Biofuel wastewater treatment method

Abstract

The invention discloses a biofuel wastewater treatment method. The method comprises the following steps: sewage enters a mixing tank through a grid; pumping water in the mixing tank into a coagulation air floatation tank, and adding a PAC / PAM coagulant into the coagulation air floatation tank; after a coagulation reaction is carried out in the coagulation air floatation tank, water in the coagulation air floatation tank is pumped into the UASSB reaction tank, and an anaerobic reaction is carried out in the UASSB reaction tank; pumping water in the UASSB reaction tank into a CASS reaction tank, and carrying out an aerobic reaction in the CASS reaction tank; pumping water in the CASS reaction tank into a precision filter tank; and pumping water in the precision filter tank to a disinfection tank. According to the method, secondary pollution to the environment is prevented, emission of pollution factors is reduced, and the regional environment is effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of ecological environmental protection, and in particular to a method for treating biofuel wastewater. Background Art

[0002] In recent years, with people's pursuit of material and spiritual life, more and newer products have been manufactured. Biodiesel is a new type of biomass energy and one of the alternative energy sources with great development potential. Therefore, the large-scale production of biodiesel has become a general trend and an imminent situation.

[0003] At present, biodiesel is mainly produced by chemical methods, using vegetable oil and methanol or ethanol to undergo esterification reaction at 230℃~250℃ with acid or alkaline catalysts to generate corresponding fatty acid methyl ester or ethyl ester biodiesel. That is, it is a clean fuel refined from rapeseed oil. Methanol or ethanol can be recycled in the production process, mainly because it is necessary to deal with unsaturated fatty acids, short-chain alcohols, enzymes with certain toxicity and waste alkali liquid discharge in fat. Economical and effective treatment methods are the focus of research, and improving the reuse rate of water and reducing sewage discharge will be the main research direction in the future.

[0004] Seeking a reasonable method for treating biofuel water, while recycling and resource utilization of wastewater is also a development trend of wastewater treatment, which has a huge market demand, and zero discharge and resource utilization of wastewater has become one of the key development directions of many environmental protection companies. In order to further improve the level of clean production in the fuel industry and reduce the waste of resources such as water and salt, it is necessary to break through the key technologies of fuel impurity removal and resource utilization. At present, the pretreatment impurity removal technology and impurity salt resource treatment technology are mainly involved in zero discharge and recycling of wastewater. Summary of the invention

[0005] In view of the shortcomings existing in the above problems, the present invention provides a method for treating biofuel wastewater.

[0006] To achieve the above object, the present invention provides a biofuel wastewater treatment method, comprising: the wastewater passes through a grid and enters a mixing tank;

[0007] The water in the mixing tank is pumped to a coagulation and flotation tank, and a PAC / PAM coagulant is added to the coagulation and flotation tank;

[0008] After the coagulation reaction in the coagulation flotation tank, the water in the coagulation flotation tank is pumped to the UASSB reaction tank, and an anaerobic reaction is performed in the UASSB reaction tank;

[0009] The water of the UASSB reaction tank is pumped to the CASS reaction tank, and an aerobic reaction is performed in the CASS reaction tank;

[0010] Pumping water from the CASS reaction tank to a precision filter tank;

[0011] The water from the precision filter is pumped to the disinfection tank.

[0012] Preferably, the sludge in the UASSB reaction tank and the scum in the CASS reaction tank are pumped to a thickening tank.

[0013] Preferably, the supernatant of the concentration tank is pumped to the mixing tank.

[0014] Preferably, the pH value in the mixing tank is adjusted.

[0015] Preferably, the operation cycle of the CASS reaction tank includes a water inlet period, an aeration reaction period, a static sedimentation period, a supernatant discharge period and an idle period.

[0016] Preferably, the coagulation flotation tank is stirred simultaneously during aeration.

[0017] Preferably, the disinfection pool uses chlorine dioxide method for disinfection.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention prevents secondary environmental pollution, reduces the emission of polluting factors, effectively improves the regional environment, reduces COD by 5,600 tons / year, reduces organic matter by 9,800 tons / year, reduces total nitrogen by 15.77 tons / year, reduces BOD by 2,300 tons / year, and reduces raw water by more than 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0023] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] The following is combined with Figure 1 The present invention is described in further detail:

[0025] Reference Figure 1 , the present invention provides a method for treating biofuel wastewater, including passing wastewater through a grid into a mixing tank;

[0026] The water from the mixing tank is pumped to the coagulation and flotation tank, and PAC / PAM coagulant is added to the coagulation and flotation tank;

[0027] After the coagulation reaction in the coagulation flotation tank, the water in the coagulation flotation tank is pumped to the UASSB reaction tank, where anaerobic reaction is carried out;

[0028] The water from the UASSB reaction pool is pumped to the CASS reaction pool, where aerobic reaction is carried out;

[0029] Pump the water from the CASS reaction tank to the precision filter tank;

[0030] Pump the water from the precision filter into the disinfection tank.

[0031] In this embodiment, the sewage contains impurities, which are firstly passed through a screen to be intercepted and removed before entering the subsequent treatment process, so as to reduce the load of the subsequent treatment structure.

