CN114195336A - Method and system for treating oily sewage - Google Patents
Method and system for treating oily sewage Download PDFInfo
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- CN114195336A CN114195336A CN202210023685.6A CN202210023685A CN114195336A CN 114195336 A CN114195336 A CN 114195336A CN 202210023685 A CN202210023685 A CN 202210023685A CN 114195336 A CN114195336 A CN 114195336A
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/24—Treatment of water, waste water, or sewage by flotation
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/40—Devices for separating or removing fatty or oily substances or similar floating material
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
- C02F1/5245—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents using basic salts, e.g. of aluminium and iron
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/54—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
- C02F1/56—Macromolecular compounds
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
- C02F1/78—Treatment of water, waste water, or sewage by oxidation with ozone
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/30—Aerobic and anaerobic processes
Abstract
The invention relates to a method and a system for treating oily sewage, wherein the method comprises the following steps: s1 collecting the oily sewage in a storage tank, homogenizing and adjusting, and keeping the pH value at 7-9; s2, discharging oily sewage in a storage tank into a pretreatment device for pretreatment after the oily sewage reaches a preset liquid level, wherein the pretreatment comprises oil removal, flocculation, primary coagulation air flotation and ozone oxidation; s3 discharging the pretreated oily sewage into an intermediate water tank; s4 continuously and uniformly injecting the domestic sewage into the middle water tank, and distributing water with the oily sewage in the middle water tank to form mixed sewage; and S5, allowing the mixed sewage to enter an SBR biological reaction tank, performing biodegradation on organic substances of the mixed sewage, performing sludge-water separation and secondary coagulation air flotation treatment on the biodegraded mixed sewage, and finishing the treatment of the oily sewage when the pH value of the mixed sewage reaches 6-9. The invention has high automation degree, high efficiency and low cost for treating the oily sewage and can stably resist impact.
Description
Technical Field
The invention belongs to the technical field of sewage treatment, and particularly relates to a method and a system for treating oily sewage.
Background
The discharge of oily sewage and domestic sewage from ships is in accordance with the discharge standard of ship pollutants. In recent years, with the continuous development of petrochemical industry, the oil refining technology is more advanced, the types of fuel oil are more and more abundant, the composition and the characteristics of ship oily water become more and more complex, and the existing sewage treatment station system cannot meet the treatment requirement of oily sewage.
The current oily sewage treatment generally comprises the processes of oil removal, pre-oxidation, coagulation air flotation, biodegradation and the like. For example, CN206447733U discloses an oily sewage treatment system, which comprises a grit chamber, an oil separation chamber, a coagulation sedimentation tank, an air flotation tank, an anaerobic hydrolysis tank, an SBR reaction tank and a multi-stage constructed wetland unit, wherein the units are connected in sequence and used for conveying sewage in a self-flowing manner, and the multi-stage constructed wetland unit comprises a first-stage vertical flow type constructed wetland, a second-stage subsurface flow type constructed wetland and a third-stage vertical flow type constructed wetland.
CN112079524A provides a system and a process for treating oily sewage, which utilizes a high-pressure pump to pump the oily sewage into a regulating tank; adding a flocculating agent at the front end of the air floatation tank; pressing the supernatant in the air floatation tank into an iron-carbon micro-electrolysis tower for degradation treatment; pressing the wastewater subjected to degradation treatment into a Fenton oxidation tank for oxidative decomposition; pressing the waste water after oxidative decomposition into a hydrolysis acidification pool for further decomposition into small molecular substances; pressing the hydrolyzed and acidified wastewater into an A/O pool to degrade small molecular substances in the water; pressing the wastewater into a coagulating sedimentation tank, adding a flocculating agent into the front end of the coagulating sedimentation tank, and pressing the supernatant of the coagulating sedimentation tank into an activated carbon filter; and starting an activated carbon filter for decoloring and deodorizing to finish sewage treatment.
However, the above treatment processes all have the disadvantages of poor impact resistance, unsmooth sludge discharge, high oxygen consumption/medicament consumption and the like of the pretreatment process before biochemistry, and limit the treatment efficiency and treatment quality of the oily sewage.
