This dissertation consists of four papers concerning impacts of zinc orthophosphate (ZOP) inhibitor on iron, copper and lead release in a changing water quality environment. The mechanism of zinc orthophosphate corrosion inhibition in drinking water municipal and home distribution systems and the role of zinc were investigated. Fourteen pilot distribution systems (PDSs) which were identical and consisted of increments of PVC, lined cast iron, unlined cast iron and galvanized steel pipes were used in this study. Changing quarterly blends of finished ground, surface and desalinated waters were fed into the pilot distribution systems over a one year period. Zinc orthophosphate inhibitor at three different doses was applied to three PDSs. Water quality and iron, copper and lead scale formation was monitored for the one year study duration. The first article describes the effects of zinc orthophosphate (ZOP) corrosion inhibitor on surface characteristics of iron corrosion products in a changing water quality environment. Surface compositions of iron surface scales for iron and galvanized steel coupons incubated in different blended waters in the presence of ZOP inhibitor were investigated using X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) / Energy Dispersive X-ray Spectroscopy (EDS). Based on surface characterization, predictive equilibrium models were developed to describe the controlling solid phase and mechanism of ZOP inhibition and the role of zinc for iron release. The second article describes the effects of zinc orthophosphate (ZOP) corrosion inhibitor on total iron release in a changing water quality environment. Development of empirical models as a function of water quality and ZOP inhibitor dose for total iron release and mass balances analysis for total zinc and total phosphorus data provided insight into the mechanism of ZOP corrosion inhibition regarding iron release in drinking water distribution systems. The third article describes the effects of zinc orthophosphate (ZOP) corrosion inhibitor on total copper release in a changing water quality environment. Empirical model development was undertaken for prediction of total copper release as a function of water quality and inhibitor dose. Thermodynamic models for dissolved copper based on surface characterization of scale that were generated on copper coupons exposed to ZOP inhibitor were also developed. Surface composition was determined by X-ray Photoelectron Spectroscopy (XPS). The fourth article describes the effects of zinc orthophosphate (ZOP) corrosion inhibitor on total lead release in a changing water quality environment. Surface characterization of lead scale on coupons exposed to ZOP inhibitor by X-ray Photoelectron Spectroscopy (XPS) was utilized to identify scale composition. Development of thermodynamic model for lead release based on surface analysis results provided insight into the mechanism of ZOP inhibition and the role of zinc.

This study evaluated the effects of orthophosphate (OP) inhibitor addition on iron, copper, and lead corrosion on coupons exposed to different blends of groundwater, surface water, and desalinated seawater. The effectiveness of OP inhibitor addition on iron, copper, and lead release was analyzed by statistical comparison between OP treated and untreated pilot distribution systems (PDS). Four different doses of OP inhibitor, ranging from zero (control) to 2 mg/L as P, were investigated and non-linear empirical models were developed to predict iron, copper, and lead release from the water quality and OP doses. Surface characterization evaluations were conducted using X-ray Photoelectron Spectroscopy (XPS) analyses for each iron, galvanized steel, copper, and lead/tin coupon tested. Also, a theoretical thermodynamic model was developed and used to validate the controlling solid phases determined by XPS. A comparison of the effects of phosphate-based corrosion inhibitor addition on iron, copper, and lead release from the PDSs exposed to the different blends was also conducted. Three phosphate-based corrosion inhibitors were employed; blended orthophosphate (BOP), orthophosphate (OP), and zinc orthophosphate (ZOP). Non-linear empirical models were developed to predict iron, copper, and lead release from each PDS treated with different doses of inhibitor ranging from zero (control) to 2 mg/L as P. The predictive models were developed using water quality parameters as well as the inhibitor dose. Using these empirical models, simulation of the water quality of different blends with varying alkalinity and pH were used to compare the inhibitors performance for remaining in compliance for iron, copper and lead release. OP inhibitor addition was found to offer limited improvement of iron release for the OP dosages evaluated for the water blends evaluated compared to pH adjustment alone. Empirical models showed increased total phosphorus, pH, and alkalinity reduced iron release while increased silica, chloride, sulfate, and temperature contributed to iron release. Thermodynamic modeling suggested that FePO4 is