1,721,286 research outputs found
A comprehensive comparison between two strategies to produce polyhydroxyalkanoates from domestic sewage sludge
Full text linkBiopolimer materials, such as polyhydroxyalkanoates (PHA), are essential to restrain the use of petroleum-based plastic material fostered by European Union regulation. Despite the recent development regarding the production of PHA, the scale-up of sewage sludge-based technology is still in its infancy since the literature lacks studies on the environmental impact of the process. This work aims to stand as a pioneer study reporting the direct greenhouse gas (GHG) emissions and carbon footprint (CF) of two sewage sludge-based PHA production strategies. The two strategies, aerobic dynamic feeding (ADF) and aerobic/anoxic enrichment (AE/AN), were monitored and compared based on the system 's efficiency in removing carbon and nutrients, PHA 's production and productivity, nitrous oxide direct emissions and the CF. The produced PHA accounted for 38.21 g PHA g-1 volatile suspended solids (VSS) % and 14.54 g PHA g-1 VSS %, for ADF and AE/AN, respectively. The N 2 O emissions were lower for ADF than the AE/AN enrichment, 0.39 N 2 O -N L-1 and 0.98 N 2 O -N L-1 , respectively, as was the CF, which accounted for 3.56 kg CO 2 day- 1 and 6.91 kg CO 2 day- 1 for ADF and AE/AN respectively. This innovative study provides valuable insights into comparing the two above-mentioned strategies and a pilot for structuring and designing future studies comprehensively considering the environmental consequences of the process in future life cycle assessments
Uncertainty Propagation In Integrated Urban Water Quality Modelling
No full textSensitivity and uncertainty assessment of integrated urban drainage water quality
models are crucial steps in the evaluation of the reliability of model results. Indeed, the
assessment of the reliability of the results of complex water quality models is crucial in
understanding their significance. In the case of integrated urban drainage water quality
models, due to the fact that integrated approaches are basically a cascade of sub-models
(simulating the sewer system, wastewater treatment plant and receiving water body),
uncertainty produced in one sub-model propagates to the following ones in a manner
dependent on the model structure, the estimation of parameters and the availability and
uncertainty of measurements in the different parts of the system. Uncertainty basically
propagates throughout a chain of models in which the simulation output from upstream
models is transferred to the downstream ones as input. The paper presents the uncertainty
assessment of an integrated urban drainage model developed in previous studies by means
of the Generalized Likelihood Uncertainty Estimation (GLUE) methodology. A
straightforward approach based on the analysis of the coefficient of variation (Rxy). Rxy is
defined as the ratio between the standard deviation (α) and the average (μ) value of the
model output of reference taken into account. The analysis has been applied to an
experimental catchment in Bologna (Italy) which consists of a part of the Bologna sewer
network and a reach of the Savena river. The results showed that the method can be a useful
tool for uncertainty analysis and for guiding the operator in the choice of the modelling
approach
Frontiers International Conference on Wastewater Treatment
Full text linkThis book describes the latest research advances, innovations, and applications in the field of water management and environmental engineering as presented by leading researchers, engineers, life scientists and practitioners from around the world at the Frontiers International Conference on Wastewater Treatment (FICWTM), held in Palermo, Italy in May 2017. The topics covered are highly diverse and include the physical processes of mixing and dispersion, biological developments and mathematical modeling, such as computational fluid dynamics in wastewater, MBBR and hybrid systems, membrane bioreactors, anaerobic digestion, reduction of greenhouse gases from wastewater treatment plants, and energy optimization. The contributions amply demonstrate that the application of cost-effective technologies for waste treatment and control is urgently needed so as to implement appropriate regulatory measures that ensure pollution prevention and remediation, safeguard public health, and preserve the environment. The contributions were selected by means of a rigorous peer-review process and highlight many exciting ideas that will spur novel research directions and foster multidisciplinary collaboration among different water specialists.
