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Service > Emulsion wastewater treatment technology

Emulsion wastewater treatment technology

Emulsion is widely used in machining, automotive engine machining, steel rolling Kun and cooling and lubrication [1]. Emulsion that is in the process of recycling metal dust and the surrounding environment influence the media, deteriorate, and must be replaced regularly. Replacement of the chemical properties of water emulsion is very stable, to deal with great difficulty. The author of the emulsion wastewater treatment technologies were reviewed in order to provide a reference for emulsion wastewater treatment.
Features 1 emulsion wastewater
1.1 to form an emulsion of
Emulsion added a number of surfactants reduce surface free energy of the system, and the surfactant molecules in the oil - water interface and the formation of interfacial film directed adsorption, preventing collision between droplets becomes large, so that oil droplets can long-term stability to the presence of water [2, 3, 4]. Therefore, it must destroy the emulsion wastewater handling stability, try to eliminate or weaken the ability of surfactant-stabilized emulsion to achieve oil-water separator.
1.2 emulsion wastewater characteristics
Water emulsion as an intractable industrial wastewater, chemical stability and high pollution load. Relevant information, waste oil emulsion mass concentrations up to 15 000 ~ 20 000 mg / L, COD of 18 000 ~ 35 000 mg / L, BOD up to 5 000 ~ 10 000 mg / L. To improve the performance of the emulsion, but also adding a lot of additives, such as oil additives, extreme pressure additives, anti-corrosion additives, anti-mildew additives, anti-foam additives, etc. [5], so that the emulsion composition is extremely complex, difficult process.
2 emulsion wastewater treatment technology
Currently emulsion wastewater treatment mainly uses chemical coagulation, co-coagulation flotation method, electro-coagulation method, advanced oxidation, ultrafiltration, biochemistry combined process, which co-coagulation flotation method, electro-coagulation method is the basis of the chemical coagulation the developed, advanced oxidation, ultrafiltration water treatment rule separately using advanced oxidation and membrane technology, biochemical composition process is a combination of the above methods developed on the basis of biological treatment, now on their emulsion Wastewater Treatment The application status were introduced.
2.1 Chemical Coagulation
Chemical coagulation method is the traditional method for processing waste water emulsion, namely water emulsion in dosing chemical coagulants, on the one hand the hydrolysis reaction of colloids adsorb oil beads, on the other hand a macromolecular polymerization occurs in varying degrees of polymerization purified by adsorption and flocculation, bridging the removal of oil droplets, to breaking the purpose of achieving the separation of oil and water [3, 6].
Early in the chemical coagulation process waste water emulsion, the commonly used inorganic coagulant, such as ferric sulfate, aluminum sulfate, etc., but because of the traditional inorganic coagulant effect is not ideal, in recent years there have been many inorganic polymer coagulation Application and Research Agent. Wu Keming, etc. [7] water glass and sulfuric acid is made of poly silicon compound aluminum sulfate coagulant, turbidity is 10 910 NTU, the oil is 3 446 mg / L, COD of 21 006 mg / L of high concentrations of emulsifying Liquid waste water treatment, appropriate removal rates were 99.9%, 99.7%, 99.5%. ZHANG Jian-peng, etc. [8] using a composite polymer emulsion wastewater ferric coagulant treatment, not only to obtain good breaking effect, CODCr average removal of oil and 90%, respectively, more than 99%, and the water has a high coagulation biodegradability. Yong and other [9] will increase the pickling liquid waste as raw material prepared PAC (PAC) applies to secondary cold rolling emulsion waste treatment, COD removal rate could reach above 95%, to achieve the purpose of waste to treat waste .
In addition, organic coagulants in emulsion wastewater treatment there are certain applications. Lee Jung to wait [10] use of organic demulsifier SYS and PAC joint breaking of a steel company for oil concentration 6 200 mg / L, COD processing of 34 000 mg / L of cold-water emulsion, di stage breaking oil removal rate of 99.58%, COD removal rate was 97.79%, and achieved very good results.
2.2-coagulation flotation method
Coagulated flotation method is based on the chemical coagulation, flotation technology combined with a way to produce. Because after chemical coagulation resulting large particle droplets and micro-bubbles floc flotation machine with particulate matter produced by the collision of adhesion, the formation of larger particle size with gas floe, so its removal is more significant than the coagulating sedimentation method , water pH, temperature, pollutants load adaptable, less dosage, shorter reaction time [11, 12].
