p-Nitrophenol removal by combination of powdered activated carbon adsorption and ultrafiltration - comparison of different operational modes

Ultrafiltration is classified as a low-pressure membrane technology which effectively removes particulate matter and microorganisms and to a certain extent dissolved organic matter (15-25%) and colour. The technology has been optimized and is becoming competitive compared to conventional processes for larger scale plant capacities. In combination with activated carbon it is an effective barrier regarding the removal of synthetic organic chemicals. Growing interest in ultrafiltration raises the question of better usage of the adsorption capacity of powdered activated carbon (PAC) used in combination with this low-pressure membrane technique. This paper presents a pilot plant study of different PAC dosing procedures within a combined hybrid membrane IN/OUT process for removal of p-nitrophenol (PNP) from water (c(0)=1mg/L) under real case conditions (e.g. usage of the same module for the whole duration of the experiment, backwashing with permeate water, no separate saturation of the membrane with substance without presence of carbon). p-Nitrophenol was chosen as an appropriate test substance to assess the efficiency of different operation modes. Dead-end and cross-flow filtration were compared with respect to different PAC dosing procedures: continuous dosing into a continuously stirred tank reactor (CSTR) in front of the module and direct dosing into the pipe in front of the module (continuous, single-pulse and multi-pulse dosing). There was no advantage in cross-flow mode over dead-end referring to PNP concentration in the permeate. Relating to the carbon dosing procedure, the best results were obtained for continuous PAC addition. The option of dosing directly into the pipe has the advantage of no additional tank being necessary. In the case of single-pulse dosing, the formation of a carbon layer on the membrane surface was assumed and an LDF model applied for a simplified estimation of the "breakthrough behaviour" in the thus formed "PAC filter layer".     

Stress responses investigated; application of zinc and heat to Terrestrial Model Ecosystems from heavy metal polluted grassland

This study tested the hypothesis that soils with a deprived biodiversity due to metal pollution are less stable than non-polluted soils, containing a more diverse community. For this, soils were sampled from specific grasslands in the Netherlands that contain elevated heavy metal concentrations (Cu, Pb and Zn). Soils that showed the largest differences in metal concentrations were incubated in the laboratory using Terrestrial Model Ecosystems (TMEs). This approach enabled simultaneous measurement of structural (bacteria, nematodes, enchytraeids, earthworms) and functional parameters (nitrogen leaching, feeding activity, CO₂ production, plant growth). The highest polluted soils showed a lower bacterial growth, and decreased enchytraeid and nematode biomass and diversity, hence a deprived community. More nitrate leached from high polluted soils, while all other functional endpoints did not differ. Additional stress application of zinc and heat was used to test the stability. Zinc treatment caused effects only in the higher polluted soils, observed at several moments in time for enchytraeids, CO₂ fluxes and plant growth. Heat stress caused a large reduction in enchytraeid and earthworm biomass. Ammonium leaching was decreased by heat treatments in the most polluted soils, while CO₂ was increased by heat in less polluted soils. Most effects were seen in the most polluted systems and it was concluded that they seem less stable.     

外墙外保温面层体系用防水抗裂砂浆性能实验研究

通过测试外墙外保温面层体系防水抗裂砂浆的工作性、吸水率、力学性能和耐久性能,综合评价了掺不同防水剂后防水抗裂砂浆的防水性能,并推荐有效的有机硅防水剂品种,为实际工程提供借鉴.     

Regulation through comparative performance evaluation

Ofwat used comparative performance regulation in the 1994 periodic review of prices. We consider such a regulatory mechanism when there are technological spillovers. The regulator cannot observe firms effort and must design a regulatory contract which induces the socially optimal level of cost reduction. The extent to which cost reducing activities are non-appropriable is shown to affect the optimal choice of regulation. In general, comparative performance regulation is optimal and yardstick competition emerges only as a special case. However, when spillovers are spread evenly across an industry, an optimal comparative regime does not exist.     

