Advanced treatment method and device for oily wastewater of ship

Abstract

The invention relates to the technical field of sewage treatment, and discloses an advanced treatment method and device for ship oily wastewater, and the method comprises the following steps: carrying out preliminary filtration on the ship oily wastewater to remove suspended solids and particulate matters so as to obtain first oily wastewater; the first oily wastewater is subjected to coalescence separation treatment, floating oil, dispersed oil and a small part of emulsified oil in the wastewater are removed, the oil content in the wastewater is reduced to 500 ppm or below, and second oily wastewater is obtained; the second oily wastewater is subjected to cross-flow ultrafiltration deep treatment, emulsified oil and dissolved oil are intercepted, produced water and concentrated water are obtained, and the concentrated water serves as third oily wastewater; the third oil-containing wastewater flows back to the first oil-containing wastewater, and discharged water is obtained after the produced water is detected to be qualified. The invention provides a primary filtration, coalescence separation and ultrafiltration three-stage circulating filtration method, emulsified oil and dissolved oil can be efficiently separated and removed, oil resource recovery is realized, and membrane pollution is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and in particular to a method and device for deep treatment of ship oily wastewater. Background Art

[0002] With the development of the global economy, the total tonnage and number of ships in the world have increased, and the discharge of oily wastewater from ships has become increasingly larger, causing more and more serious pollution to the marine environment. According to the definitions given in the "Ship Pollutant Discharge Standard" (GB 3552-2018) and the "MARPOL73 / 78" convention, ship oily wastewater mainly refers to wastewater containing crude oil, petroleum derivatives and their residues generated during ship transportation. It mainly comes from leakage of ship power system machinery and residual oil products left behind in cargo, and also includes bilge water in ship engine rooms and tank washing water of oil tankers. Treating ship oily wastewater can reduce pollution to the ocean. The treatment and resource recycling of ship oily wastewater is an important part of ship pollution prevention.

[0003] According to the form of existence in water, ship oily wastewater can be divided into floating oil, dispersed oil, emulsified oil and dissolved oil. Among them, floating oil and dispersed oil have larger particle sizes and are easily removed using conventional treatment methods; while the diameter of emulsified oil particles is generally 0.1~10 μm, and the minimum particle size of emulsified oil droplets treated by coalescence is 5~10 μm; the size of dissolved oil is usually below 0.1 μm, which is not easy to separate and remove. Compared with traditional oily wastewater, ship oily wastewater has complex pollutant components, high proportion of emulsified oil and dissolved oil, and is difficult to separate. Therefore, removing emulsified oil and dissolved oil from oily wastewater is the key to effectively treat oily wastewater. Traditional oily wastewater treatment processes mainly include gravity separation, coagulation, filtration separation, flotation, coalescence separation, chemical oxidation, biofilm, activated sludge and ultrasonic methods. Most of them are based on physical processes and supplemented by demulsification processes, and oil and water are separated according to the different densities of oil and water, such as demulsification + flotation process, gravity separation process, etc. However, it is difficult for the effluent to meet the discharge requirements by simply using filtration technology. Therefore, the main development direction is to develop integrated, intelligent and efficient marine oily wastewater treatment equipment to meet the water supply needs of ships during navigation and reduce the pollution of wastewater to the marine environment.

[0004] In the process of realizing the present invention, the inventors found that there are at least the following problems in the prior art: the oil in the oily wastewater by chemical treatment methods cannot be recycled; it is difficult to effectively remove small-sized emulsified oil and dissolved oil by conventional physical processes; conventional membrane treatment of oily wastewater is prone to membrane clogging and there are problems with concentrated water treatment.

[0005] It should be noted that the statements herein merely provide background information related to the present application and do not necessarily constitute prior art. Summary of the invention

[0006] To this end, the present invention proposes a novel method for deep treatment of ship oily wastewater that can solve at least part of the above-mentioned problems.

[0007] This application adopts the following technical solutions:

[0008] The present application provides a method for deep treatment of ship oily wastewater, the method comprising: performing preliminary filtration on the ship oily wastewater to remove suspended matter and particulate matter to obtain first oily wastewater; performing agglomeration and separation treatment on the first oily wastewater to remove floating oil, dispersed oil and a small part of emulsified oil in the wastewater, and reducing the oil content in the wastewater to below 500 ppm to obtain second oily wastewater; performing cross-flow ultrafiltration deep treatment on the second oily wastewater to intercept emulsified oil and dissolved oil to obtain produced water and concentrated water, and the concentrated water is used as third oily wastewater; the third oily wastewater is refluxed to the first oily wastewater, and the produced water is obtained as discharge water after being tested as qualified.

[0009] Preferably, the oil content of the ship oily wastewater is less than 4000 ppm.

[0010] Preferably, the preliminary filtration uses a precision filter to reduce the turbidity of the oily wastewater. The precision filters are arranged in series and include at least one precision filter; each of the precision filters is provided with an odd number of filter elements.

