A novel multi-electrode system for electrolytic and biological water treatments: electric charge transfer and application to denitrification

A novel multi-electrode system is proposed for electrolytic and biological water treatments. The multi-electrode system is comprised of multiple working electrodes and their counter electrode, where electric current or potential applied to each electrode is controlled independently. Experimental result for different electrolyte solutions showed that electric charge in the system was efficiently carried by dissociative electrolytes such as carbonate ions. This transfer mechanism is regarded as being effective both in keeping pH level around neutrality and in passing certain amounts of electric current especially in dilute solutions such as groundwater and surface water. A long-term (over 500 days) experiment also showed the enhanced and stable denitrification performance of biofilm-electrode reactor (BER) equipped with the multi-electrode system, comparing to former BERs. This superior performance was thought to be attributable to large effective surface area of electrode, the charge transfer mechanism by dissociative electrolyte, and the formation of highly reducing (or oxidizing) zones. From these results, we conclude that the multi-electrode system is useful for electrolytic and biological treatments of groundwater and surface water.     

Determination of labile and strongly bound metals in lake water

Differential pulse anodic stripping voltammetry is applied to differentiate and determine the labile and strongly bound forms of Zn, Cd, Pb and Cu in lake water without preconcentration of the sample. The sensitivities as established for an oxidation peak current of 0·020 μA are: 0·2 ppb for Zn. 0·4 ppb Cd. 0·7 ppb Pb and 0·5 ppb for Cu. For the analysis of a lake water containing 5·0–24·5 ppb of the four metals, the relative S.D. ranged from 1·6 to 10 per cent. Interferences of cations and anions and the choice of a buffer system have been discussed. The method has been applied to study a number of small lakes in the Sudbury area. Ontario.     

Fluid filling of a membrane tube with self-weight

The filling of a membrane tube with self-weight by a fluid is studied theoretically for the first time. The fundamental problem depends on two non-dimensional parameters, $\beta$ and $\gamma$ which represent the importance of internal pressure and membrane self-weight respectively. The nonlinear equations are solved by an efficient numerical integration method. It is found that membrane self-weight has considerable effect on the tube geometry and the tension of the membrane at low filling pressures.     

Prediction of the effectiveness of rolling dynamic compaction using artificial neural networks and cone penetration test data

Rolling Dynamic Compaction(RDC),which is a ground improvement technique involving non-circular modules drawn behind a tractor,has provided the construction industry with an improved ground compaction capability,especially with respect to a greater influence depth and a higher speed of compaction,resulting in increased productivity. However,to date,there is no reliable method to predict the effectiveness of RDC in a range of ground conditions. This paper presents a new and unique predictive tool developed by means of artificial neural networks(ANNs) that permits a priori prediction of density improvement resulting from a range of ground improvement projects that employed 4-sided RDC modules;commercially known as"impact rollers". The strong coefficient of correlation(i.e. R0.86) and the parametric behavior achieved in this study indicate that the model is successful in providing reliable predictions of the effectiveness of RDC in various ground conditions.     

Field measurement of the air flow characteristics of big mechanically ventilated spaces

Air speeds induced by mechanical ventilation systems in the occupied zone are studied experimentally in seven railway stations in Hong Kong. Values of air speed at different positions are measured. From these values, air speed contours and turbulence intensities are calculated. Macroscopic numbers describing airflow in a space including the Reynolds number and the jet momentum number are estimated and their potential uses are discussed.     

Profiles of mean wind speeds and vertical turbulence intensities measured at seashore and two inland sites using Doppler sodars

The authors’ group has been conducting full-scale measurements of wind velocities with Doppler sodars. It is very important to accurately assess the profiles of mean wind speeds and turbulence intensities in relation to terrain roughness. In this study, the profiles were evaluated for all data measured over a long period at a seashore and two inland sites. It is confirmed that for strong winds the profiles can be approximated by a single power law at altitudes between 50 and 340 m. The power law exponents of the mean wind speed profiles are approximately 0.1 for wind from the sea and 0.2-0.3 for wind blown over land. Those of the turbulence intensity profiles are approximately 0 and −0.2 to 0.4, respectively.     

A research about a method for restoration of traditional lime mortars and plasters: A staging system approach

Turkey is quite rich with historical buildings. Depending on various factors like time, increasing air pollution due to technological improvements of the present era together with insufficiency of inspection leads to the formation of damages on these buildings which are part of our historical heritage. Conservation of such buildings which are as important as historical documents should be the first and foremost target of any project. Where maintenance is insufficient, conservation and restoration attempts should replace it. What is necessary in restoration is the use of material which resembles the original material to the closest degree or, producing appropriate material which is compatible with the properties of the original material. The first dimension of the current problem is the insufficiency of resources while the second dimension stems from the lack of proper evaluation of the material to be used in conservation and restoration. This study defines the importance of mortars and plasters along with their history and the reasons of deterioration. In addition, it sets up the information flow of mortar and plaster within a systematic decision making process. The necessary experimental methods for the production of new repair mortar or plaster that can be used in determining the character analysis of original mortar and deterioration morphology are also analyzed. Thus, a method that can be used in the conservation and restoration studies is determined with this paper.     