Mobilisation of heavy metals by deicing salts in a roadside environment

The seasonal variations of some selected heavy metals (Cd, Cu, Pb and Zn) and principal anions in soil solutions were monitored as a function of distance from the road at two field sites in Sweden. During the winter, the conductivity, concentrations of dissolved sodium and chloride increased dramatically due to the application of deicing agents (i.e. NaCl). Due to ion exchange, the pH decreased one unit in the soil solutions, whereas the concentrations of total organic carbon decreased due to coagulation and/or sorption to stationary solids. The heavy metal concentrations increased during the winter, but through different mechanisms. Cadmium concentrations in the aqueous phase increased as a response to ion exchange, possibly also enhanced by the formation of chloride complexes. Similarly, the concentrations of zinc increased, due to ion exchange, with calcium and protons. The mechanisms of mobilisation for copper and lead were not that clear probably due to association with coagulated or sorbed organic matter in combination with colloid dispersion.     

Drei Jahre Zeitschrift Grundwasser

Liebe Leserinnen und Leser, die Zeitschrift Grundwasser hat mit dem vorliegenden Heft 4 des Jahrganges 1998 ihr drittes Jahr seit dem ersten Erscheinen vollendet. Zum ersten Mal werden in dieser Ausgabe vier Artikel ver?ffentlicht, die thematisch eng zusammenh?ngen. Alle Beitr?ge sind aus Untersuchungen im Rahmen des DFG-Schwerpunktes “Geochemische Prozesse mit Langzeitfolgen im anthropogen beeinflu?ten Sickerwasser und Grundwasser” hervorgegangen und beleuchten die unterschiedlichen Aspekte der hydrogeologischen, hydrochemischen und bodenkundlichen Untersuchungen im Rahmen von BTEX-Schadensf?llen, von der Charakterisierung des Schadstoffherdes im Boden und im Grundwasser über die Bestimmung der hydraulischen Verh?ltnisse in einem Lockergesteins-Grundwasserleiter bis hin zur Schadstoffemission. Wir sind der überzeugung, damit ein abgerundetes Bild eines praxisorientierten Forschungsprojektes exemplarisch darstellen zu k?nnen, das die aktuelle Forschung an die Anwender heranführen kann. Das vorliegende Heft unterscheidet sich somit grunds?tzlich von den bisherigen Ausgaben, in denen Beitr?ge im Gro?en und Ganzen so abgedruckt wurden, wie sie eingereicht und vom Reviewproze? bewertet wurden. Auch wenn das Bild der Zeitschrift Grundwasser in Zukunft weiter vornehmlich durch eine m?glichst gro?e Vielfalt von Beitr?gen aus Praxis und Forschung bestimmt werden soll, zeigt sich aus der nun eingeleiteten Entwicklung, da? die Anfangsphase der Zeitschrift damit als beendet betrachtet werden kann. In den ersten Jahrg?ngen war die Hauptsorge des wissenschaftlichen Redakteurs der Eingang einer ausreichenden Zahl von qualitativ hochwertigen Fachbeitr?gen. Bei dem noch geringen Bekanntheitsgrad der Fachzeitschrift wurden einige Hefte gedruckt ohne zu wissen, welche Beitr?ge in das n?chste Heft aufgenommen werden. Die Redaktion lebte oft von der Hand in den Mund, und die Arbeit konzentrierte sich immer auf die letzten Wochen vor dem Erscheinen. Auch mu?te sich das Zusammenspiel zwischen der wissenschaftlichen Redaktion und der Redaktionsleitung erst einstellen. Der Eingang an wissenschaftlichen Beitr?gen hat sich in dem letzten Jahr deutlich positiv entwickelt. W?hrend in den Jahren zuvor auf zwei ver?ffentlichte Beitr?ge ein abgelehnter Beitrag kam und damit die der Zeitschrift zur Verfügung stehenden Seiten ausgesch?pft wurden, ist abzusehen, da? in Zukunft mehr gute Manuskripte eingehen, als Platz in der Zeitschrift ist. Aus dieser an sich wünschenswerten Entwicklung wird es m?glich werden, einen thematischen Mix in den einzelnen Heften herzustellen oder fachlich verwandte Artikel gemeinsam zu publizieren. L?ngerfristig ist darüber hinaus zu überlegen, ob die Fachsektion Hydrogeologie mit dem Verlag über eine Ausweitung des j?hrlichen Seitenkontingentes verhandeln sollte. Alles in allem sind dies positive Zeichen, die zeigen, da? die Zeitschrift eine weite Akzeptanz erreicht hat, so da? die Funktion des wissenschaftlichen Editors nunmehr wechseln kann. Ab dem ersten Heft 1999 wird Frau Prof. Dr. Margot Isenbeck-Schr?ter, Heidelberg, für den wissenschaftlichen Teil der Zeitschrift verantwortlich zeichnen. Ich hoffe mit meiner Arbeit der Zeitschrift über die ersten Jahre einen guten Start gegeben zu haben und bin sicher, da? meine Nachfolgerin in dem bisherigen Sinne, aber hoffentlich auch mit eigenen neuen Impulsen diese ehrenamtliche und zeitaufwendige Arbeit fortsetzen wird. Ich m?chte mich an dieser Stelle sehr herzlich bei alen bedanken, die mit dazu beigetragen haben, da?Grundwasser so erfolgreich gestartet ist (eine Aufz?hlung erübrigt sich, denn Sie k?nnen die Namen auf der anschlie?enden Seite nachlesen) und hoffe, mich auch weiterhin für die Zeitschrift engagieren zu dürfen.     

