Final report of the preliminary study of the project “The role of microbiological biofilm communities for degradation of sprayed concrete in subsea tunnels”

There are today over 30 subsea tunnels in Norway. These tunnels, built since the early 1980’s, connect islands and peninsulas in the fjord dominated landscape. Several new subsea tunnels are also planned in the near future, within the ferry-free coastal route E39 project. This report summarizes the activities of the pre-study for the project 10 "The role of microbiological biofilm communities for degradation of sprayed concrete in subsea tunnels"

Dynamical transitions and sliding friction in the two-dimensional Frenkel-Kontorova model

The nonlinear response of an adsorbed layer on a periodic substrate to an external force is studied via a two dimensional uniaxial Frenkel-Kontorova model. The nonequlibrium properties of the model are simulated by Brownian molecular dynamics. Dynamical phase transitions between pinned solid, sliding commensurate and incommensurate solids and hysteresis effects are found that are qualitatively similar to the results for a Lennard-Jones model, thus demonstrating the universal nature of these features.Comment: 11 pages, 12 figures, to appear in Phys. Rev.

Evolution of Non-Equilibrium Profile in Adsorbate Layer under Compressive Strain

We investigate the time evolution of an initial step profile separating a bare substrate region from the rest of the compressively strained adsorbate layer near a commensurate to incommensurate transition. The rate of profile evolution as a function of the mismatch, coverage and the strength of the substrate potential are determined by Brownian molecular dynamics simulations. We find that the results are qualitatively similar to those observed for the Pb/Si(111) system. The anomalously fast time evolution and sharpness of the non-equilibrium profile can be understood through the domain wall creation at the boundary and its subsequent diffusion into the interior of the adsorbate layer.Comment: 6 pages, 7 figures, Tribology Letter

Seasonal variations in acidogenic fermentation of filter primary sludge

Primary treatment of municipal wastewater by rotating belt filtration followed by hydrolysis and acidogenic fermentation of the filter primary sludge (FPS) at ambient temperature was studied at pilot-scale during one year. The seasonal variations of volatile fatty acids (VFAs), nutrient release and soluble COD production as well as microbial community assembly were assessed, leading to novel findings for fermentation at ambient temperature. The reproducibility of VFA production performance was first established by operating the two fermentation reactors under the same conditions, showing similar results regarding VFA production and microbial community structure. One year of operation at 5 d retention time (RT) and 16–29 \ub0C resulted in an average VFA yield of 180\ub135 mg COD/g VSin and soluble COD yield of 242\ub140 mg COD/g VSin. The VFA formation was temperature-dependent, with ϴ=1.033\ub10.005 (r=r20\ub7Θ(T−20∘C)). The seasonal variations of the acetic and propionic acid productions were pronounced, whereas the productions of VFAs with longer chains were more stable regardless of temperature. The community structure of the reactor microbiomes was also clearly affected by season and temperature and linked with the production spectrum of VFAs. The ammonium and phosphate releases were stable during the year, leading to a decrease in ratios of soluble COD to NH4+-N and PO43−-P during winter. The soluble COD yield was 11% and 27% higher at 5 d RT compared to 3 and 2 d RT respectively, but the corresponding volumetric productivities were lower. The dissimilarities between microbiomes in influent FPS and fermenters were significant even at a short RT of 2 d, and increased with longer RT of 3 and 5 d, primarily caused by selection of bacteria within Bacteroidota in the fermentation reactors

