Population growth, increasing living standards, but also environmental hazards with global climate change as the most significant are all contributing to an increasing water stress in many parts of the world. While access to fresh water for drinking water is getting more costly due to environmental pollution, uses of drinking water conflicts with water needs for agricultural and industrial use, which are in need of substantial water quantities. The use of reclaimed wastewater for non-potable purposes provides a solution for this. This is not new and has in fact been applied in many regions as the main water management approach. As water scarcity becomes more severe, also the need for more sustainable and holistic approaches to deal with our limited fresh water resources becomes more and more obvious. The traditional one-way water handling approach, with end-of-pipe treatment releasing “clean” effluent water to nature, has to be converted into a society-internal water reuse scheme where different water qualities and water uses are considered as an integral part of the water cycle. The present report presents activities and results from an international project that aimed at developing and optimizing water treatment processes and systems for sustainable reuse of treated wastewater. The starting point is to combine the sequential batch treatment (SBR, sequencing batch reactors) with different conventional and emerging secondary and tertiary treatment techniques in various combinations, optimized from an overall sustainability perspective. Evaluation and optimization is achieved using life cycle assessment and life cycle cost assessment and their combination.
Större delen av de läkemedel och andra mikroföroreningar som används i samhället hamnar i våra avloppsreningsverk. Där bryts en del ner effektivt, men många föroreningar passerar i stort sett opåverkade genom verken. Vid låg utspädning i närrecipienten kan vissa substanser nå så höga halter att man inte kan utesluta effekter på vattenlevande organismer. Kompletterande rening av avloppsvattnet vid avloppsreningsverk kan därför vare ett alternativ för att avlägsna dessa mikroföroreningar. De mest lovande teknikerna för att minska utsläppen av ett brett spektrum av läkemedelssubstanser och andra svårnedbrytbara substanser är behandling med starka oxidationsmedel, främst ozon, adsorption till aktivt kol och en utökad biologisk nedbrytning. Denna rapport redovisar resultat från fortsatta försök med avskiljning av särskilt läkemedelsrester i avloppsvatten inom projektet SystemLäk, och kompletterar tidigare genomförda försök inom samma projekt. I första hand har 24 olika läkemedel, som ofta förekommer i avloppsvatten och som representerar olika läkemedelsgrupper, analyserats. Tekniker som studerats innefattar: § Granulerat aktivt kol som filtermaterial med biologisk aktivitet - BAF(GAK) § Rening med biokol framställt från bioslam/organiskt substrat - BAK § Användning av pulveriserat aktivt kol i MembranBioReaktor (MBR) -PAK § Oxidation med ozon § Oxidation med klordioxid Genomförda tester, i kombination med tidigare försök, visar tydligt på att de flesta studerade teknikerna ger ökad avskiljning av de flesta studerade ämnena. I många fall får man en mycket bra effekt med en rimlig insats. Testerna har även lyft fram begränsningar hos de studerade teknikerna: BAF(GAK) - Granulerat aktivt kol som biofilter, BAK – Biokol framställt från bioslam, PAK-MBR – Pulveriserat aktivt kol (PAK) i membranbioreaktor, Resurseffektiv ozonering, Klordioxid (ClO2) För mer detaljer kring de ämnen som studerats, analysmetoder för dessa, vilken effekt dessa har i recipienten samt till vilken nivå de bör reduceras hänvisas till den första delrapporten i SystemLäk (Baresel m fl., 2015a). För en samlad bedömning av olika reningssystem inklusive miljöpåverkan och kostnader samt vilka av tekniker som rekommenderas hänvisas till slutrapporten i SystemLäk (Baresel m fl., 2017).
