On the ultrafiltration membrane technology in environmental engineering water treatment

Paper Keywords: super water treatment applications of membrane technology Environmental Engineering

Abstract: This paper first discusses the basic principles and characteristics of the ultrafiltration membrane technology, and then from the five aspects of ultrafiltration membrane technology in water treatment applications, for reference.

1 Introduction
Ultrafiltration membrane technology is a solution purification, separation or concentration of the film through the separation technique, the range between the microfiltration and nanofiltration. Ultrafiltration membrane is an effective barrier of the suspended particles and colloidal substances, the ultrafiltration membrane at the same time can also be achieved an effective removal of the two insects, algae, bacteria, viruses, and aquatic organisms, so as to achieve the purification of the solution, and the purpose of separation and concentration. compared with conventional processes, membrane technology with low energy consumption in water treatment low, low operating pressure, high separation efficiency advantage of flux and recyclable useful substances widely used in drinking water purification, recycling of sewage, wastewater, pulp wastewater, desalination water treatment in this paper ultrafiltration membrane technology in environmental engineering water treatment commence a brief summary, for reference.

Basic principles and characteristics of ultrafiltration membrane technology

2.1 ultra basic principles of membrane technology

Ultrafiltration (Ultra Filtration, referred to as UF) is the solution is under pressure, solvent and part of the low molecular weight solutes pass through the membrane pores to reach the other side of the membrane, while the the polymer solutes or other emulsified micelles group trapped, from the purpose of separation in the solution. the rejection mechanism is sieving effect, but sometimes of the chemical characteristics of the film surface (of the electrostatic effect of the film also plays an interception ultrafiltration separation is after a certain pressure is applied to the feed solution, the polymeric substance membrane surface and microporous adsorption, colloidal substances, the hole is blocked interception and membrane surface mechanical sieving effect in three ways ultrafiltration membrane to prevent water, inorganic salts and low molecular weight substances through film .

The domain of definition of the molecular weight cutoff of the ultrafiltration membrane technology 500-500000 or so, corresponding to the aperture is about 0.002-0.1μm, the static pressure differential operation is generally 0.1-0.5Mpa, is the diameter of the separation component of about 0.005-10μm.

2.2 ultrafiltration membrane technology features

1 high efficiency removal of impurities, the quality of water is much better than the traditional method.

2. Completely eliminate or greatly reduce the use of chemical agents to avoid secondary pollution.

System is easy to automation, and high reliability. Easy operation facilities only open, close the two tranches.

4. Has good chemical stability, acid, alkali hydrolysis performance, can be widely used in various fields.

Heatproof temperature can reach 140 ℃, can be ultra-high-temperature steam and ethylene oxide sterilization, can be used in a wide pH range, and can be used in acid and alkali, and a variety of organic solvent under conditions.

6 high filtration precision, can effectively filter out 99.99% of the water colloids, bacteria, suspended solids and other harmful substances.

Conventional water treatment system costs quite sewage ultrafiltration process water quality and reuse industrial wastewater, the general technology not standard, full wastewater treatment using ultrafiltration technology.

3 ultrafiltration membrane technology in water treatment

3.1 Drinking Water Purification

With the increasingly serious water pollution problems in China, China experienced water quality problems, such as Giardia and Cryptosporidium (two insects, daphnia and bloodworm, the algae increased pollution and odor and algal toxins microorganisms, water, biological stability problems. ultra membrane technology used in the purification of drinking water, which may remove the water including the daphnia, algae, protozoa, bacteria, and even viruses, water have better treatment effect of disease microorganisms, turbidity, natural organic matter, trace organic pollutants, ammonia, etc., to meet the water quality requirements.

Such as, Zhang Yan et al [2] coagulation and sedimentation pretreatment method, submerged ultrafiltration membrane treating Dongjiang run in a pilot study, the process by pathogenic micro-organisms on the water, turbidity, natural organic matter, toxic the harmful trace organic pollutants, ammonia, heavy metals and other multi-level barrier, its content has been progressively cut the last to get high-quality drinking water.