Förplaneringsstrategins påverkan på gallringsskördarens produktivitet

Sedan slutet av 60-talet och början av 70-talet har snitsling använts för att planera skogsbruksåtgärder och tydliggöra gränser som annars kan verka otydliga. Genom att märka upp träd med snitselband i olika färger och med olika betydelse lämnas ett budskap till de aktörer som ska vidta åtgärder i skogsbeståndet. Det flesta skogsbruksåtgärder som utförs idag planeras med snitselband. I dagsläget är planering med snitselband tids- och resurskrävande och planerarna GPS-loggar samtidigt som det hänger snitselband under planeringens gång. Frågan är om det räcker med enbart GPS-loggning. En undersökning har därför genomförts i syfte att undersöka skillnader mellan prestationen hos skördare i gallring på traditionellt snitslade och GPS-loggade trakter jämfört med trakter som enbart är GPS-loggade. Genom att undersöka homogena trakter där den ena är snitslad och den andra enbart är GPS-loggad kan data från skördaren jämföras för att se dels om prestationen hos maskinen sjunker vid osnitslade trakter och dels om maskinen håller sig innanför de avgränsade områdena. Resultatet visar att samplet i undersökningen var för litet för att kunna användas till att dra några säkra slutsatser. Trots detta syns ändå en viss tendens i siffrorna. Prestationen hos skördaren på de trakter som inte är snitslade visar en lika eller något lägre prestation på samtliga trakter. I rapporten går det även att se att skördaren i enstaka fall har svårt att följa GPS-loggarna och därmed råkar köra in på de angränsande och avgränsade områdena. Även om det inte går att dra några säkra slutsatser av denna studie går erfarenheterna att använda för att kunna planera och genomföra en bättre och mer omfattande undersökning i framtiden.Since the late 60s and early 70s, cutting strips have been used to plan forestry measures and clarify boundaries that might otherwise seem unclear. The method is about marking trees with cut strips of different colors and significance to leave a message to proceeding actors. Most forestry measures currently carried out are planned with cutting strips. At present, planning with cutting strips is time and resource consuming and the planners GPS logs at the same time during the planning process. This study will therefore focus on evaluating whether GPS logging alone is sufficient. The purpose of this report is to investigate differences between the performance of harvesters in thinning correlated on cut areas compared to areas that are only GPS-logged. By planning homogeneous areas where one is cut and the other is uncut, the data that the harvester registers can be compared to see if the performance of the machine decreases in uncut areas. The results show that the sample in the survey is too small to be used to draw any conclusions. Even though no conclusions can be drawn, a pattern can be seen in the figures. Because the performance of the harvester in the areas that is not cut shows similar or lower performance in all comparisons. In the report, it is also possible to see that the harvester in individual cases has difficulty following the GPS logs and driving inside the delimited areas. Although it is not possible to draw any conclusions from this report, it is possible to see the shortcomings that existed in this study and evaluate these to be able to do a better and more thorough intended study in the future

Resistance of aerobic granular sludge microbiomes to periodic loss of biomass

Granular sludge is a biofilm process used for wastewater treatment which is currently being implemented worldwide. It is important to understand how disturbances affect the microbial community and performance of reactors. Here, two acetate-fed replicate reactors were inoculated with acclimatized sludge and the reactor performance, and the granular sludge microbial community succession were studied for 149 days. During this time, the microbial community was challenged by periodically removing half of the reactor biomass, subsequently increasing the food-to-microorganism (F/M) ratio. Diversity analysis together with null models show that overall, the microbial communities were resistant to the disturbances, observing some minor effects on polyphosphate-accumulating and denitrifying microbial communities and their associated reactor functions. Community turnover was driven by drift and random granule loss, and stochasticity was the governing ecological process for community assembly. These results evidence the aerobic granular sludge process as a robust system for wastewater treatment

The effect of time and surface type on the composition of biofilm communities on concrete exposed to seawater

Microbially induced deterioration is a threat to concrete infrastructures in marine environments. Complex microbial biofilms form on concrete surfaces exposed to sea water and cause material deterioration. However, the mechanisms determining the composition and the development of the biofilm communities are poorly understood. We designed a mesocosm experiment to determine the influence of concrete surface structure (smooth/rough) and steel fiber reinforcement (presence/absence) on biofilm development over a period of 455 days. This enabled a novel methodology to systematically assess biofilm formation of bacteria on concrete exposed to marine water. The biofilm communities were distinctly different from the planktonic communities in the systems. The alpha diversity increased with time and longer time intervals correlated with higher turnover of taxa. Several taxa within Caulobacterales and Rhodobacterales were identified as early biofilm formers, which decreased in relative abundance and were replaced by taxa within Planctomycetales as the biofilm developed. Throughout the experimental period, concrete surface type influenced the microbial community composition. Some taxa such as Magnetospiraceae, Portibacter, Rubripirellula, and Rhodopirellula, possibly involved in the oxidation and reduction of iron, were for instance more abundant in biofilms on steel-fiber containing concrete. Null models suggested that mainly deterministic factors were shaping the microbial communities with limited importance of stochasticity at shorter time intervals

Effects of storage on mixed-culture biological electrodes

Storage methods are important to preserve the viability and biochemical characteristics of microbial cultures between experiments or during periods when bioreactors are inactive. Most of the research on storage has focused on isolates; however, there is an increasing interest in methods for mixed cultures, which are of relevance in environmental biotechnology. The purpose of this study was to investigate the effect of different storage methods on electrochemically active enrichment cultures. Acetate-oxidizing bioanodes generating a current density of about 5 A m−2 were enriched in a microbial electrolysis cell. The effect of five weeks of storage was evaluated using electrochemical techniques and microbial community analysis. Storage by refrigeration resulted in quicker re-activation than freezing in 10% glycerol, while the bioelectrochemical activity was entirely lost after storage using dehydration. The results showed that the bioelectrochemical activity of bioanodes stored at low temperature could be retained. However, during the re-activation period the bioanodes only recovered 75% of the current density generated before storage and the bacterial communities were different in composition and more diverse after storage than before