Environmental Geochemistry and Health, 1992, 14(1), page 15
Unusual sources of aluminium and heavy metals in potable waters Ronald Fuge, Nicholas J.G. Pearce and William T. Perkins Geochemistry and Hydrology Research Group, Institute of Earth Studies, University College of Wales, Aberystwyth, Dyfed SY23 3DB, UK
Abstract
Aluminium in water supplies derives from natural sources and from the use of AI2(SO4)3 in water treatment. Heavy metals such as Pb, Cu, Zn and Cd can be added to water from pipework and solder. However, it is apparent that AI and other metals in potable waters can derive from deposits on pipe walls which can be subsequently mobilised when the supply and/or treatment process is changed. Concentrations of AI in domestic supply water of the Llanbrynmair area have been shown to increase from 1 I.tg to 50 ~g L-1 during its 18 km journey along the water main. Similarly, Pb concentrations in a public building in the Aberystwyth area are found to be extremely elevated due to the metal's mobUisation from encrustations occurring on the copper pipework.
Introduction It has long been known that relatively high concentrations of aluminium can enter potable water by dissolution of the element from clays and other alumino-silicate minerals found in soils, sediments and rocks. This is particularly so when relatively acidic waters are used for domestic supplies. Another major source of AI in drinking water is the widespread use of A12(SO4)3 as a coagulant in water treatment. It has been suggested that high dietary AI may be detrimental to human health (Connery, 1990), in particular, some workers have shown a correlation between AI in drinking water and the incidence of Alzeimer's disease (Flaten, 1988; Martyn et al., 1989). This has led some water companies in Britain to discontinue the use of A1 salts in water treatment. The use of metal pipework for the movement of domestic water has been shown to cause contamination of the supply. This problem is particularly acute in areas where the water is relatively soft. Thus the problem of Pb in waters has led to much concern (Royal Commission on Environmental Pollution, 1983), while it has been shown that considerable quantities of Cu and Zn can be dissolved from pipework, and Cd can enter supplies from brass fittings (Fuge and Perkins, 1991). In addition, solder has been found to be a potential source of Pb and Sn together with several other contaminant metals. The problem of plumbo-solvency has resulted in a general ban on the use of lead water pipes, and in many cases, old lead piping has been replaced with another material, while lead-free solder is also now in general use. In the present study, we report on two water supplies in mid- Wales where recent work has highlighted another potential source of A1 and heavy metals in potable water. In the examples quoted, previously deposited coatings on
pipe walls are found to be sources of metal contamination where the supply and/or the water treatment process has been changed.
The Areas of Study and Methodology Two areas in Central Wales were studied during this work. In the first of these, the Llanbrynmair area (Figure 1), until 1990 water for public consumption was obtained from surface sources. Surface water in this region has been found to contain elevated levels of A1, typically 150-300 ~tg L -1 (F.M. Pearce, personal communication). This water was also extremely peaty and A12(SO4)3 was used to clarify it. Concern over high A1 levels in the drinking water resulted in the change, during 1990, to a borehole supply deriving from river gravels, removing the necessity for the use of any coagulant. Water samples from the new supply have been analysed, together with domestic waters from the whole area covered by this supply (Figure 1). A second area of study was a public building in the Aberystwyth area (see inset map, Figure 1) where high Pb levels were detected in the water supply during routine tests. As no lead pipes were found to be transporting water there was no obvious source of the metal in the supply. In this case, metal pipework from the building was examined and surface deposits on these were removed for analysis. In addition, water, both domestic supply and ultra- pure deionised, were left standing for 12 h in lengths of pipe (65 cm long and 100 mL volume) taken from the building. This water was subsequently analysed. All water samples were collected in acid-washed polypropylene bottles which were rinsed three times with the water before samples were taken. Analyses were performed within 48 h of collection. 500 mg samples of pipe-surface deposit were treated
16
Unusual sources of aluminium and heavy metals
Road
Borehole II
Cornmins Coch LLanbrynmair
Machynlleth
Tal-y-Wern
.-'
Aberystwyth ......
Railway line Pennar
0 (
1
2
i
i
3
4
i
J
,.
