Document Lp3EgzeOk7gvypOMvED9LZoq7

RIT- wCrlv S*lvnt$ Chl*r6s The occurrence of chlorinated solvents in the environment March 1987 CEFIC Conseil Europeen des Federations de I'lndustrie Chimique European Council of Chemical Manufacturers' Federations 250, Avenue Louise-Box 72-B-1050 Brussels-Belgium Telephone: 02/640.20.95-Telex: 62 498 CEFICB Telefax: SL 037114 The review makes the following conclusions: the concentrations of these solvents in the atmosphere and in the aquatic environment is generally extremely low (of the order of a few ppt - 1 in 1,000,000,000,000) where local higher concentrations are measured, in ground water or in surface water, this is directly due to spillage or indiscriminate waste disposal there is no overall trend for the total concentrations in the environment to increase. Whilst atmospheric concentrations of 111-trichloroethane are still growing, the rate of change in concentration is low and is diminishing the natural degradative processes in the atmosphere are ensuring that there is no undesirable build up of these products in the environment strict observance of current Codes of Practice covering storage, handling and use of these solvents will ensure that problems of limited local contamination are reduced considerably. SL 037115 Reprinted from Chemistry & Industry, 1986, 861 -869 by Strange the Printer Ltd., Heathfietd, East Sussex TN21 8HX The occurrence of chlorinated solvents in the environment* his review covers the occurrence in the environ Tment of the four most widely used chlorinated Table 1 Western Europe consumption (kt) (Based on information from CEFIC and other producer estimates) solvents in industry: methylene chloride (ME); ME Tri Per 111-Tri 111-trichloroethane (methyl chloroform) (111-Tri); tri 1974 222 310 290 92 chloroethylene (Tri) and perchloroethylene (Pier). 1975 195 253 275 86 Much of the data published on the four solvents is 1976 207 277 290 99 brought together in this review which covers their 1977 203 257 281 109 1978 occurrence in the atmosphere, surface water and ground 1979 201 206 236 210 304 240 120 147 water. The various degradative processes are discussed, 1980 208 177 215 145 including trends in the concentration levels. The total 1981 214 159 187 146 1982 tonnage of these solvents is declining, partly because of 1983 196 191 154 151 196 172 142 140 the economic pressures and partly as a result of develop 1984 202 148 180 144 ments in cleaning process technology and cleaning 1985 195 147 172 150 plant design. 111-Tri figures do not include US imports which were around 12-15 kt/a between 1981-5, Consumption, use and emission As an introduction to this review of the occurrence of the title solvent chlorohydrocarbons in the environ ment, this section deals with their consumption in western Europe, including their pattern of use and estimated emissions into the atmosphere. The data is based on information from the Conseil Europeen des Federations de 1'Industrie Chimique (CEFIC) and other producer estimates. 111-Tri is principally in metal degreasing, Per is used mainly in drycleaning. Methylene chloride is used in Fig 1 Consumption of chlorinated solvents in western Europe Consumption-western Europe. Since the mid 1970s the consumption of Tri and Per has declined by 30-50 per cent while the consumption of 111-Tri increased initially, but has remained steady since 1979. The consumption of methylene chloride dropped by around 10 per cent over the same period. These trends are shown in the Table 1 and also in Fig 1. End-use pattern. While the consumption of Tri and 'Prepared by a workshop of the European Chemical Industry Federation, CEFIC: Paul Herbert (ICI, England); P Carbonnier (Atochem, France); L Rivolta (Montedipe, Italy); M Servais (Solvay, Belgium); F Van Mensch ________ (AKZO, Holland) and Ian Campbell of ICI. SL 037116 Table 2 End-uses of title solvents Use (%) ME Metal degreasing Dry cleaning Extraction Solvent Aerosols Adhesives ftint Stripper Intermediates > 50% 10-50 1-10 <1% *** ++ * - - + * * - it Tri - - - Per - 111-Tri - _ Table 3 Estimated emissions in air, kt/year (1984) (based on information from CEFIC and other producer estimates) ME 111-Tri Tri R:r Total Belgium Denmark Eire France h'K Germany