Wastewater Management Strategies Research Articles

Navigating the nitrogen challenge: Strategies for wastewater management and sustainable resource recovery

Water scarcity and the impact of nitrogen pollution from wastewater have emerged as pressing global concerns. This study delved into the hazards posed by nitrogen pollution, focusing on its sources, composition, and detrimental effects on both the environment and the agricultural sector. The primary research methodology involved a comparative analysis of various nitrogen control and recovery technologies, highlighting the technical effects and future application prospects of ammonia vapor stripping and adsorption nitrogen recovery. Findings revealed that while ammonia vapor stripping offers operational simplicity, it is energy-intensive and requires careful byproduct management. In contrast, adsorption nitrogen recovery provides a more energy-efficient method, though challenges like selectivity in the presence of contaminants persist. The study concludes by suggesting an integrated approach that combines both methods, optimized based on wastewater characteristics, and underscores the importance of byproduct valorization and the development of selective adsorbents. The ultimate goal is to ensure sustainable environmental solutions while maximizing resource optimization.

Elastic, Janus 3D evaporator with arch-shaped design for low-footprint and high-performance solar-driven zero-liquid discharge

Solar-driven zero-liquid discharge (ZLD) is a promising wastewater management strategy for freshwater recovery and solid waste harvesting. However, practical application of the solar-driven ZLD is severely constrained due to its low evaporation efficiency, large footprint, and rapid salt accumulation. Here, we present a Janus arch-shaped solar-driven evaporator (▪) comprising a hydrophobic top photothermal layer for effective light absorption, solar-thermal conversion, and vapor evaporation, which exhibits an evaporation rate of 2.82 kg∙m−2∙h−1 in pure water. The design also includes shapable delignified longitudinal wood (D-L-wood) serving as the hydrophilic bottom water transport layer, which enables dual-directional saltwater transportation and salt crystallization. D-L-wood, with numerous aligned channels, exhibits a low thermal conductivity of 0.04 W·m−1·K−1 along perpendicular direction and can effectively localize heat on the photothermal layer of the evaporator. D-L-wood has excellent hydrophilicity, and the salty water can be transferred quickly along both ends of the wood, providing sufficient salty water for rapid evaporation. The anisotropy of the wood makes the heat transfer quickly along the channel, improving the thermal management ability of the evaporator. Moreover, during vapor evaporation on the hydrophilic-hydrophobic interface, salt is crystallized at the hydrophilic layer, resulting in an enhanced anti-salt performance, a 1.5 folds evaporation rate compared with non-Janus evaporator after 15 h test. Under the conditions of a salt concentration of 3.5 %, a high salt harvest performance of 62.4 g∙m−2∙h−1 can be obtained under AM 1.5 solar irradiation. The arch-shaped design fully utilizes the upper space and effectively reduces evaporator footprint, resulting in an evaporation area to footprint ratio of 1.57:1. The designed evaporator can also be utilized for ZLD treatment of other heavy metal polluted water including Cu2+, CrO42−, Co2+, and so on. Therefore, the Janus-arch-shaped, solar-driven evaporator enables a potentially low-footprint, low-cost, scalable, and practical ZLD strategy for sustainable wastewater treatment.

Integrating the circular economy model into the management and treatment of Fischer–Tropsch effluents—a conversion of waste to energy (biogas) opportunity

AbstractThe Fischer–Tropsch (FT) process converts coal, biomass, or natural gas into liquid hydrocarbons via syngas generation and catalytic conversion. However, FT produces byproducts and effluents with substantial environmental consequences. This review explores the circular economy model's potential as a sustainable wastewater management strategy for FT effluent management. Furthermore, the paper investigates ameliorative measures to overcome the limitations of one biological treatment method, anaerobic digestion of FT effluents by examining the combination of nutrient augmentation, microbial augmentation, and enrichment from the integration of wastes derived from other industrial sectors as pivotal to the implementation of circular economics modelling in FT effluents valuation. This approach to the circular economy model can help overcome the environmental concerns posed by FT effluents in its advocacy of resource sharing, reuse, and recycling. This review also promotes circular economy principles to improve resource recovery, recycling, and collaboration with other industrial sectors, such as agriculture and mining, with FT application industries to create a more sustainable economy and reduce their environmental footprints. However, since the chemical compositions of wastes vary with location and other parameters, future case studies should optimize the waste mixtures to determine the optimal balance before valorizing them.

