Environmental pollution by wastewater from brown coal processing ¬ a remediation case study in Germany

The large scale of the contamination by the former carbo-chemical industry in Germany requires new and often interdisciplinary approaches for performing an economically sustainable remediation. For example, a highly toxic and dark-colored phenolic wastewater from a lignite pyrolysis factory was filled into a former open-cast pit, forming a large wastewater disposal pond. This caused an extensive environmental pollution, calling for an ecologically and economically acceptable strategy for remediation. Laboratory-scale investigations and pilot-scale tests were carried out. The result was the development of a strategy for an implementation of full-scale enhanced in situ natural attenuation on the basis of separate habitats in a meromictic pond. Long-term monitoring of the chemical and biological dynamics of the pond demonstrates the metamorphosis of a former highly polluted industrial waste deposition into a nature-integrated ecosystem with reduced danger for the environment, and confirmed the strategy for the chosen remediation management

Evaluation of Skybox Video and Still Image products

The SkySat-1 satellite lauched by Skybox Imaging on November 21 in 2013 opens a new chapter in civilian earth observation as it is the first civilian satellite to image a target in high definition panchromatic video for up to 90 seconds. The small satellite with a mass of 100 kg carries a telescope with 3 frame sensors. Two products are available: Panchromatic video with a resolution of around 1 meter and a frame size of 2560x1080 pixels at 30 frames per second. Additionally, the satellite can collect still imagery with a swath of 8 km in the panchromatic band, and multispectral images with 4 bands. Using super-resolution techniques, sub-meter accuracy is reached for the still imagery. The paper provides an overview of the satellite design and imaging products. The still imagery product consists of 3 stripes of frame images with a footprint of approximately 2.6 x 1.1 km. Using bundle block adjustment, the frames are registered, and their accuracy is evaluated. Image quality of the panchromatic, multispectral and pansharpened products are evaluated. The video product used in this evaluation consists of a 60 second gazing acquisition of Las Vegas. A DSM is generated by dense stereo matching. Multiple techniques such as pairwise matching or multi image matching are used and compared. As no ground truth height reference model is availble to the authors, comparisons on flat surface and compare differently matched DSMs are performed. Additionally, visual inspection of DSM and DSM profiles show a detailed reconstruction of small features and large skyscrapers

Consistent Multi-View Texturing of Detailed 3D Surface Models

Texture mapping techniques are used to achieve a high degree of realism for computer generated large-scale and detailed 3D surface models by extracting the texture information from photographic images and applying it to the object surfaces. Due to the fact that a single image cannot capture all parts of the scene, a number of images should be taken. However, texturing the object surfaces from several images can lead to lighting variations between the neighboring texture fragments. In this paper we describe the creation of a textured 3D scene from overlapping aerial images using a Markov Random Field energy minimization framework. We aim to maximize the quality of the generated texture mosaic, preserving the resolution from the original images, and at the same time to minimize the seam visibilities between adjacent fragments. As input data we use a triangulated mesh of the city center of Munich and multiple camera views of the scene from different directions

Spatially Regularized Fusion of Multiresolution Digital Surface Models

In this paper, we propose an algorithm for robustly fusing digital surface models (DSMs) with different ground sampling distances and confidences, using explicit surface priors to obtain locally smooth surface models. Robust fusion of the DSMs is achieved by minimizing the L1-distance of each pixel of the solution to each input DSM. This approach is similar to a pixel-wise median, and most outliers are discarded. We further incorporate local planarity assumption as an additional constraint to the optimization problem, thus reducing the noise compared with pixel-wise approaches. The optimization is also inherently able to include weights for the input data, therefore allowing to easily integrate invalid areas, fuse multiresolution DSMs, and to weight the input data. The complete optimization problem is constructed as a variational optimization problem with a convex energy functional, such that the solution is guaranteed to converge toward the global energy minimum. An efficient solver is presented to solve the optimization in reasonable time, e.g., running in real time on standard computer vision camera images. The accuracy of the algorithms and the quality of the resulting fused surface models are evaluated using synthetic data sets and spaceborne data sets from different optical satellite sensors

