Wastewater Treatment in the Food Industry Abstract: The content of the food industry is extremely complex, including sugar refining, brewing, meat, and dairy processing production processes, all of which discharge wastewater containing organic matter, which is highly oxygen-consuming and contains a large amount of suspended solids. The wastewater from animal food processing also contains animal excrement, blood, fur, and fat, and may contain pathogens, so it has a high oxygen demand and is much more polluting than the wastewater from plant food processing. Therefore, the wastewater from the food industry has a significant impact on the environment and human health, and it needs to be treated and purified before being discharged. Keywords: Food, Food Industry Wastewater, Treatment Methods 1 Overview: The food industry includes meat processing, aquatic product processing, dairy processing, canned food production, brewing, and sugar refining, among other industries. Therefore, the food industry has a wide range of raw materials and a variety of products, and the amount and quality of the wastewater discharged vary greatly. Unlike other industrial wastewater, food industry wastewater generally does not contain harmful substances such as heavy metals and pesticides. However, its BOD and COD are usually high. Since most of the raw materials used in the food industry are organic substances that can be digested by the human body, the biodegradability of food industry wastewater is generally good. The main pollutants in the wastewater are: (1) solid substances floating in the wastewater, such as vegetable leaves, fruit peels, meat scraps, and poultry feathers; (2) substances suspended in the wastewater, such as fats, proteins, starches, and colloidal substances; (3) acids, alkalis, salts, and sugars dissolved in the wastewater; (4) sand and other organic matter brought in by the raw materials; (5) pathogens and toxins. Food wastewater includes wastewater from the production of alcohol, beer, monosodium glutamate, starch, lactose, citric acid, vegetable processing, and various soft drinks. If the wastewater is not treated in time, it can cause great pollution to the environment. The characteristics of food industry wastewater are high content of organic matter and suspended solids, easy to decompose, generally non-toxic, and the amount and quality of the wastewater change with the seasons, with many high-concentration wastewater. Its main harm is to cause eutrophication of water bodies, leading to the death of aquatic animals and fish, and the organic matter deposited at the bottom of the water to produce an odor, worsening the water quality, and polluting the environment. In addition to appropriate pretreatment according to the quality characteristics of the wastewater, food industry wastewater is generally suitable for biological treatment. If the water quality requirements are very high or the content of organic matter in the wastewater is very high, two-stage aeration tanks or two-stage biological filters, or multi-stage biological discs can be used, or two biological technologies can be combined, or an anaerobic-aerobic series biological treatment system can be used.

　　2 General Situation at Home and Abroad The treatment of food wastewater pollution in China started later than in Western countries. Based on the experience of advanced foreign technologies, China has introduced and developed a large number of new food wastewater treatment technologies through science and technology research projects some of which have reached a high level. The operation of these new technologies has played a crucial role in alleviating China's severe water pollution and improving the water. According to the China Environmental Condition Bulletin, in 2008, the pollution of surface water in the country remained serious. Among the 40 national monitoring sections of the seven major river systems, the proportions of sections with water quality of Class I to III, Class IV to V, and worse than Class were 49.9%, 26.5%, and 23.6%, respectively. The overall water quality of the seven major river systems moderately polluted, the rivers in the Zhejiang-Fujian region were lightly polluted, the rivers in the Northwest were excellent, and the rivers in the Southwest in good condition. The lakes (reservoirs) had prominent eutrophication problems; the overall water quality of the nearshore sea areas was lightly polluted Food industry wastewater accounts for a large proportion of this pollution. In China, especially in small and medium-sized towns, there are a large number of food processing enterprises The modernization level and production scale of these enterprises are increasing, but the quality of the wastewater they produce is poor, and the amount of wastewater is continuously increasing causing serious environmental harm. The food industry, including the beverage industry, is a major consumer of water. Most of the water consumed is used for washing and cleaning the food production process, so this wastewater can be recycled. The pollutants produced by the fermentation industry, which mainly uses grain as raw material, are mainly due to unused grain, so most of the pollutants discharged into the water environment are products and by-products with recovery value. Modern wastewater treatment technologies are divided into three categories: treatment methods, chemical treatment methods, and biochemical treatment methods. Physical treatment methods include: sedimentation method, filtration method, centrifugal separation method, and flotation method chemical treatment methods include: coagulation method, neutralization method, oxidation-reduction method, electrolysis method, extraction method, air stripping method, adsorption, electrodialysis method, and reverse osmosis method; biochemical treatment methods include: activated sludge method, biological film method, oxidation pond method, land treatment method. Additionally, there are some new technologies, such as enzymatic degradation method, application of high-efficiency degrading bacteria, application of ultrasound technology magnetic separation method, supercritical water oxidation method, and electro-biological film method.