Natürliche Schadstoffrückhalteprozesse für Arsen und Kupfer am Standort einer ehemaligen Buntfarbenfabrik

The sharply confined pattern of arsenic groundwater contamination at the site of a historic dye factory suggests that natural attenuation processes are active and efficient. The supporting data included sequential soil extractions combined with analyses of other soil properties like carbonate content, the loss of ignition and cation exchange capacity and the extraction characteristics of the original dye pigment. The results point to iron oxides and iron hydroxides as the most important adsorbers for copper and arsenic. The attenuation of copper can be estimated to be very efficient mainly due to its pH-controlled low solubility. Besides the specific adsorption to iron oxides, however, arsenic exhibits a rather large, loosely bound and easily exchangeable fraction. The speciation of arsenic in groundwater is dominated by As(V). The oxidation state of the original pigment is As(III). In some parts of the aquifer where suboxic conditions prevail, this oxidation state is conserved. In oxic zones of the aquifer, oxidation to the pentavalent form As(V) takes place.     

Multilayer carbon foils for cyclotron beam extraction

The TRIUMF Applied Technology Group operates high-power industrial cyclotrons for commercial radioisotope production. Two of these cyclotrons, TR30-1 and TR30-2, are capable of accelerating H⁻ ions to an energy of 30 MeV and beam currents in excess of 1000 μA. For many years, amorphous carbon foils of approximately 2.0 μm thickness have been utilized to extract proton beams from these accelerators.Novel multilayer foils consisting of layers of amorphous and diamond-like carbon (DLC) of 2.0±0.2 μm thickness were manufactured in-house by carbon arc and pulsed laser deposition, respectively. In the TR30 cyclotrons, the new composite foils with 25% DLC content show a three times longer lifetime than the purely amorphous foils, while maintaining their excellent physical and mechanical characteristics during irradiation.     

Estimation of the surface normal velocity of high frequency ultrasound transducers

This paper is concerned with the characterization of the true locally resolved surface normal velocity of an assumed piston-type ultrasonic transducer. Instead of involving a very complicated direct pointwise measurement of the velocity distribution, an inverse problem is solved which yields a spatially discretized weighting vector for the surface normal velocity of the transducer. The study deals with a spherically focused high frequency transducer, which is driven in pulse-echo mode. As a means of posing the inverse problem, the active transducer surface is divided into annuli of equal surface so that for each annulus the spatial impulse response can be calculated. An acrylic glass plate acts as a simple structured target. The resulting ill-posed nonlinear inverse problem is solved with an iterative regularized Gauss-Newton algorithm. The solution of the inverse problem yields an estimated weight for the surface normal velocity for each annulus. Experimental results for a thin copper wire target are compared to simulation results for both uniform and estimated surface normal velocities.