The reliability of a microbial fuel cell (MFC) system was tested on an industrial scale by operating a 1,000-L single-chamber system under real conditions at a municipal wastewater treatment plant ...(WWTP) over a 6-month period. Submergible multi-electrode modules with large-scale grid-segmented gas diffusion cathodes with activated carbon as a catalyst were used. Maximum power densities normalised to the cathode area were above 100 mW m
. Fluctuating chemical and physical wastewater characteristics of the influent had reversible effects on MFC performance in terms of energetic efficiency. Thereby, the composition of the chemical oxygen demand (COD) fractions changes only insignificantly and the concentration of readily biodegradable (S
) required for the enhanced biological phosphorus removal (EBPR) process or upstream denitrification was reduced by 41 ± 10 mg L
(37 ± 2% of inflow S
).
In this article, we briefl y survey studies of the nature of expertise, and we present the results of research directed at evidence of the complicated nature of expertise, which is most eff ectively ...seen in experts' use of a transfer mechanism. The phenomenon of the transfer of verbalized operational senses (VOS) is analyzed and is investigated on the basis of the sense theory of thinking, as proposed by Tikhomirov (1969, 1984). It is shown that VOS transfer manifests itself in diverse forms. It seems to be dependent on the factors of chess position and the age and skill level of the player. Diverse forms of transferring are associated with a change in separate indices of VOS volume, structure, depth, and degree of consciousness in a connected position. VOS transfer is found more in skilled than in unskilled chess players; skilled players demonstrate selectivity of search in a connected position. VOS transfer is associated not simply with the repetition and copying of some forecasts, which give the direction of search, but also with using and transforming the results of previous verbal searches.
A second order kinetic model for simulating chlorine decay in bulk water due to the reaction with dissolved organic matter (DOM) was developed. It takes into account the decreasing reactivity of ...dissolved organic matter using a variable reaction rate coefficient (VRRC) which decreases with an increasing conversion. The concentration of reducing species is surrogated by the maximum chlorine demand. Temperature dependency, respectively, is described by the Arrhenius-relationship. The accuracy and adequacy of the proposed model to describe chlorine decay in bulk water were evaluated and shown for very different waters and different conditions such as water mixing or rechlorination by applying statistical tests. It is thus very well suited for application in water quality modeling for distribution systems.
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•A second order variable reactivity bulk chlorine decay model was developed.•The model considers the impact of initial chlorine dose and temperature.•The model applies for rechlorination and water mixing conditions.•The model needs no further calibration.•The model adequacy was demonstrated using statistical tests.
The effect of chess skill, age, and conditions for memorization on the efficiency of the recall of sequences of opening chess moves was studied. Thirty-nine chess players of different skill levels ...(from category 2 to grandmaster) and ages (from 17 to 81 years old) were divided into four groups (ELO > 2000 before and after the age of 40; ELO < 2000 before and after the age of 40). They were asked to remember the sequences of moves under three conditions (passive perception, use of imagination, physical generation of moves) and to recall (reproduce) the sequences by making the moves. It turned out that in the passive-perception condition the younger chess players, on the one hand, and the more highly skilled players, on the other, recalled the moves significantly better than did the other groups. Also, in almost all the groups of players the efficiency of memory grew as the condition for memorization and that for reproduction converged, with the highest growth rate found among chess players older than 40 years with ELO > 2000. The current memory of the chess experts was to a greater extent mediated by opening schemes and knowledge than was that of the intermediate players. A hypothesis about the activity specificity of the coding in episodic memory was confirmed and concretized.
