Basic equipment configuration:
Name: Oily wastewater treatment equipment
Amount of sewage treated: 1-50 (m3 / h)
Ozone dosage: 0 ~ 500 (g / h)
Flowmeter specifications: 5-100 (m3 / h)
Outlet pipe diameter: DN20-DN80 (mm)
Inlet pipe diameter: DN25 ~ DN100 (mm)
Dimensions: L500 * B190 * 180 (cm)
Aerator power: 2 (kw)
The production of oily sewage is large and involves a wide range, such as oil extraction, petroleum refining, petrochemicals, oil storage and transportation, tanker accidents, ship shipping, vehicle cleaning, machinery manufacturing, and food processing. As a common pollution, oil pollution is extremely harmful to environmental protection and ecological balance. Today there are many oil-water separation technologies, and the commonly used methods include gravity separation, air flotation, coarse granulation, filtration, adsorption, and ultrasonic methods.
Oily substances usually exist in three states in wastewater.
Floating oil: The diameter of the oil droplets is larger than 100 μm, which is easy to be separated from the waste water. Oil products have larger particles dispersed in wastewater, and the particle size is greater than 100 microns, which is easy to separate from wastewater. In petroleum sewage, this oil accounts for 60 to 80% of the total oil content in water.
Dispersion oil: The diameter of the oil droplets is between 10 and 100 μm, and it floats in water.
Emulsified oil: The particle size of the oil droplets is less than 10μm, and the particle size of the oil dispersed in the wastewater is small, and it is in an emulsified state, and it is not easy to separate from the wastewater.
Oily substances contained in oily wastewater include natural petroleum, petroleum products, tars and their fractions, as well as edible animal and vegetable oils and fats. In terms of water pollution, mainly oil and tar. The concentrations of oily substances in wastewater discharged from different industrial sectors vary widely. For example, the waste water produced during the refining process has an oil content of about 150-1000 mg / L, the tar content in the coking plant wastewater is about 500-800 mg / L, and the tar content in the wastewater discharged from the gas generation station can reach 2000-3000 mg. /Rise.
Due to the large differences in oil concentration in wastewater discharged from different industrial sectors, such as wastewater generated during the refining process, the oil content is about 150-1000mg / L, the tar content in coking wastewater is about 500-800mg / L, and the gas generation station discharges wastewater into the wastewater. The tar content can reach 2000-3000mg / L. Therefore, the treatment of oily wastewater should first use an oil trap to recover slick oil or heavy oil. The treatment efficiency is 60% to 80%, and the oil content in the effluent is about 100 to 200mg / L. It is difficult to emulsify and disperse oil in wastewater. Treatment, it should prevent or reduce the phenomenon of emulsification. One method is to reduce the emulsification of oil in the wastewater during the production process; the other is to reduce the number of times that the pump is used to raise the wastewater during the treatment process to avoid increasing the degree of emulsification. Treatment methods usually use air flotation and demulsification.
If oily wastewater is not recycled, it will cause waste; discharge into rivers, lakes or bays will pollute water bodies and affect the survival of aquatic organisms; used in agricultural irrigation, it will block soil voids and hinder crop growth.
The treatment of oily wastewater should first consider the recovery of oily substances and make full use of the treated water resources. Therefore, the treatment of oily wastewater can first use oil traps to recover oil slick or heavy oil. The oil trap is suitable for separating oil with large particles in wastewater. The treatment efficiency is 60 to 80%, and the oil content in the effluent is about 100 to 200 mg / liter. Fine oil droplets and emulsified oil in wastewater are difficult to remove.
The main treatment methods used for oily wastewater treatment equipment are as follows:
Gravity separation method < br Gravity separation method is a typical primary treatment method. It uses the density difference between oil and water and the incompatibility between oil and water to separate oil droplets, suspended solids and water under static or flowing conditions. The oil droplets dispersed in water slowly rise and layer under the buoyancy effect. The speed of oil droplets floating depends on the size of the oil particles, the difference between the density of oil and water, the flow state and the viscosity of the fluid. The relationship between them can be described by the laws of Stokes and Newton.
Filtration method < br The filtration method is to pass wastewater through a device with perforations or through a filter layer composed of a certain particulate medium, and use its retention, screening, and inertial collision to make suspended solids and oil in the wastewater harmful. Material is removed. There are three common filtration methods: layered filtration, membrane filtration, and fiber media filtration.
Membrane filtration method, also called membrane separation method, uses microporous membranes to trap oil beads and surfactants, and is mainly used to remove emulsified oil and some dissolved oil. Filter membranes include ultrafiltration membranes, reverse osmosis membranes, and hybrid membranes. Membrane materials include organic and inorganic membranes. Common organic membranes include cellulose acetate membranes, polysulfone membranes, and polypropylene membranes. Common inorganic membranes include ceramic membranes, alumina, cobalt oxide, and titanium oxide. Emulsified oil is in a stable state, and it is difficult to separate it by physical or chemical methods. With the rapid development of membrane science, the treatment of emulsified oil wastewater by membrane process has been gradually accepted and applied in industry.