the controlling solid that forms on iron and galvanized steel surfaces, regardless of blend, when OP inhibitor is added for corrosion control. While FePO4 does not offer much control of the iron release from the cast iron surfaces, it does offer protection of the galvanized steel surfaces reducing zinc release. OP inhibitor addition was found to reduce copper release for the OP dosages evaluated for the water blends evaluated compared to pH adjustment alone. Empirical models showed increases in total phosphorus, silica, and pH reduced copper release while increased alkalinity and chloride contributed to copper release. Thermodynamic modeling suggested that Cu3(PO4)2·2H2O is the controlling solid that forms on copper surfaces, regardless of blend, when OP inhibitor is added for corrosion control. OP inhibitor addition was found to reduce lead release for the OP dosages evaluated for the water blends evaluated compared to pH adjustment alone. Empirical models showed increased total phosphorus and pH reduced lead release while increased alkalinity, chloride, and temperature contributed to lead release. Thermodynamic modeling suggested that hydroxypyromorphite is the controlling solid that forms on lead surfaces, regardless of blend, when OP inhibitor is added for corrosion control. The comparison of phosphate-based inhibitors found increasing pH to reduce iron, copper, and lead metal release, while increasing alkalinity was shown to reduce iron release but increase copper and lead release. The ZOP inhibitor was not predicted by the empirical models to perform as well as BOP and OP at the low dose of 0.5 mg/L as P for iron control, and the OP inhibitor was not predicted to perform as well as BOP and ZOP at the low dose of 0.5 mg/L as P for lead control. The three inhibitors evaluated performed similarly for copper control. Therefore, BOP inhibitor showed the lowest metal release at the low dose of 0.5 mg/L as P for control of iron, copper, and lead corrosion.

No description available.

Les milieux oligotrophes sont pauvres en éléments nutritifs. En utilisant la technologie de séquençage à haut débit, on a étudié la diversité bactérienne dans trois environnements oligotrophes différents, y compris A. sâbles du désert, B. sâbles dans les tempêtes de l'Asie et C. l’eau et biofilms dans les réseaux de distribution d'eau potable.A. Le désert représente 30% de la surface de la terre. Les conditions de vie dans ces environnements sont un réel défi pour les micro-organismes à cause de nombreux facteurs limitants : peu d’eau et/ou de carbone disponible, une variation importante de température et une forte exposition aux irradiations UV. Le but de cette recherche est donc d’étudier la diversité bactérienne à la surface du sable du désert Taklemaken et du désert de Gobi en utilisant la technologie de séquençage à haut débit. Nos résultats ont révélé une grande diversité bactérienne dans le sol du désert comparable à d'autres types de sols. En outre, nous avons observé une corrélation positive entre la richesse bactérienne et le rapport C/N du sol.B. Les tempêtes de sable d'Asie se produisent presque toujours au printemps, elles sont générées dans les régions arides d'Asie telles que le désert Taklamaken et le désert de Gobi. L'arrivée des tempêtes de sable pourrait largement modifier l'environnement de l'air dans ces régions sous l’effet du vent, surtout dans les villes asiatiques qui sont le plus souvent touchées. Nos travaux visent à étudier la modification de la composition et la diversité des bactéries associées aux particules au moment de tempête de sable en Asie par la technologie de séquençage à haut débit. Nos résultats ont démontré que les compositions des bactéries associées aux particules sont modifiées pendant les tempêtes, en particulier, la proportion des Proteobacteria qui augmentent les jours de tempête. Nous avons signalé neuf genres bactériens détectés en plus pendant les jours de tempêtes, cela nécessite des études plus approfondies.C. Après avoir analysé la population bactérienne dans les tempêtes de sable, et celles des déserts, nous poursuivons notre objectif de recherche à un environnement aquatique. Nous avons suivi le flux d'eau provenant de l'usine d'Orly (DW-A) à l'entrée du réservoir (DW-B), et à la sortie du réservoir (DW-C). Nous avons constaté une forte variation de la communauté bactérienne, dans DW-A et DW-B, les bactéries prédominantes appartiennent aux populations des Betaproteobacteria, puis nous avons observé une conversion vers la population de Alphaproteobacteria dans DW-C. Le DW-C a montré une forte similitude avec un échantillon de biofilm (BF-C), ce qui suggère l'effet important du biofilm sur la modification des communautés bactériennes dans l'eau lors de la distribution. / Oligotrophic ecosystems can be loosely defined as environments that exhibit low ambient nutrient levels. During my thesis, I used 454 DNA pyrosequencing of partial 16S rDNA to explore the bacterial diversity in three different oligotrophic environments, including A. surface desert soil, B. Asian sandstorm dust