Influence of rubber particle inputs on nitrogen removal efficiency of bioretention systems
Bioretention systems effectively capture rubber particles and other microplastics in stormwater runoff. However, it is uncertain whether long-term particle accumulation affects pollutant removal efficacy. This study investigated the impact of various concentrations of ethylene-propylene-diene-monomer (EPDM) particles (0, 50, 100, and 400 mg/L) on bioretention system nitrogen removal performance. The input of EPDM during short-duration (2 h) rainfall favored the removal of nitrogen, and the total nitrogen effluent concentration of the bioretention system with EPDM was reduced by 0.59-1.52 mg/L compared with that of the system without EPDM. In addition, the input of EPDM reduced the negative effects of drought. During long-duration (24 h) rainfall, higher concentrations of EPDM led to lower nitrate-nitrogen concentrations in the effluent. The bioretention system with EPDM required less time for nitrate-nitrogen removal to reach 50% than that without EPDM input. Microbial community analysis showed that EPDM increased the relative total abundance of denitrifying bacteria (such as , , , and ) by 7.25-10.26%, which improved the denitrification capacity of the system.
A new strategy for greenhouse gas emission reduction in the anaerobic/anoxic/oxic biological treatment process using exogenous N-acyl-homoserine lactones, a quorum-sensing signaling molecules
In this study, the impact of exogenous N-acyl-homoserine lactones (AHLs) on greenhouse gas (GHG) emissions in anaerobic/anoxic/oxic (A/A/O) systems was analyzed by manipulating the type and dosage of AHLs. The mechanism behind AHLs' effects on GHG emissions was explored through changes in microbial community structure. Findings revealed that N-octanoyl-homoserine lactone (C8-HSL) and high-dose N-dodecanoyl-homoserine lactone (C12-HSL) increased GHG emissions, while low-dose C12-HSL decreased them. Moreover, C8-HSL and high-dose C12-HSL promoted methane (CH) and nitrous oxide (NO) production by affecting sludge particle size. Bacterial community analysis highlighted and 's roles in NO emissions and acetate methanogens in methane synthesis. Metabolic pathway analysis showed that the acetic acid (CHCOOH) methanogenic pathway was the main methanogenic pathway; C8-HSL and C12-HSL influenced methane emission by affecting the methanogenic pathway and NO emission by changing nitrous oxide reductase () abundance. This research underscores AHL-based quorum sensing's potential in mitigating GHG emissions during activated sludge wastewater treatment, offering insights into their application and impact on key microbial activities. Limitations include the absence of methane emission reduction by signaling molecules and the need for further investigation into their effects on sludge accumulation.
A combined support vector regression with a firefly algorithm for prediction of energy consumption in wastewater treatment plants
Wastewater treatment plants (WWTPs) comprise energy-intensive processes, serving as primary contributors to overall WWTP costs. This research study proposes a novel approach that integrates support vector regression (SVR) with the firefly algorithm (FFA) for the prediction of energy consumption in a WWTP in Chlef City, Algeria. The database comprises a comprehensive set of 1,653 samples, capturing diverse information categories. It includes chemical and physical characteristics, encompassing chemical oxygen demand, 5-day biochemical oxygen demand, potential of hydrogen, water temperature, total suspended sediment in water and basin, influent N-NH concentration, number of aerators, and operating time. Additionally, the hydraulic and energy-related parameters are represented by the flow entered at the station and the energy consumed by aerators, respectively. Finally, meteorological data, comprising rainfall, temperature, relative humidity, and the aridity index, are part of the dataset required for analysis. In this regard, 15 different models that correspond to 15 different combinations of input parameters are assessed in this study. The results show that the SVR-FFA-15 can render an improvement in the prediction accuracy of energy consumption in WWTPs. This study provides a useful tool for managing the energy consumption of wastewater treatment and makes insightful recommendations for future energy savings.
