The outbreak of the SARS-CoV-2 pandemic led to increased use of disinfectants and antiseptics (DA... more The outbreak of the SARS-CoV-2 pandemic led to increased use of disinfectants and antiseptics (DAs), resulting in higher concentrations of these compounds in wastewaters, wastewater treatment plant (WWTP) effluents and receiving water bodies. Their constant presence in water bodies may lead to development and acquisition of resistance against the DAs. In addition, they may also promote antibiotic resistance (AR) due to cross- and co-selection of AR among bacteria that are exposed to the DAs, which is a highly important issue with regards to human and environmental health. This review addresses this issue and provides an overview of DAs structure together with their modes of action against microorganisms. Relevant examples of the most effective treatment techniques to increase the DAs removal efficiency from wastewater are discussed. Moreover, insight on the resistance mechanisms to DAs and the mechanism of DAs enhancement of cross- and co-selection of ARs are presented. Furthermore,...
This paper reviews current knowledge on sources, spread and removal mechanisms of antibiotic resi... more This paper reviews current knowledge on sources, spread and removal mechanisms of antibiotic resistance genes (ARGs) in microbial communities of wastewaters, treatment plants and downstream recipients. Antibiotic is the most important tool to cure bacterial infections in humans and animals. The over- and misuse of antibiotics have played a major role in the development, spread, and prevalence of antibiotic resistance (AR) in the microbiomes of humans and animals, and microbial ecosystems worldwide. AR can be transferred and spread amongst bacteria via intra- and interspecies horizontal gene transfer (HGT). Wastewater treatment plants (WWTPs) receive wastewater containing an enormous variety of pollutants, including antibiotics, and chemicals from different sources. They contain large and diverse communities of microorganisms and provide a favorable environment for the spread and reproduction of AR. Existing WWTPs are not designed to remove micropollutants, antibiotic resistant bacte...
Analysis and Applications of Microorganisms from a Chalk Oil Reservoir in the North Sea
Ekofisk er et krittsteinsreservoar i den norske sektoren av Nordsjoen, og dette reservoaret inneh... more Ekofisk er et krittsteinsreservoar i den norske sektoren av Nordsjoen, og dette reservoaret inneholdt aktive og diverse mikrobielle samfunn. Mikrobielle aktiviteter kan medfore skadelige effekter som surgjoring av reservoarer, men ogsa ha nytteeffekter som ved okt oljeutvinning. Formalet med dette studiet var a karakterisere mikrobielle samfunn i Ekofisk reservoaret, samt a framskaffe innsikt i mikrobielle mekanismer som var viktige for a) a kontrollere reservoarforsuring og b) kunne medvirke til okt oljeutvinning. Prover av produsertvann fra oljereservoaret Ekofisk ble karakterisert ved bade kulturavhengige og –uavhengige teknikker. De mikrobielle samfunnene i Ekofiskreservoaret var dominert av termofile mikroorganismer, mange av disse hadde sulfidogen eller metanogen fysiologi. Mikroorganismene viste fylogenetiske likheter med organismer som har blitt identifisert i andre varme oljereservoarer. De dominerende mikroorganismene identifisert direkte fra prover av produsertvann viste sekvenslikheter med medlemmer av slektene Thermotoga, Caminicella, Thermoanaerobacter, Archaeoglobus, Thermococcus og Methanobulbus. Anrikingskulturer fra produsertvann var dominert av kapslete staver. Sekvensanalyser av kulturene indikerte dominans av slektene Petrotoga, Arcobacter, Archaeoglobus og Thermococcus. Reservoarforsuring, forarsaket av sulfidproduksjon fra sulfatreduserende prokaryoter (SRP) kan reduseres ved injeksjon av nitrat eller nitritt. Nitrat eller nitritt reduserer sulfidproduksjon, enten ved stimulering av nitratreduserende bakterier (NRB) ved nitrattilsetning, eller via metabolsk inhibisjon av sulfittreduksjon til sulfid vha. nitritt. Vare studier viste at tilsetning av nitrat ikke kunne kontrollere surgjoring effektivt, mens nitritt effektivt inhiberte sulfatreduksjon selv ved svaert lave konsentrasjoner (0.25 – 1 mM) i studier med bade statiske kulturer og i bioreaktorer. For a studere prosesser ved mikrobiell okt oljeutvinning (MEOR) ble to fermentative anrikingskulturer fra hhv. Ekofisk og Draugen-reservoaret benyttet i en serie av modellforsok. I lopet av denne studien ble det pavist at L- fruktose, Dgalakturonsyre, turnose, pyrodruesyre og metylester av pyrodruesyre var substrater som ble fermentert av anrikingskulturen fra Ekofisk. Det ble ogsa pavist at de mikrobielle