Greece Italy Netherlands United Kingdom Spain & Fbrtugal Sub total EEC 10.0 0.9 -- 26.1 56.7 1.0 27.8 9.5 27.2 -- 159.2 Other western 14.0 European countries* 4.0 1.1 -- 21.4 22.0 0.6 13.9 3.9 21.0 3.8 91.7 8.7 2.3 0.5 0.4 21.1 18.6 1.3 11.6 1.8 17.8 NA 75.4 13.2 Total 173.1 100.4 96.4 Includes Austria, Switzerland & the Nordic countries 3.5 0.8 0.8 14.7 23.7 0.8 18.5 3.4 9.3 7.0 82.5 7.2 89.7 19.8 3.3 1.2 83.3 121.0 3.7 71.8 18.6 75.3 10.8 408.8 43.1 459.6 further solvent applications, including paint strippers, aerosols and, as an extraction solvent. The details are shown in Table 2. Estimated emissions. Direct emission of chlorinated solvents in air, as a percentage of the total consumption, have been estimated as follows: ME-86 per cent; lll-Tri-70 per cent; Tri-60 per cent; Per-60 per cent. The total emissions in air in 1984, due to end-use are given in Table 3. The occurrence of chlorinated solvents in the environment Atmosphere. The background levels of the title solvent chlorohydrocarbons in the earth's atmosphere, remote from the emissions of the substances range from 0.01-0.12 ppb. (0.01-0.12 pans in 109 by volume). The measured levels in the northern hemisphere are as follows: ME 0.04 ppb; 111-Tri 0.15-0.17 ppb; Tri 0.01 -0.02 ppb and Per 0.06-0.09 ppb. The detailed information is given in table 4 which summarises Table 3- 1A of the NASA/WHO review'. The higher level of all four substances in the northern hemisphere relative to the southern hemisphere, reflects the predominant source of release coupled with the relatively slow inter-hemisphere transfer. In the case of methyl chloroform, neither the inter-hemisphere transfer nor the equilibria of tropospheric oxidative destruction mechanisms, are likely to have reached equilibrium. The trends show that methyl chloroform has increased from approximately 0.1 ppb in 1978 in the northern hemisphere, to approximately 0.15 ppb in 1984. The corresponding levels at the equator are 0.07-0.11 ppb and in the southern hemisphere (41 South) 0.06-0.1 ppb. However, the rate of increase is slowing down. These trends are summarised in Table 3 -13 of Ref 1 and information detailed in Table 5. The lifetimes and levels of methylene chloride, trichloroethylene and perchloroethylene are so short and low respectively that it would not be possible to measure trends of the concentrations in the atmos phere. All three have almost certainly reached a steady state concentration. The lifetimes ofmethylene chloride and Per are of the order of a few months, while the life time of trichloroethylene which is more easily oxidised than Per, is of the order of a week15. The lifetime of methylchloroform is longer, being reported to be between 5 and 10 years16, 17, 18 in earlier work, or 10 years19', six years20 or nine years2 in more recent publi cations. The lifetimes of methylene chloride, methyl chloro form and perchloroethylene are shown in Table 5 (extracted from Table 3-IB of Reference 1). Slightly higher localised levels are sometimes found in ground level air in industrial areas and in air masses from such countries. Typical levels are as follows: Tri 0.01-1.0 ppb; Per 0.01-1.0 ppb; and 111-Tri 0.05-0.5 ppb. These have been summarised in CEFIC reports and elsewhere.10, 12,23 Degradation. The degradation of the title compounds in the Earth's atmosphere is a complex process essen tially consisting of oxidation by the oxygen of the air under the action of ultraviolet light from the sun.1 The reactions involved in degradation are shown in Fig 2. Because of the temperature inversion tropopause in the Earth's atmosphere at an altitude of about 8-15km (varies with latitude), the atmosphere is divided into an upper layer (stratosphere) and lower layer (tropo sphere). The ozone layer is formed mainly in the strato sphere, by conversion of diatomic 02 molecules into triatomic O, ozone molecules under the action of short wavelength UV sunlight penetrating into the strato sphere. Less ozone is formed in this way at or below the tropopause because the short wavelength light needed is greatly attenuated by absorption. Ozone is constantly being decomposed and reformed under the action of sunlight, bringing about a steady-state concentration of ozone (the `ozone layer'). Halogenated organic compounds with relatively short atmospheric lifetimes, such as the title compounds except methyl chloroform, are not able to diffuse easily upwards across the tropopause and into the stratosphere. Instead, they are held down in the troposphere and undergo degradative processes as shown in Fig 1. The lifetime of methyl chloroform is only just long enough for a small fraction of the amount to be emitted, (about 10 per cent) to pass into the stratosphere and so become involved in various stratospheric chemical reactions. This effect is calcu lated to be small, however, and is less than half of that caused by naturally occurring methyl chloride.16,17 18 Chloroalkenes (trichloroethylene and perchloro ethylene) are oxidised to carbon dioxide, water and hydrogen chloride by both ozone and hydroxyl radical. SL 037117 Table 4 Measured distributions of selected halocarbon* Compound Date of Concentration measure- + / - ment standard deviation ppt v/v Latitude Northern hemisphere average + /standard deviation ppt v/v Southern hemisphere average + /standard deviation ppt v/v Global average + /standard deviation Ref these levels has been detected, this has invariably been caused by the direct discharge of solvents to the ground surface rather than by transfer of solvent vapour from the air. Methylene chloride 12/81 CH,C1, 38.0 21.0 Evidence has been 2 published suggesting that Methyl chloroform CHjCCI, 12/81 2/81 1981 11/81 1978 1/80 149.1+/- 3.0 20 170.4 + /- 9.3 70 123.0 + /- 0.6 30S-42S 156.0 116.0 117.0 + / -- 4.0 90.0 + /-3.0 114.4 83.2 98.4 2 3 4 5 6 ? levels of solvents in freshlyfallen rainwater are higher than those expected from Henry's Law equilibrium.28 It has never been possible to Trichloroethylene C2HC1, 12/81 1981 1981 Perchloroethylene C,C1, 12/81 2/81 1981 1981 11/81 1978 71 16.0 + /-15.0 70 60.0 + /- 7.0 87.0 + /-28.0 9.0 + /- 1.0 20 71 70 30S-42S 12 0 18.0 11.0 29.0 89.0 56.0 + /-11.0 90.0 <3 5.0 9.0 + /- 1.0 14.0 + /-3.0 35.0 2 repeat this finding, and it is 4 possible that the effect is due 4 8, 9 to adsorption phenomena 2 similar to those described for 3 fluorocarbons.29 The washout 4 4 of solvents from the air by rain 5 following a local emission has 6 9 been studied, and has been found to be very inefficient.50 Methyl chloroform and methylene chloride are oxidised Conclusion. The concentrations of the title solvent by hydroxyl radical only, again forming the same chlorohydrocarbons in the atmosphere are very low, in the naturally occurring inorganic breakdown products. range of 0.01-0.1 ppb, and, in general, are not increasing. Trichloroethylene, perchloroethylene and methylene Whilst atmospheric concentrations of 111-trichloroethane chloride are destroyed so quickly in the troposphere, are increasing, the rate of increase in the troposphere is with lifetimes of a few months or less, (Reference 1, slowing down (2) reflecting the feet that equilibrium has Table 3-18) that they do not reach levels at which their not yet been reached. The rate of change in concentration transfer to the stratosphere is significant. is low and is diminishing. It has been shown that the contribution of chlorinated solvent vapour degradation to the acidity of the Surface water atmosphere is negligible.21 There is undoubtedly a heavy burden of chlorine, suggested to occur in the form of Concentration. There is a wealth of data on the hydrogen chloride and from other sources including concentrations of chlorinated solvents found in surface sea salt (l-9.108kt/year)23 and volcanic activity (9.106 water in Europe. Much of this data covers measurements kt/year).29 The relative importance of other natural made of concentrations in the Rhine and it tributaries. sources of gaseous chloride is unknown. Such sources The concentrations were measured in the rivers and lakes could include forest and grass fires and acidic soils near of Switzerland, in England and in several other European coastal areas, which might release hydrogen chloride.22 countries. Hydrogen chloride has been suggested to enhance the Reference to Henry's Law has already been made and so, ->S04 reaction, leading to increased acidity in the this shows that feirly rapid evaporation of the chlorinated