Estimation of retardation of tce migration in a porous medium using batch tests

Sorption is one of the most important processes responsible for contaminants migration in groundwater. The main aim of this study was to determine the retardation of TCE migration due to sorption in the Quaternary aquifer consisting mainly of medium to fine sands. Two types of the aquifer material, characterised by different grain-size distributions and similar organic matter contents were used for the batch tests. Soil samples came from a representative profile of the Nowa Dęba area - the site contaminated with chlorinated ethenes. The batch experiments allowed for determining the sorption isotherms, the partition coefficients K, between liquid and solid phases and, finally, the retardation coefficients R of TCE migration in groundwater in the porous aquifer

Column experiments on sorption coefficients and biodegradation rates of selected pharmaceuticals in three aquifer sediments.

The presence of pharmaceuticals in the environment, and in groundwater, has been recognized as a great environmental concern. Biodegradation and sorption are the main processes leading to the removal of contamination from the water phase. The aim of this study was to determine the transport processes of selected pharmaceuticals (antipyrine, atenolol, carbamazepine, caffeine, diclofenac, ketoprofen, sulfamethoxazole) in selected sediments (coarse sand, medium sand, sandy loam) in laboratory experiments. Moreover, the impact of flow velocities on the sorption and degradation rates of the selected compounds was studied. Column experiments were performed at three flow velocities, under abiotic and biotic conditions, applying conservative (bromide) and reactive tracers (pharmaceuticals). From the breakthrough curves, retardation factors and degradation rates were determined and the influence of variable flow conditions on transport parameters was evaluated. Low observed concentrations and recoveries of atenolol indicated a strong influence of sorption on its transport. Diclofenac, caffeine, and carbamazepine were also affected by sorption but to a lesser extent. Sulfamethoxazole, ketoprofen, and antipyrine were recovered nearly completely, indicating an almost conservative transport behavior. Biodegradation was small for all the compounds, as the results from biotic and abiotic column experiments were similar. Transport of the tested pharmaceuticals was not influenced by different flow velocities, as similar modelled degradation rates and retardation factors were found for all tested flow velocities

Ocena możliwości samoistnej biodegradacji trii tetrachloroetenu w wodach podziemnych w rejonie ujęcia Nowa Dęba

Natural Attenuation (NA) in the case of groundwater contaminated with organic compounds relies mainly on intrinsic biodegradation processes. The aim of reliance on natural processes is to achieve site-specific cleanup objectives within reasonable time frames and costs. Such approach may be considered as a risk reduction/remedial option for groundwater contaminated with trichloroethene (TCE) and tetrachloroethene (PCE) in the vicinity of Nowa Deba waterworks. This case study presents implementation of the USEPA’s guideline „Technical protocol for evaluating natural attenuation of chlorinated solvents in ground water” to asses intrinsic biodegradation potentials in contaminated groundwater in the case of Nowa Deba. Literature and field data collected from wells and piezometers were used to develop a conceptual model of contaminants’ fate and transport from a source to a receptor. The intrinsic biodegradation was investigated basing on available analytical parameters (eg concentrations of oxygen, nitrates, chlorides, and pH, TOC and temperature) that are considered as indicators of TCE and PCE transformation. Preliminary screening was done by giving certain points for these parameters, and interpreted in order to asses intrinsic biodegradation potentials. The results indicate inadequate evidence for intrinsic biodegradation (reductive dehalogenation) of TCE and PCE, thus a limited potential for NA as a remedial/risk reduction option in the studied case, unless some measures for enhancement of TCE and PCE intrinsic biodegradation are applied.Samooczyszczenie (ang. natural attenuation - NA) w przypadku wód podziemnych zanieczyszczonych substancjami organicznymi polega głównie na samoistnej biodegradacji zanieczyszczeń. Oparcie remediacji na naturalnych procesach zakłada osiągnięcie wymaganych efektów oczyszczania specyficznych dla danego terenu przy zachowaniu rozsądnych ram czasowych i kosztów. Takie podejście może być zastosowane jako jedna z opcji likwidacji zagrożenia/remediacji wody podziemnej zanieczyszczonej trichloroetenem (TCE) i tetrachloroetenem (PCE) w rejonie ujęcia Nowa Dęba (południowo-wschodnia Polska). Do oceny możliwości samoistnej biodegradacji TCE i PCE w rejonie Nowej Dęby wykorzystano procedurę opisaną w dokumencie US EPA „Technical protocol for evaluating natural attenuation of chlorinated solvents in ground water”. Dane archiwalne oraz wyniki badań terenowych zostały użyte do opracowania modelu koncepcyjnego transportu zanieczyszczeń od ogniska do receptora. Samoistna biodegradacja była oceniana na podstawie dostępnych parametrów analitycznych (np. stężenia tlenu, azotanów, chlorków oraz pH, TOC i temperatury wody), które uważane są jako wskaźniki rozkładu TCE i PCE. Ocena polegała na przypisaniu odpowiedniej liczby punktów i wag dla poszczególnych parametrów oraz interpretacji uzyskanych wyników w celu sprawdzenia możliwości samoistnej biodegradacji badanych zanieczyszczeń. Stwierdzono brak jednoznacznych dowodów na samoistną biodegradację (dehalogenację redukcyjną) TCE i PCE w wodach podziemnych w rejonie ujęcia Nowa Dęba. Wynika z tego, że w opisywanym przypadku oparcie remediacji wód podziemnych (i likwidacji zagrożenia dla ujęcia wody) na NA jest możliwe pod warunkiem zastosowania metod wspomagających biodegradację TCE i PCE

Applying numerical modeling for designing strategies of effective groundwater remediation.