[0011] Preferably, the coalescence and separation treatment includes using an oil-water coalescence separator to remove floating oil, dispersed oil and part of the emulsified oil in the water to ensure that the oil content in the second oil-containing wastewater is reduced to below 500 ppm; the oil substance in the oil-water coalescence separator is pumped into an oil storage tank for storage at regular intervals.

[0012] Preferably, the cross-flow ultrafiltration deep treatment includes separation using a ceramic ultrafiltration membrane assembly, wherein at least one group of the ceramic ultrafiltration membrane assembly is provided, and the ultrafiltration membrane assembly further comprises an inlet end, a produced water outlet end and a concentrated water outlet end, and an odd number of the ceramic ultrafiltration membranes are provided.

[0013] Preferably, the ceramic ultrafiltration membrane assembly adopts SiC ceramic ultrafiltration membrane with a filtration accuracy of 40 nm and a pure water flux of 2-3 m 3 / (m 2 ·h), operating transmembrane pressure difference 0.05~0.25 MPa, membrane surface flow rate 1.0~2.0 m / s.

[0014] Preferably, the produced water is detected using an oil concentration meter, and produced water whose oil content meets the standard requirements can be discharged, while unqualified produced water is returned to the ship's oily wastewater collection tank.

[0015] Preferably, the ultrafiltration membrane assembly is cleaned by a cleaning agent combination of 5% NaOH+0.5% NaClO+0.2% SDBS in combination with air and water for simultaneous backwashing, and the backwashing cycle is set to 60 min.

[0016] In summary, in order to overcome the shortcomings of the existing technology, such as the inability to treat special impurities such as emulsified oil and dissolved oil, the inability to guarantee the removal effect of general oil pollution, and the inconvenience of equipment use and maintenance, the present invention provides a ship oily wastewater treatment process and device using ceramic membrane ultrafiltration technology, which can effectively remove most of the dissolved oil and emulsified oil through the three-stage circulation filtration process of "precision filter + oil-water coalescing separator + silicon carbide ceramic ultrafiltration membrane" to meet the relevant requirements of GB3552-2018 "Ship Water Pollutant Emission Control Standard" and GB / T 4795-2009 "15 ppm Bilge Water Separator", that is, the discharge standard of oily wastewater is less than 15 mg / L; by setting backwashing tanks and wastewater return pipelines, an efficient and highly automated wastewater deep treatment system is realized, which improves the efficiency of oil resource recovery and wastewater treatment.

[0017] The present application also proposes a ship oily wastewater deep treatment device, which includes a water inlet, a water collection tank, a precision filter group, an oil-water coalescing separator, an ultrafiltration membrane assembly and a water outlet in order of water flow direction. A water inlet pump is provided between the water collection tank and the precision filter group; a circulation pump is provided between the precision filter group and the oil-water coalescing separator; the oil-water coalescing separator is provided with an oil storage cabinet for storing filtered substances; a ceramic ultrafiltration membrane for filtering emulsified oil and impurities in water is provided inside the ultrafiltration membrane assembly, and a backwash tank for cleaning the ultrafiltration membrane assembly is provided outside; an oil concentration meter is provided between the ultrafiltration membrane assembly and the water outlet, and the ultrafiltration membrane assembly is also provided with a reflux pipeline connecting the circulation pump and the water collection tank.

[0018] Preferably, the inlet and outlet of the water inlet pump are provided with a bypass pipeline directly connected to the water collecting tank and the precision filter group; whether to use a booster pump to meet the water inlet pressure requirement is selected according to the water inlet pressure, which can save energy consumption.

[0019] Preferably, the precision filter group is arranged in series, including at least one precision filter, and each precision filter is provided with an odd number of filter elements; the use of multiple filter elements in series greatly improves the pretreatment efficiency of the device and ensures the smooth operation of subsequent membrane components.

[0020] Preferably, a drain port is provided at the bottom of the oil-water coalescing separator, and an external discharge pipeline and a valve are provided in the oil storage tank; waste water after cleaning the oil-water coalescing separator can be discharged through the drain port, and the oil substances are stored in the oil storage tank after being separated and then processed uniformly, which is environmentally friendly.

[0021] Preferably, at least one group of ultrafiltration membrane components is provided, and the ultrafiltration membrane components also include a water inlet, a water outlet and a concentrated water outlet. The ceramic ultrafiltration membrane is provided with an odd number; the use of multiple membranes in series can improve the recovery rate of the membrane and the efficiency of treating oil and other impurities. The ultrafiltration membrane component uses SiC ceramic ultrafiltration membrane, the outer diameter of the pipeline is 60 mm, the channel diameter is 4 mm, the number of channels is 37, the filtration accuracy is 40 nm, and the pure water flux is 2~3 m 3 / (m 2 ·h). The operating transmembrane pressure difference is 0.05~0.25 MPa, and the membrane surface flow rate is 1.0~2.0 m / s.

[0022] Preferably, the water outlet end of the ultrafiltration membrane assembly is connected to the backwash tank, and the concentrated water outlet end is connected to the circulation pump and the water collecting tank respectively; when there are too many impurities in the raw water, the oil concentration meter will show that the water quality is unqualified, and the unqualified water will flow back into the water collecting tank and the process flow can be repeated until the water outlet requirements are met.

