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The level of microplastics (MPs) in wastewater treatment plants (WWTPs) has been well evaluated by the particle number, while the mass concentration of MPs and especially nanoplastics (NPs) remains unclear. In this study, pyrolysis gas chromatography-mass spectrometry was used to determine the mass concentrations of MPs and NPs with different size ranges (0.01-1, 1-50, and 50-1000 μm) across the whole treatment schemes in two WWTPs. The mass concentrations of total MPs and NPs decreased from 26.23 and 11.28 μg/L in the influent to 1.75 and 0.71 μg/L in the effluent, with removal rates of 93.3 and 93.7% in plants A and B, respectively. The proportions of NPs (0.01-1 μm) were 12.0-17.9 and 5.6-19.5% in plants A and B, respectively, and the removal efficiency of NPs was lower than that of MPs (>1 μm). Based on annual wastewater effluent discharge, it is estimated that about 0.321 and 0.052 tons of MPs and NPs were released into the river each year. Overall, this study investigated the mass concentration of MPs and NPs with a wide size range of 0.01-1000 μm in wastewater, which provided valuable information regarding the pollution level and distribution characteristics of MPs, especially NPs, in WWTPs.

Slow Sand Filtration is popular in drinking water treatment for the removal of a wide range of contaminants (e.g., particles, organic matter, and microorganisms). The Schmutzdecke in slow sand filters (SSFs) is known to be essential for pathogen removal, however, this layer is also responsible for increased head loss. Since the role of deeper layers in bacteria and virus removal is poorly understood, this research investigated the removal of E.coli WR1 and PhiX 174 at different depths of a full-scale SSF. Filter material from top (0–5 cm), middle (5–20 cm) and deep (20–35 cm) layers of an established filter was used in an innovative experimental set-up to differentiate physical-chemical and biological removal processes. In the analysis, we distinguished between removal by biological activity, biofilm and just sand. In addition, we modelled processes by a one-side kinetic model. The different layers contributed substantially to overall log removal of E.coli WR1 (1.4–1.7 log10) and PhiX 174 (0.4–0.6 log10). For E.coli WR1, biological activity caused major removal, followed by removal within biofilm and sand, whereas, removal of PhiX 174 mainly occurred within sand, followed by biofilm and biological activity. Narrow pore radii in the top layer obtained by micro-computed tomography scanner suggested enhanced retention of bacteria due to constrained transport. The retention rates of E.coli WR1 and PhiX 174 in top layer were four and five times higher than deeper layers, respectively (kret 1.09 min−1 vs 0.26 min−1 for E.coli WR1 and kret 0.32 min−1 vs of 0.06 min−1 for PhiX 174). While this higher rate was restricted to the Schmutzdecke alone (top 5 cm), the deeper layers extend to around 1 m in full-scale filters. Therefore, the contribution of deeper layers of established SSFs to the overall log removal of bacteria and viruses is much more substantial than the Schmutzdecke.

Nanoplastics (NPs) are currently considered an environmental pollutant of concern, but the actual extent of NP pollution in environmental water bodies remains unclear and there is not enough quantitative data to conduct proper risk assessments. In this study, a pretreatment method combining ultrafiltration (UF, 100 kDa) with hydrogen peroxide digestion and subsequent detection with pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) was developed and used to identify and quantify six selected NPs in surface water (SW) and groundwater (GW), including poly(vinylchloride) (PVC), poly(methyl methacrylate) (PMMA), polypropylene (PP), polystyrene (PS), polyethylene (PE), and poly(ethylene terephthalate) (PET). The results show that the proposed method could detect NPs in environmental water samples. Nearly all selected NPs could be detected in the surface water at all locations, while PVC, PMMA, PS, and PET NPs were frequently below the detection limit in the groundwater. PP (32.9-69.9%) and PE (21.3-44.3%) NPs were the dominant components in both surface water and groundwater, although there were significant differences in the pollution levels attributed to the filtration efficiency of riverbank, with total mass concentrations of 0.283-0.793 μg/L (SW) and 0.021-0.203 μg/L (GW). Overall, this study quantified the NPs in complex aquatic environments for the first time, filling in gaps in our knowledge about NP pollution levels and providing a useful methodology and important reference data for future research.

To reduce worldwide greenhouse gas (GHG) emissions, fossil fuels are being replaced by renewable energy in a rapid tempo. As a result, the energy system becomes more decentralized with e.g. PV systems as a source for local multi-energy systems, with aim to become as self-sustainable as possible. This is challenging because these systems often rely on an intermittent energy source (production mainly in summer), which is not aligned with energy demand (mainly in winter). One solution for this problem is the combination of power-to-heat (PtH) with High Temperature Aquifer Thermal Energy Storage (HT-ATES), which allows for flexible and effective utilisation and storage of available green electricity to match the availability and demand of sustainable electricity. Currently, insights in the practical potential of this solution and methods for effective integration of PtH and HT-ATES in multi-energy systems are lacking. Therefore, we assessed methods to improve the integration and control of a HT-ATES system and tested varying ways of integration for a local decentralized multi-energy system. To this end, we expanded and integrated a multi-energy system model with a numerical hydro-thermal model to dynamically simulate the functioning of the integrated HT-ATES. The impact of key design parameters (heat pump size, storage temperature, cut-off temperature) on overall energy performance and the effect of different methods for integration of the local energy system were simulated and analysed. Results show that the integration of HT-ATES with PtH allows for providing the local energy system with 100% of the yearly heat demand with a 25% smaller heat pump than without HT-ATES. Also, compared to Pth without storage, the yearly energy use pattern changes dramatically to match the availability of renewable electricity. An inventive mode of operation was designed which allows for lowering the threshold temperature of the HT-ATES by an innovative integration of the heat pump. This mode of operation increases the HT-ATES performance and decreases the overall costs of heat production. Overall, this study shows that the integration of HT-ATES in a multi-energy system is suitable to cost-effectively match annual heat demand and supply, and to increase local sustainable energy use. Solutions like these show high potential to decentralize energy production/use, to decrease pressure on the power grid and to increase total renewable energy use.