Treatment with ozone or granulated activated carbon (GAC) are compared for further purification of an already well treated (chemically and biologically) wastewater. The wastewater was taken from the pilot plant Hammarby Sjöstadsverk where incoming water to the main WWTP Henriksdal was treated by pre-precipitation, pre- denitrification, nitrification, and post-denitrification in an MBR pilot scale, providing particle-free water. This represents the process planned for the expanded Henriksdal WWTP. The removal efficiency of the MBR-pilot is highly effective, but further removal of some organic compounds may eventually be required. This is particularly true for pharmaceutical residues. Polishing treatment with ozone or active carbon is most relevant for the moment and has been tested in a scale around 1 m3/hr. Concentrations of 37 pharmaceutical residues and a number of phenolic substances were analyzed before and after the treatments. Ozone was tested at doses between 3 and 13 g/m3. 9 of the 18 detectable pharmaceutical residues in the effluent from the MBR pilot were removed already at 3 g ozone/m3. After 5 g ozone/ m3 remained six compounds in measurable concentrations, and after 7 g ozone/m3 only 3 pieces (atenolol, metoprolol, and oxazepam). After 13 g ozone/m3 remained only oxazepam (18 ng/L). Among phenolic compounds triclosan and bisphenol A were removed effectively at 7 g of ozone/m3. Nonylphenol and octylphenol were much more stable and levels were just halved at 7 g ozone/m3. 13 g ozone /m3 did not produce an increased reduction. A potential method to adapt the ozone dose depending on the demand is discussed. Granulated activated carbon (GAC) was tested in a pilot with automatic backwash when the bed tended to clog. Most of the analyses were made after about 6800 bed volumes had passed, corresponding to about 13 m3/kg coal. The separation efficiency decreases with load, but has been shown in previous experiments to be acceptable up to at least 25 000 bed volumes, or 50 m3/kg coal. The contact time in the bed (EBCT) appeared not to affect the reduction in the range of 10 to 18 minutes. The removal of pharmaceutical residues was generally better with GAC than with 7 g ozone/m3, and the removal of oxazepam was evidently more effective with GAC than at 13 g ozone/m3. Octylphenol and triklosan were effectively reduced, but not nonyphenol and bisphenol A. Additional analyzes at higher loads are required in order to evaluate the removal efficiency over the entire lifetime of the carbon. Supplementary analyzes after about 16 700 Empty Bed Volumes (EBV), equivalent to more than 32 m3/kg carbon, however, indicate a continued good removal efficiency. The treatment with ozone and GAC was also compared with the treatment using reverse osmosis (RO) from a parallel project. RO was more effective than both ozone and GAC, but is overall significantly more resource intensive. The color of treated wastewater declined sharply using the two methods, but most effective was ozone. Other parameters were less affected, but an additional disinfection of the already fairly clean water was recorded with both methods. The target level of removal should be determined by each substance and its impact in the receiving water (PNEC) and the individual plant's initial dilution in the receiving water. The comparison of the different treatment methods should also consider costs (capital and operating costs) and total resource consumption and environmental impacts (life cycle analysis). These calculations are under preparation, based on current tests, but are not yet completed. This report is only available in Swedish.
Different studies have indicated limitations of treatment technologies such as ozone oxidation and active carbon for certain particularly persistent substances in municipal wastewater. Therefore, the use of advanced oxidation treatment using UV light coupled with hydrogen peroxide (UV/H2O2) for the oxidation of pharmaceutical residues in municipal wastewater effluents was investigated. The conducted tests, comprising both lab-scale and pilot-scale studies, show good removal efficiencies for all pharmaceuticals observed in the effluent of Stockholm’s largest WWTP. A clear dose-response behaviour is observed that can be used for targeting various substances depending on removal target definition. The cost evaluation of the technique reveals that UV/H2O2 applications may be more cost intensive compared to other technologies, especially ozonation and activated carbon. However, compared to combinations of several technologies such as ozonation and activated carbon or technologies with ultrafiltration, UV/H2O2 applications may be in the same or lower cost range. Based on the project results it is understood that the gap in costs towards other removal techniques is not that wide and that several advantages of the UV/H2O2 technology may favour its application in various cases. For this, further investigations are planned by the project partners.
