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  • 1.
    Herrmann, Inga
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Vidal, Brenda
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Hedström, Annelie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Discharge of indicator bacteria from on-site wastewater treatment systems2017In: Desalination and Water Treatment, ISSN 1944-3994, E-ISSN 1944-3986, Vol. 91, p. 365-373Article in journal (Refereed)
    Abstract [en]

    Small-scale on-site wastewater treatment facilities present the risk of microbial pollution of groundwaterused for drinking water and surface water used for recreational purposes. This study assessedthe discharge of indicator bacteria, total coliform, Escherichia coli, intestinal enterococci and Clostridiumperfringens, by flow-proportional sampling from 12 full-scale on-site treatment systems featuringbiological treatment units (mainly sand filters) and alkaline filter beds for phosphorus treatment(P-filters). Correlations of effluent bacterial concentrations with pH, total and dissolved organic carbon,filter age and hydraulic load were evaluated. The bacterial concentrations in the effluents ofthe sand filters were considerable. The concentrations for excellent bathing water quality set in theEU bathing water directive, 200 and 500 colony forming units (cfu)/100 mL for intestinal enterococciand E. coli, respectively, were exceeded in three (intestinal enterococci) and one (E. coli) of the eightinvestigated sand filters. In one of the sand filters, effluent E. coli concentrations were high althoughno obvious malfunction of the filter was observed. In the effluent from the other investigated biologicaltreatment units (a trickling fibre filter, two units with attached growth treatment and one aeratedactivated sludge technique), bacterial concentrations were very high (75,000 cfu/100 mL of Clostridiumperfringens and 85,000 cfu per 100 mL of total coliform), possibly because of a shorter retention time ofthe wastewater in these facilities, missing aeration and little time between start-up and measurements.Three and four of the nine investigated P-filters exceeded excellent bathing water quality in coastalwaters as stipulated by the EU bathing water directive in respect of E. coli and intestinal enterococci,respectively.

  • 2.
    Herrmann, Inga
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Vidal, Brenda
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Hedström, Annelie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Slutrapport av projekten "Fosforfällor för små avlopp - hur länge fungerar de?" och "Bakterieutsläpp från små avlopp"2017Report (Other academic)
    Abstract [sv]

    Små enskilda avloppsanläggningar i Sverige består ofta av en slamavskiljare med markbädd eller infiltration. I områden med hög skyddsnivå har på senare år ett stort antal fosforfilter installerats. Syftet med denna studie var att undersöka markbäddars och fosforfilters förmåga att reducera halten bakterier och fosfor i avloppsvattnet. Avloppsanläggningar i Västerbotten, Norrbotten och Norrtälje kommun identifierades och inspekterades. Prover togs mellan september 2015 och september 2016 från tolv avloppsanläggningar, åtta markbäddar och nio fosforfilter. Provtagning skedde minst tre gånger vid varje anläggning, och varje provtagningstillfälle varade cirka 3–4 timmar då det togs två stickprover från slamavskiljarens tredje kammare alternativt från fördelningsbrunnen, samt två flödesproportionella samlingsprover efter den biologiska reningen (det vill säga efter markbädden eller biosteget i minireningsverket) och efter fosforfiltret. I proverna mättes pH, mängden suspenderat material, temperatur, indikatorbakterier (E. coli, totala koliforma, intestinala enterokocker och Clostridium perfringens/C. perfringens), halten löst och total fosfor, halten löst och totalt organiskt kol (DOC, TOC) samt BOD. Spårämnesförsök genomfördes i tre fosforfilter med färgen rhodamin.

     

    22 av de 34 inspekterade avloppsanläggningarna (65 procent) lämpade sig inte för flödesproportionell provtagning, vilket visar på svårigheten med att kontrollera funktionen av små avloppsanläggningar med hjälp av provtagning. Nio av 21 inspekterade fosforfilter lämpade sig inte för provtagning på grund av att det inte fanns något vattenflöde genom filtret, vilket indikerar att filtren inte fungerade som avsett.

     

    I utloppen från tre av de åtta undersökta markbäddarna var medelkoncentrationen intestinala enterokocker högre än badvattendirektivets gränsvärde för inlandsvatten med utmärkt vattenkvalitet. För E. coli-koncentrationer var detta fallet bara i en enda markbädd, men detta trots att det utgående vattnet var klart och hade TOC koncentrationer på en acceptabel nivå. Det här visar att bakteriekoncentrationer kan vara höga även om markbädden ser ut att fungera.

