IHE Delft Institute for Water Education
Recent publications
The effects of citizen science are wide ranging, influencing science, society, the economy, the environment, as well as individual participants. However, in many citizen science projects, impact evaluation is still overly simplistic. This is particularly the case when assessing the impact of participation in citizen science on the environmental attitudes, behaviour and knowledge of citizen scientists. In an attempt to bridge the gap between the state of the art in relevant scientific fields and citizen science, this systematic literature review identified best practices and approaches in the field of environmental psychology for measuring environmental attitudes, behaviour and knowledge. From the literature, five relevant and validated approaches were identified that can be used to measure changes in attitudes, behaviour and knowledge in citizen science projects. This would allow for improved understanding of the impacts of citizen science, as well as for improved project evaluation as a whole.
This study explored the feasibility of thermosonication (TS)-prestressed inoculum with different fermentation patterns for regulating microbial (post)-fermentation acidification kinetics. Through a Box-Behnken design, stimulative (20 min, 400 W, 33 kHz, 25 oC) and inhibitive (10 min, 600 W, 33 kHz, 20 oC) effects on the acidification capability of Lactobacillus plantarum A3 were achieved without observing greatly activated/inactivated strains growth, further confirmed by lactose fermentation performed by Streptococcus thermophilus and Lactobacillus bulgaricus. Lactic acid was the major contributing factor responsible for TS-induced acidification modifications corresponding to the potential fluctuations of CoA biosynthesis, fatty acid degradation and chain elongation pathways to TS prestress. Microscopy observations and quantitative extracellular substance assays showed palpable stress disturbance on microbes, but causing insignificant effects on products characteristics. This investigation demonstrated the potential of controlled sonication prestress strategies to achieve dual engineering effects on microbial metabolic behavior, for alleviating post-acidification problem or enhancing process efficiencies.
Process simulation approaches based on thermodynamics calculations can provide good capabilities to predict the ash behavior of biomasses and their mixtures. In the present work, a critical assessment of such simulations was performed in the field of biomass ashes, and experimentally checked to be at equilibrium. Two commercial thermodynamic databases, FToxid and GTOX, were used together with the FactSage Gibbs energy minimization software. For the first time in literature, a comparison was performed between the calculated phase equilibria using the recent market versions of the two databases. The predicted results were then compared to those measured on various ash samples of straws and barks along with their ash mixtures, highlighting the lingering need for improvements for the recent versions of these commercial databases. The phase diagram approach showed excellent capabilities in predicting the physical state of the ash (solid, liquid, or solid-liquid mixture) using both databases. Global simulations using the FToxid database showed better prediction capabilities for single biomass ash than those using the GTOX database. Unfortunately, predictions using the former were significantly limited in the case of ash mixture samples, whereas using the latter were a total failure. Nevertheless, both databases showed correct volatilization prediction capabilities but failed to forecast the solidus and liquidus characteristic temperatures. Further work is still needed to enhance the prediction capabilities of this tool.
This study investigated binding forms of cobalt (Co), copper (Cu), and lead (Pb) in 28 sediment samples from inlet to outlet of three Zambian wetlands receiving mining effluents. Use was made of a modified Tessier metal binding fractions procedure. Due to storage artefacts, the original aim of investigating the effects of redox potential (Eh) changes, starting from extremely low Eh, was suspended. Instead, use was made of the new, not often explored opportunity for replicate sample division into three categories of varying redox potential and pH. Additionally, in line with the original research aim, two sediments from each wetland were investigated for their response to increasing Eh. The results showed overall high trace metal contents, with a need for remedial actions for Co and Cu in the first, Cu in the second, and Pb in the third wetland. Rather independent of Eh and pH, Co was often found in the residual fraction (F5), as well as in the oxidizable (F4) and reducible (F3) fraction. Cu was generally dominant in F5 and F4 fractions, with low F3 prevalence, indicating a high organic matter affinity. Pb distribution among binding forms showed small variations within and across wetlands, F5, F4, and F3 fractions dominating. In the above observations, statistical analysis showed that, among the 28 sediment samples across wetlands, the influence of Eh and pH on binding forms were generally found to be not significant, being ‘overruled’ by other sedimentological factors. With increasing Eh, the decrease in the oxidizable (F4) fraction was smaller than expected in eight of 18 tests. The Risk Assessment Code (RAC) method, based on the exchangeable fraction (F1) plus carbonate fraction (F2), showed that some sediments turned from “unsafe” to “safe,” and vice versa, with increasing Eh. The “total metals method” does not show bioavailability, whereas RAC does not use the metal contents. Thus, the two methods should be used together to improve the prediction of potential toxicity.
