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Muller B.,Eawag - Swiss Federal Institute of Aquatic Science and Technology | Bryant L.D.,Eawag - Swiss Federal Institute of Aquatic Science and Technology | Bryant L.D.,ETH Zurich | Matzinger A.,Kompetenzzentrum Wasser Berlin GGmbH | And 3 more authors.
Environmental Science and Technology | Year: 2012

The oxygen-consuming processes in the hypolimnia of freshwater lakes leading to deep-water anoxia are still not well understood, thereby constraining suitable management concepts. This study presents data obtained from 11 eutrophic lakes and suggests a model describing the consumption of dissolved oxygen (O2) in the hypolimnia of eutrophic lakes as a result of only two fundamental processes: O2 is consumed (i) by settled organic material at the sediment surface and (ii) by reduced substances diffusing from the sediment. Apart from a lakes productivity, its benthic O2 consumption depends on the O2 concentration in the water overlying the sediment and the molecular O2 diffusion to the sediment. On the basis of observational evidence of long-term monitoring data from 11 eutrophic lakes, we found that the areal hypolimnetic mineralization rate ranging from 0.47 to 1.31 g of O2 m-2 d-1 (average 0.90 ± 0.30) is a function of (i) a benthic flux of reduced substances (0.37 ± 0.12 g of O2 m-2 d-1) and (ii) an O2 consumption which linearly increases with the mean hypolimnion thickness (zH) up to ∼25 m. This model has important implications for predicting and interpreting the response of lakes and reservoirs to restoration measures. © 2012 American Chemical Society.


Schoumans O.F.,Wageningen University | Bouraoui F.,European Commission - Joint Research Center Ispra | Kabbe C.,Kompetenzzentrum Wasser Berlin gGmbH | Oenema O.,Wageningen University | van Dijk K.C.,Wageningen University
Ambio | Year: 2015

Food production in Europe is dependent on imported phosphorus (P) fertilizers, but P use is inefficient and losses to the environment high. Here, we discuss possible solutions by changes in P management. We argue that not only the use of P fertilizers and P additives in feed could be reduced by fine-tuning fertilization and feeding to actual nutrient requirements, but also P from waste has to be completely recovered and recycled in order to close the P balance of Europe regionally and become less dependent on the availability of P-rock reserves. Finally, climate-smart P management measures are needed, to reduce the expected deterioration of surface water quality resulting from climate-change-induced P loss. © 2015, The Author(s).


Remy C.,Kompetenzzentrum Wasser Berlin GGmbH | Jekel M.,TU Berlin
Water Science and Technology | Year: 2012

This study investigates the cumulative energy demand (CED) of different systems for the management of urban wastewater, following the methodology of Life Cycle Assessment. In a hypothetical case study for an urban area (5,000 inhabitants), all relevant processes for wastewater collection and treatment and the construction of infrastructure are described in a substance flow model. The conventional system requires 1,250 MJ/(pe*a), with the operation contributing 45%, the infrastructure 7%, and the system expansion (production of mineral fertilizer and electricity) 48% to the total CED. The separation systems have a CED of 930-1,182 MJ/(pe*a) depending on their configuration. Results of the impact assessment show that recovering energy from the organic matter of toilet wastewater and household biowaste in a digestion process can decrease the cumulative energy demand by 13-26%. Energetic benefits of mineral fertilizer substitution are relatively small compared to the energy recovered from organic matter. Decisive parameters for the energy analysis are the amount of biowaste which is co-digested with toilet wastewater and the energy demand of the vacuum plant. © IWA Publishing 2012.


Groeschke M.,Kompetenzzentrum Wasser Berlin gGmbH | Groeschke M.,Free University of Berlin | Kumar P.,Indian Institute of Technology Roorkee | Winkler A.,Free University of Berlin | And 2 more authors.
Environmental Earth Sciences | Year: 2016

At a riverbank filtration (RBF) site in central Delhi unusually high and strongly fluctuating ammonium (NH4 +) concentrations were measured in the groundwater. Sewage contaminated river water has been identified as the main source of the NH4 + plume. However, the well field is located within an irrigated agricultural area and irrigation return flow might have an additional impact on the groundwater contamination. To quantify the role of irrigation return flow, sediments of the vadose zone were characterized concerning their hydraulic and sorption characteristics, and x-ray diffraction for clay mineral analyses and laboratory column studies were conducted with representative sediments. The sediments range between silt and fine-medium sand with calculated hydraulic conductivities between 2.1 × 10−4 and 1.0 × 10−7 m/s and a cation exchange capacity between 0.9 and 37.2 meq/100 g sediment. The column experiments show that NH4 + retardation through cation exchange is the main process occurring in the sediments. Contrary to the results of similar experiments conducted with sediments from the saturated zone, mass balances reveal that NH4 + fixation or degradation also takes place in significant amounts and up to 0.09 meq NH4 +/100 g sediment were transformed this way. This indicates that irrigation return flow can be neglected as a major source of NH4 + at the field site. Instead the NH4 + fixation or degradation in the unsaturated zone might be one reason for the observed variations of NH4 + concentrations in the groundwater. © 2015, Springer-Verlag Berlin Heidelberg.