Numerical and CFD-Based Modelling of Concentrated Domestic Slurry in Turbulent Flow Through Circular Pipes
No full textThe concentration of domestic slurry has two advantages, it promotes resource recovery (nutrients and biomass) and saves water. But the design of a relevant sewerage requires a clear understanding of the frictional losses incurred during the transport of the slurry. This abstracts describes numerical & CFD-based methods to estimate losses while the concentrated slurry flows through circular pipes in a fully-turbulent flow. To model turbulent flows through circular pipes, one can rely on either the Newtonian Moody Charts appropriate for engineering applications or a computational fluid dynamics (CFD)-based analysis, made possible through the Newtonian universal law of the wall. However, our studies reveal that concentrated domestic slurry behaves like a non-Newtonian fluid, of the Herschel-Bulkley type. Therefore, the analysis of such a slurry would require modifications to both, existing engineering models and CFD methods. This abstract summarises a modified law of the wall suitable for Herschel-Bulkley fluids, which has been validated against experiments on concentrated domestic slurry. It further details possible non-Newtonian numerical engineering models that could be modified to assess frictional losses incurred by Herschel-Bulkley fluids. The latter will be a quicker and perhaps reliable alternative to computationally expensive CFD-analyses.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Sanitary Engineerin
Influence of Flood Water Contribution from Multiple Sources in Extreme Event Statistics of Urban Flooding
Full text linkFor pluvial flood risk assessment in urban areas it is important to be able to calculate how often a specific area is at risk of flooding. This is especially evident in urban areas subject to contribution from multiple sources, e.g. surcharging drainage system, surface runoff, overflowing rivers, etc. In this study extreme event statistics are assessed by simulation of rainfall impact and consecutive statistics of flood response in order to estimate return periods of flooding. The model applied is an integrated hydraulic model which includes relevant hydrological processes that contribute to urban flooding. The setup is analysed based on a small urban catchment in Aalborg Denmark. Results show that it is possible to estimate return periods of flood volume, flood extent and local water levels based on simulation and that rainfall and hydrological conditions critical to flooding can be identified.Accepted Author ManuscriptAtmospheric Remote Sensin
Mathematical Modelling of Corleone (Italy) Full-Scale Wastewater Treatment Plant for Estimating the Greenhouse Gas Emissions: A Sensitivity Analysis
Full text linkThis study summarises the sensitivity analysis results using a novel mathematical model. The mathematical model already published represents the modification of the activated sludge model no. 1 (ASM1) in view of including the nitrous oxide (N2O) emission (namely ASM1 + N2O model). The ASM1 + N2O model was applied to a full-scale wastewater treatment plant in Corleone (Italy). Sensitivity analysis was performed by applying a local approach. In view of comparing results obtained for the model outputs taken into account (mixed liquor suspended solids - MLSS, effluent total COD, and effluent NH4-N - SNH concentrations) a normalised sensitivity index (SI) was assessed. Calculated normalised SI for model outputs highlight specific influential parameters, notably YH, fp, μH, bH, and those related to ammonia-oxidizing bacteria (AOBs). For the MLSS model output, only two model parameters were found influential, but 8 significant model parameters (4 for each) were identified for effluent total COD and SNH concentrations. This study provides insights for a more efficient calibration process, laying the groundwork for future research on the ASM1 + N2O mode
Mathematical modelling of greenhouse gas emissions from membrane bioreactors: A comprehensive comparison of two mathematical models
Full text linkThis paper compares two mathematical models (Model I and Model II) to predict greenhouse gases emission from a University Cape Town (UCT) – membrane bioreactor (MBR) plant. Model I considers N2O production only during denitrification. Model II takes into account the ammonia-oxidizing bacteria (AOB) formation pathways for N2O. Both models were calibrated adopting real data. Model comparison was performed in terms of (i) sensitivity analysis (ii) best fit and (iii) model prediction uncertainty. On average 6% of factors of Model I and 9% of Model II resulted to be important. In terms of best fit, Model II had a better capability of reproducing the measured data. The average efficiency related to the N2O model outputs was equal to 0.33 and 0.38 for Model I and Model II, respectively. On average, 73% (Model I) and 86% (Model II) of measured data lay inside the uncertainty bands
