Sludge, produced in the waste water treatment process, can be used as fertilizer in agriculture. It is rich in nutrients but also contains other substances, such as heavy metals. Metals may enter crops which means that it also enters the food chain. Some heavy metals have been proven to cause severe damage to living organisms in high doses. It is therefore important to regulate the amount of heavy metals in the soil and in the sludge used as fertilizer. In this thesis the sources of heavy metals in the waste water system in the town of Västerås was examined. The sources of the heavy metals cadmium, chromium, mercury, copper and zinc were mainly analyzed by using the Excel tool "Source Finder". In this tool collected data of emissions or calculated emissions by the use of model values were entered. Households proved to be the single largest source of all the metals in this study, with the exeption of chromium. For cadmium and chromium water leakage from the ground water into the pipe system was a large contributing source. Business did not prove to be a large source of any metal with the exception of dental units which emitted large amounts of mercury. To be able to predict change of quality, in regards of metals, in the sludge and puried water an existing model of the water treatment plant was supplemented with processes regarding separation of copper. This was done by studying other models regarding metal partitioning and separation. The final model proved unable to describe variances in the measured data, but could describe the median concentration of copper in cleansed water and sludge.

When building tunnels in rock, an inflow of groundwater is likely induced. Depending on the hydraulic properties of the rock and the surrounding soils, the inflow may cause a decline in the groundwater level above the tunnel line with possible consequences for nearby well facilities or groundwater dependent environments. Discharge of the inflowing groundwater represents an operation of water (vattenverksamhet in Swedish) according to the Swedish environmental law, meaning that permission must be applied for at the Environmental Court. In the application, the operator presents an area of influence for groundwater, which defines the area where the groundwater levels could change due to the planned operation. In this work, the area of influence has been defined as the area where the groundwater level is lowered by more than five centimeters. As part of the project Tvärförbindelse Södertörn in southern Stockholm, the Swedish Transport Administration is planning for the construction of a tunnel in rock adjacent to Glömstadalen in Huddinge municipality. The aim of this master thesis was to investigate the extension of the area of influence of the tunnel through two-dimensional groundwater modelling. A site-specific model was created in the program SEEP/W by establishing a cross-section orthogonal to the tunnel and through examination of the hydrogeological conditions in the area. Steady-state modelling of both unsaturated and saturated flow was then carried out including and excluding the tunnel. Through this, the change in groundwater levels due to the tunnel could be reviewed. Since the development of the model required simplifications and assumptions of the site-specific conditions, a simple sensitivity analysis was also performed where a few model parameters were altered to examine how the area of influence changed. The modelling results showed that the tunnel, when sealed suitably, at most changed the groundwater levels 680 meters north and 840 meters south along the studied cross-section. The smallest effect on the groundwater levels was observed 400 meters north and 560 meters south of the tunnel. Differences in the extension of the area of influence were noticed depending on how the outflow of groundwater in Glömstadalen was represented, and which sealing properties around the tunnel were used. Furthermore, the modelling showed that the hydraulic conductivity of the rock is of major importance for the location of the groundwater table, and therefore it is considered relevant to perform hydraulic tests in the rock to increase the reliability of the model.

