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A set of indicators for the assessment of temporal variations in the sustainability of sanitary systems
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Waf. 5, PP. Waf. Sci. Sci. Tech. Tech. Vol. Vol. 39, 39, No. No.5, pp. 235-242, 235-242, 1999 1999 Q LAWQ © 1999 19991AWQ Published Published by by Elsevier Elsevier Science Science Ltd Ltd Printed Printed in in Great Great Britain. Britain. All All rights rights reserved reserved 0273-1223/99 0273-1223/99 $19.00 $19.00 ++ 0.00 0.00
PII: PI!: SO273-1223(99)00107-9 S0273-1223(99)00107-9
A A SET SET OF OF INDICATORS INDICATORS FOR FOR THE THE ASSESSMENT ASSESSMENT OF TEMPORAL TEMPORAL VARIATIONS VARIATIONS IN IN THE THE SUSTAINABILITY SUSTAINABILITY OF SANITARY SANITARY SYSTEMS SYSTEMS M. M. Lundin, Lundin, S. S. Molander Molander and and G. G. M. M. Morrison Morrison Technical Environmental Chalmers University Technology, Technical Environmental Planning, Planning, Chalmers University of oj Technology, S-412 S-412 96 96 Giiteborg, Goteborg, Sweden Sweden
ABSTRACT ABSTRACT The of an an urban studied by application of of aa set set of indicators that that focuses focuses on on The sustainability sustainability of urban water water system system was was studied by application of indicators environmental issues and the efficiency and performance of of the the technical technical system. system. Temporal of environmental issues and the efficiency and performance Temporal variations variations of indicators freshwater resources, drinking water, were investigated for indicators reflecting reflecting freshwater resources, drinking water, wastewater wastewater and and by-products, by-products, were investigated for the water water and and wastewater wastewater system system in Extended time time series series of of precise for precise data data were were available available for the in Goteborg. GOteborg. Extended quantitative indicators such as as water consumption, energy energy use use and and discharge discharge loadings. Qualitative indicators indicators quantitative indicators such water consumption, loadings. Qualitative such as drinking sewage sludge quality and ecosystem status status were were more diffkult to assess, aa such as drinking water water quality, quality, sewage sludge quality and ecosystem more difficult to assess, situation criteria set set in in different Although large large urban systems situation complicated complicated by by variations variations in in criteria different countries. countries. Although urban water water systems are often often considered unsustainable, the the set set of of indicators indicators demonstrate demonstrate that that the the water water and and wastewater wastewater system system in in are considered unsustainable, Giiteborg has moved moved towards towards aa more more sustainable status; recycling recycling of of nutrients nutrients to to agriculture agriculture remains, remains, though, though, Goteborg has sustainable status; aa major major concern. 0 1999 1999 IAWQ IAWQ Published Elsevier Science Science Ltd. Ltd. All All rights rights reserved reserved concern. © Published by by Elsevier KEYWORDS KEYWORDS
Indicators; sustainability; sustainability; water water and and wastewater wastewater system. system. Indicators; INTRODUCTION INTRODUCTION There is is an an increasing increasing emphasis emphasis on on defining defining and and measuring measuring the the sustainability sustainability of of service service systems. systems. However, However, aa There scientific approach to define the sustainability of service systems, which is both complete and unambiguous, scientific approach to define the sustainability of service systems, which is both complete and unambiguous, is lacking. The sustainability of urban water systems can be addressed through a systems approach, where is lacking. The sustainability of urban water systems can be addressed through a systems approach, where not only the sanitary system itself but also households, industry and agriculture are included. The urban not only the sanitary system itself but also households, industry and agriculture are included. The urban water system should be seen as consisting not only of the material technical systems, with installations such water system should be seen as consisting not only of the material technical systems, with installations such as pipes, pumps and buildings but also integrated human activities, as a means to fullil basic human needs. as pipes, pumps and buildings but also integrated human activities, as a means to fulfil basic human needs. The user of the system should thus be included as an important part of the analysis as well as the The user of the system should thus be included as an important part of the analysis as well as the organisation and technical functions needed to build, operate and maintain the production and transport of organisation and technical functions needed to build, operate and maintain the production and transport of drinking water and collection and treatment of wastewater. The whole hydrological cycle provides a natural, drinking water and collection and treatment of wastewater. The whole hydrological cycle provides a natural, if somewhat large boundary, for the urban water system. The system boundaries should also include if somewhat large boundary, for the urban water system. The system boundaries should also include catchment areas, water reserves, receiving waters and the use of nutrients, energy or other products from the catchment areas, water reserves, receiving waters and the use of nutrients, energy or other products from the treatment processes or chemical additives used in the treatment processes. The issue of a sustainable urban sustainable urban treatment processes chemical additives used in the treatment processes. issue of water system raises or difficult questions concerning choice of technology andThe conflicts of ainterests or values. water system raises difficult questions concerning choice of technology and conflicts of interests or values. There is also a need to develop and discuss criteria for sustainability, and indicators relevant to monitoring There is also a need to develop discuss criteria systems. for sustainability, and indicators to monitoring and developing sustainable waterandand wastewater The following definition relevant is employed here: A and developing sustainable water and wastewater systems. The following definition is employed here: A 235
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M. LUNDIN LUNDIN et et al. al. M.
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sustainable sustainable urban urban water water system system should should not not have have negative negative environmental environmental effects effects even even over over a long long time time perspective, perspective, while while providing providing required required services, services, protecting protecting human human health health and and the the environment environment with with aa minimum minimum of of scarce scarce resource resource use use (Lundin (Lundin et et al., ai., 1997). 1997). mEvaluatin~ the the sm sustainability of Sanitary svstem systems An An evaluation evaluation of of the the sustainability sustainability of of different different water water and and wastewater wastewater systems systems involves involves an an interpretative interpretative approach approach that that includes includes environmental, environmental, social social and and economic economic dimensions. dimensions. Promising Promising methods methods for for gaining gaining information information of of environment environment performance performance include include Life Life Cycle Cycle Assessment Assessment (Tillman (Tillman et et al., at., 1998; 1998; Bengtsson Bengtsson et et al., ai., 1997), 1997), energy energy balances balances and and mass mass flow flow analysis analysis (Hellstrom (Hellstrom and and Karrman, Karrman, 1997). 1997). These These approaches approaches tend tend to indicators of to give give aa rather rather limited limited or or one-sided one-sided assessment assessment of of sanitary sanitary systems. systems. Scientifically Scientifically based based indicators of sustainability sustainability have have recently recently been been developed developed (e.g. (e.g. Carlson Carlson et et al., ai., 1996). 1996). AA comparison comparison of of different different indicators indicators and to and approaches approaches can can be be found found inin Azar Azar et et al. ai. (1996). (1996). An An attempt attempt to to link link data data on on material material and and energy energy flows flows.to social proposed aa set social and and economic economic considerations considerations was was made made by by Nilsson Nilsson and and Bergstrom Bergstrom (1995). (1995). They They proposed set of of socio-ecological al. (1997) (1997) socio-ecological indicators indicators which which was was applied applied to to five five sewage sewage plants plants of of different different sizes. sizes. Lundin Lundin et et ai. proposed environmental issues proposed a set set of of indicators indicators focusing focusing on on environmental issues and and the the efficiency efficiency of of the the technical technical system, including including water water resources, resources, drinking drinking water water production production and and distribution, distribution, collection collection and and treatment treatment of of wastewater wastewater and and nutrient nutrient recycling. recycling. The indicators by limited case study of of the water of this this paper paper is is to to test test the the proposed proposed indicators by performing performing aa limited case study the water The purpose purpose of and paper focuses temporal variations variations within within of Gliteborg. Goteborg. This This paper focuses on on temporal and wastewater wastewater system system in in the the municipality municipality of one sanitary system. system. Spatial Spatial comparisons one sanitary comparisons will will be be addressed addressed elsewhere. elsewhere. SELECTION SELECTION OF OF INDICATORS INDICATORS Within the water and wastewater sector aa range of economic economic and and environmental environmental quality quality indicators indicators have have been been Within the water and wastewater sector range of used for decades evaluate the systems. Examples such performance are leakage leakage and and water water used for decades to to evaluate the systems. Examples of of such performance indicators indicators are efficiency These aspects often coincide environmental concerns. concerns. efficiency (OFWAT, (OFWAT, 1997). 1997). These aspects often coincide with with environmental AA limited which covers aspects of of sustainability sustainability should should be be applicable applicable to to aa limited set set of of indicators indicators which covers fundamental fundamental aspects broad of different systems, covering (large scale-small scale-small scale), scale), degree degree of of technological technological broad range range of different systems, covering variety variety in in size size (large development and types types of of treatment. Here the the choice choice of of indicators indicators was was guided guided by by the the following following criteria: criteria: treatment. Here development and their ability to to demonstrate demonstrate aa move move towards towards or or away away from from sustainability sustainability their ability their applicability applicability to broad range of sanitary sanitary systems systems of of different different sizes sizes and and types types of of technological technological their to aa broad range of development development their ability ability to to provide provide an an early early warning warning of of potential potential problems problems •l their . availability of data of sufftcient quality and quantity to provide spatial and temporal trends • availability of data of sufficient quality and quantity to provide spatial and temporal trends . their comprehensiveness; to facilitate involvement from the technical and administrative staff as well as • their comprehensiveness; to facilitate involvement from the technical and administrative staff as well as the community community the 0 their cost-effectiveness • their cost-effectiveness •l . •
In Table Table I1 aa list list is is presented presented with with 19 19 indicators indicators which which are are intended intended to to In technical/environmental aspects of the sustainability of the system. Reasoning technical/environmental aspects of the sustainability of the system. Reasoning indicators has been presented elsewhere (Ltmdin et al., 1997). indicators has been presented elsewhere (Lundin et ai., 1997).
give an an overview overview of of the the give behind the selection of the behind the selection of the
CASE STUDY CASE STUDY Goteborg, situated situated on on the the west west coast coast of of Sweden Sweden is is the the second second largest largest municipality municipality in in Sweden. Sweden. Population Population Goteborg, growth in Goteborg was linear from 1945 to 1970 after which growth stagnated at approximately 450,000 growth in Goteborg was linear from 1945 to 1970 after which growth stagnated at approximately 450,000 persons within within an an area area of of 450 450 km km2. region includes 10 smaller municipalities and has a total 2 The Goteborg persons • The Goteborg region includes 10 smaller municipalities and has a total population of 780 000. Two municipal companies are responsible for water management. Giiteborg water population of 780 000. Two municipal companies are responsible for water management. Goteborg water and sewage works (VA-verket) operates the water works and the pipe network for both water and and sewage works (VA-verket) operates the water works and the pipe network for both water and wastewater. The Rya wastewater treatment plant (WWTP) is operated by the Goteborg Regional Sewage wastewater. The Rya wastewater treatment plant (WWTP) is operated by the Goteborg Regional Sewage Works (GRYAAB). The WWTP receives wastewater from 573,000 inhabitants excluding industry. Works (GRYAAB). The WWTP receives wastewater from 573,000 inhabitants excluding industry.
