Process for preparing carbon source from kitchen waste water

Abstract

The present application relates to garbage, sewage treatment technical field, disclose a kind of process for preparing carbon source of kitchen waste water, comprising the following steps: a), to the high concentration kitchen waste water of untreated pretreatment;B), to the kitchen waste water after pretreatment anaerobic ammonification treatment;C), to the wastewater after being fully anaerobic ammonification treatment, join base agent, the pH of wastewater is adjusted to strong alkaline;D), the wastewater after pH adjustment is heated and then enters critical vacuum air floatation system treatment;E), waste gas waste residue generated in step d) is harmlessly treated and resource utilization;And, the organic matter wastewater generated in step d) is concentrated, then acetic acid, methanol and sodium acetate are mixed and matched, to obtain high concentration organic carbon source.The present application has the advantages of not producing foul-smelling gas, waste residue resource utilization, high energy utilization rate, reducing wastewater treatment cost and municipal sewage treatment cost, etc., so that kitchen waste water disposal realizes the maximum utilization of resources.

Description

Technical Field

[0001] This invention relates to the field of waste and sewage treatment technology, and more specifically, to a process for preparing a carbon source from kitchen wastewater. Background Technology

[0002] With the rapid advancement of urbanization and the booming catering industry, the discharge of kitchen waste (food waste) has increased dramatically, placing enormous pressure on kitchen waste (food waste) treatment. Kitchen wastewater contains a large amount of organic matter, such as starch, cellulose, protein, and lipids, and the abundant organic matter in the wastewater has a high utilization rate.

[0003] Currently, wastewater treatment plants have accumulated rich experience in using organic compounds such as acetic acid, methanol, glucose, and sodium acetate as external carbon sources, confirming their effectiveness. However, these carbon sources are expensive and have complex compositions, making their widespread practical application difficult. In contrast, concentrating high-concentration organic wastewater into a high-concentration organic waste liquid through technological processes and using it as an external carbon source can reduce wastewater discharge and enable the resource utilization of organic matter. Wastewater from kitchen waste, in particular, is rich in organic matter, has good biodegradability, and high utilization rate, making it an ideal substrate for carbon source preparation. Therefore, research on preparing carbon sources from high-concentration kitchen wastewater has gradually become a hot topic in recent years.

[0004] Furthermore, in response to national water ecological environment protection requirements, discharge standards for domestic and industrial wastewater treatment plants have been increasing year by year, especially for total nitrogen. In many regions, the COD of influent to urban and industrial wastewater treatment plants is low, and the C / N ratio is severely imbalanced, leading to a gradual increase in the demand for carbon sources by these plants and thus increasing their operating costs. To address this, and to reduce operating costs and improve efficiency, a resource utilization technology for preparing organic carbon sources from high-concentration kitchen wastewater has been developed. This technology can both reduce wastewater treatment volume and increase the production capacity of kitchen waste.

[0005] Therefore, there is an urgent need for a technology that can economically and efficiently convert kitchen wastewater into a high-quality liquid carbon source. Summary of the Invention

[0006] In view of this, the present invention proposes a process for preparing carbon sources from kitchen wastewater, aiming to solve the problems of unstable product quality, low utilization efficiency, and easy secondary pollution caused by the inhibitory effect of high concentration of ammonia nitrogen in the wastewater when preparing carbon sources from kitchen wastewater in the prior art.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A process for preparing a carbon source from kitchen wastewater includes the following steps: a) Pre-treat untreated high-concentration kitchen wastewater to remove large impurities or sediments; b) Anaerobic ammoniation treatment of pretreated kitchen wastewater; c) Add an alkaline agent to the wastewater after it has undergone sufficient anaerobic ammoniation treatment to adjust the pH of the wastewater to a strongly alkaline state; d) After pH adjustment, the wastewater is heated and then enters the critical vacuum flotation system for secondary impurity removal. e) The waste gas and waste residue generated in step d) are treated in a harmless manner and utilized for resource recovery; and the organic wastewater generated in step d) is concentrated and then mixed with acetic acid, methanol and sodium acetate to obtain a high-concentration organic carbon source.

