西安建筑科技大学：《水资源利用与保护》参考资料_Wastewater as a resource_Wastewater as a resource - EuroCase Paris

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2 Content Overview Wastewater as a resource – what are the options?……………………………………………. 3 Prof. H. Ødegaard (N), Norwegian University of Science and Technology, Trondheim, Norway Reuse/recycling of reclaimed wastewater Achievements and challenges in the reuse of reclaimed wastewater……………………….. 9 Prof. R. Mujeriego (E), ETS Ingenieros de Caminos, Barcelona, Spain Recycling of treated wastewater for agricultural and landscape irrigation – treatment options and challenges …………………………………………………………… 14 Prof. G. Oron (IL), Ben-Gurion University of the Negev, Israel Recycling of treated wastewater for industrial reuse – treatment options and challenges…… 16 Prof. L. Bonomo (I), Politecnico di Milano, Italy Recycling of treated wastewater for indirect potable and urban reuse – treatment options and challenges……………………………………………………………………………………… 24 Prof. Takashi Asano, University of California, Davis, USA Public health aspects in wastewater reclamation, recycling and reuse - treatment options and challenges……………………………………………………………………………………… 28 Prof. J. Bontoux (F), Université Montpellier, Montpellier, France Reuse/recycling of resources in wastewater sludge Challenges in the reuse of resources in wastewater sludge……………………………………. 31 Dr. Peter Matthews (UK), Pelican Portifolio, Cambridge, UK Use of sludge on farmland as fertiliser/soil conditioner……………………………………….. 38 Prof. Jens Aage Hansen (DK), University of Aalborg, Denmark The production and utilization of constructed soil conditioner/compost made from wastewater sludge and other components…………………………………………………………………. 43 Dr. Ing. Ludovico Spinosa (I), C.N.R.-Nat. Res. Council, Bari, Italy Alternatives to agricultural use of sludge…………………………………………………….. 48 Prof. Helmut Kroiss (A), Technische Universität, Wien, Austria Wastewater as a resource – What is the future?……………………………………………… 53 Ms Valentina Lazarova (F), Suez Lyonnaise des Eaux

WASTEWATER AS A RESOURCE- WHAT ARE THE OPTIONS? Hallvard odegaard Faculty of Civil and Emvironmental Engineering, Norwegian University of Science and Technology(NTNU), N-7491 Trondheim, Norway. E-mail: hallvard odegaard(@byggntnu. no INTRODUCTION Control of the epidemics, especially cholera, that ravaged many of the major European cities in the middle of the 18th century, was the driving force behind the development of wastewater systems The sanitation conditions had become a threat to the urban human health. Since the introduction of centralised water supply and sewerage systems, the cities of Europe has, however, been essentially free of water-borne epidemics. Around the middle of the 19'th century, discharges of wastewater (sewage as well as industrial waste)for the ever expanding industrialised society, resulted in unacceptable pollution in receiving waters, threatening aquatic life as well as human health. The cceptance of the need for pollution control, leads to the construction of wastewater treatment plants. Today these are taken for granted as part of the infrastructure of a city. Even though people living in the countryside did not experience the epidemics development caused by poor sanitation to the same extent as the cities did, centralised wastewater systems were also established for small communities and villages. Even in scattered dwellings the convenience of using water toilets lead to small on-site wastewater systems that required treatment With respect to management of the water resources, the links between the cities and the countryside become ever more evident. The wastewater treatment plants produce sludge and this sludge has to be taken care of in the countryside somehow. The countryside needs water to produce food for the cities, but the cities water is used by the cities that are also polluting the water. This clash of interests has lead to the focus on" Sustainable Urban Water Systems'". Two schools of thought have eme 1. The present centralised wastewater systems are unsuitable in the future and should be replaced by alternative systems based on local handling 2. The present system is the only realistic one in an urban environment and will be maintained in foreseeable future, but it should be modified to be more in agreement with the principles of sustainable development It is very difficult to comprehend how Europe can meet the vast economical consequences of a total system change. Therefore, we have to take our present system as the stepping-stone for a development towards a more sustainable society. Wastewater has traditionally been looked upon a problem or waste. This work-shop aims at showing that wastewater should rather be regarded as a RESOURCES IN WASTEWATER There are principally 3 resource components in wastewater 1. The water itself 2. The heat of the water(energy 3. The constituents in the wastewater(primarily nutrients and carbon

3 WASTEWATER AS A RESOURCE – WHAT ARE THE OPTIONS? Hallvard Ødegaard* * Faculty of Civil and Environmental Engineering, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway. E-mail: hallvard.odegaard@bygg.ntnu.no INTRODUCTION Control of the epidemics, especially cholera, that ravaged many of the major European cities in the middle of the 18’th century, was the driving force behind the development of wastewater systems. The sanitation conditions had become a threat to the urban human health. Since the introduction of centralised water supply and sewerage systems, the cities of Europe has, however, been essentially free of water-borne epidemics. Around the middle of the 19’th century, discharges of wastewater (sewage as well as industrial waste) for the ever expanding industrialised society, resulted in unacceptable pollution in receiving waters, threatening aquatic life as well as human health. The acceptance of the need for pollution control, leads to the construction of wastewater treatment plants. Today these are taken for granted as part of the infrastructure of a city. Even though people living in the countryside did not experience the epidemics development caused by poor sanitation to the same extent as the cities did, centralised wastewater systems were also established for small communities and villages. Even in scattered dwellings the convenience of using water toilets lead to small on-site wastewater systems that required treatment. With respect to management of the water resources, the links between the cities and the countryside become ever more evident. The wastewater treatment plants produce sludge and this sludge has to be taken care of in the countryside somehow. The countryside needs water to produce food for the cities, but the cities water is used by the cities that are also polluting the water. This clash of interests has lead to the focus on “Sustainable Urban Water Systems”. Two schools of thought have emerged: 1. The present centralised wastewater systems are unsuitable in the future and should be replaced by alternative systems based on local handling 2. The present system is the only realistic one in an urban environment and will be maintained in foreseeable future, but it should be modified to be more in agreement with the principles of sustainable development. It is very difficult to comprehend how Europe can meet the vast economical consequences of a total system change. Therefore, we have to take our present system as the stepping-stone for a development towards a more sustainable society. Wastewater has traditionally been looked upon as a problem or waste. This work-shop aims at showing that wastewater should rather be regarded as a resource. RESOURCES IN WASTEWATER There are principally 3 resource components in wastewater 1. The water itself 2. The heat of the water (energy) 3. The constituents in the wastewater (primarily nutrients and carbon )