Assessment Assessment of of temporal temporal variations variations in in sustainability sustainability of of sanitary sanitary systems systems
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Table 1. Proposed indicators of systems Table 1. Proposed indicators of sustainability sustainability for for urban urban water water systems Environmental Environmental -Technical systems Technical systems Freshwater Freshwater resources resources
Dimension Dimension
Example indicators Example indicators
Withdrawal Withdrawal
Annual /annual available Annual freshwater freshwater withdrawal withdrawal/annual available volume volume Phosphorus (pgl-‘) Phosphorus (l1gr')
Water Water quality quality Drinking Drinking water water
Wastewater
By-products By-products
Protection Protection Water Water consumption consumption
Use capita per Use per per capita per day day (lp-‘d’) (lp"d")
Treatment Treatment Distribution Distribution
Degree of of treatment Degree treatment required required Leakage (unaccounted %) Leakage (unaccounted water/produced water/produced water, water, %)
Distance Distance Quality Quality
Distance from Distance from water water source source or or treatment treatment facility facility Coliforms count Coliforms count
Reuse of water water Reuse of Production Production
Reused water Reused water I/ Water Water consumption consumption Wastewater production Wastewater production per per day day
Treatment Treatment performance performance Loadings Loadings to to receiving receiving water water
Removal of BODr, P, of BODs, P, N N (%) (%) Removal Loadings of BODr, P and Loadings of BODs, P and N N
Resource Resource use use Energy use Energy use
Chemical use Chemical use per per P P removed removed Energy use per BODs and N removed Energy use per BODs and N removed Amount of sludge disposed or reused (%) reused (%) Amount of sludge disposed or
Sludge use Sludge use Recycling Recycling of of nutrients nutrients Quality of sludge Quality of sludge Energy recovery Energy recovery Transportation Transportation
Water sources Water sources protected protected
P and and N P N recycled recycled Cadmium content in sludge (kg) Cadmium content in sludge (kg) Energy recovered, heating and power (GWh) Energy recovered, heating and power (GWh) Transportation needed to spread nutrients Transportation needed to spread nutrients
Raw water quality data were collected from the Gota Alv Water Conservation Committee (Gota iilvs Raw water quality data were collected from the Gota Xlv Water Conservation Committee (Gota iilvs vattenvardsfdrbund, 1996), river quality has been monitored since 1958. Drinking water quality, usage, vattenvardsforbund, 1996), river quality has been monitored since 1958. Drinking water quality, usage, leakage, energy and chemical annual report is reported reported by by VA-verket VA-verket and and published published in in their their annual report (VA-verket, (VA-verket, leakage, energy and chemical use use is 1990 and 1996). Data on wastewater content and flow, sludge use and quality, energy demand and recovery 1990 and 1996). Data on wastewater content and flow, sludge use and quality, energy demand and recovery is reported by GRYAAR and published annually (GRYAAB 1972-1996). Data on energy supplied to the is reported by GRYAAB and published annually (GRYAAB 1972-1996). Data on energy supplied to the district heating net were provided by Goteborg Energy. district heating net were provided by Goteborg Energy. Freshwater resources
The municipality of Giiteborg depends on the GSta Alv river as a water source. The river has two The municipality of Goteborg depends on the Gota Xlv river as a water source. The river has two advantages, its proximity and its high water flow (300-900 m3s-‘). Total withdrawal is 7.5 mJi’ including advantages, its proximity and its high water flow (300-900 m3s' I ). Total withdrawal is 7.5 m3s· 1 including four municipalities and fifieen industries (process and cooling water) which corresponds to 1.5% of the four municipalities and fifteen industries (process and cooling water) which corresponds to 1.5% of the average flow. The industrial and municipal wastewater is returned to the river after treatment. The river also average flow. The industrial and municipal wastewater is returned to the river after treatment. The river also receives stormwater and combined sewer overflows. receives stormwater and combined sewer overflows.
FlQhdruwal. The demand for produced drinking water increased by more than three times in Gijteborg Withdrawal. The demand drinkingincreased water increased by more than threeTotal timeswater in Goteborg during the period 1945-70 for whileproduced the population from 306,000 to 450,000. use was during the period 1945-70 while the population increased from 306,000 to 450,000. Total water use was highest in the early 1970s around 2.2 m3sM’. Presently the city of GiXeborg uses 2 m3sM’ water to produce 1 1 highestforinindustrial the earlyand 1970s, arounduse. 2.2 m3 s· • Presently the city of GOteborg uses 2 m3 s· water to produce water municipal water for industrial and municipal use.
Raw water qunlity. Since 1957 the control of river water quality has been co-ordinated by the Gota Alv Raw quality. Since 1957 the control of system river water quality has been co-ordinated GotaIf Xlv Waterwater Conservation Committee. A monitoring is used to secure the quality of the by raw the water. the Water Conservation Committee. A monitoring system is used to secure the quality of the raw water. the quality of the water changes (e.g. by an accident) the intake of water ceases and water is taken fromIf the quality of the water changes (e.g. by an accident) the intake of water ceases and water is taken from the reserve which consists of a series of lakes. The most common raw water quality problems are bacteria, of a and series of lakes. The most common raw water quality problems are bacteria, reserve substances, which consists organic oil spills saltwater intrusion. organic substances, oil spills and saltwater intrusion.
238 238
M. LUNDIN LUNDIN et et al. al. M.
During During the the 20th 20th century century the the Gota Gota Alv Alv river river has has been been subjected subjected to to significant significant environmental environmental impact. impact. In the the early early 1970’s 1970's the the river river was was so so polluted polluted that that the the choice choice of of another another source source of of drinking drinking water water was was investigated. investigated. Since Since then then the the quality quality of of the the river river water water has has improved improved significantly significantly following following the the introduction introduction of of treatment treatment plants of plants for for municipal municipal and and industrial industrial sewage sewage equipped equipped with with biological biological and and chemical chemical treatment. treatment. Loadings Loadings of phosphorus phosphorus and and nitrogen nitrogen to to the the river river depend depend to to a high high degree degree on on the the quality quality of of lake lake Vanem Vlinem (Gota (G
Consumption.As the demand demand for for water water usually usually increases increases for for households and Consumption. As development development increases increases the households and industrial purposes. In Giiteborg water consumption per person (including industry) increased from 170 to industrial purposes. In GOteborg water consumption per person (including industry) increased from 170 to 410 lp-‘d-’ 1 between 1945 and and 1970 1970 (Figure made in as well in most most Swedish Swedish between 1945 (Figure 1). I). Prognoses Prognoses made in Giiteborg Goteborg as well in 410 Ip·ld· municipalities believed an an increased increased future installations were were extended extended accordingly. accordingly. municipalities believed future consumption consumption and and installations However, in 1970 consumption stagnated. During the last 10 years the trend has been declining However, in 1970 consumption stagnated. During the last 10 years the trend has been aa declining consumption and and was was 360 360 Ip·ld· lp-‘d’ 1 in 1996, with with household household use use corresponding corresponding to to 190 190 Ip·ld·l. lp-‘de’. Reasons Reasons for for in 1996, consumption stagnation are coupled to cessation of population growth and increased water prices. stagnation are coupled to cessation of population growth and increased water prices. 500 5 00,..-----------------, 400
400 300
300 200
200 100
100 0
I=__
··--··1000
inhabitants
I -, d· 1
1
I
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O\----+------------~ 1970 1980 1990 1 0 1950 1960 1940 1950 1960 1970 1980 1990 2000
Figure 1, Inhabitants in Giiteborg and drink%zwater consumption in litres per person and day (including Figure I. Inhabitants in Gliteborg and drink~g\vater consumption in litres per person and day (including households, industry and leakage), 19451996. households, industry and leakage), 1945-1996.
Treatment.Drinking Drinking water water treatment treatment consists consists of of disinfection, disinfection, chemical chemical precipitation, precipitation, sand sand filtration filtration and and Treatment. activated carbon adsorption; pH and alkalinity of the water are adjusted to protect iron pipes from corrosion. activated carbon adsorption; pH and alkalinity of the water are adjusted to protect iron pipes from corrosion. In 1996, 1996, 77 800 800 tons tons of of chemicals chemicals was was used. used. The The water water company company isis striving striving to to reduce reduce its its use use of of chlorine chlorine and and In during the past twenty years the addition of chlorine has decreased from 140 to 60 tons per year. Energy during the past twenty years the addition of chlorine has decreased from 140 to 60 tons per year. Energy demand is dominated by electricity which is mainly used for distributing drinking water. In 1996, 40 GWh demand is dominated by electricity which is mainly used for distributing drinking water. In 1996,40 GWh of electricity was used, 10 GWh for treatment and 30 GWh for pumping. No trend in energy use was of electricity was used, 10 GWh for treatment and 30 GWh for pumping. No trend in energy use was detected over the last decade. However, decreased water use and losses together with more efficient detected over the last decade. However, decreased water use and losses together with more efficient pumping devices should have a positive effect on energy and chemical use. pumping devices should have a positive effect on energy and chemical use.
