A system and method for the pretreatment of slaughter and food industry wastewater

Abstract

The application provides a slaughter and food industry wastewater pretreatment system and method, which comprises a first adjusting unit, a second adjusting unit, a gas floatation unit and a sludge storage unit. The wastewater is preliminarily mixed in the first adjusting unit to avoid impacting the process section, and then directly enters the second adjusting unit without oil separation treatment process, is fully homogenized and treated by hydrolysis, and then is lifted to separate the wastewater into solid and liquid by the gas floatation process. The pretreatment process of the slaughter and food industry wastewater treatment plant is optimized, the biodegradability of the wastewater after pretreatment is improved, and good conditions are provided for subsequent treatment. The wet sludge treatment path after skimming of the traditional oil separation tank is optimized, all the wet sludge is concentrated in the sludge storage unit, the output of the high-water-content wet sludge is reduced, the existing pretreatment system process is simplified, the operation pressure of the pretreatment process is reduced, the operation efficiency of the wastewater treatment plant is improved, and the concentration of the wet sludge provides a solution for realizing sludge resource utilization.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and in particular relates to a pretreatment system and method for slaughtering and food processing industrial wastewater. Background Technology

[0002] For the pretreatment process of wastewater from slaughtering and food processing industries, the core process usually adopts "oil separator - equalization tank - air flotation tank". The overall concept of this process is to treat the solid matter in the wastewater in two parts: first, the oil separator process is used to isolate and collect large pieces of oil and fine suspended solids in the wastewater and transport them off-site for secondary treatment; second, the remaining solid matter is separated by air flotation process, and after separation, it is dried by the plant's dewatering equipment and then transported off-site. The above-mentioned process has the following shortcomings: First, its processing capacity is limited. While the process primarily targets floating oil and larger suspended solids (such as floating oil and meat scraps), its effectiveness is limited for solids such as large amounts of emulsified oil, dissolved oil, and fine suspended solids (such as hair and feathers). These unremoved pollutants adhere to the equipment in the subsequent biological treatment system, causing blockages and inhibiting microbial activity. Furthermore, due to the unsatisfactory treatment effect of the above-mentioned process, the treated wastewater's various indicators are difficult to meet the requirements of the biological treatment process, affecting its operation and potentially leading to substandard effluent. Second, the solid matter separated from the oil separator has a water content of over 90%. This makes transportation inconvenient, requiring specialized equipment for off-site transport, and its disposal is also cumbersome, necessitating the search for a disposal site and incurring high treatment costs. Third, the process route is complex and maintenance is cumbersome. Because the above process involves two separation paths for solid matter, additional maintenance personnel are needed for daily operation and maintenance, increasing the workload of the treatment plant. In summary, the above-mentioned processes have significant limitations when dealing with the complex industrial wastewater generated by modern slaughtering and food processing. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a pretreatment system and method for slaughtering and food processing industrial wastewater to overcome the shortcomings of the prior art.

[0004] To achieve the above objectives, the present invention is implemented through the following technical solution: On the one hand, a pretreatment system for industrial wastewater from slaughtering and food processing is provided, comprising a primary regulating unit, a secondary regulating unit, and an air flotation unit connected in series, wherein: The primary regulating unit, a liquid-holding tank equipped with a homogenizing agitator, is located at the rear end of the bar screen process. It completely mixes the wastewater from various enterprises after the bar screen treatment and initially homogenizes the grease, suspended solids and other solids in the wastewater with the wastewater, ensuring that solid-liquid separation does not occur in the tank. The secondary regulation unit, with a liquid-holding tank equipped with a pusher agitator, fully homogenizes and mixes the wastewater from different factories in the industrial park and carries out a hydrolysis reaction. The hydrolysis reaction is a complete mixing type, in which activated sludge is evenly distributed in the wastewater. The activated sludge is separated and treated in the subsequent air flotation unit along with the wastewater. The dissolved air flotation unit includes a dissolved air system, a bubble release system, and a chain plate scraper. The dissolved air system forms dissolved air water, and the bubble release system releases the air from the dissolved air water delivered to the flotation tank into the wastewater. This causes a large number of dispersed microbubbles to rise to the surface of the wastewater and form a scum layer. The chain plate scraper then performs surface skimming to achieve solid-liquid separation.

