Stein W. Østerhus

Rapid bacteriophage MS2 transport in an oxic sandy aquifer in cold climate: Field experiments and modeling

Virus removal during rapid transport in an unconfined, low-temperature (6°C) sand and gravel aquifer was investigated at a riverbank field site, 25 km south of Trondheim in central Norway. The data from bacteriophage MS2 inactivation and transport experiments were applied in a two-site kinetic transport model using HYDRUS-1D, to evaluate the mechanisms of virus removal and whether these mechanisms were sufficient to protect the groundwater supplies. The results demonstrated that inactivation was negligible to the overall removal and that irreversible MS2 attachment to aquifer grains, coated with iron precipitates, played a dominant role in the removal of MS2; 4.1 log units of MS2 were removed by attachment during 38 m travel distance and less than 2 days residence time. Although the total removal was high, pathways capable of allowing virus migration at rapid velocities were present in the aquifer. The risk of rapid transport of viable viruses should be recognized, particularly for water supplies without permanent disinfection.

Degradation of pCBA by catalytic ozonation in natural water.

The catalytic effect of commercially available ceramic Raschig rings versus stainless steel rings (known to be oxidant resistant) at different water qualities, for the decomposition of ozone and the hydroxyl radical formation have been investigated by using an ozone bubble column. Para-chlorobenzoic acid (pCBA) has been used as a model pollutant since it has been reported to be an ideal compound for ozone AOP studies because it displays slow reaction rates with ozone, but rapid oxidation kinetics with the OH radical. While the ozone was quite stable when the stainless steel rings were used as a packing media, the ceramic media enhanced the decomposition of the ozone. Nevertheless, the water quality was found to significantly affect the ozone stability. Indeed, in addition to high pH, both NOM and TIC lowered the ozone concentration in the system. When considering the degradation of pCBA, the ceramic packing rings, as high pH and NOM, increases its rate constant which is correlated to the higher decomposition of ozone and consequently to higher formation of hydroxyl radicals. In contrast, TIC decreased the degradation rate of pCBA even if it decomposes the ozone which is due to its scavenging effect.

Evaluation of bank filtration as a pretreatment method for the provision of hygienically safe drinking water in Norway: results from monitoring at two full-scale sites