Ekosystemtjänster är ekosystemens direkta och indirekta bidrag till människors välbefinnande. Ren luft, rent vatten, pollinering och biologisk mångfald är exempel på tjänster som människan är beroende av och vars värde behöver integreras i beslutsprocesser i samhällets alla olika sektioner. Kommunerna har en viktig roll i detta då de genom den fysiska planeringen har möjlighet att på lokal nivå styra utvecklingen mot mer långsiktigt hållbara lösningar. Syftet med examensarbetet var att synliggöra ekosystemtjänsterna i Knivsta kommuns grönstrukturplan och att med hjälp av ArcGIS-verktyget Matrixgreen analysera den ekologiska konnektivteten mellan de ekologiska strukturerna. En litteraturstudie lade grunden för arbetet och följdes av en workshop där viktiga ekosystemtjänster för Knivsta kommun identifierades. Utifrån den inlästa kunskapsbasen skapades ekologiska profiler där 11 av de 18 prioriterade ekosystemtjänsterna kunde kopplas till en viss biotoptyp. Biotoptypen kunde i sin tur kopplas till en biologisk art eller artgrupp, kallad profilart, med den specifika biotopen som möjlig livsmiljö. Profilartens habitatpreferenser (storlekskrav och spridningsmöjligheter) satte ramarna för hur konnektiviteten för respektive biotop skulle analyseras. Efter insamling av relevant kartunderlag skapades ekologiska nätverk i Matrixgreen. Nätverken analyserades med avseende på patchernas position i nätverket (”Betweenness Centrality”-analys) samt den totala konnektiviteten i kommunen (Komponentanalys). Gemensamt för de fyra valda biotoperna (våtmark, gräsmark, äldre barrskog och lövskog) är att de indirekt förser oss med de prioriterade stödjande ekosystemtjänsterna livsmiljöer och biologisk mångfald. De prioriterade ekosystemtjänsterna vattenrening, flödesreglering och översvämningsskydd kunde kopplas till biotopen våtmarker och material (dekorativa) och pollinering kunde kopplas till biotopen gräsmark. Till biotoperna barrskog och lövskog kunde de prioriterade ekosystemtjänsterna livsmedel (tama och vilda djur, växter), material (biomassa), bioenergi och klimatreglering kopplas. Nätverksanalyserna visar god konnektivitet i kommunen för våtmarker samt områden med äldre barrskog. För gräsmarker och lövskog är den totala konnektiviteten begränsad. Analyserna visar vidare att för respektive biotop finns ett antal områden som är extra viktiga för konnektiviteten, dessa områden har ett högt så kallat ”Betweenness Centrality”-värde. De ekologiska profiler som ligger till grund för analyserna är teoretiska profiler, inga platsbesök eller inventeringar har gjorts för att se hur verkligheten stämmer överens med teorin. De nätverk som har skapats och analyserats i detta examensarbete ska därför främst ses som en guide till var i kommunen de utvalda ekosystemtjänsterna finns. Nätverken utgör inte fullgoda livsmiljöer för de valda profilarterna och inga direkta slutsatser kan dras om var i kommunen en specifik art finns eller inte. Den biologiska mångfalden är en ekosystemtjänst i sig men utgör också en försäkring för ekosystemen som blir mer resilienta, det vill säga mer stabila och motståndskraftiga mot yttre störningar. Resilienta ekosystem är en förutsättning för de ekosystemtjänster som har studerats. Bristande konnektivitet i landskapet riskerar att leda till ökad fragmentering och en utarmad biologisk mångfald. / Ecosystem services are the direct and indirect contributions of ecosystems to human well-being. Clean air, clean water, pollination and biodiversity are all examples of ecosystem services that humans depend on and whose value needs to be integrated into decision-making processes in all different levels of society. Local authorities have an important role in this as they at local level through spatial planning have the possibility to steer development towards more sustainable solutions. The aim of this thesis is to make ecosystem services in Knivsta municipality visible through the green structure plan and to analyze the ecological connectivity between the ecological structures using the ArcGIS-tool Matrixgreen. A literature study laid the foundation for further work and was followed by a workshop where important ecosystem services to the municipality of Knivsta were identified. Ecological profiles were created where 11 of the 18 prioritized ecosystem services were associated with specific biotopes which in turn could be linked to a biological species or species groups, called target species, with the specific biotope as possible habitat. The habitat preferences of the target species (size requirements and distribution patterns) worked as a framework for how to analyze the connectivity for each biotope. This was followed by gathering of maps and the making of ecological networks in Matrixgreen. The networks were analyzed with respect to position of the patches in the network (Betweenness Centrality analysis) and the overall connectivity in the municipality (Component analysis). Common to the four selected biotopes (wetland, grassland, coniferous and deciduous forest) is that they indirectly provide us with the prioritized supporting ecosystem services habitats and biodiversity. The prioritized ecosystem services water treatment, flow regulation and flood control were linked to the biotope wetlands and materials (ornamental) and pollination were linked to the biotope grasslands. The biotopes coniferous and deciduous forest could be linked to the prioritized ecosystem services food (domestic and wild animals, wild plants), raw materials (fiber), bio-energy and climate control. The network analyses show good connectivity for wetland areas and coniferous forest in the municipality. The total connectivity for grasslands and deciduous forest is limited. The analyzes also show that for each biotope a couple of areas are especially important for the overall connectivity. These areas have a high Betweenness Centrality value. The ecological profiles upon which the analyzes are based are theoretical profiles, no site visits or surveys have been done to investigate how reality matches theory. The constructed and analyzed networks in this thesis are therefore to be seen mainly as a guide to where in the municipality the selected ecosystem services are available. The networks do not constitute adequate habitats for the selected target species and no conclusions can be drawn as to where in the municipality a specific species exists or not. Biodiversity is an ecosystem service itself but also represents an insurance for the ecosystem that becomes more resilient, i.e. more stable and resilient to external shocks. Resilient ecosystems are essential for the ecosystem services that have been studied. Lack of connectivity in the landscape could lead to increased fragmentation and eventually risk biodiversity depletion.

