Slaughtering Sewage Treatment Project in Mexico

Project content:

The construction content of this project mainly includes: slaughtering ring, slaughtering and processing workshop, cold storage, etc., and supporting construction of sewage treatment station and other supporting projects. The capacity of sewage is 1200m3/day, inlet COD 2100mg/L, the outlet COD<100mg/L

Wastewater characteristics:

The wastewater of the factory mainly comes from the wastewater of the slaughtering production line, the wastewater of the (cattle, sheep) meat processing workshop, the softened water of the boiler, the drainage of the refrigeration system and the domestic sewage of the factory during the product processing.

Wastewater contains a large amount of blood, oil, hair, meat scraps, bone scraps, visceral debris, undigested food, feces and other contaminants, and the content of solid suspended solids is high.

In summary, the analysis shows that

(1) The wastewater contains COD, BOD, ammonia nitrogen, SS and animal and vegetable oils as the main pollutants;

(2) It belongs to typical organic and biochemical wastewater.

Design ideas:

The slaughtering wastewater contains a certain amount of suspended solids such as broken skin, ground meat, cattle hair, feces, residual feed, etc., with high chromaticity. In order to improve the removal efficiency of pollutants, grids or screens are first used to remove larger particle sizes in the wastewater. The suspended solids are treated by precipitation or air flotation after the post-dosing coagulation reaction. Coagulation is the addition of chemicals to water, through rapid mixing, the chemicals are evenly dispersed in the water, and then react to form large flocs. The larger flocs produced by coagulation are separated from the water by means of solid-liquid separation by subsequent precipitation or air flotation. The characteristics of sedimentation separation are small investment, large floor space, long processing time, high sludge moisture content, simple operation and management, and low failure rate; the main characteristics of air flotation separation are fast separation speed, low sludge moisture content, The land area is small, the operation and management are complicated, and the operation cost is high.

Since the slaughtering wastewater also contains a certain amount of blood stains and grease, we choose to remove grease and suspended solids at the same time as pretreatment, and then use air flotation for re-treatment. Practice has shown that when adding flocculants to remove pollutants in the pretreatment process, it is not that the more types of flocculants are added and the larger the dosage of chemicals is, the better the removal effect is. Coagulation agent, when the dosage is kept at a certain amount (trace amount), the pollutant removal effect is good. This is the selective physical and chemical technology, which is conducive to saving the cost of chemicals and reducing the amount of physical and chemical sludge.

A: The wastewater passes through coarse and fine gratings to remove large particles of debris, cattle wool, and large pieces of oil, and then flows to the sedimentation adjustment tank for oil floating isolation and suspended solids sedimentation removal.

B: The effluent from the sedimentation conditioning tank is lifted to the air intake flotation machine to further remove grease and suspended solids.

C: The flotation water enters the lifting well, and is lifted to the UASB anaerobic tower by a water pump, and the pH value of the water quality is adjusted to 8.0-9.0 by adding alkali to create hydrolysis conditions. The anaerobic tower effluent flows into the anoxic/aerobic pool. In the oxygen/aerobic tank, the COD, BOD, and ammonia nitrogen are reacted more deeply, and most of the pollutants are digested. The effluent from the aerobic tank flows into the secondary sedimentation tank, and after the effluent from the secondary sedimentation tank, it flows into the disinfection treatment and discharges up to the standard.

D: The excess sludge in the sedimentation adjustment tank, air flotation machine, and secondary sedimentation tank is discharged into the sludge thickening tank, and is driven into the belt sludge dewatering machine through the sludge pump for sludge pressing. The filtrate is returned to the grid canal for further treatment. The mud cake is transported to the landfill for safe disposal.

Technological process:

According to the above analysis and combined with our company's years of experience in the treatment of the same type of wastewater, in line with the purpose of up-to-standard discharge, from the perspective of saving construction costs and operating costs, the treatment route for the new part of the project is determined as: "mechanical coarse grid The comprehensive treatment technology of grid + mechanical fine grid + sedimentation adjustment tank + air flotation + UASB anaerobic tower + anoxic + aerobic + secondary sedimentation tank + third sedimentation tank + disinfection tank" ensures that the wastewater can meet the design effluent requirements.