Essais d'aerateurs: Enseignements tires de 500 essais en eau claire effectues dans 200 stations d'epuration differentes—II ResultatsTests on aerators: Conclusions drawn from 500 clean water tests conducted in 200 different sewage treatment plants—II Data interpretation

The large number of aerator tests conducted in the field by the CEMAGREF teams has allowed developing a critical review of tests results by means of statistical analysis. Measurement quality is estimated from the variation of the transfer coefficient values from one sampling point to another. Individual transfer coefficient values $\text{(}\text{K}{}_{\mathrm{L}}\text{a)i}$ are compared with the average value of the test $\text{(}\text{K}{}_{\mathrm{L}}\text{a). (K}{}_{\mathrm{L}}\text{a)i/}\text{K}{}_{\mathrm{L}}\text{a}$ ratios correlating with one year's data are gathered in histogramms (Fig. 1).A χ² test is used for evaluating the fit of a Normal distribution on each histogram (Tables 1 and 2 results for two kinds of surface aerators). When the Normality is not rejected, the variances between distributions are compared by means of a Fisher test.$\text{(K}{}_{\mathrm{L}}\text{a)i/}\text{K}{}_{\mathrm{L}}\text{a}$ variations in a same run are independent of transfer coefficient when the K_La ranges 1–10 h^?1 and applied specific power ranges 15–70 W m^?3. Those variations allow evaluating the technique of measuring, the reliability of oxygen probes and the operator's experience (Table 3).In a well mixed tank and when the recommended procedure is correctly implemented the relative error in measuring the specific oxygen input (kg O₂ kWh^?1) is 5%. In less favorable cases it reaches 10%.Tables 4 and 5 show the reproductibility of repetitive run results in the same plant and of tests performed with the same aerator in different plants.The histograms of the performances of the main types of mechanical surface aerators (high speed vertical shaft turbine, slow speed vertical shaft turbine, horizontal shaft aerator) are presented (Figs 2, 4, 5). Relations between oxygenation capacity and specific power consumption are plotted in Figs 3 and 6. As to other aeration systems, fewer data are available. Table 6 summarizes the usual range of performances.In 1974, after a series of measurements performed on 72 different plants, CEMAGREF stated that the oxygenation capacities claimed by manufacturers were, on the average, 40% higher than actual results. Now, the performances predicted by manufacturers in France are generally very close to the measured values. A difference higher than 10% between predicted values and measured ones now occurs as an exception.     

Sorption of phosphorous to Filtralite-P--the effect of different scales

Sorption of P to the filter material Filtralite-P was examined at a small, medium and large scale. In the small- and meso-scale laboratory models, the sorbed amount of total phosphorus (P) was heterogeneously distributed with more P sorbed in the inlet zone and the bottom layers. The full-scale system had, on the other hand, the highest sorbed concentration in the outlet region. The overall P sorption capacity of the material was 8030, 4990 and 521 mg P kg(-1) Filtralite-P for Box 1, Box 2 and meso scale, respectively. This equals 4.4, 2.8 and 0.29 kg P m(-3) material, respectively. However, the maximum sorption capacities found were 2500, 3887 and 4500 mg P kg(-1) Filtralite-P for the two small-scale box systems and the meso-scale container, respectively. In the full-scale system the overall P sorption capacity of the material was 52 mg P kg(-1) Filtralite-P (0.029 kg P m(-3) Filtralite-P with a maximum sorbed amount of P of 249 mg P kg(-1). Results from both the small- and meso-scale system show that when a constructed wetland (CW) is saturated, i.e. when the outlet concentration has reached its maximum allowed concentration of 1.0 mg P l(-1), only parts of the filter material will have reached the sorption capacity. Sequential extractions of Filtralite-P showed that the loosely bound P, Ca-P and Al-P were the primary P sorption pools both in the small-scale models and in the full-scale CW. However, the proportion of these three fractions varied with time and change in pH. A white product precipitated in the outlet zone of both the small-scale box models as well as the onsite CW. The surface of these precipitation particles was identified by X-ray diffraction and SEM method as CaCO3 and precipitated Ca- and Mg-phosphates.     

Evolution of pH, organic matter and (226)radium/calcium partitioning in U-mining debris following revegetation with pine trees

Natural attenuation processes resulting from the afforestation of some U-waste rock piles have the potential to limit the linkage of radioelements and other trace pollutants, thereby minimizing exposure risks. We determined the evolution of pH and organic matter and compared the (226)Ra and Ca extractability in pyrite-containing mining debris which was revegetated 35 years ago with Scots pine. Oxidation of sulphidic minerals remaining in the substrate appeared to dominate over acidification processes due to vegetation inputs and litter decomposition. The accumulation of organic matter in forest floor had a negligible effect on the (226)Ra upward recycling compared to the migration losses observed mainly from decarbonatation of the surface mining debris. (226)Ra was overall less soluble than Ca in the soil profile but NH(4)Ac-pH 5 had the capacity to extract a (226)Ra fraction of 31.1-41.5%, i.e. at least twice as much as for Ca. In deeper layers, a majority of both Ca and (226)Ra were extractable from the same non-specific adsorption pool, which mainly involved carbonate. In the upper acidified layer, the incorporation of organic matter had no effect on (226)Ra extractability. A further specific adsorption pool for (226)Ra was attributed to the formation of sparingly soluble Fe-Al oxyhydroxides. However, that specific (226)Ra-bearing phase was readily dissolved in NH(4)Ac-pH 5, indicating a relatively reversibility of the precipitation reaction of (226)Ra with amorphous oxide. Trees are effective at reducing hydrological release of many pollutants but in the mining debris studied, four decades of pine growth did not significantly promote (226)Ra remediation in the soil.