[0009] Preferably, in step b), the pretreated kitchen wastewater is sent to an anaerobic device for full ammoniation for 2-3 hours.

[0010] Preferably, in step c), the pH of the wastewater is adjusted to a strongly alkaline range of 11.8 to 12.2.

[0011] Preferably, in step c), the alkaline agent is sodium aluminate.

[0012] Preferably, in step d), the temperature of the wastewater after heating treatment is 63℃~67℃.

[0013] Preferably, in step d), the temperature of the wastewater after heating treatment is 65°C.

[0014] Preferably, in step d), the critical vacuum flotation system removes small scum from the wastewater and strips ammonia-containing waste gas from the wastewater by using a critical vacuum flotation method after heating, thus obtaining organic wastewater.

[0015] Preferably, in step d), the time for entering the critical vacuum air flotation system for processing is 13~17 minutes.

[0016] Preferably, in step e), the ammonia in the ammonia-containing waste gas is recovered and reused through acid washing, other remaining odorous gases are treated through an absorption tower, and small scum is composted aerobically.

[0017] Preferably, in step e), the concentration treatment is to concentrate the organic wastewater using an MVR device.

[0018] Compared with existing technologies, the process for preparing carbon sources from kitchen wastewater according to the present invention has the following beneficial effects: (1) This invention first improves the biodegradability of organic matter through "anaerobic ammoniation", and then efficiently removes high concentrations of ammonia nitrogen from wastewater through the core combination process of "strong alkali-heating-critical vacuum flotation", which fundamentally solves the problem of traditional kitchen wastewater carbon source inhibiting the biochemical system. The carbon source product prepared has high COD concentration, high VFA ratio and low ammonia nitrogen content, and the product quality is uniform.

[0019] (2) This invention not only converts large organic molecules such as fats, carbohydrates, and proteins in high-concentration kitchen wastewater into easily biodegradable organic matter, increasing the utilization rate of organic matter and preparing a high-concentration organic carbon source, but also alleviates the pressure on wastewater treatment and solves the problems of large differences in concentration and composition and high cost of traditional carbon sources. Furthermore, it enables the full resource utilization of organic matter in wastewater. In addition, this invention can recover ammonia-containing waste gas generated during the treatment process by acid washing to produce ammonium salts, realizing the resource utilization of pollutants, avoiding secondary pollution, and demonstrating significant environmental and economic benefits.

[0020] (3) By adopting equipment such as vacuum flotation and MVR concentration, the present invention effectively reduces the energy consumption of the ammonia removal and concentration steps, improves the overall energy utilization rate of the process, reduces operating costs, and makes the resource utilization of kitchen wastewater more economically feasible.

[0021] Overall, this invention has advantages such as not producing odorous gases, resource utilization of waste residue, high energy utilization rate, and reduced wastewater treatment costs and urban sewage treatment costs, thus maximizing the utilization of resources in the treatment of kitchen wastewater. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0023] Figure 1 This is a process flow diagram of a method for preparing a carbon source from kitchen wastewater according to the present invention. Detailed Implementation

[0024] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0025] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0026] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0027] Example: This embodiment provides a process for preparing carbon sources from kitchen wastewater, aiming to solve the problems of low organic matter conversion efficiency, unstable quality due to excessively high ammonia nitrogen content in the product, and secondary pollution caused by the treatment process in existing technologies for preparing carbon sources from kitchen wastewater. This technical solution uses a combined process of "anaerobic ammoniation-strong alkali high-temperature deammoniation-concentration" to economically and efficiently convert high-concentration, high-ammonia-nitrogen kitchen wastewater into a liquid carbon source usable in wastewater treatment plants.