　3 Wastewater Treatment 3.1 Indicators of wastewater pollution and wastewater characteristics: Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Suspended Solids (TSS), Volatile Suspended Solids (VSS), nutrients, acidity andinity, temperature, and toxic substances. 3.2 Physical treatment methods: Physical treatment methods refer to methods that alter the components of wastewater using physical actions. Methods in the food industry include screening, skimming, equalization, sedimentation, flotation, centrifugal separation, filtration, and microfiltration. The first five are often used for pretreatment or primary treatment, while the last three are mainly used for advanced treatment. 3.2.1 Screening Screening is a used method in pretreatment. Its main function is to separate larger suspended solids from the wastewater. The equipment used includes grates and screens. Grates intercept larger solids and serve to protect pumps and subsequent treatment equipment. 3.2.2 Skimming Some food industry wastewater contains a large amount of oil, which must removed before entering the biological treatment process to prevent clogging of pipes, pumps, and some equipment, and to avoid affecting the biological treatment process. Additionally, the and recovery of oil has significant economic value. The oil in the wastewater can be divided into free floating and emulsified forms. Typically, oil separators are used remove floating oil, with a removal rate of over 90%. If an equalization tank or sedimentation tank is set up in the treatment process, it save investment and space. 3.2.3 Equalization For food industry wastewater with large fluctuations in flow, an equalization tank is set up to regulate quality and quantity of the wastewater. 3.2.4 Sedimentation Sedimentation is used to remove inorganic and organic solids from the original, as well as to separate the solid and liquid phases in the biological treatment process. Sand settlers are used to remove inorganic solids from the original wastewater; primary are used to remove organic solids from the original wastewater; secondary settlers are used to separate the biological phase and liquid phase in the biological treatment process. Sand settlers are placed after grates and screens. To avoid the precipitation of organic solids in the sand settler during removal, an aerated sand settler can be used. a primary settler can reduce the burden on subsequent processes. According to the direction of water flow in the tank, there are horizontal flow sedimentation tanks, vertical sedimentation tanks, and radial flow sedimentation tanks.

　　3.2.5 Air Flotation Air flotation is mainly used to remove emulsified oils, surfactants and other suspended solids from wastewater. There are vacuum, pressurized dissolved air, and plate types. Before the wastewater enters the air flotation tank, chemical coulants or flocculants are added to the water to improve the removal rate. 3.3 Chemical Treatment Methods Chemical treatment methods refer to the of chemical principles and chemical reactions to convert pollutants in wastewater into harmless substances, thereby purifying the wastewater. The pollutants undergo chemical changes during the treatment process. Methods for food wastewater treatment include neutralization, coagulation, electrolysis, oxidation-reduction, ion exchange, and membrane separation. 3.3.1 Coulation Method The coagulation method is a primary chemical treatment method that cannot be used alone but must be combined with physical treatment processes such as sedimentation,, or air flotation, forming coagulation sedimentation or coagulation air flotation. For wastewater with small colloidal particles or colloidal solutions that are difficult precipitate, coagulants are added to form larger particles that are easier to precipitate and thus remove. 3.3.2 Oxidation-uction Oxidation-reduction is an effective method for converting pollutants in wastewater. Organic and inorganic substances in the wastewater are oxidized or reduced through reactions into micro-toxic or non-toxic substances, or into forms that are easier to separate from water, thereby achieving the purpose of treatment. 3.33 Ion Exchange Ion exchange mainly involves using ion exchange agents to remove harmful ions from the water through exchange reactions.

　　3.4 Biological Treatment Methods Biochemical treatment methods are one of the critical processes in organic wastewater systems. In the treatment of food industry wastewater, biological treatment processes are divided into aerobic, anaerobic, stabilization ponds, land treatment, and various combinations these. Biological methods are the primary secondary treatment processes, aimed at degrading COD and BOD. Aerobic biological treatment processes are divided into activated sludge and membrane processes based on the growth form of the utilized microorganisms. The former includes traditional activated sludge, stage aeration, biological adsorption, complete mixing extended aeration, oxidation ditches, and intermittent activated sludge. The latter includes biological filters, tower biological filters, biological rotors, activated biological filters, contact oxidation, and aerobic fluidized beds. Anaerobic biological treatment methods are suitable for food industry wastewater, mainly because the wastewater contains easily biodegradable highcentration organic matter and is non-toxic. Additionally, anaerobic treatment consumes less power, the produced biogas can be used as energy, and the sludge is minimal. The entire anaerobic treatment system is sealed, which helps improve environmental hygiene. 4 Conclusions and Prospects Through the use and of various effective methods, food industry wastewater has been significantly improved, and other substances can be obtained from it, producing other raw materials instead of wasting the waste. can be recycled, reducing unnecessary losses and waste. The harm to water pollution, human health, and other aspects has been greatly reduced. However, the equipment and consumption of various treatment methods are a significant burden. Most rural or small and medium-sized food enterprises cannot afford it. Moreover, some enterprises, in pursuit of more, are unwilling to invest too much in wastewater treatment. On the other hand, the country's policies and relevant laws and regulations are not perfect and are not strictly. The country's investment in this area is also limited. Furthermore, some people in food enterprises have low quality and insufficient awareness, not seeing the severity of wastewater and only caring about their own interests. If the country can increase its investment in this area and establish a complete system and legal system, making these detection methods widely, the situation of food industry wastewater treatment will be greatly improved, with minimal impact on water pollution and significantly reduced harm to human health. Food enterprises will also gain benefits from the treatment process, enabling resource recycling and reducing unnecessary burdens and waste. I believe that if the above detection methods can be popularized, China will benefit greatly, not only in monetary terms but also in the well-being of the entire population.