[0023] Preferably, the ultrafiltration membrane assembly adopts cross-flow filtration, the water inlet end is directly connected to the oil-water coalescing separator, and the water outlet end is directly connected to the bypass line of the outlet; in the case of ultrafiltration membrane blockage, water is directly discharged from the bypass line to ensure the safe operation of the device. In addition, according to the oil concentration of the oil-water separation coalescer outlet water displayed by the oil concentration meter, it can be selected whether to connect the ultrafiltration membrane assembly for deep treatment to achieve the purpose of saving energy consumption.

[0024] Preferably, the backwash tank adopts chemical washing or air washing, and is provided with a matching chemical adding mechanism or air supply mechanism; chemical washing or air washing is selected according to the degree of membrane pollution to save resources and energy consumption; the ultrafiltration membrane assembly is cleaned by a combination of 5% NaOH + 0.5% NaClO + 0.2% SDBS cleaning agent combined with air and water for simultaneous backwashing, and the backwashing cycle is set to 60 min. Among the single type of cleaning agents, the oxidizing cleaning agent has the best cleaning effect on irreversible pollution in ceramic membranes. Since irreversible pollution accounts for a large proportion of pollution in ceramic membranes, the concentration of the oxidant can be increased in the actual cleaning process, and other types of cleaning agents can be combined to achieve good pollution removal and flux recovery effects.

[0025] Preferably, the treatment device adopts a wastewater zero discharge system and is provided with an automatic operation safety protection module and an alarm module; the oily wastewater is not discharged after treatment, and the fully automated operation and monitoring can also facilitate the use and management of the staff.

[0026] Based on the above technical solution, it can be seen that compared with the prior art, the ship oily wastewater treatment device and treatment method of the present invention can achieve the following beneficial effects:

[0027] (1) The three-stage circulating filtration technology of precision filter + coalescing separator + SiC ceramic membrane ultrafiltration can efficiently separate and remove emulsified oil and dissolved oil, ensuring that the oil content of the effluent water is less than 15ppm, and can meet the higher 10ppm and 5ppm treatment standards.

[0028] (2) The oil particles in the effluent from the initial filtration and coalescence separation treatment are small in size, and further ceramic membrane ultrafiltration treatment reduces membrane pollution; membrane ultrafiltration deep treatment increases the concentration of emulsified oil and dissolved oil in the oily wastewater, increases the oil particle size, and reflux coalescence separation treatment further effectively recovers the emulsified oil and dissolved oil of particle sizes that cannot be recovered in the original oily wastewater, thereby improving the efficiency of oil resource recovery and wastewater treatment.

[0029] (3) The backwash tank is installed to enable the device to have a regular automatic cleaning function. A combination of cleaning agents and air and water are used for simultaneous backwashing, with a recovery rate of 96.25%, saving costs.

[0030] (4) The device adopts a wastewater depth system and is equipped with automatic control and management functions, including precision filter protection function, automatic backwashing function, automatic shutdown and alarm function when the device is operating abnormally, emergency shutdown function, etc., to reduce manual operation and realize the efficiency and intelligence of the device.

[0031] The above description of the technical solution of the present application is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Also, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0033] Figure 1 This is a schematic diagram of the steps of the method for deep treatment of ship oily wastewater in an embodiment of the present application;

[0034] Figure 2 It is a schematic diagram of the process of the deep treatment device for ship oily wastewater in the embodiment of the present application;

[0035] Figure 3 is a schematic structural diagram of a ceramic ultrafiltration membrane assembly in an embodiment of the present application;

[0036] Figure 4This is a diagram showing the effect of ceramic ultrafiltration membrane c on removing oily wastewater under different water-oil concentration conditions in Example 2 of the present application;

[0037] Figure 5 This is a diagram of membrane flux recovery of different cleaning combination methods in Example 3 of the present application;

[0038] Figure 6 This is a graph showing the relationship between the water production rate, effective water production rate and time of the ceramic ultrafiltration membrane in Example 4 of the present application;

[0039] Figure 7 It is a device structure diagram of a device for deep treatment of ship oily wastewater in an embodiment of the present application.

[0040] In the figure: 1-water inlet, 2-water collecting tank, 3-water inlet pump, 4-precision filter group, 41-precision filter, 5-circulation pump, 6-oil-water coalescing separator, 61-drain port, 62-oil storage cabinet, 7-ultrafiltration membrane assembly, 71-ceramic ultrafiltration membrane, 72-ultrafiltration membrane water inlet end, 73-produced water outlet end, 74-concentrated water outlet end, 8-backwash tank, 9-oil concentration meter, 10-water outlet. DETAILED DESCRIPTION

[0041] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0042] The inventive concept of the present invention is that the oil in the oily wastewater cannot be recycled by chemical treatment methods, the conventional physical process is difficult to effectively remove small-sized emulsified oil and dissolved oil, and the conventional membrane treatment of oily wastewater is prone to membrane clogging and has problems with concentrated water treatment. This application uses a three-stage circulating filtration process of "precision filtration + oil-water coalescence separation + ceramic ultrafiltration" to effectively remove most of the dissolved oil and emulsified oil, realize an efficient and highly automated wastewater deep treatment system, and improve the efficiency of oil resource recovery and wastewater treatment.