Chemical weathering of mafic rocks represents substantial sink of atmospheric CO2 yet the mechanismes of this process in high-latitude regions are poorly understood. This work addresses geochemical ...migration and partitioning of major and trace elements between rock, soil and surface waters during chemical weathering of mafic rocks and soil formation under the influence of a glacial moraine in the northwestern Russian subarctic. We used multidisciplinary approach which included major and trace element chemical analysis, Sr isotopic measurements, and mineralogical structural and microscopic investigations. Quaternary (Pleistocene) deposits were observed even in the deepest horizons of soil profiles and confirm a strong moraine influence as most soils showed podzolic features. Chemical and Sr isotopic analyses revealed a strong impact of the moraine on soil chemistry and mineralogy. Mineralogical studies showed the presence of non-aeolian quartz and zircon in soils which were not linked to the nature of the parental rocks (i.e. mafic and felsic). At the same time, we observed the presence of etch pit corrosion on the surface of zircons and feldspars, and a newly-formed matter adjacent to the surface of primary phases. The chemical index of alteration (CIA) showed weak or no weathering of rocks within the soil profile and the weathering intensity scale confirmed the “felsic” chemical composition of soils developed over mafic and ultramafic rocks. Analysis of Sr radiogenic isotopes demonstrated preferential removal of easily weatherable and less radiogenic minerals over the full depth of soil profile and a more radiogenic signature of the granitic moraine compared to mafic and felsic bedrocks. The composition of most surface waters reflected the weathering of silicate rocks but did not allow for distinguishing purely mafic source. The chemical weathering rates of ultramafic rocks were calculated to be higher than those for the granitic till, but the moraine depositions which dominate this region hide evidence of the real weathering process. This could be due to retention of Mg and Ca in soil due to precipitation of secondary phases such as Mg-vermiculite or divalent cation adsorption on mineral, organic or organo-mineral phases. As a result, weathering rates estimated for the olivinite rock appear to be lower than the weathering rates of mafic rocks reported in other boreal and subarctic regions. Overall, the felsic moraine deposits are capable to sizably decrease the weathering intensity of mafic rocks which should be taken into account for chemical weathering modelling of high-latitude regions subjected to glaciation in the past.
Chemical weathering of mafic rocks under granitic moraine in the subarctic. Display omitted
In this study, a 1000 L pilot scale internal loop airlift bioreactor was operated and compared to a mathematical model to determine the best design for optimal supply of oxygen for nitrification and ...sufficient air for biomass fluidization. The design model is based on parameters such as geometry, carrier density, and airflow of the 1000 L pilot scale bioreactor. The model predicts a range of superficial air velocities (0.009–0.013 m/s) under which the airlift bioreactor was fluidized. Three superficial air velocities (0.009 m/s, 0.011 m/s and 0.013 m/s) were experimentally tested in the pilot plant and the obtained circulation velocities were compared with the predicted design scenarios. The predicted velocity was in agreement with the measured velocity. The aim of the mathematical model and the calculations of different geometry scenarios was to define the optimal geometry design for the physical model. The results show that the ratio of the cross-sectional area between the riser and the downcomer of 1.33 resulted in the lowest superficial liquid velocity of 0.076 m/s in the riser at a relative low superficial air velocity of 0.011 m/s and a carrier density of 1030 kg/m3. This bioreactor design enabled longest retention time of particles in the oxygenated riser.
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•Low growth rate and competing heterotrophs continue to challenge nitrification.•Low liquid velocity and higher carrier fraction in riser enhance nitrification.•A three phase ...mathematical model was applied for predicting low liquid velocity.•Geometry, aeration, and carrier characteristics were major design criteria.•Construction of a 1000L pilot plant verified the design and liquid velocity.
In this study, a 1000L pilot scale internal loop airlift bioreactor was operated and compared to a mathematical model to determine the best design for optimal supply of oxygen for nitrification and sufficient air for biomass fluidization. The design model is based on parameters such as geometry, carrier density, and airflow of the 1000L pilot scale bioreactor. The model predicts a range of superficial air velocities (0.009–0.013m/s) under which the airlift bioreactor was fluidized. Three superficial air velocities (0.009m/s, 0.011m/s and 0.013m/s) were experimentally tested in the pilot plant and the obtained circulation velocities were compared with the predicted design scenarios. The predicted velocity was in agreement with the measured velocity. The aim of the mathematical model and the calculations of different geometry scenarios was to define the optimal geometry design for the physical model. The results show that the ratio of the cross-sectional area between the riser and the downcomer of 1.33 resulted in the lowest superficial liquid velocity of 0.076m/s in the riser at a relative low superficial air velocity of 0.011m/s and a carrier density of 1030kg/m3. This bioreactor design enabled longest retention time of particles in the oxygenated riser.