atmosphere. However, the reaction energy required solvent into the atmosphere can be expected. In general, (57 kcal/mole), renders this routine extremely unlikely. concentrations are reduced by about 90 per cent within Vi-1 hour.31,52 We can conclude that only a very small Movement of volatile solvents from the atmosphere proportion of the chlorinated solvent produced and into rainwater, the oceans and ground water. consumed in Europe is traceable in surface water. A study of the relevant partition calculations, according to There are examples of relatively high concentrations, Henry's Law, clearly shows the driving force for the which can be found within short distances of known solvents to be from the aqueous phase into the sources of contamination. These concentrations tend to atmosphere. For example, at equilibrium with a fluctuate and are reduced very rapidly by dilution by concentration of 25 jrg/1 (25ppb), the levels of the title compounds in the atmosphere would be: Tri-2.2 ppm; Per-3.9 ppm; ME -1.1 ppm and Table 5 Reported trends for selected halocarbon concentrations Compound Date Increase Increase ppt Lifetime (per cent/a) (ppt/a) +/- (years) +/- Reference lll-Tri-2.7. The movement of solvents from the atmosphere + /- standard standard deviation deviation standard deviation into rainwater25 and the oceans26-27 has been studied, ME 12/81 0.90 + /-0.3 2 and measurements have been reported.1011,12 These show that the maximum levels likely to occur in rainwater, and hence in groundwater from rainfall, are very low and are of the order of 10-100 /rg/1 111-Tri 12/81 11/81 1/80 8.7 13.0 + /-3 9.00 + 2/-1 13.2 + .8/1.2 8.6 6.5 to 9 2 14 5 Unreferenced (ppb). Where ground water contamination exceeding Per 12/81 0.6 + /-0.2 1 037U8 SL Long wavelength UV light Downwards transport of 03 through 'mid-latitude gap' into troposphere Height of tropopause 7-15 km 03-------- 02 + 0('D) 0('D) + H20 Troposphere CHCI=CCI2 + 03 CCIj=CCI2 + OH" Destruction of chloroalkenes (trichloroethylene and perchloroethylene) Formation of hydroxyl radical in the troposphere occurring breakdown products OH + /CHjCI }CH3,Cc(ci3 Destruction of chloroalkanes (methylene chloride and nnethyl chloroform) Earth's surface Fig 2 Reaction scheme for the destruction of chloro-organic compounds by oxidation in the lower atmosphere (troposphere). factors of 10/10,000, depending on the local conditions. The concentrations of chlorinated hydrocarbons measured in European water range from fractions of micrograms/litre to some hundreds of micrograms/litre. The higher levels are caused by local contamination, which are quickly diluted. When the concentration levels are compared over a period of 10-15 years, it can be concluded that there is no overall upward trend. This would also be expected from theoretical consideration, based on Henry's Law, taking into account the rapid evaporation. Details are given in the following tables. The concentrations are micrograms/litre (ppb). Degradation. The behaviour of the title substances in water varies as a function of their different chemical structures (C,, C2 saturated, C, olefinic) and depending on the situation of the water (shallow surface water, running surface water, deep surface water, ground water). Only 1,1,1-trichloroethane of the title com pounds is known to react with pure neutral deoxygenated water at ambient temperatures, with a half life of 4-10 years, breaking down to HCl, vinylidine chloride and acetic acid.12 An alkaline pH will enhance this breakdown. Decomposition rates have been measured in aerated water, with and without exposure to light32, Table 7. All four compounds will also biodegrade slowly, although experience with ground water pollution shows Table 6a Tributaries of the River Rhine (Ref) Tri Per Main and Lippe (33) Main at Kostheim (34) Ruhr at Mfllheim (35) Ruhr Lippe (36) up to 70 3.20 0.7-0.9 0.3-0.9 2.1-4.1 up to 70 19.77 0.7-1.7 0.4-1.0 1.5-3.2 Small rivers in central West Germany (37) Main at Rtisselsheim (37) Ruhr at Duisburg (34) 0.2-0.9 1.2 0.45 1.1-2.7 05 0.41 Mosel (38) Neckar (38) 0.15-0.20 0.2-0.4 0.8-1.3 0.2-0.4 Other rivers in West Germany 111 -Tri ME Remarks Industrial effluents 2.16 <1 Influence of local industry n.d. n.d. Household