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3.2 papermaking wastewater treatment

Ultrafiltration membrane technology used in papermaking wastewater, mainly concentrated in certain ingredients and recycled through the water and return to the process used. General, the papermaking wastewater membrane separation technology research include: recycling by-products, the development of comprehensive utilization of lignin, the pulping liquor preconcentration, removal of toxic substances in the bleaching effluent.

Yang Youjiang [3] ultrafiltration processing paper sulfonated chemical mechanical pulp (SCMP ultrafiltration wastewater and the impact of various factors, the results showed that: MWCO for a 20000u the polyethersulfone (PES200 film is suitable for processing SCMP wastewater, and cleaning 98% after membrane flux recoverable. Huang Lijiang [4] 0.8μm microfiltration (MF, with 50nm ultrafiltration (UF inorganic ceramic membrane combined process of papermaking wastewater treatment at a temperature of 15 ° C and a pressure of 0.1 MPa operating conditions, the 0.8 μm membrane COD removal efficiency of 30% to 45% of the 50 nm film of COD removal efficiency of 55% to 70%.

3.3 treatment of oily wastewater

Oily wastewater existing state divided into three types: floating oil, dispersed oil, emulsified oil, the first two are easier to handle, can be mechanically separated, condensed precipitation, activated carbon adsorption technology processing, oil dropped to very low. Emulsified oil containing the organic surfactant and play the same role, the oil to the micron size of the ion present in the water are more difficult, gravity separation and coarse method while the use of membrane technology, it makes the water and low molecular weight organic compounds through the membrane, degreasing and removal of COD and BOD, in order to achieve the oil-water separator.

Oily wastewater is usually oil 100 ~ 1000mg / L, more than the national emission standards (<10mg / L, so advanced and efficient balanced pressure Air Flotation technology and hollow fiber membrane separation technology for the separation before discharge operating pressure of 0.1MPa, sewage temperature of 40 ℃, the membrane permeable speed of up to 60 ~ 120L / (m2 · h), the oil content in the water for traces of the average of the suspended solids content of 32mg / L suspended matter particle size in the average value of 0. 82μm, to fully achieve the ultra-low permeability oil field water injection water quality standards.

3.4 urban sewage reuse

Urban sewage is an important water resources, countries have already begun extensive English film urban wastewater reuse, with the problem of water pollution in China's increasingly serious, ultra-filtration membrane technology used in urban wastewater reuse has become aroused attention. soup where sensitive [5] CASS ultrafiltration membrane Combined Process residential sewage, hydraulic retention time of 12h of CODCr concentration between 215 ~ 677 mg / L, the process water the CODCr stable in about 30 mg / L, NH3-N concentration of 22.2 ~ 41.2 mg / L, the effluent NH3-N as low as 0. 2 mg / L, the removal rate of more than 90% of the effluent pH value of between 7.26 to 7.89 effluent turbidity of less than 0.5, the water quality is better than reuse water standards, direct reuse.

3.5 Desalination

Desalination technology after half a century of development, the technically more mature, the current major desalination reverse osmosis (SWRO, multi-stage flash (MSF, multi-effect evaporator (MED and pressure steam distillation (VC, etc., while the suitable for large-scale desalination method only SWRO, MSF and MED With the continuous development of membrane technology, from the 19 World beginning of the 1960s film technology began to be used desalination but in the process, due to the problem of membrane fouling, making The reverse osmosis system bottlenecks in the processing of seawater, application of ultrafiltration membrane technology, can effectively control the sea water quality to deliver quality water for the reverse osmosis system.

Such as, Yechun Song et al [6] using hollow fiber ultrafiltration membranes to deal directly with the high turbidity water, product water turbidity average of the ultrafiltration membrane 0 11NTU Silt Density Index average of 2.4, the average removal of COD rate of 60.0%, the average removal rate of 89.0% for the glue silicon, transmembrane pressure less than 6.0 × 104Pa, far less than the ultrafiltration membrane the maximum operating pressure of 1 × 105Pa, the ultrafiltration membrane of high turbidity, large changes in the sea water is highly adaptive, in the case of high turbidity seawater for water as a pretreatment device for seawater reverse osmosis system.


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