Therefore, how to design a processing process flow and a processing system for oily sewage with high automation degree, high processing efficiency, low cost and stable shock resistance is an urgent technical problem to be solved in the field.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method and a system for treating oily sewage, which can realize high treatment efficiency and high automation rate, reduce the cost and are suitable for multi-scene oily sewage treatment.
In a first aspect, the present invention provides a method for treating oily sewage, comprising the steps of:
s1: collecting oily sewage in a storage tank, homogenizing and adjusting, and keeping the pH value at 7-9;
s2: after the oily sewage in the storage tank reaches a preset liquid level, discharging the oily sewage into a pretreatment device for pretreatment, wherein the pretreatment comprises oil removal, flocculation, primary coagulation air flotation and ozone oxidation;
s3: discharging the pretreated oily sewage into an intermediate water tank;
s4: continuously and uniformly injecting domestic sewage into the intermediate water tank, and distributing water with oily sewage in the intermediate water tank to form mixed sewage;
s5: and (3) allowing the mixed sewage to enter an SBR biological reaction tank, performing biodegradation on organic substances of the mixed sewage, performing sludge-water separation and secondary coagulation air flotation treatment on the biodegraded mixed sewage, and finishing the treatment of the oily sewage when the pH value of the mixed sewage reaches 6-9.
Further, the S2 specifically includes:
s21: discharging the oily sewage into an inclined plate separation tank for first oil removal to obtain first pretreated sewage;
s22: the first pretreated sewage enters a coagulation reaction tank added with PAC and/or PAM, and is stirred and subjected to flocculation reaction to obtain second pretreated sewage;
s23: the second pre-treated sewage enters an air floatation reaction tank to be subjected to primary coagulation air floatation treatment, and then is filtered to obtain third pre-treated sewage, and the third pre-treated sewage enters a filtering water storage tank;
s24: and the third pretreated sewage of the filtering water storage tank enters an ozone reaction tower to remove the characteristic pollutants, and then enters a buffer tank to obtain pretreated oily sewage.
Further, the S21 specifically includes:
s211: carrying out oil-water separation on the oily sewage in an inclined plate separation tank;
s212: the separated light oil flows to an emergency sump oil tank through an oil skimming pipe and is lifted and recovered by a pump;
s213: collecting oily sludge into a sludge cone hopper at the bottom of the inclined plate separation tank, and periodically discharging the oily sludge into an oily sludge tank;
s214: and discharging light oil and oily sludge to obtain first pretreated sewage.
Further, the concentration of the added PAC is 400-500mg/L, the concentration of the added PAM is 5-10mg/L, and the temperature of the second pretreatment sewage is less than or equal to 60 ℃.
Further, the S24 specifically includes:
s241: starting an ozone supply system, and conveying the prepared ozone to the bottom of an ozone reaction tower along a pipeline;
s242: the third pre-treated sewage in the filtering water storage tank enters an ozone reaction tower and is in countercurrent contact with ozone passing through a tower bottom gas distributor, and characteristic pollutants in the third pre-treated sewage react with the ozone;
s243: the reacted ozone is discharged into a tail gas treatment device from a tail gas discharge pipe at the top of the ozone reaction tower, and the ozone is discharged into the atmosphere after residual active oxygen is decomposed;
s243: and the third pretreated sewage after reaction enters a buffer tank.
Further, the ozone supply system comprises a liquid oxygen storage tank, a vaporizer, a safety valve, a pressure gauge, a pressure reducing valve, a pipeline and an ozone generator, wherein the liquid oxygen storage tank is communicated with the ozone generator through the pipeline, and the vaporizer, the safety valve, the pressure gauge and the pressure reducing valve are installed on the liquid oxygen storage tank;
the S241 specifically includes:
s2411: injecting liquid oxygen into the liquid oxygen storage tank, controlling the pressure in the liquid oxygen storage tank through a pressure gauge and a safety valve, converting the liquid oxygen into gas through a vaporizer after the pressure reaches a first preset value, and keeping the output pressure of the gas at a second preset value;
s2412: the gas is decompressed through a decompression valve, the pressure reaches a third preset value after decompression, and the gas is conveyed to an ozone generator;
s2413: ozone is prepared in an ozone generator, and the prepared ozone is conveyed to the bottom of an ozone reaction tower along a pipeline.