Two case studies were carried out in central Norway in order to assess the performance of bank filtration systems in cold-climate fluvial aquifers relying on recharge from humic-rich surface waters with moderate microbial contamination. Three municipal wells and two surface-water sources at operative bank filtration systems were monitored for naturally occurring bacteriophages, fecal indicators, natural organic matter (NOM) and physico-chemical water quality parameters during a 4-month period. Aquifer passage effectively reduced the microorganism and NOM concentrations at both study sites. Bacteriophages were detected in 13 of 16 (81%) surface-water samples and in 4 of 24 (17%) well-water samples, and underwent 3 ± 0.3 log10 reduction after 50–80-m filtration and 20–30 days of subsurface passage. NOM reductions (color: 74–97%; dissolved organic carbon: 54–80%; very hydrophobic acids: 70%) were similar to those achieved by conventional water-treatment processes and no further treatment was needed. Both groundwater dilution and sediment filtration contributed to the hygienic water quality improvements, but sediment filtration appeared to be the most important process with regard to microbial and NOM reductions. A strengths-weaknesses-opportunities-threats analysis showed that bank filtration technology has a high potential as a pretreatment method for the provision of hygienically safe drinking water in Norway.RésuméDeux études de cas ont été menées dans le centre de la Norvège afin d’évaluer la performance des systèmes de filtration par les berges dans des aquifères alluviaux sous climat froid en se fondant sur une recharge à partir d’eaux de surface riches en humus avec une contamination microbienne modérée. Trois puits municipaux et deux sources d’eaux superficielles appartenant aux dispositifs opérationnels de filtration par les berges ont été suivis pour ce qui est des bactériophages qui surviennent naturellement, des indicateurs fécaux, de la matière organique naturelle (MON) et des paramètres de qualité physico-chimique de l’eau, pendant une période de 4 mois. Le transit dans l’aquifère a réduit efficacement la concentration des microorganismes et de MON dans les deux sites. Les bactériophages ont été détectés dans 13 des 16 (81%) échantillons d’eau de surface et dans 4 des 24 (17%) échantillons d’eau des puits, et ont subi une réduction de 3 ± 0.3 log10 après 50–80 m de filtration et 20–40 jours de transit dans le sous-sol. Les réductions de MON (couleur: 74–97%: carbone organique dissous: 54–80%: acides très hydrophobes: 70%) étaient similaires à celles obtenues par les procédés de traitement conventionnels de l’eau et aucun traitement supplémentaire n’a été nécessaire. Tant la dilution par les eaux souterraines que la filtration par les sédiments ont contribué à l’amélioration de la qualité hygiénique de l’eau, mais la filtration par les sédiments apparaît comme étant le processus le plus important concernant les réductions microbiennes et de MON. Une analyse des forces-faiblesses-opportunités-menaces a montré que la technologie de la filtration par les berges offre un fort potentiel en tant que méthode de prétraitement pour l’approvisionnement d’eau potable hygiéniquement sure en Norvège.ResumenSe realizaron dos estudios de casos en el centro de Noruega con el fin de evaluar el rendimiento de los sistemas de filtración de banco en los acuíferos fluviales en clima frío que dependen de la recarga del agua superficial rica en humus con contaminación microbiana moderada. Se monitorearon durante un período de 4 meses tres pozos municipales y dos fuentes de agua superficial en la operación de los sistemas de filtración de banco para la presencia natural de bacteriófagos, indicadores fecales, materia orgánica natural (NOM) y parámetros físico-químicos de la calidad del agua. El pasaje por el acuífero redujo eficazmente las concentraciones de microorganismos y el NOM en ambos sitios de estudio. Se detectaron bacteriófagos en 13 de 16 (81%) de las muestras de agua de superficie y en 4 de 24 (17%) de las muestras de agua de pozo y se sometieron a una reducción de 3 ± 0.3 log10 después de 50–80 m de filtración y 20–30 días de pasaje subsuperficial . Las reducciones de NOM (color: 74–97%, carbono orgánico disuelto: 54–80%, ácidos muy hidrófobos: 70%) fueron similares a las obtenidas por los procesos convencionales de tratamiento de agua y no se necesitó tratamiento adicional. Tanto la dilución de agua subterránea como la filtración por sedimentos contribuyeron a mejorar la calidad del agua, pero la filtración por sedimentos parecía ser el proceso más importante con respecto a las reducciones microbianas y de ONM. Un análisis de fortalezas-debilidades-oportunidades-amenazas mostró que la tecnología de filtración de banco tiene un alto potencial como método de pretratamiento para el suministro de agua potable higiénicamente segura en Noruega.摘要在挪威中部进行了两个案例研究,目的就是评价依赖于具有中度微生物污染、富含腐殖物地表水补给的寒冷气候河流含水层中河岸入渗的性能。对运行的河岸入渗系统三个市政井和两个地表水源进行了为期4个月的天然出现的噬菌体、排泄物指标、天然有机物和物理化学水质参数监测。含水层通道有效地减少了两个研究场地的微生物和天然有机物含量。在16个水样中的13个地表水样中(81%)和24个井水样中的4个水样中(17%)检出了噬菌体,经过50–80米的入渗及20–30天的地表以下通道,噬菌体减少了3 ± 0.3 log10。天然有机物的减少量(颜色:74–97%;溶解有机碳:54–80%;非常疏水酸:70%)与通过常规水处理过程获得的减少量类似,不需要进一步的处理。地下水稀释和沉积物入渗对水质改良贡献巨大,但沉积物入渗对于微生物和天然有机物的减少是最重要的过程。优势--劣势—机会—威胁分析显示,河岸入渗技术作为挪威挪威安全饮用水规定的预处理方法具有很大的潜力。ResumoDois casos de estudos foram conduzidos na Noruega central para avaliar o desempenho de sistemas de filtragem por bancadas em aquíferos aluviais de clima frio dependentes da recarga a partir de águas superficiais ricas em material húmico com contaminação microbiológica moderada. Três poços municipais e duas fontes de águas superficiais em sistemas de filtragem por bancadas em operação foram monitorados para bacteriófagos de ocorrência natural, indicadores fecais, matéria orgânica natural (MON) e parâmetros físico-químicos de qualidade da água durante um período de 4 meses. A passagem pelo aquífero reduziu efetivamente as concentrações de microrganismos e MON nos dois locais de estudo. Bacteriófagos foram detectados em 13 das 16 (81%) das amostras de águas superficiais e em 4 de 24 (17%) das amostras de águas dos poços, e passaram por uma redução de 3 ± 0.3 log10 após filtragem por50–80 m e 20–30 dias de passagem subterrânea. A redução de MON (cor: 74–97%; carbono orgânico dissolvido: 54–80%; ácidos muito hidrofóbicos: 70%) foi similar àquelas alcançadas por processos de tratamento convencionais da água e não foram necessários tratamentos subsequentes. Ambas, diluição das águas subterrâneas e filtração de sedimentos contribuíram para melhorias na qualidade higiênica das águas, mas a filtração de sedimentos parece ser o processo mais importante em relação a redução microbiana e de MON. Uma análise força-oportunidade-fraqueza-ameaça mostrou que a tecnologia de filtração por bancadas tem um alto potencial como um método pré-tratamento no fornecimento de água potável higienicamente segura na Noruega.

Coagulation and Corrosion Control for Soft and Coloured Drinking Water

Soft, acidic, and coloured (humic substances) surface waters with a low turbidity are commonly used for the drinking water supply in Norway. For these waters, coagulation/direct filtration combined with a process for corrosion control is one of the most interesting water treatment alternatives.

NOM removal by a Vacuum-UV/UV/TiO2 reactor assisted by electron scavengers

AbstractThis paper investigates the photochemical degradation of natural organic matter (NOM) which impacts the production of drinking water. Two types of reactors (with or without immobilised TiO2) and two types of 15 W low pressure mercury lamps (one emitting only at 254 nm and the other emitting at both 254 and 185 nm) were used. After 150 min of treatment of NOM-containing waters, the achieved average removals were 77% for the UV-absorbance at 254 nm (UV254), 83% for the colour and 70% for the dissolved organic carbon. Regardless of the initial concentration, the colour increased until it reached a maximum value before decreasing. It is believed that during degradation, aromatic components of the NOM structure are transformed into intermediates which have much higher absorbance at 410 nm than their parent compounds. The investigation of the effect of various electron scavengers (oxygen (O2), hydrogen peroxide (H2O2) and peroxodisulphate ()) has shown that could increase the degradation rate by a facto...