[0028] For details, please refer to [link / reference]. Figure 1 This embodiment describes a process for preparing a carbon source from kitchen wastewater, comprising the following steps: a) Pre-treat untreated high-concentration kitchen wastewater to remove large impurities or sediments.

[0029] The purpose of this step is to: intercept large suspended solids such as bones, vegetable leaves, silt, and fibers in kitchen wastewater to prevent clogging and wear of subsequent equipment; reduce the load on subsequent anaerobic ammoniation and flotation to avoid solid sediment affecting reaction efficiency; and provide a water quality foundation for subsequent stable operation to ensure process continuity.

[0030] This step is fundamental to the resource utilization of wastewater and ensures the stable operation of subsequent biochemical and physicochemical treatment units.

[0031] b) Anaerobic ammoniation treatment of pretreated kitchen wastewater.

[0032] The purpose of this step is to address the problem that a large amount of organic matter in kitchen wastewater is macromolecules with poor biodegradability; through the action of anaerobic microorganisms, complex carbohydrates and proteins are decomposed into small-molecule organic matter, mainly volatile fatty acids (VFA), which significantly improves the utilization rate of organic matter and provides a high-quality raw material basis for the subsequent preparation of high-quality carbon sources.

[0033] This step can transform organic matter that is difficult to use directly into a form that is easy to biodegrade, thus solving the problems of complex composition and low utilization rate of traditional carbon sources.

[0034] c) Add an alkaline agent to the wastewater after it has undergone sufficient anaerobic ammoniation treatment to adjust the pH of the wastewater to a strongly alkaline state.

[0035] Kitchen wastewater contains high concentrations of ammonia nitrogen. If not removed, it will not only severely imbalance the C / N ratio of the final carbon source product, but also have a toxic and inhibitory effect on microorganisms in the wastewater treatment plant when used as an external carbon source. This step involves raising the pH to a strongly alkaline level, thereby reducing the concentration of ammonium ions (NH4+) in the wastewater. + A large amount of it will be converted into free ammonia (NH3), creating the necessary thermodynamic conditions for subsequent stripping and removal.

[0036] d) After pH adjustment, the wastewater is heated and then enters the critical vacuum flotation system for secondary impurity removal.

[0037] Heating treatment can further reduce the solubility of free ammonia in water, decrease wastewater viscosity, improve bubble adhesion efficiency, and promote the flotation and separation of impurities. Meanwhile, critical vacuum flotation uses gas-liquid mass transfer to strip volatile free ammonia from the liquid phase, and micro-flotation removes residual suspended solids, grease, colloids, some heavy metals, and insoluble impurities. This combined operation can efficiently and thoroughly remove ammonia nitrogen from wastewater, significantly improving the purity and quality of the final carbon source product.

[0038] This step yields an intermediate product rich in organic matter but with extremely low ammonia nitrogen content, paving the way for the final high-rate concentration.

[0039] e) The waste gas and waste residue generated in step d) are treated in a harmless manner and utilized for resource recovery; and the organic wastewater generated in step d) is concentrated and then mixed with acetic acid, methanol and sodium acetate to obtain a high-concentration organic carbon source.

[0040] Collecting and treating the scum and odorous gases generated by air flotation to meet emission standards can prevent secondary pollution. At the same time, the waste residue can be further recycled (such as composting), improving the overall economic efficiency and environmental protection level of the process.

[0041] Concentration treatment increases the concentration of effective carbon sources such as COD and VFA in organic wastewater, meeting the concentration requirements for added carbon sources. Adding acetic acid, methanol, and sodium acetate allows for precise control of the carbon source components and carbon-nitrogen ratio, improving the biodegradability and utilization efficiency of the carbon source. Furthermore, since most inorganic salts and inhibitory substances (such as ammonia nitrogen) have been removed in the preceding steps, the concentration process here can be carried out efficiently, resulting in a liquid organic carbon source product with extremely high chemical oxygen demand (COD) and stable quality. This solves the problems of low concentration and high transportation costs associated with traditional carbon sources, achieving high-value resource utilization of kitchen wastewater.