Recovering phosphorus from wastewater in more concentrated forms has potential to sustainably recirculate phosphorus from cities to agriculture. The environmental sustainability of wastewater-based phosphorus recovery processes or wastewater-derived phosphorus products can be evaluated using life cycle assessment (LCA). Many LCA studies used a process perspective to account for the impacts of integrating phosphorus recovery processes at wastewater treatment plants, while some used a product perspective to assess the impacts of producing wastewater derived phosphorus products. We demonstrated the application of an end-user perspective by assessing life cycle environmental impacts of substituting half of the conventional phosphorus rock-based fertilizers used in three crop production systems with wastewater derived phosphorus products from six recovery pathways (RPs). The consequential LCA results show that the substitution reduces global warming potential, eutrophication potential, ecotoxicity potential, and acidification potential of the assessed crop production systems in most RPs and scenarios. The end-user perspective introduced in this study can (i) complement with the process perspective and the product perspective to give a more holistic picture of environmental impacts along the "circular economy value chains " of wastewater-based resource recovery, (ii) enable systemwide assessment of wide uptake of wastewater-derived products, and (iii) draw attention to understanding the long-term environmental impacts of using wastewater-derived products.

Organic micropollutants (OMPs) that occur in the aquatic environment are an emerging concern. Adsorption by granular zeolites and regenerating exhausted zeolites by gaseous ozone is an innovative and advanced treatment technology for removing OMPs from wastewater treatment plant (WWTP) effluent. In this study, WWTP effluent spiked with eleven OMPs at 4–5 µg/L was treated by this combined technology, which included five steps in each cycle. The five steps comprised 1) selective adsorption of OMPs from WWTP effluent for five days by a zeolite granules fixed-bed column, 2) pre-backwash of the column, 3) drying of the column, 4) in-situ regeneration of the column with gaseous ozone 5) post-backwash of the column. The removal efficiency of eight OMPs (sotalol, metoprolol, propranolol, trimethoprim, clarithromycin, carbamazepine, methyl-benzotriazole, and benzotriazole) reached between 70 % and 100 % in six cycles. The adsorption of sulfamethoxazole and diclofenac was less favourable. In each cycle, less than 8 % of dissolved organic carbon (DOC) was removed from the WWTP effluent. The effect of the natural organic matter (NOM) on the adsorption of OMPs was negligible. Ozone consumption during regeneration was reduced by around 70 % by increasing pre-backwash duration from 30 min to 1 h. Ozonation directly with ozone gas can effectively regenerate the zeolite granules in the column under low ozone consumption.

Powdered activated carbon (PAC) is a promising technology to reduce organic micropollutants (OMPs) in drinking water treatment plants and combined with biological treatment processes such as rapid sand filters (RSFs), has the potential to remove a broad range of OMPs during water treatment. However, the removal of OMPs by a combination of two treatments (PAC-RSF) is not fully understood. 49 OMPs were spiked in PAC followed by RSF pilot plant treatment and the effluent was measured after 1, 4 and 7 day(s). Also, in a separate experiment 29 OMPs (out of 49) were dosed into the RSF column to assess the removal of OMPs by just RSF. Statistical analyses were performed and the OMPs were classified according to their charge and hydrophobicity. The results showed that OMPs were removed at the highest percentage after the first 24 h of dosing. The highest removal was observed for the neutral and hydrophobic compounds (80.0%–99.5%). The removal of neutral and hydrophilic compounds varied (0.14%–98.5%) depending on the possibility of forming π-π interactions and hydrogen bonds. Electrostatic repulsion between anionic OMPs and negatively charged PAC led to a decrease in the removal of anionic compounds. In contrast, electrostatic attraction led to an increase in the removal of cationic OMPs. Regarding OMPs removal by RSF, some compounds were removed by the sand filter depending partly on their physical-chemical properties and more dominantly on their functional groups. By comparing the OMPs removal by PAC-RSF with RSF, it was possible to determine the contribution of biological processes in the sand filter in the removal of some OMPs.