When purifying the wastewater, one gets primarily two outgoing streams, 1)the treated water stream and 2)the sludge stream. Both of these streams contain all the three resource components mentioned above, but these resources will be utilised differently depending on in which stream they such)and the heat of the water is most important. The sludge stream is more important Wh ater(a are present. The water stream is quantitatively much larger that the sludge stream and the wa to recovery of nutrients and energy based on its carbon content carbon (biogas, heat from incineration) REUSE OF THE TREATED WATER Generally the use of water has been supply driven. As it has been an abundant commodity in most places, water has been supplied in large quantities at a very cheap price. This will have to change in therefore changing fion ns that are short of fresh water supplies. The policy of water management is the future in many regi n being supply driven to demand driven. In a demand driven situation the price of water will increase and it is possible that even extensive treatment of wastewater may turn out to be cost effective in order to produce the necessary amount of freshwater There are many possibilities for reuse of reclaimed wastewater, such as 1) for agricultural and landscape irrigation, 2)for urban reuse, 3)for industrial reuse and 4) for potable water supply. The different uses require different degrees of purity of the water, and water quality standards for this has been established (WHO, 1973, 1989). Today there are treatment technologies available that can produce reclaimed water from wastewater for these applications( Mujeriego and Asano, 1999). The greatest challenges in the reuse of reclaimed wastewater are: 1)the safeguarding of the hygienic quality, 2) the prevention of soil contamination and 3) the prevention of ground water contamination Reclaimed wastewater for agricultural and landscape irrigation In most countries the greatest demand for water is for agricultural and urban irrigation. The wastewater resource to be utilised is firstly the water as such and secondly the nutrients in the wastewater Wastewater purification at"sewage farms" was an example of zero discharge based on the"assimilative"and"self-purification power of soil(Bouwer, 1993). Even though there are a few remaining of these"sewage farms", the vast area required close to the city as well as health regulations, has made them disappear. After WHo in 1973 proposed unrealistically stringent guidelines for the quality of the effluent to irrigate crops, WHO issued in 1989 new guidelines for aqua-culture and non-potable urban uses. This new set of guidelines is controversial but has allowed a real development of wastewater reuse for irrigation purposes(WHO, 1973, 1989) Reclaimed wastewater for urban reuse Urban reuse can primarily be divided in two 1. Reuse of reclaimed wastewater for toilet flushing in dual distribution systems 2. Reuse of reclaimed wastewater for recreational lakes and brooks as well as for creation of wetlands and wildlife habitat Dual distribution systems segregate the potable water supply from the non-potable system distribution systems can be developed in two ways. One approach is to construct a city-wide sy in which the wastewater is returned to a central wastewater treatment plant for processing before being redistributed to the population to be used in the non-potable water supply system. The other approach is using small-scale individual systems where"grey"water, the wastewater from washing operations(sinkS, bathtubs, showers, wash machines) and other non-faecal wastewater is treated

4 When purifying the wastewater, one gets primarily two outgoing streams; 1) the treated water stream and 2) the sludge stream. Both of these streams contain all the three resource components mentioned above, but these resources will be utilised differently depending on in which stream they are present. The water stream is quantitatively much larger that the sludge stream and the water (as such) and the heat of the water is most important. The sludge stream is more important with respect to recovery of nutrients and energy based on its carbon content carbon (biogas, heat from incineration). REUSE OF THE TREATED WATER Generally the use of water has been supply driven. As it has been an abundant commodity in most places, water has been supplied in large quantities at a very cheap price. This will have to change in the future in many regions that are short of fresh water supplies. The policy of water management is therefore changing from being supply driven to demand driven. In a demand driven situation the price of water will increase and it is possible that even extensive treatment of wastewater may turn out to be cost effective in order to produce the necessary amount of freshwater. There are many possibilities for reuse of reclaimed wastewater, such as 1) for agricultural and landscape irrigation, 2) for urban reuse, 3) for industrial reuse and 4) for potable water supply. The different uses require different degrees of purity of the water, and water quality standards for this has been established (WHO, 1973, 1989). Today there are treatment technologies available that can produce reclaimed water from wastewater for these applications (Mujeriego and Asano, 1999). The greatest challenges in the reuse of reclaimed wastewater are: 1) the safeguarding of the hygienic quality, 2) the prevention of soil contamination and 3) the prevention of ground water contamination. Reclaimed wastewater for agricultural and landscape irrigation In most countries the greatest demand for water is for agricultural and urban irrigation. The wastewater resource to be utilised is firstly the water as such and secondly the nutrients in the wastewater. Wastewater purification at “sewage farms” was an example of zero discharge based on the “assimilative” and “self-purification” power of soil (Bouwer, 1993). Even though there are a few remaining of these “sewage farms”, the vast area required close to the city as well as health regulations, has made them disappear. After WHO in 1973 proposed unrealistically stringent guidelines for the quality of the effluent to irrigate crops, WHO issued in 1989 new guidelines for aqua-culture and non-potable urban uses. This new set of guidelines is controversial but has allowed a real development of wastewater reuse for irrigation purposes (WHO, 1973, 1989). Reclaimed wastewater for urban reuse Urban reuse can primarily be divided in two: 1. Reuse of reclaimed wastewater for toilet flushing in dual distribution systems 2. Reuse of reclaimed wastewater for recreational lakes and brooks as well as for creation of wetlands and wildlife habitat Dual distribution systems segregate the potable water supply from the non-potable system. Dual distribution systems can be developed in two ways. One approach is to construct a city-wide system in which the wastewater is returned to a central wastewater treatment plant for processing before being redistributed to the population to be used in the non-potable water supply system. The other approach is using small-scale individual systems where “grey” water, the wastewater from washing operations (sinks, bathtubs, showers, wash machines) and other non-faecal wastewater is treated