     

    Efter de nio undersökta fosforfiltren var bakteriekoncentrationen särskilt hög efter fosforfilter utan markbädd som förbehandlingssteg. I flera fall översteg koncentrationerna gränsvärdet för utmärkt badvattenkvalitet enligt badvattendirektivet; i tre fosforfilter med avseende på E. coli och i fyra fosforfilter med avseende på intestinala enterokocker. Medelkoncentrationen av E. coli-bakterier reducerades signifikant (p = 0,044) i fosforfiltren, vilket tyder på att fosforfilter kan tjäna som ett reningssteg som ytterligare reducerar bakterier. Detta kunde dock inte påvisas för intestinala enterokocker, totala koliforma eller C. perfringens. Koncentrationen av koliforma bakterier var beroende av fosforfiltrets hydrauliska belastning, vilket tyder på att flödesregimen och vattnets uppehållstid i filtret är viktiga parametrar som påverkar bakteriereduktionen. Både för markbäddarna och för fosforfiltren fanns ett samband mellan koncentrationen av indikatorbakterierer och utloppskoncentrationen av TOC och DOC, vilket tyder på att en högre halt av organiskt kol i utgående vatten visar på en sämre bakteriereduktion.

     

    Två av de åtta undersökta markbäddarna visade på god fosforreduktion som uppgick till 70 procent (slamavskiljare exkluderad) vilket krävs vid normal skyddsnivå enligt nuvarande regelverk. Fosforreduktionen i tre andra markbäddar var lägre (21–29 procent). Övriga tre markbäddar kunde inte betraktas vara godtagbara reningsanläggningar eftersom det troligtvis skedde en betydande inströmning av vatten in i dessa markbäddar med utspädning som följd.

     

    Den högsta koncentrationen av fosfor i utgående vatten från en markbädd var omkring 15 mg/l. Dock var utgående fosforkoncentrationer från de undersökta markbäddarna endast i fyra av åtta fall så höga (>2mg/l) att ett efterföljande fosforfilter skulle vara meningsfullt. Därför är det viktigt att markbäddar med efterföljande rening i fosforfilter byggs med tätskikt för att undvika in- och exfiltration.

     

    Fem av de nio utvärderade fosforfiltren reducerade (tillsammans med den biologiska förbehandlingen) mer än 90 procent av den inkommande fosforn från slamavskiljaren. Det betyder att de klarade reningskravet för fosfor i områden med hög skyddsnivå. Två av filtren uppvisade utgående koncentrationer av totalfosfor på 1–3 mg/l och den högsta utgående medelkoncentrationen var 4,4 mg/l. I anläggningar med biologiska behandlingsenheter som inte var markbäddar stod fosforfiltren för merparten av fosforavskiljningen.

     

    Fosforreduktionen i fosforfiltren korrelerade med pH i utgående vatten från filtren, med en beräknad korrelationskoefficient på 74 procent, vilket indikerar att pH kan användas som indikator på filtrets funktion. Dock visade resultaten också att fosforfilter med liknande pH-värde (nära 9) kan skilja sig mycket med avseende på fosforreduktion.

     

    Koncentration av organiskt kol eller fosfor i inkommande vatten till fosforfiltren kunde inte korreleras till filtrens fosforreducerade förmåga. En hög hydraulisk belastning påverkade dock fosforfiltrens funktion negativt. Liknande effekt hade filtrets ålder, om än inte lika tydligt. De preliminära resultaten från spårämnesförsöken indikerar att de fosforfilter som hade längre uppehållstid också hade högre fosforavskiljning än filter med kortare uppehållstid.

  • 3.
    Herrmann, Inga
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Vidal, Brenda
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Hedström, Annelie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Treatment of Phosphorus and Bacteria in Filters used for On-Site Sanitation in Cold Climate2016Conference paper (Refereed)
    Abstract [en]

    Swedish rural on-site wastewater facilities need to reduce the phosphorus (P) concentrations in the wastewater to prevent eutrophication of the Baltic Sea, as well as the bacteria concentrations to comply with EU standards for bathing water quality. The aim of this study was to investigate two different on-site filter systems at full-scale, sand filters and (often subsequently used) alkaline P filters towards their performance to treat P and bacteria from domestic wastewater. Flow-proportional composite samples were taken from five sand filter beds and two P filters. Four of the five investigated sand filters considerably reduced the concentration of total P in the wastewater. However, infiltrating soil / ground water may have diluted the effluents. The investigated P filters varied in performance. While one of them treated P effectively, the other one performed poorly, probably due to old age and clogging. Low inlet P concentrations impeded the general assessment of the P filters’ efficiency. Concentrations of four indicator bacteria, intestinal enterococci, E. coli, total coliforms and C. perfringens, were considerably reduced in four of the five investigated sand filter beds. Bacteria removal in the two investigated P filters was difficult to assess because of low bacteria concentrations in the influents.