Further, the first predetermined value is 0.7 to 1.0MPa, the second predetermined value is 0.3 to 0.5MPa, and the third predetermined value is 0.09 to 0.1 MPa.
Further, the S5 specifically includes:
s51: the mixed sewage enters an SBR biological reaction tank and an AO biological reaction tank from an intermediate water tank, and the organic matters are biodegraded;
s52: a part of the mixed sewage from S51 flows into a sedimentation tank for sludge-water separation, the separated sludge returns to the AO biological reaction tank through a first sludge return pipe, and the separated sewage is subjected to secondary coagulation air flotation treatment;
s53: the other part of the mixed sewage treated by the S51 enters MBR equipment for treatment, and then secondary coagulation air flotation treatment is carried out;
s54: and (4) finishing the treatment of the oily sewage after the second-stage coagulation air flotation.
Further, the number of the A pools and the number of the O pools in the AO biological reaction pool are not less than 2 and 2 respectively;
the time for biodegradation of the mixed sewage in the S51 in the AO biological reaction tank is 35-40h, and the ratio of the mixed sewage entering the S52 to the mixed sewage entering the S53 is 3: 1.
In a second aspect, the present invention provides a treatment system using the above oil-containing wastewater treatment method, comprising: the device comprises a storage tank assembly, a pretreatment device, an intermediate water tank, an SBR biological reaction tank and a coagulation air flotation unit;
the storage tank assembly comprises an oily sewage storage tank and a domestic sewage storage tank, the oily sewage storage tank is communicated with the pretreatment device, and oily sewage enters the pretreatment device from the oily sewage storage tank;
the pretreatment device is also communicated with an intermediate water tank, pretreated oily sewage enters the intermediate water tank, the domestic sewage storage tank is also communicated with the intermediate water tank, and the domestic sewage enters the intermediate water tank from the domestic sewage storage tank and is mixed with the pretreated oily sewage to form mixed sewage;
the middle water tank, the SBR biological reaction tank and the coagulation air flotation unit are sequentially communicated, and the mixed sewage is respectively subjected to biodegradation, mud-water separation and secondary coagulation air flotation treatment.
The invention adds the steps of oil removal, flocculation and coagulation air flotation in the pretreatment stage of the oily sewage treatment process and improves the ozone oxidation process, thereby achieving the following technical effects:
1. the method has the advantages of effectively removing petroleum and suspended matters, reducing ozone consumption in an ozone oxidation stage, improving the removal effect of characteristic pollutants, reducing the toxicity of wastewater and improving the biodegradability of the wastewater.
2. The toxic action of characteristic pollutants on a biochemical system is reduced, and the low-noise biochemical treatment efficiency is exerted.
3. The purpose of catalyzing ozone to oxidize and decompose different target pollutants is realized through the step oxidation process.
Drawings
The above and other objects, features and advantages of exemplary embodiments of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying drawings. Several embodiments of the present invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar or corresponding parts and in which:
FIG. 1 is a process flow diagram showing a method for treating oily sewage according to an embodiment of the present invention;
fig. 2 is a process flow diagram illustrating a process for pretreatment of oil-contaminated water according to an embodiment of the present invention;
FIG. 3 is a process flow diagram illustrating a first degreasing according to an embodiment of the invention;
FIG. 4 is a process flow diagram illustrating ozone oxidation according to an embodiment of the present invention;
fig. 5 is a schematic view illustrating a treatment system of oily sewage according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail with reference to the accompanying drawings, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the examples of the present invention and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise, and "a plurality" typically includes at least two.
It is also noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such article or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in the article or device in which the element is included.