DSM Accuracy Evaluation for the ISPRS Commission I Image matching Benchmark

sensing community, the Working Group 4 of Commission I: Geometric and Radiometric Modeling of Optical Airborne and Spaceborne Sensors provides on its website http://www2.isprs.org/commissions/comm1/wg4/benchmark-test.html a benchmark dataset for measuring and comparing the accuracy of dense stereo algorithms. The data provided consists of several optical spaceborne stereo images together with ground truth data produced by aerial laser scanning. In this paper we present our latest work on this benchmark, based upon previous work. As a first point, we noticed that providing the abovementioned test data as geo-referenced satellite images together with their corresponding RPC camera model seems too high a burden for being used widely by other researchers, as a considerable effort still has to be made to integrate the test datas camera model into the researchers local stereo reconstruction framework. To bypass this problem, we now also provide additional rectified input images, which enable stereo algorithms to work out of the box without the need for implementing special camera models. Care was taken to minimize the errors resulting from the rectification transformation and the involved image resampling. We further improved the robustness of the evaluation method against errors in the orientation of the satellite images (with respect to the LiDAR ground truth). To this end we implemented a point cloud alignment of the DSM and the LiDAR reference points using an Iterative Closest Point (ICP) algorithm and an estimation of the best fitting transformation. This way, we concentrate on the errors from the stereo reconstruction and make sure that the result is not biased by errors in the absolute orientation of the satellite images. The evaluation of the stereo algorithms is done by triangulating the resulting (filled) DSMs and computing for each LiDAR point the nearest Euclidean distance to the DSM surface. We implemented an adaptive triangulation method minimizing the second order derivative of the surface in a local neighborhood, which captures the real surface more accurate than a fixed triangulation. As a further advantage, using our point-to-surface evaluation, we are also able to evaluate non-uniformly sampled DSMs or triangulated 3D models in general. The latter is for example needed when evaluating building extraction and data reduction algorithms. As practical example we compare results from three different matching methods applied to the data available within the benchmark data sets. These results are analyzed using the above mentioned methodology and show advantages and disadvantages of the different methods, also depending on the land cover classes

Advances in DSM Generation and Higher Level Information Extraction from High Resolution Optical Stereo Satellite Data

The automatic generation of digital surface models (DSM) of urban areas from high and very high resolution (VHR) stereo data from satellites is still a research issue. Image matching algorithms from computer vision have been introduced and adopted to satellite imagery in recent years. These algorithms do not work using local optimisation like area based matching but try to optimize a global cost function. Analysis shows that matching approaches based on epipolar images like semi-global matching (SGM) and new methods using total generalized variation (TGV) yield the best results. Especially satellites like Worldview-2, GeoEye-1 and Pleiades exhibit very high spatial resolution and geometric quality and can therefore be used to generate DSMs with good properties. If several stereo images from one orbit are available, a combination of DSMs generated by different stereo pairs leads to even better results. Using these DSMs, which already show urban area features in high detail, further higher level information can be extracted and new products can be generated. The main focus of this contribution is to present and analyse several derived information products which can be generated using the DSMs generated from satellite stereo data together with panchromatic and multispectral images. In many applications the product of interest is not the DSM but the digital terrain model (DTM), which exhibits not the height of objects like buildings or trees but the underlying terrain. In this paper a selected method and example for generating DTM from DSM is presented. A further issue is to extract real 3D objects like buildings using DSM and the derived DTM data. Different methods have been developed and are presented using typical examples in densely build city areas including validation results. At least larger buildings can be automatically extracted with sufficient accuracy; even the roof shape (gable or flat roof) can be extracted and modelled. Since automatic change detection is generally a very difficult topic in image processing, information on height or 3D properties are of advantage when used in the change detection procedure. Therefore, if stereo data sets from different dates are available, automatic 3D change detection can be performed using the corresponding DSMs. Since the change detection results depend very much on the quality of the DSMs they generally have to be improved using the multispectral information. Two methods have been developed and are shown and compared using examples from dense urban and industrial areas. The presented results show that due to the good data quality and resolution of satellite image data and the corresponding DSMs, it has become feasible to derive higher level and detailed geo-information regarding 3D relevant object classes and change detection

