150m3/D slaughter wastewater treatment 

Chapter 1 Project Overview

First, the project name
Slaughterhouse Wastewater Treatment Project

Second, the design unit
Shandong Jixu Environmental Engineering Co., Ltd.

Third, the project overview
A certain amount of wastewater will be produced during the slaughter process. The wastewater mainly comes from wastewater after slaughter, disintegration, visceral washing and surface washing, and fecal wastewater. Wastewater contains a large amount of organic matter, the main components: animal manure, blood, animal viscera, poultry, minced meat and oil and other organic matter, belonging to high concentration of organic wastewater. The wastewater is brownish red with a strong odor. The fat, protein and other substances in these wastewaters are not treated and discharged directly into the water body, which will cause serious eutrophication of the surrounding water bodies, seriously destroying the self-sufficiency of the water bodies, causing the water body to become black and smell, affecting the environment and agricultural irrigation. For the normal production and sustainable development, the slaughterhouse protects the surrounding water environment, attaches great importance to the problem of wastewater pollution, and is determined to treat the wastewater and entrust our company to formulate a treatment plan. Based on the wasteland properties and emission requirements of the slaughterhouse, our company adopts advanced wastewater treatment technology and equipment from the goal of reducing the cost and operating cost of sewage treatment projects. Based on this principle, this governance plan document has been drawn up for the review of the leaders of enterprises and relevant departments.

Chapter II Design Water Quality and Treatment Requirements

First, the design of water
According to the owner's requirements, the daily sewage treatment capacity is 150m3/d, and the daily wastewater volume is 7.5m3/h according to 20 hours.
Second, the influent water quality indicators
According to the water quality data provided by Party A, refer to the water quality characteristics of wastewater in the same industry as a reference to determine the design wastewater quality as follows:
project

Chapter III Sewage Treatment System Process

First, the design principle

a Sewage treatment system design principles

1. Conscientiously implement the national guidelines and policies on environmental protection work, so that the design conforms to relevant national laws, regulations, and standards.
2. Comprehensively consider the characteristics of wastewater quality and quantity of water, and the selected process technology is advanced, reliable, economical, flexible, safe and applicable.
3. The layout of the sewage treatment system is compact, reducing land occupation and investment.
4. Properly dispose of sludge and other grid slag and sediments generated during the sewage treatment process to avoid secondary pollution.
5, automatic control in the sewage treatment process, and strive to manage convenient, safe and reliable, economical and practical.
6. The layout of the elevation should be as large as possible to make full use of the underground space. The layout should be compact to save land.
7. Designed in strict accordance with the conditions defined by the factory to meet the actual requirements of the project.

b mud treatment system design principles

1. The sludge produced by the system is transported to the landfill after being concentrated and dehydrated.
2. Process design minimizes system sludge production.
Second, the analysis of wastewater properties and the determination of process routes

2.1 Analysis of wastewater properties
Slaughter wastewater contains a large amount of pollutants such as blood, oil and grease, hair, meat, bone chips, internal organs, undigested food and feces, with unpleasant blood red and bloody smell. .
Slaughter wastewater is a high-concentration organic polluted wastewater with complex composition. Slaughter wastewater has the following characteristics:
1, with a certain blood red, mainly caused by blood;
2, has a bloody smell, mainly caused by chicken blood and protein decomposition;
3, containing a large amount of suspended matter, mainly formed by chicken duck feathers, meat chips, bone chips, internal organs, undigested food and feces;
4. Contains higher animal fats;
5. Contains a large number of E. coli populations.