Recent advances in heavy metal/metalloid ion treatment from wastewater using nanocomposites and bionanocomposites

Wastewater remediation is of paramount importance for the water-stressed modern civilization from the perspective of sustainable development and the management of limited freshwater resources. Contaminants such as heavy metal and metalloid ions, toxic dyes, and pathogenic microbes present in the aquatic ecosystem have adverse effects not only on the environment but also on human health. Traditional wastewater remediation processes are costly, energy-consuming, and have less efficiency in removing pollutants from wastewater. Multi-phasic nanomaterials or nanocomposites have enormous potential for removing contaminants from water bodies. These materials have an enormous tunable surface area for interacting with the target toxicants and are extremely stable in the aquatic system, but they readily agglomerate. Many research groups have exploited biosorption, bioleaching, and bioprecipitation capacities of fungal hyphae for wastewater remediation. Recently, researchers have attempted to explore the synergistic effect of the bionanocomposite of fungal hyphae and nanomaterials for removing pollutants from wastewater. This bionanocomposite has already shown promise as a superior material for wastewater treatment and can easily be separated from the polluted water for reuse over several cycles. The bionanocomposite-mediated decontamination of water can lead to a total paradigm shift in wastewater management strategies.

A review of advanced wastewater treatment technologies: USA vs. Africa

This research paper conducts a comprehensive comparative analysis of advanced wastewater treatment technologies in the USA and Africa, emphasizing infrastructure, regulatory frameworks, and socio-economic factors. The USA exhibits robust infrastructure, supportive regulations, and technological awareness, fostering the adoption of advanced solutions. In contrast, Africa faces limited resources and diverse regulatory landscapes. Affordability, accessibility, public awareness, and education are critical socio-economic factors influencing technology adoption. Prospects include innovations like AI integration and circular economy principles. Policy recommendations stress adaptive frameworks and international collaborations. The conclusion underscores the importance of inclusive strategies for global sustainable wastewater management, recognizing each region's unique socio-economic diversity. This research contributes valuable insights for policymakers, researchers, and practitioners working towards resilient and equitable wastewater treatment systems.

An efficient wastewater collection model for groundwater resource protection in smart cities

Efficient wastewater collection is a critical concern in the development of smart cities, where sustainable urban infrastructure is paramount. In the context of smart city wastewater optimization, this study highlights the need for a comprehensive approach that considers both surface water and groundwater dynamics. Existing methods often fall short in addressing groundwater-related concerns, with limitations in accounting for potential contamination and aquifer vulnerability. The proposed method integrates a nuanced understanding of groundwater aspects, providing a more robust and sustainable solution for urban water resource management. This research introduces a new approach that harnesses the power of Divide-And-Conquer (DAC) and Variable Neighborhood Search (VNS) to optimize wastewater collection systems in smart cities. The DAC strategy divides the city into manageable zones, simplifying the optimization problem for parallel processing in large-scale urban environments. VNS fine-tunes wastewater collection networks within each zone by exploring diverse neighborhood solutions. The DAC and VNS offers several benefits, including improved efficiency in wastewater transport, reduced energy consumption, and minimized environmental impact. Zoning the urban landscape is a strategic approach to optimize wastewater collection in smart cities. It involves dividing the city into manageable zones based on specific criteria such as geographical features, population density, and infrastructure layout. Each zone is treated as an independent unit for focused analysis and optimization. The optimization process employs a scoring function that combines weighted criteria, yielding a composite score for each geographical location. Applying a threshold or clustering algorithm group's locations into zones, facilitating tailored wastewater management strategies. By optimizing collection routes and infrastructure design, this approach assists smart cities in achieving sustainability goals while efficiently managing wastewater. The study showcases the potential of DAC and VNS as a robust and adaptable solution for wastewater collection in smart cities, contributing to the development of greener, more resource-efficient urban areas.