Navigating the definition of urban flooding: A conceptual and systematic review of the literature
Urban flooding is a pervasive global risk, posing a great challenge to urban planners, policymakers, and particularly communities. This paper reviews the literature to analyze how urban flooding is defined across scientific disciplines. Our objectives are to uncover the elements used to define urban flooding and evaluate how these elements can impact future research and practice. A key difficulty is the lack of a consistent, comprehensive definition that captures both physical and social dimensions of urban flooding. Current definitions often focus solely on physical aspects (e.g., rainfall, infrastructure) or social impacts, rarely integrating both. This fragmentation hinders effective flood risk management and interdisciplinary collaboration. Our contribution is a multifaceted definition incorporating spatial and social concerns, including water origins, built environment characteristics, and local community aspects. We introduce the 'Urban Water Transect' concept to illustrate the continuum of flood risk across urban zones, addressing a gap in the literature. The analysis reveals that many papers discuss flooding causes without providing an explicit definition. Urban flooding is predominantly defined based on water source, imperviousness, and drainage infrastructure. Future research should adopt an interdisciplinary perspective considering both physical and social aspects, potentially transforming urban flood risk management.
Flocculation of for successful harvesting and potential use
This study includes cultivation in artificial saline medium (ASM). With the aim of harvesting the bulk biomass, an experiment was set up at a bench scale to evaluate the best flocculation technique with the least compromising biomass and lipid loss. The flocculation efficiencies for the biomass have been studied using the auto-, bio-, and chemical-flocculation methods. Different concentrations of chitosan for the biological method and alum for the chemical method were added in culture growing in the liquid ASM. The optimal concentration with the highest biomass and oil collection was determined for each method. In the biological method, the highest (96.44%) and lowest (67.88%) flocculation efficiencies were observed by adding 15 and 2 mg of chitosan, respectively, and in the chemical method, the highest (97.2%) and lowest (35.4%) flocculation efficiencies were observed by adding 150 and 50 mg of alum, respectively. The auto-flocculation method shows the highest efficiency (97.8%) among all the tests. The oil yield from the three highest biomasses was 2.60, 1.51, and 1.08% in the auto-, bio-, and chemical-flocculation methods, respectively. The time taken for auto-, bio-, and chemical-flocculation was 48, 4, and 1 h, respectively.
Comparative life cycle assessment of on-site sanitation systems using lagoons or drying beds for fecal sludge treatment in low-income tropical countries
Environmental challenges in low-income countries, such as Haiti, persist due to inadequate sanitation infrastructure. This study assesses the environmental impacts of nine on-site sanitation systems to identify those with the least environmental impacts and explore improvement options. Nine scenarios were developed, each representing different systems for managing 1 ton of fecal sludge over 1 year. The 'Impact World + ' and 'IPCC 2013 GWP 100a' methods evaluated impacts on ecosystems, human health, and climate change. Data sources included interviews, weighing records, and scientific publications. Results show that Scenario 8 (Flush Toilet - Evacuation - Planted Drying Beds) is most impactful on health (1.17 × 10 DALY), while Scenario 1 (Composting Toilet - Evacuation - Unplanted Drying Beds) is least impactful (1.77 × 10 DALY). For ecosystem impacts, Scenario 2 (Container-based Toilet - Evacuation - Planted Drying Beds) is most impactful (3.81 × 10 PDF·m·year), while Scenario 6 (VIP latrine - Evacuation - Lagoons) is least impactful (3.52 × 10 PDF·m·year). Key hotspots include toilet paper, wood shavings, GHG emissions, and water use. The study recommends an integrated approach combining environmental life cycle assessment (LCA) with life cycle cost assessment and social LCA for sustainable decision-making on sanitation systems in low-income countries.