According to the characteristics of the wastewater and the requirements for the treatment of the effluent, it is necessary to use the physicochemical + biochemical treatment process for the wastewater treatment process. When the CODcr and the chromaticity of the wastewater are high, when the concentration of the oil in the wastewater exceeds 40 mg/l, the oil adheres to the surface of the biofilm, blocking the contact of the wastewater with the biofilm, and the biochemical removal efficiency is lowered; the large amount of hair and meat contained in the wastewater , bone chips, visceral sundries, undigested food and feces are also not easy to biochemical, so the wastewater must take the necessary pre-treatment and physicochemical treatment to minimize the suspended solids and oil content entering the biological treatment structure, and then carry out biochemical treatment. To ensure the normal operation of biochemical treatment. In addition to high concentration and high chroma, slaughter wastewater also contains ammonia nitrogen, which is more difficult to handle. Therefore, their removal should be considered in the design process.

2.2 Process route analysis
According to the characteristics of the wastewater and the requirements for treating the effluent, it is necessary to use the physicochemical + biochemical treatment + filtration and disinfection process for the wastewater treatment process. The COD and chroma of wastewater are high, mainly due to the high concentration of feces in wastewater. The presence of a large amount of manure affects the treatment of subsequent sewage, which reduces the biochemical removal rate. The wastewater contains a lot of hair, residual feed, and impurities. Therefore, the wastewater must be subjected to necessary pretreatment and physicochemical treatment to minimize the suspension of the biological treatment structure and then carry out the normal operation of the biochemical treatment.

2.3 Wastewater pretreatment
Pretreatment of slaughter wastewater is the key to the efficient operation of the entire system. The suspended solids (SS) in the wastewater is as high as 200-1000 mg/L. The suspended solids are perishable organic substances and must be intercepted before entering the treatment system to prevent clogging of subsequent pipelines and equipment and prolong the service life of the equipment. At the same time, the suspended solid organic matter can be prevented from becoming a dissolved organic matter, resulting in an increase in the concentration of CODcr and BOD5 in the wastewater.

There are many common pretreatment methods, including: filtration, grit, sedimentation, coagulation and sedimentation, conditioning, and air flotation. Taking into account the water quality characteristics of the project, the pretreatment process uses a combination of a grid, a solid-liquid separator, a conditioning tank, and an air flotation machine.

The wastewater first enters the treatment system through the grid. The grid can remove the larger particle size suspended matter, floating matter, hair, and other impurities in the wastewater. The effluent enters the grease trap, and the grease trap can adjust the water volume and water quality. The oil can be removed. The effluent from the grease trap is lifted by a lift pump to a solid-liquid separator, which is a mechanical filtration method. It is suitable for separating the micro-suspended substances (slurry, fiber, feces) existing in the liquid to the maximum to achieve the separation of solid and liquid phases. The difference between solid-liquid separation and other methods is that the filter medium has a particularly small gap, and with the centrifugal force of the screen rotation, at a lower hydraulic resistance, the flow rate is higher, and the suspended solids are trapped.

This equipment is specially developed for the problems that the existing microfiltration machine is easy to block, easy to break, large maintenance and maintenance work, and more secondary investment. It is one of the best practical equipments for wastewater treatment.

This equipment is a new solid-liquid separator developed by absorbing New Zealand Wanquan technology and aiming at China's national conditions. It is widely used in various occasions where solid-liquid separation is required, such as filtration of urban domestic sewage, papermaking, food, textile, printing and dyeing, and chemical sewage.

After treatment by the solid-liquid separator, the suspended matter in the wastewater is greatly reduced, which creates conditions for subsequent processing. The slag from the solid-liquid separator enters the slag pool, and the effluent enters the sump, and the sump is pumped into the high-efficiency air flotation machine.