cellene fra Draugen-kulturen i seg selv kunne emulgerte olje. I tillegg forarsaket begge kulturene endrete fuktegenskaper. Dette ble vist i to eksperimenter; 1) ved endringer av hoyden pa olje-vann menisken i et kapillaerrorsystem, og 2) ved forandringer i kontaktvinkler pga. biofilmvekst pa polykarbonat-kuponger. I det siste eksperimentet ble kontaktvinkel endret fra 154° pa kontroller til 0o pga. biofilmvekst pa kupongen. Slike endringer i fuktegenskaper kan resultere i okt oljeutvinning. I dette prosjektet ble det vist at nitritt-behandling var en effektiv metode for a kontrollere surgjoring. I tillegg viste studiene at biofilm kan spille en viktig rolle ved reservoarforsuring, som malt ved endringer i fuktegenskaper. Bedre forstaelse av mikrobielle samfunn i oljereservoarer vil derfor gi muligheter til a kontrollere bade skadelige og positive effekter.
It is well known from several core scale experiments that microbial activity inside a core may le... more It is well known from several core scale experiments that microbial activity inside a core may lead to enhanced oil production. In this work we argue that the only realistic microbial mechanism that contributes to oil production is that of the biof ilm type, simply because of the low concentration of microbes inside the porous media . Microbial activity can lead to formation of a biofilm on the rock surface and the oil wat er interface. By modelling the microbes as immiscible drops we show that they can change the wetting properties of the rock. The model used is a Lattice Boltzmann algorithm for sol ving the multiphase Navier- Stokes equations. Experiments with two strains of micro bes from oil fields have been performed. The experiments are focused on studying the abili ty of microbes to attach to interfaces and surfaces and thereby change the wetting prope rties of oil, brine and rock. The first type is a microbial capillary tube experiment where microbes grown inside capillary t...
Microbial enhanced oil recovery (MEOR) represents a possible cost-effective tertiary oil recovery... more Microbial enhanced oil recovery (MEOR) represents a possible cost-effective tertiary oil recovery method. Although the idea of MEOR has been around for more than 75 years, even now little is known of the mechanisms involved. In this study, Draugen and Ekofisk enrichment cultures, along with Pseudomonas spp. were utilized to study the selected MEOR mechanisms. Substrates which could potentially stimulate the microorganisms were examined, and l-fructose, d-galacturonic acid, turnose, pyruvic acid and pyruvic acid methyl ester were found to be the best utilized by the Ekofisk fermentative enrichment culture. Modelling results indicated that a mechanism likely to be important for enhanced oil recovery is biofilm formation, as it required a lower in situ cell concentration compared with some of the other MEOR mechanisms. The bacterial cells themselves were found to play an important role in the formation of emulsions. Bulk coreflood and flow cell experiments were performed to examine MEOR mechanisms, and microbial growth was found to lead to possible alterations in wettability. This was observed as a change in wettability from oil wet (contact angle 154 •) to water wet (0 •) due to the formation of biofilms on the polycarbonate coupons.
Unfortunately, the name of the third author was rendered incorrectly. His correct name is given a... more Unfortunately, the name of the third author was rendered incorrectly. His correct name is given above.
Samples from an oil storage tank (resident temperature 40 to 60°C), which experienced unwanted pe... more Samples from an oil storage tank (resident temperature 40 to 60°C), which experienced unwanted periodic odorous gas emissions, contained up to 2,400/ml of thermophilic, lactate-utilizing, sulfate-reducing bacteria. Significant methane production was also evident. Enrichments on acetate gave sheathed filaments characteristic of the acetotrophic methanogen Methanosaeta thermophila of which the presence was confirmed by determining the PCR-amplified 16S rDNA sequence. 16S rDNA analysis of enrichments, grown on lactate-and sulfate-containing media, indicated the presence of bacteria related to Garciella nitratireducens, Clostridium sp. and Acinetobacter sp. These sulfidogenic enrichments typically produced sulfide to a maximum concentration of 5-7 mM in media containing excess lactate and 10 mM sulfate or thiosulfate. Both the production of sulfide and the consumption of acetate by the enrichment cultures were inhibited by low concentrations of nitrite (0.5-1.0 mM). Hence, addition of nitrite may be an effective way to prevent odorous gas emissions from the storage tank.