Assessment of of temporal temporal variations variations in in sustainability sustainability of of sanitary sanitary systems systems Assessment
239 239
Drinking water water quality quality depends depends to aahigh highdegree degreeon onthe thesource, source,the theGota G&aAlv Alv river. river. Since Sinceraw rawwater waterquality quality Drinking to hasimproved improvedduring duringthe thelast last20 20 to to 25 25years, years,chemical chemicaland andmicrobiological microbiologicalparameters parameters arebelow belowthe thelimits limits has are setby by the theNational NationalSwedish SwedishFood FoodAdministration. Administration. set Leakage. Substantial Substantialamounts amountsof drinking drinkingwater waterare arelost lostdue dueto to ageing ageingdelivery delivery systems. systems. In Goteborg Giiteborgthere there Leakage. In areabout about1700 1700Ian km of of water waterpipelines. pipelines.The Thedrinking drinkingwater waternetwork networkconsists consists mainlyof of iron iron(approximately (approximately are mainly 75%).Water Waterlost lostin in the thedistribution distributionnetworks networkscan canbe bedefined definedin in several severalways; ways;leakage leakageas aslitres litresof of water waterlost lost 75%). per minute minuteand andkilometre kilometreof of pipe pipe or or per per person personand andday, day, or or as asaa percentage percentageof of sold soldwater watercompared comparedto to per producedwater water (Table (Table2). 2). During During the the past past15 15 years yearsleakage leakagehas hasdecreased, decreased, but is is still still around around20% 20% of of produced but produceddrinking drinkingwater. water.During Duringthe thesame sameperiod periodthe thedistribution distributionnet nethas hasbeen beenextended extendedby by 200 200Ian. km. produced
Table2. 2. Length Lengthofwater of waterpipes pipesin in Goteborg Giiteborgand andaverage averageleakage leakagerates ratesfor for selected selected years,1980-1995. 1980-1995. years, Table Year Year 1980 1980 1985 1985 1990 1990 1995 1995
Water mains, mains, Water km km 1497 1497 1522 1522 1602 1602 1707 1707
Water mains, mains, Water mp,l mp-’ 3.6 3.6 3.7 3.7 3.8 3.8 3.9 3.9
Leakage Leakage j&)-‘m.l !min,lm,1 20 20 22 22 16 16 13 13
Leakage, Leakage, 1 4&l Ip"d,1 103 103 119 119 87 87 73 73
Leakage, Leakage, % % 24 24 26 26 22 22 18 18
Thirty years challengefor for the systemin in Goteborg Goteborgwas the delivery delivery capacity capacityand andquantity. quantity. Thirty years ago ago the the challenge the water water system was the Trends for consumption indicate that water use is now in fact declining. Today the emphasis is on on aa Trends for consumption indicate that water use is now in fact declining. Today the emphasis is continuedsupply supplyof of aa good goodquality water.However, However,much muchof of the theinformation informationon on quality quality is is related related continued quality drinking drinking water. to process performance.There is a needto to develop developindicators indicatorsthat that reflect reflect drinking drinkingwater watercorrosion corrosionpotential potential to process performance. There is a need or human health risk at tap. Consumption, treatment, leakage and resource use are all indicators that are are or human health risk at tap. Consumption, treatment, leakage and resource use are all indicators that related temporaldata data are are readily at least for the the major major systems. systems.Chemical Chemicaland and energy energyuse use related and and temporal readily available, available, at least for dependon on consumption consumption and alsoon quality and anddistance. distance.Leakage Leakagemay difficult to to depend and leakage leakage but but also on raw raw water water quality may be be difficult interpret in terms of sustainability, although on the other hand it is valuable in system comparison. interpret in terms of sustainability, although on the other hand it is valuable in system comparison. Wastewater
The asreceiving wastewaterand The The Rya Rya WWTP WWTP serves serves 573,000 573,000 persons persons as as well well as receiving industrial industrial wastewater and stormwater. stormwater. The l) corresponds industrial lp-‘de’) corresponds to 200,000 200,000p.e. p.e. industrial water water load load calculated calculated as as specific specific household household consumption consumption (190 (190 lp·ld· to Wastewater production. alsoto high degree degreeon on Wastewater production. Wastewater Wastewater production production depends depends on on consumption consumption but but also to aa high leakage into sewage pipes. Almost one quarter of the WWTP catchment has combined sewers. For the last leakage into sewage pipes. Almost one quarter of the WWTP catchment has combined sewers. For the last 20 WWTP has between100 100and year Mmyl. In In aa normal normal year 20 years years wastewater wastewater flow flow entering entering the the Rya Rya WWTP has been been between and 136 136 Mm3y“. about about one one half half of of the the influent influent water water consists consists of of surface surface water, water, drain drain water water and and groundwater groundwater which which have have leaked leaked into into the the sewer sewer system. system. Treatment the Gota Giita Alv of nutrients nutrients to to the Alv Treatment perjbrmance. performance. The The Rya Rya WWTP WWTP has has significantly significantly decreased decreased the the load load of river andcoastalwaters.It wasbuilt in 1972asa highly loadedactivatedsludgeplant with no presettling.As river and coastal waters. It was built in 1972 as a highly loaded activated sludge plant with no presettling. As Figure 2 shows,the treatmentprocesswas over-loadedin the first three years while householdswere Figure 2 shows, the treatment process was over-loaded in the first three years while households were connectedto the plant. Since 1976the removalof BOD and phosphorus has increasedsteadily.Primary connected to the plant. Since 1976 the removal of BOD and phosphorus has increased steadily. Primary settlementand Rtrther aerationwere addedin 1982with chemicalprecipitationintroducedin 1984,thus settlement and further aeration were added in 1982 with chemical precipitation introduced in 1984, thus improving the efftciency of phosphorusand BOD removal. The removal of nitrogen has been less improving the efficiency of phosphorus and BOD removal. The removal of nitrogen has been less successful, between20 and30%, giving emissions of about2000tonsof nitrogena year. The total nitrogen successful, between 20 and 30%, giving emissions of about 2000 tons of nitrogen a year. The total nitrogen transport by the G&a Alv river is in the range of 10,000 to 16,000 tons per year (Gbta Llvs transport by the GOta Alv river is in the range of 10,000 to 16,000 tons per year (Gota lilvs vattenv&lsfirbund, 1996)andcorresponds to half of the total loadfrom Swedento theKattegat.Duringthe vattenvardsfOrbund, 1996) and corresponds to half of the total load from Sweden to the Kattegat. During the lastthreeyearsthe Rya WWTP hasbeenupgradedfor a 50% nitrogenremovalandincreasedcapacityto last three years the Rya WWTP has been upgraded for a 50% nitrogen removal and increased capacity to reduce stormwateroverflows. reduce stormwater overflows.
240 240
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Figure substances (( BOD,), at the Figure 2. 2. Treatment Treatment performance perfonnance (%) (%) of of organic organic substances BOD 7), total total phosphorus phosphorus and and total total nitrogen nitrogen at the Rya Rya WWTP, 1996. WWTP, 1972 1972 to to 1996.
Resource sewagetreatment chemicalsand Resource use. use. The The sewage treatment process process depends depends on on the the inputs inputs of of chemicals and energy. energy. Between Between 6 6 000 000 and 7 000 tons of iron sulphate are used annually for phosphorus removal. In addition chemicals are used for and 7 000 tons of iron sulphate are used annually for phosphorus removal. In addition chemicals are used for disinfection andsludge disinfection and sludge thickening. thickening. No No trend trend in in chemical chemical use use has has been been detected detected over over the the last last decade decade and and the the amount amount of of chemicals chemicals used used per per phosphorus phosphorus removal removal has has been been relatively relatively constant. constant. Energy Energy used used in in the the treatment 10 years years the the use use of of electricity electricity has has been been treatment process process is is dominated dominated by by electricity. electricity. During During the the last last 10 relatively BOD removal relatively stable stable but but since since BOD removal has has improved, improved, the the efficiency efficiency has has increased. increased.
Wastewater is an indicator.If If too too much much water water enters enters the the sewage sewage system system Wastewater production production is an important important sustainability sustainability indicator. the loweredand directly to the effectiveness effectiveness of of the the treatment treatment may may be be lowered and untreated untreated water water could could be be discharged discharged directly to water water bodies. of stormwater, impermeable areas as percentage percentage of stormwater, impermeable areas and and groundwater groundwater infiltration infiltration bodies. Further Further indicators indicators such such as can of detail. Treatmentperformances relatively straightforward detail. Treatment performances are are relatively straightforward indicators indicators can be be used used to to gain gain a a higher higher level level of that reflect the function of the technical systems, an abundance of data exists for those connected connected to to the the that reflect the function of the technical systems, an abundance of data exists for those major systems. Loadings to receiving waters are perhaps more important in terms of sustainability because major systems. Loadings to receiving waters are perhaps more important in terms of sustainability because they they indicate indicate the the total total pressure pressure on on the the receiving receiving waters. waters. Chemical Chemical and and energy energy use use are are other other indicators indicators which which show that achieving high removal to protect the aquatic systems is often at the expense of resources. show that achieving high removal to protect the aquatic systems is often at the expense of resources. By-produd By-products Energy recovery Before 1990sludgetreatmentconsisted of dewateringandcompostingor lime addition.In Energy recovery. Before 1990 sludge treatment consisted of dewatering and composting or lime addition. In 1990sludgetreatmentwas supplemented with digestiontanksandproducedbiogaswas usedto heatthe 1990 sludge treatment was supplemented with digestion tanks and produced biogas was used to heat the plant, excessenergywasutilisedin the districtheatingsystem.In 1994a gasmotorwasinstalledto produce plant, excess energy was utilised in the district heating system. In 1994 a gas motor was installed to produce electricity from biogas,supplyinghalf of the electricity neededfor the operationof the plant (Figure3). In electricity from biogas, supplying half of the electricity needed for the operation of the plant (Figure 3). In additiona smallpart of thebiogasis usedastransportfuel. addition a small part of the biogas is used as transport fuel.