Membrane Bioreactors for wastewater reuse: Respirometric assessment of biomass activity during a two year survey
No full textStricter effluent limits, water shortage conditions, land availability requires today even more the needs of advanced wastewater treatments. Attractive solutions come from membrane bioreactors (MBR), Integrated Fixed Film Activated Sludge (IFAS) or combinations (i.e., IFAS-MBRs). One crucial aspect for the applicability of this overall new technology, compared to the conventional activated sludge systems, is the lack of knowledge for design and manage (e.g., kinetic constants, optimal operative conditions etc.). In view of the above frame, the aim of the present study was to assess the kinetic and stoichiometric parameters of bacterial species in MBRs by means of respirometric techniques. Plant configurations, operational conditions and wastewater features (domestic/industrial) were analysed. Four different MBR plants were investigated: i) sequencing batch MBR subjected to a gradual salinity increase; ii) pre-denitrification MBR treating saline wastewater contaminated by hydrocarbons; iii) University of Cape Town (UCT) MBR treating domestic wastewater subjected to a carbon-to-nitrogen (C/N) ratio variation; iiii) UCT- IFAS -MBR treating domestic wastewater. Results show a significant influence on biomass respiratory activity from both plant configurations and operational conditions. The salinity increase severely affected the activity of autotrophic species, while heterotrophic community was mainly influenced by the C/N variation. Moreover, it was observed a specialization in the IFAS-MBR configuration, with the suspended biomass more affine to organic matter, whilst biofilm in the nitrification process. The respirometric analysis confirmed to be an effective tool for the evaluation of the biomass kinetic and stoichiometric parameters. The results of this study can be useful for the application of mathematical models in the design phase and for the monitoring of biomass viability during plant operations
Sewage sludge acidogenic fermentation for organic resource recovery towards carbon neutrality: an experimental survey testing the headspace influence
Full text linkVolatile fatty acids (VFAs) produced by acidogenic digestion of sewage sludge are very interesting bio-products which can contribute to carbon neutrality of wastewater treatment plants. Studies on the production of VFAs from sewage sludge from fermenters with membrane are limited. In view of above, VFAs from a fermenter pilot plant equipped with a membrane bioreactor and fed with real sewage sludge has been monitored. The effect of headspace volume (HdV) on VFA production was studied for the first time to elucidate the optimal operation conditions. Specifically, three fermenter HdV values (namely, 20, 40 and 60% of the total volume) have been investigated. Results revealed that the HdV of 20% ensured the highest sCOD production (900 mgCOD/L) and VFA/COD ratio (45.4%). High value of HdV (namely, 40 and 60%) strongly decreased the acidogenic fermentation performance in terms of VFA production
Water Reuse and Risk Analysis: The Case Study of Corleone (Italy) Ultrafiltration Plant
No full textThis study summarises the results of two months of monitoring the full-scale ultrafiltration plant in Corleone (Italy). The monitoring has been conducted according to the current regulations on water reuse in Italy (Italian Ministerial Decree 185/2003 and 2020/741/EU). Samples were withdrawn every ten days from three sections: i. treated disinfected wastewater (Section 1); ii. Downstream the sand filtration (Section 2); iii. After the ultrafiltration (Section 3). Data showed the ultrafiltration plant’s excellent capability to remove E.coli, total suspended solids (TSS), and turbidity. For the parameters, the permeate quality can be classified as Class A according to 2020/741/EU. Conversely, in terms of BOD5, the permeate can be categorised as Class B according to 2020/741/EU since the BOB5 value was around 20 mgO2 L-1 on average. Therefore, treated water can be adopted for food crops, processed and non-food crops and all irrigation methods are allowed. The study also has the novelty of providing a first attempt at performing a risk analysis according to 2020/741/EU, which has yet to apply to Sicilian plants
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