Photothermal self-floating aerogels based on chitosan functionalized with polydopamine and carbon nanotubes for removal of arsenic from wastewater

Although wastewater disposal in evaporation ponds may be a cost-effective strategy for wastewater management, it overlooks water recycling and can possibly pose significant threats to the surrounding environment. The development of photothermal materials with functional groups capable of adsorbing toxic contaminants offers a promising opportunity for detoxification and potentially solar-driven recycling of wastewater disposed in evaporation ponds. In this study, ultralight aerogels based on chitosan (Ch), a natural biodegradable polymer, functionalized with mussel-inspired polydopamine (PDA) and carbon nanotubes (CNT) were fabricated through a facile approach and examined for the removal of arsenic from water. Three aerogels, namely chitosan, CNT/Ch, and PDA@CNT/Ch were fabricated and characterized using SEM, FTIR, TGA, XPS, and BET surface area analysis. Adsorption isotherms, thermodynamics, and kinetics were systematically investigated, revealing the feasibility of the fabricated aerogels for arsenic removal from aqueous solutions. The UV–Vis and photothermal analysis indicated excellent light-absorption and light-to-heat conversion performance of the functionalized aerogels. Arsenic adsorption by aerogels occurred rapidly and reached equilibrium within 30 to 60 min and was well-fitted by pseudo second-order kinetics model. The Langmuir model well described the adsorption isotherm, and the maximum adsorption capacities were found to be 31.5, 36.6, and 38.7 mg/g at neutral pH for chitosan, CNT/Ch, and PDA@CNT/Ch, respectively. The adsorption mechanism was studied by FTIR and XPS analysis and the adsorption pathway was evaluated using intraparticle diffusion model. This study broadens the scope of utilizing aerogels for the detoxification and potential recycling of wastewater from diverse sources and effluents disposed in evaporation ponds.

Microplastic removal in managed aquifer recharge using wastewater effluent

Microplastic (MP) pollution has emerged as a pressing environmental issue, with its impacts on ecosystems and human health yet to be fully understood. This study aims to investigate the presence and distribution of MPs in the soil of a managed aquifer recharge (MAR) system, built with different reactive barriers of natural materials and irrigated with the secondary effluent of a wastewater treatment plant (WWTP). MPs were extracted from reactive barrier material following an approach based on the density separation of MPs with posterior oxidant digestion, combined with visual and chemical characterisation by Fourier-Transform Infrared Spectroscopy (FTIR). The results revealed the widespread occurrence of MPs in the MAR soil samples. MPs concentration in the different barrier materials ranged from 60 to 236 n kg−1. The most dominant morphologies were fragments (60%) and fibers (17%), and the most abundant colour was white (51%), followed by transparent MPs (20%). Polypropylene (PP) was detected in all the samples with an abundance of 47%, followed by polyethylene (PE, 34%). The interplay of barrier composition significantly influences the retention of MPs, with compost (T5) and woodchips (T4) exhibiting the most notable retention rates. Remarkably, the outer layers of the reactive barriers display superior retention compared to the deeper layers.The findings of this study demonstrate the good performance of the MAR system in retaining MPs and contribute to the growing body of knowledge on MPs pollution in freshwater systems while providing insights into the dynamics of MPs transport and accumulation in soil. Such information can inform the development of effective wastewater management strategies to mitigate the impacts of these pollutants on water resources and safeguard the environment.

Selective Separation between Ammonium and Potassium in a Membrane-Separated Magnesium-Based Electrochemical Process