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Figure 3. Electricity demand and production ofplant, electricity and district heating at the Rya wastewater treatment 19751996. plant, 1975-1996.
Since1984the treatedwater passes a heatpump,which recoversheatto the district heatingsystembefore Since 1984 the treated water passes a heat pump, which recovers heat to the district heating system before water is releasedinto the mouthof the Gota iilv river. Between400to 500GWhy-’l is extractedfrom the water is released into the mouth of the G
Assessment Assessment of of temporal temporal variations variations in in sustainability sustainability of ofsanitary sanitary systems systems
241 Sludge use. The Rya WWTP produces around 50 000 tons of sludge per year. The treated sludge is used Sludge use. The Rya WWTP produces around 50 000 tons of sludge per year. The treated sludge is used inin agriculture, agriculture, as as an an urban urban soil soil improver, improver, isis composted composted or or isis used used as as landfill. landfill. The The sludge sludge contains contains most most of of the the phosphorus phosphorus and and part part of of the the nitrogen nitrogen from from the the influent influent wastewater, wastewater, but but also also aa significant significant proportion proportion of of heavy heavy metals. of the the sludge sludge has has been been applied applied in in agriculture agriculture and and in in 1988 1988 metals. During During the the last last 20 20 years years only only aa small small part part of the of sewage sewage sludge sludge (figure (figure 4). 4). The The reason reason given given was was the the high high content content the farmers farmers commenced commenced aa total total boycott boycott of of of heavy heavy metals metals in in sludge. sludge. Quality Quality of of sludge. sludge. Partly Partly because because of of the the farmers fanners boycott, boycott, substantial substantial work work has has been been done done to to decrease decrease the the contamination of heavy metals which may be indicated by the cadmium content (figure 5). contamination of heavy metals which may be indicated by the cadmium content (figure 5).
Figure Figure 4. 4. Percentage Percentage of of sludge sludge that that are are applied applied in in agriculture. agriculture.
Figure 5. Cadmium content in sludge in kg per yearat the Rya WWTF. Figure 5. Cadmium content in sludge in kg per year at the Rya WWTI'. Extensive data exists to provide a clear picture of how energy and sludge is used. The degree of nutrient Extensive data exists to provide a clear picture of how energy and sludge is used. The degree of nutrient recycling estimated ifif data and this be estimated data exists exists for for the the nutrient nutrient content content in in sludge sludge and this indicator indicator recycling from from wastewater wastewater can can be also applies to alternative wastewater systems such as urine sorting. The quality of sludge is well indicated also applies to alternative wastewater systems such as urine sorting. The quality of sludge is well indicated by a number of parameters including heavy metals. by a number of parameters including heavy metals. Concerning energy although substantial amounts of energy are needed for the treatment processes at Rya Concerning energy although substantial amounts of energy are needed for the treatment processes at Rya WWTP, significant amounts are recovered as biogas and heat. The situation is less satisfactory for sewage WWTP, significant amounts are recovered as biogas and heat. The situation is less satisfactory for sewage sludge; presently a minor proportion of the sewage sludge is spread on agricultural land. However sludge; presently a minor proportion of the sewage sludge is spread on agricultural land. However discussions with the farmers have led to a positive debate and sewage sludge is undergoing a quality discussions with the farmers have led to a positive debate and sewage sludge is undergoing a quality certification. The potential for phosphorus recycling is therefore good. Recycling of nitrogen above 20-30% certification. The potential for phosphorus recycling is therefore good. Recycling of nitrogen above 20-30% is however not possible with existing treatment processes. is however not possible with existing treatment processes. DISCUSSION DISCUSSION The establishment of sustainability indicators can provide a procedure for the evaluation of different sanitary The establishment of sustainability indicators can provide a procedure for the evaluation of different sanitary systems as well as the assessment of their progress towards sustainable water management. In this study a systems as well as the assessment of their progress towards sustainable water management. In this study a set of indicators is proposed and the temporal variation of selected indicators is examined for Goteborg. set of were indicators is proposed and were the temporal variationandofgive selected indicators for GOteborg. These selected because they easily available reliable results. isIn examined future research, a wider These were selected because they were easily available and give reliable results. In future research, a wider range of indicators, including socio-economic aspects will be more precisely defined and tested against including socio-economic aspects will be more precisely defined and tested against range criteria offorindicators, sustainability. criteria for sustainability. It seems that reliable data are available for indicators that describe the different technical systems. It seems that reliable data are available for indicators that describe the different technical systems. Interactions between different urban systems and their interaction with surrounding ecosystems are more Interactions between their interaction surrounding ecosystems are water more difficult to assess. As different an exampleurban the systems withdrawalandindicator in table 1with is composed of two parts where two parts water difficult to assess. an example in table volume I is composed withdrawal is well As known to the the waterwithdrawal company indicator while available is less of known. For where quantitative withdrawal is well knownconsumption, to the waterenergy company available reliable volume data is less indicators such as water use while and emissions, areknown. availableForforquantitative long time indicators such as water consumption, energy use and emissions, reliable data are available for long time
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series. Qualitative parameters equally important. series. Qualitative parameters can can be more more difficult difficult to monitor monitor but but can can be equally important. One One way way to handle indicators into handle this this problem problem can can be be to combine combine several several indicators into an index. index. Examples Examples of of such such parameters parameters are drinking drinking water water quality quality or or ecosystem ecosystem status. Drinking and sludge quality are values, related Drinking water, water, wastewater wastewater and sludge quality are usually usually evaluated evaluated against against criteria criteria or or limit limit values, related to criteria vary to some some judgement judgement or or ecological/health ecological/health observation. observation. The The criteria vary in in different different countries countries and and comparisons comparisons are can be with is important important to to recognise recognise the the difference difference between between aa criterion, criterion, which which can be aa directive directive with are complicated. complicated. ItIt is aa scientifically-based scientifically-based judgement, judgement, and and an an indicator, indicator, which which is is one one parameter parameter chosen chosen to to reflect reflect sustainability. sustainability. AA conclusion conclusion that that the that can can be be drawn drawn for for the the Gdteborg Goteborg water water and and wastewater wastewater system system is is that the system system is is moving moving towards towards aa more more sustainable sustainable status. status. Water Water consumption consumption is is decreasing, decreasing, less less drinking drinking water water is is lost lost and and the the quality effkiency of quality of of the the raw raw water water has has improved. improved. The The efficiency of wastewater wastewater treatment treatment has has increased increased as as indicated indicated by by increasing for BOD Recycling of of nutrients nutrients is is increasing removal removal and and less less resource resource use, use, at at least least for BOD and and phosphorus. phosphorus. Recycling however remains aa major however limited limited and and remains major hurdle hurdle for for this this urban urban area. area. REFERENCES REFERENCES Azar, K. (1996). Socio-ecological indicators 18, 89-112. 89-l 12. Azar, C., c., Holmberg, Holmberg, J. J. and and Lindgren Lindgren K. (1996). Socio-ecological indicators for for sustainability. sustainability. Ecol. Ecol. Econ., Econ., 18, Bengtsson, (1997). Life cycle assessment Conventional S. (1997). Life cycle assessment of of wastewater wastewater systems. systems. Case Case stidies studies of of Conventional Bengtsson, M., M., Lundin, Lundin, M. M. and and Molander, Molander, S. Treatment. Urine sorting Three Swedish Technical Treatment. Urine sorting and and Liquid Liquid Cornposting Composting in in Three Swedish Municipalities, Municipalities. Report Report 1997~9, 1997:9, Technical Environmental Environmental Planning, Planning, Chalmers Chalmers University University of of Technology, Technology, Giiteborg, Goteborg, Sweden. Sweden. Carlson, Carlson, U., U., Holmberg, Holmberg, J. J. and and Bemdes, Bemdes, G. G. (1996). (1996). Socio-ecological Socio-ecological indicators indicators for for sustainability sustainability for for Gotland, Gotland. Sweden, Sweden, Institute Institute of of Physical Physical Resource Resource Theory, Theory, Chalmers Chalmers University University of of Technology, Technology, Giiteborg. Goteborg. GRYAAB GRYAAB (1972-1996). (1972-1996). Environmental Environmental reports reports (in (in Swedish). Swedish). Giita Blvs vattenvHrdsfdrbund Swedish). Gota lilvs vattenvardsfOrbund (1996). (1996). Facts Facts on on Giita Gota Blv lilv 1996 1996 (in (in Swedish). Hellstr8m, D. and (1997). Exergy flows of systems. Wat. E. (1997). Exergy analysis analysis and and nutrient nutrient flows of various various sewerage sewerage systems. Wat. Sci. Sci. Tech. Tech. 35(9), 35(9), Hellstrom, D. and K%rrman, Klirrman, E. 135-144. 135-144. Lundin, for the development of Lundin, M., M., Molander, Molander, S. S. and and Morrison, Morrison, G. G. M. M. (1997). (1997). Indicators IndicatoIs for the development of sustainable sustainable water water and and wastewater wastewater systems. Sustainable development research conference, Manchester, April. systems. Sustainable development research conference, Manchester, April. Nilsson, Nilsson, J. J. and and Bergstrijm, Bergstrom, S. S. (1995). (1995). Indicators Indicators for for the the assessment assessment of of ecological ecological and and economic economic consequences consequences of of municipal municipal policies for resource use. Ecol. Econ., 14, 175-184. policies for resource use. Ecol. Econ., 14, 175-184. OFWAT (1997). Report on Leakage and water efficiency, Office of Water Service, Birmingham, UK. OFWAT (1997). Report on Leakage and water efficiency, Office of Water Service, Birmingham, UK. Tillman, A.-M., Lund&ram, H. and Svingby, M. (1998). Life cycle assessment of Municipal Wastewater Systems - A case study. Tillman, A.-M., Lundstrom, H. and Svingby, M. (1998). Life cycle assessment of Municipal Wastewater Systems - A case study. Submitted to the International Journal of Life Cycle Assessment. Submitted to the International Journal ofLife Cycle Assessment. VA-verket (1990). Annual report (in Swedish). VA-verket (1990). Annual report (in Swedish). VA-verket (1996). Annual report (in Swedish). VA-verket (1996). Annual report (in Swedish).
