Slaughter wastewater treatment process
Preamble to Slaughter Wastewater
1. Source of water quality
Slaughter wastewater arises from cleansing and rinsing of enc...
Slaughter wastewater treatment process
Preamble to Slaughter Wastewater
1. Source of water quality
Slaughter wastewater arises from cleansing and rinsing of enclosures, washing of slaughter and other factory floors, scalding, dissection, processing of non-staple food, animal remnants, blood, and other constituents. The fecal matter retained in animal bodies and the blood generated during the slaughter process bear a significant amount of ammonia nitrogen. Left untreated, they can permeate the soil or spill into rivers, causing harm to the natural water essential for human survival, fostering the proliferation of blue-green algae and inducing widespread mortality of fish and shrimp in the water.
2 Water quality attributes
From its water quality origin, it is apparent that the wastewater primarily comprises blood, oil, minced meat, bone debris, animal hair, and excreta. The wastewater is a reddish brown color and emits a pronounced fishy odor. The organic suspended solids present elevated levels and are prone to decomposition. Once discharged into water bodies, they consume dissolved oxygen, damage ecosystems, and contaminate the environment. Furthermore, its most salient difference from other high concentration organic wastewater is that its NH3-N concentration is relatively high (approximately 120mg/L), hence the impact of NH3-N on wastewater treatment should be thoroughly considered in process design.
3 Hazards of Slaughter Water
The organic suspended solids possess elevated levels and are prone to decomposition. Once discharged into water bodies, they consume dissolved oxygen, damage ecosystems, and pollute the environment.
During the process of slaughtering and meat processing, a substantial volume of water is utilized, and concurrently, wastewater laden with pollutants such as blood, oil, wool, meat scraps, livestock and poultry organs, undigested food and excreta must be discharged. Moreover, such wastewater also harbors a vast number of microorganisms detrimental to human health. If meat processing wastewater is discharged directly without treatment, it will engender severe pollution to the water environment and pose a menace to human and animal health.
The pollutants contained in meat processing wastewater predominantly belong to readily biodegradable organic compounds. After they are discharged into water bodies, they swiftly consume dissolved oxygen in the water, causing fish and aquatic organisms to perish due to hypoxia; Due to hypoxia, water bodies can also transition into anaerobic states, which can deteriorate water quality, generate odors, and affect hygiene. Concurrently, pathogenic microorganisms in wastewater will proliferate in vast numbers, posing a threat to human health. It is imperative to treat the wastewater from slaughtering and meat processing to eradicate its pollution and safeguard the ecological environment and human health.
Slaughter wastewater treatment process
1. Grid regulating pool
(1) Mechanical grille: intercepts and eliminates hair and visceral residues from wastewater.
(2) Regulating pool: storing wastewater, uniformly regulating water quality and quantity, can effectively mitigate the impact of wastewater flow fluctuations and reduce load.
2. Air flotation coagulation tank
Certain low-density oily substances in the wastewater are floated to the liquid surface via air flotation, and subsequently, the floating slag is eliminated by a scraper.
3 Anaerobic tanks
Within the anaerobic tank, facultative microorganisms are employed to reduce nitrate in sewage to molecular nitrogen, which escapes into the atmosphere and plays a role in denitrification. The hydrolysis acidification tank also serves an acidic fermentation function, degrading carbohydrates into fatty acids and converting recalcitrant large molecules into easily biodegradable small molecules.
4 Hypoxia pool
Following anaerobic reaction in the tank, it transits to the anoxic tank for denitrification reaction to further eliminate ammonia nitrogen
5 Aerobic tanks
Within the aerobic tank, residual organic carbides are digested and eliminated through biological contact oxidation. The principal process is mechanical air blowing oxygenation biological contact oxidation treatment technology. The suspended substances in the sewage are intercepted by hanging fillers in the tank, and the colloidal substances in the sewage are adsorbed on its surface. The organic matter within it enables microorganisms to proliferate rapidly under conditions of ample oxygen, while these microorganisms further adsorb suspended solids colloids and dissolved substances in the sewage, progressively forming a biofilm. The sewage is purified through the adsorption, oxidation, and flocculation of the biofilm.
6 Sedimentation tank
Upon undergoing biochemical aerobic reaction, the wastewater proceeds to the sedimentation tank for solid-liquid separation. The sludge descends to the base of the tank and is pumped into the sludge concentration tank for pressure filtration by a sludge pump. The supernatant is discharged in accordance with the standard.
Common treatment reagents for slaughter wastewater
Coagulants: occasionally also referred to as coagulants, can be employed as a method to augment solid-liquid separation, in primary sedimentation tanks, air flotation machines, tertiary treatment, or deep treatment. There are primarily polyacrylamide and sodium polyacrylate.
Coagulant aid: The auxiliary flocculant fulfills a role and amplifies the coagulation effect. There are primarily aluminum sulfate, alum, green alum, polyaluminum, ferric chloride, polyiron, and lime.
Defoamer: primarily utilized to eradicate a significant amount of foam in the process of aeration or mixing.
PH adjuster: utilized to regulate the pH value of acidic and alkaline wastewater. There are primarily lime, caustic soda, sodium carbonate, sulfuric acid, and hydrochloric acid.
Redox agent: employed for the treatment of industrial wastewater containing oxidizing or reducing substances.
Disinfectant: Utilized for disinfection treatment post wastewater treatment prior to discharge or reuse. There are primarily thiazolone, sodium hypochlorite, and organic sulfur fungicides.
Phosphorus removal agent: Phosphorus removal agents can be employed to eliminate turbidity from wastewater, and the phosphorus content of water treated with phosphorus removal agents will be reduced below the threshold value (removing inorganic phosphorus).
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