and C. a section of the city of Paris’s drinking water distribution system.A. Arid regions represent nearly 30% of the Earth’s terrestrial surface. The living conditions at the surface of deserts are a challenge for microorganisms, as there is little available water and/or carbon, a very large range of temperatures and high exposure to UV irradiation from the Sun. In surface sand samples from two large Asian deserts, unexpectedly large bacterial diversity residing was revealed. Sequences belonging to the Firmicutes, Proteobacteria, Bacteroidetes and Actinobacteria phyla were the most abundant. An increase in phylotype numbers with increasing C/N ratio was noted, suggesting a possible role in the bacterial richness of these desert sand environments.B. Desert sandstorms are a meteorological phenomenon which have been postulated affect the Earth's climate and public health. We examined the particle-associated (dust and sand-associated) bacterial populations of atmospheric sand in the absence (as control) and presence of sandstorms in five Asian cities. Greater than 90% of the sequences can be classified as representing bacteria belonging to four phyla: Proteobacteria, Bacteriodetes, Actinobacteria and Firmicutes. Principal component analyses showed that the sandstorm-associated bacterial populations were clustered by sampling year, rather than location. Members belonging to nine bacterial genera (Massilia, Planococcus, Carnobacterium, Planomicrobium, Pontibacter, Pedobacter, Lysobacter, Sanguibacter, Ohtaekwangia) were observed to increase in sand-associated samples from sandstorms, versus the controls. C. We characterized the bacterial communities in three water and three biofilm samples from one part of the Parisian drinking water distribution system. A dramatic change in bacterial population in the water during flow through the distribution system from the water treatment plant to the exit from the reservoir was found. The richness of the bacterial population was reduced from the water treatment plant to the reservoir (from 336 to 165 OTUs for water samples leaving the reservoir and from 947 to 275 for biofilm samples in the network). Several OTUs belonging to pathogenic genera were detected in our samples, mostly in the biofilm samples, thus suggesting that the biofilms may be an important source of bacteria during water distribution to the consumers.

Oligotrophic ecosystems can be loosely defined as environments that exhibit low ambient nutrient levels. During my thesis, I used 454 DNA pyrosequencing of partial 16S rDNA to explore the bacterial diversity in three different oligotrophic environments, including A. surface desert soil, B. Asian sandstorm dust and C. a section of the city of Paris's drinking water distribution system.A. Arid regions represent nearly 30% of the Earth's terrestrial surface. The living conditions at the surface of deserts are a challenge for microorganisms, as there is little available water and/or carbon, a very large range of temperatures and high exposure to UV irradiation from the Sun. In surface sand samples from two large Asian deserts, unexpectedly large bacterial diversity residing was revealed. Sequences belonging to the Firmicutes, Proteobacteria, Bacteroidetes and Actinobacteria phyla were the most abundant. An increase in phylotype numbers with increasing C/N ratio was noted, suggesting a possible role in the bacterial richness of these desert sand environments.B. Desert sandstorms are a meteorological phenomenon which have been postulated affect the Earth's climate and public health. We examined the particle-associated (dust and sand-associated) bacterial populations of atmospheric sand in the absence (as control) and presence of sandstorms in five Asian cities. Greater than 90% of the sequences can be classified as representing bacteria belonging to four phyla: Proteobacteria, Bacteriodetes, Actinobacteria and Firmicutes. Principal component analyses showed that the sandstorm-associated bacterial populations were clustered by sampling year, rather than location. Members belonging to nine bacterial genera (Massilia, Planococcus, Carnobacterium, Planomicrobium, Pontibacter, Pedobacter, Lysobacter, Sanguibacter, Ohtaekwangia) were observed to increase in sand-associated samples from sandstorms, versus the controls. C. We characterized the bacterial communities in three water and three biofilm samples from one part of the Parisian drinking water distribution system. A dramatic change in bacterial population in the water during flow through the distribution system from the water treatment plant to the exit from the reservoir was found. The richness of the bacterial population was reduced from the water treatment plant to the reservoir (from 336 to 165 OTUs for water samples leaving the reservoir and from 947 to 275 for biofilm samples in the network). Several OTUs belonging to pathogenic genera were detected in our samples, mostly in the biofilm samples, thus suggesting that the biofilms may be an important source of bacteria during water distribution to the consumers.