Currently flotation of coagulated emulsion wastewater treatment study abroad a little bit more in detail. AI Zouboulis, etc. [13] using a co-coagulation and air flotation process simulation emulsion wastewater containing n-octane. The results showed that the main factors of the method include flocculant dosage, initial pH, chemical additives (such as demulsifiers) concentration, flotation scavenger concentration and recycle ratio. The initial concentration of oil processing at the Best Conditions 500 mg / L of simulated waste water emulsion, 95% of emulsified oil was isolated. After K. Bensadok, etc. [14] found that in the conventional emulsion breaking method COD removal efficiency is not high, the joint use of dissolved air flotation method of COD reduction of 29% compared with the original process, turbidity reduction of 71%.
Domestic research on co-coagulation flotation emulsion wastewater treatment also achieve better results.曹福, etc. [15] using ferric chloride (PAFC) for the emulsion co-coagulation flotation wastewater treatment, when PAFC is 1 g / L, the turbidity removal rate of 98%. Xu Chi et al. [12] by co-coagulation flotation emulsion breaking adsorption treatment of wastewater, based dosing PAC, PAM, based on the adsorption capacity of a certain sewage treatment plant sludge in wastewater investment and added to the emulsion, found the sludge dosage of 15 g / L, with the best treatment effect of COD, 5 000 ~ 20 800 mg of COD can be treated before / L 75 mg lowered treated / L, up to the national sewage treatment effect Integrated emission standard.
2.3 electro-coagulation method
Electro-coagulation method with soluble metal as an electrode, the electric field in the metal loses electrons is oxidized to form hydroxide gel, the use of adsorption and coagulation effect and electrolytic oxidation-reduction reaction of the process to achieve the removal of oil pollution. Since this method can greatly reduce the amount of coagulation agent and the processing effect is good, very promising [16]. Typically different electrode materials, electro-coagulation mechanisms are different. Metal as an anode, a cathode inert material, the electrolysis process will produce metal colloids, reducing the performance of the role of electrode reaction bleaching, electrochemical reaction, coagulation, adsorption and so on in their research materials mainly iron and coke. Chen Yilan, etc. [17] use a rotary electric coagulation breaking technical processing metalworking emulsion, oil, COD removal rate was 59.9%, more than 28.5%, and to lead to the raw water B / C increased from 0.21 to 0.32.
Metal as yin, the male electrode, usually added NaCl, the electrode reaction produces a metal colloid, a strong oxidizing agent chlorine and hypochlorite, can play a role in coagulation, adsorption, flotation function and role of oxidation and reduction. P. Ca horns izares etc. [18] In the aluminum electrode at the plate spacing 9 mm, a current density of 1.01 × 10-2 A / cm2 treatment emulsion by electric coagulation method, and with dosing AlCl3 or Al2 comparison (SO4) chemical coagulation method 3. Experimental results show that the effect of the dose of the two methods has nothing to do with the concentration of aluminum ions in water and the pH is related to under optimum pH 5 ~ 9, high COD removal efficiency. Wu Keming, etc. [19] to the aluminum electrode, in order to prevent passivation using timed inverted pole and adding NaCl emulsion wastewater treatment, the use of chlorine and hypochlorite oxidizing emulsion waste water produced by the reaction of organic compounds produced by electrolytic process aluminum and aluminum hydroxide complex ions of organic matter and suspended solids removal. The results show that the method of turbidity, oil, COD removal rate is very high, reaching 99.1%, 98.6% and 99.3%.
Some researchers of electro-coagulation method design parameters are discussed. For the external power supply form, studies have shown that the coagulation effect is better than AC current, and frequency control higher at 60 Hz economic suitability [20].周连成, etc. [21] pointed out that the plate spacing is too large, the current density is too big, too long and is the cause of electrolysis electrolysis breaking failure, and proposed plate spacing 8 ~ 15 mm, a current density of 0.004 ~ 0.006 A / cm2, electrolysis time 40 ~ 50 min of optimal operating conditions. Caofu, etc. [22] to the aluminum electrode and adding NaCl rolling emulsion wastewater treatment, the test pH = 6, the current density is 0.004A / cm2, time is 40 min, NaCl was 1.25 g / L, plate spacing When 1 cm, COD removal efficiency of 99.5%, and achieved good treatment effect.
2.4 Advanced Oxidation
Using advanced oxidation process is based on emulsion wastewater strong oxidation of · OH, research in this area to the main Fenton oxidation. ACSC Teixeira, etc. [23] using the Fenton and Fenton Process for emulsion wastewater containing different concentrations PDMAS (an amino silicone polymer) are processed, by COD, nitrate, iron and ferrous ion analysis indicates PDMAS be removed in the oxidation process, mainly due to an emulsion of a surfactant is degraded, so that PAMAS further gather and role of · OH. MA Tony [24] and other studies also show that Fenton Process for emulsifying oily wastewater treatment have a good effect, not only can effectively remove COD, oil, also significantly improve the water quality of emulsified wastewater. To reduce the amount of Fenton oxidation of ferrous, 唐文伟 etc. [25] use to replace some or all of the air H2O2 wet hydrogen peroxide oxidation emulsion wastewater treatment process, significantly reducing the dosage of ferrous, 150 ℃, water COD 50 540 mg / L, the removal rate of 82.4%. Li Cheng [26] combined with micro electrolysis and Fenton emulsion wastewater treatment, COD removal under optimal operating conditions of up to 97.16%.