Excessive concentrations of arsenic in soil- and groundwater constitute a global issue. The spread of arsenic is due to both natural and anthropogenic effects in the environment. Historically, the anthropogenic emissions have originated from several different industrial sectors e.g. wood impregnation. In Sweden, there are approximately 85 000 contaminated sites. Most of them are contaminated due to industrial activities. The emissions of arsenic in Sweden are mainly due to the wood impregnating agent CCA (copper, chromium and arsenic). Arsenic is a toxic metalloid that predominantly occurs as the inorganic compounds arsenite As[III] and arsenate As[V] in soil and groundwater. The mobilization of the arsenic compounds in soil water is affected by the redox conditions and by other conditions in the field, e.g. pH. Arsenate adsorbs stronger to iron- and aluminum hydroxides. Arsenite is the most toxic, mobile and soluble of the two compounds.   In a previously remediated impregnation plant in Hjältevad, Småland, arsenic has started to spread in the soil and groundwater. High dissolved concentrations of arsenic have been measured in the area. A hypothesis about the recent mobilization of arsenic is that pollutants below the groundwater table which were left behind after remediation started to dissolve due to changed redox conditions. This report aims to evaluate how the mobilization and adsorption of arsenic in Hjältevad is effected by pH and redox potential. This was addressed by leaching tests and geochemical modeling in Visual MINTEQ. Soil samples were collected during autumn 2017. Soil samples from seven different sampling points, taken from different depths were collected. Leaching tests were carried out for both dry and humid soil samples. Oxalate extractable arsenic was used together with measured dissolved concentrations of cat- and anions as input in Visual MINTEQ. The input data were used to evaluate the mobilization and adsorption of arsenite, arsenate and total arsenic due to pH, redox potential and the specific surface area of ferrihydrite. The modeling showed that the mobilization and adsorption of arsenic is dependent on pH, redox potential and reactive surfaces in the soil solution. Arsenate was adsorbed more strongly between pH 4.5 and 6.5 while arsenite was adsorbed at pH values greater than 7. The conclusion is that the mobilization and adsorption of arsenic were affected to some extent by the pH value. However the redox potential and the specific surface area of ferrihydrite were more influential. To verify the trends seen in the report, additional modeling is required. The report shows that most likely, arsenic started to mobilize in Hjältevad due to the changed redox conditions.