[0032] Since the amount and quality of sewage discharged are uneven in different time periods, in order to ensure the continuous operation of subsequent equipment, a mixing tank is used to store wastewater and even the water quality, and to adjust the water quality and quantity. Pre-aeration in the coagulation flotation tank is conducive to water homogenization. After oxygenation, the sewage will not produce odor due to lack of oxygen and corruption; at the same time, the stirring effect of aeration can increase the subsequent oil removal and organic matter removal efficiency, ensuring better operation of the subsequent treatment process. In addition, it also serves as a reaction tank to adjust the pH value of sewage, making the pH value close to neutral, further ensuring the normal operation of subsequent treatment facilities. Basic supporting facilities such as maintenance ladders are installed at the end of the regulating tank.

[0033] Adding PAC / PAM coagulant to the incoming water for coagulation reaction will make floating oil and suspended solids form sediment flocs, accelerating their separation from the water body.

[0034] After the sewage fully reacts with the reagent, it enters the high-efficiency flotation stage. The principle of flotation water purification technology is to introduce a large number of small bubbles into the wastewater to the maximum extent possible, and add flocculants or flotation agents when necessary, so that impurities, floccules and other fine suspended matter in the water adhere to each other with the bubbles, forming a floating body with an overall density less than that of water, and then float to the water surface by buoyancy and be removed, realizing solid-liquid separation, thereby achieving the purpose of purifying wastewater, removing oil and excessive precipitation in the water, and ensuring the water discharge effect.

[0035] The UASSB reaction pool removes most of the pollutants in the wastewater, especially COD and BOD in the water. Various microorganisms such as facultative bacteria and anaerobic bacteria in the reactor decompose large molecular organic matter into small molecular organic matter under anaerobic conditions, and generate CH4, CO2 and other gases at the same time. The CH4 content in the gas is about 45% to 60%, which is a highly efficient fuel and can be recycled.

[0036] In the CASS reaction tank, an anoxic and aerobic environment is created, and the activated sludge that grows in large quantities in the biological reaction tank is used to degrade pollutants in the water to achieve the purpose of purifying the water quality. Usually, an operation cycle has five independent stages, namely water inlet, aeration reaction, static sedimentation, supernatant discharge and idle (including residual sludge discharge). Water level control is used for water inlet and discharge, and time control is used for reaction and sedimentation.

[0037] The effluent of CASS reaction tank generally contains tiny suspended matter. These substances that are forcibly solidified by mechanical action may dissolve again and cause the suspended matter in the effluent to exceed the standard. Multi-media filtration after SBR tank can effectively remove tiny suspended matter. Filter the wastewater before it is discharged, and use natural quartz sand and anthracite filter media to ensure that the effluent water quality meets the standard. The process principle is to fill a certain amount of granular filter media with smaller particle size in the filter tank. When the sewage flows through, the filter media uses the interception ability of the floc to quickly purify the sewage; after running for a certain period of time, due to the increase in head loss, the filter tank needs to be backwashed to release the intercepted suspended matter, which is the backwashing process. Here, a complete set of fully automatic filters is selected. The backwashing process of the equipment is fully automatic, and there is no backwashing pump or water tower outside the body. Save water and electricity, and operate reliably.

[0038] Disinfection treatment can remove most pathogenic bacteria such as Escherichia coli and fecal streptococci in water. There are many ways to disinfect, such as liquid chlorine method, ozone method, sodium hypochlorite method, chlorine dioxide method, etc. Although the sodium hypochlorite method has the advantages of convenient dosing, low price and high reliability, it will combine with certain organic matter in the water to form organic halides with carcinogenic effects. Chlorine dioxide is recognized as the best disinfectant with good bactericidal effect and is an ideal substitute for sodium hypochlorite. This system uses chlorine dioxide for disinfection. The effluent from the disinfection pool is discharged or reused after passing through the pipeline. An electromagnetic flowmeter is installed in the outlet pipe section to monitor the amount of treated water.

[0039] The sludge thickening tank is used to store a certain amount of sludge, which is concentrated by gravity. The concentrated sludge is eventually transported out by tank trucks regularly for further drying or composting. It can also be mixed with coal sludge and burned as a final treatment method.

[0040] In order to improve the management level, reduce the labor intensity of personnel, strengthen the rational operation of each production link, ensure the quality of sewage treatment and production safety, save energy consumption, and reduce production costs, automation is used to control the sewage treatment process. The sewage treatment plant is equipped with automated monitoring equipment according to the requirements of each process treatment and controlled in the central control room.

[0041] Treatment bacteria are specially cultivated according to the types of sewage pollutants, and have special ability to degrade sewage, such as common nitrifying bacteria to remove organic matter, denitrifying bacteria to treat nitrogen, etc. Bacteria rely on metabolism to decompose organic matter in wastewater, so it takes a certain amount of time for the wastewater and bacteria to be fully mixed to achieve the desired effect. The reaction time is longer than that of chemical treatment, but the bacteria treatment effect is significant, the cost is low, and no special person is required to supervise during operation, so it can be widely used.