and redistributed to the non-potable water supply system. The latter of the systems have been more extensively used that the first one, caused by the fact that it can be implemented without interfering with the public city water and wastewater system. It is especially used in high-rise buildings, hotels, resorts etc The environmental movement has more and more focused on restoring natural environments within cities by establishing or restoring brooks and lakes as well establishing the basis for wetlands and wildlife habitats. For this purpose, reclaimed wastewater (or run-off water)is being extensively more used Reclaimed wastewater for industrial reuse Internal water recycling has been implemented successfully in several industries, while use of reclaimed municipal wastewater is less common. Because of the large volume, reclaimed wastewater can be particularly suitable for cooling-system make-up water, boiler feed water process waters for various production industries (i.e. iron and steel, textile etc)and wash-down waters(car wash etc). While requirements for irrigation applications tend to vary seasonally industrial water needs are more consistent. This makes reclaimed wastewater for industrial reuse easier to plan for Reclaimed wastewater for potable water supply Planned direct potable reuse of reclaimed wastewater is seldom used. The most well known is the operation in Windhoek, Namibia( Harhoff and van der Merwe, 1996). This fact is not caused by inability to produce potable water from wastewater or even to the cost of this, but rather by the public acceptance or, more accurately, public rejection of reclaimed wastewater as a potable water supply. The fact that people do not seem to object to reclaimed water from polluted rivers that carries water in which a very substantial fraction originates from sewage, is probably a matter of not knowing"(as long as I do not know, it does not matter) Much more common is planned indirect potable reuse in which treated wastewater is discharged to the groundwater, recharging this before used as a potable water source. The purpose of groundwater include: 1)arresting the decline of groundwater levels due to excessive groundwater withdrawals 2) protection of coastal aquifers against salt water intrusion from the ocean, and 3)to store the surface water(including reclaimed wastewater)for future use(Asano, 1998) RECLAMATION OF RESOURCES IN THE SLUDGE The wastewater sludge contains many different components, both valuable resources such organic matter, nutrients and metals(i.e. residual coagulants), as well as problematic components such as heavy metals and bacteria, virus's etc. The valuable resources in sludge may be reclaimed/reused in three ways 1. by direct use of sludge on farmland as fertiliser/soil conditioner 2. By use of a constructed soil conditioner(bio-soil) 3. By use of reclaiming resources(energy, nutrients, metals, etc) from the sludge through treatment Wastewater sludge may turn out to be a very valuable phosphorous source for producing P-fertiliser in the future. In 1989, the Phosphorous Resources Institute of Japan estimated that the phosphate rock in the world would remain for only 50 years at the use of the resources as at that time Watanabe et al, 2000)

5 and redistributed to the non-potable water supply system. The latter of the systems have been more extensively used that the first one, caused by the fact that it can be implemented without interfering with the public city water and wastewater system. It is especially used in high-rise buildings, hotels, resorts etc. The environmental movement has more and more focused on restoring natural environments within cities by establishing or restoring brooks and lakes as well establishing the basis for wetlands and wildlife habitats. For this purpose, reclaimed wastewater (or run-off water) is being extensively more used. Reclaimed wastewater for industrial reuse Internal water recycling has been implemented successfully in several industries, while use of reclaimed municipal wastewater is less common. Because of the large volume, reclaimed wastewater can be particularly suitable for cooling-system make-up water, boiler feed water, process waters for various production industries (i.e. iron and steel, textile etc) and wash-down waters (car wash etc). While requirements for irrigation applications tend to vary seasonally, industrial water needs are more consistent. This makes reclaimed wastewater for industrial reuse easier to plan for. Reclaimed wastewater for potable water supply Planned direct potable reuse of reclaimed wastewater is seldom used. The most well known is the operation in Windhoek, Namibia (Harhoff and van der Merwe, 1996). This fact is not caused by inability to produce potable water from wastewater or even to the cost of this, but rather by the public acceptance or, more accurately, public rejection of reclaimed wastewater as a potable water supply. The fact that people do not seem to object to reclaimed water from polluted rivers that carries water in which a very substantial fraction originates from sewage, is probably a matter of “not knowing” (as long as I do not know, it does not matter). Much more common is planned indirect potable reuse in which treated wastewater is discharged to the groundwater, recharging this before used as a potable water source. The purpose of groundwater include: 1) arresting the decline of groundwater levels due to excessive groundwater withdrawals, 2) protection of coastal aquifers against salt water intrusion from the ocean, and 3) to store the surface water (including reclaimed wastewater) for future use (Asano, 1998). RECLAMATION OF RESOURCES IN THE SLUDGE The wastewater sludge contains many different components, both valuable resources such as organic matter, nutrients and metals (i.e. residual coagulants), as well as problematic components such as heavy metals and bacteria, virus’s etc. The valuable resources in sludge may be reclaimed/reused in three ways: 1. By direct use of sludge on farmland as fertiliser/soil conditioner 2. By use of a constructed soil conditioner (bio-soil) 3. By use of reclaiming resources (energy, nutrients, metals, etc) from the sludge through treatment Wastewater sludge may turn out to be a very valuable phosphorous source for producing P-fertiliser in the future. In 1989, the Phosphorous Resources Institute of Japan estimated that the phosphate rock in the world would remain for only 50 years at the use of the resources as at that time (Watanabe et al, 2000)