5 f
km
Figure 1 The Llanbrynmair study area. Inset map indicates Aberystwyth.
with concentrated nitric acid and the resulting solutions were filtered and diluted prior to analysis. Analyses of water and some of the pipe-surface deposits were performed by inductively coupled plasma-mass spectromeliy (ICP-MS) using a VG Instruments PQ2+. The technique used was based on a single standard calibration method using indium as an internal standard (Pearce, 1991). Some analyses of pipe-surface deposits were performed by atomic absorption spectrophotometry using a Pye-Unicam SP9.
Results and Discussion Llanbrynmair area Analyses of the borehole water which is used for the Llanbrynmair domestic supply reveal it to be low in dissolved solids and extremely low in AI (Table 1). Following minimal treatment, which includes pH correction to an alkaline condition and disinfection, the water contains even less AI. It is then passed through the supply system linking several villages indicated in Figure 1. The results for A1 in the domestic supplies are listed in Table 1, together with the distance the water has travelled from the treatment plant. It is somewhat surprising that while the water leaving the plant has very low A1 levels, increasingly higher levels are recorded at greater distances from this point. The only possible source of this increased AI in the domestic supplies must therefore be in the pipes. These pipes are the same ones that previously carried the original high A1 water from the surface sources. While the water company concerned have attempted to clean these pipes, it is apparent that sufficient AI remains on the pipe surfaces to raise the level of this element at the furthest supply point to about 50 I.tg L-I , the
Table 1 Aluminium concentrations in potable waters in the Llanbrynmair area: changes with distance along water main from treatment plant. Sample locality Borehole water Untreated Treated Domestic supplies 20th May, 1991 Cemmaes Road Tal-y-Wern Llanbrynmair
Lian Pennant 30th May, 1991 Cemmaes Road Commins Coch Tal-y-Wern Llanbrynmair Pennant
AI content (mg L-l)
Distance (km) from treatment plant
2 1
17 34 48 48 45 47 48 50
6 6 13 13 28 37 37 48
5 9 12
14 18
5 7 9 12 18
R. Fuge, N.I.G. Pearce and W.T. Perkins
17
Table 2 Analyses of water samples from a public building in Aberystwyth - copper supply pipes (all values in l.tg L-l).
Element
Water from building Standing Running
Water left overnight in copper pipe from building Pure Domestic
AI Ca Cd Cu Pb Sb Sn Zn pH
13 10,000 0.5 1,116 94 0.2 8 . 285 6.2
143 21,700 0.5 2,770 235 0.5 12 103 6.5
18 15,000 trace 131 70 nd 24 113 6.5
59 5,060 nd 3,430 300 0.6 19 125 6.3
(51)
(4,820) (nd) (20) (1) (~)
(nd) (25) (6.5)
Values in brackets = analyses of domestic supply water prior to standing in pipe. Trace Cd = detectable but below 0.5 I.tg L -1. nd = not detected.
Table 3 Analytical data for encrusting material from
copper water-supply pipes (all values in mg kg-1).
Element AI Cd Ca Pb Sb Sn Zn
1 104 0.5 32 574 0.5 11 52
Sample 2 200 5.4 112 766 0.4 31 510
3 68 trace 36 2,940 1.7 273 66
Trace Cd = detectable but below 0.2 mg kg -1.
EEC recommended level for AI in potable waters. Analytical data for Ca shows that it too exhibits a parallel increase with distance from the treatment plant, with values in the treated water leaving the plant being 3.6 mg L -1 and 5.7 mg L -1 at Pennant 18 km away. This would suggest that Ca is also being mobilised from the pipe coatings.
