantly, resulting in a BOD5 / COD ratio of only about 0.3, which severely affected the biodegradability of the treated water. Secondly, the NH3-N concentration in the wastewater remained essentially unchanged, which also directly affected subsequent denitrification treatment. Without oxidation, even with the subsequent use of alkaloids and denitrifying bacteria, the reduction in total phosphorus and total nitrogen after treatment was not substantial.

[0089] As can be seen from the effluent data of Comparative Example 2 in Table 3, although the method of adjusting alkali before ozone oxidation can also reduce COD, the reduction is not as significant as that of the ferrate composite oxidant provided in this invention. Secondly, the inventors discovered that conventional ozone oxidation has little effect on the NH3-N concentration in wastewater, but the ferrate composite oxidant provided in this invention can significantly reduce the NH3-N concentration in wastewater, partially converting it into nitrite or nitrate nitrogen, thus creating favorable conditions for subsequent denitrification.

[0090] As shown in Comparative Example 3 in Table 3, although ferric chloride can achieve phosphorus removal and eliminate some COD, it cannot purify the water. Instead, it increases chloride levels in the treated water by 5200 mg / L, which is undesirable for wastewater treatment plants. Chloride affects microbial activity, requiring further treatment before use. Furthermore, the inventors unexpectedly discovered that the second-step reaction using ferric chloride resulted in higher COD levels in the treated water, leading to a decrease in the BOD5 / COD ratio and reduced biodegradability. The inventors believe that the bio-iron provided by this invention has a better effect on flocculating recalcitrant COD in water, while ferric chloride is less effective in this regard, resulting in a smaller reduction in COD in the treated water.

[0091] As can be seen from the effluent data of Comparative Example 4 in Table 3, although the chemical method of polyferric sulfate can achieve a treatment effect comparable to that of the bio-iron provided by this invention, the chemical method of polyferric sulfate is more expensive. The price of chemically produced polyferric sulfate is approximately 1000 yuan / ton; based on a ratio of 20 kg / ton of kitchen waste wastewater, this cost is 20 yuan / ton of kitchen waste wastewater. The price of bio-iron is approximately 10 yuan / ton; based on a ratio of 200 kg / ton of kitchen waste wastewater, this cost is 2 yuan / ton of kitchen waste wastewater. Therefore, compared with chemically produced polyferric sulfate, the bio-iron provided by this invention is superior.

[0092] As can be seen from the data in Comparative Example 5 in Table 3, when denitrifying bacteria are used first for nitrogen removal, followed by the addition of bio-iron for reaction, the phosphorus content in the system is high during denitrification. Microorganisms absorb phosphorus during denitrification, which consumes a large amount of BOD5, leading to a decrease in BOD5 content in the effluent of Comparative Example 5. This, in turn, reduces the BOD5 / COD ratio and decreases the biodegradability of the treated water. Therefore, the optimal treatment process flow established in this invention—using a ferrate composite oxidant for oxidation treatment, adding bio-iron first for reaction, and then adding denitrifying bacteria for nitrogen removal—is the best.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. Application of kitchen waste resource treatment water as a carbon source in a sewage treatment plant, wherein the kitchen waste resource treatment water is obtained by using a treatment agent composition according to a kitchen waste wastewater resource treatment process, and the treatment agent composition is composed of a high ferrate composite oxidant, biological iron and denitrifying bacteria; the high ferrate composite oxidant is prepared by the following method: a1) stirring and mixing liquid caustic soda with a concentration of 50% and liquid sodium hypochlorite with a concentration of 12% at a temperature of 40-45 ℃, and the mass ratio of liquid caustic soda to sodium hypochlorite is (2-3):1; a2) slowly adding liquid ferric chloride with a concentration of 40% to the reaction kettle at a stirring speed of 1000-1500 rpm, and the volume of liquid ferric chloride is 1 / 3-1 / 2 of that of liquid sodium hypochlorite, and stirring for 1-2 hours to prepare the high ferrate composite oxidant; the biological iron is prepared by the following method: b1) adding industrial-grade solid ferrous sulfate and water to a bioreactor to form an aqueous solution with a concentration of 400-450 g / L, adding inorganic salts to make the final concentration of (NH4)2SO41-1.5 g / L, KCL 0.1-0.2 g / L, K2HPO40.2-0.3 g / L, and MgSO4·7H2O 0.2-0.3 g / L in the solution, introducing a bacterial strain, and preparing a microbial reaction solution, wherein the bacterial strain is a combination of ferrous iron-oxidizing bacteria and acidophilic bacteria, and the ratio of the number of bacterial strains is (6-9):1; b3) repeating the reactions of steps b1) and b2) to continuously obtain biological iron; the denitrifying bacteria are a combination of denitrifying bacteria and Shewanella, and the ratio of the number of bacterial strains is 50-90% and 10-50%, respectively; the kitchen waste wastewater resource treatment process comprises: c1) adding the high ferrate composite oxidant to kitchen waste wastewater for simultaneous alkaline adjustment and oxidation treatment; c2) adding biological iron to the reaction system of the previous step and stirring for 5-200 minutes; c3) adding denitrifying bacteria to the reaction system for denitrification treatment, and the supernatant is kitchen waste resource treatment water; the concentration of COD in the kitchen waste wastewater is 70000-120000 mg / L, the concentration of BOD5 is 35000-70000 mg / L, the concentration of TN is 1500-6000 mg / L, and the concentration of TP is 50-1200 mg / L; the kitchen waste wastewater includes wastewater produced by traditional treatment processes or fermentation treatment processes of kitchen waste. The kitchen waste wastewater is selected from wastewater produced by a kitchen waste fermentation treatment process, wherein the kitchen waste fermentation treatment process refers to a kitchen waste recycling combined biological processing process, referred to as CBP process, the concentration of TN in the kitchen waste wastewater is 3000-6000 mg / L, the concentration of TP is 600-1200 mg / L, and the pH is 2-4. ​ ​ ​ ​ b2) control the dissolved oxygen in the solution to be 4-5 ppm, the reaction temperature to be 20-40 °C, and after 24 hours of reaction, when the Fe 2+ When the concentration is lower than 0.1%, 30% of the liquid in the bioreactor is discharged and matured to obtain bio-iron. ​ ​ ​ ​ ​ ​ 2. Use according to claim 1, characterized in that, ​ 3. Use according to claim 2, characterized in that, ​ 4. Use according to claim 3, characterized in that, For the CBP process of kitchen waste wastewater, the addition amount of ferric salt composite oxidant is 10-25 kg / ton of kitchen waste wastewater; according to the iron content of 1%, the addition amount of bio-iron is 100-200 kg / ton of kitchen waste wastewater; the addition amount of denitrifying bacteria is 0.2-0.5 kg / ton of kitchen waste wastewater.

5. Use according to claim 4, characterized in that, For the CBP process of kitchen waste wastewater, the addition amount of ferric salt composite oxidant is 20 kg / ton of kitchen waste wastewater; according to the iron content of 1%, the addition amount of bio-iron is 200 kg / ton of kitchen waste wastewater; the addition amount of denitrifying bacteria is 0.2 kg / ton of kitchen waste wastewater.

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