Direct use of sludge on land In many countries use of sludge on land has been the preferred way of final disposal of the sludge It both solves a disposal problem for the wastewater treatment plant owners and it has a value for the farmers in terms of the fertiliser and soil conditioner effect. It is technically feasible to treat the sludge to such a degree that it could be used on farm land without any danger, and this direct reuse of the resources in sludge is probably the most sustainable one. Nevertheless, it is a fact that the use of sludge on farmland has been reduced over the years in Europe. This is caused by factors such as; (1)the amount of sludge has exceeded the soil carrying capacity of that region when also the disposal of manure is taken into account,(2) the sludge has contained unacceptably high concentrations of heavy metals, (3)the distance of transport of the sludge to farm-land has been too ar to be economically feasible and (4)there has been a fear among the farmer population and the public that food grown on sludge treated soils is not considered safe enough by the public In order to deal with the problems of heavy metal accumulation in soil as well as possible hygieni contamination, strict rules and regulations have to be complied with, concerning the pre-treatment of the sludge as well as the area loading of the sludge on the land(Matthews, 1996). In some countries the sludge that is approved for farmland use(for certain crops, such as cereals) has to be disinfected stabilised and dewatered and comply with maximal values of heavy metal content and content of certain bacteria Use of a constructed soil conditioner made from mixtures of sludge and other components In many regions there is a need for soil conditioner, both for farmland as well as for road/highway embankments, golf courses, skiing courses, parks, football fields, green houses etc. There are now various companies that make a living out of making a soil conditioner for this market by mixing treated(for instance composted) sludge with sand and other filling materials and selling this as a pecial product(bio-soil etc)that is psychologically not associated with sludge. There is reason to believe that this use of sludge will increase in the future, as the demand for the product is likely to Increase Indirect use of sludge through the extraction of resources Constituents that can be reclaimed from treatment of the sludge are for instance 1. Energy in the form of Biogas from anaerobic digestion Biofuel to produce heat from incineration plants 2. Fertilisers in the form of organic C, P and n( the latter from sludge water) 3. Soluble organic matter to be used as carbon source in biological nutrient removal plants 4. Coagulants, from sludge of treatment plants where coagulants have been added There are several commercially available processes for such reclamation of resources, for instance the KrePro process developed in Sweden( Cassidy, 1998) a process that is directly designed for the conversion of sludge to a valuable product is the sludge to oil process in which dewatered sludge undergoes pyrolysis to oil and tar. The tar is used for heating the pyrolysis unit(Campell, 1989)(Steger and Meibner, 1999) A marketing survey carried out in Northern Europe a couple of years ago, demonstrated that there was a support among wastewater plant owners for the establishment of private companies(slud reclamation factories)that would be paid to take the sludge and reclaim resources that could be sold in the market place

6 Direct use of sludge on land In many countries use of sludge on land has been the preferred way of final disposal of the sludge. It both solves a disposal problem for the wastewater treatment plant owners and it has a value for the farmers in terms of the fertiliser and soil conditioner effect. It is technically feasible to treat the sludge to such a degree that it could be used on farm land without any danger, and this direct reuse of the resources in sludge is probably the most sustainable one. Nevertheless, it is a fact that the use of sludge on farmland has been reduced over the years in Europe. This is caused by factors such as; (1) the amount of sludge has exceeded the soil carrying capacity of that region when also the disposal of manure is taken into account, (2) the sludge has contained unacceptably high concentrations of heavy metals, (3) the distance of transport of the sludge to farm-land has been too far to be economically feasible and (4) there has been a fear among the farmer population and the public that food grown on sludge treated soils is not considered safe enough by the public. In order to deal with the problems of heavy metal accumulation in soil as well as possible hygienic contamination, strict rules and regulations have to be complied with, concerning the pre-treatment of the sludge as well as the area loading of the sludge on the land (Matthews, 1996). In some countries the sludge that is approved for farmland use (for certain crops, such as cereals) has to be disinfected, stabilised and dewatered and comply with maximal values of heavy metal content and content of certain bacteria. Use of a constructed soil conditioner made from mixtures of sludge and other components In many regions there is a need for soil conditioner, both for farmland as well as for road/highway embankments, golf courses, skiing courses, parks, football fields, green houses etc. There are now various companies that make a living out of making a soil conditioner for this market by mixing treated (for instance composted) sludge with sand and other filling materials and selling this as a special product (bio-soil etc) that is psychologically not associated with sludge. There is reason to believe that this use of sludge will increase in the future, as the demand for the product is likely to increase. Indirect use of sludge through the extraction of resources Constituents that can be reclaimed from treatment of the sludge, are for instance: 1. Energy in the form of: • Biogas from anaerobic digestion • Biofuel to produce heat from incineration plants 2. Fertilisers in the form of organic C, P and N (the latter from sludge water) 3. Soluble organic matter to be used as carbon source in biological nutrient removal plants 4. Coagulants, from sludge of treatment plants where coagulants have been added There are several commercially available processes for such reclamation of resources, for instance the KREPRO process developed in Sweden (Cassidy, 1998) A process that is directly designed for the conversion of sludge to a valuable product is the sludge to oil process in which dewatered sludge undergoes pyrolysis to oil and tar. The tar is used for heating the pyrolysis unit (Campell, 1989) (Steger and Meibner, 1999). A marketing survey carried out in Northern Europe a couple of years ago, demonstrated that there was a support among wastewater plant owners for the establishment of private companies (sludge reclamation factories) that would be paid to take the sludge and reclaim resources that could be sold in the market place

