26 research outputs found
Disinfection by peracetic acid: influence of inorganic and organic compounds
No full textThe disinfection effectiveness of peracetic acid (PAA) for wastewater applications has been extensively documented; however, PAA decays rapidly in water solution, depending on the water matrix characteristics. Guarantying a proper disinfectant dose is fundamental for the design of a disinfection process, therefore modeling PAA decay as a function of wastewater characteristics is crucial. The aim of this study was to assess PAA consumption in multi-component solutions reflecting realistic situations of a final effluent of a wastewater treatment plant (WWTP) under controlled conditions. Two experimental plans, one for inorganics and another one for organics, were defined using the statistical method of Design of Experiments (DoE), which allowed evaluating the effect of each compound or their interaction on PAA decay. Experiments were performed at laboratory-scale for PAA concentrations between 2-10 mgPAA/L and linear least-square regressions were used to interpolate two models based on the compounds that displayed an effect on PAA decay
A statistical assessment of persistent micropollutants occurrence, fate and health risk using censored water quality data
No full textIn the recent years, the presence of micropollutants in drinking water has become an issue of growing global concern. Great attention is paid to persistent toxic micropollutants that belong to several families (e.g. pesticides, perfluorinated compounds, pharmaceuticals, endocrine disrupting compounds) and are present at trace concentrations (ranging from ng/l to μg/l) in aquatic environments [1]. Due to their low concentration, monitoring databases are usually rich in censored data (e.g. samples with concentrations reported below the limit of quantification (LOQ)) that are typically eliminated or replaced with a value between 0 and LOQ [2]. These traditional methods present some limitations and can lead to erroneous conclusions on the presence of persistent micropollutants in the source water, treatment efficiencies, quality of the produced water and associated human health risk. Alternative methods, based on the principles of survival analysis, allow to estimate the statistical distribution of the whole dataset, combining the values above the LOQ with the information contained in the proportion of censored data [3]. The methods applied in this work are Maximum Likelihood Estimation or non-parametric techniques (e.g. Kaplan-Meier). Monitoring data of 5,362 groundwater (GW) and 12,344 drinking water samples collected from 2012 to 2017 in the city of Milan, Italy were analysed. Several persistent micropollutants, including pesticides and perfluorinated compounds, were selected for this study. This study demonstrated the benefits of the innovative methods in the assessment of data statistical distribution, highlighting the more accurate estimation of the distribution median, 95° and 98° quantiles, especially for high percentages of censored data. The resulting statistical distributions were used for several applications: time trend evaluation in GW micropollutant concentrations, optimization of well management, treatment efficiency evaluation. Moreover, they have been applied to assess the residual health risk associated with low concentration micropollutants and the risk reduction resulting by treatment and/or management intervention in the drinking water treatment plants. This study highlighted high discrepancy in the results obtained with traditional and innovative techniques related to the evaluation of the presence, fate and health risk associated to persistent and toxic micropollutants
Predicting long-term pharmaceutical concentrations during sewer overflows using a census data driven model
Get PDFA new modelling framework, which combines census and georeferenced data with a mechanistic storm water model, was developed to predict concentration dynamics of pharmaceuticals (PhACs) during overflow events. The model was verified with measurements and used to perform a long-term (1 year) risk assessment in a small urban catchment in Switzerland. Results show that census and georeferenced data are useful information that can be used as new type of model inputs to correctly predict PhACs concentration during combined sewer overflow (CSO) events
Modelling the fate of micropollutants in the water cycle at urban and peri-urban scale – An integrated perspective towards the impacts of water reuse
Get PDFAn integrated model was developed, calibrated and validated to predict the fate of micropollutants (MPs) and the human health risks that these substances pose when wastewater is reused for agricultural purposes. Results showed that pharmaceuticals (e.g., the anti-inflammatory drug paracetamol) can form during in-sewer transit from other metabolites and posing a potential risk (Hazard Quotient for infants = 10-2) if wastewater is not treated before irrigation. The model can represent a relevant decision-support tool to plan barriers for reducing the risk associated to MP
A statistical assessment of micropollutants occurrence, time trend, fate and human health risk using left-censored water quality data
Get PDFIn recent years, the presence of micropollutants in drinking water has become an issue of growing global concern. Due to their low concentrations, monitoring databases are usually rich in censored data (e.g. samples with concentrations reported below the limit of quantification, LOQ) which are typically eliminated or replaced with a value arbitrarily chosen between 0 and LOQ. These conventional methods have some limitations and can lead to erroneous conclusions on: presence of micropollutants in the source water, treatment efficiencies, produced water quality and associated human health risk. In this work, an advanced approach, based on Maximum Likelihood Estimation method for left-censored data (MLELC), was applied on monitoring data of 19 contaminants (metals, volatile organic compounds, pesticides and perfluorinated compounds) in 5362 groundwater (GW) and 12,344 drinking water (DW) samples, collected from 2012 to 2017 in 28 drinking water treatment plants in an urbanized area. This study demonstrates the benefits of MLELC method, especially for high percentages of censored data. Data are used to build statistical distributions which can be effectively used for several applications, such as the time trend evaluation of GW micropollutant concentrations and the estimation of treatment removal efficiency, highlighting the adequacy or the need for an upgrade. Moreover, the MLELC method has been applied to assess the human health risk associated with micropollutants, indicating the high discrepancy in the estimations obtained with conventional methods, whose results do not follow precautionary or sustainability criteria
Risk assessment of contaminants of emerging concern in the context of wastewater reuse for irrigation: An integrated modelling approach
