Energy efficient demand controlled ventilation in single family houses

This paper presents a strategy for a simple demand controlled ventilation system for single family houses where all sensors and controls are located in the air handling unit. The strategy is based on sensing CO₂-concentration and moisture content in the outdoor air and exhaust air. The CO₂-concentration is used to ensure adequate ventilation during occupancy and the moisture content is used to ensure adequate removal of moisture produced in the house. The ventilation rate can be switched between two flow rates: a high rate and a low rate. The high flow rate is based on existing requirements in the Danish building regulations and the low flow rate is based on minimum requirements in indoor air quality standards. Measurements were performed on an existing single family house where the controls were installed on the existing mechanical ventilation system. The results showed that the ventilation can be reduced to the low rate 37% of the time without significant changes in the CO₂-concentration and moisture level in the house. In theory this gives a 35% saving on electric energy for fans.     

Potential acidifying capacity of deposition experiences from regions with high NH4+ and dry deposition in China

Acid rain may cause soil acidification possibly leading to indirect forest damage. Assessment of acidification potential of atmospheric deposition is problematic where dry and occult deposition is significant. Furthermore, uncertainty is enhanced where a substantial part of the potential acidity is represented by deposition of ammonium (NH(4)(+)) since the degree of assimilation and nitrification is not readily available. Estimates of dry deposition based on deposition velocity are highly uncertain and the models need to be verified or calibrated by field measurements of total deposition. Total deposition may be monitored under the forest canopy. The main problem with this approach is the unknown influence of internal bio-cycling. Moreover, bio-cycling may neutralize much of the acidity by leaching of mainly K(+). When the water percolates down into the rooting zone this K(+) is assimilated again and acidity is regenerated. Most monitoring stations only measure deposition. Lacking measurements of output flux of both NH(4)(+) and NO(3)(-) from the soil one cannot assess current net N transformation rates. Assumptions regarding the fate of ammonium in the soil have strong influence on the estimated acid load. Assuming that all the NH(4)(+) is nitrified may lead to an overestimation of the acidifying potential. In parts of the world where dry deposition and ammonium are important special consideration of these factors must be made when assessing the acidification potential of total atmospheric loading. In China dry and occult deposition is considerable and often greater than wet deposition. Furthermore, the main part of the deposited N is in its reduced state (NH(4)(+)). The IMPACTS project has monitored the water chemistry as it moves through watersheds at 5 sites in China. This paper dwells at two important findings in this study. 1) Potassium leached from the canopy by acid rain is assimilated again upon entering the mineral soil. 2) Nitrification apparently mainly takes place in forest floor (H- and O-) horizon as NH(4)(+) that escapes this horizon is efficiently assimilated in the A-horizon. This suggests that the potential acidification capacity of the deposition may be found in the throughfall and forest floor solution by treating K(+) and NH(4)(+), respectively, as acid cations in a base neutralization capacity (BNC) calculation.     

Accumulation of heavy metals in circumpolar willow ptarmigan (Lagopus l. lagopus) populations

A circumpolar survey of heavy metals in willow ptarmigan liver and kidney revealed considerable variations in Cd content in Canada and Scandinavia. The Cd content in central Canada was comparable with that in Scandinavia and Russia, at least for kidney. However, in both liver and kidney the median for Canada as a whole was much higher than in the other countries. Some Canadian locations had exceptionally high levels, several birds having >50 mg kg(-1) in liver and >400 mg kg(-1) in kidney. In Norway, the Cd content was highest in central mountain areas in south Norway and inland locations in the two northernmost counties. Five locations in central and north Norway showed mean Cd levels in kidney above 100 mg kg(-1). It is difficult to evaluate regional differences in Sweden, but most locations had the same Cd level as moderately contaminated locations in Norway. Cd levels in Russia were comparable to moderately contaminated locations in the other countries. Due to a high intake of willow, naturally rich in Cd, direct comparison of the Cd level in willow ptarmigan from different locations cannot reveal the effects of long-range pollution. The Pb concentration in willow ptarmigan kidney and liver varied significantly in Norway and Canada, but not in Sweden and Russia. Levels in Sweden and Russia were comparable to those in Canada and low levels in Norway. The highest median value from all locations within countries was found in Norway, both in liver and kidney. The highest Pb content was found in south Norway, indicating an effect of long-range pollution in willow ptarmigan. The level in western Canada was significantly higher than in central Canada. The Hg content in liver varied significantly from one location to another in all the countries and in kidney everywhere except Sweden. In Scandinavia, there is no distinct regional pattern. Canada had a significantly higher Hg level in central than western regions in both tissues the opposite of that found for Cd and Pb. Cu and Zn showed significant variations from one location to another in liver and kidney in Canada and Norway, but only in kidney in samples from Sweden. Comparison between western and central Canada revealed a significant difference for Cu in liver, samples from central Canada having more. There are no significant differences from one country to another, but some localities in Canada seem to have higher Cu concentrations in kidney than are found in Scandinavia and Russia.     