EXTRACTING ENERGY FROM WASTEWATER AND WASTEWATE SLUDGE Wastewater is an energy source. The two major energy sources are the heat of the wastewater and the organic material. The main routes by which the energy potential of the wastewater can be utilised. are By extracting heat from the wastewater through heat pumps By producing biogas from the wastewater sludge through anaerobic digestion By producing excess heat through incineration of dewatered wastewater sludg The wastewater as a heat source The wastewater produced in a city every day is normally cooler in summer and warmer in winter than the outdoor air, making it suitable as a heat source used by heat pumps for heating and cooling The wastewater of the cities contains enormous quantities of thermal energy. For instance, heat contained in Tokyo's wastewater is estimated at 39 of the total waste heat, about 10%GJ(2, 7*10 MWh). Using this huge heat source for district heating and cooling in cities by water-source heat pumps can save considerable amounts of energy and reduce SOx, NOx and OC2-emissions. F every kw of electricity used in the heat pumps, 3 kw can be transferred to thermal energy to be supplied to a district heating system. In Gothenburg, for instance, about 25 of the energy for district heating is recovered from the wastewater. There may be some practical problems encountered when the wastewater is not extensively pre-treated ahead of the heat pump. However, in a scenario where more extensive treatment can be foreseen as a result of the need to reuse water this is not a serious problem. Such energy reclamation is clearly economically and environmentally feasible and the matter should therefore be more focused in the future Production of biogas There is a long tradition of producing biogas by digestion in the wastewater treatment business, but reduction of sludge mass as well as stabilisation of sludge has been the main objective. Today biogas production is very worthwhile also from an energy and sustainability perspective. The total energy potential from the biogas corresponds to about 2, 1 kWh/kg DS of a typical wastewater sludge. This corresponds to about 75 GWh/year in a city of 1 million inhabitants or 15 TWh for the whole of EUs sludge production. Of this energy potential about 1/3 can be recovered as electrici while and about as recoverable heat out of which about 1/6 (of the total)will have to be used for heating the digester. It is evident that the biogas that can be produced from wastewater sludge represents an enormous energy potential and that this potential should be utilised even if the sludge is to be incinerated Production of excess heat from incinerators The raw wastewater sludge has an effective heat value of about 14 MJ/kg DS (3, 85 kWh/kgDS)and digested sludge about 12 MJ/kgDS (3, 3 kWh/kgDS). Even though anaerobic digestion reduces the mount of sludge and therefore the recoverable heat from incineration, the energy recoverable from the biogas far more than outweighs this. From a recycling point of view, sludge should be digested therefore, before incinerated. Whether or not one will have an energy surplus from the incineration depends largely on how much water that has to be evaporated (i.e. the DS-content of the sludge to e incinerated ) The sludge dS if incoming sludge has to be above about 20 in order to have a net energy surplus, and this increases drastically with increasing Ds-content. Pre-treatment that increase the ds-content at low energy consumption is consequently favourable

7 EXTRACTING ENERGY FROM WASTEWATER AND WASTEWATER SLUDGE Wastewater is an energy source. The two major energy sources are the heat of the wastewater and the organic material. The main routes by which the energy potential of the wastewater can be utilised, are: • By extracting heat from the wastewater through heat pumps • By producing biogas from the wastewater sludge through anaerobic digestion • By producing excess heat through incineration of dewatered wastewater sludge The wastewater as a heat source The wastewater produced in a city every day is normally cooler in summer and warmer in winter than the outdoor air, making it suitable as a heat source used by heat pumps for heating and cooling. The wastewater of the cities contains enormous quantities of thermal energy. For instance, heat contained in Tokyo’s wastewater is estimated at 39 % of the total waste heat, about 108 GJ (2,7*107 MWh). Using this huge heat source for district heating and cooling in cities by water-source heat pumps can save considerable amounts of energy and reduce SOx, NOx and OC2-emissions. For every kW of electricity used in the heat pumps, 3 kW can be transferred to thermal energy to be supplied to a district heating system. In Gothenburg, for instance, about 25 % of the energy for district heating is recovered from the wastewater. There may be some practical problems encountered when the wastewater is not extensively pre-treated ahead of the heat pump. However, in a scenario where more extensive treatment can be foreseen as a result of the need to reuse water, this is not a serious problem. Such energy reclamation is clearly economically and environmentally feasible and the matter should therefore be more focused in the future. Production of biogas There is a long tradition of producing biogas by digestion in the wastewater treatment business, but reduction of sludge mass as well as stabilisation of sludge has been the main objective. Today biogas production is very worthwhile also from an energy and sustainability perspective. The total energy potential from the biogas corresponds to about 2,1 kWh/kg DS of a typical wastewater sludge. This corresponds to about 75 GWh/year in a city of 1 million inhabitants or 15 TWh for the whole of EU’s sludge production. Of this energy potential about 1/3 can be recovered as electricity while and about ½ as recoverable heat out of which about 1/6 (of the total) will have to be used for heating the digester. It is evident that the biogas that can be produced from wastewater sludge represents an enormous energy potential and that this potential should be utilised even if the sludge is to be incinerated. Production of excess heat from incinerators The raw wastewater sludge has an effective heat value of about 14 MJ/kgDS (3,85 kWh/kgDS) and digested sludge about 12 MJ/kgDS (3,3 kWh/kgDS). Even though anaerobic digestion reduces the amount of sludge and therefore the recoverable heat from incineration, the energy recoverable from the biogas far more than outweighs this. From a recycling point of view, sludge should be digested, therefore, before incinerated. Whether or not one will have an energy surplus from the incineration depends largely on how much water that has to be evaporated (i.e. the DS-content of the sludge to be incinerated). The sludge DS if incoming sludge has to be above about 20 % in order to have a net energy surplus, and this increases drastically with increasing DS-content. Pre-treatment that increase the DS-content at low energy consumption is consequently favourable