Bio-oxidation method < br Bio-oxidation method is a method of purifying wastewater by using the biochemical action of microorganisms. Oil is a kind of hydrocarbon organic matter, which can be decomposed into carbon dioxide and water by using microbial metabolism and other life activities. Organic matter in oily wastewater mostly exists in dissolved and emulsified state, and BOD5 is higher, which is beneficial to biological oxidation. For wastewater containing oil with a mass concentration below 30-50 mg / L, but also containing other biodegradable harmful substances, biochemical treatment is commonly used, mainly for removing dissolved oil in wastewater. Common biochemical treatment methods for oily wastewater include activated sludge method, biological filtration method, and biological turntable method. The activated sludge method has good treatment effect, and is mainly used to treat wastewater with high requirements and stable water quality. Compared with the activated sludge method, the biofilm method is attached to the surface of the filler carrier, so that microorganisms that reproduce slowly can also exist, thereby forming a stable ecosystem. However, because the amount of microorganisms attached to the surface of the carrier is difficult to control, it has poor flexibility in operation and limited volume load.
Chemical method <br /> The chemical method, also known as the pharmaceutical method, is a method of adding chemicals to convert pollutant components in wastewater into harmless substances by chemical action to purify the wastewater. Commonly used chemical methods include neutralization, precipitation, coagulation, and redox. For oily wastewater, coagulation is mainly used. The coagulation method is to add a certain proportion of flocculant to the oily wastewater. After hydrolysis in water, a positively charged micelle is formed and a negatively charged emulsified oil is electrically neutralized, the oil particles are aggregated, and the particle size becomes large. The object adsorbs fine oil droplets, and then achieves oil-water separation by sedimentation or air flotation. Common flocculants include inorganic flocculants such as polyaluminum chloride (PAC), ferric chloride, aluminum sulfate, and ferrous sulfate, and organic polymer flocculants such as acrylamide and polyacrylamide (PAM). Dosage and pH range are different. This method is suitable for emulsified oil droplets and other fine suspensions that cannot be separated by gravity sedimentation.
Adsorption method <br /> Adsorption method is the use of lipophilic materials to adsorb dissolved oil and other dissolved organic matter in wastewater. The most commonly used oil-absorbing material is activated carbon, which can absorb dispersed oil, emulsified oil and dissolved oil in wastewater. Due to the limited adsorption capacity of activated carbon (generally 30 to 80 mg / g for oil), high cost and difficult regeneration, it is generally only used as the last stage of multi-stage treatment of oily wastewater. mg / L. In 1976, Hunan Changling Refinery adopted activated carbon adsorption for advanced treatment in wastewater treatment. The development of new adsorbents at home and abroad has also achieved some beneficial results. The study found that flake graphite can adsorb heavy oil released by oil spills on offshore tankers and easily separate from water.
Adsorption resin is a new type of organic adsorption material developed in recent years. It has good adsorption performance and easy regeneration. It has a tendency to gradually replace activated carbon. More and more people in the industry are studying the synthesis and application of efficient oil absorption resin. Studies have shown that the use of polypropylene oil-absorbing materials for the separation and recovery of oily substances from oily industrial wastewater can be based on factors such as the initial condition of the wastewater, final requirements, water flow, and other suitable purification methods. In addition, coal ash, modified bentonite, sulfonated coal, crushed coke, organic fibers, linoleum, ceramsite, quartz sand, wood chips, straw, etc. can also be used as oil absorbing materials. After the oil-absorbing material is saturated with oil, it can be re-used or used directly as fuel according to specific conditions.
Combined ultrasound / electrochemistry technology < br Using the cavitation effect of ultrasound, the electrode can be prevented from forming a covering layer in the electrochemical reaction, which can prevent the electrode activity from decreasing. And accelerate the decomposition of pollutants in sewage; ultrasound can also fully disperse organic matter in aqueous solution, thereby greatly improving the processing capacity of the reactor. Mizera et al. Found that in the electrolytic oxidation treatment of phenol-containing wastewater, when there is no ultrasound, the decomposition rate is only 50%. If 25kHz, 104W / m2 ultrasonic treatment is used, the decomposition rate of phenol will increase to 80%. The treatment of printing and dyeing wastewater by Liu Jing et al. Using combined ultrasound / electrochemical technology showed that the decolorization rate of wastewater was much higher than that of ultrasonic wave alone under the synergistic effect of ultrasound and electric field.
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