and industrial Local industrial effluent 0.05-0.2 Local high emissions Influence of Frankfurt airport 0.05 <i Small industry emissions 1.5-2 0.6-1.0 Elbe (38) Vfcser (38) 0.7-52.3 0.5-1.5 0.2-9,9 0,5-1.5 0,7-2.1 Industrial Table 6b River Rhine partly under the influence of the tributaries (Ref) Tri Ffer 111 -Tri ME Remarks Near Koblenz (38) Length profile (38) At several places (38) From Basel to Duisburg (39) General (36) At Lobith (34) Near Dutch border(40) Near Dutch border(33) General (41) Near Main mouth (42) 0.14-1.03 0.2-0.5 0.7-3,1 0.1-2.4 1.14 1 1.1 0.23 0.75 0.22-0.97 0,02-0.7 0.2-0.9 0.3-1.1 0.2-1.3 1.53 1 1.5 1.2 0.18 0.2 0.2 5.35-171 Local high emission 2-5 >1 Industrial 1 Industrial 5 Industrial 1.0 Industrial n.d. Main is more polluted than Rhine Table 6c Rivers and lakes in Switzerland (Ref) Tri Per River Glatt (43) Lake Zurich (44) Several Lakes (39) Max. 80} normally 0.1-I.0 0.038 0.1-0.4 0.14 0.04-0.1 lit-Tri Lake Zurich (45) 0.04-0.07 General (46) 0.058 0.274 0.063 ME Remarks Local industrial effluent Remote from industrial activity Spills, waste water effluents, rainwater General back ground only 10% of samples contained* more than 1 *i/l with a detection of 0 05. Tri and Per were found in 70% of surface water SL 037119 Table 6d England (Ref) Tri Upstream of any industrial activity (47) 0.1-1.4 Several rivers (48) Surface water (49) Sea coast (49) Some 0.01-1.0 0.1-1.0 Per <0.1-16 Some lll-Tri 5-41 ME Remarks Special and varying weather conditions Industrial 0.01-1.0 Industrial 0.1-1.0 Industrial Table 6e Other European countries (Ref) Tri Swedish west coast(50) Surrounding Torino (51) Danube near Vienna (52) 0.015 0-5 0.6 0.005 0-5 0.6 Northern Greek coast (53) Surface water Netherlands (54) 0.25-3 0.1-1.5 General background 0.25-3 0.1-1.5 lll-Tri 0.046 0 ME Remarks Anthropogenic source Industrial 0.2 Dry cleaning spillage and groundwater containin' ation Industrial General Atlantic (49) 0.001-0.013 0.001-0.013 Rivers and lakes m Traces Traces urbanized areas (55) Generally sea Traces Traces (coasts) (55) Traces Traces Traces Traces that contamination with methylene chloride is much more localized owing to its relatively ready biodegradation.56 However, the above mechanisms are slow compared with the predominant mechanism of transfer to the air.31-32 The approximate evaporative half-lives of the compounds are as follows: ME 20 mins; 111-Tri 20 mins; Tri 20 mins and Per 25 mins. In all cases 90 per cent had evaporated in less than 1V2 hours. Regulations. There are numerous regulations in Europe for maximal concentrations of the title substances in effluent, surface water and drinking water. It is interesting to note that the legislation is particularly directed at concentrations discharged in the effluent resulting from operations involving chlorinated solvents. The actual concentration in the surface water will ultimately be very dependant on dilution factors and the rate of evaporation into the atmosphere, which has already been mentioned. It is not economic to require all effluent to be of drinking water quality at source. Drinking water standards are also referred to since in some countries, surface water is a major source of water for domestic consumption. Details of current legislation and recommendations are given in Tables 8a, b and c. Table 7 Decomposition rates Half life, months Dark Illuminated ME lll-Tri Tn Ptr 18 Same 6 Same 10.7 5 8.8 4 Table 8a Effluent EEC Directive (57) 76/464 4 May 1976 Fresh water, estuarial water, and sea water. List I - substances: elimination of pollution List II - substances: reduction of pollution intended. Chlorinated organics are being considered against the criteria for possible inclusion in List 1. Switzerland Verordnung (58) Abwassereinleitungen, 3 October 1980 Actual limit for all chlorinated compounds together ng/1 (as chlorine) for effluents into rivers, lakes and public sewages. Final target (QualitStsziel): 5 (tg/1 for individual compounds. Netherlands Law 13 November 1969 (59) and 28 November 1974 (60) Law 5 June 1975 (61) No discharge without permit; Figures can be fixed. Discharge into sea only according to regulation. Belgium Legislation (to be published in 1986) on limits of solvents in effluents. Total