[0043] The present application provides a method for deep treatment of ship oily wastewater, such as Figure 1 shown.

[0044] Step S1, preliminarily filtering the ship's oily wastewater to remove suspended matter and particulate matter to obtain first oily wastewater.

[0045] Specifically, the oily wastewater from ships in the water collection tank is sent to the precision filter for preliminary cleaning to remove suspended matter and particulate matter, reduce turbidity, and prevent large particles in the wastewater from entering subsequent treatment units and causing membrane pollution problems.

[0046] Step S2, subjecting the first oily wastewater to a coagulation and separation treatment to remove floating oil, dispersed oil and a small portion of emulsified oil in the wastewater, and reducing the oil content in the wastewater to below 500 ppm to obtain second oily wastewater.

[0047] Specifically, the filtered oil and water enter the coalescing separator. The coalescing separator of this device adopts a two-stage filter element type coalescing separator. The specific working principle is to first use the first-stage nano-material filter element with aggregation induction to demulsify the oil droplets, so that the floating oil, dispersed oil and most of the emulsified oil droplets with smaller particle sizes in the water are coalesced into large oil droplets, and then the hydrophilicity (oleophobicity) of the second-stage filter element is used to intercept the coalesced large particle size oil droplets on the surface of the filter element, thereby achieving the purpose of removing floating oil, dispersed oil and a small part of emulsified oil in the oil and water. The oil substances in the coalescing separator are pumped into the oil storage cabinet for separation and storage at regular intervals. The coalescing separator can withstand the impact of high oil content, and has a removal rate of more than 90% for oil substances in water, ensuring that the oil content in the water is reduced to below 500 ppm.

[0048] Step S3, subjecting the second oil-containing wastewater to cross-flow ultrafiltration deep treatment to intercept emulsified oil and dissolved oil to obtain produced water and concentrated water, and the concentrated water is used as the third oil-containing wastewater.

[0049] Specifically, the oily wastewater treated by the oil-water coalescing separator then enters the ceramic membrane ultrafiltration membrane for separation, and the emulsified oil and dissolved oil are further retained by utilizing the filtration principle of dynamic membrane cross-flow filtration and the hydrophilicity (oleophobicity) of the ceramic membrane, so that the oil content in the effluent meets the relevant requirements of GB3552-2018 "Ship Water Pollutant Emission Control Standards" and GB / T 4795-2009 "15 ppm Bilge Water Separator", that is, the effluent oil content is less than 15 ppm, and can meet the higher 10 ppm and 5 ppm treatment standard requirements.

[0050] Step S4, returning the third oily wastewater to the first oily wastewater, and obtaining discharge water after the produced water is tested and found to be qualified.

[0051] Specifically, unqualified produced water flows back into the water tank, and concentrated water flows back to the front end of the circulation pump to continue circulating, maintaining a certain membrane surface flow rate on the surface of the ceramic membrane in the circulation system and reducing membrane pollution.

[0052] The present application also provides a marine oily wastewater treatment device, such as Figure 2 , Figure 3As shown, the water inlet 1, water collecting tank 2, precision filter group 4, oil-water coalescing separator 6, ultrafiltration membrane assembly 7 and water outlet 10 are included in sequence in the order of water flow direction. A water inlet pump 3 is provided between the water collecting tank 2 and the precision filter group 4; a circulation pump 5 is provided between the precision filter group 4 and the oil-water coalescing separator 6; the oil-water coalescing separator 6 is provided with an oil storage cabinet 62 for storing filtered substances; a ceramic ultrafiltration membrane 71 for filtering emulsified oil and impurities in water is provided inside the ultrafiltration membrane assembly 7, and a backwash tank 8 for cleaning the ultrafiltration membrane assembly 7 is provided outside; an oil concentration meter 9 is provided between the ultrafiltration membrane assembly 7 and the water outlet 10, and the ultrafiltration membrane assembly 7 is also provided with a reflux pipeline connecting the circulation pump 5 and the water collecting tank 2.

[0053] Specifically, the inlet and outlet of the water inlet pump 3 are provided with a bypass pipeline directly connected to the water collecting tank 2 and the precision filter group 4 .

[0054] Specifically, the precision filter group 4 is arranged in series, including at least one precision filter 41, and each precision filter 41 is provided with an odd number of filter elements; in the embodiment, the precision filter element is a single-core 10-inch, filtration accuracy 5 μm, PP spray-melt material filter element; the number of filter elements is 3.

[0055] Specifically, the bottom of the oil-water coalescing separator 6 is provided with an emptying port 61, and the oil storage cabinet 62 is provided with an external discharge pipeline and a valve. In the embodiment, the oil-water coalescing separator uses a combination of "2 coalescing filter elements + 2 separation filter elements", with a filtration accuracy of 3μm filter element, and a processing capacity of 5~6 m 3 / h, the oil content of inlet water shall be below 4000 ppm.