Selection of effective groundwater remediation scenarios is a complex issue that requires understanding of contaminants’ transport processes. The effectiveness of cleanup measures may be verified by fate and transport numerical modeling. The goal of this work was to present the usefulness of fate and transport modeling for planning, verification and fulfillment of effective groundwater remediation methods. Selection methodology was developed, which is based on results of numerical flow and transport modeling. A field site located in south-east Poland was selected as a case study, in which groundwater contamination of trichloroethene and tetrachloroethene was detected. The results indicated that “pump and treat” was the most effective among the studied remediation methods, followed by permeable reactive barrier and in situ chemical oxidation. Natural attenuation-based remediation was demonstrated to be the least suitable, as it requires the longest time to reach predefined remediation goals, principally due to low sorption capacity and unfavorable hydrogeochemical conditions for biodegradation. Fate and transport numerical modeling allowed simulating different remediation strategies, and thus the decision-making process was facilitated

Sorption and biodegradation parameters of selected pharmaceuticals in laboratory column experiments.

Pharmaceutically active compounds have increasingly been detected in groundwater worldwide. Despite constituting a risk for human health and ecosystems, their fate in the environment has still not been exhaustively investigated. This study characterizes the transport behavior of five selected pharmaceutically active compounds (antipyrine, atenolol, caffeine, carbamazepine and sulfamethoxazole) in two sediments (coarse quartz sand and sandy loam) using column experiments with long-term injection of spiked groundwater. Transport parameters were estimated using an analytical reactive transport model. When five selected compounds were injected simultaneously, transport behavior of antipyrine, carbamazepine and the antibiotic sulfamethoxazole were similar to the conservative tracer in both sediments and under varying redox conditions. Atenolol and caffeine were retarded significantly stronger in the sandy loam sediment than in the coarse quartz sand. Biodegradation of caffeine was observed in both sediments after an adaption period and depended on dissolved oxygen. The identification of biodegradation processes was supported by monitoring of intracellular adenosine triphosphate (ATPitc) as a measure for microbial activity. ATPitc was present in varying concentrations in all sediments and was highest when biodegradation of pharmaceuticals, especially caffeine, was observed. When only caffeine and sulfamethoxazole were injected simultaneously, sulfamethoxazole was degraded while caffeine degradation was reduced. The latter seemed to be influenced by low concentrations in dissolved oxygen rather than the presence of the antibiotic sulfamethoxazole. Results of these experiments emphasize the impact on pharmaceutical sorption and (bio)degradation of sediment type and redox conditions, as well as available time for microbial adaption and the combination of pharmaceuticals that are released together into groundwater

Sorption properties and behaviour at laboratory scale of selected pharmaceuticals using batch experiments.

Despite the increasing public concern about the frequent occurrence of pharmaceuticals in the water bodies, their transport and fate are not yet well known; in particular in groundwater. In this laboratory study, batch experiments were conducted to investigate the sorption behaviour of selected pharmaceuticals. The choice of compounds was motivated by their chemical properties as well as by their occurrence at the relevant field sites. It included: antipyrine, atenolol, caffeine, carbamazepine, ciprofloxacin, diclofenac, ketoprofen, ofloxacin, and sulfamethoxazole. Sorption behaviour has already been investigated for some of these compounds (e.g. carbamazepine), but for the others (e.g. antipyrine, ketoprofen), extensive studies are missing so far. For the experiments, artificial and actual aquifer materials from complementary field sites were selected: technical coarse quartz sand and sediments from alluvial Vistrenque Aquifer, France (sandy loam), and fluvio-deltaic Baix Fluvia Aquifer, Spain (sandy clay loam, clay, and medium sand). In these field sites occurrence of pharmaceuticals in groundwater was previously stated, and the presented laboratory experiments were complementary to the field investigations. Five concentration steps for determining the sorption isotherms were investigated. Correlation analysis showed dependencies of K-coefficients of individual compounds and sediment properties; however, no clear, universal patterns for all compounds were found. Batch experiments suggest that sorption behaviour was governed by compound-specific properties rather than by sediment properties. These results contribute to the understanding sorption behaviour of pharmaceuticals in heterogeneous sediments, although some inconsistencies were revealed between laboratory scale results and field scale observations