The transport and fate of nanoplastics (NPs) in aquatic environments are closely associated with their colloidal stability, which is affected by aging and natural organic matter (NOM) adsorption. This study systematically investigated the combined effects of photoaging and NOM (e.g. humic acids, HA; and a model protein, bovine serum albumin, BSA) on the aggregation kinetics of NPs (polystyrene, PS) in NaCl and CaCl2 solutions. Our results showed that photoaged NPs adsorbed less HA than pristine NPs due to weaker hydrophobic and π-π interactions. In return, HA showed weaker impacts on NPs’ stability after photoaging. Differently, photoaged NPs absorbed more BSA than pristine NPs due to stronger hydrogen bonding and electrostatic attraction. Thus, the inhibitory effects of BSA on the aggregation kinetics of NPs were enhanced after photoaging. Regarding the effects of NOM on the aging of NPs, our results showed that HA competed with NPs for photons and underwent photo-degradation. Subsequently, the destruction/reconstruction of adsorbed HA increased (in NaCl) or decreased (in CaCl2) the stability of NPs. Notably, light radiation-induced flocculation of BSA molecules, which wrapped and integrated NPs and lead to their destabilization. Overall, this study provided new insights into the aggregation behavior of NPs in aquatic systems, which have significant implications for predicting the transport and fate of NPs in complex real-world environments.

The UV/Cl2 process (also known as chlorine photolysis, which is the combination of chlorine and simultaneous irradiation of UV light) is conventionally applied at acidic mediums for drinking water treatment and further treatment of wastewater effluents for secondary reuse. This is because the quantum yield of HO• from HOCl (ϕHO•, 254 = 1.4) is greater than the one from OCl- (ϕHO•, 254 = 0.278) by approximately 5 times. Moreover, chlorine photolysis in acidic mediums also tends to have lower radical quenching rates than that of their alkaline counterparts by up to 1000 times. The aim of this research is to investigate the applicability of the UV/Cl2 process by assessing its efficacy on the removal of trimethoprim (TMP) at not only acidic to neutral conditions (pH 6-7), but also alkaline mediums (pH 8-9). At alkaline pH, free chlorine exists as OCl- and since OCl- has a higher molar absorption coefficient as compared to HOCl at higher wavelengths, there would be higher reactive chlorine species (RCS) formation and contribution. TMP removal followed pseudo-first order kinetics and depicted that a maximum fluence based constant (kf′ = 0.275 cm2/mJ) was obtained using 42.25 μM (3 mg/L) of chlorine at pH 9, with an irradiation of 275 nm. At alkaline conditions, chlorine photolysis performance followed the trend of UV (275)/Cl2 > UV (265)/Cl2 > UV (310)/Cl2 > UV (254)/Cl2. RCS like Cl•, Cl2−• and ClO• contributed to the degradation of TMP. When the pH was increased from 6 to 8, contribution from hydroxyl radicals (HO• ) was decreased whilst that of RCS was increased. Application of UV (310)/Cl2 had the highest HO• generation, contributing to TMP removals up to 13% to 48% as compared to 5% to 27% in UV (254, 265, 275)/Cl2 systems at pH 6-9. Artificial neural networks modelling was found to be able to verify and predict the contribution of HO• and RCS conventionally calculated via the general kinetic equations in the UV/Cl2 system at 254, 265, 275 and 310 nm.

During drinking water treatment, advanced oxidation process (AOP) with O3 and H2O2 may result in by-products, residual H2O2 and BrO3−. The water containing H2O2 and BrO3− often flows into subsequent granular activated carbon (GAC) filters. A concentrated H2O2 solution can be used as GAC modification reagent at 60 °C to improve its adsorption ability. However, whether low concentrations of H2O2 residuals from AOP can modify GAC, and the impact of H2O2 residuals on BrO3− removal by the subsequent GAC filter at ambient temperature, is unknown. This study evaluated the modification of GAC surface functional groups by residual H2O2 and its effect on BrO3− removal by GAC. Results showed that both H2O2 and BrO3− were effectively removed by virgin GAC, while pre-loaded and regenerated GACs removed H2O2 but not BrO3− anymore. At the ambient temperature 150 µmol/L H2O2 residuals consumed large amounts of functional groups, which resulted in the decrease of BrO3− removal by virgin GAC in the presence of H2O2 residuals. Redox reactions between BrO3− and surface functional groups played a dominant role in BrO3− removal by GAC, and only a small amount of BrO3− was removed by GAC adsorption. The higher the pH, the less BrO3− removal and the more H2O2 removal was observed.

Riverbank filtration (RBF) as a barrier of pathogenic microorganisms and organic micropollutants recently has been proven capable of removing sulfonamides. However, the study about the effect of redox conditions on biodegradation of common and persistent sulfonamides in RBF is limited and the response of microbial communities to sulfonamides stress during RBF is unknown. In this study, two column set-ups (with residence time 5 days and 11 days respectively), simulating different redox conditions of riverbank filtration systems, were operated for seven months to investigate 1) the long-term effect of redox conditions on ng∙L−1 level sulfonamides (sulfapyridine, sulfadiazine, sulfamethoxazole, sulfamethazine, sulfaquinoxaline) removal, and 2) the microbial community evolution represented by the phylogenetic and metabolic function shift under non-lethal selective pressures of sulfonamides. The results showed that sulfonamides were more degradable under anoxic conditions than oxic and suboxic conditions. In the sulfonamides stressed community, the phylogenetic diversity increased slightly. Relative abundance of an intrinsic sulfonamides resistant bacteria Bacillus spp. increased, suggesting that sulfonamide resistance developed in specific bacteria under sulfonamides contamination pressure in RBF systems. At the same time, an activated transport function in the stressed microbial community was noticed. The predicted relative abundance of gene folP, which encodes dihydropteroate synthase, also increased significantly, indicating a detoxification mechanism and sulfonamides resistance potential under non-lethal selective pressures of sulfonamides in RBF systems.