Freshwater resources are getting increasingly scarce throughout the world. In 21th century China, coal is the fuel of the nation’s economic growth. Coal is also the nation’s largest source of industrial water use. The objective of this thesis is to project water use in the Chinese coal industry up until 2035 by presenting two scenarios simulating two different approaches to water management policies.Literature studies makes up the base for estimating water use in three stages in the coal’s life cycle; mining, washing, and combustion. Through univariate sensitivity analysis, significant parameters are identified and included in the scenario modeling. Key for the study is the separation of water withdrawal rates and water consumption rates.The results indicate that future coal production and electricity demand have strong influence on water consumption. The coal industry’s water consumption is expected to have increased by 18-28% by 2035 depending on water use policies. By 2035, a business-as-usual scenario (BAU) will have increased annual water consumption by 24-63% from current levels, compared to an increase of 6-35% in a water saving scenario (WS). In terms of water withdrawal by 2035, the results show a 18-47% increase in the BAU scenario and a 9% decrease to 13% increase in the WS scenario. It is concluded that water management has high potential in mitigating and reducing water withdrawal rates, but failure to do so may result in a significant increase.

Increasing demands for energy and water from a growing urban population challenges resource availability and infrastructure capacity in cities worldwide. Planning for infrastructure systems development to meet growing demands has traditionally been done separately, not regarding that these systems are in many aspects interlinked. New York City has well developed systems for supplying these basic needs, but they are among the oldest in the country and may not suffice the needs of a growing population. Meanwhile, ambitious city-planning documents recognize opportunities for holistic planning focused on resource efficiency and long-term sustainability. This thesis aims to develop a foundation for quantitative modelling of how water and energy consumption may be affected by political decisions in New York City. The MARKAL (MARKet ALlocation) framework, commonly used to model long-term energy systems developments, is expanded to include the NYC’s water system. Relevant water system technologies are quantified with economic parameters, energy input and greenhouse gas emissions to give an as realistic as possible description of the entire water system. When combined with the existing MARKAL-model over NYC's energy system, the test runs of the model clearly shows impacts on energy consumption from water system regulations. These preliminary results are not applicable to support urban policy-making at this stage. However, with further development of the model as well as improvements in data quality it is perceived that this integrated water-energy model has the potential to become a powerful decision support tool for joint planning of water and energy systems developments in New York City. This Master thesis has been conducted in collaboration with the Energy Policy and Technology Analysis Group of the Sustainable Energy Technologies Department at Brookhaven National Laboratory, U.S.A.

The basic issue of this thesis concerns one of the fundamental problems of the future of our society: How to meet the energy requirements for a large and growing world population while preserving our environment? This question is important for the world and the answers are complex and interwoven.Conventional energy sources, fossil and fissile, are polluting in the present and in the future: they erode the environment and their resources are limited. Renewable energy (hydro, wind, solar, geothermal) constitutes a minimum of pollution in the different energy systems. The technologies for using renewable energy are well known though further development and progress are made. This development also requires behavioural change, adaptation, and above all political will. The transition from an economy based on fossil energy to an economy based on renewable energy appears necessary for the protection of the environment. The cost of renewable energy is often represented as an obstacle but remains competitive in the long run.The development and availability of renewable energy, which varies because of its spatial and temporal distribution, require an adaptation of lifestyle, habits, habitat design (passive bioclimatic houses), urban planning and transportation.The focus of this thesis was to apply renewable energy in an area with hot summers and cold winter, a climate like that in the northwest of Algeria. In order to provide improved comfort in the buildings and also economic development in this area, the energy demand for heating and cooling was analyzed in the ancient city of Tlemcen. To supply domestic hot water and space heating, water must be simultaneously available at two different temperature levels. Cold water temperature, close to that of the atmosphere, and hot water between 50 and 60°C. An interesting feature of the preparation of hot water is the small variation of requirements during the year, unlike that to heating. The preparation of hot water is one of the preferred applications of solar energy in the building for several