[0056] Specifically, at least one group of the ultrafiltration membrane assembly 7 is provided, and the ultrafiltration membrane assembly 7 also includes an water inlet end 72, a produced water outlet end 73 and a concentrated water outlet end 74, and an odd number of the ceramic ultrafiltration membranes 71 are provided; in the embodiment, a 5-core membrane shell is adopted, the shell material is stainless steel, the ceramic ultrafiltration membrane filter element material is silicon carbide, and the filtration accuracy is 40 nm.

[0057] Specifically, the produced water outlet 73 is connected to the backwash tank 8, and the concentrated water outlet 74 is connected to the circulation pump 5 and the water collecting tank 2 respectively.

[0058] Specifically, the water inlet end 72 and the water outlet end 73 of the ultrafiltration membrane assembly 7 are provided with a bypass pipeline directly connecting the oil-water coalescing separator 6 and the water outlet 10 .

[0059] Specifically, the backwash tank 8 adopts a chemical washing or air washing method and is provided with a matching chemical adding mechanism or air supply mechanism.

[0060] Specifically, the treatment device adopts a wastewater zero discharge system and is provided with an automatic operation safety protection module and an alarm module.

[0061] The working process of the present invention is as follows.

[0062] like Figure 1 , Figure 2 and Figure 3 As shown, the oily sewage from the bilge flows into the water collecting tank from the water inlet. After the equipment is stable, the equipment is powered on, the water inlet pump is turned on, and the valves of the main circuit inside the equipment are opened. The water inlet pump provides water source pressure for the precision filter pretreatment part. If the inlet water pressure is sufficient, the water inlet pump and the one-way valve in front of it can be closed, and the two manual valves can be opened to allow the oily sewage in the water collecting tank to flow into the precision filter group from the bypass line to remove suspended matter, particulate matter, colloids and other impurities in the oily sewage. The oily sewage after filtering by the precision filter continues to flow into the circulation pump, and the circulation pump boosts the water supply for the oil-water coalescing separator and the ultrafiltration membrane assembly.

[0063] The filtered sewage enters the oil-water coalescing separator through the circulation pump. The oil-water coalescing separator is made of modified glass fiber. The surface of the filter element is treated with hydrophobic or oleophobic treatment to meet various precision level requirements. The internal structure adopts a 2+2 method of coalescing + separation filter element. Each filter element can be designed with different flow rates according to different water qualities. The oil-water coalescing separator can remove floating oil, dispersed oil and most of the emulsified oil in the water, reducing the oil content in the water to below 500 ppm, and then enters the ceramic ultrafiltration membrane for filtration to ensure that the subsequent effluent oil content meets the requirements.

[0064] The water from the oil-water coalescing separator enters the ultrafiltration membrane assembly for ultrafiltration, flows into the central tube through the water production channel, and then flows out at the water outlet. As the sewage continuously passes through the ultrafiltration membrane, the emulsified oil and dissolved oil in the influent are fully removed. The water produced by the device meets the requirements of GB3552-2018 "Ship Water Pollutant Emission Control Standards", and the oil content is less than 15 ppm.

[0065] The device adopts a zero-discharge system for wastewater. The concentrated water from the ultrafiltration device can enter the circulation pump or the water collecting tank through the reflux pipe. Qualified produced water can flow out directly through the outlet water, and unqualified produced water can enter the water collecting tank through the reflux pipe for re-treatment.

[0066] The present invention adopts an automatic operation safety protection system, which can shut down for protection and send out an alarm signal, and integrates all parts to form an integrated device; the device is equipped with an automatic oil drainage system, which has an oil-water interface monitoring and alarm function, and the automatic control part of the device can be converted into manual control, and the electric control box realizes functions such as pump start, stop, and oil drainage control; the ceramic membrane is automatically backwashed at the time set by the program to extend the service life of the membrane; in the process of treating oily wastewater, when abnormal conditions such as oil-water coalescing separator and excessive pressure of ceramic membrane occur, the device automatically shuts down and issues an alarm reminder; when the device is abnormal, it can be shut down by pressing the emergency stop button. Example 1

[0067] The performance screening test of ceramic membranes was carried out on an Al2O3 ceramic membrane a and two SiC ceramic membranes b and c. The main difference between the two SiC ceramic membranes b and c is the different pure water flux. The pure water flux of membrane b is 3~4 m 3 / (m 2 h), pure water flux of membrane c is 2~3 m 3 / (m 2 h).

[0068] The effect of transmembrane pressure drop (TMP) on the flux of membrane modules. After the water inlet pump is turned on, the reverse osmosis water in the water collection tank enters the test device for circulation test. The test adopts the cross-flow filtration method and sets the water inlet volume to 3 m 3 / h, and continuously increase the membrane inlet pressure to increase the water production. Replace the membrane assembly and repeat the operation. Change TMP from 0.01 MPa to 0.2 MPa. The pure water flux J of the three membranes increases with the increase of transmembrane pressure difference TMP. When TMP reaches 0.2 MPa, the pure water flux J of ceramic ultrafiltration membranes a, b, and c are 1.24 m 3 / (m 2 ·h)、3.04 m 3 / (m 2 ·h)、2.85 m 3 / (m 2 h). The pure water flux of the two SiC ceramic ultrafiltration membranes and components is 2 to 3 times that of the Al2O3 ceramic ultrafiltration membrane and components.

