1,720,977 research outputs found
Implementing a composite indicator approach for prioritizing activated sludge-based wastewater treatment plants at large spatial scale
No full textSuccessful implementation of the European Urban Wastewater Treatment Directive requires a deepened and multidisciplinary knowledge of the wastewater systems. The development of ready-to-use tools for decision makers is, in this sense, a challenge. This paper proposes a methodology to efficiently prioritize wastewater treatment plants (WWTPs) on the basis of the relative environmental, social and public health impacts, taking into account the territorial context issues. The proposed methodology has led to the implementation of a composite indicator. The several choices made for its development, from the definition of framework to the final outcomes, have been evaluated in depth and are supported through methodological and statistical techniques. The potential use of the composite indicator with the inherent advantages and limitations are discussed in order to provide a ready-to-use tool for final users for WWTPs prioritization. Moreover, a concise methodology for composite index implementation is described. © 2016 Elsevier Lt
Online monitoring of MBR fouling by transmembrane pressure and permeability over a long-term experiment
No full textSeveral methods have been proposed over the last decade for the monitoring of fouling processes in membrane bioreactors (MBRs). Many of these methods aim to acquire information measuring the transmembrane pressure (TMP) and permeability (K) directly on the membrane modules used in wastewater treatment plants. This study assessed in a critical light the use of TMP and K for membrane fouling monitoring. TMP and K were directly measured on a pilot-scale submerged MBR operated continuously for approximately 450 d at different solids retention times and fed with real municipal wastewater. The results showed that under standard operating conditions such as those usually applied in full-scale MBR and with the monitoring instruments typically employed in industrial applications, the identification of specific TMP trends within a filtration phase was often problematic and the results were unreliable, mainly because of the noise and the variability of real wastewater and environmental conditions. Moreover, a non-linear trend of the pressure behaviour within a filtration phase was observed when fouling phenomena were taking place. This study also proposes the use of the ratio between filtration and backwash permeability in order to assess whether the membrane flux is deviating from the "pressure controlled region" and, consequently, fouling processes are occurring. © 2013 Elsevier B.V. All rights reserved
Effect of solid retention time on sludge filterability and biomass activity: Long-term experiment on a pilot-scale membrane bioreactor treating municipal wastewater
No full textA membrane bioreactor (MBR) pilot-plant fed by municipal wastewater, was continuously operated for 450d at different solid retention times (SRT: 25, 50 and 75d) with the aim of identifying possible relations between transmembrane pressure (TMP) evolution and a set of parameters describing physico-chemical sludge characteristics such as capillary suction time (CST), soluble microbial products (SMP), extracellular polymeric substances, critical flux (Jc), oxygen diffusion, biomass kinetic and stoichiometric coefficients (measured by respirometric techniques). Data analysis confirms that MBRs can operate with high SRT ensuring good treatment performances and, from the biological point of view, no effective loss of biodegradation activities. During the study changes in sludge filterability properties for the different operating conditions were observed. Among the different microbial products that characterise the colloidal materials of the mixed liquor, only the carbohydrate fraction of the SMP was correlated with CST and Jc and showed a clear dependence on SRTs. However, the same information can be obtained by a much simpler analysis such as the chemical oxygen demand (COD) fine fraction (defined as the difference between the mixed liquor soluble COD and the effluent COD). TMP trend showed the typical evolution proposed in the local flux theory. Jc and CST trends can be used to predict sludge filterability. Higher sludge fouling propensity was observed at operating conditions when the highest sludge activity was also observed, suggesting a direct relation between fouling and microbial metabolism. Moreover, the addition of the anoxic process seemed to deteriorate the sludge filterability. © 2013 Elsevier B.V
An integrated approach for monitoring efficiency and investments of activated sludge-based wastewater treatment plants at large spatial scale
No full textWISE, the Water Information System for Europe, is the web-portal of the European Commission (EU) that disseminates the quality state of the receiving water bodies and the efficiency of the municipal wastewater treatment plants (WWTPs) in order to monitor advances in the application of both the Water Framework Directive (WFD) as well as the Urban Wastewater Treatment Directive (UWWTD). With the intention to develop WISE applications, the aim of the work was to define and apply an integrated approach capable of monitoring the efficiency and investments of activated sludge-based WWTPs located in a large spatial area, providing the following outcomes useful to the decision-makers: (i) the identification of critical facilities and their critical processes by means of a Performance Assessment System (PAS), (ii) the choice of the most suitable upgrading actions, through a scenario analysis. (iii) the assessment of the investment costs to upgrade the critical WWTPs and (iv) the prioritization of the critical facilities by means of a multi-criteria approach which includes the stakeholders involvement, along with the integration of some technical, environmental, economic and health aspects. The implementation of the proposed approach to a high number of municipal WWTPs highlighted how the PAS developed was able to identify critical processes with a particular effectiveness in identifying the critical nutrient removal ones. In addition, a simplified approach that considers the cost related to a basic-configuration and those for the WWTP integration, allowed to link the critical processes identified and the investment costs. Finally, the questionnaire for the acquisition of data such as that provided by the Italian Institute of Statistics, the PAS defined and the database on the costs, if properly adapted, may allow for the extension of the integrated approach on an EU-scale by providing useful information to water utilities as well as institutions. © 2015 Elsevier B.V