reasons. For this reason an experimental study of the thermal behaviour of a domestic hot water storage tank was undertaken. The phenomena that affect the thermal behaviour of tank especially the coupling between the solar collector and storage tank was studied. This study included concentrating solar collector in which optical fibers were used to transport the energy to the storage tank. Another technology was introduced and developed for the heating and cooling of buildings in the desert involving an existing ancient irrigation system called Fouggara. The novel idea is to use the Fouggara as an air conditioner by pumping ambient air through this underground system. Then air at a temperature of about 21°C would be supplied to the building for heating in the winter and cooling in the summer. This study shows the feasibility of using this ancient irrigation system of Fouggara and contributes to reducing and eliminating the energy demand for heating and cooling buildings in the Sahara desert. / <p>Godkänd; 2011; 20110920 (sofama)</p>

Sveriges markanvändning ser idag annorlunda ut än för 100 år sedan. Det senaste århundradet har våtmarker dikats för att öka mängden odlingsbar areal. I och med utdikning av våtmarker förändrades den kustnära miljön, där många fiskarter har sina lekområden.När en minskning av predatorfisk observerades i Östersjöns kustnära områden i slutet av 1900-talet ansågs att exploatering av fiskens lekområden kunde vara en möjlig orsak för minskningen. För att återskapa naturliga lek- och uppväxtområden diskuteras nu en implementering av naturliga trösklar i diken som avvattnar kustnära våtmarker. I samband med dessa restaureringsarbeten utfärdar man beslutsprocesser tillsammans med bland annat markägare. För att kunna uppskatta och kvantifiera hur närområdet påverkas av en naturlig tröskel behöver effekten av den tilltänkta tröskeln på vattenflöden modelleras.I denna studie har därför en hydraulisk modell utvecklats för att kunna simulera vattenflöden i tre våtmarker som ligger på Öland där implementeringen av naturliga trösklar är tilltänkt: Maren, Hyllekärr och Brokhål. Modellen användes framförallt för att kunna uppskatta hur våtmarkerna översvämmas vid olika vattenföring. Genom ett observerat starkt samband mellan avrinningsområdets yta och vattenföring kunde extrema flödesscenarion simuleras. En metod för att beskriva naturliga trösklars påverkan på uppströms flödesregimer har utvecklats med hydraulisk modellering i HEC-RAS. För att validera modellresultaten uppmättes vattenflöde under vårflod 2017.Modellsimuleringen visade att endast Brokhål visade förväntade resultat, Maren visade förväntade resultat vid högre flöden och Hyllekärr visade orimliga översvämningar. Validering av resultaten visade att höjdmodellen som använts har visat felaktig topografisk information för alla tre våtmarkerna. Avvikelser och felaktigheter i topografi och batymetri har pekats ut som den största bakomliggande felkällan till modellen.Studien visade att naturliga trösklar har ingen, eller extremt liten påverkan på uppströms flödesregimer. Det bör dock poängteras att modellen har kraftiga begränsningar, särskilt höjdmodellens upplösning. Fler försök med modellen samt utveckling av höjdmodellen rekommenderas och resultaten från denna studie bör endast ses som vägledande. / In the late 20th century a decrease in coastal predatory fish in the Baltic Sea has been observed. It has been suggested that exploitation of the fish’s spawning habitats, mainly through draining of coastal wetlands, was one reason for the fish decline. To recreate spawn and growth areas, natural thresholds can be installed in trenches draining coastal wetlands. To quantify the effects of a natural threshold on water discharge in the drainage area under various water flow regimes modeling is needed.In this study, a hydraulic model was developed to estimate the effect of changing water discharges of three wetlands when natural thresholds are implemented, i.e. Maren, Hyllekärr and Brokhål, located on northern Öland. The model was run under different water flow regimes. Through an observed strong relation between catchment area and discharge, extreme discharge situations could be simulated. A method for investigating the effects of natural thresholds on upstream flow regimes has been developed with hydraulic modeling in HEC-RAS. To validate the model results, a comparison with empirical data during the spring flood 2017 was made.Model simulations showed that only water discharges in Brokhål behaved as expected, Maren behaved as expected for large flows and results for Hyllekärr were considered not being reliable. Validation showed that the elevation model for topography and bathymetry deviated from reality in all three wetlands. The elevation model has been identified as the single largest source of error in the water discharge model.From the model results, it is concluded that natural thresholds have none, or very minor effects on the upstream water flow regimes. It should however be emphasized that the model has major limitations, in particular the elevation model’s resolution. It is highly recommended to further develop the elevation model before further simulations on water discharges are made. The results from this study should only be considered as a first approximation where more detailed studies are needed to confirm that natural thresholds won’t result in major changes in upstream water flows.