Här rapporteras om ett långtidsförsök med aktivt kol i kolonner/bäddar för att bestämma avskiljning och kolets kapacitet. Kolfiltret sattes in som ett extra polersteg efter den normala reningen vid Henriksdals avloppsreningsverk i Stockholm. Försöken genomfördes under 19 månader 2011-2012 vid försöksanläggningen Hammarby Sjöstadsverk. Avskiljningen av analyserade läkemedelssubstanser var generellt mycket bra. Vid en belastning motsvarande 50 m3 vatten/kg kol (20 g kol/m3 vatten) passerade 5-10 % av vissa föreningar den första kolonnen. Även vid över 70 m3/kg kol i första kolonnen kunde man inte påvisa kvantifierbara mängder ut från kolonn 2. Det största problemet för teknisk drift var den begränsade hydrauliska kapaciteten, till stor del beroende på mikrobiell tillväxt i kolonnerna. Kolet måste regelbundet rensas genom backspolning med luft och vatten. Baserat på förbrukningen av kol och andras beräkningar av totalkostnaden inklusive investeringar kommer man fram till en totalkostnad för reningen med aktivt kol kring 1 kr/m3 vatten i ett sort avloppsreningsverk. Det är högre än för ozonbehandling, men lägre än för andra metoder med samma effektivitet. Vid en bedömning av olika metoder bör också andra faktorer än de rent ekonomiska vägas in. Fortsatta studier av hydraulisk kapacitet, nödvändig uppehållstid och avskiljning av andra organiska föreningar föreslås, och har delvis påbörjats.
Syftet med detta projekt var att studera rening av PFAS-förorenat lakvatten från avfallsanläggningar genom praktiska försök i labb- och pilotskala och genom sammanfattning och utvärdering av försök som genomfördes på andra avfallsanläggningar. Försök med ett brett spektrum av olika reningstekniker genomfördes på fyra avfallsanläggningar. En generell slutsats för alla tekniker som ger en rimlig reningskostnad är att de PFAS som har en kortare fullfluorerad kolkedja avskiljs sämre än de med en längre kedja. Ett stort fokus i utvärderingen av resultaten var därför att demonstrera hur olika reningsgrader för olika PFAS kan påverka reningskostnader. Utvärderingen av samtliga försök visade att skumfraktionering, rening med GAK och jonbytare är de mest lovande teknikerna som ger liknande kostnader vid samma reduktionsgrad. Om reningen ska utformas utifrån dagens krav blir reningskostnaderna lägst vid användning av jonbytare. Skumfraktionering ger bra reduktion av PFAS med sex eller fler helfluorerade kolatomer och är den mest kostnadseffektiva tekniken för reduktionen av de mest toxiska PFAS. Rening med GAK bedöms vara motiverat vid låga inkommande DOC-halter och om rening av andra organiska miljögifter behövs. Kostnad för rening av PFAS-förorenat lakvatten beräknas till 5-13 kr/m3 för en mellanstor avfallsanläggning.
Many process parameters in a wastewater treatment plant are expensive, difficult or even impossible to measure online, limiting the possibilities for efficient process monitoring and control. In this work, soft sensors were developed to provide on-line values for a number of parameters, primarily different fractions of phosphate (PO4 and total phosphorous), nitrogen (NO3, NH4 and total nitrogen), organic matter (COD) and suspended solids (TSS), at five different steps of the wastewater treatment process at the R&D-facility Hammarby Sjöstadsverk. The soft sensors were PLS (Partial Least Squares) models predicting the value of the hard-to-measure parameters based on easy-to-measure process parameters that were normally measured on-line or on acoustic data generated by acoustic sensors placed on the tanks of three of the five selected process steps. During a 13-day sampling campaign, data for the soft sensor development and validation were collected by laboratory analysis of the hard-to-measure parameters and combining them with corresponding 5 minute average values of the on-line parameters and the acoustic data. A majority of the soft sensors that were based on acoustic data had comparable or better performance than corresponding models using process data, indicating that data from acoustic sensors are of interest as input variables for soft sensors at WWTPs. The performance of the soft sensors varied significantly and some of them showed promising results. When removing the effect of the laboratory measurement error and the sampling error, 6 out of 26 soft sensor models had a so-called relative true prediction error less than 10% (NO3 in untreated water, COD, TSS and NO3 in the first bioreactor, NH4 in the last bioreactor and TSS in the membrane bioreactor). In combination with the proposed actions for further improvement of the models, the results suggest that soft sensors, that in many cases preferably could be based on acoustic data, is a possible approach to provide WWTPs with on-line process data.