CONCLUSIONS Wastewater should be looked at as a resource with its three main resource components: the water itself, the components of the water(primarily nutrients and carbon)and the heat of the water. Utilization of these resources is closely linked to advanced wastewater treatment 2. In a situation where water use is demand driven, the price of water will be high and extensive wastewater treatment to reclaim water may be cost effective 3. The major use of reclaimed wastewater will be for agricultural and landscape irrigation and for urban reuse( dual distribution systems as well as constructed waterways and wetlands) 4. Utilization of the wastewater heat has a great potential for district heating purposes and should be encouraged 5. Even though direct use on farmland may be the most sustainable way of recycling the resources in sludge, the negative public image of"sewage-fertilized""crops, seems to limit this application 6. The energy that can be produced from sludge biogas is very significant and the use of anaerobic sludge treatment should be encouraged 7.Productification of the resources in sludge can be expected -sludge factories will make products such as electricity, heat, biofuel, bio-solids, phosphorous, ammonium etc REFERENCES Asano, T(ed)(1998)Wastewater reclamation and reuse. Water Quality Management Libraray Vol 10. Technomic Publishing Company, Inc, Lancaster, Pe enn Bouwer, H (1993) From sewage farm to zero discharge. Journ. Eur. Water Poll. Control 3, 9-16 Campbell H W(1989). Status Report on Oil from Sludge Technology in Dirkswagen A H and L'Hermite P(eds): Sewerage Sludge Treatment and Use, Technological Aspects and Environmental. Effects Elsevier Applied Science Cassidy S(1998). Recovery of Valuable Products from Municipal Sewage Sludge. In Hahn HH Hoffmann,E and Odegaard, H (eds): Chemical Water and Wastewater Treatment. Springer Verlag, pp 325-340 Harhoff, J and van der merwe, B(1996) Twenty years of wastewater reclamation in Windhoek, amibia, War. Sci Tech. 33, No 10-11, pp. 25- Matthews P (1996)A Global Atlas of Wastewater Sludge and Biosolids Use and Disposal. IAWQ Scientific and Technical Report No 4, pp 129-132 Mujeriego, R and Asano, T (1999) The role of advanced treatment in wastewater reclamation and reuse. Wat. Sci. Tech. 40, No 4-5, pp 1-9 Watanabe, Y,, Tadano, T, Hasegawa, T, Shimanuki, Y and Odegaard, H(2000) Phosphorous recycling from pre-coagulated wastewater sludge. Proc. 9'th International Gothenburg Symposium, Istanbul, 2-4. Oct World Health Organisation(1973) Reuse of effluents: Methods of wastewater treatment and health safeguards. Tech. Bull. Ser:. 51, WHO, Geneva, Switzerland World Health Organisation(1989) Health guidelines for the use of wastewater in agriculture and aquaculture. Tech. Bull. Ser:. 77, WHO, Geneva, Switzerland

8 CONCLUSIONS 1. Wastewater should be looked at as a resource with its three main resource components: the water itself, the components of the water (primarily nutrients and carbon) and the heat of the water. Utilization of these resources is closely linked to advanced wastewater treatment 2. In a situation where water use is demand driven, the price of water will be high and extensive wastewater treatment to reclaim water may be cost effective 3. The major use of reclaimed wastewater will be for agricultural and landscape irrigation and for urban reuse (dual distribution systems as well as constructed waterways and wetlands) 4. Utilization of the wastewater heat has a great potential for district heating purposes and should be encouraged 5. Even though direct use on farmland may be the most sustainable way of recycling the resources in sludge, the negative public image of “sewage-fertilized” crops, seems to limit this application in the future 6. The energy that can be produced from sludge biogas is very significant and the use of anaerobic sludge treatment should be encouraged 7. “Productification” of the resources in sludge can be expected - sludge factories will make products such as electricity, heat, biofuel, bio-solids, phosphorous, ammonium etc REFERENCES Asano, T. (ed) (1998) Wastewater reclamation and reuse. Water Quality Management Libraray – Vol 10. Technomic Publishing Company, Inc., Lancaster, Penn., USA Bouwer, H. (1993) From sewage farm to zero discharge. Journ. Eur. Water Poll. Control 3, 9-16 Campbell H.W. (1989). Status Report on Oil from Sludge Technology in Dirkswagen A.H. and L'Hermite P. (eds): Sewerage Sludge Treatment and Use, Technological Aspects and Environmental. Effects Elsevier Applied Science Cassidy S. (1998). Recovery of Valuable Products from Municipal Sewage Sludge. In Hahn H.H., Hoffmann, E. and Ødegaard, H.(eds): Chemical Water and Wastewater Treatment. Springer Verlag, pp 325-340. Harhoff, J. and van der Merwe, B. (1996) Twenty years of wastewater reclamation in Windhoek, Namibia, Wat. Sci. Tech. 33, No 10-11, pp. 25- Matthews P. (1996) A Global Atlas of Wastewater Sludge and Biosolids Use and Disposal. IAWQ Scientific and Technical Report No 4, pp 129-132. Mujeriego, R. and Asano, T. (1999) The role of advanced treatment in wastewater reclamation and reuse. Wat. Sci. Tech. 40, No 4-5, pp 1-9 Watanabe,Y., Tadano,T., Hasegawa,T., Shimanuki,Y. and Ødegaard,H. (2000) Phosphorous recycling from pre-coagulated wastewater sludge. Proc. 9’th International Gothenburg Symposium, Istanbul, 2.-4. Oct. World Health Organisation (1973) Reuse of effluents: Methods of wastewater treatment and health safeguards. Tech. Bull. Ser. 51,WHO, Geneva, Switzerland World Health Organisation (1989) Health guidelines for the use of wastewater in agriculture and aquaculture. Tech. Bull. Ser. 77,WHO, Geneva, Switzerland