Biological activated carbon (BAC) filtration is usually considered to be able to decrease formation potentials (FPs) of disinfection by-products (DBPs) in drinking water treatment plant (DWTP). However, BAC filters with long running time may release microbial metabolites to effluents and therefore increase FPs of nitrogenous DBPs with high toxicity. To verify this hypothesis, this study continuously tracked BAC filters in a DWTP for one year, and assessed effects of old (running time 8–9 years) and new (running time 0–13 months) BAC filters on FPs of 15 regulated and unregulated DBPs. Results revealed that dissolved organic carbon (DOC) removal was slightly higher in the new BAC than the old one. All fluorescent components of dissolved organic matter evidently declined after new BAC filtration, but fulvic acid-like and soluble microbial product-like substances increased after old BAC filtration, which could be caused by microbial leakage. Correspondingly, new BAC filter generally removed more DBP FPs than the old one. 46.5% HAA7 FPs from chlorination and 44.3% THM4 FPs from chloramination were removed by new BAC filter. However, some DBP FPs, especially HAN FPs, were poorly removed or even increased by the old BAC filter. Proteobacteria could be a main contributor for DBP precursor removal in BAC filters. Herminiimonas, most abundant genera in new BAC filter, may explain its better DOC and UV254 removal performance and lower DBP FPs, while Bradyrhizobium, most abundant genera in old BAC filter, might produce more extracellular polymeric substances and therefore increased N-DBP FPs in old BAC effluent. This study provided insight into variations of DBP FPs and microbial communities in the new and old BAC filters, and will be helpful for the optimization of DWTP design and operation for public health.

Resource recovery solutions are an essential part of a sustainable water sector. Sustainability of these solutions needs to be analysed to assess, compare and optimize them. Life Cycle Sustainability Assessment (LCSA) is the most commonly used framework for sustainability assessment. This review paper discusses three critical characteristics of water sector resource recovery solutions: (i) their potential to actively benefit natural processes through reciprocal services, (ii) their dependence upon natural resources and processes, and (iii) their goal to avoid transgression of environmental thresholds. We analyse these three characteristics in the context of the following features of LCSA: (i) it being a damage assessment-based framework, (ii) its treatment of economic and natural capital as substitutable and (iii) the absence of environmental thresholds and past emissions in its environmental assessment methodology. We use a real-life resource recovery case study from the Netherlands to evaluate and demonstrate the mentioned features of the existing LCSA framework. Our review indicates that, LCSA can be modified for application to resource recovery solutions if it includes reciprocity towards nature as an essential component, limits compensations between economic welfare and environmental damage, and incorporates environmental thresholds and past emissions.

Magnetic seeding coagulation (MSC) process has been used to accelerate flocs sedimentation with an applied magnetic field, offering large handling capacity and low energy consumption. The interactions of three typical Al species, aluminum chloride (AlCl3), Al13O4(OH)247+ polymer (Al13), and (AlO4)2Al28(OH)5618+ polymer (Al30), with magnetic particles (MPs) were examined to clarify the MSC process. In traditional coagulation (TC) process, the aggregation of primary Ala-dissolved organic matter (DOM) complexes with in-situ-formed polynuclear species generated a large average floc size (226 μm), which was proved to be efficient for DOC removal (52.6%). The weak connections between dissolved Ala-DOM complexes and MPs led to the negligible changes of dissolved Al after seeding with MPs in AlCl3. A significant interaction between MPs and Al13 was observed, in which the MPs-Al13-DOM complexes were proposed to be responsible for the significant improvement of DOC removal (from 47% to 52%) and residual total Al reduction (from 1.05 to 0.27 mg Al L−1) with MPs addition. Al30 produced a lower floc fractal dimension (Df = 1.88) than AlCl3 (2.08) and Al13 (1.99) in the TC process, whereas its floc strength (70.9%) and floc recovery (38.5%) were higher than the others. Although more detached fragments were produced with MPs addition, the effective sedimentation of these fragments with the applied magnetic field led to the decrease of residual turbidity and colloidal Al in Al30. The dependence of coagulation behavior to MPs and different Al species can be applied to guide the application of an effective MSC process.

The presence of trace levels of pharmaceutically active compounds (PhACs) in the aquatic environment threatens human health and the environment. Metronidazole (MNZ) is a soluble PhAC with low biodegradability, a possible human mutant and carcinogen. This study aimed the synthesis, physicochemical characterizations, and employment of porous amine-modified green-graphene (AMGG) for MNZ removal from aqueous solutions. Response-surface methodology (RSM) based on Box-Benken design (BBD) was used to assess the MNZ adsorption efficiency of AMGG as a function of pH (4–12), contact time (5–60 min), AMGG dose (0.1–1 g/L) and MNZ concentration (10–100 mg/L). From the model optimization, the highest MNZ removal was predicted at a pH of 5.9, a contact time of 27 min, an AMGG dose of 0.86 g /L, and an MNZ concentration of 100 mg /L. The experimental data were in agreement with the pseudo-second order kinetic model and the Langmuir isotherm model. The maximum adsorption capacity of AMGG for MNZ was 416.7 mg/g. The MNZ concentration at equilibrium increased about 4.8 mg/L when the solution temperature increased by 20 oC (from 30 to 50 °C), indicative of an exothermic process. AMGG showed an efficiency decrement from 84 % to 57 %, after five consecutive saturation-regeneration cycles. Moreover, AMGG showed a removal efficiency of 74 % when it was employed for real hospital wastewater treatment.