Some aspects of the intraregional spatial distribution of local sector activities

This paper focuses on the spatial distribution of economic activities that serve the demands of households within a region. The level of local sector activities is measured by employment per inhabitant. The basic hypothesis relates to how this proportion varies systematically over space for a wide range of geographies, from high values in a city center to low values in areas adjacent to the city center, and asymptotically approaching the average regional level as the distance from the center increases. This defines a curve that we (under quite general conditions) find to be invariant under changes in the spatial residential pattern and the transportation structure. This suggests that relationships of this kind might be a powerful tool in the prediction of regional development.

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Numerische Simulation von Rammarbeiten im Erdwiderstandsbereich von Baugrubenwänden

Numerical simulation of pile driving in the area of soil resistance of pit walls. In‐situ measurements at deep excavations during the construction show that the installation of buoyancy piles for the pit floor leads to large deformations of the pit walls. Today these additional loads caused by the construction of adjacent piles cannot be predicted and often lead to astonishment. The aim of this article is to present a first numerical model to predict the additional loads for the ground and the pit walls in the near field of driven piles. Regarding additional deformations of a pit wall at the Potsdamer Platz due to vibratory pile driving of buoyancy piles the importance of the numerical investigation is described. Nevertheless in the future considerable efforts are necessary to receive recommendations for the construction of pit walls.     

Sulfide-iron interactions in domestic wastewater from a gravity sewer

Interactions between iron and sulfide in domestic wastewater from a gravity sewer were investigated with particular emphasis on redox cycling of iron and iron sulfide formation. The concentration ranges of iron and total sulfide in the experiments were 0.4-5.4mgFeL(-1) and 0-5.1mgSL(-1), respectively. During anaerobic conditions, iron reduction kinetics were investigated and reduction rates amounted on average to 1.32mgFeL(-1)d(-1). Despite the very low solubility of iron sulfide, the reduced iron reacted only partly with sulfide to produce iron sulfide, even when dissolved sulfide was in excess. When a ferric chloride solution was added to sulfide containing anaerobic wastewater, the ferric iron was quickly reduced to ferrous forms by oxidation of dissolved sulfide and the ferrous iron precipitated almost completely as iron sulfide. During aerobic conditions, iron sulfide was oxidized with a half-life period of 11.7h. The oxidation rate of iron sulfide was significantly lower than that reported for the oxidation of dissolved sulfide.     

A review of the Namntall Tunnel project with regard to grouting performance

The 6 km tunnel under the Namntall hill is a part of the Botniabanan railway project in northern Sweden. The tunnels were excavated by means of drilling and blasting and with, for Scandinavian conditions, a normal grouting routine. The grouting is performed to reduce water ingress into the tunnel to the level defined in the contract. When the water ingress requirements proved difficult to meet, it was obvious that the geological and the hydrogeological conditions in the tunnel would dictate the work processes. A distinctive change in rock conditions influenced both grouting performance and seepage into the tunnel. The rock conditions and the grouting were quantified throughout the project and these are summarized in this paper. It can be concluded that the strongest correlation is between the water ingress, the hydrogeological conditions and the density of the zones and the conditions in and around these zones. The paper suggests a different approach to hydrogeological prognosis and the grouting process, such as distribution of grouting classes, increased mixer capacities and regular use of two grouting rounds.     

Design for pressure die casting—A DFM example

The designer makes many maufacturing decisions that influence the production cost and the quality of the product. It is therefore important to ensure that the designer has a good foundation for these decisions. When talking DFM, it is important to realise that there are large differences between companies in how product design and production are carried out. The objective of the present research is to investigate and to improve the communication flow between design and production for a selected area: pressure die casting. This area is characterised by many subcontracting producers, and design and production are therefore often placed at different geographic locations. This makes an efficient communication flow even more important and it also makes the communication interface more visible. This paper discusses how manufacturing considerations are made in different design situations and how information supporting tools should be formed accordingly. Results from an investigation of DFM in a number of pressure diecasting companies and companies that design products for pressure die casting are presented. The investigation focuses on the type, the detailing level and the accessibility of the part information passing from design to production and on the manufacturing guidelines and suggestions coming from production to design.     

Metabolic versatility in full-scale wastewater treatment plants performing enhanced biological phosphorus removal

This study analysed the enhanced biological phosphorus removal (EBPR) microbial community and metabolic performance of five full-scale EBPR systems by using fluorescence in situ hybridisation combined with off-line batch tests fed with acetate under anaerobic–aerobic conditions. The phosphorus accumulating organisms (PAOs) in all systems were stable and showed little variability between each plant, while glycogen accumulating organisms (GAOs) were present in two of the plants. The metabolic activity of each sludge showed the frequent involvement of the anaerobic tricarboxylic acid cycle (TCA) in PAO metabolism for the anaerobic generation of reducing equivalents, in addition to the more frequently reported glycolysis pathway. Metabolic variability in the use of the two pathways was also observed, between different systems and in the same system over time. The metabolic dynamics was linked to the availability of glycogen, where a higher utilisation of the glycolysis pathway was observed in the two systems employing side-stream hydrolysis, and the TCA cycle was more active in the A²O systems. Full-scale plants that showed higher glycolysis activity also exhibited superior P removal performance, suggesting that promotion of the glycolysis pathway over the TCA cycle could be beneficial towards the optimisation of EBPR systems.