Aberystwyth region The water supply to a public building was found in a routine check to contain in excess of the EEC Maximum Admissible Pb Content of 50 I.tg L -1. Several other metals also exhibited enhanced levels (Table 2). On examination, it was found that no lead pipes were, or at any time had been, used for the water supply. Copper pipes were found to be in use throughout the system, and these had become extremely corroded. Pipes which were removed from the building were found to have heavy green deposits on the inside. To ascertain if these corroded copper pipes could represent a source of heavy-metal contamination of the water supply, two lengths of pipe of almost identical size and volume were sealed at one end. One of these tubes was filled with ultra- pure water while the other was filled with previously analysed domestic supply water, and the sealed
pipes were left for 12 h. The analyses (Table 2) revealed that very high levels of Pb and several other metals were leached offthe pipe walls by both the pure and the domestic supply waters. Laser ablation ICP-MS analyses of Cu pipe and brass joints revealed Pb to be undetectable. In addition, as no soldered joints were included in the lengths of pipe tested, it appeared that the pipe deposits were the source of much of the contaminant metals. Three samples of the pipe deposit material were removed and analysed following digestion with HNO3. The data are included in Table 3. From the data it is immediately apparent that very high levels of Pb reside in the pipe deposits, together with elevated levels of several other metals. The presence of appreciable quantities of Sn in the samples of pipe deposits and all of the waters analysed suggests that the original source of the Pb, in common with the Sn, was solder. In addition, Sb present in the pipe encrustations is thought to derive from the same source as this element has been detected in solder during laser ablation ICP-MS analyses of pipe materials. One of the analysed pipe- deposit samples was collected from a coating over a solder joint (sample 3, Table 3) and this sample contains very elevated levels of Pb and Sn and higher levels of Sb. The building in question was erected in the 1950s and it is likely that during the following years some of the solder was dissolved, but most was re-precipitated on the pipe walls. Until 1990, water for supply to the Aberystwyth area was treated with A12(SO4)3 but during 1990, Fe salts were used as coagulants. We contend that this change to Fe salts has resulted in the re- mobilisation of the Pb-rich pipe encrustations. Domestic supply water from the property concerned was found to be slightly acid (pH 6.5), the water used in the pipe leaching experiments being also of the same acidity. The water supply in the Aberystwyth area is, despite the use of Ca compounds in the water treatment process, very soft, and this allied to a slightly acid pH has, we feel, exacerbated the problem of dissolution of Pb from the contaminated pipe surfaces.
18
Unusual sources of aluminium and heavy metals
Conclusions The major sources of metals such as A1 and Pb in potable domestic waters are well documented, and problems of elevated levels of these metals in the supplies can be addressed in this light. However, an additional potential source of A1 and heavy metal contamination in domestic water has been highlighted in this work. Thus, previously deposited surface coatings on pipowork carrying the supply waters can be re-mobilised adding significant levels of metals to the water. Aluminium which was originally deposited from high A1 waters has been shown to be mobilised from the trunk main when a low-Al water supply was substituted. Heavy metals such as Pb, originally derived from solder, can be precipitated on the surface of copper pipes. These metals can be re-dissolved if the water chemistry changes, as when the water treatment process is modified. This can result in levels of Pb in the water supply being considerably higher than the EEC limit of 50 mg L-1 for drinking water.
Acknowledgements We would like to thank Mr G. Owen for providing the samples of pipe used in this study, and Mr E. Glyn and Mr T. Morgan of HTV for providing background information on the Llanbrynmair area. Also our thanks are due to
Severn Trent PLC for providing access to their Llanwrin treatment plant. Institute of Earth Studies Publication 224
References Connery, J. 1990. Summary report of workshop on aluminium and health, Oslo, May 2-5, 1988. Environ. Geochem. Health, 12, 179-196. Flaten, T.P. 1988. A possible relationship between aluminium in drinking water and registered death rates from Dementia (including Alzeirner's disease) in Norway. In: Thornton, I. (ed.), Geochemistry and Health. Proceedings of the Second International symposium, pp.245-256. Science Reviews Ltd, Northwood, UK. Fuge, R, and Perkins, W. 1991. Aluminium and heavy metals in potable waters of the north Ceredigion area, mid-Wales. Environ. Geochem. Health, 13, 56--65. Martyn, C.N., Osmond, C., Edwardson, J.A., Barker, D.J.P., Harris, E.C. and Lacey, R.F.. 1989. Geographical relation between Alzeimer's disease and aluminium in drinking water. Lancet, i, 59--62. Pearce, F.M. 199I. The use of ICP-MS for the analysis of natural waters and an evaluation of sampling techniques. Environ. Geochem. Health, 13, 50-55. Royal Commission on Environmental Pollution 1983. Lead in the Environment. HMSO, London. (Manuscript No.258: received October 28, 1991, and accepted after revision January 15, 1992.)