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Waf. 5, PP. Waf. Sci. Sci. Tech. Tech. Vol. Vol. 39, 39, No. No.5, pp. 235-242, 235-242, 1999 1999 Q LAWQ © 1999 19991AWQ Published Published by by Elsevier Elsevier Science Science Ltd Ltd Printed Printed in in Great Great Britain. Britain. All All rights rights reserved reserved 0273-1223/99 0273-1223/99 $19.00 $19.00 ++ 0.00 0.00
PII: PI!: SO273-1223(99)00107-9 S0273-1223(99)00107-9
A A SET SET OF OF INDICATORS INDICATORS FOR FOR THE THE ASSESSMENT ASSESSMENT OF TEMPORAL TEMPORAL VARIATIONS VARIATIONS IN IN THE THE SUSTAINABILITY SUSTAINABILITY OF SANITARY SANITARY SYSTEMS SYSTEMS M. M. Lundin, Lundin, S. S. Molander Molander and and G. G. M. M. Morrison Morrison Technical Environmental Chalmers University Technology, Technical Environmental Planning, Planning, Chalmers University of oj Technology, S-412 S-412 96 96 Giiteborg, Goteborg, Sweden Sweden
ABSTRACT ABSTRACT The of an an urban studied by application of of aa set set of indicators that that focuses focuses on on The sustainability sustainability of urban water water system system was was studied by application of indicators environmental issues and the efficiency and performance of of the the technical technical system. system. Temporal of environmental issues and the efficiency and performance Temporal variations variations of indicators freshwater resources, drinking water, were investigated for indicators reflecting reflecting freshwater resources, drinking water, wastewater wastewater and and by-products, by-products, were investigated for the water water and and wastewater wastewater system system in Extended time time series series of of precise for precise data data were were available available for the in Goteborg. GOteborg. Extended quantitative indicators such as as water consumption, energy energy use use and and discharge discharge loadings. Qualitative indicators indicators quantitative indicators such water consumption, loadings. Qualitative such as drinking sewage sludge quality and ecosystem status status were were more diffkult to assess, aa such as drinking water water quality, quality, sewage sludge quality and ecosystem more difficult to assess, situation criteria set set in in different Although large large urban systems situation complicated complicated by by variations variations in in criteria different countries. countries. Although urban water water systems are often often considered unsustainable, the the set set of of indicators indicators demonstrate demonstrate that that the the water water and and wastewater wastewater system system in in are considered unsustainable, Giiteborg has moved moved towards towards aa more more sustainable status; recycling recycling of of nutrients nutrients to to agriculture agriculture remains, remains, though, though, Goteborg has sustainable status; aa major major concern. 0 1999 1999 IAWQ IAWQ Published Elsevier Science Science Ltd. Ltd. All All rights rights reserved reserved concern. © Published by by Elsevier KEYWORDS KEYWORDS
Indicators; sustainability; sustainability; water water and and wastewater wastewater system. system. Indicators; INTRODUCTION INTRODUCTION There is is an an increasing increasing emphasis emphasis on on defining defining and and measuring measuring the the sustainability sustainability of of service service systems. systems. However, However, aa There scientific approach to define the sustainability of service systems, which is both complete and unambiguous, scientific approach to define the sustainability of service systems, which is both complete and unambiguous, is lacking. The sustainability of urban water systems can be addressed through a systems approach, where is lacking. The sustainability of urban water systems can be addressed through a systems approach, where not only the sanitary system itself but also households, industry and agriculture are included. The urban not only the sanitary system itself but also households, industry and agriculture are included. The urban water system should be seen as consisting not only of the material technical systems, with installations such water system should be seen as consisting not only of the material technical systems, with installations such as pipes, pumps and buildings but also integrated human activities, as a means to fullil basic human needs. as pipes, pumps and buildings but also integrated human activities, as a means to fulfil basic human needs. The user of the system should thus be included as an important part of the analysis as well as the The user of the system should thus be included as an important part of the analysis as well as the organisation and technical functions needed to build, operate and maintain the production and transport of organisation and technical functions needed to build, operate and maintain the production and transport of drinking water and collection and treatment of wastewater. The whole hydrological cycle provides a natural, drinking water and collection and treatment of wastewater. The whole hydrological cycle provides a natural, if somewhat large boundary, for the urban water system. The system boundaries should also include if somewhat large boundary, for the urban water system. The system boundaries should also include catchment areas, water reserves, receiving waters and the use of nutrients, energy or other products from the catchment areas, water reserves, receiving waters and the use of nutrients, energy or other products from the treatment processes or chemical additives used in the treatment processes. The issue of a sustainable urban sustainable urban treatment processes chemical additives used in the treatment processes. issue of water system raises or difficult questions concerning choice of technology andThe conflicts of ainterests or values. water system raises difficult questions concerning choice of technology and conflicts of interests or values. There is also a need to develop and discuss criteria for sustainability, and indicators relevant to monitoring There is also a need to develop discuss criteria systems. for sustainability, and indicators to monitoring and developing sustainable waterandand wastewater The following definition relevant is employed here: A and developing sustainable water and wastewater systems. The following definition is employed here: A 235
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sustainable sustainable urban urban water water system system should should not not have have negative negative environmental environmental effects effects even even over over a long long time time perspective, perspective, while while providing providing required required services, services, protecting protecting human human health health and and the the environment environment with with aa minimum minimum of of scarce scarce resource resource use use (Lundin (Lundin et et al., ai., 1997). 1997). mEvaluatin~ the the sm sustainability of Sanitary svstem systems An An evaluation evaluation of of the the sustainability sustainability of of different different water water and and wastewater wastewater systems systems involves involves an an interpretative interpretative approach approach that that includes includes environmental, environmental, social social and and economic economic dimensions. dimensions. Promising Promising methods methods for for gaining gaining information information of of environment environment performance performance include include Life Life Cycle Cycle Assessment Assessment (Tillman (Tillman et et al., at., 1998; 1998; Bengtsson Bengtsson et et al., ai., 1997), 1997), energy energy balances balances and and mass mass flow flow analysis analysis (Hellstrom (Hellstrom and and Karrman, Karrman, 1997). 1997). These These approaches approaches tend tend to indicators of to give give aa rather rather limited limited or or one-sided one-sided assessment assessment of of sanitary sanitary systems. systems. Scientifically Scientifically based based indicators of sustainability sustainability have have recently recently been been developed developed (e.g. (e.g. Carlson Carlson et et al., ai., 1996). 1996). AA comparison comparison of of different different indicators indicators and to and approaches approaches can can be be found found inin Azar Azar et et al. ai. (1996). (1996). An An attempt attempt to to link link data data on on material material and and energy energy flows flows.to social proposed aa set social and and economic economic considerations considerations was was made made by by Nilsson Nilsson and and Bergstrom Bergstrom (1995). (1995). They They proposed set of of socio-ecological al. (1997) (1997) socio-ecological indicators indicators which which was was applied applied to to five five sewage sewage plants plants of of different different sizes. sizes. Lundin Lundin et et ai. proposed environmental issues proposed a set set of of indicators indicators focusing focusing on on environmental issues and and the the efficiency efficiency of of the the technical technical system, including including water water resources, resources, drinking drinking water water production production and and distribution, distribution, collection collection and and treatment treatment of of wastewater wastewater and and nutrient nutrient recycling. recycling. The indicators by limited case study of of the water of this this paper paper is is to to test test the the proposed proposed indicators by performing performing aa limited case study the water The purpose purpose of and paper focuses temporal variations variations within within of Gliteborg. Goteborg. This This paper focuses on on temporal and wastewater wastewater system system in in the the municipality municipality of one sanitary system. system. Spatial Spatial comparisons one sanitary comparisons will will be be addressed addressed elsewhere. elsewhere. SELECTION SELECTION OF OF INDICATORS INDICATORS Within the water and wastewater sector aa range of economic economic and and environmental environmental quality quality indicators indicators have have been been Within the water and wastewater sector range of used for decades evaluate the systems. Examples such performance are leakage leakage and and water water used for decades to to evaluate the systems. Examples of of such performance indicators indicators are efficiency These aspects often coincide environmental concerns. concerns. efficiency (OFWAT, (OFWAT, 1997). 1997). These aspects often coincide with with environmental AA limited which covers aspects of of sustainability sustainability should should be be applicable applicable to to aa limited set set of of indicators indicators which covers fundamental fundamental aspects broad of different systems, covering (large scale-small scale-small scale), scale), degree degree of of technological technological broad range range of different systems, covering variety variety in in size size (large development and types types of of treatment. Here the the choice choice of of indicators indicators was was guided guided by by the the following following criteria: criteria: treatment. Here development and their ability to to demonstrate demonstrate aa move move towards towards or or away away from from sustainability sustainability their ability their applicability applicability to broad range of sanitary sanitary systems systems of of different different sizes sizes and and types types of of technological technological their to aa broad range of development development their ability ability to to provide provide an an early early warning warning of of potential potential problems problems •l their . availability of data of sufftcient quality and quantity to provide spatial and temporal trends • availability of data of sufficient quality and quantity to provide spatial and temporal trends . their comprehensiveness; to facilitate involvement from the technical and administrative staff as well as • their comprehensiveness; to facilitate involvement from the technical and administrative staff as well as the community community the 0 their cost-effectiveness • their cost-effectiveness •l . •
In Table Table I1 aa list list is is presented presented with with 19 19 indicators indicators which which are are intended intended to to In technical/environmental aspects of the sustainability of the system. Reasoning technical/environmental aspects of the sustainability of the system. Reasoning indicators has been presented elsewhere (Ltmdin et al., 1997). indicators has been presented elsewhere (Lundin et ai., 1997).
give an an overview overview of of the the give behind the selection of the behind the selection of the
CASE STUDY CASE STUDY Goteborg, situated situated on on the the west west coast coast of of Sweden Sweden is is the the second second largest largest municipality municipality in in Sweden. Sweden. Population Population Goteborg, growth in Goteborg was linear from 1945 to 1970 after which growth stagnated at approximately 450,000 growth in Goteborg was linear from 1945 to 1970 after which growth stagnated at approximately 450,000 persons within within an an area area of of 450 450 km km2. region includes 10 smaller municipalities and has a total 2 The Goteborg persons • The Goteborg region includes 10 smaller municipalities and has a total population of 780 000. Two municipal companies are responsible for water management. Giiteborg water population of 780 000. Two municipal companies are responsible for water management. Goteborg water and sewage works (VA-verket) operates the water works and the pipe network for both water and and sewage works (VA-verket) operates the water works and the pipe network for both water and wastewater. The Rya wastewater treatment plant (WWTP) is operated by the Goteborg Regional Sewage wastewater. The Rya wastewater treatment plant (WWTP) is operated by the Goteborg Regional Sewage Works (GRYAAB). The WWTP receives wastewater from 573,000 inhabitants excluding industry. Works (GRYAAB). The WWTP receives wastewater from 573,000 inhabitants excluding industry.