[0005] Furthermore, the pretreatment system for slaughtering and food processing industrial wastewater also includes a sludge storage unit, which includes a sludge storage tank. The sludge storage tank temporarily stores the wet sludge separated by air flotation screening, awaiting subsequent dewatering and drying treatment.

[0006] Furthermore, in the aforementioned pretreatment system for slaughtering and food processing industrial wastewater, the primary regulating unit, secondary regulating unit, air flotation unit, and sludge storage unit are all integrated into a single unit and can be modularized.

[0007] On the other hand, a method for pretreatment of industrial wastewater from slaughtering and food processing is provided, comprising: S1: After passing through the bar screen process, the water enters the primary regulating unit and is mixed by a homogenizer to reach a stable state. The wastewater retention time is not less than 1 hour. The mixed wastewater is then lifted and transported to the secondary regulating unit. S2: Wastewater entering the secondary regulation unit is thoroughly homogenized and mixed in the tank. After deep mixing, the wastewater is stirred by a flow mixer and undergoes hydrolysis. The wastewater retention time is no less than 8 hours. After hydrolysis, the wastewater is lifted and enters the air flotation unit. S3: In the air flotation unit, the wastewater is transformed into dissolved air water through the dissolved air system. Then, the air in the dissolved air water transported to the air flotation tank is released into the wastewater through the bubble release system, which generates a large number of dispersed microbubbles in the wastewater, causing the solid matter in the wastewater to float to the surface and form a scum layer. The surface scum is then skimmed off by a chain plate scraper to achieve solid-liquid separation. S4: The solid sludge separated by the air flotation unit is transported to the sludge storage tank for temporary storage.

[0008] The beneficial effects of the technical solution of this invention are: 1. By connecting primary control unit, secondary control unit, and air flotation unit in series, the efficiency of air flotation treatment process is improved, the oil content can be reduced to below 50 mg / L, the total phosphorus removal rate can reach 85%, and the ammonia nitrogen concentration can be reduced by 27%; 2. By eliminating the oil separator process and setting up primary and secondary regulating units, the operation and maintenance of the pretreatment process section is simplified, saving 1 to 2 operating personnel. 3. The wet sludge separated by the original oil separator has a high water content, few receiving units, and high treatment costs. All the wet sludge can be concentrated in the sludge treatment workshop on-site for treatment, thereby reducing treatment costs. 4. This pretreatment system achieves solid-liquid mixing of wastewater in both the primary and secondary regulating units, thereby reducing the solid waste treatment process in the pretreatment stage. Solid-liquid separation is completed in one step in the flotation unit, and all solid waste is finally concentrated in one place, simplifying the process flow. 5. The aforementioned solid wastes are characterized by high organic matter content and low toxicity. This pretreatment system collects solid wastes in one place, which can provide a good prerequisite for the resource utilization of such solid wastes.

[0009] In summary, this invention can adjust the B / C ratio of wastewater, enhance the biodegradability of raw water, and provide favorable conditions for subsequent wastewater treatment. The centralized processing of wet sludge provides a solution for the resource utilization of sludge. At the same time, the above functions do not require additional material input or new equipment, and the method is simple and efficient. Attached Figure Description

[0010] To further illustrate the above-mentioned objectives, structural features, and effects of the present invention, the present invention will be described in detail below with reference to the accompanying drawings.

[0011] Figure 1 This is a schematic diagram of the overall system of a preferred embodiment of the present invention; In the diagram: 1. Primary regulating unit; 101. Agitator; 102. First lift pump; 2. Secondary regulating unit; 201. First jet mixer; 202. Second lift pump; 3. Air flotation unit; 301. Dissolved air system; 302. Bubble release system; 303. Chain plate scraper; 4. Sludge storage tank; 401. Second jet mixer. Detailed Implementation

[0012] The terms “invention” and “the present invention” used in this specification are intended to broadly refer to all subject matter of this specification and any of the following patent claims. Statements containing these terms should not be construed as limiting the subject matter described herein or limiting the meaning or scope of any of the following patent claims. Furthermore, this specification does not attempt to describe or limit the subject matter covered by any claim of any particular component, paragraph, statement, or drawing of this application. The subject matter should be understood with reference to the entire specification, all drawings, and any of the following claims. The invention may have other embodiments and be practiced or implemented in other ways. Moreover, it should be understood that the wording and terminology used herein are for illustrative purposes and should not be considered limiting.