Increasing trends in global food and water demands alongside growing environmental concerns press the need for developing new wastewater management strategies. Modern wastewater treatment facilities should provide nutrient recovery and recycling, localized production capabilities, and low energy consumption. Magnesium-based electrochemical wastewater treatment processes are one technology option with the potential to address these needs by providing opportunities for simultaneous recovery of valuable resources from waste streams. In this system, phosphate and ammonium coprecipitate with the magnesium released from the sacrificial anode, producing struvite, NH4MgPO4, as a fertilizer. This technology also eliminates the disadvantages of the commonly used chemical precipitation method of struvite recovery, including magnesium salt dosing, and adding base to the system for pH control, due to in situ magnesium corrosion and hydroxide production at the magnesium anode surface.In this presentation, we specifically focus on a membrane-separated electrochemical process with a solid magnesium electrode. A complex synthetic water matrix including key ions such as ammonium, potassium, and phosphorus with other background salts was made for the anodic chamber to simulate animal liquid manures. Sodium sulfate solution was used as the supporting electrolyte on the cathodic chamber. Two different cation exchange membranes (CEMs) were placed between the two compartments to separate the anolyte from the catholyte. All experiments were conducted under OCV (no external energy input), and ion concentrations in each chamber were tracked over time using ion chromatography to perform kinetic study. The produced precipitates from each experiment are collected and have been characterized by scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) to identify the morphology and purity of the produced solid precipitates. Furthermore, X-ray diffraction (XRD) and Fourier-transform infrared spectrometry (FT-IR) were used to exactly identify the nature of the precipitates. Experimental results indicate that magnesium electrode corrosion under OCV in the anolyte will decrease ammonium separation through the CEM to the catholyte compared to potassium.

Prevalence of antibiotic-resistant Gram-negative bacteria having extended-spectrum β-lactamase phenotypes in polluted irrigation-purpose wastewaters from Indian agro-ecosystems.

Antibiotic resistance in bacteria has emerged as a serious public health threat worldwide. Aquatic environments including irrigation-purpose wastewaters facilitate the emergence and transmission of antibiotic-resistant bacteria and antibiotic resistance genes leading to detrimental effects on human health and environment sustainability. Considering the paramount threat of ever-increasing antibiotic resistance to human health, there is an urgent need for continuous environmental monitoring of antibiotic-resistant bacteria and antibiotic resistance genes in wastewater being used for irrigation in Indian agro-ecosystems. In this study, the prevalence of antibiotic resistance in Gram-negative bacteria isolated from irrigation-purpose wastewater samples from Sirmaur and Solan districts of Himachal Pradesh was determined. Bacterial isolates of genera Escherichia, Enterobacter, Hafnia, Shigella, Citrobacter, and Klebsiella obtained from 11 different geographical locations were found to exhibit resistance against ampicillin, amoxyclav, cefotaxime, co-trimoxazole, tobramycin, cefpodoxime and ceftazidime. However, all the isolates were sensitive to aminoglycoside antibiotic gentamicin. Enterobacter spp. and Escherichia coli showed predominance among all the isolates. Multidrug-resistance phenotype was observed with isolate AUK-06 (Enterobacter sp.) which exhibited resistant to five antibiotics. Isolate AUK-02 and AUK-09, both E. coli strains showed resistant phenotypes to four antibiotics each. Phenotypic detection revealed that six isolates were positive for extended-spectrum β-lactamases which includes two isolates from Enterobacter spp. and E. coli each and one each from Shigella sp. and Citrobacter sp. Overall, the findings revealed the occurrence of antibiotic resistant and ESBL-positive bacterial isolates in wastewaters utilized for irrigation purpose in the study area and necessitate continuous monitoring and precautionary interventions. The outcomes of the study would be of significant clinical, epidemiological, and agro-environmental importance in designing effective wastewater management and environmental pollution control strategies.

Exploring the Potential and Challenges of Electrochemical Processes for Sustainable Waste Water Remediation and Treatment

Emerging as an efficient, cost-effective, and environmentally sound approach, electrochemical treatment methods hold significant promise for sustainable remediation and wastewater treatment. This review elucidates recent progress in electrochemical techniques used for site decontamination and wastewater management. It elucidates the fundamental electrochemical processes, detailing the principles of electrocoagulation, electroflocculation, electrochemical membranes, electrochemical oxidation (EO), and advanced oxidation processes (AOPs). The broad applicability of these methods for contaminant removal, inclusive of heavy metals, organic pollutants, complex organic compounds, and suspended particulate matter, is underscored. Notwithstanding, the adoption of these techniques encounters notable challenges. These involve the heterogeneity of soil conditions, the presence of intricate contaminant mixtures, and the risk of electrode fouling and degradation. Suggestions for overcoming such challenges include refining the comprehension of electrochemical treatment processes in field-scale applications, investigating innovative electrode materials, and developing advanced modeling and simulation tools. This review offers a robust overview of electrochemical treatment strategies for sustainable wastewater management and can guide researchers, engineers, and policymakers towards the successful adoption and implementation of these techniques to meet environmental challenges and foster sustainable water management.