[0042] In this embodiment, the aerated activated sludge process, the jet aerated activated sludge process, the biological rotating disc, etc. are also used, and the biological fluidized bed is still in the experimental application stage. However, since the biological removal rate of chromaticity is not high, generally around 75%, when the chromaticity requirement of the effluent is high, physical or chemical treatment is required.

[0043] Aerobic biological treatment has obvious effect on BOD removal, generally reaching about 95%, but the chromaticity and COD removal rates are not high. In particular, the widespread application of surfactants, solvents and reduction technologies has not only increased the COD of fuel wastewater to 5000-6000 mg / L, but also reduced the BOD / COD from the original 0.3-0.4 to below 0.15. Simple aerobic biological treatment is becoming more and more difficult, and the effluent is difficult to meet the standards. In addition, the problem of residual sludge treatment or disposal of aerobic methods has always been a difficult problem that has not been solved in the field of wastewater treatment.

[0044] In order to explore new technologies for the treatment of fuel wastewater with high efficiency, low consumption and low investment, a large number of experimental studies have been conducted in recent years on the combination of CASS and UASSB, and great success has been achieved. This process flow is mainly aimed at some high-molecular substances with poor biodegradability in fuel wastewater, hoping that they will be hydrolyzed and acidified in the anaerobic section to become smaller molecules, thereby improving the biodegradability of the wastewater and creating conditions for aerobic treatment. Therefore, the anoxic section in the anoxic system has a dual role: one is to pretreat the wastewater, improve its biodegradability, and adsorb and degrade some organic matter; the other is to digest the residual sludge in the system.

[0045] After the sewage is denitrified by oxygen, it is passed through the CASS process, and some microorganisms grow in suspension in the water without carriers. Therefore, it has the characteristics of both the activated sludge method and the biological filter. According to the characteristics of fuel wastewater, when I design the UASSB process, I often design pre-sedimentation tanks in the middle and rear sections of the tank body. One is to reduce the total nitrogen concentration in the effluent to ensure the treatment effect of the subsequent sedimentation tank; the other is to return the precipitated sludge to the anaerobic tank to ensure a certain sludge concentration in the tank and a higher removal rate.

[0046] The beneficial effects of this method include:

[0047] Economic benefits: Prevent secondary environmental pollution, maintain water quality safety in the North China Industrial Park and other industrial parks, and ensure people's environmental safety.

[0048] Social benefits: The emission of pollution factors is reduced, the regional environment is effectively improved, and the environmental quality of water, air and soil in the North China Park is further guaranteed.

[0049] Ecological benefit indicators: COD reduction of 5,600 tons / year, organic matter reduction of 9,800 tons / year, total nitrogen reduction of 15.77 tons / year, BOD reduction of 2,300 tons / year, and raw water reduction rate of more than 90%.

[0050] Sustainable impact indicators: After the implementation of the project, the environmental quality has been effectively improved, and the happiness index of local residents has been effectively improved. The environmental impact on the industrial park is relatively small, and it has a positive significance for ecological restoration.

[0051] Based on the principle of advanced technology, simple management, mature technology, reliable and reliable, low infrastructure investment, low operating cost and low treatment cost, and the advantages of localization of equipment and spare parts, small footprint, high degree of automation and small number of personnel, combined with the characteristics of large changes in sewage volume and water quality, high requirements for effluent water quality and underground structures, we selected the biochemical process as the main process of the sewage treatment plant. In addition, the biochemical treatment adopts our patented technology, high-efficiency flotation equipment, and combines multiple sedimentation tanks to ensure that various indicators such as effluent color meet the standards.

[0052] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for treating biofuel wastewater, characterized in that: include: Sewage passes through the screen and enters the mixing tank; The water in the mixing tank is pumped to a coagulation and flotation tank, and a PAC / PAM coagulant is added to the coagulation and flotation tank; After the coagulation reaction in the coagulation flotation tank, the water in the coagulation flotation tank is pumped to the UASSB reaction tank, and an anaerobic reaction is performed in the UASSB reaction tank; The water of the UASSB reaction tank is pumped to the CASS reaction tank, and an aerobic reaction is performed in the CASS reaction tank; Pumping water from the CASS reaction tank to a precision filter tank; The water from the precision filter is pumped to the disinfection tank.

2. The biofuel wastewater treatment method according to claim 1, characterized in that: The sludge in the UASSB reaction tank and the scum in the CASS reaction tank are pumped to a thickening tank.

3. The biofuel wastewater treatment method according to claim 2, characterized in that: The supernatant of the concentration tank is pumped to the mixing tank.

4. The biofuel wastewater treatment method according to claim 3, characterized in that: The pH value in the mixing tank is adjusted.

5. The biofuel wastewater treatment method according to claim 4, characterized in that: The operation cycle of the CASS reaction tank includes a water inlet period, an aeration reaction period, a static sedimentation period, a supernatant discharge period and an idle period.

6. The biofuel wastewater treatment method according to claim 5, characterized in that: The coagulation flotation tank is stirred simultaneously during aeration.

7. The biofuel wastewater treatment method according to claim 6, characterized in that: The disinfection pool adopts chlorine dioxide method for disinfection.

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