The air floatation adopts a unified air flotation device, which is composed of a pool body, a dissolved gas tank, an air compressor and a return water pump, and is controlled by an electric control box. There is a large amount of fine suspended solids and oil in the waste water. The concentration of the above pollutants can be greatly reduced by the treatment of the air flotation device. When the air flotation equipment is working, the high-molecular flocculant is added, and the wastewater enters the air flotation machine after the drug addition reaction, and The bubbles released by the release device are thoroughly mixed and contacted, so that the flocs in the water adhere to the microbubbles, and the average diameter of the released bubbles is about 30 um, and the flocs float to the surface to form scum, and after the scum gathers to a certain thickness, the scum is scraped. The machine scrapes into the air floating mud channel and sends it to the sludge concentration tank. A part of the clean water in the lower layer of the air flotation machine is pumped for the dissolved gas water through the dissolved gas pump, and the remaining clean water enters the subsequent processing unit through the overflow pipe. Air floatation removes 80-90% of suspended solids and 40-70% of CODcr. At the same time, due to the addition of a coagulant in the flotation cell, it reacts with the phosphate in the wastewater to form a salt which is more difficult to dissolve in water, thereby better removing the phosphorus in the wastewater and reducing the subsequent phosphorus removal unit. load.

2.4 Selection of secondary treatment process

2.4.1 Selection of anaerobic part process
The organic matter in the slaughter wastewater is mainly protein and fat, which is difficult to be directly used by general aerobic bacteria. In the process of biodegradation, it is generally decomposed into small molecular organic substances such as amino acids and carbohydrates by the action of enzymes, and then can be aerobic. Direct use of bacteria. In addition, the concentration of pollutants in the wastewater is high, and directly removing all the organic materials by the aerobic process will consume a large amount of electric energy, which will inevitably increase the operating cost of the system. In order to save operating costs, it is very important to choose a process that requires both good processing and operating costs. The anaerobic processes commonly used in slaughter wastewater treatment have complete anaerobic and incomplete anaerobic hydrolysis hydrolysis acidification, which is the main stage of complete anaerobic. The complete anaerobic process is divided into four stages: hydrolysis, acidification, acetic acid production and methanogenesis. In the hydrolysis stage, the macromolecular organic matter is decomposed by bacterial extracellular enzymes into small molecular substances that can be dissolved in water and can penetrate the cell membrane; in the acidification stage, the hydrolyzed small molecular substances are converted into simpler compounds in the cells of the acidified bacteria. And secreted to the outside of the cell; in the acetic acid production stage, the product of the hydrolysis and acidification stage is further converted into acetic acid, hydrogen, carbon dioxide and new cellular substances by the acetogen; in the methanation stage, the acetic acid, hydrogen, carbonic acid produced in the acetic acid production stage Formic acid, methanol, etc. are converted to methane, carbon dioxide, and new cellular materials. The complete anaerobic process has the advantages of high volumetric load, obvious removal effect, strong impact resistance, strong methanogen activity and high sludge concentration. However, the conditions of the complete anaerobic process are relatively strict. For example, the wastewater needs to reach a certain temperature (middle temperature digestion is 35-38 ° C), the pH value in the reactor must be kept at a certain level, and there must be an effective three-separator. It has granular sludge or high concentration anaerobic sludge. At the same time, a large amount of biogas is generated in the process of complete anaerobic reaction. For the type of wastewater in this project, the biogas generated has odor, corrosiveness and explosiveness. If it is poorly managed and handled, it will endanger the management personnel and surrounding residents. Safety.

The hydrolysis acidification process is the most widely used form in the treatment of high-concentration organic wastewater. By controlling the hydraulic retention time and the concentration of dissolved oxygen in the water, the anaerobic process of the organism is controlled in the hydrolysis and acidification stage, and no acetic acid or production is required. The methane phase, which shortens the progress and time of the reaction. Its main advantage is that it can remove more organic matter, degrade the material with large molecular weight and long carbon chain, improve the biodegradability of the influent water, and at the same time, because it does not enter the methanogenic stage, it has lower requirements on environmental conditions and can resist certain The impact load of water quality and water quantity, while the hydrolysis acidification reaction can occur under anaerobic and anoxic conditions, and the structural form of the reaction tank is required to be low. Hydrolysis acidification is to control the anaerobic process in the hydrolysis and acidification stage. Therefore, the residence time of the hydrolysis acidification reaction tank is short, and the dominant bacteria in the reaction tank are hydrolysis acidification bacteria, and a few are acetic acid bacteria and methanogens. In addition, the hydrolysis acidification process does not enter the methanogenic stage, and a small amount of gas generated can be directly discharged into the atmosphere without a significant impact on the human body and the surrounding environment.