Removal of contaminants of emerging concern (CECs) from municipal wastewater is becoming more and more important. On-site regeneration of exhausted adsorbents can be the key to practical applications. In this study, ozone-based regeneration of granular zeolites loaded with acetaminophen (ACE) was investigated. The adsorption capacity of ACE was 90 mg/g. After adsorption and breakthrough in column tests, granular zeolites were drained and dried for regeneration. Water content in granules is the main factor that limits the regeneration performance by affecting the gaseous ozone transfer rate. Ozone-based regeneration of fully dried granular zeolites (0% water content) is the most efficient, whereas fully wet granules (40% water content) have poor regeneration efficiency. Various ozone concentrations and gas flow rates were applied. With the same total mass of ozone dosed (900 mg), the regeneration efficiency increased by increasing the ozonation duration up to 50 min. The longer the regeneration time, the deeper the gaseous ozone can diffuse into the inner pores of zeolites to decompose the adsorbed ACE. The effect of gaseous ozone on the adsorption capacity of zeolites and the effect of the intermediates accumulation on the long-term adsorption capacity recovery rate were also investigated. It was found that gaseous ozone did not influence the adsorption of ACE on zeolites. The adsorption capacity of ACE decreased 7% after three adsorption-regeneration cycles. This can be explained by the accumulation of undissolved intermediate breakdown products adsorbed on the granules.

A novel sol-gel method was employed in this study to efficiently synthesize SnO2 nanoparticles to catalyze the ozonation of acetaminophen (ACT) from aqueous solutions. The influence of various parameters including Sn source, type of capping and alkaline agents, and calcination temperature on the catalytic activity of the SnO2 preparations was investigated. The SnO2 nanoparticles prepared by tin tetrachloride as Sn source, NaOH as gelatin agent, CTAB as capping agent and at calcination temperature of 550 °C (SnNaC-550) exhibited the maximum performance in the catalysis of ACT. The optimized catalyst (SnNaC-550) had spherical-homogeneous and cubic-shaped nanocrystalline particles with 5.5 nm mean particle size and a BET surface area of 81 m2/g, which resulted in 98% degradation and 84% mineralization of 50 mg/L ACT at 20 and 30 min reaction time, respectively when combined with ozonation (COP). Based on the radical scavenger experiments, •OH was the major oxidizing agent involved in the removal of ACT. LC/MS analysis showed that short-chain carboxylic acids were the main intermediates. Furthermore, the SnNaC-550 catalytic activity was preserved after four successive cycles. Collectively, the new method has the potential to efficiently synthesize stable and reusable SnO2 nanoparticles to catalyze the ozonation of ACT from aquatic environments.

Fluid flow through a bed of solid particles is an important process that occurs in full-scale water treatment operations. The Carman–Kozeny model remains highly popular for estimating the resistance across the bed. It is common practice to use particle shape factors in fixed bed state to match the predicted drag coefficient with experimentally obtained drag coefficients. In fluidised state, however, where the same particles are considered, this particle shape factor is usually simply omitted from the model without providing appropriate reasoning. In this research, it is shown that a shape factor is not a constant particle property but is dependent on the fluid properties as well. This dynamic shape factor for irregularly shaped grains increases from approximately 0.6 to 1.0 in fluidised state.We found that unstable packed beds in moderate up-flow conditions are pseudo-fixed and in a setting state. This results in a decreasing bed voidage and simultaneously in a decreasing drag coefficient, which seems quite contradictory. This can be explained by the collapse of local channels in the bed, leading to a more uniform flow distribution through the bed and improving the available surface for flow-through. Our experimental measurements show that the drag coefficient decreases considerably in the laminar and transition regions. This is most likely caused by particle orientation, realignment and rearrangement in particles’ packing position.A thorough hydraulic analysis shows that up-flow filtration in rapid sand filters under backwash conditions causes the particle bed to collapse almost imperceptibly. In addition, an improved expression of the drag coefficient demonstrated that the Carman–Kozeny model constant, however often assumed to be constant, is in fact not constant for increasing flow rates. Furthermore, we propose a new pseudo-3D image analysis for particles with an irregular shape. In this way, we can explain the successful method using optimisation of the extended terminal sub-fluidisation wash (ETSW) filter backwashing procedure, in which turbidity and peaks in the number of particles are reduced with a positive effect on water quality.