[0069] Effect of different membrane surface flow rate conditions on membrane flux. During the test, cross-flow filtration was used, and oil-water (diesel fuel oil: marine system oil = 1:1) with a water-oil concentration of 500 ppm was used as the inlet water for the test. Due to the large water flux, in order to compare the performance of several ceramic ultrafiltration membranes, the water valve opening was reduced, and the water flow rate was initially set to 20L / h. Each time the water flow rate was adjusted, the water flow rate increment was 20 L / h. In the initial stage of operation, when the flux was low, the water flux and working pressure of the membrane assembly were basically stable; as the water flux increased, the working pressure increased, and the water flux fluctuated and showed a downward trend; the water flux continued to increase, the working pressure increased, and the membrane flux decline trend intensified; in the final stage, the working pressure increase gradually eased, and the membrane flux continued to decline. The critical flux of ceramic membrane a is between 110~130 L / (m 2 ·h); the critical flux of ceramic ultrafiltration membrane b is between 150~180 L / (m 2 ·h); the critical flux of ceramic membrane c is between 180~200 L / (m 2h). Under this test condition, the critical flux of ceramic membrane c is larger than that of the other two membranes, and its anti-fouling ability is stronger. Table 1 shows the flux decline of the three membranes under different membrane surface flow rates.

[0070] Table 1.

[0071]

[0072] As the membrane surface flow velocity v increases, the membrane flux decline rate of ceramic ultrafiltration membrane a and ceramic ultrafiltration membrane c decreases; the membrane flux of ceramic ultrafiltration membrane b changes irregularly with the increase of v, but the flux decline rate of ceramic ultrafiltration membrane decreases significantly after the membrane surface flow velocity v reaches 1.75 m / s. As the membrane surface flow velocity v increases, the scouring force of the fluid on the ultrafiltration membrane increases, the retention time of pollutants on the membrane surface decreases, the degree of blockage decreases, and the speed of water flowing through the membrane surface increases, resulting in a decrease in the decline in membrane flux. Under the experimental conditions, the decline in the membrane flux J of ceramic ultrafiltration membrane a is between 11% and 20%, the decline in the membrane flux J of ceramic ultrafiltration membrane b is between 6% and 10%, and the decline in the membrane flux J of ceramic ultrafiltration membrane c is between 8% and 12%.

[0073] The effect of transmembrane pressure difference TMP on the flux of ceramic ultrafiltration membrane. The inlet flow rate was controlled at 3 m 3 / h, and other conditions remain unchanged. The transmembrane pressure difference TMP of ceramic ultrafiltration membranes a, b, and c were adjusted to 0.5, 1.0, 1.5, 2.0, and 2.5 MPa, respectively. The flux changes of the three membranes under different transmembrane pressure differences are shown in Table 2 below.

[0074] Table 2

[0075]

[0076] The flux decline rate of the three ceramic ultrafiltration membranes decreases with the increase of the transmembrane pressure difference of the ceramic ultrafiltration membrane. Under the experimental conditions, the flux J of ceramic ultrafiltration membrane a decreases by 15.5~37%, the flux of ceramic ultrafiltration membrane b decreases by 8.9~18.3%, and the flux of ceramic ultrafiltration membrane c decreases by 8.6~12.9%. In terms of flux decline under different transmembrane pressure differences, the decline of ceramic ultrafiltration membrane c is the smallest.

[0077] Based on the above experimental results, ceramic membrane c has the best comprehensive performance. The performance parameters of the screened ceramic membrane c are summarized in Table 3.

[0078] Table 3

[0079] Example 2

[0080] SiC ceramic ultrafiltration membrane was used to treat simulated bilge water with different concentrations. Due to the complex composition of bilge oily wastewater, water was distributed according to the bilge water composition requirements in GB / T4795-2009 "15 ppm Bilge Water Separator" to obtain simulated bilge water in 2.2.2 (2), and the distributed water was further diluted to concentrations of 250, 500, 750, 1000, and 1250 ppm. The simulated water contained characteristic pollutants in bilge water, such as light fuel oil, heavy engine oil, LAS, and Fe3O4.

[0081] Control the water flow rate of ceramic ultrafiltration membrane c to 3 m 3 / h, that is, the membrane surface flow rate is 1.75 m / s, the transmembrane pressure difference TMP is 0.2MPa, and other conditions are controlled unchanged. Since only a part of the oil in the actual influent oil substances is emulsified and dissolved in the water, and a part of the floating oil floats on the surface of the liquid in the water collecting tank and cannot enter the device pipeline, the actual ceramic ultrafiltration membrane influent oil content is much lower than the distribution water concentration. The membrane influent oil content is measured, and the oil content corresponding to the distribution water concentration is approximately 95, 185, 270, 345, and 410 ppm. The fluctuation of the oil content in a small range does not affect the determination and analysis of the test results. The ceramic ultrafiltration membrane c was used to treat simulated bilge water under different distribution water oil substance concentrations. The test results are as follows Figure 4 shown.