The present invention will be described in detail with reference to specific examples. As shown in fig. 1, a method for treating oily sewage comprises the following steps:
s1: collecting oily sewage in a storage tank, homogenizing and adjusting, and keeping the pH value at 7-9;
s2: after the oily sewage in the storage tank reaches a preset liquid level, discharging the oily sewage into a pretreatment device for pretreatment, wherein the pretreatment comprises oil removal, flocculation, primary coagulation air flotation and ozone oxidation;
s3: discharging the pretreated oily sewage into an intermediate water tank;
s4: continuously and uniformly injecting domestic sewage into the intermediate water tank, and distributing water with oily sewage in the intermediate water tank to form mixed sewage;
s4: and (3) allowing the mixed sewage to enter an SBR biological reaction tank, performing biodegradation on organic substances of the mixed sewage, performing sludge-water separation and secondary coagulation air flotation treatment on the mixed sewage after biodegradation, and finishing the treatment of the oily sewage when the pH value of the mixed sewage reaches 6-9.
In one embodiment, as shown in FIG. 5, a system for treating oily wastewater is provided. The system is provided with a tank assembly for storing sewage, and the tank assembly comprises an oily sewage storage tank and a domestic sewage storage tank. Collecting the oily sewage and collecting the oily sewage into an oily sewage storage tank. Before the pretreatment, the oily sewage in the storage tank is subjected to homogenization regulation, and a specific homogenization regulation method and a suitable device are not specifically limited. And when the oily sewage in the storage tank is collected to a certain liquid level, discharging the oily sewage into a pretreatment device for pretreatment. The height of the liquid level can be preset according to specific treatment scenes and treatment capacity, and the pH value of the oily sewage is kept between 7 and 9 before pretreatment. For example, the indicator of oily sewage after the oil tanker is cleaned in a certain port scene is measured, and specific measurement data is as follows: CODcr≦2500mg/l，NH3-N < 200mg/l, total nitrogen < 350mg/l, oil < 200mg/l, SS < 50mg/l, pH 7-9; CODcrThe oxygen demand measured by using potassium dichromate as an oxidant is referred to.
The oily sewage storage tank is communicated with a pretreatment device, and the pretreatment device comprises an inclined plate separation tank, a coagulation reaction tank, an integrated air flotation reaction tank, a filtering water storage tank and an ozone reaction tower. As shown in fig. 2, the pretreatment process of oily sewage entering the pretreatment device specifically comprises:
s21: the oily sewage enters an inclined plate separation tank for first oil removal to obtain first pretreated sewage;
s22: enabling the first pretreated sewage to enter a coagulation reaction tank added with PAC and/or PAM for flocculation reaction to obtain second pretreated sewage;
s23: the second pre-treated sewage enters an air floatation reaction tank to be subjected to primary coagulation air floatation treatment, and then is filtered to obtain third pre-treated sewage, and the third pre-treated sewage enters a filtering water storage tank;
s24: and the third treated sewage of the filtering water storage tank enters an ozone reaction tower to remove the characteristic pollutants, and then enters a buffer tank to obtain the pretreated oily sewage.
As shown in fig. 3, the first degreasing includes: enabling light oil to flow to an emergency sump oil tank through an oil skimming pipe by gravity, and lifting and recovering sump oil in the emergency sump oil tank by a pump; the bottom of the inclined plate separation tank is provided with a sludge cone hopper which gathers sludge, and the gathered sludge is periodically removed by a sludge discharge pump. On the one hand, the efficiency of sludge removal is improved, on the other hand, the degree of mechanization is improved, and the difficulty of manual operation is reduced. Light oil flows to the emergency sump by gravity through the oil skimming pipe, and oil droplets, suspended matters and water are separated in a static or flowing state. The oil droplets dispersed in water slowly float and layer under the action of buoyancy, and the floating speed of the oil droplets depends on the size of oil droplet particles, the density difference of oil and water, the flowing state and the viscosity of fluid. And then, lifting and recovering sump oil in the emergency sump oil pool by a pump.
The coagulation reaction tank comprises a flocculation stirrer, and plays a role in increasing the flocculation deposition effect on suspended matters in the sewage. The petroleum and suspended matters in the water discharged from the inclined plate separation tank still have high concentration, and if the water is subjected to ozone oxidation and then enters a coagulation air floatation process, the petroleum and suspended matters can excessively consume ozone in an ozone oxidation stage, and finally toxic and harmful substances in the wastewater are difficult to obtain effective oxidative degradation.