The global move to more sustainable and renewable energy sources causes increased fluctuations in theelectric market. That fact combined with the Swedish regulations on micro producers make high levels ofself-use critical and have increased the interest in energy storage of energy from intermittent sources.Cooperation with Eksta AB have provided the opportunity to evaluate an innovative energy storage conceptfor a future exploitation area of around 17,2 hectares planned residential and urban area. This bachelorthesis studies the potential of using stormwater management ponds for small-scale energy storage in theform of pumped hydro energy storage (PHES). The focus is on storage of surplus energy from a solarenergy system designed for micro production and local energy supply. However, it also evaluates thepotential of using the equivalent dimensions for energy storage which storage level only change whenbuying or selling electricity at market prices for arbitrage purposes.Potential in the form of financial benefit and increased self-use of solar energy are studied through aquantitative methodology that, in the case of storing surplus energy from a solar system, use a simulationmodel developed for this thesis that takes Eksta´s contractual electric specifications into account. Toevaluate the case of energy storage for arbitrage a simulation model is used in the form of an algorithmbaseddrive strategy named “Optimal”, which has been recreated from research in the field of energy storageand drive strategies. The level of innovation is high on account of including such as energy additions to thestorage from rain water management, energy losses from dispersion of stored stormwater to surroundingground layers, it´s novel focus on a stormwater pond for energy storage, the rarely studied combination ofPHES and small scale solar systems and finally that the dimensions of the pump and turbine that is neededin PHES is based on PaT (pump as turbine) technology, allowing the reverse drive of a centrifugal pumpto operate as a turbine.Sensitivity analysis is included to increase the understanding of PHES-stormwater systems in the case of Eksta and as a concept for energy storage. The work also includes a brief examination of relevant regulationsin order to supply a wider perspective.The result shows that the implementation of a PHES-stormwater system during the years 2018 and 2019increased the self-use of generated solar energy by 28,59 % and provide the joint financial benefit of 5989SEK. The simulation model of energy storage for arbitrage during the years 2018 and 2019 resulted in thecombined financial benefit of 699 SEK when “Optimal” operation strategy is used and 678 SEK with apractically applicable operation strategy.The main conclusion is that PHES-stormwater systems as an energy storage for small-scale solar surplushas high potential to increase the self-use of solar energy but relatively low potential to increase the financialbenefits of small-scale solar systems. From the sensitivity analysis it can be concluded that the simulatedPHES-stormwater system is sensitive to small and medium ranged changes in storage capacity, efficiency,rate of dispersion, set electrical buying price and selectivity of which hours to empty the storage. This whilebeing generally insensitive to small and medium ranged variations in installed peak effect of the solar system,filling/emptying time and the relative size of the turbine compared to the pump.The conclusion from the simulation of arbitrage application is that the potential for financial benefit inthese circumstances is extremely low. The sensitivity analysis lead to the conclusion that the system issensitive to small and medium ranged variations in storage capacity, efficiency, filling/emptying time andmarginal operation costs.Besides the limited financial benefit, other potential hindrances may be the legality of connecting the systemelectrically, lack of financial benefits given to larger but still small-scale solar systems and the eventuality ofdisrupting the main function of the stormwater pond, which is purifying stormwater.

