Az értol az óceánig - A víz

A jövo kihívása

Translated title of the contribution: From rivulet to ocean - water: The challenge of the future

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Freshwater amounts to about 2.5% of the total water resource of the Earth. Within this the utilisable fraction is only 0.6% (rivers, lakes and subsurface waters). The global demand for water (80% of which is that for irrigation) is about 1 percent of the renewing resource. The problem stems from he extremely uneven spatial and temporal distribution: the occurrences of water shortage, drought and floods. Consequently one must manage the resources of water, an activity which has been successfully performed since several centuries by the Hungarian water professionals. Life in natural waters is of highly diverse type: For example in freshwaters several ten thousands of plant and animal species are found. Among these the smallest ones bacteria, downward-most along the food-chain, and algae (suspended microscopic plants) are of micron size. (Viruses, things of hardly larger size than the water molecule and causing much trouble, are not living thins, and therefore they are difficult to detect). Algae can also be of the size of several hundred microns: their size cover two-, while their volume 4-5 orders of magnitude. The largest specimen of the freshwater food-web are the fish, that can grow to several meters length. In course of the biological production the matter cycles continuously (affected also by pollution) via the producers and the decomposers of the aquatic life. In this cycling the various substance are also spatially trans-located and may interact which each other, the sediment, the soil and with the atmosphere. The multiple physical, chemical and biological processes, which vary in time and space, affect the state of the quality of water and the biogeochemical cycling of matter. Waste waters differ substantially from natural waters, due to their chemical and biological properties and to the species-poor life of them. The frequently contain pathogens. Waste water is a "spent medium" regarding industrial, communal and agricultural water use objectives. They contain various inorganic and organic polluting substances and plant nutrients in a condensed way, at high concentrations. Every substance which was used by the society will sooner or later appear in these waste waters (Figure 1). The impact of waste waters, when discharged into natural waters, may be of varying types: For example: too low or too high concentrations of elements, substances and compounds; the modification of the chemical and physical environment; the distortion of the biological cycling and thus the ecosystem; domination of certain life forms and thus the decrease of biodiversity; toxicity; health-deteriorating effects and so on (these may appear simultaneously and in interacting manner). All these hinder, make very expensive, or even eliminate the use of waters and may result in serious damages even on the long term (Figures 2-3). Presently almost all large European rivers show the signs of eutrophication. The internal seas, the Baltic and Black seas, are also suffering from this impact (Figure 4). We face two problems: a) The largest part of the pollution load, casing this problem, stem from the agriculture and is of non-point source character; b) Investigations indicated that unlike in freshwater lakes, here the limiting factor is not the phosphorus but the nitrogen or the two together. Therefore there is a need for removing nitrogen from waste waters. The solution was found, more than two decades ago, in biological denitrification (the principe was know already in the 19th Century). The need for the protection of the internal seas and the successful technological development resulted in the sewage treatment directive of the EU. For the so called sensitive areas this directive requests, from the waste water treatment of large cities, the simultaneous removal of compounds containing C, N, and P. In Hungary the cost-requirements corresponding to the compliance with this directive amounts to 1000 billion HUF (including the respective sewerage). A substantial part of global worries are connected to the increase of the population and to the decrease of the specific, per capita, resources. The growth is exponential: by the end of the 21st Century the population of our planet will exceed 10 billion. Presently about 4-6% of the population is facing