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Introduction of wastewater treatment process in food factory


With the rapid development of economy, more and more food factories have sprung up, which not only improve people’s living standards, but also produce a lot of waste water and pollute the living environment. What kind of wastewater does the food factory have? What are the characteristics? How to treat the waste water of food factory? What are the ideas and methods?

The main pollutants in wastewater are:

  • Solid substances floating in wastewater, such as vegetable leaves, peel, broken meat, bird feathers, etc;
  • The suspended substances in the wastewater include oil, protein, starch, colloidal substances, etc;
  • Acids, alkalis, salts and sugars dissolved in wastewater;
  • Mud, sand and other inorganic substances carried by raw materials;
  • Pathogenic bacteria and toxin, etc.

The main characteristics of food industry wastewater are high content of organic matter and suspended solids, easy to corrupt and generally non-toxic. The main harm is eutrophication of water body, resulting in the death of aquatic animals and fish, causing the odor of organic matter deposited at the bottom of water, deteriorating water quality and polluting the environment.

Sewage treatment scheme of food factory

Generally, the food sewage has higher COD, moderate pH and higher bod/cod value, so biochemical method is suitable for treatment. Generally speaking, the wastewater treatment of food plants mainly adopts pretreatment and biochemical method.

  1. Pretreatment.

The grid filtration and sedimentation methods are used in the pretreatment, which can remove the large block solid pollutants in the sewage. Wedge wire screen filter element is the core element of the coarse filter.

  1. Biochemical treatment.

A2O process was used for biochemical treatment. Due to the high concentration of organic matter in wastewater, and containing a large number of macromolecular pollutants, direct aerobic treatment will make the treatment efficiency low. Anaerobic treatment process is used in the first stage of biochemical treatment. By using anaerobic reaction, macromolecular refractory organics in meat processing industrial water can be transformed into water molecules easily degradable organics, and the biochemical performance of effluent can be improved, which makes the residence time of aerobic treatment part less than that of traditional treatment process. At the same time, the suspended solids are hydrolyzed into soluble substances, so that the sludge can be treated stably. The effluent from the anaerobic tank flows into the anoxic tank by itself. The inorganic oxide oxygen replaces the molecular oxygen for biological oxidation, which further decomposes the organic matter and removes ammonia nitrogen by denitrification.

  1. Activated sludge process.

The technology of using activated sludge process to treat food factory wastewater is very mature, which is widely used at home and abroad, and has achieved ideal results. Activated sludge process is composed of aeration tank, sedimentation tank, sludge return and excess sludge removal system. The effluent from the anoxic tank enters the aeration tank and is filled with air through the aeration equipment. The oxygen in the air dissolves into the sewage, which makes the activated sludge mixture produce aerobic metabolism reaction. Aeration equipment not only transfers oxygen into the mixture, but also makes the mixture get enough stirring to be suspended. In this way, the organic matter and oxygen in the sewage can fully contact and react with microorganisms. Under the function of microbial metabolism, the organic pollutants in the sewage can be removed and the sewage can be purified.

  1. Coagulation sedimentation method.

Coagulation sedimentation tank can be added after biochemical treatment tank. The coagulation sedimentation tank is in the form of inclined pipe. The biochemical sewage first reacts with denitrification agents, and then flows into the inclined pipe sedimentation tank for solid-liquid separation. It mainly settles the falling biofilm and some fine suspended substances in the biochemical tank. The inclined pipe sedimentation tank uses the shallow layer principle and adopts the form of counter flow inclined pipe sedimentation tank, which has the advantages of short residence time, high sedimentation efficiency, less floor area and maintenance workload.