Das Auftreten von Braunwasser in Trinkwasserverteilungsnetzen ist eine Beeinträchtigung der Trinkwasserqualität, die durch mobilisierte partikuläre Ablagerungen verursacht wird. Die Partikel gelangen durch verschiedene Prozesse, wie z. B. der Korrosion metallischer Leitungen und den Eintrag am Wasserwerk, kontinuierlich in sehr geringen Massenströmen in das Rohrnetz. Durch die Akkumulation der Partikel an Rohroberflächen können sich Ablagerungsmengen bilden, die bei ansteigenden Strömungsgeschwindigkeiten resuspendiert werden und zu unerwünschten Braunwassererscheinungen führen. Die vorliegende Arbeit behandelt die experimentelle Untersuchung des Transportes von Partikeln, die für Trinkwassernetze typisch sind, in Rohrströmungen. Es werden Einflussfaktoren identifiziert, die für den Partikeltransport von Bedeutung sind. Ein neu entwickeltes dynamisches Modell beschreibt den Transport von Partikeln und die Ablagerungsbildung in Rohrströmungen und vermaschten Rohrnetzen. Das Modell wurde in einer Anwendersoftware implementiert und an einem Trinkwasserverteilungsnetz für das Nachvollziehen der beobachteten Ablagerungsbildung eingesetzt. Im Vergleich zu bestehenden dynamischen Modellen werden partikelbezogene Prozesse unter Berücksichtigung der für trinkwasserbürtige Partikel und Ablagerungen typischen Eigenschaften mathematisch genauer beschrieben. Stationäre und dynamische Ereignisse bezüglich Wasserqualität und Ablagerungsbildung können jetzt durch die Berücksichtung zahlreicher zeitabhängiger Einflussfaktoren nachvollzogen werden. / The occurrence of discoloured water in drinking water distribution systems is a disturbance of the water quality, which is induced by mobilised particulate deposits. Different processes result in the continuous entry of small mass flow rates of particles into the piping, for instance the corrosion of metallic pipes as well as the entry at the water works outlet. By the accumulation of these particles, significant amounts of deposits can be formed and at higher flow rates be resuspended, which leads to unwanted events with discoloured water. This study examines the experimental investigation of the transport of particles, which are typical for drinking water distribution systems, in pipe flow. Influencing factors are identified, which are of importance for the particle transport. With a newly developed model, the transport of particles and the deposit formation in pipe flow and in piping is described. The model is implemented into a software application and deployed at a drinking water distribution system to understand the observed deposit formation. In comparison with existent dynamic water quality models, particle-related processes are described mathematically in more details, under consideration of characteristics typical for particles and deposits in drinking water distribution systems. Hence, observed steady-state and dynamic events can be followed using several influencing time-dependent factors.

Das Auftreten von Braunwasser in Trinkwasserverteilungsnetzen ist eine Beeinträchtigung der Trinkwasserqualität, die durch mobilisierte partikuläre Ablagerungen verursacht wird. Die Partikel gelangen durch verschiedene Prozesse, wie z. B. der Korrosion metallischer Leitungen und den Eintrag am Wasserwerk, kontinuierlich in sehr geringen Massenströmen in das Rohrnetz. Durch die Akkumulation der Partikel an Rohroberflächen können sich Ablagerungsmengen bilden, die bei ansteigenden Strömungsgeschwindigkeiten resuspendiert werden und zu unerwünschten Braunwassererscheinungen führen. Die vorliegende Arbeit behandelt die experimentelle Untersuchung des Transportes von Partikeln, die für Trinkwassernetze typisch sind, in Rohrströmungen. Es werden Einflussfaktoren identifiziert, die für den Partikeltransport von Bedeutung sind. Ein neu entwickeltes dynamisches Modell beschreibt den Transport von Partikeln und die Ablagerungsbildung in Rohrströmungen und vermaschten Rohrnetzen. Das Modell wurde in einer Anwendersoftware implementiert und an einem Trinkwasserverteilungsnetz für das Nachvollziehen der beobachteten Ablagerungsbildung eingesetzt. Im Vergleich zu bestehenden dynamischen Modellen werden partikelbezogene Prozesse unter Berücksichtigung der für trinkwasserbürtige Partikel und Ablagerungen typischen Eigenschaften mathematisch genauer beschrieben. Stationäre und dynamische Ereignisse bezüglich Wasserqualität und Ablagerungsbildung können jetzt durch die Berücksichtung zahlreicher zeitabhängiger Einflussfaktoren nachvollzogen werden. / The occurrence of discoloured water in drinking water distribution systems is a disturbance of the water quality, which is induced by mobilised particulate deposits. Different processes result in the continuous entry of small mass flow rates of particles into the piping, for instance the corrosion of metallic pipes as well as the entry at the water works outlet. By the accumulation of these particles, significant amounts of deposits can be formed and at higher flow rates be resuspended, which leads to unwanted events with discoloured water. This study examines the experimental investigation of the transport of particles, which are typical for drinking water distribution systems, in pipe flow. Influencing factors are identified, which are of importance for the particle transport. With a newly developed model, the transport of particles and the deposit formation in pipe flow and in piping is described. The model is implemented into a software application and deployed at a drinking water distribution system to understand the observed deposit formation. In comparison with existent dynamic water quality models, particle-related processes are described mathematically in more details, under consideration of characteristics typical for particles and deposits in drinking water distribution systems. Hence, observed steady-state and dynamic events can be followed using several influencing time-dependent factors.