Application des phytotechnologies : état de l'art

Le réseau Européen COST 859 (European Cooperation in the field of Scientific and Technical Research) " Phytotechnologies to promote sustainable land use and improve food safety " (http://w3.gre.ac.uk/cost859) rassemble plus de 250 scientifiques. Depuis octobre 2004, il oeuvre à promouvoir et organiser en réseau la recherche dans le domaine des phytotechnologies. Structuré en quatre groupes de travail (WG) interconnectés, ses activités sont axées sur les plantes et microorganismes associés pour (i) comprendre, contrôler et utiliser des mécanismes impliqués dans l'absorption, la translocation, le métabolisme et le stockage des polluants (éléments traces non essentiels ou en excès, composés organiques) et des éléments nutritifs essentiels, (ii) réduire le transfert des polluants vers les plantes utilisées en alimentation et améliorer leurs qualités et valeur nutritive (WG3), en utilisant les connaissances et outils de la Physiologie et Biologie végétale (tous WG), Biochimie, Biogéochimie et Microbiologie (WG1) et Biologie moléculaire (WG2) . Enfin, le dernier groupe de travail " Application et Intégration des Phytotechnogies " (WG4) a pour mission de proposer des solutions appropriées pour assainir, réhabiliter et gérer durablement les sols et les ressources en eaux, avec une évaluation des conséquences écologiques, socio-économiques (dont la valorisation des milieux et de la biomasse récoltée) et réglementaires. Ces solutions doivent pouvoir prouver leur efficacité, présenter des avantages par rapport aux autres solutions disponibles, respecter l'environnement et être économiquement viables. Sur la base des travaux réalisés par les scientifiques du WG4 sur des sites pilotes où sont expérimentés la phytoextraction, la phytostabilisation, la rhizodégradation, la rhizofiltration et le lagunage artificiel et restitués lors des réunions du groupe de travail, l'état d'avancement de l'application des phytotechnologies au niveau mondial sera présenté ainsi que les besoins de recherche associés

Regulation of aerobic granular sludge reformulation after granular sludge broken: Effect of poly aluminum chloride (PAC)

The present study focuses on the effect of poly aluminum chloride (PAC) on the re-formation of aerobic granular sludge after its rupture. The morphological changes, physical characteristics such as SVI, mechanical strength and surface properties of aerobic granular sludge during the re-formation process of broken granules were investigated. Moreover, components (protein (PN), polysaccharides (PS)) and distributions (soluble, loosely-bound (LB), tightly-bound (TB)) of extracellular polymeric substances (EPS) in sludge flocs were taken into consideration. It was found that the effect of charge neutralization and bridging induced by PAC treatment improved the surface properties of sludge, the re-formed granules had a larger size, more compact structure and that the removal performance of pollutants after chemical coagulation had improved. The results of correlation analysis demonstrated that PN in EPS correlated well with the surface characteristics and settling ability of sludge flocs, and PAC treatment strengthened the influence, further accelerated the reformation of granular sludge.</p

Poly aluminum chloride (PAC) enhanced formation of aerobic granules:Coupling process between physicochemical–biochemical effects

Transforming conventional flocculent sludge to aerobic granular sludge is drawing increasing global interest in a quest for an efficient and innovative technology in wastewater treatment. However, long start-up time and low granule stability are the main challenging issues for its application. In this study, long-term and short-term PAC feeding strategies were applied in parallel to enhance the sludge granulation and with the aim to figure out the temporal effect of PAC during the whole process. Nevertheless, both of them identified to allow a rapid start-up formation of aerobic granules with better performances in physicochemical characteristics. More extracellular polymeric substances (EPS) were secreted in all PAC-fed reactors, especially for polysaccharides. By using enzymatic hydrolysis, factors which account for the flocculating ability and stability of granules were identified. Notably, the correlation between them was also revealed. Based on these findings, dosage of PAC played a positive role mainly during the start-up period (first 15&nbsp;days) of the aerobic granules formation, extending its dosing time made no significant sense. The granules formed under this condition were the result of physicochemical&ndash;biochemical effects coupling process.</p

Transformation of Chloroform in Model Treatment Wetlands: From Mass Balance to Microbial Analysis

Chloroform is one of the common disinfection byproducts, which is not susceptible to degradation and poses great health concern. In this study, the chloroform removal efficiencies and contributions of sorption, microbial degradation, plant uptake, and volatilization were evaluated in six model constructed wetlands (CWs). The highest chloroform removal efficiency was achieved in litter-added CWs (99%), followed by planted (46–54%) and unplanted CWs (39%). Mass balance study revealed that sorption (73.5–81.2%) and microbial degradation (17.6–26.2%) were the main chloroform removal processes in litter-added CWs, and that sorption (53.6–66.1%) and plant uptake (25.3–36.2%) were the primary contributors to chloroform removal in planted CWs. Around 60% of chloroform got accumulated in the roots after plant uptake, and both transpiration and gas-phase transport were expected to be the drivers for the plant uptake. Sulfate-reducing bacteria and methanogens were found to be the key microorganisms for chloroform biodegradation through cometabolic dechlorination, and positive correlations were observed between functional genes (dsrA, mcrA) and biodegradation rates. Overall, this study suggests that wetland is an efficient ecosystem for sustainable chloroform removal, and that plant and litter can enhance the removal performance through root uptake and microbial degradation stimulation, respectively