The drinking water production in Sweden is facing challenges because of climatic changes, eutrophication and brownification, which contributes to an increase of algal blooms. This can lead to a production of different types of toxins, and the most common group of algal toxins is the hepatotoxic microcystins (MC). Other algal toxins that occur in Sweden are anatoxin-A (ATX-A) and the paralytic shellfish toxins (PST), which are neurotoxic. Flocculation and filtration has been shown to reduce intracellular MC, but to reduce extracellular MC it seems like other techniques are needed, such as membrane filtration, active carbon or ozone. It has also been shown that dissolved organic carbon (DOC) might affect the reduction of MC, either through occupying adsorption spots on the membrane, or through bindings between MC and DOC. In this project, the reduction of four types of added MC (microcystin-LR, microcystin-RR, microcystin-LY and (D-Asp3)microcystin-LR) with two nanofilters (NF) (with molecular weight cutoff (MWCO) 300-500 Da and 1000 Da) and one ultrafilter (UF) (MWCO 10000 Da) was studied. Further, the sorption between toxins and membrane or between toxins and DOC was studied. Water samples from three Swedish lakes were used to achieve a varying DOC-character. The reduction was also studied in synthetic water (MilliQ-water with adjusted pH and conductivity). This was done in order to study if the reduction was affected of the presence of DOC. The reduction of ATX-A and PST was studied in one experiment, with an NF-membrane (MWCO 1000 Da). The studied PST’s were saxitoxin (STX), N-sulfocarbamoyl-gonyautoxin-2 (C1) and Gonyuatoxin‑2 (GTX2). MC was reduced to under the limit of detection for all NF-experiments, while a low or no reduction was observed with UF. MC-RR was the toxin that, to the biggest extent, bound to the membrane or to DOC. MC seemed to bind to the membrane or to DOC to a higher extent when the DOC was hydrophilic and low molecular autochthonous, as compared to when the DOC was allochthonous. The reduction of ATX-A and PST was 20 – 40 %, with a reduction that declined during the experiment. C1, the PST with highest molecular weight and lowest net charge, was reduced to the lowest extent, while STX, the PST with the lowest molecular weight and the greatest net charge, was reduced to the highest extent. This implies that size exclusion was not a contributing reduction mechanism for ATX-A or PST, while electrostatic mechanisms probably were more important.

I Sverige har ungefär 1,2 miljoner människor enskild dricksvattenförsörjning och en stor andel av dessa har problem med vattenkvalitet. En utvärdering av reningstekniker har inletts av företaget Ecoloop och Utvecklingscentrum för vatten och detta examensarbete fördjupar och följer upp de inledande resultaten från det projektet. Med hjälp av en litteraturstudie, modellering i Visual MINTEQ och fem fallstudier utvärderades reningsteknikerna jonbytarfilter och nanofilter avsett för enskild dricksvattenförsörjning med avseende på reduktion av föroreningarna bly och uran. Fallstudierna visar att jonbytarfilter kan fungera väl för att reducera uranhalter men en viss inkörningsperiod förekommer där bieffekter, exempelvis kemisk smak, kan förekomma samt att underhåll är viktigt för att fortsätta ha en hög reduktionsgrad. Fallstudierna kunde ej besvara ifall nanofilter är en lämplig reningsteknik för ändamålet att reducera halter av bly och uran under de gränsvärden som finns, eftersom de membranfilter som använts i fallstudierna visade sig ha för stor porstorlek för att kallas nanofilter. En slutsats är att det är viktigt att fortsätta med provtagning av vattnet även efter att ett filter installerats. Utöver det genomfördes intervjuer och en enkätundersökning som undersökte hur kommuner i Sverige arbetar för att möta enskilda brunnsägare i deras utmaningar med vattenkvalitet. Intervjuerna och enkätsvaren visar på en variation där några kommuner jobbar aktivt för att stötta de enskilda brunnsägarna med rådgivning, bidrag och förebyggande åtgärder medan andra kommuner är mer passiva och låter de enskilda ta eget ansvar för sitt vatten. / About 1.2 million people in Sweden rely on their own private drinking water supply for their daily needs and a large portion of those have problems with water quality. An evaluation of water treatment technology intended for private wells has been initiated by the companies Ecoloop and Utvecklingscentrum för vatten and this master’s thesis further develops and follows up the initial results. By conducting a literature review, doing modelling in Visual MINTEQ and carrying out five case studies the two water treatment techniques nanofilter and ion exchange are evaluated in the context of domestic water supplies with water quality problems caused by either lead or uranium. The case studies shows that ion exchange filters can reduce uranium in drinking water below the threshold value but with some initial side effects (i.e., chemical taste of the water). The case studies could not show if nanofilters are suitable to reduce lead or uranium from domestic water supplies, since the pore size was found to be too big for the membrane filters used in the case studies to be called nanofilters. This concludes that it is important to proceed with sampling of the water even after installing a filter for water treatment. Additionally, interviews and a survey were conducted which investigated how municipalities in Sweden are working to meet private well owners in their challenges with water quality. The answers from the interviews and the survey displays a variation where some municipalities are actively supporting the private well owners through counselling, grants, and preventive measures while other municipalities are more passive and leaves the individual well owners responsible to look after their water quality by themselves.