Att ha ständig tillgång till ett hälsosamt, rent och gärna gott dricksvatten tas idag ofta som självklart av många människor i Sverige. Sveriges sammanlagda nybildning av vatten innebär idag inga problem för dricksvattenförsörjningen om man bortser från ojämn fördelning av vattentillgångar samt lokala kvalitetsproblem. Många områden förses med dricksvatten från något av landets omkring 2000 vattenverk. En del får sitt vatten från enskilda brunnar, medan vissa har löst vattenfrågan tillsammans med andra i samfälligheter. Vissa samfälligheter som inte har någon egen vattentäkt kan ibland förses med vatten från ett allmänt distributionsnät. I Vaxholms kommun finns nära ett 30-tal samfälligheter som får sitt vatten från Görvälnverket i Järfälla kommun vilket ägs och drivs av kommunalförbundet Norrvatten AB. Behandlat dricksvatten distribueras vidare av Norrvatten AB. I Vaxholms kommun är Vaxholmsvatten AB/ Roslagsvatten AB VA-huvudman och förvaltar kommunens allmänna VA-anläggning. Roslagsvatten AB levererar vatten till vattenkonsumenter som är anslutna till det allmänna VA-nätet i Vaxholms kommun, men bolaget levererar även dricksvatten till nämnda samfälligheter. Vattenverket behandlar (renar) det så kallade råvattnet från vattentäkten (i detta fall Mälaren) för att åstadkomma ett kvalitetsmässigt bra dricksvatten sett ur såväl kemisk som ur mikrobiologisk synvinkel. Kan då dricksvattensamfälligheterna slå sig till ro med att de har ett dricksvatten av god kvalitet? SRMH bedriver kontroll och tillsyn av dricksvattensamfälligheterna och deras distributionsanläggningar. SRMH har gjort sina första pilotinspektioner hos samfälligheterna och uppmärksammat ett antal förmodade brister med vissa rutiner och installationer. I forskningsfältet kring distributionsanläggningar för dricksvatten studeras bland annat faktorer som påverkar mikrobiologisk förekomst och tillväxt i distributionsanläggningar. Mot bakgrund av utvalda delar ur detta forskningsfält har jag skapat ett analytiskt ramverk för att söka värdera mikrobiologiska risker i samfälligheternas distributionsanläggningar. Förutom detta görs några typer av mikrobiologiska analyser för att jämföra med uppskattad risk. Förutom protokoll från SRMH:s inspektioner av samfälligheterna görs små intervjuer av vattenkonsumenter och samfällighetsansvariga. För att se var eventuella kvalitetsproblem uppstår används sekundärdata från Norrvatten som beskriver kvalitet efter vattenverkets behandling och kvalitet vid ett vattentorn på ”halva vägen” samt vid en referenspunkt i Vaxholm. Relevant dricksvattenjuridik studeras också för att ta reda på vem som ansvarar för vad samt för att se vilka kvalitetskrav som är relevanta avseende samfälligheterna. Resultatet antyder försiktigt att riskerna men även vattentemperaturen samt den mikrobiologiska vattenkvaliteten (odlingsbara mikroorganismer) i undersökningen till viss del skiljer mellan olika typer av samfälligheter. För samfälligheter med året-runt-vatten verkar problemen vara mindre, medan för samfälligheter som endast har sommarvatten verkar det finnas fler risker. Det senare verkar även gälla för samfälligheter där fritidsbostäder ingår. Skillnader i antal långsamväxande mikroorganismer mellan olika samfällighetstyper är dock mer osäkra. Kvalitetsreglerna avseende mikrobiologi i samfällighetsnätet och i det allmänna nätet styrs av livsmedelsverkets föreskrifter och EU:s dricksvattendirektiv och alla parter måste försäkra sig om att kvalitetskraven uppfylls inom respektive distributionsnät. Återströmning av vatten från samfälligheter till den allmänna distributionsanläggningen verkar inte kunna regleras av lagen om allmänna vattentjänster och därmed ej heller av det lokala regelverket ABVA för Vaxholm. Enligt min tolkning av regelverket är respektive ägare av distributionsnäten ansvariga för om kvaliteten påverkas i det egna nätet när/om återströmning sker från mottagande part. I diskussionsdelen görs även jämförelser avseende temperatur och mikrobiologiska parametrar mellan de olika typerna av studerade samfälligheter och Norrvattens perifera kommuner för att se om det finns några skillnader. / Continuous