Therefore, the water discharged from the inclined plate separation tank is lifted by a water pump to enter a coagulation reaction tank, and is subjected to flocculation reaction by adding PAC (flocculating agent) or PAM (demulsifying agent), and then enters an integrated air floatation reaction tank to remove suspended matters and oil substances in the wastewater. Wherein, the PAC amount can be 400-500mg/L, and 450mg/L is preferred in specific application; the amount of PAM can be 5-10mg/L, and is preferably 7mg/L in specific application; the temperature during the flocculation reaction is controlled below 60 ℃. In order to further improve the effect of reaction treatment, hydrogen peroxide can be added into the coagulation reaction tank, and the adding amount is 1.5 per mill.
Oily sewage enters an integrated air floatation reaction tank after being treated by a coagulation reaction tank for primary coagulation air floatation treatment, a filter is arranged at the rear end of the integrated air floatation reaction tank, effluent after air floatation enters a filtering water storage tank after being filtered by the filter, and then is lifted by a water pump to enter an ozone oxidation stage.
Flocculation, air flotation and filtration are added before ozone oxidation, so that the consumption of a rear-end ozone oxidation stage can be reduced while effective removal of petroleum and suspended matters is realized, the removal efficiency of characteristic pollutants is improved, the toxicity of wastewater is reduced, and the biodegradability of the wastewater is improved.
In order to reduce the toxic effect of characteristic pollutants on a biochemical system and better exert the treatment efficiency of low-cost biochemical treatment, the characteristic pollutants in the wastewater must be effectively removed in a pretreatment stage. The ozone reaction tower is internally provided with a catalyst, a functional filler and a functional structure for improving the internal flow state, strengthening the full and effective removal of gas and water and effectively reducing the reaction time.
The third treatment sewage of the filtering water storage tank enters the ozone reaction tower, and characteristic pollutants are removed, as shown in fig. 4, the third treatment sewage specifically comprises:
s241: starting an ozone supply system, and conveying the prepared ozone to the bottom of an ozone reaction tower along a pipeline;
s242: the third pre-treated sewage in the filtering water storage tank enters an ozone reaction tower and is in countercurrent contact with ozone passing through a tower bottom gas distributor, and characteristic pollutants in the third pre-treated sewage react with the ozone;
s243: the reacted ozone is discharged into a tail gas treatment device from a tail gas discharge pipe at the top of the ozone reaction tower, and the ozone is discharged into the atmosphere after residual active oxygen is decomposed;
s243: and the third pretreated sewage after reaction enters a buffer tank.
The ozone reaction tower is internally provided with a circulating pump, ozone is conveyed to the bottom of the ozone reaction tower through a pipeline and is removed with the sewage in a counter-current way through a gas distributor at the bottom of the tower, so that the content of toxic substances and oily substances in the sewage is reduced, and the biodegradability is improved. Meanwhile, an adjusting valve and a flowmeter are arranged in the oxidation tower and used for controlling the flow of inlet air, a tail gas discharge pipe is arranged at the top of the oxidation tower, and tail gas discharged from the oxidation tower enters a tail gas treatment device to separate residual active oxygen and is discharged at high altitude through a chimney.
The ozone supply system comprises a liquid oxygen storage tank, a vaporizer, a safety valve, a pressure gauge, a pressure reducing valve, a pipeline and an ozone generator, wherein the liquid oxygen storage tank is communicated with the ozone generator through the pipeline, and the vaporizer, the safety valve, the pressure gauge and the pressure reducing valve are arranged on the liquid oxygen storage tank. The preparation and supply of ozone specifically comprises:
s2411: injecting liquid oxygen into the liquid oxygen storage tank, controlling the pressure in the liquid oxygen storage tank through a pressure gauge and a safety valve, converting the liquid oxygen into gas through a vaporizer after the pressure reaches a first preset value, and keeping the output pressure of the gas at a second preset value;
s2412: the gas is decompressed through a decompression valve, the pressure reaches a third preset value after decompression, and the gas is conveyed to an ozone generator;
s2413: ozone is prepared in an ozone generator, and the prepared ozone is conveyed to the bottom of an ozone reaction tower along a pipeline.