  • 4.
    Vidal, Brenda
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    On-site sanitation systems - An integrated assessment of treatment efficiency and sustainability2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Small on-site sanitation systems for wastewater collection and treatment are prevalent in suburban and rural areas in many countries. However, these systems often underperform, causing potential impact to the receiving waters and increasing the risks to public health, thus hindering the overall sustainability of the systems. Understanding the different sustainability dimensions and trade-offs between assessment indicators can support the planning of sustainable on-site sanitation systems for a specific context. The overall aim of this thesis was to evaluate the sustainability and function of on-site sanitation systems by defining a set of indicators to assess on-site sanitation options and estimating them for different scenarios, and by investigating the treatment efficiency of on-site facilities for domestic wastewater treatment in a field study. Particular attention was given to the removal of phosphorus (P) and indicator bacteria due to their relevance in terms of eutrophication risk and public-health concern.

    In a multi-criteria approach, twelve indicators were defined to assess nine on-site sanitation systems. A reference group representing stakeholders’ views assigned weights to express the relative importance of each indicator. The reference group assigned the highest weights to the indicators robustness, risk of pathogen discharge and nutrient removal. Assessing the robustness proved to be challenging, as there is a gap between how the sanitation systems are expected to perform based on their design, and how they actually perform in practice, mainly due to incorrect construction, operation and maintenance. The discriminating power of the indicators was calculated using the entropy method, which showed that the indicators energy recovery and capital cost had little impact in the final ranking of the alternatives. A sustainability ranking was obtained by using the method ELECTRE III. A scenario analysis based on different settings of interest based on socio-economic and geographical factors was done to evaluate the changes in the ranking of alternatives. Overall, the greywater–blackwater separation system ranked the highest in the baseline scenario and when nutrient-related indicators were important (Scenario 2), together with the urine diversion system. The sand filter and drain field were the most sustainable options when nutrient removal and recycling was not important (Scenario 1), and (in combination with chemical P-removal) when the indicators related to energy and climate change had the highest weights (Scenario 3). In terms of P-removal, chemical removal outranked the alkaline P-filter.

    In a field study, the effluent wastewater from twelve on-site wastewater treatment facilities with sand and alkaline P-filters was evaluated in terms of removal and discharge of organic content, total and dissolved phosphorus, and indicator bacteria (E. coli, total coliforms, intestinal enterococci and C.perfringens). The results showed that the investigated sand filters generally had low P-removal capacity and sometimes exceeded the criteria for excellent water quality set by the EU bathing water directive with regard to intestinal enterococci and E. coli. Only one sand filter of eight was confirmed to remove P according to the Swedish guidelines for areas with non-sensitive receiving waters with a tot-P effluent concentration below 3 mg L−1. This indicates that a downstream treatment step is needed to meet the guidelines regarding P discharge concentrations. Alkaline P-filters generally removed P efficiently. Despite high effluent pH, the collected data did not generally confirm a further reduction of the bacterial content of the wastewater in the P-filters, as had been previously hypothesized. However, effluent concentrations of indicator bacteria showed moderate positive correlations with effluent concentrations of P and organic matter, indicating the potential of the P-filters to serve as a polishing step also for bacteria.