High-resolution hydrodynamics of coral reefs and tracing of pollutants from hotel areas along the west coast of Unguja Island, Zanzibar

A rapid increase in population size along with expansion in hotel investment have been identified as key drivers of marine pollution in Zanzibar coastal waters. A validated high-resolution hydrodynamic tracer model was used to estimate the dispersal and impact range of pollutants from the main hotel areas along the western coastline of Unguja Island. The model showed the highest impact of pollutants from land during the northeast monsoon season due to the weakening of the main current. Marine protected areas with short distances to hotel areas and weak tidal currents were more likely to be impacted by pollutants from land than the more remote areas with higher flushing in agreement with water quality and seagrass health measurements. Cumulative effects of pollutants instead of single sources are important to consider for integrated wastewater treatment plans and management strategies to reduce pollution for the protection of biodiversity and guide future monitoring.

Chemical characterization and source attribution of organic pollutants in industrial wastewaters from a Chinese chemical industrial park

Accelerated urbanization and industrialization have led to an alarming increase in the generation of wastewater with complex chemical contents. Industrial wastewaters are often a primary source of water contamination. The chemical characterization of different industrial wastewater types is an essential task to interpret the chemical fingerprints of wastewater to identify pollution sources and develop efficient water treatment strategies. In this study, we conduct a non-target chemical analysis for the source characterization of different industrial wastewater samples collected from a chemical industrial park (CIP) located in southeast China. The chemical screening identified volatile and semi-volatile organic compounds that included dibutyl phthalate at a maximum concentration of 13.4 μg/L and phthalic anhydride at 35.9 μg/L. Persistent, mobile, and toxic (PMT) substances among the detected organic compounds were identified and prioritized as high-concern contaminants given their impact on drinking water resources. Moreover, a source analysis of the wastewater collected from the wastewater outlet station indicated that the dye production industry contributed the largest quantities of toxic contaminates (62.6%), and this result was consistent with the ordinary least squares and heatmap results. Thus, our study utilized a combined approach of a non-target chemical analysis, a pollution source identification method, and a PMT assessment of different industrial wastewater samples collected from the CIP. The results of the chemical fingerprints of different industrial wastewater types as well as the results of the PMT assessment benefit risk-based wastewater management and source reduction strategies.

Metagenomic Insight into Microbiome and Antibiotic Resistance Genes of High Clinical Concern in Urban and Rural Hospital Wastewater of Northern India Origin: a Major Reservoir of Antimicrobial Resistance.

India is one of the largest consumers and producers of antibiotics and a hot spot for the emergence and proliferation of antimicrobial resistance genes (ARGs). Indian hospital wastewater (HWW) accumulates ARGs from source hospitals and often merges with urban wastewater, with the potential for environmental and human contamination. Despite its putative clinical importance, there is a lack of high-resolution resistome profiling of Indian hospital wastewater, with most studies either relying on conventional PCR-biased techniques or being limited to one city. In this study, we comprehensively analyzed antibiotic resistomes of wastewater from six Indian hospitals distributed in rural and urban areas of northern India through shotgun metagenomics. Our study revealed the predominance of ARGs against aminoglycoside, macrolide, carbapenem, trimethoprim, and sulfonamide antibiotics in all the samples through both read-based analysis and assembly-based analysis. We detected the mobile colistin resistance gene mcr-5.1 for the first time in Indian hospital sewage. blaNDM-1 was present in 4 out of 6 samples and was carried by Pseudomonas aeruginosa in HWW-2, Klebsiella pneumoniae in HWW-4 and HWW-6, and Acinetobacter baumanii in HWW-5. Most ARGs were plasmid-mediated and hosted by Proteobacteria. We identified virulence factors and transposable elements flanking the ARGs, highlighting the role of horizontal gene transmission of ARGs. IMPORTANCE There is a paucity of research on detailed antibiotic resistome and microbiome diversity of Indian hospital wastewater. This study reports the predominance of clinically concerning ARGs such as the beta-lactamases blaNDM and blaOXA and the colistin resistance gene mcr and their association with the microbiome in six different Indian hospital wastewaters of both urban and rural origin. The abundance of plasmid-mediated ARGs and virulence factors calls for urgent AMR crisis management. The lack of proper wastewater management strategies meeting international standards and open drainage systems further complicates the problem of containing the ARGs at these hospitals. This metagenomic study presents the current AMR profile propagating in hospital settings in India and can be used as a reference for future surveillance and risk management of ARGs in Indian hospitals.