Advanced technologies to remove organic micropollutants (OMPs) from municipal wastewater have gained much attention over the last decades. Adsorption by zeolites is one of these technologies. In this study, the regeneration performance of well-tailored granular zeolites loaded with OMPs was evaluated. The selected OMPs were categorized into three groups due to the adsorption performance: high, medium and low adsorbance. Gaseous ozone was directly applied to regenerate dried zeolite granules at an ozone concentration of 30 mg/L and a gas flow rate of 0.2 L/min (0.04 m/s). For the high and medium adsorbing OMPs, 45 min of ozonation was long enough to fully restore their adsorption capacity. For the low adsorbing OMPs, the regeneration efficiency reached 60% after 60 min of ozonation. Interestingly, their recovered adsorption capacities firstly decreased and subsequently increased along with the ozonation duration. The dramatically decrease was most probably due to the presence of the transformation products generated from the ozonation of some selected OMPs. In seven sequential adsorption-regeneration cycles, the adsorption capacity for 75% of the selected OMPs was fully recovered at an ozonation duration of 60 min in each regeneration. The assumed accumulation of the ozonation transformation products only influenced the adsorption of low adsorbing OMPs in 7 cycles.

The fossil-based energy system is transitioning towards a renewable energy system. One important aspect is the spatial and temporal mismatch between intermitted supply and continuous demand. To ensure a reliable and affordable energy system, we propose an integrated system approach that integrates electricity production, mobility, heating of buildings and water management with a major role for storage and conversion. The minimization of energy transport in such an integrated system indicates the need for local optimization. This study focuses on a comparison between different novel system designs for neighborhood energy and water systems with varying modes of system integration, including all-electric, power-to-heat and power-to-hydrogen. A simulation model is developed to determine the energy and water balance and carry out economic analysis to calculate the system costs of various scenarios. We show that system costs are the lowest in a scenario that combines a hydrogen boiler and heat pumps for household heating, or a power-to-X system that combines power-to-heat, seasonal heat storage, and power-to-hydrogen (2070 €/household/year). Scenarios with electricity as the main energy carrier have higher retrofitting costs for buildings (insulation + heat pump), which leads to higher system costs (2320–2370 €/household/year) than more integrated systems. We conclude that diversification in energy carriers can contribute to a smooth transition of existing residential areas.

Drinking water distribution systems (DWDSs) have been thoroughly studied, but the concept of thermal energy recovery from DWDSs is very new and has been conceptualized in the past few years. Cold recovery results in a temperature increase of the drinking water. Its effects on drinking water quality and biofilm development are unclear. Hence, we studied both bulk water and biofilm phases for 232 days in two parallel pilot scale distribution systems with two temperature settings after cold recovery, 25 °C and 30 °C, and compared these with a reference pilot system without cold recovery. In all three pilot distributions systems (DSs) our results showed an initial increase in biomass (ATP) in the biofilm phase, along with occurrence of primary colonizers (Betaproteobacteriales) and subsequently a decrease in biomass and an increasing relative abundance of other microbial groups (amoeba resisting groups; Xanthobacteraceae, Legionellales), including those responsible for EPS formation in biofilms (Sphingomonadaceae). The timeline for biofilm microbial development was different for the three pilot DSs: the higher the temperature, the faster the development took place. With respect to the water phase within the three pilot DSs, major microbial contributions came from the feed water (17–100%) and unkown sources (2–80%). Random contributions of biofilm (0–70%) were seen between day 7–77. During this time period six-fold higher ATP concentration (7–11 ng/l) and two-fold higher numbers of high nucleic acid cells (5.20–5.80 × 104 cells/ml) were also observed in the effluent water from all three pilot DSs, compared to the feed water. At the end of the experimental period the microbial composition of effluent water from three pilot DSs revealed no differences, except the presence of a biofilm related microbial group (Sphingomonadaceae), within all three DSs compared to the feed water. In the biofilm phase higher temperatures initiated the growth of primary colonizing bacteria but this did not lead to differences in microbial diversity and composition at the end of the experimental period. Hence, we propose that the microbiological water quality of DWDSs with cold recovery should be monitored more frequently during the first 2–3 months of operation.

De drinkwaterbedrijven hebben samen met KWR, HWL en RIVM onderzoek gedaan naar microplastics in water. De resultaten werden onlangs op een workshop gepresenteerd, waarbij werd ingegaan op de oorsprong van microplastics in water, analyse en karakterisering van microplastics en wat ermee gebeurt tijdens het drinkwaterzuiveringsproces. Op dit moment bevat kraanwater nog vrijwel geen meetbare microplastics, maar meer onderzoek is nodig om te kijken of dit zo kan blijven.

The high chlorine dosages in wastewater treatment plants during the COVID-19 pandemic may result in increased formation of disinfection by-products (DBPs), posing great threat to the aquatic ecosystem of the receiving water body and the public health in the downstream area. However, limited information is available on the effect of biological wastewater treatment processes on the formation of CX3R-type DBPs. This study investigated the effect of oxidation ditch (OD) and anaerobic-anoxic-oxic (AAO), two widely used biological wastewater treatment processes, on the formation of five classes of CX3R-type DBPs, including trihalomethanes (THMs), haloacetic acids (HAAs), haloacetaldehydes (HALs), haloacetonitriles (HANs) and halonitromethanes (HNMs), during chlorination. Experimental results showed that biological treatment effectively reduced the dissolved organic carbon (DOC) and UV254, while it increased the dissolved organic nitrogen (DON), and therefore the ratio of DON/DOC. In addition, increases in the contents of soluble microbial product- and humic acid-like matters, and the transformation of high molecular weight (MW) fractions in the dissolved organic matter into low MW fractions were observed after OD and AAO processes. Although biological treatment effectively decreased the formation of Cl-THMs, Cl-HAAs, Cl-HANs and Cl-HNMs, the formation of DBCM, DBAA, BDCAA, DBCAA, DCAL, TCAL and DBAN (where C = chloro, B = bromo, D = di, T = tri) all increased significantly, due to the increased formation reactivity. Moreover, biological treatment increased the ratio of bromide/DOC and bromine incorporation into THMs, HAAs and DHANs except for HALs and THANs. Different from previous studies, this study revealed that biological treatment increased the formation of some DBPs, especially brominated DBPs, despite the efficient removal of organic matters. It provides insights into the DBP risk control in wastewater treatment, particularly during the COVID-19 pandemic.