ACHIEVEMENTS AND CHALLENGES IN THE REUSE OF RECLAIMED WATER lujeriego, R. School of Civil Engineering. Universidad Politecnica de Cataluia, Gran Capitan s/n, 08034 Barcelona, Spain. E-mail: rafael. muieriegolaupces INTRODUCTION Wastewater reuse is an essential component of the natural water cycle. Wastewater discharges to natural watercourses and their subsequent dilution with flowing waters have promoted incidental water reuse in downstream points for urban, agricultural and industrial uses. Direct or planned water reuse at a larger scale has a more recent origin, and implies the direct beneficial use of effluents with a variable degree of treatment, after water is transported using a specific distribution system without discharge or dilution in a natural water course The considerable development reached by planned wastewater reuse, particularly in areas with sufficient water resources, has been motivated by the need to expand water supply capacity and to improve wastewater discharges. The increase in drinking water allocations, together with the population growth experienced by numerous urban areas, have resulted in conventional water supply sources being insufficient to respond to current water demands. The increasing distances between new water sources and urban centers the environmental constrains to build new water dams, and the extended drought episodes experienced in some areas have forced numerous ommunities to approach reuse of reclaimed water as an alternative and additional water source for uses that do not require a potable water quality. Furthermore, increasing public health and environmental requirements on coastal and surface water quality, together with restrictions on location of wastewater facilities and levels of wastewater treatment have resulted in reclaimed wastewater becoming an alternative water source, economical and safe both from the public health and environmental points of view The objective of this presentation is to evaluate the achievements reached by wastewater reclamation and reuse over the last few decades, as well as the challenges that is already facing to ecome an essential component of water resources management WATER RECLAMATION AND REUSE The treatment process necessary for a wastewater effluent to reach the quality required for a given use is commonly designated water reclamation. The water produced by such a process is known reclaimed water. The great impact of those words in public perception has resulted in repeated attempts to adopt words with a more positive meaning for public opinion. One of the more significant changes has been the increasing use of the word water, instead of wastewater. Among the current proposals for the processes themselves, repurification and recycling have gained considerable acceptance. Water produced by those processes has been designated repurified and cycled water(Asano, 1991). Asano(2000) has proposed the more symbolic word of" new water for use in Japanese culture

9 ACHIEVEMENTS AND CHALLENGES IN THE REUSE OF RECLAIMED WATER Mujeriego, R. School of Civil Engineering. Universidad Politécnica de Cataluña, Gran Capitán s/n, 08034 Barcelona, Spain. E-mail: rafael.mujeriego@upc.es INTRODUCTION Wastewater reuse is an essential component of the natural water cycle. Wastewater discharges to natural watercourses and their subsequent dilution with flowing waters have promoted incidental water reuse in downstream points for urban, agricultural and industrial uses. Direct or planned water reuse at a larger scale has a more recent origin, and implies the direct beneficial use of effluents, with a variable degree of treatment, after water is transported using a specific distribution system, without discharge or dilution in a natural water course. The considerable development reached by planned wastewater reuse, particularly in areas with sufficient water resources, has been motivated by the need to expand water supply capacity and to improve wastewater discharges. The increase in drinking water allocations, together with the population growth experienced by numerous urban areas, have resulted in conventional water supply sources being insufficient to respond to current water demands. The increasing distances between new water sources and urban centers, the environmental constrains to build new water dams, and the extended drought episodes experienced in some areas have forced numerous communities to approach reuse of reclaimed water as an alternative and additional water source for uses that do not require a potable water quality. Furthermore, increasing public health and environmental requirements on coastal and surface water quality, together with restrictions on location of wastewater facilities and levels of wastewater treatment, have resulted in reclaimed wastewater becoming an alternative water source, economical and safe both from the public health and environmental points of view. The objective of this presentation is to evaluate the achievements reached by wastewater reclamation and reuse over the last few decades, as well as the challenges that is already facing to become an essential component of water resources management. WATER RECLAMATION AND REUSE The treatment process necessary for a wastewater effluent to reach the quality required for a given use is commonly designated water reclamation. The water produced by such a process is known as reclaimed water. The great impact of those words in public perception has resulted in repeated attempts to adopt words with a more positive meaning for public opinion. One of the more significant changes has been the increasing use of the word water, instead of wastewater. Among the current proposals for the processes themselves, repurification and recycling have gained considerable acceptance. Water produced by those processes has been designated repurified and recycled water (Asano, 1991). Asano (2000) has proposed the more symbolic word of “new water” for use in Japanese culture