Assessment Assessment of of temporal temporal variations variations in in sustainability sustainability of of sanitary sanitary systems systems
237 237
Table 1. Proposed indicators of systems Table 1. Proposed indicators of sustainability sustainability for for urban urban water water systems Environmental Environmental -Technical systems Technical systems Freshwater Freshwater resources resources
Dimension Dimension
Example indicators Example indicators
Withdrawal Withdrawal
Annual /annual available Annual freshwater freshwater withdrawal withdrawal/annual available volume volume Phosphorus (pgl-‘) Phosphorus (l1gr')
Water Water quality quality Drinking Drinking water water
Wastewater
By-products By-products
Protection Protection Water Water consumption consumption
Use capita per Use per per capita per day day (lp-‘d’) (lp"d")
Treatment Treatment Distribution Distribution
Degree of of treatment Degree treatment required required Leakage (unaccounted %) Leakage (unaccounted water/produced water/produced water, water, %)
Distance Distance Quality Quality
Distance from Distance from water water source source or or treatment treatment facility facility Coliforms count Coliforms count
Reuse of water water Reuse of Production Production
Reused water Reused water I/ Water Water consumption consumption Wastewater production Wastewater production per per day day
Treatment Treatment performance performance Loadings Loadings to to receiving receiving water water
Removal of BODr, P, of BODs, P, N N (%) (%) Removal Loadings of BODr, P and Loadings of BODs, P and N N
Resource Resource use use Energy use Energy use
Chemical use Chemical use per per P P removed removed Energy use per BODs and N removed Energy use per BODs and N removed Amount of sludge disposed or reused (%) reused (%) Amount of sludge disposed or
Sludge use Sludge use Recycling Recycling of of nutrients nutrients Quality of sludge Quality of sludge Energy recovery Energy recovery Transportation Transportation
Water sources Water sources protected protected
P and and N P N recycled recycled Cadmium content in sludge (kg) Cadmium content in sludge (kg) Energy recovered, heating and power (GWh) Energy recovered, heating and power (GWh) Transportation needed to spread nutrients Transportation needed to spread nutrients
Raw water quality data were collected from the Gota Alv Water Conservation Committee (Gota iilvs Raw water quality data were collected from the Gota Xlv Water Conservation Committee (Gota iilvs vattenvardsfdrbund, 1996), river quality has been monitored since 1958. Drinking water quality, usage, vattenvardsforbund, 1996), river quality has been monitored since 1958. Drinking water quality, usage, leakage, energy and chemical annual report is reported reported by by VA-verket VA-verket and and published published in in their their annual report (VA-verket, (VA-verket, leakage, energy and chemical use use is 1990 and 1996). Data on wastewater content and flow, sludge use and quality, energy demand and recovery 1990 and 1996). Data on wastewater content and flow, sludge use and quality, energy demand and recovery is reported by GRYAAR and published annually (GRYAAB 1972-1996). Data on energy supplied to the is reported by GRYAAB and published annually (GRYAAB 1972-1996). Data on energy supplied to the district heating net were provided by Goteborg Energy. district heating net were provided by Goteborg Energy. Freshwater resources
The municipality of Giiteborg depends on the GSta Alv river as a water source. The river has two The municipality of Goteborg depends on the Gota Xlv river as a water source. The river has two advantages, its proximity and its high water flow (300-900 m3s-‘). Total withdrawal is 7.5 mJi’ including advantages, its proximity and its high water flow (300-900 m3s' I ). Total withdrawal is 7.5 m3s· 1 including four municipalities and fifieen industries (process and cooling water) which corresponds to 1.5% of the four municipalities and fifteen industries (process and cooling water) which corresponds to 1.5% of the average flow. The industrial and municipal wastewater is returned to the river after treatment. The river also average flow. The industrial and municipal wastewater is returned to the river after treatment. The river also receives stormwater and combined sewer overflows. receives stormwater and combined sewer overflows.
FlQhdruwal. The demand for produced drinking water increased by more than three times in Gijteborg Withdrawal. The demand drinkingincreased water increased by more than threeTotal timeswater in Goteborg during the period 1945-70 for whileproduced the population from 306,000 to 450,000. use was during the period 1945-70 while the population increased from 306,000 to 450,000. Total water use was highest in the early 1970s around 2.2 m3sM’. Presently the city of GiXeborg uses 2 m3sM’ water to produce 1 1 highestforinindustrial the earlyand 1970s, arounduse. 2.2 m3 s· • Presently the city of GOteborg uses 2 m3 s· water to produce water municipal water for industrial and municipal use.
Raw water qunlity. Since 1957 the control of river water quality has been co-ordinated by the Gota Alv Raw quality. Since 1957 the control of system river water quality has been co-ordinated GotaIf Xlv Waterwater Conservation Committee. A monitoring is used to secure the quality of the by raw the water. the Water Conservation Committee. A monitoring system is used to secure the quality of the raw water. the quality of the water changes (e.g. by an accident) the intake of water ceases and water is taken fromIf the quality of the water changes (e.g. by an accident) the intake of water ceases and water is taken from the reserve which consists of a series of lakes. The most common raw water quality problems are bacteria, of a and series of lakes. The most common raw water quality problems are bacteria, reserve substances, which consists organic oil spills saltwater intrusion. organic substances, oil spills and saltwater intrusion.
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During During the the 20th 20th century century the the Gota Gota Alv Alv river river has has been been subjected subjected to to significant significant environmental environmental impact. impact. In the the early early 1970’s 1970's the the river river was was so so polluted polluted that that the the choice choice of of another another source source of of drinking drinking water water was was investigated. investigated. Since Since then then the the quality quality of of the the river river water water has has improved improved significantly significantly following following the the introduction introduction of of treatment treatment plants of plants for for municipal municipal and and industrial industrial sewage sewage equipped equipped with with biological biological and and chemical chemical treatment. treatment. Loadings Loadings of phosphorus phosphorus and and nitrogen nitrogen to to the the river river depend depend to to a high high degree degree on on the the quality quality of of lake lake Vanem Vlinem (Gota (G
Consumption.As the demand demand for for water water usually usually increases increases for for households and Consumption. As development development increases increases the households and industrial purposes. In Giiteborg water consumption per person (including industry) increased from 170 to industrial purposes. In GOteborg water consumption per person (including industry) increased from 170 to 410 lp-‘d-’ 1 between 1945 and and 1970 1970 (Figure made in as well in most most Swedish Swedish between 1945 (Figure 1). I). Prognoses Prognoses made in Giiteborg Goteborg as well in 410 Ip·ld· municipalities believed an an increased increased future installations were were extended extended accordingly. accordingly. municipalities believed future consumption consumption and and installations However, in 1970 consumption stagnated. During the last 10 years the trend has been declining However, in 1970 consumption stagnated. During the last 10 years the trend has been aa declining consumption and and was was 360 360 Ip·ld· lp-‘d’ 1 in 1996, with with household household use use corresponding corresponding to to 190 190 Ip·ld·l. lp-‘de’. Reasons Reasons for for in 1996, consumption stagnation are coupled to cessation of population growth and increased water prices. stagnation are coupled to cessation of population growth and increased water prices. 500 5 00,..-----------------, 400
400 300
300 200
200 100
100 0
I=__
··--··1000
inhabitants
I -, d· 1
1
I
I
~_~J
O\----+------------~ 1970 1980 1990 1 0 1950 1960 1940 1950 1960 1970 1980 1990 2000
Figure 1, Inhabitants in Giiteborg and drink%zwater consumption in litres per person and day (including Figure I. Inhabitants in Gliteborg and drink~g\vater consumption in litres per person and day (including households, industry and leakage), 19451996. households, industry and leakage), 1945-1996.
Treatment.Drinking Drinking water water treatment treatment consists consists of of disinfection, disinfection, chemical chemical precipitation, precipitation, sand sand filtration filtration and and Treatment. activated carbon adsorption; pH and alkalinity of the water are adjusted to protect iron pipes from corrosion. activated carbon adsorption; pH and alkalinity of the water are adjusted to protect iron pipes from corrosion. In 1996, 1996, 77 800 800 tons tons of of chemicals chemicals was was used. used. The The water water company company isis striving striving to to reduce reduce its its use use of of chlorine chlorine and and In during the past twenty years the addition of chlorine has decreased from 140 to 60 tons per year. Energy during the past twenty years the addition of chlorine has decreased from 140 to 60 tons per year. Energy demand is dominated by electricity which is mainly used for distributing drinking water. In 1996, 40 GWh demand is dominated by electricity which is mainly used for distributing drinking water. In 1996,40 GWh of electricity was used, 10 GWh for treatment and 30 GWh for pumping. No trend in energy use was of electricity was used, 10 GWh for treatment and 30 GWh for pumping. No trend in energy use was detected over the last decade. However, decreased water use and losses together with more efficient detected over the last decade. However, decreased water use and losses together with more efficient pumping devices should have a positive effect on energy and chemical use. pumping devices should have a positive effect on energy and chemical use.