During biomass gasification, both the char physical properties and the biomass inorganic composition are known to have a significant influence on the reaction kinetics. However, the impact of the inorganic content is more pronounced than the impact of the char features, though no clear explanations have been found in the literature yet. In order to clarify this point, two biomass species with significant inorganic composition differences were gasified under steam and the chars obtained at various conversion values were characterized. Both the char physicochemical properties (chemical composition, carbon structure, porosity, and surface chemistry) and the gasification kinetic behavior were analyzed. A particular focus on the inorganic elemental composition and inorganic compound nature were performed. Experimental results were compared with simulation results at thermodynamic equilibrium obtained with the FactSage 7.2 software. The results showed that the physical properties of the carbon matrix do not have a strong influence on the gasification reactivity. In contrast, the inorganic composition could explain the differences between the gasification kinetic behaviors of the two investigated chars (obtained starting from two different biomass sources).
Mining activities depend significantly on water resources availability as it consists a major tool of the extraction, processing and the post closure mining operations. Especially, groundwater is the major water source in most mining areas. However, overexploitation, competition from the communities and climate change effects have caused significant stress on the groundwater resources in many areas of the Mediterranean basin. The sustainability of mining operations is threatened as well as the uninterrupted supply of raw materials to the industry. In this work spatial estimation and analysis of groundwater stress at hydrological basin-scale in the European part of the Mediterranean region is applied using local and global datasets. Aquifer productivity index and groundwater use information at monitoring sites are extracted from the River Basin Management Plans of the European Environment Agency, while groundwater recharge is considered from the World-wide Hydrogeological Mapping and Assessment Program (WHYMAP) after validation. The processing of these data using the Self Organized Maps technique and their integration within a novel function, provide the groundwater stress index. The output of this work can be used for governance and management decisions that will improve groundwater resources availability in vulnerable areas ensuring the sustainable use from the communities and the industry.
A practical approach for understanding and monitoring the sustainability of a river basin as a complex socio-hydrological system is to co-develop an indicator-based assessment framework with the help of the major stakeholders. This study defines the concept of Sustainability Assessment (SA) in the context of water management at basin level. A step-by-step methodology is proposed and further applied for developing indicator-based SA framework in the complex and overexploited Mashhad Basin in Iran. The methodology is based on a participatory approach that includes forming an expert panel of basin stakeholders, co-creating goals and objectives, identifying and screening indicators, and shaping the final SA framework. We identify 332 potential indicators from existing literature. Using selection criteria and two-round of fuzzy Delphi method, we adapt 25 fit-for-purpose indicators relevant to sustainable water management in Mashhad Basin. Subsequently, a SA framework is developed by categorizing final indicators into four main components (Technical, Environmental, Economic and Social) and ten subcomponents to provide better links and insights of the basin water management practices between different groups of stakeholders. Finally, using a weighting scheme through the Analytical Hierarchy Process (AHP), a sustainability index is constructed by aggregating the indicators. The results indicate that Mashhad Basin is in a critical unsustainable condition with a sustainability index at 0.34 out of 1. Analysis of the relative importance of the adapted indicators shows that the top-four ranked indicators (including water productivity, access to safe drinking water, renewable groundwater dependency and water pollution) have almost 40% contribution to the basin sustainability index. Such indicator-based SA framework can support identification and analysis of major sustainability trade-offs. Additionally, it can provide an effective tool for achieving water-related targets of the Sustainable Development Goals (SDGs). We therefore highly encourage further development of indicator-based SA frameworks in the context of water management at basin level.
Several wastewater treatment plants (WWTPs) worldwide have documented the occurrence of filamentous bulking in full-scale systems despite the efforts made for filamentous bulking control. The Activated Sludge Models (ASM) can neither describe nor predict filamentous bulking at WWTPs. This research aims to expand the ASM No. 1 to be able to describe filamentous bulking sludge and to model the effects of incorporating an aerobic selector on filamentous bulking. Four theories (hydrolysis of slowly biodegradable organics theory, kinetic selection theory, substrate diffusion limitation theory, and filamentous backbone theory) were combined to expand the ASM1. The results showed that this combination was successful to distinguish between the substrate uptake by filamentous organisms and by floc forming organisms. Moreover, the concentrations of filamentous and floc forming organisms inside the reactor were converted to a “filamentous score” that predicted the outcome of filamentous bulking. Filamentous bulking would occur if the filamentous score was higher than 3, in a range of 1–6. As a case study, the Fuhais WWTP in Jordan was modelled using the expanded-ASM1 “filamentous model” and the filamentous score of 4.2 was in accordance to the visually observed bulking. However, when an aerobic selector with 3 compartments would be added before the aeration tank, the filamentous score decreased to 1.5. The selector changed the hydraulic behaviour from a completely mixed mode to a plug flow mode, which created a substrate gradient in the model, making the floc forming organisms to outcompete the filamentous organisms. Additional experimental results are required to further calibrate and validate the filamentous model.