10 Implementation of a water reclamation project has two basic and complementary requirements: 1) to define the water quality limits applicable to the beneficial uses considered, and 2)to establish the treatment processes recommended to achieve the above limits. Beneficial use of reclaimed water requires basically: 1)transport of water from the reclamation facility to the point of use, using a dual distribution pipeline or canal system, 2) an storage facility to adjust water supply and water demand, or an alternative discharge permit when there is no need for reclaimed water, and 3)a set of water use requirements, to minimize potential public health and environmental risks BENEFITS OF WATER REUSE Planned water reuse has made considerable advances in water resources management(Mujeriego 1998). The most significant contribution has been the realization that reclaimed water is a significant component of the water cycle, to be taken into account together with other more traditional or conventional tools, such as water savings, rational water use, and water demand management. Reuse of reclaimed water may have one or more of the following benefits 1. An additional contribution of water resources either as net water resources or as alternative water resources that can be used for beneficial uses not requiring drinking water quality, leaving good quality water to be used for urban water supply 2. A reduction on wastewater treatment and disposal costs. Reuse of reclaimed water will offer a clear economical advantage when the quality requirements for reclaimed water are lower than those imposed by water quality standards of the water body receiving wastewater effluents 3. A reduction of pollutant loads to surface water flows, when reuse involves agricultural landscape or forest irrigation. Irrigation with reclaimed water provides an opportunity for organic substances to be degraded through soil biochemical processes into its mineral components, which can be eventually assimilated by plants 4. The reduction, postponement, or even cancellation of new drinking water treatment facilities, with the ensuing positive consequences that it may have on natural water courses and water costs 5. A significant energy saving, while preventing the need for water supplies to be conveyed from areas located much further than the water reclamation facility 6. A beneficial use of nutrients(nitrogen and phosphorous)contained in reclaimed water, when it is used for agricultural and landscape irrigation. Golf course irrigation with reclaimed water may represent up to Euros 18 000 per year, for a regular championship golf cours under southern mediterranean conditions 7. A considerable higher reliability and uniformity of water flows available. Urban wastewater flows are normally much more reliable than the vast majority of rivers and streams in semi arid areas, such as the southern Mediterranean region REQUIREMENTS OF PLANNED WATER REUSE One of the determining factors for the implementation and development of planned water reuse is the establishment of water quality criteria and standards for each of the beneficial uses considered WHO, 1989; USEPA, 1992; WPCF, 1989). Among the numerous substances added to water during its urban, industrial and agricultural use, there are dissolved salts, nutrients, pathogeni microorganisms, inorganic toxic and bio-accumulative substances, and organic micro-pollutants

10 Implementation of a water reclamation project has two basic and complementary requirements: 1) to define the water quality limits applicable to the beneficial uses considered, and 2) to establish the treatment processes recommended to achieve the above limits. Beneficial use of reclaimed water requires basically: 1) transport of water from the reclamation facility to the point of use, using a dual distribution pipeline or canal system, 2) an storage facility to adjust water supply and water demand, or an alternative discharge permit when there is no need for reclaimed water, and 3) a set of water use requirements, to minimize potential public health and environmental risks. BENEFITS OF WATER REUSE Planned water reuse has made considerable advances in water resources management (Mujeriego, 1998). The most significant contribution has been the realization that reclaimed water is a significant component of the water cycle, to be taken into account together with other more traditional or conventional tools, such as water savings, rational water use, and water demand management. Reuse of reclaimed water may have one or more of the following benefits: 1. An additional contribution of water resources, either as net water resources or as alternative water resources that can be used for beneficial uses not requiring drinking water quality, leaving good quality water to be used for urban water supply. 2. A reduction on wastewater treatment and disposal costs. Reuse of reclaimed water will offer a clear economical advantage when the quality requirements for reclaimed water are lower than those imposed by water quality standards of the water body receiving wastewater effluents. 3. A reduction of pollutant loads to surface water flows, when reuse involves agricultural, landscape or forest irrigation. Irrigation with reclaimed water provides an opportunity for organic substances to be degraded through soil biochemical processes into its mineral components, which can be eventually assimilated by plants. 4. The reduction, postponement, or even cancellation of new drinking water treatment facilities, with the ensuing positive consequences that it may have on natural water courses and water costs. 5. A significant energy saving, while preventing the need for water supplies to be conveyed from areas located much further than the water reclamation facility. 6. A beneficial use of nutrients (nitrogen and phosphorous) contained in reclaimed water, when it is used for agricultural and landscape irrigation. Golf course irrigation with reclaimed water may represent up to Euros 18 000 per year, for a regular championship golf course under southern Mediterranean conditions. 7. A considerable higher reliability and uniformity of water flows available. Urban wastewater flows are normally much more reliable than the vast majority of rivers and streams in semi arid areas, such as the southern Mediterranean region. REQUIREMENTS OF PLANNED WATER REUSE One of the determining factors for the implementation and development of planned water reuse is the establishment of water quality criteria and standards for each of the beneficial uses considered (WHO, 1989; USEPA, 1992; WPCF, 1989). Among the numerous substances added to water during its urban, industrial and agricultural use, there are dissolved salts, nutrients, pathogenic microorganisms, inorganic toxic and bio-accumulative substances, and organic micro-pollutants

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西安建筑科技大学：《水资源利用与保护》参考资料_Wastewater as a resource_Wastewater as a resource - EuroCase Paris