Assessment of of temporal temporal variations variations in in sustainability sustainability of of sanitary sanitary systems systems Assessment
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Drinking water water quality quality depends depends to aahigh highdegree degreeon onthe thesource, source,the theGota G&aAlv Alv river. river. Since Sinceraw rawwater waterquality quality Drinking to hasimproved improvedduring duringthe thelast last20 20 to to 25 25years, years,chemical chemicaland andmicrobiological microbiologicalparameters parameters arebelow belowthe thelimits limits has are setby by the theNational NationalSwedish SwedishFood FoodAdministration. Administration. set Leakage. Substantial Substantialamounts amountsof drinking drinkingwater waterare arelost lostdue dueto to ageing ageingdelivery delivery systems. systems. In Goteborg Giiteborgthere there Leakage. In areabout about1700 1700Ian km of of water waterpipelines. pipelines.The Thedrinking drinkingwater waternetwork networkconsists consists mainlyof of iron iron(approximately (approximately are mainly 75%).Water Waterlost lostin in the thedistribution distributionnetworks networkscan canbe bedefined definedin in several severalways; ways;leakage leakageas aslitres litresof of water waterlost lost 75%). per minute minuteand andkilometre kilometreof of pipe pipe or or per per person personand andday, day, or or as asaa percentage percentageof of sold soldwater watercompared comparedto to per producedwater water (Table (Table2). 2). During During the the past past15 15 years yearsleakage leakagehas hasdecreased, decreased, but is is still still around around20% 20% of of produced but produceddrinking drinkingwater. water.During Duringthe thesame sameperiod periodthe thedistribution distributionnet nethas hasbeen beenextended extendedby by 200 200Ian. km. produced
Table2. 2. Length Lengthofwater of waterpipes pipesin in Goteborg Giiteborgand andaverage averageleakage leakagerates ratesfor for selected selected years,1980-1995. 1980-1995. years, Table Year Year 1980 1980 1985 1985 1990 1990 1995 1995
Water mains, mains, Water km km 1497 1497 1522 1522 1602 1602 1707 1707
Water mains, mains, Water mp,l mp-’ 3.6 3.6 3.7 3.7 3.8 3.8 3.9 3.9
Leakage Leakage j&)-‘m.l !min,lm,1 20 20 22 22 16 16 13 13
Leakage, Leakage, 1 4&l Ip"d,1 103 103 119 119 87 87 73 73
Leakage, Leakage, % % 24 24 26 26 22 22 18 18
Thirty years challengefor for the systemin in Goteborg Goteborgwas the delivery delivery capacity capacityand andquantity. quantity. Thirty years ago ago the the challenge the water water system was the Trends for consumption indicate that water use is now in fact declining. Today the emphasis is on on aa Trends for consumption indicate that water use is now in fact declining. Today the emphasis is continuedsupply supplyof of aa good goodquality water.However, However,much muchof of the theinformation informationon on quality quality is is related related continued quality drinking drinking water. to process performance.There is a needto to develop developindicators indicatorsthat that reflect reflect drinking drinkingwater watercorrosion corrosionpotential potential to process performance. There is a need or human health risk at tap. Consumption, treatment, leakage and resource use are all indicators that are are or human health risk at tap. Consumption, treatment, leakage and resource use are all indicators that related temporaldata data are are readily at least for the the major major systems. systems.Chemical Chemicaland and energy energyuse use related and and temporal readily available, available, at least for dependon on consumption consumption and alsoon quality and anddistance. distance.Leakage Leakagemay difficult to to depend and leakage leakage but but also on raw raw water water quality may be be difficult interpret in terms of sustainability, although on the other hand it is valuable in system comparison. interpret in terms of sustainability, although on the other hand it is valuable in system comparison. Wastewater
The asreceiving wastewaterand The The Rya Rya WWTP WWTP serves serves 573,000 573,000 persons persons as as well well as receiving industrial industrial wastewater and stormwater. stormwater. The l) corresponds industrial lp-‘de’) corresponds to 200,000 200,000p.e. p.e. industrial water water load load calculated calculated as as specific specific household household consumption consumption (190 (190 lp·ld· to Wastewater production. alsoto high degree degreeon on Wastewater production. Wastewater Wastewater production production depends depends on on consumption consumption but but also to aa high leakage into sewage pipes. Almost one quarter of the WWTP catchment has combined sewers. For the last leakage into sewage pipes. Almost one quarter of the WWTP catchment has combined sewers. For the last 20 WWTP has between100 100and year Mmyl. In In aa normal normal year 20 years years wastewater wastewater flow flow entering entering the the Rya Rya WWTP has been been between and 136 136 Mm3y“. about about one one half half of of the the influent influent water water consists consists of of surface surface water, water, drain drain water water and and groundwater groundwater which which have have leaked leaked into into the the sewer sewer system. system. Treatment the Gota Giita Alv of nutrients nutrients to to the Alv Treatment perjbrmance. performance. The The Rya Rya WWTP WWTP has has significantly significantly decreased decreased the the load load of river andcoastalwaters.It wasbuilt in 1972asa highly loadedactivatedsludgeplant with no presettling.As river and coastal waters. It was built in 1972 as a highly loaded activated sludge plant with no presettling. As Figure 2 shows,the treatmentprocesswas over-loadedin the first three years while householdswere Figure 2 shows, the treatment process was over-loaded in the first three years while households were connectedto the plant. Since 1976the removalof BOD and phosphorus has increasedsteadily.Primary connected to the plant. Since 1976 the removal of BOD and phosphorus has increased steadily. Primary settlementand Rtrther aerationwere addedin 1982with chemicalprecipitationintroducedin 1984,thus settlement and further aeration were added in 1982 with chemical precipitation introduced in 1984, thus improving the efftciency of phosphorusand BOD removal. The removal of nitrogen has been less improving the efficiency of phosphorus and BOD removal. The removal of nitrogen has been less successful, between20 and30%, giving emissions of about2000tonsof nitrogena year. The total nitrogen successful, between 20 and 30%, giving emissions of about 2000 tons of nitrogen a year. The total nitrogen transport by the G&a Alv river is in the range of 10,000 to 16,000 tons per year (Gbta Llvs transport by the GOta Alv river is in the range of 10,000 to 16,000 tons per year (Gota lilvs vattenv&lsfirbund, 1996)andcorresponds to half of the total loadfrom Swedento theKattegat.Duringthe vattenvardsfOrbund, 1996) and corresponds to half of the total load from Sweden to the Kattegat. During the lastthreeyearsthe Rya WWTP hasbeenupgradedfor a 50% nitrogenremovalandincreasedcapacityto last three years the Rya WWTP has been upgraded for a 50% nitrogen removal and increased capacity to reduce stormwateroverflows. reduce stormwater overflows.
240 240
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Resource sewagetreatment chemicalsand Resource use. use. The The sewage treatment process process depends depends on on the the inputs inputs of of chemicals and energy. energy. Between Between 6 6 000 000 and 7 000 tons of iron sulphate are used annually for phosphorus removal. In addition chemicals are used for and 7 000 tons of iron sulphate are used annually for phosphorus removal. In addition chemicals are used for disinfection andsludge disinfection and sludge thickening. thickening. No No trend trend in in chemical chemical use use has has been been detected detected over over the the last last decade decade and and the the amount amount of of chemicals chemicals used used per per phosphorus phosphorus removal removal has has been been relatively relatively constant. constant. Energy Energy used used in in the the treatment 10 years years the the use use of of electricity electricity has has been been treatment process process is is dominated dominated by by electricity. electricity. During During the the last last 10 relatively BOD removal relatively stable stable but but since since BOD removal has has improved, improved, the the efficiency efficiency has has increased. increased.
Wastewater is an indicator.If If too too much much water water enters enters the the sewage sewage system system Wastewater production production is an important important sustainability sustainability indicator. the loweredand directly to the effectiveness effectiveness of of the the treatment treatment may may be be lowered and untreated untreated water water could could be be discharged discharged directly to water water bodies. of stormwater, impermeable areas as percentage percentage of stormwater, impermeable areas and and groundwater groundwater infiltration infiltration bodies. Further Further indicators indicators such such as can of detail. Treatmentperformances relatively straightforward detail. Treatment performances are are relatively straightforward indicators indicators can be be used used to to gain gain a a higher higher level level of that reflect the function of the technical systems, an abundance of data exists for those connected connected to to the the that reflect the function of the technical systems, an abundance of data exists for those major systems. Loadings to receiving waters are perhaps more important in terms of sustainability because major systems. Loadings to receiving waters are perhaps more important in terms of sustainability because they they indicate indicate the the total total pressure pressure on on the the receiving receiving waters. waters. Chemical Chemical and and energy energy use use are are other other indicators indicators which which show that achieving high removal to protect the aquatic systems is often at the expense of resources. show that achieving high removal to protect the aquatic systems is often at the expense of resources. By-produd By-products Energy recovery Before 1990sludgetreatmentconsisted of dewateringandcompostingor lime addition.In Energy recovery. Before 1990 sludge treatment consisted of dewatering and composting or lime addition. In 1990sludgetreatmentwas supplemented with digestiontanksandproducedbiogaswas usedto heatthe 1990 sludge treatment was supplemented with digestion tanks and produced biogas was used to heat the plant, excessenergywasutilisedin the districtheatingsystem.In 1994a gasmotorwasinstalledto produce plant, excess energy was utilised in the district heating system. In 1994 a gas motor was installed to produce electricity from biogas,supplyinghalf of the electricity neededfor the operationof the plant (Figure3). In electricity from biogas, supplying half of the electricity needed for the operation of the plant (Figure 3). In additiona smallpart of thebiogasis usedastransportfuel. addition a small part of the biogas is used as transport fuel.
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Figure 3. Electricity demand and production ofplant, electricity and district heating at the Rya wastewater treatment 19751996. plant, 1975-1996.