Unusual sources of aluminium and heavy metals in potable waters Ronald Fuge, Nicholas J.G. Pearce and William T. Perkins Geochemistry and Hydrology Research Group, Institute of Earth Studies, University College of Wales, Aberystwyth, Dyfed SY23 3DB, UK
Abstract
Aluminium in water supplies derives from natural sources and from the use of AI2(SO4)3 in water treatment. Heavy metals such as Pb, Cu, Zn and Cd can be added to water from pipework and solder. However, it is apparent that AI and other metals in potable waters can derive from deposits on pipe walls which can be subsequently mobilised when the supply and/or treatment process is changed. Concentrations of AI in domestic supply water of the Llanbrynmair area have been shown to increase from 1 I.tg to 50 ~g L-1 during its 18 km journey along the water main. Similarly, Pb concentrations in a public building in the Aberystwyth area are found to be extremely elevated due to the metal's mobUisation from encrustations occurring on the copper pipework.
Introduction It has long been known that relatively high concentrations of aluminium can enter potable water by dissolution of the element from clays and other alumino-silicate minerals found in soils, sediments and rocks. This is particularly so when relatively acidic waters are used for domestic supplies. Another major source of AI in drinking water is the widespread use of A12(SO4)3 as a coagulant in water treatment. It has been suggested that high dietary AI may be detrimental to human health (Connery, 1990), in particular, some workers have shown a correlation between AI in drinking water and the incidence of Alzeimer's disease (Flaten, 1988; Martyn et al., 1989). This has led some water companies in Britain to discontinue the use of A1 salts in water treatment. The use of metal pipework for the movement of domestic water has been shown to cause contamination of the supply. This problem is particularly acute in areas where the water is relatively soft. Thus the problem of Pb in waters has led to much concern (Royal Commission on Environmental Pollution, 1983), while it has been shown that considerable quantities of Cu and Zn can be dissolved from pipework, and Cd can enter supplies from brass fittings (Fuge and Perkins, 1991). In addition, solder has been found to be a potential source of Pb and Sn together with several other contaminant metals. The problem of plumbo-solvency has resulted in a general ban on the use of lead water pipes, and in many cases, old lead piping has been replaced with another material, while lead-free solder is also now in general use. In the present study, we report on two water supplies in mid- Wales where recent work has highlighted another potential source of A1 and heavy metals in potable water. In the examples quoted, previously deposited coatings on
pipe walls are found to be sources of metal contamination where the supply and/or the water treatment process has been changed.
The Areas of Study and Methodology Two areas in Central Wales were studied during this work. In the first of these, the Llanbrynmair area (Figure 1), until 1990 water for public consumption was obtained from surface sources. Surface water in this region has been found to contain elevated levels of A1, typically 150-300 ~tg L -1 (F.M. Pearce, personal communication). This water was also extremely peaty and A12(SO4)3 was used to clarify it. Concern over high A1 levels in the drinking water resulted in the change, during 1990, to a borehole supply deriving from river gravels, removing the necessity for the use of any coagulant. Water samples from the new supply have been analysed, together with domestic waters from the whole area covered by this supply (Figure 1). A second area of study was a public building in the Aberystwyth area (see inset map, Figure 1) where high Pb levels were detected in the water supply during routine tests. As no lead pipes were found to be transporting water there was no obvious source of the metal in the supply. In this case, metal pipework from the building was examined and surface deposits on these were removed for analysis. In addition, water, both domestic supply and ultra- pure deionised, were left standing for 12 h in lengths of pipe (65 cm long and 100 mL volume) taken from the building. This water was subsequently analysed. All water samples were collected in acid-washed polypropylene bottles which were rinsed three times with the water before samples were taken. Analyses were performed within 48 h of collection. 500 mg samples of pipe-surface deposit were treated
16
Unusual sources of aluminium and heavy metals
Road
Borehole II
Cornmins Coch LLanbrynmair
Machynlleth
Tal-y-Wern
.-'
Aberystwyth ......
Railway line Pennar
0 (
1
2
i
i
3
4
i
J
,.