Wherein the first preset value is the working pressure of the liquid oxygen storage tank, the range is 0.7-1.0MPa, and the specific application is preferably 0.8 MPa; the second preset value is the pressure of the gasified outlet gas, the range is 0.3-0.5MPa, and the preferred value in the specific application is 0.4 MPa; the third predetermined value is the pressure after depressurization, ranging from 0.09 to 0.1MPa, preferably 0.095MPa for a particular application.
The ozone oxidation process can fully utilize the oxidation characteristics of different oxidation groups (such as hydroxyl free radicals and oxygen free radicals) under the control of different reaction conditions and operation parameters according to the composition of pollutants in the oily wastewater, and induce the rapid chemical reaction (such as addition reaction, substitution reaction and the like) between a specific oxidation group and a pollutant functional group, thereby realizing the efficient selective degradation of chromogen groups such as C-C, C-O and the like and highly toxic and difficultly biodegradable substances such as aromatic hydrocarbons, heterocyclic rings and the like. Meanwhile, the ozone oxidation process is also used for removing oil from the oily sewage for the second time, and the oil content of the oily sewage can be greatly reduced on the basis of the first oil removal of the inclined plate separation tank in the pretreatment process.
In a part of reaction stages, the problem of poor selectivity of hydroxyl radical (OH) oxidation to target pollutants in wastewater is avoided through process regulation, meanwhile, the problem of competition among oxidants is avoided, and the efficiency of oxidation reaction is effectively improved. In another stage of oxidation reaction, the characteristic of high oxidation potential of hydroxyl radical (OH) is fully utilized to make it react with organic matter in waste water, the organic radical produced in the reaction can continuously take part in chain reaction of hydroxyl radical, or after producing organic peroxide radical, further produce oxidative decomposition reaction until it is degraded into final product CO2And H2And O. Through the step oxidation process, the purpose of decomposing different target pollutants by ozone oxidation is achieved.
The ozone oxidation realizes the efficient selective degradation of organic poisons and difficult degradation, can effectively improve the biochemical level of sewage, and obviously improves the bubbling phenomenon in the biochemical stage; and the chromophoric group can be destroyed, and the decolorizing effect is very obvious.
To the oily sewage after wasing the oil ship in certain harbour scene, after the preliminary treatment, measure the index: CODcr≦1500mg/l，NH3-N < 200mg/l, total nitrogen < 350mg/l, oil < 15mg/l, SS < 50mg/l, pH 7-9. After pretreatment, the Chemical Oxygen Demand (COD)cr) Saving 40% and oil removing amount up to 92.5%.
Discharging the pretreated oily sewage into an intermediate water tank, wherein the intermediate water tank is a distribution tank, and carrying out oily sewage treatmentAnd distributing domestic sewage. Oily sewage in the buffer pool is discharged into the middle water pool through the lifting pump, and domestic sewage is continuously and uniformly discharged into the middle water pool from the domestic sewage storage tank through the water pump to form mixed sewage. Before entering the intermediate basin, the indexes of the domestic sewage are measured, wherein: CODcr≦700mg/l，NH3-N ≦ 20mg/l, pH 6-8. The water distribution ratio of the oily sewage and the domestic sewage can be adjusted according to the actual application scene, and is not specifically limited herein.
And (3) the mixed sewage enters an SBR (sequencing batch reactor) biological reaction tank, the organic substances of the mixed sewage are biodegraded, the mixed sewage after biodegradation is subjected to mud-water separation and secondary coagulation air flotation treatment, and the pH value of the mixed sewage reaches 6-9, namely the whole oily sewage treatment is completed.
