Liv Fiksdal

Application of rapid enzyme assay techniques for monitoring of microbial water quality.

Rapid enzyme assay techniques based on direct measurement of beta-d-galactosidase (GALase) or beta-d-glucuronidase (GLUase) activity without selective cultivation are used for rapid estimation of the level of coliform bacteria and Escherichia coli in water samples. Reported detection limits using fluorogenic substrates correspond to culturable target bacteria concentrations that can be appropriate within present guidelines for recreational waters. The rapidity, that is detection within one hour, compromises the specificity of the assay; enzyme activity contributions from other than target bacteria need to be considered, particularly at low levels of target bacteria. Enzyme activities are more persistent than the culturability of target bacteria to environmental and disinfection stress, thus water samples may express enzyme activities of both culturable and viable non-culturable cells.

Rapid detection of Escherichia coli in water by a culture-based amperometric method

An amperometric culture-based method was developed for rapid detection of viable Escherichia coli in water. The bacteria were recovered by filtration and incubated in a selective medium, lauryl sulphate broth (LSB) supplemented with the substrate 4-aminophenyl-β-D-galactopyranoside (4-APGal) at 44.5°C. The electrochemically active molecule 4-aminophenol (4-AP) was produced after hydrolysis of 4-APGal by the enzyme β-galactosidase. 4-AP was measured by amperometry and was detected at a due concentration of E. coli. The time necessary for reaching that concentration was inversely related to the initial E. coli concentration of the sample. Environmental samples and suspensions of E coli IT were assayed. 4-AP was detected after 7.3 and 2.0 h in samples containing initial concentrations of E. coli IT1 of 4.5 and 4.5 × 10 6 cfu ml -1 respectively. For environmental samples with initial E. coli concentrations of 1.0 and 2.0 × 10 3 cfu ml -1 , 4-AP were detected after 10 and 6.6 h, respectively.

Waterborne disease in Norway: emphasizing outbreaks in groundwater systems

In this study, we compiled and examined available data on waterborne disease outbreaks (1984-2007) in Norway, with emphasis on groundwater systems. A total of 102 waterborne outbreaks and 17,243 disease cases were reported during the period 1984-2007. The proportion of outbreaks related to groundwater reflected the proportion of groundwater works in Norway (40%). The proportion of disease cases corresponded to the proportion of persons supplied by groundwater (15%). Norovirus was identified as the most important disease causing agent in groundwater systems. No clear seasonal correlation was observed for Norovirus outbreaks in groundwater, but the largest outbreaks occurred during winter season. All outbreaks of campylobacteriosis occurred during March to November, with a peak in July-September, which correlates with the occurrence of coliforms in Norwegian groundwater in bedrock wells.

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.