[0042] Furthermore, the present invention, by selectively adding acetic acid, methanol, and sodium acetate after concentration, is not simply a matter of adding components together, but rather achieves the following effects in denitrification applications: ① The denitrification rate is increased by more than 40%; ② Carbon source utilization rate increased by 35%; ③ The system's stability and adaptability are significantly enhanced; ④ Non-toxic inhibitor, sludge activity increased by 30%.

[0043] Furthermore, in a preferred embodiment, in step b), the pretreated kitchen wastewater is sent to an anaerobic device for full ammoniation for 2-3 hours.

[0044] Pretreated kitchen wastewater is ammonified in an anaerobic device for 2-3 hours. This allows for the initial hydrolysis and ammonification of organic matter under mild anaerobic conditions, breaking down large molecules such as proteins and polysaccharides into smaller organic molecules and releasing ammonia nitrogen, thus improving the biodegradability of the wastewater. At the same time, the short reaction time avoids excessive anaerobic fermentation and methanogenesis, which would lead to carbon source loss. This maximizes the retention of usable organic components and provides sufficient substrate for the subsequent preparation of high-concentration organic carbon sources.

[0045] Furthermore, in a preferred embodiment, in step c), the pH of the wastewater is adjusted to a strongly alkaline range of 11.8 to 12.2.

[0046] Adjusting the pH of the wastewater to a strongly alkaline range of 11.8 to 12.2 has several advantages. First, it allows more ammonia nitrogen produced by ammonification to exist in the form of free ammonia, facilitating its volatilization and removal during subsequent air flotation, thus reducing the ammonia nitrogen content in the subsequent carbon source products. Second, this strongly alkaline environment effectively disrupts the stability of colloids, oils, and suspended solids in the wastewater, promoting their coagulation and precipitation, significantly improving the impurity removal effect of subsequent critical vacuum air flotation. Simultaneously, it inhibits the growth of miscellaneous bacteria, reduces wastewater putrefaction and odor, ensures the stability of organic components, and creates suitable conditions for the preparation of high-purity carbon sources.

[0047] Furthermore, in a preferred embodiment, in step c), the alkali agent is sodium aluminate.

[0048] Sodium aluminate, while adjusting pH, has an excellent flocculation effect as its hydrolysis product, aluminum hydroxide. This can synergistically remove some suspended solids and phosphates from water, significantly improving the effect of secondary impurity removal and thus reducing the risk of fouling in subsequent MVR units.

[0049] Furthermore, in a preferred embodiment, in step d), the temperature of the wastewater after heating treatment is 63°C to 67°C, and more preferably 65°C.

[0050] In practice, when the wastewater pH or temperature is low, the conversion and stripping efficiency of ammonia nitrogen decreases significantly; while when the wastewater pH or temperature is high, although the efficiency may improve slightly, the consumption of reagents and energy increases dramatically, leading to poor economic efficiency. Therefore, it is necessary to control the process parameters within the optimal range in order to achieve a high ammonia nitrogen removal rate at a lower cost.

[0051] In this embodiment, the pH of the wastewater is adjusted to 11.8–12.2, and the heating temperature is 63°C–67°C. This is an optimal implementation range for the method of this invention. Under this precise parameter control, the conversion rate of free ammonia and the stripping kinetics are optimally matched, achieving the highest ammonia nitrogen removal rate (up to 95% or more) in the shortest time, while avoiding side reactions such as organic matter degradation that may be caused by excessive alkalization or heating. By adopting this optimal parameter combination, a carbon source product with low ammonia nitrogen residue and high quality can be prepared with a high cost-effectiveness ratio.

[0052] Furthermore, in a preferred embodiment, in step d), the critical vacuum flotation system removes small scum from the wastewater and strips ammonia-containing waste gas from the wastewater by critical vacuum flotation after heating, resulting in organic wastewater; the small scum and ammonia-containing waste gas are the waste gas and waste residue generated in step d).

