污水处理工业废水回用中英文对照外文翻译文献.docx

1、污水处理工业废水回用中英文对照外文翻译文献Catalytic strategies for industrial water re-useAbstractThe use of catalytic processesi n pollution abatement and resource recovery is widespread and of significant economic importance R.J. Farrauto, C.H. Bartholomew, Fundamentals of Industrial Catalytic Processes, Blackie Acade

2、mic and Professional,1997. For water recovery and re-use chemo-catalysis is only just starting to make an impact although bio-catalysis is well established J.N. Horan, BiologicalWastewater Treatment Systems; Theory and Operation, Chichester, Wiley, 1990. This paper will discuss some of the principle

3、s behind developing chemo-catalytic processes for water re-use. Within this context oxidative catalytic chemistry has many opportunities to underpin the development of successful processes and many emerging technologies based on this chemistry can be considered .Keywords: COD removal; Catalytic oxid

4、ation; Industrial water treatment 1.IntroductionIndustrial water re-use in Europe has not yet started on the large scale. However, with potential long term changes in European weather and the need for more water abstraction from boreholes and rivers, the availability of water at low prices will beco

5、me increasingly rare. As water prices rise there will come a point when technologies that exist now (or are being developed) will make water recycle and re-use a viable commercial operation. As that future approaches, it is worth stating the most important fact about wastewater improvement avoid it

6、completely if at all possible! It is best to consider water not as a naturally available cheap solvent but rather, difficult to purify, easily contaminated material that if allowed into the environment will permeate all parts of the biosphere. A pollutant is just a material in the wrong place and th

7、erefore design your process to keep the material where it should be contained and safe. Avoidance and then minimisation are the two first steps in looking at any pollutant removal problem. Of course avoidance may not be an option on an existing plant where any changes may have large consequences for

8、 plant items if major flowsheet revision were required. Also avoidance may mean simply transferring the issue from the aqueous phase to the gas phase. There are advantages and disadvantagest o both water and gas pollutant abatement. However, it must be remembered that gas phase organic pollutant rem

9、oval (VOC combustion etc.,) is much more advanced than the equivalent water COD removal and therefore worth consideration 1. Because these aspects cannot be over-emphasised， a third step would be to visit the first two steps again. Clean-up is expensive, recycle and re-use even if you have a cost ef

10、fective process is still more capital equipment that will lower your return on assets and make the process less financially attractive. At present the best technology for water recycle is membrane based. This is the only technology that will produce a sufficiently clean permeate for chemical process

11、 use. However, the technology cannot be used in isolation and in many (all) cases will require filtration upstream and a technique for handling the downstream retentate containing the pollutants. Thus, hybrid technologies are required that together can handle the all aspects of the water improvement

12、 process6,7,8.Hence the general rules for wastewater improvement are:1.Avoid if possible, consider all possible ways to minimise.2.Keep contaminated streams separate.3.Treat each stream at source for maximum concentration and minimum flow.4.Measure and identify contaminants over complete process cyc

13、le. Look for peaks, which will prove costly to manage and attempt to run the process as close to typical values as possible. This paper will consider the industries that are affected by wastewater issuesa nd the technologies that are available to dispose of the retentate which will contain the pollu

14、tants from the wastewater effluent. The paper will describe some of the problems to be overcome and how the technologies solve these problems to varying degrees. It will also discuss how the cost driver should influence developers of future technologies.2.The industriesThe process industries that ha

15、ve a significant wastewater effluent are shown in Fig. 1. These process industries can be involved in wastewater treatment in many areas and some illustrations of this are outlined below.Fig. 1. Process industries with wastewater issues.2.1.RefineriesThe process of bringing oil to the refinery will

16、often produce contaminated water. Oil pipelines from offshore rigs are cleaned with water; oil ships ballast with water and the result can be significant water improvement issues.2.2.ChemicalsThe synthesis of intermediate and speciality chemicals often involve the use of a water wash step to remove

17、impurities or wash out residual flammable solvents before drying.2.3.PetrochemicalsEthylene plants need to remove acid gases (CO2, H2S) formed in the manufacture process. This situation can be exacerbated by the need to add sulphur compounds before the pyrolysis stage to improve the process selectiv