The Sustainable Development Goal (SDG) Target 6.2 aims at providing access to adequate and equitable sanitation and hygiene for all and to end open defecation by 2030. Yet, 47 % of the population in Bolivia lacked access to basic sanitation services in 2012. There is a risk of actors focusing on only the construction of toilet facilities, without looking at the need for related service required for a sustainable development. El Alto is a rapidly growing city in Bolivia where the sanitation service is expanding fast. In order to enhance knowledge about the sustainability of existing sanitation systems in El Alto and to give recommendations for future development, this sustainability assessment was conducted. Two sanitation systems in El Alto were assessed against five sustainability criteria, related to: 1) health, 2) environment, 3) technical function, 4) socio-culture (institutional and user related) and 5) economy. The conventional sanitation system with sewers and an alternative small-scale sanitation system with urine-diverting dry toilets (UDDTs) were selected as system options.  Results show that the "conventional system" entails higher health risks than the "UDDT system". For example, blockages in the main sewer lines cause overflows in the streets during rainy season when storm water gets mixed with potentially infectious wastewater. The UDDT system has a higher performance than the conventional system regarding the environment criterion, which is related to nutrients recovery and removal. Results related to the technical function criterion show that the conventional system has a better capacity to endure a change in quality or quantity of input products to the system. Both systems can handle the freezing temperatures in El Alto but the UDDT system has better resilience against climate change impacts such as flooding or drought events. The levels of complexity are reasonable in a local context for both systems. If assuming that the aspiration for flush toilets is as low in entire El Alto as in the area of investigation, results show that users of the UDDT system are more satisfied than uses of the conventional system. The dissatisfaction expressed by users of the conventional system mainly derives from malodors appearing during the wastewater overflows in the streets. The institutional capacity is stronger for the conventional system, making it harder for the UDDT system to expand. In addition, the UDDT system has difficulties with financing. Recommendations for future development are to inspect and renew the sewer network and to review and expand treatment capacity of the centralized treatment plant. Financial resources should be focused on the UDDT system where there is no sewer network. / Det globala hållbarhetsdelmålet 6.2 syftar till att senast 2030 säkerställa att alla har tillgång till fullgod och rättvis sanitet och hygien och att ingen behöver uträtta sina behov utomhus. År 2012 hade fortfarande 47% av Bolivias befolkning inte tillgång till acceptabel sanitet. Det finns en risk för att aktörer fokuserar på enbart snabb utbyggnation av toaletter, utan att ta hänsyn till behovet av relaterad service som krävs för en hållbar utveckling. För att sanitetssystem ska räknas som hållbara krävs, förutom att de skyddar hälsan, även att de är ekonomiskt genomförbara, socialt accepterade, tekniskt och institutionellt anpassade och att de skyddar miljön och hushåller med naturresurser. Med syftet att öka kunskapen kring hållbarheten av de existerande sanitetssystemen i El Alto, en snabbt växande stad i Bolivia, och för att ge rekommendationer till framtida utveckling av sanitetssystemen, genomfördes en hållbarhetsanalys av två existerande sanitetssystem i området. Det ena var det konventionella systemet tillhörande avloppsledningar och det andra var ett alternativt småskaligt system tillhörande urinsorterande torrtoaletter (UDDT).  Resultaten visar på att det ”konventionella systemet” innebär högre hälsorisker än ”UDDT systemet” för arbetarna och för boende som vistas i områdena där systemen finns. Det dåligt underhållna avloppssystemet var den avgörande faktorn, eftersom under regnperioder orsakas översvämningar av avloppsvatten på gatorna. Det konventionella systemet orsakar ungefär sex gånger så höga utsläpp av övergödande ämnen som UDDT systemet. UDDT systemet har potential att återvinna ungefär 64 % av inkommande kväve medan den motsvarande siffran för det konventionella systemet är endast 9%. Det konventionella systemet klarar bättre av förändringar i kvalitet och kvantitet av inflöden än UDDT systemet men båda systemen klarar av perioder då minusgrader inträffar. UDDT systemet förväntas, till skillnad från det konventionella systemet, att kunna hantera eventuell torka eller översvämning bättre som kan inträffa till följd av klimatförändringar. Till stor del på grund av de årligt förekommande översvämningarna av avloppsvatten på gatorna verkar användarna av det konventionella systemet vara mindre nöjda med sitt sanitetssystem än vad användarna av UDDT systemet verkar vara. Det gäller då att viljan att skaffa vattentoaletter är lika låg i hela El Alto som i området där intervjuer gjordes. Den institutionella kapaciteten är högre för det konventionella systemet än för UDDT systemet, vilket gör det svårare för UDDT systemet att expandera. Dessutom har UDDT systemet finansiella svårigheter.  