The treatment process of the oily sewage also comprises an AO (anaerobic-aerobic) biological reaction tank, a sedimentation tank and MBR (membrane biological reaction) equipment;
s5 specifically includes:
s51: the mixed sewage enters an SBR biological reaction tank and an AO biological reaction tank from an intermediate water tank, and the organic matters are biodegraded;
s52: a part of the mixed sewage from S51 flows into a sedimentation tank for sludge-water separation, the separated sludge returns to the AO biological reaction tank through a first sludge return pipe, and the separated sewage is subjected to secondary coagulation air flotation treatment;
s53: the other part of the mixed sewage treated by the S51 enters MBR equipment for treatment, and then secondary coagulation air flotation treatment is carried out;
s54: and (4) finishing the treatment of the oily sewage after the second-stage coagulation air flotation.
The oily sewage which finishes the whole treatment process can be discharged into an urban pipe network after reaching the standard.
In the specific step of S5, the number of A pools in the AO biological reaction pool is not less than 2, and the number of O pools in the AO biological reaction pool is not less than 2; the time of the mixed sewage in the S51 for AO biodegradation is 35-40h, the time of biodegradation in a specific embodiment of a certain scene application is 37.5h, and the ratio of the mixed sewage entering the S52 for mud-water separation and sludge return to the mixed sewage entering the S53 for MBR equipment treatment is 3: 1.
After the whole process of treating the oily sewage is completed, the water quality index of the produced water is tested: CODcr≦500mg/l，NH3-N < 45mg/l, total nitrogen < 70mg/l, oil < 15mg/l, pH 6-9.
Comparing the indexes of the pretreated oily sewage with the indexes of the whole oily sewage treatment process, and giving a basic numerical value of the biochemical removal rate: CODcr≥54.5％，NH3N is more than or equal to 55 percent, and total nitrogen is more than or equal to 60 percent. The treated wastewater meets the discharge requirement, is brought into an urban pipe network, and is conveyed to a town sewage treatment station through the urban pipe network for further treatment and discharge.
The foregoing describes preferred embodiments of the present invention, and is intended to provide a clear and concise description of the spirit and scope of the invention, and not to limit the same, but to include all modifications, substitutions, and alterations falling within the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A method for treating oily sewage is characterized by comprising the following steps:
s1: collecting oily sewage in a storage tank, homogenizing and adjusting, and keeping the pH value at 7-9;
s2: after the oily sewage in the storage tank reaches a preset liquid level, discharging the oily sewage into a pretreatment device for pretreatment, wherein the pretreatment comprises oil removal, flocculation, primary coagulation air flotation and ozone oxidation;
s3: discharging the pretreated oily sewage into an intermediate water tank;
s4: continuously and uniformly injecting domestic sewage into the intermediate water tank, and distributing water with oily sewage in the intermediate water tank to form mixed sewage;
s5: and (3) allowing the mixed sewage to enter an SBR biological reaction tank, performing biodegradation on organic substances of the mixed sewage, performing sludge-water separation and secondary coagulation air flotation treatment on the biodegraded mixed sewage, and finishing the treatment of the oily sewage when the pH value of the mixed sewage reaches 6-9.
2. The processing method according to claim 1, wherein the S2 specifically includes:
s21: discharging the oily sewage into an inclined plate separation tank for first oil removal to obtain first pretreated sewage;
s22: the first pretreated sewage enters a coagulation reaction tank added with PAC and/or PAM, and is stirred and subjected to flocculation reaction to obtain second pretreated sewage;
s23: the second pre-treated sewage enters an air floatation reaction tank to be subjected to primary coagulation air floatation treatment, and then is filtered to obtain third pre-treated sewage, and the third pre-treated sewage enters a filtering water storage tank;
s24: and the third pretreated sewage of the filtering water storage tank enters an ozone reaction tower to remove the characteristic pollutants, and then enters a buffer tank to obtain pretreated oily sewage.
3. The processing method according to claim 2, wherein the S21 specifically includes:
s211: carrying out oil-water separation on the oily sewage in an inclined plate separation tank;
s212: the separated light oil flows to an emergency sump oil tank through an oil skimming pipe and is lifted and recovered by a pump;
s213: collecting oily sludge into a sludge cone hopper at the bottom of the inclined plate separation tank, and periodically discharging the oily sludge into an oily sludge tank;
s214: and discharging light oil and oily sludge to obtain first pretreated sewage.