Get PDFDirect reuse of reclaimed wastewater (RWW) in agriculture has recently received increasing attention as a possible solution to water scarcity. The presence of contaminants of emerging concern (CECs) in RWW can be critical, as these chemicals can be uptaken in irrigated crops and eventually ingested during food consumption.In the present study, an integrated model was developed to predict the fate of CECs in water reuse systems where RWW is used for edible crops irrigation. The model was applied to a case study where RWW (originating from a municipal wastewater treatment plant) is discharged into a water channel, with subsequent irrigation of silage maize, rice, wheat and ryegrass. Environmental and human health risks were assessed for 13 CECs, selected based on their chemical and hazard characteristics. Predicted CEC concentrations in the channel showed good agreement with available measurements, indicating potential ecotoxicity of some CECs (estrogens and biocides) due to their limited attenuation. Plant uptake predictions were in good agreement with existing literature data, indicating higher uptake in leaves and roots than fruits. Notably, high uncertainties were shown for weakly acidic CECs, possibly due to degradation in soil and pH variations inside plants. The human health risk due to the ingestion of wheat and rice was assessed using the threshold of toxicological concern and the hazard quotient. Both approaches predicted negligible risk for most CECs, while sulfamethoxazole and 17α-ethinylestradiol exhibited the highest risk for consumers. Alternative scenarios were evaluated to identify possible risk minimization strategies (e.g., adoption of a more efficient irrigation system)
Predicting the fate of pharmaceuticals in integrated urban wastewater systems
No full textA new category of substances, Pharmaceutical Active Compounds (PhACs), has been detected in different parts of integrated urban wastewater and stormwater (IUWS) systems. PhACs are characterized by different fate processes compared to those included in existing MP (MicroPollutants) fate modelling libraries. Thus, existing modelling tools cannot predict the fate of PhACs, and it is not possible to estimate the human and environmental risk due to their discharge in natural water. In this work a dynamic model library was developed to enable the simulation of PhACs across different IUWS elements (sewers, wastewater treatment plants, receiving water bodies). The model performance was assessed by simulating the fate of four PhACs in two different IUWS systems, where measurements were available. Model prediction capability was good, highlighting how the model can be a valuable support tool for a sustainable management of water in urban areas
An integrated modelling framework to assess cascade water reuse in urban areas
Get PDFIn the recent years water scarcity has been an increasing problem for many countries worldwide. For this reason, there is currently a strong focus on increasing reclaimed wastewater reuse, especially for agriculture purposes (Fernandes and Cunha Marques, 2023). Besides, the cost of energy from conventional resources is increasing, thus the energy sector is moving towards more distributed and efficient use of heat sources across urban areas. Typical applications are heat pumps using local groundwater reservoirs and subsequently discharging in the nearby surface water bodies/artificial channels (recipients). Furthermore, for a better quality of these recipients and for a better performance of wastewater treatment plants (WWTP), stormwater can be collected in separated sewers discharging only the urban runoff to the recipient. In this context, water is subjected to multiple uses, with potential cross-contaminations across different compartments, posing a risk for the environment. Hence, there is a strong need for tools capable of supporting stakeholders towards a wiser and safer use of water resources, to ensure long-term resilience, stability, sustainability and security of the society with regard to water use. An integrated model was developed to simulate the fate and associated risk of hazardous contaminants in a cascade water reuse system
Modelling the fate of micropollutants in integrated urban wastewater systems: Extending the applicability to pharmaceuticals
No full textPharmaceutical active compounds (PhACs) are a category of micropollutants frequently detected across integrated urban wastewater systems. Existing modelling tools supporting the evaluation of micropollutant fate in such complex systems, such as the IUWS_MP model library (which acronym IUWS stands for Integrated Urban Wastewater System), do not consider fate processes and fractions that are typical for PhACs. This limitation was overcome by extending the existing IUWS_MP model library with new fractions (conjugated metabolites, sequestrated fraction) and processes (consumption-excretion, deconjugation). The performance of the extended library was evaluated for five PhACs (carbamazepine, ibuprofen, diclofenac, paracetamol, furosemide) in two different integrated urban wastewater systems where measurements were available. Despite data uncertainty and the simplicity of the modelling approach, chosen to minimize data requirements, model prediction uncertainty overlapped with the measurements ranges across both systems, stressing the robustness of the proposed modelling approach. Possible applications of the extended IUWS_MP model library are presented, illustrating how this tool can support urban water managers in reducing environmental impacts from PhACs discharges
Modelling micropollutant fate in sewer systems – A new systematic approach to support conceptual model construction based on in-sewer hydraulic retention time
No full textConceptual sewer models are useful tools to assess the fate of micropollutants (MPs) in integrated wastewater systems. However, the definition of their model structure is highly subjective, and obtaining a realistic simulation of the in-sewer hydraulic retention time (HRT) is a major challenge without detailed hydrodynamic information or with limited measurements from the sewer network. This study presents an objective approach for defining the structure of conceptual sewer models in view of modelling MP fate in large urban catchments. The proposed approach relies on GIS-based information and a Gaussian mixture model to identify the model optimal structure, providing a multi-catchment conceptual model that accounts for HRT variability across urban catchment. This approach was tested in a catchment located in a highly urbanized Italian city and it was compared against a traditional single-catchment conceptual model (using a single average HRT) for the fate assessment of reactive MPs. Results showed that the multi-catchment model allows for a successful simulation of dry weather flow patterns and for an improved simulation of MP fate compared to the classical single-catchment model. Specifically, results suggested that a multi-catchment model should be preferred for (i) degradable MPs with half-life lower than the average HRT of the catchment and (ii) MPs undergoing formation from other compounds (e.g. human metabolites); or (iii) assessing MP loads entering the wastewater treatment plant from point sources, depending on their location in the catchment. Overall, the proposed approach is expected to ease the building of conceptual sewer models, allowing to properly account for HRT distribution and consequently improving MP fate estimation.</p