organic halogens in effluents < 150mg/l FRG Baden Wiirttemberg Law 28 June 1978 Recommendation for other `Linder' of FRG January 1983 (62) S) 5 mg/l chlorinated solvents (as chlorine) ig 5 mg/l chlorinated solvents (as chlorine) Italy Law 319 & 650 (63) 5: 1 mg/l total chlorinated solvents France Table 8b Surface water No discharge allowed. FRG Recommendation 1981 or earlier (64) 100-200 pg/l total organic chlorine final goal 30 Mg/l for individual compounds. Netherlands Planning 1985-1989 (65) No specific values for Tri and Per. All volatile organohalogens together < 5 (tg/l Table 8c Drinking water Belgium Legislation (A.R. 27 April 1984) Netherlands Recommendation (65) Decree Waterworks 2 April 1984 FRG Recommendation (66) < 100 jig/1 trihalomethanes All organhalogens together < 1 Mg/l Generally; > 1 Mg/l (for each individual chlorinated solvent) not allowed < 25 Mg/l for all compounds together `Richtwert' I Mg/l (EEC) Conclusion. "The concentrations of the title solvent chlorohydrocarbons in surface water range from fractions of a microgram/litre to some hundreds of micrograms/litre. The higher levels are clearly caused SL 037120 by local contamination, which are quickly diluted. Evaporation of the title compounds into the atmosphere is rapid with evaporative half-lives in the range of 20-25 mins. contain substantial quantities of the title compounds. Where higher concentrations are found, this can be shown to be directly due to spillage or indiscriminate waste disposal, very often over a period of many years. Ground water Clean-up processes for water Several reports contain data concerning the Various technologies are available for the removal of occurrence of chlorinated solvents in ground waters and trace quantities of the title compounds destined for a summary is included in Table 9. The maximum levels human consumption. Since chlorinated solvents have a undoubtedly occur in heavily industrialised areas, limited solubility in water, and as shown above, a while the ubiquitous background levels for all the title tendency to transfer from water to the air, treatment compounds are very low (about 0.1 pg/1), (about processes can be designed to take advantage of these 0.1 ppb). physico-chemical properties. Aeration, or the intro The high levels ofchlorinated solvent in ground water duction of air into water, has also been widely used to in industrial areas were found to be caused by a lack of remove other gases. care in handling and the indiscriminate disposal of Another technology available is adsorption involving waste solvent over a period of many years.67,68'77 the concentration ofa material at an interface or surface. Methylene chloride tends to be of considerably less Activated carbon in granular or powdered form is often significance in ground water contamination, partly used for the removal of the title compounds from because of rapid evaporation but also because of its drinking water. More recently, adsorption processes relatively ready biodegradability. based on resins and molecular sieves have been devel oped. Both aeration and adsorption technologies have Drinking water standards. A publication by the World been shown to be effective and the technologies can also Health Organisation (WHO) in 1984, deals with be applied in series. guidelines for drinking water quality. The guideline It has been reported that bacterial degradation may be values for Tri and Per are 30 pg/1 and 10 pg/1 possible under certain conditions with the title respectively.69 It must be emphasised that levels recom substances and information on the biological degra mended in the guidelines are not standards in dation of methylene chloride has been studied. These themselves, but they are intended as recommendations to support both the Table 9 Chlorinated solvents in ground waters European standards for drinking water and the international standards, which have been in existence for over a decade.70,71 The adoption of standards will clearly be influenced by national priorities and economic factors. In 1980, the EEC directive on the quality of water for human consumption was adopted.12 The guideline value for organo-chlorine compounds of 1 pg/1 was established, but no maximum level was included. The