Model-based analysis of the effect of different operating conditions on fouling mechanisms in a membrane bioreactor
No full textThis study proposes a model-based evaluation of the effect of different operating conditions with and without pre-denitrification treatment and applying three different solids retention times on the fouling mechanisms involved in membrane bioreactors (MBRs). A total of 11 fouling models obtained from literature were used to fit the transmembrane pressure variations measured in a pilot-scale MBR treating real wastewater for more than 1 year. The results showed that all the models represent reasonable descriptions of the fouling processes in the MBR tested. The model-based analysis confirmed that membrane fouling started by pore blocking (complete blocking model) and by a reduction of the pore diameter (standard blocking) while cake filtration became the dominant fouling mechanism over long-term operation. However, the different fouling mechanisms occurred almost simultaneously making it rather difficult to identify each one. The membrane “history” (i.e. age, lifespan, etc.) seems the most important factor affecting the fouling mechanism more than the applied operating conditions. Nonlinear regression of the most complex models (combined models) evaluated in this study sometimes demonstrated unreliable parameter estimates suggesting that the four basic fouling models (complete, standard, intermediate blocking and cake filtration) contain enough details to represent a reasonable description of the main fouling processes occurring in MBRs. © 2015, Springer-Verlag Berlin Heidelberg
Combined statistical techniques for the water quality analysis of a natural wetland and evaluation of the potential implementation of a FWS for the area restoration: the Torre Flavia case study, Italy
No full textThe paper focussed on the analysis of the environmental status of a natural wetland and the assessment of potential solutions to preserve the area, the related ecosystem services and natural equilibria. Data on water quality parameters and on climatic conditions were derived from a yearly monitoring campaign and web sources respectively. Chemometric techniques and a water quality index (WQI) were applied in order to assemble the obtained information and define an exhaustive overview of the wetland status. Data processing allowed to estimate the system water balance and to evaluate spatial and temporal variations of water quality. A water deficit as well as a major wetland sensitivity respect to pollution loads was verified during the warmer season (June-September). Local criticalities and environmental pressure were assessed and possible solutions to properly manage and restore the natural system were evaluated. The use of the wetland as a free water system (FWS) receiving treated wastewater from a local UWWTP was considered in the view of using local resources and restoring the water balance, avoiding environmental impacts and excessive management costs. Wetland auto-depurative capacity was assessed through common empirical plug flow models which revealed the ammonia nitrogen loads during the winter season as the limiting conditions. By deriving the maximum capacity of the system to receive pollutants, the study showed how water balance restorations as well as environmental and economic savings are achievable. Additional benefits have to be associated to ecosystem services and the possibility for recreational, cultural and educational activities. © 2017 Elsevier Lt
Assessing the public perception of islanders regarding the implementation of new technologies to optimize the municipal solid waste management system: A Mediterranean case study
No full textOne of the most important contemporary challenges for small islands is to make more sustainable human activities as the management of municipal solid waste (MSW). The recent EGADI project involved the realization of two pilot project actions in a small Mediterranean island of Southern Italy (Island of Favignana) with the goal to adapt the current MSW management system to the logic of the 3Rs approach (reduce, reuse & recycle). The actions concerned the installation of a water kiosk to reduce plastic waste production and a community composter to recover material from the organic fraction of MSW. Additionally, non-structural actions as a communication plan and an environmental education campaign were implemented with the intent of increasing public awareness on the addressed topics. In this context, the study was aimed to investigate the public perception and knowledge of islanders with reference to the two pilot actions before and after the implementation of such activities so as to provide guidance for optimizing the MSW management system of the island. A structured questionnaire was implemented and administered to the students of a secondary school and their parents before and after the implementation of the planned actions. The obtained data were processed by using descriptive statistics and Multiple Correspondent Analysis (MCA) in order to achieve a global view on the level of knowledge and public perception as well as to establish as a whole, the rate of satisfaction and the goodness of the project actions. The feedbacks on the implemented actions were critically discussed highlighting both positive and negative aspects. Some drawbacks were to be connected to the adopted communicative plan which resulted to be not so effective in reaching the target since its random character. Islanders perceived positively the new technologies implemented. The water kiosk was perceived positively if it only serves residents. Furthermore, islanders positively perceived the kerbside separate collection preferring at the same time the community composting as strategy for the management of the organic fraction, at least in the most densely populated areas. The social assessment that was conducted during the investigation provided guidance of the optimum MSW management system of the island. © 2017 Elsevier Ltd. All rights reserved
Energy saving in wastewater treatment plants: A methodology based on common key performance indicators for the evaluation of plant energy performance, classification and benchmarking