A novel approach for multivariate time series interval prediction of water quality at wastewater treatment plants
This study proposes a novel approach for predicting variations in water quality at wastewater treatment plants (WWTPs), which is crucial for optimizing process management and pollution control. The model combines convolutional bi-directional gated recursive units (CBGRUs) with adaptive bandwidth kernel function density estimation (ABKDE) to address the challenge of multivariate time series interval prediction of WWTP water quality. Initially, wavelet transform (WT) was employed to smooth the water quality data, reducing noise and fluctuations. Linear correlation coefficient (CC) and non-linear mutual information (MI) techniques were then utilized to select input variables. The CBGRU model was applied to capture temporal correlations in the time series, integrating the Multiple Heads of Attention (MHA) mechanism to enhance the model's ability to comprehend complex relationships within the data. ABKDE was employed, supplemented by bootstrap to establish upper and lower bounds of the prediction intervals. Ablation experiments and comparative analyses with benchmark models confirmed the superior performance of the model in point prediction, interval prediction, the analysis of forecast period, and fluctuation detection for water quality data. Also, this study verifies the model's broad applicability and robustness to anomalous data. This study contributes significantly to improved effluent treatment efficiency and water quality control in WWTPs.
Microbe-plant-nanoparticle interactions: role in bioremediation of petroleum hydrocarbons
Petroleum hydrocarbons (PHCs) are organic substances that occur naturally on earth. PHCs have emerged as one of the most prevalent and detrimental contaminants in regions comprising soil and water resources. The limitations of conventional physicochemical and biological remediation solutions could be solved by combining remediation techniques. An effective, affordable, and environmentally benign method of reducing petroleum toxins is provided by the advanced idea of bioremediation, which has evolved into nanobioremediation. Environments contaminated with PHCs have been restored through microbe-plant-nanoparticle (NP)-mediated remediation, this review emphasizes how various metallic NPs interact with microbes and plants changing both their activity and that of enzymes, therefore accelerating the remediation process. This work further examines the challenges and possible uses of nanobioremediation, as well as the application of novel technologies in the interactions between bacteria, plants, and NPs for the bioremediation of PHCs. Furthermore, it has been shown that the use of plant-based, microbe-based, microbe-plant-based, and microbe-plant-NP-based techniques to remediate contaminated soils or water bodies is economical and environmentally beneficial. Microbial consortia have been reported as the treasure houses for the cleaning and recovery of hydrocarbon-contaminated environments, and the development of technologies for bioremediation requires an understanding of hydrocarbon degradation mechanisms.
Composition and concentrations of microplastics including tyre wear particles in stormwater retention pond sediments
Stormwater is recognised as a vector for microplastics (MPs), including tyre wear particles (TWPs) from land-based sources to receiving waterbodies. Before reaching the waterbodies, the stormwater may be treated. In this study, sediments from six treatment facilities (five retention ponds and a subsurface sedimentation tank) were analysed to understand MP occurrence, concentrations, sizes, polymer types and distribution between inlet and outlet. The concentrations of MPs showed large variations between and within different facilities with MP concentrations of 1,440-72,209 items/kg (analysed by μFTIR) corresponding to 120-2,950 μg/kg and TWP concentrations from
Developing a universal equation to estimate the mass of dewatered wastewater sludge during biological digestion at mesophilic and thermophilic temperatures
A series of dewaterability tests were conducted on various types of sludges to establish a wholistic relationship between sludge water fractions. Sludge samples were obtained from batch and continuous sludge digesters, which were operated anaerobically and aerobically under mesophilic and thermophilic conditions. Dewaterability of the sludge samples and the distribution of water fractions were studied using centrifugation and thermal drying. Thickened waste activated sludge (T-WAS) contained 10-11 g bound water (BW)/g of total solids (TS), and it was more hydrophilic than primary and digested sludges. During anaerobic digestion, BW content fluctuated between 3.2 and 4.2 g BW/g TS. However, aerobic digestion at 55°C reduced the BW content of the mixed T-WAS + primary sludges from 3.7 to 2.1 g BW/g TS. A linear function was developed to correlate supernatant and BW mass fractions (R = 0.995). An equation was derived from the linear function to estimate the mass of dewatered sludge based on the TS concentration of the initial wet sludge. The developed expression is applicable to different kinds of wastewater sludges. Such an expression would be helpful for the designers and operators of sludge thickening and dewatering systems that use centrifugal separation.
