With the rapid development of the economy, more and more food factories have sprung up. While improving people's living standards, they have also produced a lot of wastewater, polluting the living environment. What kind of wastewater does a food factory produce? What are its characteristics? How to treat the wastewater from a food factory? What are the ideas and methods for treatment?
1. Characteristics of food factory wastewater
The food industry uses a wide range of raw materials and produces a wide variety of products, so the amount and quality of wastewater discharged vary greatly.
The main pollutants in wastewater are:
(1) Solid matter floating in wastewater, such as vegetable leaves, fruit peels, minced meat, poultry feathers, etc.;
(2) Substances suspended in wastewater include oil, protein, starch, colloids, etc.;
(3) Acids, alkalis, salts, sugars, etc. dissolved in wastewater;
(4) Mud, sand and other inorganic substances carried by the raw materials;
(5) Pathogenic bacteria and viruses, etc.
The main characteristics of food industry wastewater are high content of organic matter and suspended solids, easy corruption, and generally no great toxicity. Its main harm is to cause eutrophication of water bodies, resulting in the death of aquatic animals and fish, causing the organic matter deposited at the bottom of the water to produce odor, deteriorating water quality, and polluting the environment.
2. Food factory wastewater treatment plan
Food wastewater generally has high COD, moderate PH, and large BOD/COD value, so it is suitable to be treated by biochemical method. Generally speaking, the wastewater treatment of food factories mainly adopts pretreatment plus biochemical method.
1. Preprocessing.
Pretreatment uses bar filtration and sedimentation methods to remove larger solid impurities in sewage.
2. Biochemical treatment method.
Biochemical treatment uses the A2O treatment process. Since the organic matter concentration in the wastewater is high and contains a large number of macromolecular pollutants, direct aerobic treatment will result in low treatment efficiency. The anaerobic treatment process is used in the front stage of biochemical treatment. The anaerobic reaction can convert the macromolecular difficult-to-degrade organic matter in the water of the meat processing industry into organic matter that is easily degradable by water molecules. The biodegradability of the effluent is improved, which makes the residence time of the aerobic treatment part shorter than that of the traditional treatment process. At the same time, the suspended matter is hydrolyzed into soluble substances, so that the sludge is treated stably. In the anaerobic pool effluent, the oxygen in the inorganic oxide replaces the molecular oxygen for biological oxidation, further decomposes the organic matter, and removes ammonia nitrogen through denitrification.
3. Activated sludge method.
The technology of using activated sludge method to treat food factory wastewater is very mature and widely used at home and abroad, and has achieved relatively ideal results. The activated sludge method is composed of an aeration tank, a sedimentation tank, a sludge return and a residual sludge removal system. The effluent from the anoxic tank enters the aeration tank, and air is filled into the aeration equipment. The oxygen in the air dissolves into the sewage to make the activated sludge mixed liquid produce aerobic metabolic reactions. The aeration equipment not only transfers oxygen into the mixed liquid, but also makes the mixed liquid sufficiently stirred and suspended. In this way, the organic matter and oxygen in the sewage can fully contact and react with the microorganisms. Under the action of the metabolic function of the microorganisms, the organic pollutants in the sewage are removed and the sewage is purified.
Since the biodegradability of sewage is relatively good, it is more reasonable to use the mature activated sludge method for treatment. This process has the advantages of high volumetric load, strong impact load resistance, low sludge expansion, stable operation, convenient operation and management, and low operating costs. The dissolved and colloidal organic components in the water can be degraded to the greatest extent here.
4. Coagulation and sedimentation method.
A coagulation sedimentation tank can be added after the biochemical treatment tank. The coagulation sedimentation tank adopts an inclined tube form. The biochemical sewage is first mixed with the denitrification agent for reaction, and then flows into the inclined tube sedimentation tank for solid-liquid separation, mainly to settle the biofilm and some fine suspended matter that fall off in the biochemical tank. The inclined tube sedimentation tank uses the shallow layer principle and adopts the form of a heterogeneous flow inclined tube sedimentation tank. It has the advantages of short residence time, high sedimentation efficiency, small footprint, and less maintenance workload.
The inclined tube filler adopts non-deformation inclined tube filler, which has the advantages of anti-deformation and long service life. The filler is installed at an angle of 60. Since the object of precipitation is mainly SS, the medium is in a flowing state during the precipitation process, and the surface of the precipitation inclined tube is relatively smooth, it will not cause clogging of the inclined tube sedimentation tank, ensuring the normal operation of the sedimentation tank.