Recent studies have indicated that oil reservoirs harbour diverse microbial communities. Culture-... more Recent studies have indicated that oil reservoirs harbour diverse microbial communities. Culture-dependent and culture-independent methods were used to evaluate the microbial diversity in produced water samples of the Ekofisk oil field, a high temperature, and fractured chalk reservoir in the North Sea. DGGE analyses of 16S rRNA gene fragments were used to assess the microbial diversity of both archaeal and bacterial communities in produced water samples and enrichment cultures from 4 different wells (B-08, X-08, X-18 and X-25). Low diversity communities were found when 16S rDNA libraries of bacterial and archaeal assemblages were generated from total community DNA obtained from produced water samples and enrichment cultures. Sequence analysis of the clones indicated close matches to microbes associated with high-temperature oil reservoirs or other similar environments. Sequences were found to be similar to members of the genera Thermotoga, Caminicella, Thermoanaerobacter, Archaeoglobus, Thermococcus, and Methanobulbus. Enrichment cultures obtained from the produced water samples were dominated by sheathed rods. Sequence analyses of the cultures indicated predominance of the genera Petrotoga, Arcobacter, Archaeoglobus and Thermococcus. The communities of both produced water and enrichment cultures appeared to be dominated by thermophilic fermenters capable of reducing sulphur compounds. These results suggest that the biochemical processes in the Ekofisk chalk reservoir are similar to those observed in high-temperature sandstone reservoirs.
Use of Nitrate or Nitrite for the Management of the Sulfur Cycle in Oil and Gas Fields
All Days, 2007
The production of sulfide by sulfate-reducing bacteria (SRB) in oil and gas fields causes problem... more The production of sulfide by sulfate-reducing bacteria (SRB) in oil and gas fields causes problems including enhanced corrosion risk, reservoir plugging and deterioration of product quality. Injection of nitrate or nitrite stimulates heterotrophic nitrate-reducing bacteria (hNRB), which compete with SRB for oil organics, such as volatile fatty acids (VFA). Nitrate also stimulates nitrate-reducing, sulfide-oxidizing bacteria (NR-SOB), which lower sulfide levels. Nitrite is a strong and specific inhibitor of the SRB enzyme responsible for sulfide production, whereas nitrate does not inhibit SRB. Hence, injection of nitrate or nitrite can prevent or remediate problems in the oil and gas industry caused by SRB activity, provided hNRB and NR-SOB are present. A survey of 8 oil fields, 2 gas storage reservoirs and an oil storage tank indicated that SRB and hNRB were widely distributed, whereas the distribution of NR-SOB appeared more limited. The SRB and hNRB were able to use lactate, as w...
Microbial enhanced oil recovery (MEOR) represents a possible cost-effective tertiary oil recovery... more Microbial enhanced oil recovery (MEOR) represents a possible cost-effective tertiary oil recovery method. Although the idea of MEOR has been around for more than 75 years, even now little is known of the mechanisms involved. In this study, Draugen and Ekofisk enrichment cultures, along with Pseudomonas spp. were utilized to study the selected MEOR mechanisms. Substrates which could potentially stimulate the microorganisms were examined, and l-fructose, d-galacturonic acid, turnose, pyruvic acid and pyruvic acid methyl ester were found to be the best utilized by the Ekofisk fermentative enrichment culture. Modelling results indicated that a mechanism likely to be important for enhanced oil recovery is biofilm formation, as it required a lower in situ cell concentration compared with some of the other MEOR mechanisms. The bacterial cells themselves were found to play an important role in the formation of emulsions. Bulk coreflood and flow cell experiments were performed to examine MEOR mechanisms, and microbial growth was found to lead to possible alterations in wettability. This was observed as a change in wettability from oil wet (contact angle 154 • ) to water wet (0 • ) due to the formation of biofilms on the polycarbonate coupons.
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Papers by Krista Kaster