  • 5.
    Vidal, Brenda
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Hedström, Annelie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Barraud, Sylvie
    Department of Civil Engineering and Urban Planning, National Institute of Applied Sciences of Lyon.
    Kärrman, Erik
    Division of the Built Environment, Research Institutes of Sweden.
    Herrmann, Inga
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Assessing the sustainability of on-site sanitation systems using multi-criteria analysis2019In: Environmental Science: Water Research & Technology, ISSN 2053-1400, Vol. 5, p. 1599-1615Article in journal (Refereed)
    Abstract [en]

    Small on-site sanitation systems are widely present in suburban and rural areas in many countries. As these systems often underperform and have an impact on receiving waters, understanding their overall sustainability is of interest for policy and decision-makers. However, the definition and estimation of indicators defining sustainability are challenging, as it is finding the methodological approach to combine qualitative and quantitative indicators into one comprehensive assessment. In this study, twelve indicators defined by environmental, economic, social, technical and health-related criteria were used to compare nine alternatives of on-site sanitation for single households. A non-compensatory method for multi-criteria decision analysis, ELECTRE III, was used for the assessment together with weights assigned to each indicator by a reference group. Several scenarios were developed to reflect different goals and a sensitivity analysis was conducted. Overall, the graywater–blackwater separation system resulted as the most sustainable option and, in terms of polishing steps for phosphorus removal, chemical treatment was preferred over the phosphorus filter, both options being implemented together with sand filters. Assessing the robustness of the systems was a crucial step in the analysis given the high importance assigned to the aforementioned indicator by the stakeholders, thus the assessment method must be justified. The proposed multi-criteria approach contributes to aid the assessment of complex information needed in the selection of sustainable sanitation systems and in the provision of informed preferences.

  • 6.
    Vidal, Brenda
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Hedström, Annelie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Herrmann, Inga
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Phosphorus reduction in filters for on-site wastewater treatment2018In: Journal of Water Process Engineering, ISSN 2214-7144, Vol. 22, p. 210-217Article in journal (Refereed)
    Abstract [en]

    Discharges of phosphorus (P) from on-site wastewater treatment systems generally contribute to eutrophication problems in Swedish freshwaters and, ultimately, in the Baltic Sea. Such concerns have led to a growing interest in improving P removal in treatment facilities. This study investigated the reduction of P in 12 full-scale on-site treatment systems featuring sand filters and alkaline P-filters by sampling and analysing filter influents and effluents. The flow-proportional samples collected were analysed for total and dissolved P, BOD7, total and dissolved organic carbon (TOC and DOC), and pH. Seven of the eight investigated sand filters did not provide satisfactory total P reduction; the likely explanations are filter clogging and wastewater dilution by extraneous water. In addition, effluents from four of the eight sand filters had total P concentrations higher than 3 mg L−1, which is the Swedish effluent limit recommended for common receiving waters, indicating that a subsequent polishing step would be needed. Six of the nine investigated P-filters reduced P adequately, with total P concentrations in the effluent ranging between 0.1 and 1.9 mg L−1. The three underperforming P-filters had effluent pH values below 9; filter age, clogging, and hydraulic overload were identified as probable reasons for their poor performance. A statistically significant correlation was found between total-P reduction and filtrate pH, but no significant correlation was detected between organic load in the influent and P reduction by the P-filters. The P-filter media replacement frequency could not be established, but filtrate pH appeared to be a good estimator.

  • 7.
    Vidal, Brenda
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Herrmann, Inga
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Hedström, Annelie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Små avloppssystem: hur hållbara är de?2019Other (Other (popular science, discussion, etc.))
    Abstract [sv]

    Små avloppssystem släpper ut avloppsvattnet lokalt, och därför är det viktigt att systemen uppfyller de krav som finns för utsläpp av organiskt material och näringsämnen och även klarar krav på smittskydd. Ofta fungerar, tyvärr, de små systemen inte som de borde, och när anläggningar ska uppgraderas eller när det ska byggas nya system bör det ske med tanke på hållbarheten. I ett nyligen avslutat projekt har vi arbetat med små avloppssystem i relation till hållbarhetskriterier och olika scenarier. Studien visar att det är viktigt att sätta upp mål och prioriteringar när man ska välja avloppslösning. Vilket som är det mest hållbara alternativet beror på vilka aspekter som prioriteras.

  • 8.
    Vidal, Brenda
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Herrmann, Inga
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Sharp, Liz
    Department of Civil and Structural Engineering University of Sheffield.
    Hedström, Annelie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    What are the drivers to decentralize wastewater treatment systems?: A Swedish perspective2018Conference paper (Refereed)
  • 9.
    Vidal, Brenda
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Kärrman, E.
    RISE Research Institute of Sweden, Urban Water management.
    Hedström, Annelie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Herrmann, Inga
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    An environmental approach to compare on-site sanitation systems2017Conference paper (Refereed)
1 - 9 of 9
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