Sources and characteristics of oil and fat wastewater
Oil and fat wastewater mainly comes from the continuous alkali refining, hydration, acidification, neutralization, degumming, deodorization, decolorization, washing, filtration and other processes in the leaching, physical and chemical refining process of the oil and fat production workshop. The oil in the oily wastewater mainly exists in the form of floating oil, dispersed oil, melted oil and oil-solids.
The hazards of oily wastewater are mainly manifested in: oil substances float on the water surface, forming a thin film, which can prevent oxygen in the air from dissolving into the water, reduce the dissolved oxygen in the water, cause the plankton in the water body to die due to lack of oxygen, and also hinder the photosynthesis of aquatic plants, thereby affecting the self-purification of the water body, and even make the water body smelly, destroying the value of water resources.
1. Characteristics of oil and fat industrial wastewater
The wastewater produced by oil and fat industrial production is very complex, containing a large amount of organic matter, oil, protein and other substances, with obvious water pollution characteristics, and has the following characteristics:
1. High COD value: COD concentration is very high, usually treated to more than 2000mg/L
2. High oil content: The oil content often exceeds 1000mg/L, the fatty acid content is high, and it is not easy to be biodegraded.
3. High nitrogen and phosphorus content: Contains a large amount of ammonia nitrogen, organic nitrogen and inorganic phosphorus, which will lead to eutrophication of the receiving water body.
4. Stable color and pH value: The wastewater color is darker, the pH value is neutral, and acid-base adjustment is required.
2. Treatment process
In order to remove pollutants such as oil, organic matter, nitrogen and phosphorus, biological treatment process, physical and chemical treatment process or a combination of the two are often used to treat oil and fat industrial wastewater.
1. Aerobic biological treatment: Aerobic biological treatment is one of the most commonly used treatment processes for oil and fat industrial wastewater. It mainly uses microorganisms to convert organic pollutants in sewage into inorganic substances for treatment. Since oil and fat are difficult to biodegrade, the possibility of actually treating aerobic bioreactors is relatively small. However, adding oil-water separation facilities before the aerobic bioreactor can improve the separation efficiency of oil and fat.
2. Anaerobic biological treatment: Anaerobic biological treatment has great advantages in removing high-concentration oil and fat wastewater and nitrogen-containing organic wastewater. The principle is to allow anaerobic microorganisms to convert organic matter into biogas and organic acids and other substances that are more easily biodegradable in the absence of oxygen.
3. Physicochemical treatment: Physicochemical treatment is usually used to treat high-concentration oil and fat wastewater. It mainly includes separation, precipitation, filtration, etc. This method requires the removal of pollutants based on chemical and physical principles, and has the advantages of high treatment efficiency and stable treatment effect.
III. Monitoring indicators of oily wastewater
Test items: The main test items of oil and fat factory wastewater include chemical oxygen demand (COD), biochemical oxygen demand (BOD), suspended solids, pH value, animal and vegetable oils, total phosphorus, total nitrogen, etc. These indicators can fully reflect the degree of pollution and treatment effect of wastewater.
Testing standard: According to the “Comprehensive Sewage Discharge Standard”, the discharge standard for animal and vegetable oils is 20mg/L. Grease wastewater mainly contains a large amount of animal and vegetable oils, some even reaching 10,000mg/L, which needs to be pre-treated and removed.
The monitoring indicators of oily wastewater mainly include COD, BOD5, SS and grease. Among them, COD and BOD5 are indicators reflecting the content of organic matter in wastewater, SS is an indicator reflecting the suspended matter in wastewater, and grease is an indicator reflecting the oil-containing matter in wastewater. The monitoring of these indicators can help us understand the nature and degree of pollution of wastewater, so as to take corresponding treatment measures to protect the environment.
1. COD
COD refers to chemical oxygen demand, which is one of the important indicators reflecting the content of organic matter in wastewater. The higher the COD value, the higher the content of organic matter in wastewater and the more serious the pollution. COD monitoring can help us understand the chemical oxygen demand of wastewater and provide a basis for wastewater treatment.
This indicator can be measured using Lianhua’s laboratory rapid detection equipment 5B-3C (V8), digesting the sample at 165° for 10 minutes, and then using a photometer to compare the color to get the result.
2. BOD5
BOD5 refers to biochemical oxygen demand, which is also one of the indicators reflecting the content of organic matter in wastewater. Unlike COD, BOD5 needs to be monitored through a bioreactor. The results of BOD5 monitoring can reflect the content of biodegradable organic matter in wastewater and is one of the important indicators in wastewater treatment.
BOD5 can be measured using Lianhua’s mercury-free pressure differential method BOD instrument, cultured in a constant temperature and humidity incubator at 20° for 5 days, with a built-in printer, supporting automatic printing of results. Lianhua’s BOD instrument is intelligently designed. For many samples, no BOD reagent is required, and the results can be obtained with simple operation.
3. SS
SS refers to suspended matter, which is an indicator reflecting the content of suspended matter in wastewater. SS in wastewater mainly comes from solid matter, sludge, etc. in the production process. The results of SS monitoring can help us understand the content of suspended matter in wastewater and provide a basis for wastewater treatment.
Lianhua Technology can provide suspended solids instruments using photometry, which can get results in 5 seconds, ranging from 0-1000mg/L.
4. Grease
Grease refers to oil substances in wastewater, which is one of the important indicators of oily wastewater. Grease in wastewater comes from grease, lubricants, etc. in the production process. The results of grease monitoring can help us understand the content of grease in wastewater and provide a basis for wastewater treatment.
Lianhua can provide infrared oil testers to detect grease in water, including animal and vegetable oils, mineral oils and petroleum. It has an integrated whole machine design and a built-in 10-inch 1920×1200 high-definition touch screen. It does not need to be connected to a computer or tablet, and it can be used immediately after it is turned on.
In short, the monitoring indicators of oily wastewater are very important. It can help us understand the nature and degree of pollution of wastewater, so as to take corresponding treatment measures to protect the environment. In environmental protection control, we can adopt different treatment methods for different monitoring indicators to achieve better treatment effects.
Post time: Nov-07-2024