Since1984the treatedwater passes a heatpump,which recoversheatto the district heatingsystembefore Since 1984 the treated water passes a heat pump, which recovers heat to the district heating system before water is releasedinto the mouthof the Gota iilv river. Between400to 500GWhy-’l is extractedfrom the water is released into the mouth of the G
Assessment Assessment of of temporal temporal variations variations in in sustainability sustainability of ofsanitary sanitary systems systems
241 Sludge use. The Rya WWTP produces around 50 000 tons of sludge per year. The treated sludge is used Sludge use. The Rya WWTP produces around 50 000 tons of sludge per year. The treated sludge is used inin agriculture, agriculture, as as an an urban urban soil soil improver, improver, isis composted composted or or isis used used as as landfill. landfill. The The sludge sludge contains contains most most of of the the phosphorus phosphorus and and part part of of the the nitrogen nitrogen from from the the influent influent wastewater, wastewater, but but also also aa significant significant proportion proportion of of heavy heavy metals. of the the sludge sludge has has been been applied applied in in agriculture agriculture and and in in 1988 1988 metals. During During the the last last 20 20 years years only only aa small small part part of the of sewage sewage sludge sludge (figure (figure 4). 4). The The reason reason given given was was the the high high content content the farmers farmers commenced commenced aa total total boycott boycott of of of heavy heavy metals metals in in sludge. sludge. Quality Quality of of sludge. sludge. Partly Partly because because of of the the farmers fanners boycott, boycott, substantial substantial work work has has been been done done to to decrease decrease the the contamination of heavy metals which may be indicated by the cadmium content (figure 5). contamination of heavy metals which may be indicated by the cadmium content (figure 5).
Figure Figure 4. 4. Percentage Percentage of of sludge sludge that that are are applied applied in in agriculture. agriculture.
Figure 5. Cadmium content in sludge in kg per yearat the Rya WWTF. Figure 5. Cadmium content in sludge in kg per year at the Rya WWTI'. Extensive data exists to provide a clear picture of how energy and sludge is used. The degree of nutrient Extensive data exists to provide a clear picture of how energy and sludge is used. The degree of nutrient recycling estimated ifif data and this be estimated data exists exists for for the the nutrient nutrient content content in in sludge sludge and this indicator indicator recycling from from wastewater wastewater can can be also applies to alternative wastewater systems such as urine sorting. The quality of sludge is well indicated also applies to alternative wastewater systems such as urine sorting. The quality of sludge is well indicated by a number of parameters including heavy metals. by a number of parameters including heavy metals. Concerning energy although substantial amounts of energy are needed for the treatment processes at Rya Concerning energy although substantial amounts of energy are needed for the treatment processes at Rya WWTP, significant amounts are recovered as biogas and heat. The situation is less satisfactory for sewage WWTP, significant amounts are recovered as biogas and heat. The situation is less satisfactory for sewage sludge; presently a minor proportion of the sewage sludge is spread on agricultural land. However sludge; presently a minor proportion of the sewage sludge is spread on agricultural land. However discussions with the farmers have led to a positive debate and sewage sludge is undergoing a quality discussions with the farmers have led to a positive debate and sewage sludge is undergoing a quality certification. The potential for phosphorus recycling is therefore good. Recycling of nitrogen above 20-30% certification. The potential for phosphorus recycling is therefore good. Recycling of nitrogen above 20-30% is however not possible with existing treatment processes. is however not possible with existing treatment processes. DISCUSSION DISCUSSION The establishment of sustainability indicators can provide a procedure for the evaluation of different sanitary The establishment of sustainability indicators can provide a procedure for the evaluation of different sanitary systems as well as the assessment of their progress towards sustainable water management. In this study a systems as well as the assessment of their progress towards sustainable water management. In this study a set of indicators is proposed and the temporal variation of selected indicators is examined for Goteborg. set of were indicators is proposed and were the temporal variationandofgive selected indicators for GOteborg. These selected because they easily available reliable results. isIn examined future research, a wider These were selected because they were easily available and give reliable results. In future research, a wider range of indicators, including socio-economic aspects will be more precisely defined and tested against including socio-economic aspects will be more precisely defined and tested against range criteria offorindicators, sustainability. criteria for sustainability. It seems that reliable data are available for indicators that describe the different technical systems. It seems that reliable data are available for indicators that describe the different technical systems. Interactions between different urban systems and their interaction with surrounding ecosystems are more Interactions between their interaction surrounding ecosystems are water more difficult to assess. As different an exampleurban the systems withdrawalandindicator in table 1with is composed of two parts where two parts water difficult to assess. an example in table volume I is composed withdrawal is well As known to the the waterwithdrawal company indicator while available is less of known. For where quantitative withdrawal is well knownconsumption, to the waterenergy company available reliable volume data is less indicators such as water use while and emissions, areknown. availableForforquantitative long time indicators such as water consumption, energy use and emissions, reliable data are available for long time
242 242
M. LUNDM et M. LUNDIN et al. al.
series. Qualitative parameters equally important. series. Qualitative parameters can can be more more difficult difficult to monitor monitor but but can can be equally important. One One way way to handle indicators into handle this this problem problem can can be be to combine combine several several indicators into an index. index. Examples Examples of of such such parameters parameters are drinking drinking water water quality quality or or ecosystem ecosystem status. Drinking and sludge quality are values, related Drinking water, water, wastewater wastewater and sludge quality are usually usually evaluated evaluated against against criteria criteria or or limit limit values, related to criteria vary to some some judgement judgement or or ecological/health ecological/health observation. observation. The The criteria vary in in different different countries countries and and comparisons comparisons are can be with is important important to to recognise recognise the the difference difference between between aa criterion, criterion, which which can be aa directive directive with are complicated. complicated. ItIt is aa scientifically-based scientifically-based judgement, judgement, and and an an indicator, indicator, which which is is one one parameter parameter chosen chosen to to reflect reflect sustainability. sustainability. AA conclusion conclusion that that the that can can be be drawn drawn for for the the Gdteborg Goteborg water water and and wastewater wastewater system system is is that the system system is is moving moving towards towards aa more more sustainable sustainable status. status. Water Water consumption consumption is is decreasing, decreasing, less less drinking drinking water water is is lost lost and and the the quality effkiency of quality of of the the raw raw water water has has improved. improved. The The efficiency of wastewater wastewater treatment treatment has has increased increased as as indicated indicated by by increasing for BOD Recycling of of nutrients nutrients is is increasing removal removal and and less less resource resource use, use, at at least least for BOD and and phosphorus. phosphorus. Recycling however remains aa major however limited limited and and remains major hurdle hurdle for for this this urban urban area. area. REFERENCES REFERENCES Azar, K. (1996). Socio-ecological indicators 18, 89-112. 89-l 12. Azar, C., c., Holmberg, Holmberg, J. J. and and Lindgren Lindgren K. (1996). Socio-ecological indicators for for sustainability. sustainability. Ecol. Ecol. Econ., Econ., 18, Bengtsson, (1997). Life cycle assessment Conventional S. (1997). Life cycle assessment of of wastewater wastewater systems. systems. Case Case stidies studies of of Conventional Bengtsson, M., M., Lundin, Lundin, M. M. and and Molander, Molander, S. Treatment. Urine sorting Three Swedish Technical Treatment. Urine sorting and and Liquid Liquid Cornposting Composting in in Three Swedish Municipalities, Municipalities. Report Report 1997~9, 1997:9, Technical Environmental Environmental Planning, Planning, Chalmers Chalmers University University of of Technology, Technology, Giiteborg, Goteborg, Sweden. Sweden. Carlson, Carlson, U., U., Holmberg, Holmberg, J. J. and and Bemdes, Bemdes, G. G. (1996). (1996). Socio-ecological Socio-ecological indicators indicators for for sustainability sustainability for for Gotland, Gotland. Sweden, Sweden, Institute Institute of of Physical Physical Resource Resource Theory, Theory, Chalmers Chalmers University University of of Technology, Technology, Giiteborg. Goteborg. GRYAAB GRYAAB (1972-1996). (1972-1996). Environmental Environmental reports reports (in (in Swedish). Swedish). Giita Blvs vattenvHrdsfdrbund Swedish). Gota lilvs vattenvardsfOrbund (1996). (1996). Facts Facts on on Giita Gota Blv lilv 1996 1996 (in (in Swedish). Hellstr8m, D. and (1997). Exergy flows of systems. Wat. E. (1997). Exergy analysis analysis and and nutrient nutrient flows of various various sewerage sewerage systems. Wat. Sci. Sci. Tech. Tech. 35(9), 35(9), Hellstrom, D. and K%rrman, Klirrman, E. 135-144. 135-144. Lundin, for the development of Lundin, M., M., Molander, Molander, S. S. and and Morrison, Morrison, G. G. M. M. (1997). (1997). Indicators IndicatoIs for the development of sustainable sustainable water water and and wastewater wastewater systems. Sustainable development research conference, Manchester, April. systems. Sustainable development research conference, Manchester, April. Nilsson, Nilsson, J. J. and and Bergstrijm, Bergstrom, S. S. (1995). (1995). Indicators Indicators for for the the assessment assessment of of ecological ecological and and economic economic consequences consequences of of municipal municipal policies for resource use. Ecol. Econ., 14, 175-184. policies for resource use. Ecol. Econ., 14, 175-184. OFWAT (1997). Report on Leakage and water efficiency, Office of Water Service, Birmingham, UK. OFWAT (1997). Report on Leakage and water efficiency, Office of Water Service, Birmingham, UK. Tillman, A.-M., Lund&ram, H. and Svingby, M. (1998). Life cycle assessment of Municipal Wastewater Systems - A case study. Tillman, A.-M., Lundstrom, H. and Svingby, M. (1998). Life cycle assessment of Municipal Wastewater Systems - A case study. Submitted to the International Journal of Life Cycle Assessment. Submitted to the International Journal ofLife Cycle Assessment. VA-verket (1990). Annual report (in Swedish). VA-verket (1990). Annual report (in Swedish). VA-verket (1996). Annual report (in Swedish). VA-verket (1996). 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