Kinetic study of mineral oil removal from wastewater by the sono-electrochemical process
Chemical kinetics can be a useful tool for determining the optimal operating time of electrochemical processes. The main objective of the study was to determine the mineral oil removal rate by sono-electrochemical treatment. In this study, zero-, first-, and second-order kinetic models were used to determine the reaction rate of mineral oil removal with the sono-electrochemical process. The reaction rate experiments were conducted under the following optimal conditions: 8 min of treatment time, a current density of 53.1 A/m, and a flow rate of 0.23 L/s. It was found that the changes in mineral oil concentrations follow second-order kinetics with a coefficient of determination of 0.9732. The mineral oil removal efficiency was 94.4%. This study concludes that sono-electrochemical process could be a promising technology for the removal of mineral oil from wastewater, and that the mineral oil removal rate can be determined by chemical kinetics. The results obtained may be useful for the optimization of the sono-EC process and reactor design.
Phytomediated synthesis of WO nanoparticles using fruit extract for enhanced photocatalytic activity of 2,4-dichlorophenol
In the present study, bio-citric acid/tungsten oxide (WO) (BCAWO) nanoparticles (NPs) were prepared by using fruit extract as a reducing as well as a capping agent. The photocatalysts were characterized by UV-vis diffuse reflectance spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), high-resolution transmission electron microscopy, and photoluminescence spectroscopy techniques. Diffraction peaks in the XRD spectrum were identified as the crystal planes of crystalline tungsten oxide. The BCAWO had an average size of 23.14 nm. For W-O bonds, the Fourier transform infrared spectrum displays the vibrational peak at 671.23 cm. A prominent absorption band was observed at 268 nm, indicating the 1.2 eV bandgap. Under xenon (Xe) lamp irradiation, the synthesized BCAWO nanoparticles showed notable photocatalytic degradation of 2,4-dichlorophenol (2,4-DCP), with a degradation rate of 96%. With BCAWO concentrations of 2.5 g/L, pH of 4, reaction period of 180 min, and 2,4 DCP concentration of 10 mg/L, the degradation of 2,4-DCP had the highest efficacy, 96%. The degradation of phenols in wastewater may be facilitated by using the green WO nanoparticles as a photocatalyst, according to the results.
Decision support tools for water reuse: a systematic review
This article provides a comprehensive review of decision support tools for water reuse (DST4WR), focusing on microbiological risk assessment (MRA), life cycle analysis (LCA), life cycle cost (LCC), and multi-criteria decision analysis (MCDA). A systematic review of 35 articles published between 2020 and 2024, plus one from 2019, was conducted. The studies were categorised based on the DST4WR applied, with each tool discussed individually. MRA tools assess public health risks in different case studies. LCA identifies key environmental indicators, and its integration with LCC facilitates comprehensive cost analysis. MCDA, applied in various case studies, uses criteria like environmental, social, economic, technical, public health, and functional aspects. Integrating DST4WR tools identifies synergies and trade-offs between criteria, aiding informed decision-making. Combining MRA, LCA/LCC, and MCDA is especially beneficial, as each tool provides a distinct perspective. Using these tools together offers a holistic view of water reuse management, ensuring that all relevant factors are balanced. This approach enhances decision-making and builds stakeholder confidence and acceptance by transparently addressing public health, environmental, economic, and social concerns.