5 f
km
Figure 1 The Llanbrynmair study area. Inset map indicates Aberystwyth.
with concentrated nitric acid and the resulting solutions were filtered and diluted prior to analysis. Analyses of water and some of the pipe-surface deposits were performed by inductively coupled plasma-mass spectromeliy (ICP-MS) using a VG Instruments PQ2+. The technique used was based on a single standard calibration method using indium as an internal standard (Pearce, 1991). Some analyses of pipe-surface deposits were performed by atomic absorption spectrophotometry using a Pye-Unicam SP9.
Results and Discussion Llanbrynmair area Analyses of the borehole water which is used for the Llanbrynmair domestic supply reveal it to be low in dissolved solids and extremely low in AI (Table 1). Following minimal treatment, which includes pH correction to an alkaline condition and disinfection, the water contains even less AI. It is then passed through the supply system linking several villages indicated in Figure 1. The results for A1 in the domestic supplies are listed in Table 1, together with the distance the water has travelled from the treatment plant. It is somewhat surprising that while the water leaving the plant has very low A1 levels, increasingly higher levels are recorded at greater distances from this point. The only possible source of this increased AI in the domestic supplies must therefore be in the pipes. These pipes are the same ones that previously carried the original high A1 water from the surface sources. While the water company concerned have attempted to clean these pipes, it is apparent that sufficient AI remains on the pipe surfaces to raise the level of this element at the furthest supply point to about 50 I.tg L-I , the
Table 1 Aluminium concentrations in potable waters in the Llanbrynmair area: changes with distance along water main from treatment plant. Sample locality Borehole water Untreated Treated Domestic supplies 20th May, 1991 Cemmaes Road Tal-y-Wern Llanbrynmair
Lian Pennant 30th May, 1991 Cemmaes Road Commins Coch Tal-y-Wern Llanbrynmair Pennant
AI content (mg L-l)
Distance (km) from treatment plant
2 1
17 34 48 48 45 47 48 50
6 6 13 13 28 37 37 48
5 9 12
14 18
5 7 9 12 18
R. Fuge, N.I.G. Pearce and W.T. Perkins
17
Table 2 Analyses of water samples from a public building in Aberystwyth - copper supply pipes (all values in l.tg L-l).
Element
Water from building Standing Running
Water left overnight in copper pipe from building Pure Domestic
AI Ca Cd Cu Pb Sb Sn Zn pH
13 10,000 0.5 1,116 94 0.2 8 . 285 6.2
143 21,700 0.5 2,770 235 0.5 12 103 6.5
18 15,000 trace 131 70 nd 24 113 6.5
59 5,060 nd 3,430 300 0.6 19 125 6.3
(51)
(4,820) (nd) (20) (1) (~)
(nd) (25) (6.5)
Values in brackets = analyses of domestic supply water prior to standing in pipe. Trace Cd = detectable but below 0.5 I.tg L -1. nd = not detected.
Table 3 Analytical data for encrusting material from
copper water-supply pipes (all values in mg kg-1).
Element AI Cd Ca Pb Sb Sn Zn
1 104 0.5 32 574 0.5 11 52
Sample 2 200 5.4 112 766 0.4 31 510
3 68 trace 36 2,940 1.7 273 66
Trace Cd = detectable but below 0.2 mg kg -1.
EEC recommended level for AI in potable waters. Analytical data for Ca shows that it too exhibits a parallel increase with distance from the treatment plant, with values in the treated water leaving the plant being 3.6 mg L -1 and 5.7 mg L -1 at Pennant 18 km away. This would suggest that Ca is also being mobilised from the pipe coatings.