Remy C.,Kompetenzzentrum Wasser Berlin GGmbH | Lesjean B.,Kompetenzzentrum Wasser Berlin GGmbH | Waschnewski J.,Berliner Wasserbetriebe
Water Science and Technology | Year: 2013

This study exemplifies the use of Life Cycle Assessment (LCA) as a tool to quantify the environmental impacts of processes for wastewater treatment. In a case study, the sludge treatment line of a large wastewater treatment plant (WWTP) is analysed in terms of cumulative energy demand and the emission of greenhouse gases (carbon footprint). Sludge treatment consists of anaerobic digestion, dewatering, drying, and disposal of stabilized sludge in mono- or co-incineration in power plants or cement kilns. All relevant forms of energy demand (electricity, heat, chemicals, fossil fuels, transport) and greenhouse gas emissions (fossil CO2, CH4, N2O) are accounted in the assessment, including the treatment of return liquor from dewatering in the WWTP. Results show that the existing process is positive in energy balance (-162 MJ/PECOD *a) and carbon footprint (-11.6 kg CO2-eq/PECOD * a) by supplying secondary products such as electricity from biogas production or mono-incineration and substituting fossil fuels in co-incineration. However, disposal routes for stabilized sludge differ considerably in their energy and greenhouse gas profiles. In total, LCA proves to be a suitable tool to support future investment decisions with information of environmental relevance on the impact of wastewater treatment, but also urban water systems in general. © 2013 IWA Publishing.


Caradot N.,Kompetenzzentrum Wasser Berlin gGmbH | Sonnenberg H.,Kompetenzzentrum Wasser Berlin gGmbH | Riechel M.,Kompetenzzentrum Wasser Berlin gGmbH | Matzinger A.,Kompetenzzentrum Wasser Berlin gGmbH | Rouault P.,Kompetenzzentrum Wasser Berlin gGmbH
Water Practice and Technology | Year: 2013

The presented work studies the influence of the sampling strategy on the quality of locally calibrated UV-VIS probe measurements in combined sewer overflows (CSO) and the receiving river. Results indicate that UV-VIS spectrometers are not able to provide reliable measurements of water quality in urban stormwater without being calibrated to local conditions with laboratory analyses of water samples. The use of the global calibration (supplied by the manufacturer) led to errors of at least 30 and 45% for CSO load and river concentration of chemical oxygen demand (COD), respectively. Even with reliable local calibration, COD loads contained significant uncertainties close to 20%. Uncertainties in COD load and concentration decrease below 30% if more than 15-20 samples (i.e. 3 and 4 stormwater events) are sampled for local calibration. The effort and associated sampling costs to gain more than 15-20 samples are much less effective, since load and concentration uncertainties remain relatively stable with an increasing number of samples used for the calibration. The presented analysis aims at supporting practitioners in the planning, operation and calibration of UV-VIS spectrometer probes. © IWA Publishing 2013.


Sandoval S.,Pontifical Xavierian University | Torres A.,Pontifical Xavierian University | Pawlowsky-Reusing E.,Berliner Wasserbetriebe | Riechel M.,Kompetenzzentrum Wasser Berlin gGmbH | Caradot N.,Kompetenzzentrum Wasser Berlin gGmbH
Water Science and Technology | Year: 2013

The present study aims to explore the relationship between rainfall variables and water quality/quantity characteristics of combined sewer overflows (CSOs), by the use of multivariate statistical methods and online measurements at a principal CSO outlet in Berlin (Germany). Canonical correlation results showed that the maximum and average rainfall intensities are the most influential variables to describe CSO water quantity and pollutant loads whereas the duration of the rainfall event and the rain depth seem to be the most influential variables to describe CSO pollutant concentrations. The analysis of partial least squares (PLS) regression models confirms the findings of the canonical correlation and highlights three main in fluences of rainfall on CSO characteristics: (i) CSO water quantity characteristics are mainly influenced by the maximal rainfall intensities, (ii) CSO pollutant concentrations were found to be mostly associated with duration of the rainfall and (iii) pollutant loads seemed to be principally influenced by dry weather duration before the rainfall event. The prediction quality of PLS models is rather low (R2 < 0.6) but results can be useful to explore qualitatively the influence of rainfall on CSO characteristics. © IWA Publishing 2013.