Degradation of tetracycline (TTC) with a heterogeneous Fenton-like pyrite/H2O2 process by pyrite from mine waste as a mineral catalyst was investigated. The study focused on identifying the main oxidizing agents and degradation mechanisms along with operational variables including solution pH, pyrite and H2O2 concentration, contact time, solution temperature, and initial TTC concentration. Catalyst characterization tests revealed that pyrite is a mesoporous powder with a high degree of FeS2 purity. Radical scavenger tests demonstrated that •OH was the main oxidizing agent generated by both solution and surface phase reactions. During the pyrite/H2O2 process, more than 85% of TTC was mineralized in 60 min and the maximum TTC removal was attained in the solution at an acidic pH value (4.1). The most abundant transformation products of TTC, formed by the attack of •OH radicals, were simple chain carboxylic acids. Cultured cells of human embryonic kidney (HEK) were used for the cytotoxicity assessment of raw and pyrite/H2O2 treated TTC solutions. The results illustrated that the viability of HEK cells was enhanced considerably after treating TTC solutions under optimal conditions. Accordingly, pyrite originating from mine waste is a practically effective and cost-effective catalyst in heterogeneous Fenton-like systems for mineralization and degradation of emerging contaminants such as antibiotics.

The high chlorine dosages in wastewater treatment plants during the COVID-19 pandemic may result in increased formation of disinfection by-products (DBPs), posing great threat to the aquatic ecosystem of the receiving water body and the public health in the downstream area. However, limited information is available on the effect of biological wastewater treatment processes on the formation of CX

A novel sol-gel method was employed in this study to efficiently synthesize SnO

Continuous development of industry and civilization has led to changes in composition, texture and toxicity of waste water due to the wide range of pollutants being present. Considering that the conventional wastewater treatment methods are insufficient for removing micropollutants and nutrients to a high level, other, alternative, treatment methods should be used to polish wastewater treatment plant effluents. In this study we developed an alternative, polishing concept for removal of ammonium and micropollutants that could potentially be incorporated in existing wastewater treatment plants. We demonstrated a method to use high silica MOR zeolite granules as an adsorbent for simultaneous removal of the micropollutant sulfamethoxazole (SMX) and ammonium (NH4+) ions from aqueous solutions. At an initial NH4+ concentration of 10 mg/L the high silica zeolite mordenite (MOR) granules removed 0.42 mg/g of NH4+, similar to the removal obtained by commonly used natural zeolite Zeolita (0.44 mg/g). However, at higher NH4+ concentrations the Zeolita performed better. In addition, the Langmuir isotherm model showed a higher maximum adsorption capacity of Zeolita (qmax, 4.08 mg/g), which was about two times higher than that of MOR (2.11). The adsorption capacity of MOR towards SMX, at both low (2 µg/L) and high (50 mg/L) initial concentrations, was high and even increased in the presence of NH4+ ions. The used adsorbent could be regenerated with ozone and reused in consecutive adsorption–regeneration cycles with marginal decrease in the total adsorption capacity.

The influence of stochastic water demand on model-based leak localizationGlobally, water demand is rising and resources are diminishing. In the context of climate change and a growing world population, a further increase in water scarcity seems inevitable. Aiming towards a sustainable future, water should be used as efficient as possible by minimizing water losses, which can be higher than 50% in some drinking water networks.3 To minimize losses it is crucial to detect, localize and repair leaks as soon as possible.Leaks cause changes in flow and pressure. By monitoring the network with pressure and flow sensors and coupling these measurements with hydraulic computer models, leaks can be detected and located. The success of this so-called model-based leak localization depends heavily on our knowledge of water demand, since every water consumption affects the pressure and flow in the network as well. Nowadays, demand is modelled based on water billing information and the network’s inflow. This study proposes a new strategy by modelling stochastic demands. Realistic residential demands are generated in high spatial and temporal resolution based on Dutch water use statistics with SIMDEUM4. Subsequently, the stochastic demands are used within hydraulic simulations. The influence of demand fluctuations on pressure in the system is analyzed using Monte-Carlo sampling and the corresponding effects on model-based leak detection and localization are investigated.The proposed method is applied on a real Dutch water distribution network, containing inflow and six pressure measurements. Statistical information like the number of residents, households and annual billing information in the area is known. The corresponding hydraulic model is calibrated on pipe roughness by minimizing the mean squared error of the modelled and measured pressure at the sensor locations. Pressure driven simulations are performed and the resulting pressure changes at the sensors are simulated. Through the stochastic simulations in combination with Monte-Carlo sampling, confidence intervals for pressure changes at the sensor locations are determined and compared with the real measurements. The performance of leak detectability and localization is subsequently examined. This study shows that stochastic water demand simulations provide a better understanding on the reliability of model-based leak localization. By using these simulations, confidence intervals of demand related pressure changes at the sensor locations can be determined which affect the performance of leak detectability and localization under the variability of water demand. A better grip on the reliability of leak localization yields in a more efficient quest for leaks. 3EurEau 2017, Europe’s water in figures, an overview of European drinking water and waste water sectors, The European Federation of National Associations of Water Services4Blokker, E. J. M. (2010), Stochastic water demand modelling for a better understanding of hydraulics in water distribution networks, PhD thesis, Delft University of Technology