Study region Nile basin. Study focus Several studies have shown a relationship between climate change and changes in sediment yield. However, there are limited modeling applications that study this relationship at regional scales mainly due to data availability and computational cost. This study proposes a methodological framework using the SWAT+ model to predict and project sediment yield at a regional scale in data-scarce regions using global datasets. We implement a framework that (a) incorporates topographic factors from high/medium resolution DEMs (b) incorporates crop phenology data (c) introduces an areal threshold to linearize sediment yield in large model units and (d) apply a hydrological mass balance calibration. We test this methodology in the Nile Basin using a model application with (revised) and without (default) the framework under historical and future climate projections. New hydrological insights for the region Results show improved sediment yield estimates in the revised model, both in absolute values and spatial distribution when compared to measured and reported estimates. The contemporary long term (1989 – 2019) annual mean sediment yield in the revised model was 1.79 t ha⁻¹ yr⁻¹ and projected to increase by 61 % (44 % more than the default estimates) in the future period (2071 – 2100), with the greatest sediment yield increase in the eastern part of the basin. Thus, the proposed framework improves and influences modeled and predicted sediment yield respectively.
In recent years, due to rapid globalization and urbanization, the demand for fuels, energy, water and nutrients has been continuously increasing. To meet the future need of the society, wastewater is a prominent and emerging source for resource recovery. It provides an opportunity to recover valuable resources in the form of energy, fertilizers, electricity, nutrients and other products. The aim of this review is to elaborate the scientific literature on the valorization of wastewater using wide range of treatment technologies and reduce the existing knowledge gap in the field of resource recovery and water reuse. Several versatile, resilient environmental techniques/technologies such as ion exchange, bioelectrochemical, adsorption, electrodialysis, solvent extraction, etc. are employed for the extraction of value-added products from waste matrices. Since the last two decades, valuable resources such as polyhydroxyalkanoate (PHA), matrix or polymers, cellulosic fibers, syngas, biodiesel, electricity, nitrogen, phosphorus, sulfur, enzymes and a wide range of platform chemicals have been recovered from wastewater. In this review, the aspects related to the persisting global water issues, the technologies used for the recovery of different products and/or by-products, economic sustainability of the technologies and the challenges encountered during the valorization of wastewater are discussed comprehensively.
This study aimed to quantify the effect of membrane surface porosity on particulate fouling predicted by the MFI-UF method at constant flux. Firstly, the surface porosity of polyethersulfone UF membranes (5–100 kDa) was determined using ultra-high resolution SEM. Thereafter, the MFI-UF was measured using suspensions of polystyrene particles (75 nm), which were pre-washed to remove surfactant and particle fractions smaller than the pores of MFI-UF membranes, thus ensuring complete retention of particles during MFI-UF measurements. Consequently, the MFI-UF values of washed polystyrene particle suspensions were independent of the pore size and depended only on the surface porosity of MFI-UF membrane. The results showed that the membrane surface porosity decreased with MWCO from 10.5% (100 kDa) to 0.6% (5 kDa), and consequently the MFI-UF increased from 3700 to 8700 s/L², respectively. This increase in MFI-UF was attributed to the non-uniform distribution of membrane pores, which is exacerbated as surface porosity decreases. Consequently, preliminary correction factors of 0.4–1.0 were proposed for MFI-UF measured with UF membranes in the range 5–100 kDa. Finally, the surface porosity correction was applied to predict particulate fouling in a full-scale RO plant. However, additional research is required to establish correction factors for different types of feed water.