directive now has to be implemented by the member states. In Italy a limit of 30 /xg/1 is going to be applied by 1990.73 In West Germany a limit of 25 /tg/1 has been in practice for several years.37 66 The fact that the nationally permitted levels are higher than the guideline value has nothing to do with the materials discussed in this paper, and mainly reflects the need to allow for the traces of chloroform produced when drinking water is sterilized by chlorination. Conclusion. Concentrations of the title compounds in ground water vary quite Country CH CH CH CH CH CH CH D D D D D I I I I A GB NL Location Zurich Zurich Dubendorf Zurich Dubendorf Dubendorf Northern Switzerland Frankfurt Mannheim Mannheim German/Swiss border Hamburg Mannheim Karlsruhe Near border River Rhine Novate Milanese Milan Sesto San Giovanni Cities of northern Italy South of Vienna Marlow, Bucks (Max. level detected) Date 1976 1977 1977 1974 1978 1978 1984 Tri Concentrations t^g/]) ME Refs Per 111-Tri 0.1-1.9 0.08 0.65 (imol/1 (100 Mg/1) 0.92' <0.1-82 0.44-236 473-954 1.85 763 0.8 0.04-4.8 0.27 74 74 75 76 77 78 79 1979 1981 1981 1983 0.4-159 0.7-> 1,000 <0.16 & <0.30 & 2-120 2-120 Tri, Per & 111 -Tri together: from 0.5 to 1452; several figures in between: 0.9, 3.2 12.7, 175, 367, 850 30-130 30-130 30-130 80 81 82 83 1985 <0.01 0.01 0.8 84 7.0 2.8 0-6 4.5 85 1980-81 12-80 34-138 4-20 9-29 86 87 1981-82 1983 0.1-1.1 (max 81-158) <1->10 0.1-0.3 (max 15-32) <1->10 < l-> 10 88 89 1981 - Generally <2 1,100 Generally (max 4 & 70) <2 < 22 0.1 90 91 widely. The ubiquitous background levels are fractions of a microgram/litre (ppb), whilst contaminated water may NL NL 1982 (*) In 50% of ground water sources 1 (*) <0.01-1 < i(*) 92 93 SL 037121 results may be relevant to clean up process options. tests known as adsorption isotherms. Steam stripping is a useful technique for recovering Adsorption isotherms and other equilibrium tests solvent from an effluent or at least ensuring that the permit the development of an equilibrium equation residual concentration is acceptable (levels of 1 mg/litre which relates the concentration of adsorbate (solvent) in can be achieved). the liquid phase to the concentration of adsorbate on the solid phase (concentration of solvent absorbed per unit Aeration. When water containing a dissolved volatile or weight of activated carbon). This allows an estimate to semi-volatile compound is in contact with air, an be given of the amount of activated carbon necessary to equilibrium of molecules migrating from the water to treat water with a given concentration of solvent. the air (evaporating) and from the air to water Adsorption of solvent from contaminated water is (dissolving) is established. Henry's Law describes the achieved practically by passing the water through a bed relationship of the concentration of a substance in the of granular activated carbon. Contaminant molecules liquid phase, (dissolved in water) to the partial pressure penetrate deeper into the bed, and the appearance of of the compound in the vapour phase (concentration in detectable concentrations of solvent in the treated water air). There is a direct relationship between these two is known as break through. When the concentration of parameters. The coefficient of proportionality is known volatile organic solvent (VOC) in the treated water as Henry's Law coefficient. By providing an environ reaches an unacceptable level, the activated carbon in ment where the concentration in air is low-i.e. by the bed is removed and replaced with either virgin continuously replacing semi-saturated air with fresh carbon or reactivated carbon. air-the system will tend toward an equilibrium con dition of low concentration in water. Resins. Adsorption of chlorinated solvents can also be Because of their relatively low solubility and high achieved using columns packed with certain resins94. vapour pressure, these solvents have a natural tendency Another technique is to use a molecular sieve. These to migrate from water to the air, giving them relatively options are expected to attract increasing interest in the high Henry's Law coefficients. This tendency can be next few years. They are particularly suitable for put to use in aeration