Maximizing nutrient recovery from aquaponics wastewater with autotrophic or heterotrophic management strategies

Aquaponics uses bacterial processes and plant nutrient uptake to recover nutrients from aquaculture wastewater. However, little is known about which wastewater management strategy is best suited for nutrient recovery. We compared four aquaponics water management strategies: pH 6 or pH 7 with autotrophic bacterial populations (pH 6, pH 7), and pH 6 or 7 with heterotrophic bacterial populations (pH6M, pH 7 M). The results indicated that nutrients recovered with greater efficiency in pH 6 and pH 6 M than in pH 7, with higher plant biomass and food quality. pH 6 displayed the highest nitrogen (N) use efficiency (NUE = 65.5 %) and the lowest N loss as gas (34.5 %), followed by pH 6 M, suggesting that lower pH in aquaponics could enhance NUE and reduce N loss. pH 6 M had the highest phosphorus (P) use efficiency (PUE = 65.0 %) suggesting that lower pH and heterotrophic bacterial populations facilitate P recovery from wastewater. Plant nutrient uptake was improved when heterotrophic bacterial populations were established in an environmental pH of 6.

Applications and implications of carbon nanotubes for the sequestration of organic and inorganic pollutants from wastewater.

The rapid growth in the population, industrial developments, and climate change over the century have contributed to a significant rise in aquatic pollution leading to a scarcity of clean, reliable, and sustainable water sources and supply. Exposure through ingestion, inhalation, and dermal absorption of organic/inorganic compounds such as heavy metals, pharmaceuticals, dyes, and persistent organic pollutants (POPs) discharged from municipalities, hospitals, textile industries, food, and agricultural sectors has caused adverse health outcomes in aquatic and terrestrial organisms. Owing to the high surface area, photocatalytic activity, antimicrobial, antifouling, optical, electronic, and magnetic properties, the application of nanotechnology offers unique opportunities in advanced wastewater management strategies over traditional approaches. Carbon nanomaterials and associated composites such as single-walled carbon nanotubes (SWCNT), multiwalled carbon nanotubes (MWCNT), and carbon nanotubes (CNT) buckypaper membranes have demonstrated efficiency in adsorption, photocatalytic activity, and filtration of contaminants and thus show immense potentiality in wastewater management. This review focuses on the application of CNTs in the sequestration of organic and inorganic contaminants from the aquatic environment. It also sheds light on the aquatic pollutant desorption processes, current safety regulations, and toxic responses associated with CNTs. Critical knowledge gaps involving CNT synthesis, surface modification processes, CNT-environment interactions, and risk assessments are further identified and discussed.

Drip fertigation with treated municipal wastewater and soil amendment with composted sewage sludge for sustainable protein-rich rice cultivation

Rice paddy farming is threatened by global water scarcity, necessitating the adoption of novel water-saving cultivation practices. The purpose of this study is to determine the effects of drip fertigation with treated municipal wastewater (TWW) on a rice–soilsystem that is amended with composted sewage sludge (CSS). The treatments included flood irrigation with tap water (Control; T1), flood irrigation with TWW (T2), drip irrigation (DI) with TWW at 86% water consumption (T3), DI with TWW at 75% water consumption (T4), DI with TWW at 69% water consumption (T5), and DI with tap water at 86% water consumption (T6). The control was administered mineral fertilizers, and all other treatments received the same N amount (260 kg ha −1 ) from CSS. The results indicated that TWW drip fertigation had a significant beneficial effect on rice production by increasing (59.7 g pot −1 , T3) or maintaining (51.4 g pot −1 , T4) grain yield while conserving up to 25% of water when compared to conventional flood irrigation and mineral fertilizer application (52.9 g pot −1 ). In comparison to conventional farming, TWW drip fertigation in conjunction with CSS amendment significantly increased grain protein and Cu content while reducing As accumulation by 50%. Both CSS and TWW are effective at retaining soil fertility while avoiding unfavorable accumulation of As, Pb, Cd, Cu, and Zn. The novel cultivation techniques described herein have the potential to significantly improve the sustainability of rice farming in water-stressed areas, as well as integrated wastewater management strategies aimed at achieving sustainable development goals. • Rice farming can benefit from treated wastewater (TWW) and composted sludge (CSS). • TWW drip fertigation greatly increased rice yield and conserved up to 25% of water. • CSS and TWW reuse increased protein while lowering As contents by 50% in grains. • The practices effectively preserved soil fertility without toxic element buildup.