18、ity. Caustic scrubbing is the usual method and this produces a significant water effluent disposal problem.2.4.Pharmaceuticals and agrochemicalsThese industries can have water wash steps in synthesis but in addition they are often formulated with water-based surfactants or wetting agents.2.5.Foods a

19、nd beveragesClearly use water in processing and COD and BOD issues will be the end result.2.6.Pulp and paperThis industry uses very large quantities of water for processing aqueous peroxide and enzymes for bleaching in addition to the standard Kraft type processing of the pulp. It is important to re

20、alise how much human society contributes to contaminated water and an investigation of the flow rates through municipal treatment plants soon shows the significance of non-process industry derived wastewater.3.The technologiesThe technologies for recalcitrant COD and toxic pollutants in aqueous effl

21、uent are shown in Fig. 2. These examples of technologies 2,6,8 available or in development can be categorised according to the general principle underlying the mechanism of action. If in addition the adsorption (absorption) processes are ignored for this catalysis discussion then the categories are:

22、1.Biocatalysis2.Air/oxygen based catalytic (or non-catalytic).3.Chemical oxidation1.Without catalysis using chemical oxidants2.With catalysis using either the generation of _OH or active oxygen transfer. Biocatalysis is an excellent technology for Municipal wastewater treatment providing a very cost

23、-effective route for the removal of organics from water. It is capable of much development via the use of different types of bacteria to increase the overall flexibility of the technology. One issue remains what to do with all the activated sludge even after mass reduction by de-watering. The quanti

24、ties involved mean that this is not an easy problem to solve and re-use as a fertilizer can only use so much. The sludge can be toxic via absorption of heavy metals, recalcitrant toxic COD. In this case incineration and safe disposal of the ash to acceptable landfill may be required. Air based oxida

25、tion 6,7 is very attractive because providing purer grades of oxygen are not required if the oxidant is free. Unfortunately, it is only slightly soluble in water, rather unreactive at low temperatures and, therefore, needs heat and pressure to deliver reasonable rates of reaction. These plants becom

26、e capital intensive as pressures (from _10 to 100 bar) are used. Therefore, although the running costs maybe low the initial capital outlay on the plant has a very significant effect on the costs of the process. Catalysis improves the rates of reaction and hence lowers the temperature and pressure b

27、ut is not able to avoid them and hence does not offer a complete solution. The catalysts used are generally Group VIII metals such as cobalt or copper. The leaching of these metals into the aqueous phase is a difficulty that inhibits the general use of heterogeneous catalysts 7. Chemical oxidation w

28、ith cheap oxidants has been well practised on integrated chemical plants. The usual example is waste sodium hypochlorite generated in chlor-alkali units that can be utilised to oxidise COD streams from other plants within the complex. Hydrogen peroxide, chlorine dioxide, potassium permanganate are a

29、ll possible oxidants in this type of process. The choice is primarily determined by which is the cheapest at the point of use. A secondary consideration is how effective is the oxidant. Possibly the most researchedc atalytic area is the generation and use of _OH as a very active oxidant (advanced ox

30、idation processes) 8. There are a variety of ways of doing this but the most usual is with photons and a photocatalyst. The photocatalyst is normally TiO2 but other materials with a suitable band gap can be used 9,10. The processes can be very active however the engineering difficulties of getting l

31、ight, a catalyst and the effluent efficiently contacted is not easy. In fact the poor efficiency of light usage by the catalyst (either through contacting problems or inherent to the catalyst) make this process only suitable for light from solar sources. Photons derived from electrical power that co

32、mes from fossil fuels are not acceptable because the carbon dioxide emission this implies far outweighs and COD abatement. Hydroelectric power (and nuclear power) are possible sources but the basic inefficiency is not being avoided. Hydrogen peroxide and ozone have been used with photocatalysis but

33、they can be used separately or together with catalysts to effect COD oxidation. For ozone there is the problem of the manufacturing route, corona discharge, which is a capital intensive process often limits its application and better route to ozone would be very useful. It is important to note at this point