Water specification
1. Chemical Oxygen Demand (COD)
Scope: The COD of slaughter wastewater is usually high, with common values ranging from 500-3000 mg/L, depending on the type, quantity, and treatment process of the slaughtered animals.
2. Biochemical Oxygen Demand (BOD5)
Range: BOD5 is generally between 300-1500 mg/L. The organic load in slaughter wastewater is relatively high, and BOD5 is usually high. Generally, BOD/CODC>0.3, and can even reach 0.5, indicating good biochemical properties.
3. Total suspended solids (SS)
Scope: The suspended solids content in slaughter wastewater is generally between 200-1500 mg/L, with an empirical value of 800-1500 mg/L. The concentration of suspended solids in the wastewater is relatively high.
4. Ammonia nitrogen
Scope: The concentration of ammonia nitrogen is generally 50-200 mg/L, and high concentrations of ammonia nitrogen have strong toxicity to water bodies.
5. Oil and Fat
Range: The oil concentration is usually 50-400 mg/L, typically 40-60 mg/L. Special attention should be paid to oils and fats in wastewater treatment processes, as they not only affect water quality but may also clog pipelines and equipment.
6. pH value
Scope: The pH value of slaughter wastewater is generally 6-8. The pH value of wastewater is affected by the slaughter process and animal species, and is usually close to neutral, but may also exhibit acidity or alkalinity.
7. Total nitrogen (TN)
Scope: The concentration of total nitrogen and total phosphorus is generally low, but it may also slightly increase due to nitrogen and phosphorus substances in the animal's body during the slaughter process. The total nitrogen is generally 30-100 mg/L, and there are also data that can reach 150-300 mg/L.
8. Total phosphorus (TP)
The total phosphorus is between 5-20 mg/L, with a conventional range of 6-7 mg/L.
9. Coliform microbiota
Scope: Slaughter wastewater usually contains a large number of pathogenic microorganisms, especially coliforms and other pathogenic bacteria.
Main process flow
1. Pre treatment
Bar screen: Used to remove larger solid impurities from wastewater.
Sand settling tank: removes heavy particulate matter such as sand particles from wastewater.
Oil Separation Tank: Remove impurities such as oil and fur from wastewater. An inclined tube device can be added to the oil separation tank to increase the tank area, reduce the distance of oil droplets rising, and separate more oil particles.
Regulating pool: regulating water quantity and balancing water quality, reducing the impact of water quantity and quality on subsequent treatment units. The bottom of the regulating tank is equipped with perforated pipes, which mix wastewater of different concentrations and time periods evenly in the tank through the stirring effect of air. At the same time, it also has the function of hydrolysis and acidification, decomposing large organic molecules into small organic molecules and improving the biodegradability of wastewater.
Air flotation and flocculation: coagulants are added to the air flotation sedimentation integrated machine, and the mixed solution flows into the air flotation device after flocculation. Fine supersaturated gas combines with suspended solids in the water to form floating slag on the surface of the water. The scraper regularly scrapes off the floating slag, and the floating slag is discharged into the sludge concentration tank for dewatering treatment through the pipeline.
2. Biochemical treatment
Anaerobic treatment:
Using anaerobic systems or hydrolytic acidification techniques to decompose organic matter. During this process, large organic molecules can be decomposed into small organic molecules for further removal in aerobic processes.
Comparison of two anaerobic process options:
The advantage of anaerobic hydrolysis process is that it can effectively treat difficult to degrade organic matter, but its main limitation is that it cannot treat all types of wastewater, especially when the wastewater contains high suspended solids or solid substances, which may affect the treatment effect.
Advantages: Suitable for treating wastewater containing a large amount of complex organic compounds such as proteins, fats, etc. It can effectively promote the hydrolysis of large organic molecules and improve the efficiency of organic degradation in the system.
Disadvantage: Long hydrolysis time is required during the processing. The water quality requirements for wastewater are high, and there should not be too much suspended solids in the wastewater.
The UASB process is a typical anaerobic treatment process suitable for the treatment of high concentration organic wastewater, especially when the wastewater contains high COD and BOD. The UASB reactor controls the upstream flow rate to promote the organic matter in the wastewater to enter the reaction tank through the bottom and be degraded by microorganisms in an anaerobic environment. The UASB reactor has good solid-liquid separation ability and is suitable for treating wastewater with complex components.
Advantages: The effect is significant for wastewater containing high concentrations of organic matter, especially for wastewater with high COD load. Strong adaptability to operating conditions, able to adapt to situations where the composition of wastewater fluctuates greatly. The reactor has a simple structure and is easy to operate and maintain.
Disadvantage: It is sensitive to the content of suspended solids in wastewater and requires effective solid-liquid separation facilities. It is sensitive to changes in wastewater quality and requires good operation and control.
Aerobic treatment:
Adopting activated sludge technology or biological contact oxidation technology with denitrification and phosphorus removal functions to further decompose organic matter. By oxidizing organic matter to release energy and converting it into harmless substances such as carbon dioxide and water.
3. Disinfection treatment
Chlorine dioxide and sodium chlorate disinfection:
Ensure the safety of the effluent water quality. The disinfection contact time should not be less than 30 minutes, and the effective concentration should not be less than 50mg/L.
Ozone disinfection:
Ozone has strong oxidizing properties and can kill viruses and spores, remove pollutants such as color, odor, taste, and phenol and chlorine from wastewater. It can also be considered for advanced treatment.
4. Deep processing (if required):
Adopting a combination of biological and physicochemical treatment processes, such as biological aerated filter (BAF), biological activated carbon, coagulation sedimentation, filtration, etc. Reverse osmosis (RO) and other treatment methods can also be used to separate salt or specific soluble substances in slaughter wastewater through reverse osmosis membranes, achieving efficient purification.