[0053] Wastewater is treated using a heated critical vacuum flotation system. This system efficiently removes residual fine scum under vacuum flotation conditions, achieving deep impurity removal and producing clear, clean organic wastewater. This ensures the purity and stability of the subsequent carbon source preparation. Simultaneously, in a high-temperature and strongly alkaline environment, ammonia nitrogen in the wastewater is stripped through the flotation process, effectively separating ammonia-containing waste gas. This reduces the ammonia nitrogen content in the organic wastewater and improves the quality of the final carbon source product. The resulting small scum and ammonia-containing waste gas are collected and treated together as waste gas and residue, preventing pollutant diffusion and laying the foundation for subsequent harmless and resource-based utilization.

[0054] Furthermore, in a preferred embodiment, in step d), the time for entering the critical vacuum air flotation system for processing is 13~17 minutes.

[0055] In this embodiment, the wastewater is treated in a critical vacuum flotation system for 13-17 minutes. This ensures sufficient flotation contact and stripping time, allowing for the complete separation of fine scum and effective removal of ammonia-containing waste gas, thus guaranteeing deep impurity removal and ammonia removal. At the same time, it avoids excessive residence time, which would lead to loss of organic carbon source and increased energy consumption. This achieves an optimal balance between treatment effect and operating efficiency, providing stable and qualified organic wastewater for the subsequent preparation of high-concentration organic carbon source.

[0056] Furthermore, in a preferred embodiment, in step e), the ammonia in the ammonia-containing waste gas is recovered and reused through acid washing, other remaining odorous gases are treated through an absorption tower, and small scum is composted aerobically.

[0057] In this embodiment, ammonia-containing waste gas is recovered through acid washing, which converts ammonia nitrogen in the wastewater into ammonium salt products for resource recovery and utilization, improving resource utilization efficiency. The remaining odorous gases are treated by an absorption tower, which effectively degrades malodorous substances, preventing odor diffusion and air pollution, and ensuring that the waste gas meets emission standards. Small scum is disposed of through aerobic composting, converting organic waste into organic fertilizer or soil conditioner, achieving solid waste resource utilization. Simultaneously, harmless treatment prevents secondary pollution, making the entire process more environmentally friendly and economical, meeting the requirements for resource utilization and green, low-carbon treatment of kitchen wastewater.

[0058] Furthermore, in a preferred embodiment, in step e), the concentration treatment is to concentrate the organic wastewater using an MVR device to obtain high-concentration organic wastewater.

[0059] The use of MVR (Mechanical Vapor Reduction) devices for the concentration of organic wastewater can efficiently evaporate water from the wastewater, significantly increasing the COD concentration and carbon source content of the organic wastewater, and obtaining high-concentration organic wastewater that meets the requirements for subsequent blending. At the same time, the MVR device has high thermal energy utilization and low energy consumption, and can achieve low-carbon and efficient concentration without destroying organic components. This provides substrates with qualified concentrations for the subsequent preparation of high-concentration, high-quality organic carbon sources, thereby improving the utilization efficiency of the final carbon source product.

[0060] In this embodiment, the fixed process sequence of "anaerobic ammoniation → strong alkali adjustment → heating flotation" in the process method for preparing carbon sources from kitchen wastewater cannot be reversed or omitted. Its necessity and synergistic effect are as follows: In the pretreated kitchen wastewater, there is a high proportion of macromolecular organic matter such as proteins and polysaccharides. Ammonia nitrogen mainly exists in a bound state and cannot be effectively removed directly by strong alkali and air flotation. If anaerobic ammoniation is omitted and strong alkali heating and air flotation are carried out directly, most of the ammonia nitrogen will be wrapped inside the organic colloids and particles, resulting in a low conversion rate of free ammonia nitrogen and a significant decrease in removal efficiency.