Unraveling the dynamics of organic micropollutants in wastewater: Online LC-MS/MS analysis at high temporal resolution

Online monitoring of organic micropollutants (OMPs) in the aquatic environment at high temporal resolution is an upcoming technique that provides insights into their dynamics and has the potential to bring water research and management to a new level. An online monitoring setup was developed to quantify OMPs in wastewater treatment plant (WWTP) influent and effluent using automated and continuous sampling, sample preparation, online solid-phase extraction-liquid chromatography-tandem mass spectrometry analysis and data evaluation. This online monitoring setup provided high selectivity and sensitivity (limit of quantification down to 1 ng/L) as well as a stable performance during one week of constant operation whilst using a high sampling frequency of 10 min (>1000 samples). Custom automated data evaluation enabled quantification within seconds after each measurement and results were comparable to those from a commercial software. Additionally, an alarm tool was included in the evaluation application, which automatically notified the user in case a substance exceeded a predefined threshold. The online monitoring setup was applied to WWTP influent and effluent, where 57 substances were monitored over a period of one week and two days, respectively. High temporal resolution enabled the observation of periodic patterns of pharmaceuticals as well as pollution by OMPs originating from point and diffuse sources, while dynamics of OMPs in WWTP effluent were less pronounced. These new insights into the dynamics of OMPs in WWTP influent, which would not be observable using 24 h composite samples, will be a starting point for new stormwater and wastewater research and management strategies.

Unintended nutrient imbalance induced by wastewater effluent inputs to receiving water and its ecological consequences

Eutrophication is the most widespread water quality issue globally. To date, most efforts to control eutrophication have focused on reductions of external nutrient inputs, yet importance of nutrient stoichiometry and subsequent shift in plankton composition in aquatic ecosystem has been largely neglected. To address eutrophication, improved sanitation is one of the United Nations Sustainable Development Goals, spurring the constructions of wastewater treatment facilities that have improved water quality in many lakes and rivers. However, control measures are often targeted at and effective in removing a single nutrient from sewage and thus are less effective in removing the others, resulting in the changes of nutrient stoichiometry. In general, more effective phosphorus removal relative to nitrogen has occurred in wastewater treatment leading to substantial increases in N/P ratios in effluent relative to the influent. Unfortunately, high N/P ratios in receiving waters can impose negative influences on ecosystems. Thus, long-term strategies for domestic wastewater management should not merely focus on the total reduction of nutrient discharge but also consider their stoichiometric balances in receiving waters.

Why wastewater treatment fails to protect stream ecosystems in Europe

There is significant debate about why less than half of European rivers and streams are in good ecological status, despite decades of intense regulatory efforts. Of the multiple stressors that are recognized as potential contributors to stream degradation, we focus on discharge from 26,500 European wastewater treatment plants (WWTPs). We tested the hypothesis that stream ecological status degradation across Europe is related to the local intensity of wastewater discharge, with an expected stream-order (ω) dependence based on the scaling laws that govern receiving stream networks. We found that ecological status in streams (ω≤3) declined consistently with increasing urban wastewater discharge fraction of stream flow (UDF) across river types and basins. In contrast, ecological status in larger rivers (ω≥4) was not related to UDF. From a continental-scale logistic regression model (accuracy 86%) we identified an ecologically critical threshold UDF = 6.5% ± 0.5. This is exceeded by more than one third of WWTPs in Europe, mostly discharging into smaller streams. Our results suggest that new receiving water-specific strategies for wastewater management are needed to achieve good ecological status in smaller streams.