2.5 Ultrafiltration
Ultrafiltration emulsion wastewater treatment is the use of significantly different molecular size of water, take a cross-flow filtration of water filter, water molecules smaller than the pore and through an ultrafiltration membrane, the oil molecules larger than the pore impermeable membrane, thereby realization of oil-water separation. For emulsion wastewater treatment, early ultrafiltration using an organic film, but because of the high cost of organic film, not high temperature, low mechanical strength, easy hydrolysis, so to ceramic membrane is an inorganic membrane representative quickly occupied the market [ 27]. When the emulsion wastewater treatment, ultrafiltration system operation stability of the emulsion change adaptation, operations management and processing costs were better than oxidation [28], and therefore be more widely used in emulsion wastewater treatment. To solve the rapid decline in membrane flux and membrane ultrafiltration membrane easy to pollution problems exist, Zhao et al. [29] studied the influence of the operating parameters of the ultrafiltration system. By controlling the operating temperature of (60 ± 5) ℃, pH of 9 to 11, as well as caustic in each operating cycle, run cycle every three pickling operation, has achieved the desired results. P. Janknecht, etc. [30] compared 14 different pore size of the ultrafiltration membrane and microfiltration membrane treatment effect of cutting emulsion industrial wastewater, and finally through testing to determine the appropriate cutting emulsion wastewater treatment filters.
Currently Ultrafiltration studies focus on the use of the combination process. Shu Li et al. [31] The ultrasonic technology for ultrafiltration emulsion wastewater treatment, not only greatly improve the pollutant removal efficiency, but also improve membrane flux, reduce membrane fouling. IS Chang et al. [32] then the UF and Advanced Oxidation an automobile parts factory emulsion wastewater, ultrafiltration not penetrate the oil can be reused, the penetration of liquid through ozone oxidation treatment can be used as reuse water.
2.6 Biochemical Technology
Breaking operation can be destabilizing an emulsion of surfactant to achieve water separation, but emulsion COD after treatment remained at a high level, to be further processed to discharge or reuse. By eliminating oils, water emulsion breaking after a certain biodegradability, making biological treatment possible. Written, etc. [33] for breaking through calcium chloride and alum, PAC and PAM coagulation treatment of effluent treatment, using hydrolysis - aerobic - activated carbon adsorption effluent COD can reach 50 ~ 70 mg / L, SS is 75 mg / L, petroleum was 5.4 mg / L, chroma 5 times. Fleming et al. [34] using membrane filtration breaking + + biochemical + Fenton oxidation process for high concentration of emulsified oil wastewater treatment, COD from 3 × 104 ~ 2 × 106 mg / L decreased to 50 mg / L or less, the process works well . Zhu Jing et al. [35] using flotation -SBR- filtration process emulsion wastewater, COD, BOD, oil from the 22 400,2 680,1 420 mg / L down 137,25,0.8 mg / L, the removal of rate of 99.38%, 99.06%, 99.94% respectively.
3 Prospects
(1) chemical coagulation, co-coagulation flotation method, electro-coagulation method, advanced oxidation, ultrafiltration can be used as an effective oil emulsion breaking process wastewater. Coagulated flotation method and electro-coagulation method than conventional coagulation process has better treatment effect, with advanced oxidation and ultrafiltration as the focus of the study should be used as an emulsion process. (2) current actual project using more electricity condensation law, which is due to the method can greatly reduce the use of chemical coagulants, so this method research focus to further optimize operating parameters of the electrodes should be placed conditions on. Oil-water separation (3) is not as advanced oxidation method or ultrafiltration coagulation, and therefore should be used as a means of physico-chemical treatment after breaking to further reduce COD, improve biodegradability. Because ultrafiltration membrane pore size directly affects the molecule permeability, so the research should focus on dealing with different kinds of super emulsion membrane pore size choice. (4) may be considered the combination of two or more processes, linking emulsion for wastewater treatment, in order to achieve a mutually reinforcing effect. As the ultrasonic techniques for emulsion wastewater treatment ultrafiltration not only improve pollutant removal efficiency, but also improve membrane flux, reduce membrane fouling; ultrafiltration using advanced oxidation effluent treatment, water quality can be further improved; If After biological process as a process, there will be more economical. Thus, the combination process is a combination of special biochemical process technology for processing will become a hot emulsion wastewater treatment research.

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