access to healthy, clean and good-tasting drinking-water is perceived as obvious for many people in Sweden. The total regeneration of water is currently not a problem in Sweden if uneven distribution and local quality problems are not accounted for. Many regions are supplied with drinking water from one of Sweden’s around 2000 water treatment plants. Other water consumers get their water from private wells, while others get water access via community-owned distribution systems. Sometimes communities that do not have their own water supply can get water supply through a public distribution system. In the municipality of Vaxholm almost 30 small communities get their water from the water treatment plant (WTP) Görvälnverket, which is owned and operated by a municipal association called Norrvatten AB. Norrvatten AB redistributes the treated drinking water. In Vaxholm, Roslagsvatten AB is the legal principal of water and sewage. Roslagsvatten AB distributes water to water consumers in the municipality of Vaxholm. The WTP treats (purifies) the surface water from the water source (in this case Mälaren) in order to provide a good quality drinking water seen from both a chemical and microbiological point of view. Under these circumstances, could the water communities be complacent that they have a good quality drinking water? Södra Roslagens Miljö- och hälsoskyddskontor (SRMH) is the local health protection agency responsible for control and enforcement of drinking water communities in Vaxholm. After having performed pilot inspections at the water communities, SRMH drew attention to some assumed risks and deficiencies with routines and water pipe installations. In the drinking water distribution systems research field, factors influencing microbiological presence and growth are investigated. In the view of selected portions from this research field, I have created an analytical framework to be able to evaluate some kind of microbiological risks in the communities’ water distribution systems. Besides this, some microbiological analyzes are made to compare with assessed risk. In addition to studied protocols from inspections of the communities, some minor interviews are made with water consumers and persons responsible for plumbing in the communities. To assess whether potential quality problems occur, secondary historical quality analysis data from Norrvatten AB is used. Quality data from directly after treatment at the WTP, from a water tower “halfway” to Vaxholm, and from a reference location in Vaxholm is used. Swedish and European Union legal framework of relevance regarding drinking water is studied to find out relevant legal quality requirements with regards to the communities. The result gently suggests that identified risks but also water temperature and investigated microbiological quality (culturable microorganisms; HPC counts, 22 °C, 3 days) in the study to some extent differ between different types of communities. For communities with full-year water supply, the problems seem to be less. On the contrary, for communities with supply only during summer, problems seem to be greater. Problems also seem to exist for communities where holiday residences exist. Differences in the number of slower growing microorganisms (HPC counts, 22 °C, 7 days) between community types is more uncertain. The microbiological quality of drinking water is regulated by Swedish national regulations and by European Union’s drinking water directive. All parties must ensure that quality standards are met in each distribution network. Backflow of water from communities’ distribution networks does not seem to be regulated by the Swedish law on public water services and thus neither by the local regulatory called “ABVA” for Vaxholm. According to my interpretation of the regulations, the respective owners of the distribution networks are responsible for if quality is adversely affected in its own network if backflow occurs from the receiving party. In the discussions chapter, temperature and HPC counts are compared between studied communities and Norrvatten’s peripheral municipalities to assess if differences exist.