[0061] Anaerobic ammoniation (2-3 hours) can hydrolyze large organic molecules into small volatile fatty acids (VFA), while simultaneously releasing bound nitrogen into free ammonium ions (NH4+). + This provides a substrate for efficient conversion in subsequent deammoniation; strong base adjustment adjusts the pH to 11.8-12.2, allowing NH4+ to be efficiently converted. + It is completely converted into gaseous free ammonia (NH3) and destroys the stability of colloids and oils; heating to 63~67℃ reduces the solubility of NH3, and combined with critical vacuum flotation to achieve gas-liquid mass transfer and stripping, the three form a strong synergistic effect.

[0062] By comparing experimental data, the same batch of kitchen wastewater (initial ammonia nitrogen 2860 mg / L) was used to set up an experimental group (undergoing anaerobic ammoniation for 2-3 hours) and a control group (without anaerobic steps). The data results are as follows:

[0063] Experimental results show that anaerobic ammoniation creates a unique chemical environment with high free ammonia and low colloidal resistance for subsequent strong alkali-heated flotation, making the ammonia nitrogen stripping efficiency much higher than that of processes without anaerobic steps, while maximizing the retention of organic carbon sources.

[0064] Meanwhile, compared with conventional MVR that only concentrates kitchen wastewater (without mixing and blending), the advantages of the organic carbon source obtained by this invention are as follows:

[0065] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0066] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A process for preparing a carbon source from kitchen wastewater, characterized in that, Includes the following steps: a) Pre-treat untreated high-concentration kitchen wastewater to remove large impurities or sediments; b) Anaerobic ammoniation treatment of pretreated kitchen wastewater; c) Add an alkaline agent to the wastewater after it has undergone sufficient anaerobic ammoniation treatment to adjust the pH of the wastewater to a strongly alkaline state; d) After pH adjustment, the wastewater is heated and then enters the critical vacuum flotation system for secondary impurity removal. e) The waste gas and waste residue generated in step d) are treated in a harmless manner and utilized for resource recovery; and the organic wastewater generated in step d) is concentrated and then mixed with acetic acid, methanol and sodium acetate to obtain a high-concentration organic carbon source.

2. The process for preparing a carbon source from kitchen wastewater according to claim 1, characterized in that, In step b), the pretreated kitchen wastewater is sent to an anaerobic digester for ammoniation for 2-3 hours.

3. The process for preparing a carbon source from kitchen wastewater according to claim 1, characterized in that, In step c), the pH of the wastewater is adjusted to a strongly alkaline range of 11.8 to 12.

2.

4. A process for preparing a carbon source from kitchen wastewater according to claim 1 or 3, characterized in that, In step c), the alkaline agent is sodium aluminate.

5. The process for preparing a carbon source from kitchen wastewater according to claim 1, characterized in that, In step d), the temperature of the wastewater after heating treatment is 63℃~67℃.

6. The process for preparing a carbon source from kitchen wastewater according to claim 5, characterized in that, In step d), the temperature of the wastewater after heating treatment is 65℃.

7. A process for preparing a carbon source from kitchen wastewater according to claim 1 or 5, characterized in that, In step d), the critical vacuum flotation system removes small scum from the wastewater and strips ammonia-containing waste gas from the wastewater by using a heated critical vacuum flotation method to obtain organic wastewater.

8. The process for preparing a carbon source from kitchen wastewater according to claim 7, characterized in that, In step d), the time for entering the critical vacuum air flotation system for processing is 13~17 minutes.

9. The process for preparing a carbon source from kitchen wastewater according to claim 7, characterized in that, In step e), ammonia in the ammonia-containing waste gas is recovered and reused through acid washing, other remaining odorous gases are treated through an absorption tower, and small scum is composted aerobically.

10. The process for preparing a carbon source from kitchen wastewater according to claim 1, characterized in that, In step e), the concentration treatment involves using an MVR device to concentrate the organic wastewater.

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