4. The method as claimed in claim 2, wherein the concentration of the PAC added is 400-500mg/L, the concentration of the PAM added is 5-10mg/L, and the temperature of the second pre-treated wastewater is less than or equal to 60 ℃.
5. The processing method according to claim 2, wherein the S24 specifically includes:
s241: starting an ozone supply system, and conveying the prepared ozone to the bottom of an ozone reaction tower along a pipeline;
s242: the third pre-treated sewage in the filtering water storage tank enters an ozone reaction tower and is in countercurrent contact with ozone passing through a tower bottom gas distributor, and characteristic pollutants in the third pre-treated sewage react with the ozone;
s243: the reacted ozone is discharged into a tail gas treatment device from a tail gas discharge pipe at the top of the ozone reaction tower, and the ozone is discharged into the atmosphere after residual active oxygen is decomposed;
s243: and the third pretreated sewage after reaction enters a buffer tank.
6. The process of claim 5, wherein the ozone supply system comprises a liquid oxygen storage tank, a vaporizer, a safety valve, a pressure gauge, a pressure reducing valve, a pipe, and an ozone generator, the liquid oxygen storage tank is communicated with the ozone generator through the pipe, and the vaporizer, the safety valve, the pressure gauge, and the pressure reducing valve are mounted on the liquid oxygen storage tank;
the S241 specifically includes:
s2411: injecting liquid oxygen into the liquid oxygen storage tank, controlling the pressure in the liquid oxygen storage tank through a pressure gauge and a safety valve, converting the liquid oxygen into gas through a vaporizer after the pressure reaches a first preset value, and keeping the output pressure of the gas at a second preset value;
s2412: the gas is decompressed through a decompression valve, the pressure reaches a third preset value after decompression, and the gas is conveyed to an ozone generator;
s2413: ozone is prepared in an ozone generator, and the prepared ozone is conveyed to the bottom of an ozone reaction tower along a pipeline.
7. The process according to claim 6, characterized in that said first predetermined value is comprised between 0.7 and 1.0MPa, said second predetermined value is comprised between 0.3 and 0.5MPa and said third predetermined value is comprised between 0.09 and 0.1 MPa.
8. The processing method according to claim 1, wherein the S5 specifically includes:
s51: the mixed sewage enters an SBR biological reaction tank and an AO biological reaction tank from an intermediate water tank, and the organic matters are biodegraded;
s52: a part of the mixed sewage from S51 flows into a sedimentation tank for sludge-water separation, the separated sludge returns to the AO biological reaction tank through a first sludge return pipe, and the separated sewage is subjected to secondary coagulation air flotation treatment;
s53: the other part of the mixed sewage treated by the S51 enters MBR equipment for treatment, and then secondary coagulation air flotation treatment is carried out;
s54: and (4) finishing the treatment of the oily sewage after the second-stage coagulation air flotation.
9. The process of claim 8, wherein the number of a pools and the number of O pools in said AO bioreactor are not less than 2;
the time for biodegradation of the mixed sewage in the S51 in the AO biological reaction tank is 35-40h, and the ratio of the mixed sewage entering the S52 to the mixed sewage entering the S53 is 3: 1.
10. An oily sewage treatment system to which the treatment method according to any one of claims 1 to 9 is applied, comprising: the device comprises a storage tank assembly, a pretreatment device, an intermediate water tank, an SBR biological reaction tank and a coagulation air flotation unit;
the storage tank assembly comprises an oily sewage storage tank and a domestic sewage storage tank, the oily sewage storage tank is communicated with the pretreatment device, and oily sewage enters the pretreatment device from the oily sewage storage tank;
the pretreatment device is also communicated with an intermediate water tank, pretreated oily sewage enters the intermediate water tank, the domestic sewage storage tank is also communicated with the intermediate water tank, and the domestic sewage enters the intermediate water tank from the domestic sewage storage tank and is mixed with the pretreated oily sewage to form mixed sewage;
the middle water tank, the SBR biological reaction tank and the coagulation air flotation unit are sequentially communicated, and the mixed sewage is respectively subjected to biodegradation, mud-water separation and secondary coagulation air flotation treatment.
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