[0082] The overall removal rate of ceramic ultrafiltration membrane c is maintained between 96.5% and 98%, and the oil content of produced water is stably maintained between 4 and 11 ppm. It also has good performance in removing emulsified oil. When the concentration of oily substances in water is ≥1250 ppm, that is, the oil content of influent water is ≥410 ppm, the oil content of produced water of ceramic ultrafiltration membrane c is 10.79 ppm, which exceeds the standard requirement of 10 ppm in some countries and regions, and can still meet the widely used 15 ppm standard requirement; when the concentration of oily substances in water is <750 ppm, that is, the oil content of membrane influent water is <275 ppm, the oil content of produced water of ceramic ultrafiltration membrane c is <5 ppm. Under the experimental conditions, the suitable influent oil content of ceramic ultrafiltration membrane c is <400 ppm. Example 3

[0083] Restorative chemical cleaning test. At an inlet flow rate of 3 m 3 / h, TMP=0.2 MPa, SiC ceramic ultrafiltration membrane c continuously circulates to treat simulated bilge oily sewage with 1000 ppm of oily substances. During the treatment process, the flux dropped to 50% of the initial flux and the device stopped running. Summarize the types and combinations of detergents. The test mainly used alkaline detergents, oxidizing detergents, surfactants and other types of agents to perform restorative chemical cleaning tests on the membrane. The backwash pressure was 0.2 MPa, the agent cleaning time was 5 min, and the cleaning methods and combinations were shown in Table 4.

[0084] Table 4

[0085]

[0086] Flux recovery of five cleaning combinations Figure 5 As shown. Figure 5 It can be seen that the ceramic ultrafiltration membrane is cleaned by using different types of cleaning agents and combinations in Table 4. The first four combinations have a certain cleaning effect on the ceramic ultrafiltration membrane. The fifth combination combines the first four methods into one method, and the recovery effect is the best. The corresponding recovery rates FFR of cleaning combinations 1-5 are 63.83%, 75.30%, 80.46%, 67.74%, and 96.25%, respectively.

[0087] Among them, combination 3: gas and water combination + NaClO oxidative cleaning agent has better effect than other single type cleaning agents. In addition to the oxidative property of the cleaning agent, the weak alkalinity plays a major role. It can not only clean the pollutants on the membrane surface, but also remove the pollutants in the membrane pores, so the flux recovery rate is relatively high. Under the conditions of this experiment, the flux recovery cleaning method of the ceramic ultrafiltration membrane can use the cleaning agent combination of "5% NaOH + 0.5% NaClO + 0.2% SDBS" with gas and water combination method for simultaneous backwashing, which has a better flux recovery effect. Example 4

[0088] Backwash cycle test. During the test, the ceramic ultrafiltration membrane c circulated and treated the simulated bilge water with a distribution concentration of 1000 ppm, and the water flow rate of the ceramic ultrafiltration membrane c was controlled to be 3 m 3 / h means the membrane surface velocity is 1.75 m / s, the transmembrane pressure difference TMP is 0.2MPa, and other conditions are kept unchanged. The relationship between the above two functions is obtained as follows Figure 6 shown. Figure 6 The coordinates of the intersection of the two curves are (58.24147.41), corresponding to t = 58.24 min. In the actual test process, the backwashing time and pressure will change, and too short a backwashing cycle will reduce the working efficiency of the membrane. Therefore, the backwashing cycle of the ceramic membrane is set to 60 minutes. Example 5

[0089] Specifically, in the embodiment, the water output of the marine oily wastewater treatment device is 0.25 m 3 / h, the oil content of the inlet water is less than 4000 ppm, and the operating temperature is 5~40 ℃. When the oil content of the bilge water entering the membrane module is ≤400 ppm, the oil content of the produced water is ≤10 ppm; when the oil content of the bilge water entering the membrane module is ≤275 ppm, the oil content of the produced water is ≤5 ppm. The effluent water quality can meet the requirements of GB3552-2018 "Ship Water Pollutant Emission Control Standard", and the oil content is less than 15 ppm. The pollutant type and efficiency table of each treatment unit are shown below.

[0090] Table 5

[0091]

[0092] like Figure 7 As shown, the design of the device not only considers that the effluent meets the discharge standards, but also integrates the various parts of the process. On the basis of ensuring the normal operation of each part of the device and retaining the maintenance space, the space is compressed as much as possible. At the same time, considering the influence of the navigation environment, the device must be stable under certain swaying and tilting conditions, and the sealing between the various components is good. Therefore, the design of the external structural dimensions of this device is length × width × height 1174 mm × 874 mm × 1500 mm.

[0093] During the normal operation of the marine oily wastewater treatment device, ignoring the heat loss, the main energy-consuming parts are the water intake pump, circulation pump, electric control box and air compressor. 3 The total energy consumption for 1 h of operation is 1.645 kW·h, that is, the total energy consumption for processing 1 m 3 The water consumption is 6.58 kW·h.