treatment systems which enhance achieving low contaminant levels after initial stripping the migration, or transfer, by providing large water/air by aeration. interfacial areas, large volumes of air relative to the volume of water treated and sufficient contact time for the transfer to occur. Bacterial degradation. Another method which is beginning to attract interest, is the possibility of bio Granular activated carbon. Activated carbon removes organic contaminants from water by the mechanism of degradation95. Good results have been reported with methylene chloride96,97 98. Mechanisms have been proposed by Parsons et al and the subject reviewed by adsorption. Contaminant molecules migrate to the Kastner et a/99,100. external surface of the carbon and into the exten sive pore structure in the Table 10 Location of packed towers aeration in USA (Federal Register/40 CFR Parts 141/t42)'"'-,0J interior of the carbon par ticle, where they are effectively removed from the solution. The capacity of acti vated carbon is a function of: the type of carbon * the molecular struc ture of the compound the concentration of the compound in water Location Wjrthsmith AFB Liberty Fairfield (Mi) (Mo) (NJ) Rockawav Rock Hill Brewsier Upper Merion Warrington Tacoma Hartland (NJ) (NJ) (NY) (PA) (PA) (WA) (WL) Major contaminant Tri Tri Tri 111-Tri Per Tri Tri ftr Tri Tri Tri Tri Raw water concentration range (pg/1) (50-8000) (36-69) (26-400) (17-29) (2-172) (50-220) (45-96) (420-470) (3-20) (3-20) (54-130) (175) Air: water ratio 25:1 - Percent removal 99.9 80 - 96 - 144:1 83:1 33.1 11:1 40:1 62,1 50:1 99 99 90 94 97 95 99 Treated in water concentration Gig/1) 4-8 7.4 TCE 1-16 111 -Tri 1-12 Total < 10 PCE 1-7 < 1-2 <1 4-6 < 1-1.2 4 7 <2 the presence of Table 11 Purification of ground water competing organic Biesierfield - Cologne10-' West Germany substances and a number of other factors. Because the effect of all the many factors on the adsorption capacity can not be well defined, ca pacity is determined em Product Trichloroethylene Perchloroethylene 1000 ug/1 111 -Trichloroethane Depth 9m Methylene chloride Water flow (output)-48 m!/h Concentration discharge of chlorinated solvent < 25 pg/litre lll-Tri Per Energv - 25,000 DM Analysis - 20/25,000 DM Maintenance - 5/10,000 DM " pirically, usually by laboratory equilibrium Investments- 75,000 DM x 2 = 150,000 DM Price per m5 of processed water: 7 Pfg SL 037122 Clean-up process evaluation Packed tower aeration and granular active carbon (adsorption) are considered to offer the most efficient technology. The advantages of these systems include: high level (99% or more) of VOC removal; no limit to climatic conditons such as temperature or geographic conditions; compatibility with other water treatment processes; installation can either be at the well head or in central treatment plant; relatively economic equipment necessary for the work is commercially available; no pre-existing structure is required. Considerable experience has been obtained with both technologies over a number of years. For example: packed tower aeration has been successfully applied to the removal of VOC's in at least 24 full scale plants in the USA. Granular active carbon has been applied in at least five plants in USA to the removal of VOC's. References 1 Woi Id Inteorological Organization Global Ozone Research Monitoring Project - Report No. 16. 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EPA/600-9-85/025 September 1985 98 Proceedings international conference on new frontiers for hazardous wastes management, Cincinnati, M-, OHM 45268, EPA/600-9-85/025 September 1985 99 Parsons, F., Lage, G.B. & Rice, R., Env. Tox. and Chem., 1985. 4, 739-42 100 Kaestner, M., Harborth, P-, & Hanert, H.H., Biologische Endoxidation leichtfliichtiger Halogenkohlenwasserstoffen Seminar \r S-7I-I04-09/-6, Haus de Technik, 4300 Essen 1986 101 Federal Rcgister/40 CFR Part 141, 1985, 46, 880-46, 901 102 Federal Rcgister/40 CFR Parts 141-142, 1985, 46, 902-46, 936 103 Ministerium filr ErnShrung, Landwirtschaft, Umwelt und Forsten Baden-Wtirttemberg. Leitfaden fur die Beuneilung and Behandlung von Grundwasser-Verunreimgungen dutch leichtfltichtige Chlorkohlenwasscrstoffe - Stand August 1983. SL 037124