problems that stem from physically insufficient amount of water, but another 20% has no access to safe drinking water, due to economic reasons, mainly in the Near-East and in Africa. Since population growth is also concentrated in the Asian and African regions, which are poor in water (in many countries the population was doubled in 20 years) this ratio can be increased to ten-fold by the year 2025, depending also on the effect of climate change (Figure 5). In Europe presently we use about daily 0.24-0.25 m3 water per capita in a prodigal way. Of this the so called physiolofical water use (WC) is about 0.05 m3/cap/day, while 0.11 m3/cap/day is used in the bathroom and in the kitchen. To this comes about 0.08 m3/cap/day water loss, depending on the site (for example seepage from the distribution network). A characteristic of the present households is that they use the best quality water, regardless of whether it is used for drinking, cooking, or toilette flushing (Figure 6). Water consumption could be reduced by 50% without any special difficulty (Figure 7) by improving the maintenance of the distribution networks, supporting the use of water-saving facilities and by using an appropriate price policy. Results of investigations indicate that the above partial uses could be reduced to 0.025, 0.055 and 0.025 m3/cap/day values, respectively. Drinking water consumption could be lowered to 0.05 m3/cap/day, if it is confined solely to kitchen and bathroom uses. In this case one would distract the physiological water use from the rest, naming the former the "black sewage", while the rest is named "grey sewage". For flushing of the toilette (if this remains in use) one could use treated "grey sewage" or precipitation water. This, however, woud require dual piping within the buildings. The flushing type toilette transports various substances and pollutants into the water phase in a uniform manner, although only 2 sources represent pollutants which must be carried away by water, as the only possible solution (Figure 8). Departing from the use of the traditional "English" WC, the various substances could, along with the decrease of water consumption, be diverted to various directions, taking into account the requirements of easy treatment, the recycling and reuse of water, the closing of the material cycles. The result of all these would be the sustainability. Here only two basic solutions are mentioned (which do not exlude each-other): (1) using the present systems with the inclusion of "biological wastes"; and (2) separation of the physiological waste and its treatment together with the biological wastes. Thus we state that our present knowledge would allow, in principle, sustainable water saving solutions, which require less energy consumption and carbon dioxide emission and is based on closed cycles. Evidently these solutions depend on the type of the settlements, on the climate and the infrastructure, on the legal regulation of environmental protection, on the flexibility of the environmental industry and on several other factors. In a real situation the options are much richer, depending also on local circumstances. Namely, we could divert the waters, together with their plant nutrient content, from the settlements towards the industry and/or agriculture (in function of the demand and the options od reuse), producing with this a water quality, which is (unlike the case of the flushing toilette just tailored to the demand of the water use in concern. A part of the water would be spent and the portion which is not recycled (this amounting only to a fraction of the present sewage quantity) would be discharged into recipient water bodies, after appropriate treatment. This line of thoughts leads as to the integrated water management of the future (Figure 9) in which the principles of prevention, cautiousness, that of the "Polluter Pays", the full recovery of costs and the efficiency of the operations are the characteristic ones. The water policy of the EU is based on these principles. As contrasted to the present solutions, the problems of water quality and quantity would not be trans-located neither in time nor in space (Figure 10). This would curtail or even eliminate transboundary impacts. Evidently, technological renewing could only lead to success if it happens along with the alteration of our own attitudes. The precondition of the latter is to improve public education and awareness from the kindergarten until old age.