[0094] The above embodiments are only used to further illustrate a marine oily wastewater treatment device of the present invention, but the present invention is not limited to the embodiments. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for deep treatment of ship oily wastewater, characterized in that: The method comprises: Preliminarily filtering the ship's oily wastewater to remove suspended matter and particulate matter to obtain first oily wastewater; The first oily wastewater is subjected to a coagulation and separation treatment to remove floating oil, dispersed oil and a small portion of emulsified oil in the wastewater, and the oil content in the wastewater is reduced to below 500 ppm, thereby obtaining a second oily wastewater; The second oily wastewater is subjected to cross-flow ultrafiltration deep treatment to intercept emulsified oil and dissolved oil to obtain produced water and concentrated water, and the concentrated water is used as the third oily wastewater; The third oily wastewater is returned to the first oily wastewater, and the produced water is obtained as discharge water after being tested and found to be qualified.

2. The method according to claim 1, characterized in that: The oil content of the ship's oily wastewater is less than 4000 ppm.

3. The method according to claim 1, characterized in that: The preliminary filtration uses a precision filter to reduce the turbidity of the oily wastewater. The precision filters are arranged in series and include at least one precision filter; each of the precision filters is provided with an odd number of filter elements.

4. The method according to claim 1, characterized in that: The coalescence separation treatment includes using an oil-water coalescence separator to remove floating oil, dispersed oil and part of the emulsified oil in the water to ensure that the oil content in the second oil-containing wastewater is reduced to below 500ppm; the oil substances in the oil-water coalescence separator are pumped into the oil storage tank for storage at regular intervals.

5. The method according to claim 1, characterized in that: The cross-flow ultrafiltration deep treatment includes separation by using a ceramic ultrafiltration membrane assembly, wherein at least one group of the ceramic ultrafiltration membrane assembly is provided, and the ultrafiltration membrane assembly further comprises a water inlet, a produced water outlet and a concentrated water outlet, and an odd number of the ceramic ultrafiltration membranes are provided.

6. The method according to claim 5, characterized in that: The ceramic ultrafiltration membrane assembly adopts SiC ceramic ultrafiltration membrane with a filtration accuracy of 40 nm and a pure water flux of 2-3 m 3 / (m 2 ·h), operating transmembrane pressure difference 0.05~0.25 MPa, membrane surface flow rate 1.0~2.0m / s.

7. The method according to claim 1, characterized in that: The produced water is tested by using an oil concentration meter. The produced water with oil content that meets the standard requirements can be discharged, and unqualified produced water will flow back to the ship's oily wastewater collection tank.

8. The method according to claim 1, characterized in that: The ultrafiltration membrane components were cleaned by a combination of 5% NaOH + 0.5% NaClO + 0.2% SDBS and backwashed simultaneously with air and water, and the backwash cycle was set to 60 min.

9. A ship oily wastewater deep treatment device, characterized in that: The invention comprises, in order of water flow direction, a water inlet (1), a water collecting tank (2), a precision filter group (4), an oil-water coalescing separator (6), an ultrafiltration membrane assembly (7) and a water outlet (10); a water inlet pump (3) is provided between the water collecting tank (2) and the precision filter group (4); a circulation pump (5) is provided between the precision filter group (4) and the oil-water coalescing separator (6); the oil-water coalescing separator (6) is provided with an oil storage cabinet (62) for storing filtered substances; a ceramic ultrafiltration membrane (71) for filtering emulsified oil and impurities in water is provided inside the ultrafiltration membrane assembly (7), and a backwash tank (8) for cleaning the ultrafiltration membrane assembly (7) is provided outside; an oil concentration meter (9) is provided between the ultrafiltration membrane assembly (7) and the water outlet (10), and the ultrafiltration membrane assembly (7) is also provided with a reflux pipeline connecting the circulation pump (5) and the water collecting tank (2).

10. The device according to claim 9, characterized in that The inlet and outlet of the water inlet pump (3) are provided with a bypass pipeline directly connected to the water collecting tank (2) and the precision filter group (4).

11. The device according to claim 9, characterized in that The bottom of the oil-water coalescing separator (6) is provided with a drain port (61); the oil storage cabinet (62) is provided with an external drain pipeline and a valve.

12. The device according to claim 9, characterized in that The ultrafiltration membrane assembly (7) further comprises a water inlet (72), a produced water outlet (73) and a concentrated water outlet (74); the produced water outlet (73) is connected to a backwash tank (8), and the concentrated water outlet (74) is connected to a circulation pump (5) and a water collecting tank (2), respectively; the water inlet (72) and the produced water outlet (73) of the ultrafiltration membrane assembly (7) are provided with a bypass pipeline directly connected to the oil-water coalescing separator (6) and the water outlet (10).

13. The device according to claim 9, characterized in that: The backwash tank (8) adopts a chemical washing or air washing method and is provided with a matching chemical adding mechanism or air supply mechanism.

14. The device according to claim 9, characterized in that The device is provided with an automatic operation safety protection module and an alarm module.

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