No full textWastewater treatment plants are a major energy user in the urban water cycle with an energy demand estimated in several countries in about the 1% of the overall national energy use. Nevertheless, the sector offers wide opportunities for energy saving and recovery to be fostered in order to reduce economic and environmental impacts. Nowadays, a consolidated procedure to assess energy performances in the wastewater sector is still not available. This work proposes a methodology for the evaluation, benchmarking and labelling of energy performances of wastewater treatment plants, based on easy-to-define data related to energy use and operative parameters. Statistical techniques are applied to validate input data and the step-by-step derived outcomes. Common key performance indicators were calculated and linearly aggregated in a global index able to convey the wastewater treatment plant energy performance. Such index allowed to carry out comparisons among energy consumptions supported by a dedicated built-up database collecting sectorial data, considered as a reference. A case study based on 10 selected wastewater treatment plants is proposed. The methodology led to derive a clear and affordable overview of the analysed plant energy performances. Moreover, the benchmarking analysis allowed to get, on the basis of the differences between the calculated global index values, a rough estimation of the potential energy gains achievable if suitable measures for ameliorating the plant energy efficiency performance are adopted. For three of the selected plants, the margins for energy savings resulted higher than 60%. The methodology suggests to focus on such cases by carrying out specific on-site inspection to detect energy use inefficiencies and define suitable actions addressed to save energy and enhance the system sustainability. In this view, the proposed procedure could also be applied with the aim of prioritizing actions to pursue energy savings among a large set of wastewater treatment plants
Assessment of performance and advantages related to the use of a natural coagulant in the industrial wastewater treatment
No full textThe paper deals with the demonstration of the technical and environmental advantages related to the use of a tannin based coagulant in textile wastewater treatments. The natural coagulant was tested to evaluate its performance in the coagulation/flocculation process, the level of biodegradability in both aerobic and anaerobic conditions and the eco-toxicological risks for aquatic systems. Results were compared with a common inorganic metal based coagulant. The findings at lab scale showed that the natural coagulant is more efficient than the inorganic allowing to achieve same performance with a dosage 36% lower. Moreover, the natural coagulant gave the formed floes a high degree of dewaterability implying less excess sludge volume to be disposed after treatment. Additionally, the natural coagulant showed no toxic effects for the aquatic environment and the sludge biomass activity as well as high degree of biodegradability in both aerobic and anaerobic conditions. The efficiency ofthe natural coagulant on textile wastewater was further validated at pilot scale where, in optimized conditions, economic savings were achieved, reaching a specific treatment cost of0.18€/m3 of raw wastewater. © 2017, Gh. Asachi Technical University of Iasi. All rights reserved
Methodology for a preliminary assessment of water use sustainability in industries at sub-basin level
Full text linkThe sustainability of industrial production, especially for highly water-demanding processes, is strictly related to water resource availability and to the dynamic interactions between natural and anthropogenic requirements over the spatial and temporal scales. The increase in industrial water demand raises the need to assess the related environmental sustainability, facing the occurrence of global and local water stress issues. The identification of reliable methodologies, based on simple indices and able to consider the impact on local water basins, may play a basilar role in water sustainability diagnosis and decision-making processes for water management and land use planning. The present work focalized on the definition of a methodology based on the calculation of indicators and indices in the view of providing a synthetic, simple, and site-specific assessment tool for industrial water cycle sustainability. The methodology was built starting from geo-referenced data on water availability and sectorial uses derived for Italian sub-basins. According to the data monthly time scale, the proposed indices allowed for an industrial water-related impacts assessment, able to take into account the seasonal variability of local resources. Three industrial factories, located in northern (SB1, SB2) and central (SB3) Italian sub-basins, were selected as case studies (CS1, CS2, CS3) to validate the methodology. The companies were directly involved and asked to provide some input data. The methodology is based on the calculation of three synthetic indexes: the Withdrawal and Consumption water Stress Index (WCSI) allowed for deriving a synthetic water stress level assessment at the sub-basin scale, also considering the spatial and temporal variations; the industrial water use sustainability assessment was achieved by calculating the Overall Factory-to-Basin Impact (OFBI) and the Internal Water Reuse (IWR) indices, which allowed a preliminary evaluation of the factories' impacts on the sub-basin water status, considering the related water uses and the overall pressures on the reference territorial context. The WCSI values highlighted significant differences between the northern sub-basins, characterised by limited water stress (WCSISB1 = 0.221; WCSISB2 = 0.047), and the central ones, more subjected to high stress (WCSISB3 = 0.413). The case studies CS1 and CS3 showed to exert a more significant impact on the local water resource (OFBICS1 = 0.18%; OFBICS2 = 0.192%) with respect to CS2 (OFBI = 0.002%), whereas the IWR index revealed the different company's attitude in implementing water reuse practices (IWRCS1 = 40%; IWRCS1 = 27%; IWRCS1 = 99%). The proposed methodology and the indices may also contribute to assessing the effectiveness of river basin management actions to pursue sustainable development goals
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