Original languageHungarian
Pages (from-to)73-100
Number of pages28
JournalVizugyi Kozlemenyek
Issue number1
Publication statusPublished - 2003

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ocean
water
flushing
water use
sewage
water quality
resource
alga
drinking water
agriculture
biological production
nitrogen
technological development
lake
twenty first century
piping
drinking
pollutant source
sewage treatment
chemical process

ASJC Scopus subject areas

  • Water Science and Technology

Cite this

Az értol az óceánig - A víz : A jövo kihívása. / Somlyódy, L.

In: Vizugyi Kozlemenyek, No. 1, 2003, p. 73-100.

Research output: Contribution to journalArticle

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title = "Az {\'e}rtol az {\'o}ce{\'a}nig - A v{\'i}z: A j{\"o}vo kih{\'i}v{\'a}sa",
abstract = "Freshwater amounts to about 2.5{\%} of the total water resource of the Earth. Within this the utilisable fraction is only 0.6{\%} (rivers, lakes and subsurface waters). The global demand for water (80{\%} of which is that for irrigation) is about 1 percent of the renewing resource. The problem stems from he extremely uneven spatial and temporal distribution: the occurrences of water shortage, drought and floods. Consequently one must manage the resources of water, an activity which has been successfully performed since several centuries by the Hungarian water professionals. Life in natural waters is of highly diverse type: For example in freshwaters several ten thousands of plant and animal species are found. Among these the smallest ones bacteria, downward-most along the food-chain, and algae (suspended microscopic plants) are of micron size. (Viruses, things of hardly larger size than the water molecule and causing much trouble, are not living thins, and therefore they are difficult to detect). Algae can also be of the size of several hundred microns: their size cover two-, while their volume 4-5 orders of magnitude. The largest specimen of the freshwater food-web are the fish, that can grow to several meters length. In course of the biological production the matter cycles continuously (affected also by pollution) via the producers and the decomposers of the aquatic life. In this cycling the various substance are also spatially trans-located and may interact which each other, the sediment, the soil and with the atmosphere. The multiple physical, chemical and biological processes, which vary in time and space, affect the state of the quality of water and the biogeochemical cycling of matter. Waste waters differ substantially from natural waters, due to their chemical and biological properties and to the species-poor life of them. The frequently contain pathogens. Waste water is a {"}spent medium{"} regarding industrial, communal and agricultural water use objectives. They contain various inorganic and organic polluting substances and plant nutrients in a condensed way, at high concentrations. Every substance which was used by the society will sooner or later appear in these waste waters (Figure 1). The impact of waste waters, when discharged into natural waters, may be of varying types: For example: too low or too high concentrations of elements, substances and compounds; the modification of the chemical and physical environment; the distortion of the biological cycling and thus the ecosystem; domination of certain life forms and thus the decrease of biodiversity; toxicity; health-deteriorating effects and so on (these may appear simultaneously and in interacting manner). All these hinder, make very expensive, or even eliminate the use of waters and may result in serious damages even on the long term (Figures 2-3). Presently almost all large European rivers show the signs of eutrophication. The internal seas, the Baltic and Black seas, are also suffering from this impact (Figure 4). We face two problems: a) The largest part of the pollution load, casing this problem, stem from the agriculture and is of non-point source character; b) Investigations indicated that unlike in freshwater lakes, here the limiting factor is not the phosphorus but the nitrogen or the two together. Therefore there is a need for removing nitrogen from waste waters. The solution was found, more than two decades ago, in biological denitrification (the principe was know already in the 19th Century). The need for the protection of the internal seas and the successful technological development resulted in the sewage treatment directive of the EU. For the so called sensitive areas this directive requests, from the waste water treatment of large cities, the simultaneous removal of compounds containing C, N, and P. In Hungary the cost-requirements corresponding to the compliance with this directive amounts to 1000 billion HUF (including the respective sewerage). A substantial part of global worries are connected to the increase of the population and to the