[0013] The details of the invention will now be discussed with reference to the accompanying drawings, which are illustrated by way of example only. In the drawings, similar features or components may be labeled using the same reference numerals.

[0014] The use of the terms "comprising," "having," and "including," and variations thereof, herein means to include the items listed herein and their equivalents and additional items. While reference may be made in the description of the drawings to directions such as above, below, upward, downward, backward, bottom, top, front, rear, etc., for convenience, reference is made relative to the drawings. These directions are not intended to literally accept or limit the invention in any form. Furthermore, terms such as "first," "second," "third," etc., are used herein for illustrative purposes and are not intended to indicate or imply importance or significance.

[0015] See Figure 1 As shown, the present invention provides a pretreatment system for industrial wastewater from slaughtering and food processing, comprising a primary regulating unit 1, a secondary regulating unit 2, an air flotation unit 3, and a sludge storage unit 4 connected in series.

[0016] The primary regulating unit 1 is located downstream of the bar screen process. Wastewater treated by the bar screen directly enters the primary regulating unit 1. Its main functions are to regulate the influent flow, balance water quality fluctuations, and prevent hydraulic load from impacting subsequent units. Simultaneously, the mechanical agitator 101 prevents the sedimentation of settleable solids (such as meat scraps and dough) and initially breaks down larger suspended solids. Specifically, the primary regulating unit 1 is a single water-holding unit, which can be divided into an even number of sub-unit zones according to the water volume. The sub-units are evenly and symmetrically arranged within the regulating unit. The agitator 101 is a vertical low-speed paddle mixer made of 304 stainless steel with a power configuration of 3.0 kW. The number of units installed is determined according to the tank volume, generally one unit per 50-80 m³ of tank volume, evenly distributed within the tank. Preferably, four first lift pumps 102 are installed, arranged symmetrically in pairs within the primary regulating unit 1. The first lift pumps 102 are adjacent to the secondary regulating unit 2 and are corrosion-resistant submersible sewage pumps with a flow rate of 500 m³. 3 The pump operates at a speed of 100 km / h with a head of 30 m. Operation is automatically controlled (start / stop or frequency conversion) by the liquid level signal from the secondary regulating unit 2. The agitator 101 operates continuously to maintain a stable wastewater condition, and the first lift pump 102 delivers the wastewater to the secondary regulating unit 2.

[0017] Secondary regulation unit 2 is the core component of this system for solid-liquid separation. It requires no functional zoning and its core function is to perform advanced water quality and quantity regulation, and to achieve complete mixing and hydrolysis of wastewater within the unit. This decomposes large organic molecules in the wastewater into smaller, more easily biodegradable organic molecules, improving the wastewater's biodegradability (BOD / COD value). Simultaneously, hydrolytic microorganisms (flocs) are formed and uniformly dispersed in the water during this process. Specifically, the effective volume is designed and calculated based on an 8-12 hour hydraulic retention time for the maximum daily flow rate of the treatment system to ensure sufficient regulation and reaction time. A first flow-pushing agitator 201, with a power of 5.0 kW, is uniformly and symmetrically installed within the tank, creating a unidirectional, uniform flow of water within the tank, achieving rapid mixing and homogenization, maintaining sludge suspension within the tank, enhancing the mass transfer process, and promoting the hydrolysis reaction. The system preferably uses 10 primary agitators 201, each with a power of 10.0 kW, operating continuously. The pH value is naturally maintained within the range of 5.5 to 6.5 to create a suitable hydrolysis reaction environment. The mixed liquor suspended solids (MLSS) concentration is maintained at approximately 4000 mg / L, and the wastewater retention time is no less than 8 hours. Specifically, two secondary lift pumps 202 are equipped, with a flow rate of 500 m³ / h and a head of 30 m, and are arranged symmetrically in pairs within the secondary regulating unit 2. The secondary lift pumps 202 are located adjacent to the flotation unit 3, transporting the treated wastewater to the flotation unit 3. The operation of the lift system, i.e., the secondary lift pumps 202, is controlled by the liquid level in the reaction zone of the flotation unit 3 or by the system flow meter signal.