A popular approach to select optimal adsorbents is to perform parallel experiments on adsorbents based on an initially decided goal such as specified product purity, efficiency, or binding capacity. To screen optimal adsorbents, we focused on the max adsorption capacity of the candidates at equilibrium in this work because the adsorption capacity of each adsorbent is strongly dependent on certain conditions. A data-driven machine learning tool for predicting the max adsorption capacity (Qm) of 19 pharmaceutical compounds on 88 biochars was developed. The range of values of Qm (mean 48.29 mg/g) was remarkably large, with a high number of outliers and large variability. Modified biochars enhanced the Qm and surface area values compared with the original biochar, with a statistically significant difference (Chi-square value = 7.21–18.25, P < 0.005). K- nearest neighbors (KNN) was found to be the most optimal algorithm with a root mean square error (RMSE) of 23.48 followed by random forest and Cubist with RMSE of 26.91 and 29.56, respectively, whereas linear regression and regularization were the worst algorithms. KNN model achieved R² of 0.92 and RMSE of 16.62 for the testing data. A web app was developed to facilitate the use of the KNN model, providing a reliable solution for saving time and money in unnecessary lab-scale adsorption experiments while selecting appropriate biochars for pharmaceutical adsorption.
Biogas-based biopolymer production represents an alternative biogas valorization route with potential to cut down plastic pollution and greenhouse gas emissions. This study investigated for the first time the continuous bioconversion of methane, contained in biogas, into poly(3-hydroxybutyrate) (PHB) by a mixed methanotrophic culture using an innovative high mass-transfer Taylor flow bioreactor. Following a hydrodynamic flow regime mapping, the influence of the gas residence time and the internal gas recirculation on CH4 abatement was assessed under non nutrient limiting conditions. Under optimal operational conditions (gas residence time of 60 min and internal gas recycling ratio of 17), the bioreactor was able to support a CH4 removal efficiency of 63.3%, a robust CH4 elimination capacity (17.2 g-CH4 m-3h-1) and a stable biomass concentration (1.0 g L-1). The simultaneous CH4 abatement and PHB synthesis was investigated under 24-h:24-h nitrogen feast/famine continuous operation. The cyclic nitrogen starvation and the Taylor flow imposed in the bioreactor resulted in a relatively constant biomass concentration of 0.6 g L-1 with PHB contents ranging from 11 to 32% w w-1 (on a dry weight basis), entailing an average PHB productivity of 5.9 g-PHB m-3 d-1 with an associated PHB yield of 19.8 mg-PHB g-CH4-1. Finally, the molecular analysis of the microbial population structure indicated that type II methanotrophs outcompeted non-PHB accumulating type I methanotrophs, with a heterotrophic-methanotrophic consortium enriched in Methylocystis, Hyphomicrobium, Rubinisphaeraceae SH PL14 and Pseudonocardia.
Particle tracers are sometimes used to track sources and sinks of riverine particulate and contaminant transport. A potentially new particle tracer is ~200 nm sized superparamagnetic silica encapsulated DNA (SiDNAFe). The main objective of this research was to understand and quantify the settling and aggregation behaviour of SiDNAFe in river waters. Our results indicated, that in quiescent conditions, more than 60% of SiDNAFe settled within 30 hours, starting with a rapid settling phase followed by an exponential-like slow settling phase in the three river waters we used (Meuse, Merkske, and Strijbeek) plus MilliQ water. From this, we inferred that the rapid SiDNAFe settling was mainly due to homo-aggregation and not due to hetero-aggregation (e.g., with particulate matter present in river water). Incorporating a first-order mass loss term which mimics the exponential phase of the settling in quiescent conditions seems to be an adequate step forward when modelling the transport of SiDNAFe in river injection experiments. Furthermore, we validated the applicability of magnetic separation and up-concentration of SiDNAFe in real river waters, which is an important advantage for carrying out field-scale SiDNAFe tracing experiments.
Cascading hazards are becoming more prevalent in the central Himalayas. Primary hazards (e.g., earthquakes, avalanches, and landslides) often trigger secondary hazards (e.g., landslide dam, debris flow, and flooding), compounding the risks to human settlements, infrastructures, and ecosystems. Risk management strategies are commonly tailored to a single hazard, leaving human and natural systems vulnerable to cascading hazards. In this commentary, we characterize diverse natural hazards in the central Himalayas, including their cascading mechanisms and potential impacts. A scientifically sound understanding of the cascading hazards, underlying mechanisms, and appropriate tools to account for the compounding risks are crucial to informing the design of risk management strategies. We also discuss the need for an integrated modeling framework, reliable prediction and early warning system, and sustainable disaster mitigation and adaptation strategies.
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1,308 members
Maria D Kennedy
  • Department of Environmental Engineering and Water Technology
Carlos M Lopez-Vazquez
  • Department of Environmental Engineering and Water Technology
Jaap Evers
  • Department of Integrated Water Systems and Governance
Jan Willem Foppen
  • Department of Water Science and Engineering
Shreedhar Maskey
  • Department of Water Science and Engineering
Delft, Netherlands