decrease of the specific, per capita, resources. The growth is exponential: by the end of the 21st Century the population of our planet will exceed 10 billion. Presently about 4-6{\%} of the population is facing problems that stem from physically insufficient amount of water, but another 20{\%} has no access to safe drinking water, due to economic reasons, mainly in the Near-East and in Africa. Since population growth is also concentrated in the Asian and African regions, which are poor in water (in many countries the population was doubled in 20 years) this ratio can be increased to ten-fold by the year 2025, depending also on the effect of climate change (Figure 5). In Europe presently we use about daily 0.24-0.25 m3 water per capita in a prodigal way. Of this the so called physiolofical water use (WC) is about 0.05 m3/cap/day, while 0.11 m3/cap/day is used in the bathroom and in the kitchen. To this comes about 0.08 m3/cap/day water loss, depending on the site (for example seepage from the distribution network). A characteristic of the present households is that they use the best quality water, regardless of whether it is used for drinking, cooking, or toilette flushing (Figure 6). Water consumption could be reduced by 50{\%} without any special difficulty (Figure 7) by improving the maintenance of the distribution networks, supporting the use of water-saving facilities and by using an appropriate price policy. Results of investigations indicate that the above partial uses could be reduced to 0.025, 0.055 and 0.025 m3/cap/day values, respectively. Drinking water consumption could be lowered to 0.05 m3/cap/day, if it is confined solely to kitchen and bathroom uses. In this case one would distract the physiological water use from the rest, naming the former the {"}black sewage{"}, while the rest is named {"}grey sewage{"}. For flushing of the toilette (if this remains in use) one could use treated {"}grey sewage{"} or precipitation water. This, however, woud require dual piping within the buildings. The flushing type toilette transports various substances and pollutants into the water phase in a uniform manner, although only 2 sources represent pollutants which must be carried away by water, as the only possible solution (Figure 8). Departing from the use of the traditional {"}English{"} WC, the various substances could, along with the decrease of water consumption, be diverted to various directions, taking into account the requirements of easy treatment, the recycling and reuse of water, the closing of the material cycles. The result of all these would be the sustainability. Here only two basic solutions are mentioned (which do not exlude each-other): (1) using the present systems with the inclusion of {"}biological wastes{"}; and (2) separation of the physiological waste and its treatment together with the biological wastes. Thus we state that our present knowledge would allow, in principle, sustainable water saving solutions, which require less energy consumption and carbon dioxide emission and is based on closed cycles. Evidently these solutions depend on the type of the settlements, on the climate and the infrastructure, on the legal regulation of environmental protection, on the flexibility of the environmental industry and on several other factors. In a real situation the options are much richer, depending also on local circumstances. Namely, we could divert the waters, together with their plant nutrient content, from the settlements towards the industry and/or agriculture (in function of the demand and the options od reuse), producing with this a water quality, which is (unlike the case of the flushing toilette just tailored to the demand of the water use in concern. A part of the water would be spent and the portion which is not recycled (this amounting only to a fraction of the present sewage quantity) would be discharged into recipient water bodies, after appropriate treatment. This line of thoughts leads as to the integrated water management of the future (Figure 9) in which the principles of prevention, cautiousness, that of the {"}Polluter Pays{"}, the full recovery of costs and the efficiency of the operations are the characteristic ones. The water policy of the EU is based on these principles. As contrasted to the present solutions, the problems of water quality and quantity would not be trans-located neither in time nor in space (Figure 10). This would curtail or even eliminate transboundary impacts. Evidently, technological renewing could only lead to success if it happens along with the alteration of our own attitudes. The precondition of the latter is to improve public education and awareness from the kindergarten until old age.",
author = "L. Somly{\'o}dy",
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language = "Hungarian",
pages = "73--100",
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TY - JOUR

