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Pilot-Scale Iron Electrocoagulation for Natural Organic Matter Removal / Avskiljning av naturligt organiskt material med järnelektrokoagulering i pilotskala
A scaled-up, continuous iron electrocoagulation reactor was built for drinking water treatment research. The impact of current density (i), metal loading (ML) and inter-electrode gap (d) on the removal of natural organic matter (NOM) was studied at 1.35 L/min. Removal performance was evaluated using UV-abs-254 and DOC analysis. Larger d provided the greatest reductions in DOC. When considering UV-abs-254 analysis, the largest and smallest d, 10 and 1 mm respectively, provided the greatest reductions. The effects of i on DOC and UVabs- 254 yielded the least clear results; however, it could be surmised that lower i provided greatest reductions of both DOC and UV-abs-254. The parameters providing the most substantial reduction on both DOC and UV-abs-254 reductions was ML. At the highest ML, both reductions in DOC and UV-abs-254 were observed, however continued work must be dedicated to further reducing the latter. Although DOC reductions were observed at ML < 51.1 mg/L, increased absorbance was observed through all factors and treatments. These increased absorbance results are due to dissolved iron species introduced during the EC process and present during UV-spectrophotometric analysis.
Dricksvatten – vattnets beredning inför desinfektion med UV Koagulationsfiltrering i snabbfilter / Drinking water – preparation for disinfection with UV-light Coagulation filtration in rapid sand filters
In the early 70ies, water in lakes and streams in Sweden was generally clean enough for minimal water treatment to be considered sufficient. The situation was altered by the introduction of novel organisms, e.g., Cryptosporidium and Giardia, into Swedish waters. Since the year 2000, these unicellular parasites are inherent to several surface waters in Sweden. Existing waterworks, however, are not built to handle such infectious agents, and recent years have seen outbreaks in Lidingö, Östersund and Skellefteå affect thousands. In addition, there is a constant risk of both new and recurrent infections, ranging from bed bugs in apartment complexes to tuberculosis or measles. As wastewater is a major source of infectious agents, prolonged treatment of sewage is essential. Parasites such as Cryptosporidium are chlorine-resistant; however, UV radiation has proved highly efficient as a means of water disinfection. Previous studies show that prior to radiation treatment, water turbidity and colour must be low. With this method, more than 90 % of all microorganisms are removed, and the overall water quality improved. Ideally, waterworks should be equipped with a two-step purification barrier, which efficiently decreases microbial contamination compared to single-filtration methodology, even though it can never be 100 % impermeable. Pre-treatment prior to UV radiation should utilise modern membrane filtration technology, where adjustable filter and pressure settings allow for control of a broad spectrum of water pollutants at a select level of efficiency. Alternatively, the established method of contact-coagulation-filtration offers water purification in a single step, discarding humic matter that affects the colour, taste and smell of untreated water. More than 98 % of colloidal particles, even up to quantities of more than 1000 g/m3, can thus be removed.
Structure and Properties of Peat Humic Substances / Struktur och egenskaper för humus från torv
Humic substances are formed in very different environment and the relations between properties (and structure) and precursor biota composition still is far from being clarified. The aim of this study was to analyse relations between properties of the peat, peat humic acids and humification degree on example of analysis of three bog profiles in ombrotrophic bogs to identify the links between peat age, decomposition and humification degree, botanical composition and properties of peat humic acids (elemental, functional composition). The found variability of peat properties is much less than the significant differences in properties of peat forming living matter thus stressing the dominant impact of humification process on peat properties.
Characterisation of natural organic matter (NOM) in water treatment using seed extracts / Karakterisering av naturligt organiskt material i vattenrening med hjälp av fröextrakt
Stormwater is known to be a potentially large contributor of toxic substances to receiving waters. To be able to This study evaluates the potential of using natural plant extract in water treatment and its corresponding effects on the final treated water. Fluorescence excitation-emission matrices (EEMs) were used to characterise NOM in water treated using Okra crude extract (CE) as a coagulant in a jar test experiment. The effect of thermal treatment (TT) was also examined. Four fluorescent peaks, tryptophan-like (T), tyrosine-like (B) and humic and fulvic acid-like (A and C) were found to be more dominant in CE samples than TT samples. The results further revealed that minimal dissolved organic carbon (DOC) addition and high turbidity removal efficiency were recorded in TT compared with CE samples. It is noteworthy that the pH of the treated water remained largely unaffected from initial 7.22 to 7.17 and 7.19 in TT and CE respectively due to their buffering capacity. Overall, the water treatment potential of Okra extract has demonstrated considerable efficiency in removing turbidity in water. Elevated NOM concentration was observed following use of crude extract. However, this increase in crude extract treated water NOM can be controlled by simple heat treatment.
Interdisciplinary Water Research Network Building within Nordic and Baltic Countries / Tvärvetenskaplig nätverksbyggande inom nordisk och baltisk vattenforskning
Viable Water Management and Governance for Futures (VIWAFU), a professional network for international and interdisciplinary collaboration amongst researchers from the Nordic and Baltic countries, was built for providing and sharing knowledge on water management and governance for future policy and decision making during the years 2012–2014. VIWAFU organized four workshops for MSc students, PhD students, and postdocs, focusing on different topics, e.g. water services management, water supply infrastructure, innovative water strategies, and water management in tourist areas. In top of the seminar themes, the students discussed and practiced communication – orally in small and big groups, and as written communication aimed at appealing to diverse readers. The communication was challenging because of cultural differences, but also because of the diverse disciplinary backgrounds of the participants. Altogether, the VIWAFU seminars were successful in creating a strong network between coming researchers from Nordic and Baltic countries. Hopefully this will lead to a tighter cooperation within water-related research around the Baltic Sea in the future.
Quicker response to quality changes in incoming water with decision support for coagulant dosage at Görväln drinking water plant / Beslutsstödssystem för koagulantdosering på Görvälnverket ger snabbare respons på kvalitetsförändringar i råvattnet
A decision support system (DSS) for control of the coagulant dosage at the Görväln drinking water plant has been developed and implemented. The goal with the DSS was to enable the transition from manual to automatic control of coagulant dosage. The DSS is based on a multivariate statistical regression (PLS) model mimicking the operators’ manual dosage of coagulant and is based solely on UV-absorbance, colour, COD, TOC and conductivity in the raw water. By external validation with two years of historical data, the model was proven to provide a good estimation of the manual dosage. When the model was implemented for dosage control, the variation of the quality of the treated drinking water was significantly reduced as a result of quicker and correct response to changes in the raw water and at the same time the coagulant consumption was maintained. The results pave the way for future optimization of the coagulant dose, resulting in reduced coagulant consumption while still maintaining or even increasing the drinking water quality. The approach presented is expected to be able to give positive results on other drinking water plants as well.
Skyfall och avrinning från gröna tak med sedumvegetation / Heavy rainfall and runoff from green roofs vegetated with sedum
Precipitation and runoff are increasing due to changes in climate and urbanization. As a result, more stormwater is produced and needs to be handled locally. Internationally, roofs with vegetation are regarded as a suitable measure for sustainable urban drainage system (SUDS), but have not been much studied in Norway. For five years, two extensive green roofs with substrate depth 3 cm have been compared with a roof without vegetation in a rather harsh environment in Oslo. Annual retention for the green roof was 25 %. The retention of intensive rainfalls could be 50 % and even higher for extreme events. Green roofs without drainage systems performed best. A 1 cm cloth under the substrate increased the performance and made the vegetation flourish. Green roofs utilize areas that are in little use, and are a good supplement to SUDS on costly ground areas.