Canteen sewage treatment scheme and process flow

First, the generation and harm of canteen sewage

Canteen sewage is mainly produced in raw material cleaning, rice washing, tableware cleaning, floor cleaning, etc. Canteen sewage contains a lot of food fiber, protein and oil, if not treated, it will cause water eutrophication and pollution. After pretreatment such as oil separation and slag removal, kitchen sewage still contains a large number of organic pollutants such as emulsified colloidal oils, proteins and food fibers that are difficult to be mechanically treated, which need to be deeply treated before it can reach the discharge standard.

Second, canteen sewage process analysis

Shenzhen Water sky Blue Environmental Protection Technology Co., Ltd. refers to the treatment of canteen sewage is given the following treatment process.

1. Pretreatment process

A. Grease trap

The grease trap uses the different specific gravity of suspended matter and water in the wastewater to achieve the purpose of separation. The structure of the grease trap mostly adopts the horizontal flow. The oily waste water enters the rectangular grease trap through the distribution tank and flows slowly along the horizontal direction. In the flow, the oil products float to the surface and are pushed to the oil collector by the oil collector or the oil scraper installed on the surface of the pool. The heavy oil and other impurities deposited in the grease trap accumulate in the sludge hopper at the bottom of the pool and enter the sludge pipe through the mud discharge pipe. After oil separation treatment, the wastewater is overflowed into the drain discharge tank for subsequent treatment to remove emulsified oil and other contaminants.

The grease trap is built with reinforced concrete, and it is also used for masonry on a rectangular plane. It is divided into 2 to 4 cells along the direction of water flow, and the width of each cell is generally not more than 6 meters, so that the water is evenly distributed. The effective water depth is not more than 2 meters, and the length of the grease trap is generally more than 2 times the width of each cell.

In the actual operation of domestic sewage treatment, pretreatment facilities can be appropriately increased or decreased according to the specific water quality and quantity of the site, and the general sewage treatment system with too small water volume can not set up a sand settling tank, because the regulating tank itself can play the role of sand settling.

B. Grille

Grille, grille is installed at the inlet of waste water channels and collection Wells, used to intercept large suspended objects or floating objects, to prevent blocking the pump unit and pipeline valves. At the same time, it can also reduce the processing load of subsequent structures. The grille is divided into two kinds: artificial grille and mechanical grille. In general, large particles in sewage are less, or artificial grilles are more commonly used with less water, and mechanical grilles can be used for sewage treatment facilities with larger water volume according to the situation.

C. Regulating pool

The regulation of water quantity and water quality, the regulation of sewage pH value and water temperature, has the effect of pre-aeration, and can also be used as accident drainage. There are two regulating ponds: homogeneous regulating pond and uniform regulating pond. For domestic sewage, the regulating pond plays both a uniform regulating role and a uniform regulating role. The general design residence time is 4-24 hours, often made of civil steel-concrete structure, but also made of brick concrete, carbon steel or fiberglass structure.

2. Biochemical treatment

The biological contact oxidation method is a biofilm process between the activated sludge method and the biological filter, which is characterized by the setting of filler in the pool, aeration of the bottom of the pool to oxygenate the sewage, and the sewage in the pool is in a flowing state to ensure full contact between the sewage and the filler in the sewage, and avoid the defects of uneven contact between the sewage and the filler in the biological contact oxidation tank.

In this method, the oxygen required by microorganisms is supplied by blast aeration. When the biofilm grows to a certain thickness, microorganisms in the packing wall will undergo anaerobic metabolism due to anoxia, and the resulting gas and erosion caused by aeration will cause the biofilm to fall off and promote the growth of new biofilm. At this time, the shed biofilm will flow out of the pool with the water. The biological contact oxidation method is a kind of biofilm method with the characteristics of activated sludge method, and has the advantages of both biofilm method and activated sludge method.

3. Process flow and description

Most of the oil float and leftover rice residue are removed from the waste water through the oil separator and enter the regulating tank. After homogenizing and equalizing the amount in the regulating tank, the waste water is raised to the A-class biological tank by the pump. In the A-class biological tank section, the heterotrophic bacteria hydrolyze the soluble organic matter in the sewage into organic acid, decompose the macromolecular organic matter into small molecular organic matter, and convert the insoluble organic matter into soluble organic matter. Ammoniation of contaminants such as proteins and fats.

There are aerobic microorganisms and digestive bacteria in the O-level biological pool, in which the aerobic microorganisms decompose organic matter into CO2 and H2O. Under the condition of sufficient oxygen supply, the nitrification of nitrifying bacteria oxidizes NH3-N to NO3-, and returns to the A-level biological tank through reflux control. Under the condition of hypoxia, the denitrification effect of the aerobic bacteria reduces NO3- to molecular nitrogen, and the effluent of the supernatant of the oxidation tank enters the sedimentation tank for sedimentation. The effluent of the supernatant of the sedimentation tank enters the clear pool for A short time, and the effluent is discharged according to the standard.