T1 - Az értol az óceánig - A víz

T2 - A jövo kihívása

AU - Somlyódy, L.

PY - 2003

Y1 - 2003

N2 - Freshwater amounts to about 2.5% of the total water resource of the Earth. Within this the utilisable fraction is only 0.6% (rivers, lakes and subsurface waters). The global demand for water (80% of which is that for irrigation) is about 1 percent of the renewing resource. The problem stems from he extremely uneven spatial and temporal distribution: the occurrences of water shortage, drought and floods. Consequently one must manage the resources of water, an activity which has been successfully performed since several centuries by the Hungarian water professionals. Life in natural waters is of highly diverse type: For example in freshwaters several ten thousands of plant and animal species are found. Among these the smallest ones bacteria, downward-most along the food-chain, and algae (suspended microscopic plants) are of micron size. (Viruses, things of hardly larger size than the water molecule and causing much trouble, are not living thins, and therefore they are difficult to detect). Algae can also be of the size of several hundred microns: their size cover two-, while their volume 4-5 orders of magnitude. The largest specimen of the freshwater food-web are the fish, that can grow to several meters length. In course of the biological production the matter cycles continuously (affected also by pollution) via the producers and the decomposers of the aquatic life. In this cycling the various substance are also spatially trans-located and may interact which each other, the sediment, the soil and with the atmosphere. The multiple physical, chemical and biological processes, which vary in time and space, affect the state of the quality of water and the biogeochemical cycling of matter. Waste waters differ substantially from natural waters, due to their chemical and biological properties and to the species-poor life of them. The frequently contain pathogens. Waste water is a "spent medium" regarding industrial, communal and agricultural water use objectives. They contain various inorganic and organic polluting substances and plant nutrients in a condensed way, at high concentrations. Every substance which was used by the society will sooner or later appear in these waste waters (Figure 1). The impact of waste waters, when discharged into natural waters, may be of varying types: For example: too low or too high concentrations of elements, substances and compounds; the modification of the chemical and physical environment; the distortion of the biological cycling and thus the ecosystem; domination of certain life forms and thus the decrease of biodiversity; toxicity; health-deteriorating effects and so on (these may appear simultaneously and in interacting manner). All these hinder, make very expensive, or even eliminate the use of waters and may result in serious damages even on the long term (Figures 2-3). Presently almost all large European rivers show the signs of eutrophication. The internal seas, the Baltic and Black seas, are also suffering from this impact (Figure 4). We face two problems: a) The largest part of the pollution load, casing this problem, stem from the agriculture and is of non-point source character; b) Investigations indicated that unlike in freshwater lakes, here the limiting factor is not the phosphorus but the nitrogen or the two together. Therefore there is a need for removing nitrogen from waste waters. The solution was found, more than two decades ago, in biological denitrification (the principe was know already in the 19th Century). The need for the protection of the internal seas and the successful technological development resulted in the sewage treatment directive of the EU. For the so called sensitive areas this directive requests, from the waste water treatment of large cities, the simultaneous removal of compounds containing C, N, and P. In Hungary the cost-requirements corresponding to the compliance with this directive amounts to 1000 billion HUF (including the respective sewerage). A substantial part of global worries are connected to the increase of the population and to the decrease of the specific, per capita, resources. The growth is exponential: by the end of the 21st Century the population of our planet will exceed 10 billion. Presently about 4-6% of the population is facing problems that stem from physically insufficient