Natural colloid separation at different pH using dialysis membrane allows quantitative evaluation of trace element complexation. Display omitted
► Dialysis assessed the distribution of trace elements ...(TEs) between colloidal and dissolved (<1kDa) phases. ► Proportion of colloidal forms was measured as a function of solution pH (from 3 to 8). ► Two groups of elements can be distinguished according to their behaviour during dialysis. ► Results allow prediction of colloidal form proportion in organic- and Fe-rich boreal waters.
A dialysis procedure was used to assess the distribution coefficients of ∼50 major and trace elements (TEs) between colloidal (1kDa–0.22μm) and truly dissolved (<1kDa) phases in Fe- and organic-rich boreal surface waters. These measurements allowed quantification of both TE partitioning coefficients and the proportion of colloidal forms as a function of solution pH (from 3 to 8). Two groups of elements can be distinguished according to their behaviour during dialysis: (i) elements which are strongly associated with colloids and exhibit significant increases of relative proportion of colloidal forms with pH increase (Al, Ba, Cd, Co, Cr, Cu, Fe, Ga, Hf, Mn, Ni, Pb, rare earth elements (REEs), Sr, Th, U, Y, Zn, Zr and dissolved organic C) and (ii) elements that are weakly associated with colloids and whose distribution coefficients between colloidal and truly dissolved phases are not significantly affected by solution pH (As, B, Ca, Cs, Ge, K, Li, Mg, Mo, Na, Nb, Rb, Sb, Si, Sn, Ti, V). Element speciation was assessed using the Visual MINTEQ computer code with an implemented NICA-Donnan humic ion binding model and database. The model reproduces quantitatively the pH-dependence of colloidal form proportion for alkaline-earth (Ba, Ca, Mg, Sr) and most divalent metals (Co, Cd, Mn, Ni, Pb, Zn) implying that the complexation of these metals with low molecular weight organic matter (<1kDa fraction) is negligible. In contrast, model prediction of colloidal proportion (fraction of 1kDa–0.22μm) of Cu2+ and all trivalent and tetravalent metals is much higher than that measured in the experiment. This difference may be explained by (i) the presence of strong metal-binding organic ligands in the <1kDa fraction whose stability constants are several orders of magnitude higher than those of colloidal humic and fulvic acids and/or (ii) coprecipitation of TE with Fe(Al) oxy(hydr)oxides in the colloidal fraction, whose dissolution and aggregation controls the pH-dependent pattern of TE partitioning. Quantitative modeling of metal – organic ligand complexation and empirical distribution coefficients corroborate the existence of two colloidal pools, formerly reported in boreal surface waters: “classic” fulvic or humic acids binding divalent transition metals and alkaline-earth elements and large-size organo-ferric colloids transporting insoluble trivalent and tetravalent elements.
This study focuses on the effect of rapid mixing on the coagulation efficiency in a full-scale drinking-water treatment plant and discusses the mechanisms involved in the floc-formation process. The ...results refer to three periods of operation of the waterworks when no mechanical mixing was provided in the tanks for coagulant dosing due to mechanical failure of the rapid mixers. Although a certain deterioration of the subsequent flocculation process was observed, as assessed using the data for suspended solids, turbidity, and chemical oxygen demand, the overall water treatment performance was not affected. This suggests an insignificant role for intense rapid mixing in sweep flocculation during full-scale water treatment and reveals the potential to reduce the required energy costs for mechanical mixers.
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