Comparison of reference libraries for the detection of tire-derived microplastics (TMPs)
Introducing microplastics (MPs) into the marine environment is a global problem. Tire-derived microplastics (TMPs) are estimated to account for 60% of all secondary MPs dispersed in aquatic environments. To effectively detect TMPs in environmental samples using micro-Fourier transform infrared (μFTIR) spectroscopy, a high-quality reference library is essential. However, the use of conventional diamond crystals in FTIR presents challenges for the detection of materials containing carbon black, such as rubber and tires. In addition, there is a discrepancy between spectra from standard libraries and spectra from environmental samples, which makes detection difficult. In order to overcome these problems in the detection of TMPs by μFTIR, we developed four reference libraries to improve the detection, and 'The 26 tire wear library' was found to be the best among these four. Furthermore, a comparison of these new libraries revealed the following requirements to improve TMP detection: (i) the reference spectra must be acquired under the same setup used for material observation including prism material, (ii) tires, not rubber, must be used as reference materials, and (iii) tire wear samples must be prepared to replicate the actual generation conditions on roads.
Effects of copper and lead on the sorption and desorption behaviors of benzene onto humic acids and black carbons
Due to rapid urbanization and industrialization, combined pollution caused by BTEX (benzene, toluene, ethylbenzene, and xylene) and heavy metals has become ubiquitous in soils, which would pose serious health risks to humans. However, the effects of heavy metals on the sorption and desorption behaviors of BTEX have not been fully elucidated. In this study, the effects of Cu and Pb ions on the sorption and desorption of benzene onto humic acids and black carbons were investigated. The results showed that Cu and Pb ions significantly reduced the sorption capacity, slowed down the sorption rate, and made the desorption less hysteretic of benzene on both humic acids and black carbons. Furthermore, the inhibitory effects by Pb were significantly stronger than those of Cu. By combining the results of Fourier transform infrared spectroscopy and the site energy distribution model, it can be speculated that the hydration shells of Cu and Pb ions partially cover the surface of humic acids and black carbons, blocking their micropores and shielding sorption sites, consequently inhibiting the sorption of benzene. This study highlights that coexisting metal cations can significantly influence the fate of BTEX in soils.
Degradation of tetracycline by heat/peroxymonosulfate and ultrasound/peroxymonosulfate systems: performance and kinetics
In recent decades, water pollution caused by emerging contaminants such as pharmaceuticals, has attracted much attention. Antibiotics are commonly used pharmaceuticals, and their residue in water may accelerate the development of antibiotic resistance genes, which can produce resistance to the treatment of diseases. In this study, two energy-based systems, heat/peroxymonosulfate (PMS) and ultrasound (US)/PMS were chosen to treat the typical antibiotic tetracycline (TC) in water. The influencing factors and kinetic equations of TC degradation by heat/PMS and US/PMS were investigated and the rates of TC degradation by the two systems were compared. The results showed that the optimal PMS concentration required for TC degradation in both systems was 0.3 mM, and neither system was affected by solution pH. The power of the US in the US/PMS system was as important as the temperature in the heat/PMS system because they provided activation energy. Both heat and US could activate PMS to degrade TC, and US was slightly superior with 80% TC removal under the conditions of [TC] = 20 mg/L, [PMS] = 0.3 mM, pH = 6.4, T = 20 °C, and US power = 550 W. US is considered to be more advantageous in activating PMS to degrade TC.
Optimization of the integrated green-gray-blue system to deal with urban flood under multi-objective decision-making
The integrated green-gray-blue (IGGB) system is considered to be a new way of stormwater management, and a comprehensive evaluation of the green-gray-blue infrastructure layout mode under different return periods is the key to the implementation decision-making of stormwater management. In this study, a blue-green synergism evaluation model is established to optimize the layout of blue-green infrastructure. An evaluation framework combining the evaluation indicator system and the hydrology model is established. Stormwater storage, peak flow reduction, and life cycle cost are selected as evaluation indicators. On this basis, seven optimal scenarios, including green, blue, gray, green-blue, green-gray, blue-gray, and green-gray-blue, are established. The Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method is used to analyze these seven scenarios under different return periods. The results indicate that (1) when the drainage infrastructures are arranged in combination, the peak flow reduction is significantly improved compared to that of a single drainage. (2) TOPSIS results show that green-gray and blue-gray perform better when the cost weight is 0-0.35, and green-gray-blue performs best when the cost weight is 0.35-1. (3) The integrated green-gray-blue system has obvious synergistic effects. This study can provide support for planning department workers for the urban stormwater management strategy.