Lepot M.,INSA Lyon | Torres A.,Pontifical Xavierian University | Hofer T.,University of Graz | Caradot N.,Kompetenzzentrum Wasser Berlin gGmbH | And 3 more authors.
Water Research | Year: 2016

UV/Vis spectrophotometers have been used for one decade to monitor water quality in various locations: sewers, rivers, wastewater treatment plants (WWTPs), tap water networks, etc. Resulting equivalent concentrations of interest can be estimated by three ways: i) by manufacturer global calibration; ii) by local calibration based on the provided global calibration and grab sampling; iii) by advanced calibration looking for relations between UV/Vis spectra and corresponding concentrations from grab sampling. However, no study has compared the applied methods so far. This collaborative work presents a comparison between five different methods. A Linear Regression (LR), Support Vector Machine (SVM), EVOlutionary algorithm method (EVO) and Partial Least Squares (PLS) have been applied on various data sets (sewers, rivers, WWTPs under dry, wet and all weather conditions) and for three water quality parameters: TSS, COD total and dissolved. Two criteria (r2 and Root Mean Square Error RMSE) have been calculated - on calibration and verification data subsets - to evaluate accuracy and robustness of the applied methods. Values of criteria have then been statistically analysed for all and separated data sets. Non-consistent outcomes come through this study. According to the Kruskal-Wallis test and RMSEs, PLS and SVM seem to be the best methods. According to uncertainties in laboratory analysis and ranking of methods, LR and EVO appear more robust and sustainable for concentration estimations. Conclusions are mostly independent of water matrices, weather conditions or concentrations investigated. © 2016 Elsevier Ltd.


PubMed | University of Graz, INSA Lyon, Pontifical Xavierian University and Kompetenzzentrum Wasser Berlin gGmbH
Type: | Journal: Water research | Year: 2016

UV/Vis spectrophotometers have been used for one decade to monitor water quality in various locations: sewers, rivers, wastewater treatment plants (WWTPs), tap water networks, etc. Resulting equivalent concentrations of interest can be estimated by three ways: i) by manufacturer global calibration; ii) by local calibration based on the provided global calibration and grab sampling; iii) by advanced calibration looking for relations between UV/Vis spectra and corresponding concentrations from grab sampling. However, no study has compared the applied methods so far. This collaborative work presents a comparison between five different methods. A Linear Regression (LR), Support Vector Machine (SVM), EVOlutionary algorithm method (EVO) and Partial Least Squares (PLS) have been applied on various data sets (sewers, rivers, WWTPs under dry, wet and all weather conditions) and for three water quality parameters: TSS, COD total and dissolved. Two criteria (r(2) and Root Mean Square Error RMSE) have been calculated - on calibration and verification data subsets - to evaluate accuracy and robustness of the applied methods. Values of criteria have then been statistically analysed for all and separated data sets. Non-consistent outcomes come through this study. According to the Kruskal-Wallis test and RMSEs, PLS and SVM seem to be the best methods. According to uncertainties in laboratory analysis and ranking of methods, LR and EVO appear more robust and sustainable for concentration estimations. Conclusions are mostly independent of water matrices, weather conditions or concentrations investigated.


PubMed | Berliner Wasserbetriebe, Pontifical Xavierian University and Kompetenzzentrum Wasser Berlin gGmbH
Type: Journal Article | Journal: Water science and technology : a journal of the International Association on Water Pollution Research | Year: 2013

The present study aims to explore the relationship between rainfall variables and water quality/quantity characteristics of combined sewer overflows (CSOs), by the use of multivariate statistical methods and online measurements at a principal CSO outlet in Berlin (Germany). Canonical correlation results showed that the maximum and average rainfall intensities are the most influential variables to describe CSO water quantity and pollutant loads whereas the duration of the rainfall event and the rain depth seem to be the most influential variables to describe CSO pollutant concentrations. The analysis of partial least squares (PLS) regression models confirms the findings of the canonical correlation and highlights three main influences of rainfall on CSO characteristics: (i) CSO water quantity characteristics are mainly influenced by the maximal rainfall intensities, (ii) CSO pollutant concentrations were found to be mostly associated with duration of the rainfall and (iii) pollutant loads seemed to be principally influenced by dry weather duration before the rainfall event. The prediction quality of PLS models is rather low (R < 0.6) but results can be useful to explore qualitatively the influence of rainfall on CSO characteristics.

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