Rekommendationer för framtida utveckling av sanitetssystemen i El Alto är delvis att underhålla och förnya avloppsledningarna och att expandera kapaciteten på det konventionella vattenreningsverket innan fler hushåll ansluts till ledningsnätet. Finansiella medel rekommenderas fokuseras på UDDT systemet i områden där avloppsledningar inte täcker. / El Objetivo de Desarrollo Sostenible 6 Meta 2 incluye que hasta el 2030, se logre el acceso a servicios de saneamiento e higiene adecuados y equitativos para todos y poner fin a la defecación al aire libre. Todavía, 47 % de la población en Bolivia carecía de acceso a saneamiento básico en 2012. Para alcanzar la meta sin comprometer los otros objetivos de desarrollo sostenible, la Alianza Sustenable de Saneamiento (SuSanA) identificó cinco criterios de sostenibilidad para el desarrollo de sistemas de saneamiento. Estos criterios son relacionados con: 1) salud e higiene, 2) medio ambiente y recursos naturales, 3) tecnología 4) asuntos financieros y económicos, y 5) aspectos socioculturales e institucionales (SuSanA, 2008). Con el objeto de mejorar el conocimiento sobre la sostenibilidad de los sistemas de saneamiento existentes en El Alto, una ciudad en rápido crecimiento en Bolivia, y para dar recomendaciones para el futuro desarrollo, se realizó una evaluación comparativa sobre la sostenibilidad de dos de los sistemas. Se evaluó el ”sistema convencional”, que tiene conexiones al alcantarillado y una planta de tratamiento centralizado. Tabmbien se evaluó el ”sistema UDDT”, que tiene baños secos ecológicos de los cuales existen en menor escala en El Alto. Los resultados muestran que existe alto riesgo para la salud derivados del alcantarillado del sistema convencional. Durante la temporada de lluvia suele ocurrir bloqueos taponamientos en la red del alcantarillado. Los bloqueos causan desbordes de aguas residuales en las calles que se mezclan con aguas pluviales. Los resultados muestran también que emisiones de eutrofización son aproximadamente seis veces más altas que el sistema convencional en comparación con el sistema UDDT. El potencial para el reciclaje de nitrógeno se puede estimar en 64%del sistema UDDT y solo 9%del sistema convencional. Los resultados sobre robustez muestran que el sistema convencional tiene una mejor capacidad para soportar un cambio en la calidad o cantidad de productos de entrada al sistema. Ambos sistemas pueden manejar las temperaturas de congelación en El Alto, pero el sistema UDDT tiene una mejor resistencia contra los impactos del cambio climático, como una inundación o una sequía. Existe insatisfacción que expresan los usuarios del sistema convencional debido a los desbordes anuales de aguas residuales en las calles. En general, los usarios del sistema UDDT estaban satisfechos. Parece que la aspiración de inodoros con descarga de agua es más baja en El Alto comparado con una ciudad más al sur de Bolivia. Por que la capacidad institucional es más fuerte para el sistema convencional comparado con el sistema UDDT, es más fácil para el sistema convencional expandirse. Además, los recursos financieros no están asegurados para el sistema UDDT. Las recomendaciones para el futuro desarrollo del situación de saneamiento es inspeccionar y renovar la red de alcantarillado existente y revisar y ampliar la capacidad de tratamiento de la planta de tratamiento centralizada antes de expandir la red de alcantarillado. Los recursos financieros deben centrarse en el sistema UDDT donde ya no existe una red de alcantarillado. / This thesis has been a pre-study linked to the Stockholm Environment Institute-led Bolivia WATCH program (contributing to more integrated sanitation and watershed management planning in Bolivia), and particularly to its sub-project ‘Comparative sustainability assessment of sanitation services’, which aims at generating a fair and comprehensive comparison between different sanitation system approaches. The comparative assessment, developed in collaboration with RISE, AguaTuya and Unicef, is expected to provide insights and guide future sanitation investments in Bolivia, but also highlight where both conventional and alternative approaches have improvement potential from a sustainability perspective in the Bolivian setting.