Evaluation of pretreatment routes for seawater desalination by nanofiltration
Nanofiltration (NF) has been used as the default sulfate removal process in platforms to treat seawater for water flooding. Seawater is generally pretreated by chlorination and cartridge filters to reduce fouling of the membranes; however, this pretreatment is insufficient to provide water quality high enough to maintain the productivity of the NF membranes. In this study, the performances of two different pretreatment routes were evaluated. Microfiltration (MF) was evaluated as a replacement for cartridge filters, and the advanced oxidation process UV/HO was evaluated as an additional stage of pretreatment upstream of the cartridge filters. The permeability of the NF membranes after 12 h of seawater sulfate removal in a bench system was 4.4 L·h·m·bar when the UV/HO process was adopted as the pretreatment and 2.9 L·h·m·bar when the MF process was adopted, compared to 1.6 L·h·m·bar achieved for the pretreatment with the cartridge filter alone. These results indicate that NF membrane fouling was significantly higher when seawater was pretreated only by the cartridge filter in comparison to both proposed pretreatments. An economic analysis showed that both systems are economically viable and can potentially reduce the operational costs of the NF sulfate removal process on platforms.
Source reduction and end treatment of acid mine drainage in closed coal mines of the Yudong River Basin
After the closure of the Yudong coal mine, the pH value was approximately 3.0, and the Fe and Mn concentrations reached 380 and 69 mg/L, respectively, in the acid mine drainage (AMD), causing serious pollution to the water bodies in the nearby watershed. Combined with the formation conditions of AMD, the comprehensive treatment technology of source reduction-end treatment is adopted to treat the AMD. The treatment area of the goaf is 0.3 km, the filling and grouting volume is about 6.7 m, and the curtain grouting volume is 4,000 m. Through the grouting and sealing treatment in the goaf, the water volume is reduced to less than 85% of the initial volume (100 m/h). After the end treatment, the pH value of the effluent is around 7.0, the content of Fe and Mn is less than 0.1 mg/L, and the removal rate is above 99%. The project was subsequently operated at RMB 0.85 yuan/t. This project is aimed at the treatment of AMD from small coal mines in complex terrain conditions. It has the characteristics of low cost and high efficiency and can provide an effective treatment technology for AMD in southwestern China and areas with the same geological conditions.
A fuzzy TOPSIS-based approach for prioritizing low-impact development methods in high-density residential areas
The study successfully implemented six low-impact development (LID) methods to manage surface runoff in urban areas: green roof, infiltration trench, bio retention cell, rain barrel, green roof combined with infiltration trench, and rain barrel combined with bio-retention cell. Each method has unique benefits in mitigating surface runoff effects in urban environments. The following four indicators were used to evaluate the methods: runoff volume reduction, peak runoff flow rate reduction, economic sustainability, and social sustainability. The study, which lasted approximately 4 months, was conducted in an eastern Tehran metropolis residential area with a mix of old and new buildings. The SWMM model determined runoff volume and peak flow values, and a price analysis list determined the economic index. Local experts completed 25 questionnaires to evaluate the social index. Fuzzy TOPSIS multi-indicator decision criteria were used to prioritize LID methods, and the Rain barrel + Bio retention cell combined scenario emerged as the best option based on all four criteria. The method reduced peak runoff flow by 23.1-66.1% under rainfall with 10-year return periods. The green roof + infiltration trench method had the highest percentage reduction of 2,737 m, while the infiltration trench had the lowest reduction of 273 m.
Erratum: Water Science & Technology 86 (9), 2071-2088: Evaluation and sizing of proprietary sedimentation devices for decentralised stormwater treatment, Sam Houlker, Alexander Pasing and Moritz Gesterding, https://dx.doi.org/10.2166/wst.2022.342