amount of water, but another 20% has no access to safe drinking water, due to economic reasons, mainly in the Near-East and in Africa. Since population growth is also concentrated in the Asian and African regions, which are poor in water (in many countries the population was doubled in 20 years) this ratio can be increased to ten-fold by the year 2025, depending also on the effect of climate change (Figure 5). In Europe presently we use about daily 0.24-0.25 m3 water per capita in a prodigal way. Of this the so called physiolofical water use (WC) is about 0.05 m3/cap/day, while 0.11 m3/cap/day is used in the bathroom and in the kitchen. To this comes about 0.08 m3/cap/day water loss, depending on the site (for example seepage from the distribution network). A characteristic of the present households is that they use the best quality water, regardless of whether it is used for drinking, cooking, or toilette flushing (Figure 6). Water consumption could be reduced by 50% without any special difficulty (Figure 7) by improving the maintenance of the distribution networks, supporting the use of water-saving facilities and by using an appropriate price policy. Results of investigations indicate that the above partial uses could be reduced to 0.025, 0.055 and 0.025 m3/cap/day values, respectively. Drinking water consumption could be lowered to 0.05 m3/cap/day, if it is confined solely to kitchen and bathroom uses. In this case one would distract the physiological water use from the rest, naming the former the "black sewage", while the rest is named "grey sewage". For flushing of the toilette (if this remains in use) one could use treated "grey sewage" or precipitation water. This, however, woud require dual piping within the buildings. The flushing type toilette transports various substances and pollutants into the water phase in a uniform manner, although only 2 sources represent pollutants which must be carried away by water, as the only possible solution (Figure 8). Departing from the use of the traditional "English" WC, the various substances could, along with the decrease of water consumption, be diverted to various directions, taking into account the requirements of easy treatment, the recycling and reuse of water, the closing of the material cycles. The result of all these would be the sustainability. Here only two basic solutions are mentioned (which do not exlude each-other): (1) using the present systems with the inclusion of "biological wastes"; and (2) separation of the physiological waste and its treatment together with the biological wastes. Thus we state that our present knowledge would allow, in principle, sustainable water saving solutions, which require less energy consumption and carbon dioxide emission and is based on closed cycles. Evidently these solutions depend on the type of the settlements, on the climate and the infrastructure, on the legal regulation of environmental protection, on the flexibility of the environmental industry and on several other factors. In a real situation the options are much richer, depending also on local circumstances. Namely, we could divert the waters, together with their plant nutrient content, from the settlements towards the industry and/or agriculture (in function of the demand and the options od reuse), producing with this a water quality, which is (unlike the case of the flushing toilette just tailored to the demand of the water use in concern. A part of the water would be spent and the portion which is not recycled (this amounting only to a fraction of the present sewage quantity) would be discharged into recipient water bodies, after appropriate treatment. This line of thoughts leads as to the integrated water management of the future (Figure 9) in which the principles of prevention, cautiousness, that of the "Polluter Pays", the full recovery of costs and the efficiency of the operations are the characteristic ones. The water policy of the EU is based on these principles. As contrasted to the present solutions, the problems of water quality and quantity would not be trans-located neither in time nor in space (Figure 10). This would curtail or even eliminate transboundary impacts. Evidently, technological renewing could only lead to success if it happens along with the alteration of our own attitudes. The precondition of the latter is to improve public education and awareness from the kindergarten until old age.