Therefore, from the perspectives of stable operation, convenient management, safety and economy, the hydrolysis acidification process is superior to the complete anaerobic process.

2.4.2 Selection of aerobic part process
After the organic wastewater treatment of the project, it meets the first-level standard of the Comprehensive Emission Standard (GB18918-2002). Finally, the aerobic biological treatment process is the most commonly used, most effective, and the lowest operating cost. For slaughter and meat processing wastewater, there are many aerobic biological treatment processes at home and abroad, such as A2O, SBR, and contact oxidation. The advantages and disadvantages of several methods are compared to determine the processing technology suitable for this project.

The A2O process is an anaerobic-anoxic-aerobic process. The biological treatment structure of the process is divided into three parts, namely an anaerobic tank, an anoxic tank and an aerobic tank, and different dominant flora are grown in the three pools respectively. Different pollutants are removed separately, and the removal efficiency is relatively high. At the same time, the sludge is not easily expanded due to the anaerobic, anoxic and aerobic conditions. However, the A2O process requires two sets of sludge return systems between the aerobic tank and the anoxic tank and the secondary settling tank and the anaerobic tank to realize the nitrogen and phosphorus removal of the wastewater, and the required equipment and maintenance work are required. Big. At the same time, the sludge of the A2O process has a low organic load and a large volume of the tank.

The SBR process is a batch activated sludge system whose basic feature is the removal of different organics at different times in the same reaction cell. The operation of a single SBR pool includes five basic processes of influent, reaction, sedimentation, effluent and idle, and the cycle is repeated. The process does not need to set up a second settling tank and sludge returning equipment, and the process flow is simple and the treatment effect is good. However, since the water level of the SBR reaction tank is not constant, the volume utilization rate of the reaction tank is low. When several SBR reaction tanks are operated in parallel, each reaction tank acts as a regulating tank, an aeration tank and a sedimentation tank at different times, and each set of corresponding equipment such as aeration system and water-repellent system is required in each reaction tank. And the pools are running alternately, so the equipment utilization is also low. In addition, because the SBR process is intermittent operation, its control system relies on the computer, and the reliability of the equipment instrumentation and the automatic control system is high. Sometimes, the imported equipment is required, which will increase the overall cost of the equipment.

The contact oxidation method is an aerobic biofilm process. The microorganism grows in water in the form of a biofilm and a suspension state, so it has the characteristics of both activated sludge and biofilter. A three-dimensional elastic filler and an aeration pipeline system are arranged in the pool, and a microporous aerator is installed on the aeration pipeline system. The elastic filler is made of a brushed PP material and a stranded rope, and has a round brush shape.

It has a large specific surface area and can attach a large amount of microorganisms (biofilm). The filler film is fast, the film is easy to be removed, and the yarn can play an excellent cutting action on the air bubble during operation, so that the large bubble is cut into small bubbles, which can increase the gas-liquid contact area and promote the transmission of oxygen, thereby improving the treatment effect. . The microporous aerator has high strength, is not easy to be damaged, has uniform gas distribution, low resistance loss, corrosion resistance, and the utilization rate of oxygen is as high as 15% or more. When used together with the elastic filler, the energy saving effect can be achieved. Because the specific surface area of the filler is large, the oxygen utilization rate in the pool is high, the volumetric load is high, and the impact is resistant; the biological contact oxidation tank does not require a sludge return system, there is no sludge expansion problem, and the operation and management are convenient; biological contact oxidation The amount of biosolids in the pool is large, and when the organic volume load is high, the F/M can be maintained at a certain level. In the biological contact oxidation pond, organic carbohydrates are eventually decomposed into CO2 and H2O.