Aberystwyth region The water supply to a public building was found in a routine check to contain in excess of the EEC Maximum Admissible Pb Content of 50 I.tg L -1. Several other metals also exhibited enhanced levels (Table 2). On examination, it was found that no lead pipes were, or at any time had been, used for the water supply. Copper pipes were found to be in use throughout the system, and these had become extremely corroded. Pipes which were removed from the building were found to have heavy green deposits on the inside. To ascertain if these corroded copper pipes could represent a source of heavy-metal contamination of the water supply, two lengths of pipe of almost identical size and volume were sealed at one end. One of these tubes was filled with ultra- pure water while the other was filled with previously analysed domestic supply water, and the sealed
pipes were left for 12 h. The analyses (Table 2) revealed that very high levels of Pb and several other metals were leached offthe pipe walls by both the pure and the domestic supply waters. Laser ablation ICP-MS analyses of Cu pipe and brass joints revealed Pb to be undetectable. In addition, as no soldered joints were included in the lengths of pipe tested, it appeared that the pipe deposits were the source of much of the contaminant metals. Three samples of the pipe deposit material were removed and analysed following digestion with HNO3. The data are included in Table 3. From the data it is immediately apparent that very high levels of Pb reside in the pipe deposits, together with elevated levels of several other metals. The presence of appreciable quantities of Sn in the samples of pipe deposits and all of the waters analysed suggests that the original source of the Pb, in common with the Sn, was solder. In addition, Sb present in the pipe encrustations is thought to derive from the same source as this element has been detected in solder during laser ablation ICP-MS analyses of pipe materials. One of the analysed pipe- deposit samples was collected from a coating over a solder joint (sample 3, Table 3) and this sample contains very elevated levels of Pb and Sn and higher levels of Sb. The building in question was erected in the 1950s and it is likely that during the following years some of the solder was dissolved, but most was re-precipitated on the pipe walls. Until 1990, water for supply to the Aberystwyth area was treated with A12(SO4)3 but during 1990, Fe salts were used as coagulants. We contend that this change to Fe salts has resulted in the re- mobilisation of the Pb-rich pipe encrustations. Domestic supply water from the property concerned was found to be slightly acid (pH 6.5), the water used in the pipe leaching experiments being also of the same acidity. The water supply in the Aberystwyth area is, despite the use of Ca compounds in the water treatment process, very soft, and this allied to a slightly acid pH has, we feel, exacerbated the problem of dissolution of Pb from the contaminated pipe surfaces.
18
Unusual sources of aluminium and heavy metals
Conclusions The major sources of metals such as A1 and Pb in potable domestic waters are well documented, and problems of elevated levels of these metals in the supplies can be addressed in this light. However, an additional potential source of A1 and heavy metal contamination in domestic water has been highlighted in this work. Thus, previously deposited surface coatings on pipowork carrying the supply waters can be re-mobilised adding significant levels of metals to the water. Aluminium which was originally deposited from high A1 waters has been shown to be mobilised from the trunk main when a low-Al water supply was substituted. Heavy metals such as Pb, originally derived from solder, can be precipitated on the surface of copper pipes. These metals can be re-dissolved if the water chemistry changes, as when the water treatment process is modified. This can result in levels of Pb in the water supply being considerably higher than the EEC limit of 50 mg L-1 for drinking water.
Acknowledgements We would like to thank Mr G. Owen for providing the samples of pipe used in this study, and Mr E. Glyn and Mr T. Morgan of HTV for providing background information on the Llanbrynmair area. Also our thanks are due to
Severn Trent PLC for providing access to their Llanwrin treatment plant. Institute of Earth Studies Publication 224
References Connery, J. 1990. Summary report of workshop on aluminium and health, Oslo, May 2-5, 1988. Environ. Geochem. Health, 12, 179-196. Flaten, T.P. 1988. A possible relationship between aluminium in drinking water and registered death rates from Dementia (including Alzeirner's disease) in Norway. In: Thornton, I. (ed.), Geochemistry and Health. Proceedings of the Second International symposium, pp.245-256. Science Reviews Ltd, Northwood, UK. Fuge, R, and Perkins, W. 1991. Aluminium and heavy metals in potable waters of the north Ceredigion area, mid-Wales. Environ. Geochem. Health, 13, 56--65. Martyn, C.N., Osmond, C., Edwardson, J.A., Barker, D.J.P., Harris, E.C. and Lacey, R.F.. 1989. Geographical relation between Alzeimer's disease and aluminium in drinking water. Lancet, i, 59--62. Pearce, F.M. 199I. The use of ICP-MS for the analysis of natural waters and an evaluation of sampling techniques. Environ. Geochem. Health, 13, 50-55. Royal Commission on Environmental Pollution 1983. Lead in the Environment. HMSO, London. (Manuscript No.258: received October 28, 1991, and accepted after revision January 15, 1992.)