AB - Freshwater amounts to about 2.5% of the total water resource of the Earth. Within this the utilisable fraction is only 0.6% (rivers, lakes and subsurface waters). The global demand for water (80% of which is that for irrigation) is about 1 percent of the renewing resource. The problem stems from he extremely uneven spatial and temporal distribution: the occurrences of water shortage, drought and floods. Consequently one must manage the resources of water, an activity which has been successfully performed since several centuries by the Hungarian water professionals. Life in natural waters is of highly diverse type: For example in freshwaters several ten thousands of plant and animal species are found. Among these the smallest ones bacteria, downward-most along the food-chain, and algae (suspended microscopic plants) are of micron size. (Viruses, things of hardly larger size than the water molecule and causing much trouble, are not living thins, and therefore they are difficult to detect). Algae can also be of the size of several hundred microns: their size cover two-, while their volume 4-5 orders of magnitude. The largest specimen of the freshwater food-web are the fish, that can grow to several meters length. In course of the biological production the matter cycles continuously (affected also by pollution) via the producers and the decomposers of the aquatic life. In this cycling the various substance are also spatially trans-located and may interact which each other, the sediment, the soil and with the atmosphere. The multiple physical, chemical and biological processes, which vary in time and space, affect the state of the quality of water and the biogeochemical cycling of matter. Waste waters differ substantially from natural waters, due to their chemical and biological properties and to the species-poor life of them. The frequently contain pathogens. Waste water is a "spent medium" regarding industrial, communal and agricultural water use objectives. They contain various inorganic and organic polluting substances and plant nutrients in a condensed way, at high concentrations. Every substance which was used by the society will sooner or later appear in these waste waters (Figure 1). The impact of waste waters, when discharged into natural waters, may be of varying types: For example: too low or too high concentrations of elements, substances and compounds; the modification of the chemical and physical environment; the distortion of the biological cycling and thus the ecosystem; domination of certain life forms and thus the decrease of biodiversity; toxicity; health-deteriorating effects and so on (these may appear simultaneously and in interacting manner). All these hinder, make very expensive, or even eliminate the use of waters and may result in serious damages even on the long term (Figures 2-3). Presently almost all large European rivers show the signs of eutrophication. The internal seas, the Baltic and Black seas, are also suffering from this impact (Figure 4). We face two problems: a) The largest part of the pollution load, casing this problem, stem from the agriculture and is of non-point source character; b) Investigations indicated that unlike in freshwater lakes, here the limiting factor is not the phosphorus but the nitrogen or the two together. Therefore there is a need for removing nitrogen from waste waters. The solution was found, more than two decades ago, in biological denitrification (the principe was know already in the 19th Century). The need for the protection of the internal seas and the successful technological development resulted in the sewage treatment directive of the EU. For the so called sensitive areas this directive requests, from the waste water treatment of large cities, the simultaneous removal of compounds containing C, N, and P. In Hungary the cost-requirements corresponding to the compliance with this directive amounts to 1000 billion HUF (including the respective sewerage). A substantial part of global worries are connected to the increase of the population and to the decrease of the specific, per capita, resources. The growth is exponential: by the end of the 21st Century the population of our planet will exceed 10 billion. Presently about 4-6% of the population is facing problems that stem from physically insufficient amount of water, but another 20% has no access to safe drinking water, due to economic reasons, mainly in the Near-East and in Africa. Since population growth is also concentrated in the Asian and African regions, which are poor in water (in many countries the population was doubled in 20 years) this ratio can be increased to ten-fold by the year 2025, depending also on the effect of climate change (Figure 5). In Europe presently we use about daily 0.24-0.25 m3 water per capita in a prodigal way. Of this the so called physiolofical water use (WC) is about 0.05 m3/cap/day, while 0.11 m3/cap/day is used in the bathroom and in the kitchen. To this comes about 0.08 m3/cap/day water loss, depending on the site (for example seepage from the distribution network). A characteristic of the present households is that they use the best quality water, regardless of whether it is used for drinking, cooking, or toilette flushing (Figure 6). Water consumption could be reduced by 50% without any special difficulty (Figure 7) by improving the maintenance of the distribution networks, supporting the use of water-saving facilities and by using an appropriate price policy. Results of investigations indicate that the above partial uses could be reduced to 0.025, 0.055 and 0.025 m3/cap/day values, respectively. Drinking water consumption could be lowered to 0.05 m3/cap/day, if it is confined solely to kitchen and bathroom uses. In this case one would distract the physiological water use from the rest, naming the former the "black sewage", while the rest is named "grey sewage". For flushing of the toilette (if this remains in use) one could use treated "grey sewage" or precipitation water. This, however, woud require dual piping within the buildings. The flushing type toilette transports various substances and pollutants into the water phase in a uniform manner, although only 2 sources represent pollutants which must be carried away by water, as the only possible solution (Figure 8). Departing from the use of the traditional "English" WC, the various substances could, along with the decrease of water consumption, be diverted to various directions, taking into account the requirements of easy treatment, the recycling and reuse of water, the closing of the material cycles. The result of all these would be the sustainability. Here only two basic solutions are mentioned (which do not exlude each-other): (1) using the present systems with the inclusion of "biological wastes"; and (2) separation of the physiological waste and its treatment together with the biological wastes. Thus we state that our present knowledge would allow, in principle, sustainable water saving solutions, which require less energy consumption and carbon dioxide emission and is based on closed cycles. Evidently these solutions depend on the type of the settlements, on the climate and the infrastructure, on the legal regulation of environmental protection, on the flexibility of the environmental industry and on several other factors. In a real situation the options are much richer, depending also on local circumstances. Namely, we could divert the waters, together with their plant nutrient content, from the settlements towards the industry and/or agriculture (in function of the demand and the options od reuse), producing with this a water quality, which is (unlike the case of the flushing toilette just tailored to the demand of the water use in concern. A part of the water would be spent and the portion which is not recycled (this amounting only to a fraction of the present sewage quantity) would be discharged into recipient water bodies, after appropriate treatment. This line of thoughts leads as to the integrated water management of the future (Figure 9) in which the principles of prevention, cautiousness, that of the "Polluter Pays", the full recovery of costs and the efficiency of the operations are the characteristic ones. The water policy of the EU is based on these principles. As contrasted to the present solutions, the problems of water quality and quantity would not be trans-located neither in time nor in space (Figure 10). This would curtail or even eliminate transboundary impacts. Evidently, technological renewing could only lead to success if it happens along with the alteration of our own attitudes. The precondition of the latter is to improve public education and awareness from the kindergarten until old age.

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