Greenhouse gas (GHG) emissions contribute to climate change. The public water utility of Amsterdam wants to operate climate neutrally in 2020 to reduce its GHG emissions. Energy recovery from the water cycle has a large potential to contribute to this goal: the recovered energy is an alternative for fossil fuel and thus contributes to the reduction of GHG emissions. One of the options concerns thermal energy recovery from drinking water. In Amsterdam, drinking water is produced from surface water, resulting in high drinking water temperatures in summer and low drinking water temperatures in winter. This makes it possible to apply both cold recovery and heat recovery from drinking water. For a specific case, the effects of cold recovery from drinking water were analyzed on three decisive criteria: the effect on the GHG emissions, the financial implications, and the effect on the microbiological drinking water quality. It is shown that cold recovery from drinking water results in a 90% reduction of GHG emissions, and that it has a positive financial business case: Total Cost of Ownership reduced with 17%. The microbial drinking water quality is not affected, but biofilm formation in the drinking water pipes increased after cold recovery.

Large quantities of natural and synthetic hormones contained in livestock waste and wastewater (LWW) can cause serious problems in our environment. Composting and anaerobic digestion cannot remove hormones efficiently, so they should be modified to enhance the treatment processes. In addition, constructed wetlands show decent rates for removal of hormones. Advanced technologies such as membrane biological reactors and microalgae-based systems efficiently eliminate hormones from LWW. However, more practical studies are needed to investigate their actual performances. The categories, degradation mechanisms, and enzymes of hormone-degrading microorganisms are presented, and related hormone-degrading microorganism-based technologies are introduced. Finally, composting, anaerobic digestion, constructed wetlands, membrane biological reactors, and microalgae-based systems are compared in terms of their applicability in LWW treatment.

Reverse osmosis (RO) is the most promising membrane technology in organic micropollutants (MPs) removal of drinking water treatment. For 78 MPs, passage and removal were evaluated with an ESPA3 RO membrane and the robustness of RO against MPs was studied. The MPs were classified according to their charge and hydrophobicity. The results showed that the size of neutral compounds was negatively correlated with their passage. This correlation was weaker for neutral hydrophobic MPs than neutral hydrophilic MPs. The lowest passage (0.2%–4%) was displayed by anionic MPs because of electrostatic repulsion between the negatively charged solute and negatively charged membrane surface. Cationic MPs showed a higher passage (around 0.4%–40%) due to electrostatic sorption and Donnan exclusion. The relationship between physical-chemical properties of MPs and their passage was evaluated by the one-way analysis of variance (ANOVA). We performed a qualitative analysis of variables using Principal Component Analysis (PCA) in order to examine the physical-chemical properties of compounds that affect the membrane removal of MPs. After analysis with Multiple Linear Regression (MLR), we concluded that properties such as molecular width, equivalent molecular width, pKa and solubility can be considered as significant descriptors for prediction of the membrane removal. The influence of feed water temperature on MPs passage was also assessed. The results revealed that a rise of water temperature from 5 to 19 °C, increases the average passage of MPs by 6.5%.

H2O2 residuals from advanced oxidation processes (AOPs) may have critical impacts on the microbial ecology and performance of subsequent biological treatment processes, but little is known. The objective of this study was to evaluate how H2O2 residuals influence sand systems with an emphasis on dissolved organic carbon (DOC) removal, microbial activity change and bacterial community evolution. The results from laboratory batch studies showed that 0.25 mg/L H2O2 lowered DOC removal by 10% while higher H2O2 concentrations at 3 and 5 mg/L promoted DOC removal by 8% and 28%. A H2O2 dosage of 0.25 mg/L did not impact microbial activity (as measured by ATP) while high H2O2 dosages, 1, 3 and 5 mg/L, resulted in reduced microbial activity of 23%, 37% and 37% respectively. Therefore, DOC removal was promoted by the increase of H2O2 dosage while microbial activity was reduced. The pyrosequencing results illustrated that bacterial communities were dominated by Proteobacteria. The presence of H2O2 showed clear influence on the diversity and composition of bacterial communities, which became more diverse under 0.25 mg/L H2O2 but conversely less diverse when the dosage increased to 5 mg/L H2O2. Anaerobic bacteria were found to be most sensitive to H2O2 as their growth in batch reactors was limited by both 0.25 and 5 mg/L H2O2 (17–88% reduction). In conclusion, special attention should be given to effects of AOPs residuals on microbial ecology before introducing AOPs as a pre-treatment to biological (sand) processes. Additionally, the guideline on the maximum allowable H2O2 concentration should be properly evaluated.