[0018] Referring again to the diagram, flotation unit 3 is the key component for solid-liquid separation in this system. Specifically, a rectangular dissolved air flotation tank is used, which can be divided into an even number of sub-units based on the water volume. Each sub-unit has the same system and function, with a total hydraulic retention time of 20-30 minutes. It includes a dissolved air system 301, a bubble release system 302, and a chain-plate scraper 303. The dissolved air system 301 generates dissolved air water, and the bubble release system 302 releases the air from the dissolved air water into the wastewater, causing a large number of dispersed microbubbles to rise to the surface and form a scum layer. The dissolved air system 301 operates at a pressure of 0.5 MPa. The chain-plate scraper 303 is installed at the top of the flotation tank for continuous or intermittent scraping of scum. The scraper's travel speed can be adjusted within the range of 1-3 m / min. The resulting scum is separated into solid and liquid by a chain-plate scraper 303, and then flows by gravity to the sludge storage unit 4. The separated wastewater is collected through the bottom water collection pipe and enters the subsequent biological treatment system.

[0019] Sludge storage unit 4 is an independent sludge storage tank (sludge tank) used to temporarily collect and store scum generated from flotation unit 3. This unit does not require functional zoning; its function is to store and adjust the properties of sludge, providing a stable and continuous feed to the existing sludge dewatering and drying equipment in the plant. A second flow mixer 401 is installed in the tank to adjust the properties of the sludge, and the uniformly mixed sludge can then be pumped to the dewatering and drying equipment.

[0020] The entire pretreatment system can be integrated into a closed or semi-closed structure, which is conducive to the collection and treatment of any odorous gases that may be generated. The system can be centrally and automatically controlled by monitoring the above-mentioned main parameters to ensure stable and efficient operation. Centralized wet sludge provides a solution for realizing the resource utilization of sludge.

[0021] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A pretreatment system for industrial wastewater from slaughtering and food processing, characterized in that, It includes a primary regulating unit, a secondary regulating unit, and an air flotation unit connected in series, wherein: The primary regulating unit, a liquid-holding tank equipped with a homogenizing agitator, is located at the rear end of the bar screen process. It completely mixes the wastewater from various enterprises after the bar screen treatment and initially homogenizes the grease, suspended solids and other solids in the wastewater with the wastewater, ensuring that solid-liquid separation does not occur in the tank. The secondary regulation unit, with a liquid-holding tank equipped with a pusher agitator, fully homogenizes and mixes the wastewater from different factories in the industrial park and carries out a hydrolysis reaction. The hydrolysis reaction is a complete mixing type, in which activated sludge is evenly distributed in the wastewater. The activated sludge is separated and treated in the subsequent air flotation unit along with the wastewater. The dissolved air flotation unit includes a dissolved air system, a bubble release system, and a chain plate scraper. The dissolved air system forms dissolved air water, and the bubble release system releases the air from the dissolved air water delivered to the flotation tank into the wastewater. This causes a large number of dispersed microbubbles to rise to the surface of the wastewater and form a scum layer. The chain plate scraper then performs surface skimming to achieve solid-liquid separation.

2. The pretreatment system for slaughtering and food processing industrial wastewater according to claim 1, characterized in that, It also includes a sludge storage unit, which includes a sludge storage tank. The sludge storage tank temporarily stores the wet sludge separated by air flotation screening, waiting for subsequent dewatering and drying treatment.

3. The pretreatment system for slaughtering and food processing industrial wastewater according to claim 2, characterized in that, The primary regulation unit, secondary regulation unit, air flotation unit, and sludge storage unit are all integrated into a single unit and can be modularized.

4. A method for pretreatment of industrial wastewater from slaughtering and food processing, characterized in that, include: S1: After passing through the bar screen process, the water enters the primary regulating unit and is mixed by a homogenizer to reach a stable state. The wastewater retention time is not less than 1 hour. The mixed wastewater is then lifted and transported to the secondary regulating unit. S2: Wastewater entering the secondary regulation unit is thoroughly homogenized and mixed in the tank. After deep mixing, the wastewater is stirred by a flow mixer and undergoes hydrolysis. The wastewater retention time is no less than 8 hours. After hydrolysis, the wastewater is lifted and enters the air flotation unit. S3: In the air flotation unit, the wastewater is transformed into dissolved air water through the dissolved air system. Then, the air in the dissolved air water transported to the air flotation tank is released into the wastewater through the bubble release system, which generates a large number of dispersed microbubbles in the wastewater, causing the solid matter in the wastewater to float to the surface and form a scum layer. The surface scum is then skimmed off by a chain plate scraper to achieve solid-liquid separation. S4: The solid sludge separated by the air flotation unit is transported to the sludge storage tank for temporary storage.

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