Techno-economic assessment of zero liquid discharge (ZLD) systems for sustainable treatment, minimization and valorization of seawater brine

Membrane Technologies for Sustainable Wastewater Treatment: Advances, Challenges, and Applications in Zero Liquid Discharge (ZLD) and Minimal Liquid Discharge (MLD) Systems

As the demand for sustainable water and wastewater management continues to rise in both desalination and industrial sectors, there is been notable progress in developing Zero Liquid Discharge (ZLD) and Minimal Liquid Discharge (MLD) systems. Membrane technologies have become a key component of these systems, providing effective solutions for removing contaminants and enabling the recovery of both water and valuable resources. This article explores recent advancements in the design and operation of ZLD and MLD systems, discussing their benefits, challenges, and how they fit into larger treatment processes. Emphasis is given to membrane-based processes, such as reverse osmosis (RO), membrane distillation (MD), and forward osmosis (FO), as well as hybrid configurations, and innovative membrane materials. These advancements are designed to address critical challenges like fouling, scaling, high energy demands, and high brine production. The article also explores exciting research directions aimed at enhancing the efficiency and durability of membrane technologies in ZLD and MLD systems, paving the way for new innovations in sustainable water management across various industries.

Investigation on the rotary atomization evaporation of high-salinity desulfurization wastewater: Performance and products insights

Spray drying of concentrated wastewater epitomizes a harmonious convergence of technological progress, economic viability, and practicality within the realm of zero liquid discharge. Nevertheless, elevated salinity may influence the atomization and evaporation processes, along with the storage and transportation of evaporation products. This study systematically examines the influence of salinity on rotary atomization evaporation performance and evaporation products of wastewater through a series of experimental investigations. The results indicate that, under identical conditions, the overall droplet size of high-salinity wastewater is approximately 20-50% larger compared to conventional wastewater. Salinity significantly influences the atomization particle size (D32), followed by rotation speed, and then influent flow rate. The high-salinity wastewater droplets manifest a multi-bubble growth pattern with earlier shell expansion, where the reduction of free water dominates the overall process dynamics. Despite the diminished evaporation rate, the total evaporation duration shortens with elevating salinity, reducing flue gas consumption by about 10%. With elevated crystalline salt content, high-salinity wastewater evaporation products exhibit pronounced hygroscopicity, manifesting as a viscous powder with suboptimal flowability (FF 3.57) at a 2 wt% moisture content. This study bridges the gap in rotary spray drying technology for high-salinity wastewater treatment, contributing to sustainable water conservation and energy-efficient management.

Vapor Pressure and Evaporation Studies of Saline Solutions on Natural and Synthetic Fabrics for Industrial Water Treatment

In the present paper, we have conducted a comprehensive analysis of vapor pressures of both saturated and unsaturated solutions, alongside a study of evaporation using synthetic and natural fabrics for industrial applications in brackish water treatment under zero liquid discharge (ZLD) philosophy. By determining the vapor pressures of saturated solutions, we obtained results consistent with those of other researchers, extending the range of tested temperatures from 1 to 50 °C and successfully fitting the parameters of an Antoine-type equation. Similarly, positive results were achieved for unsaturated solutions, where various parameters of different equations accounting for the salt concentration were estimated, simplifying the fitting procedure. Natural evaporation tests from water surfaces using saturated solutions revealed that salts with higher associated vapor pressures exhibit higher evaporation rates. On the other hand, hydrated salts retain water in their structure and are significantly affected by ambient humidity. Evaporation studies on natural and synthetic fabrics with saturated NaCl and CuSO4·5H2O solutions showed distinct behaviors. NaCl increased both the evaporation rate and salt deposition with each cycle. In contrast, CuSO4·5H2O reduced the absorption capacity by blocking the fabric's structure, decreasing the evaporation efficiency over successive cycles.

Data-Monitoring Solution for Desalination Processes: Cooling Tower and Mechanical Vapor Compression Hybrid System

The advancement of novel water treatment technologies requires the implementation of both accurate data measurement and recording processes. These procedures are essential for acquiring results and conducting thorough analyses to enhance operational efficiency. In addition, accurate sensor data facilitate precise control over chemical treatment dosages, ensuring optimal water quality and corrosion inhibition while minimizing chemical usage and associated costs. Under this framework, this paper describes the sensoring and monitoring solution for a hybrid system based on a cooling tower (CT) connected to mechanical vapor compression (MVC) equipment for desalination and brine concentration purposes. Sensors connected to the data commercial logger solution, Almemo 2890-9, are also discussed in detail such as temperature, relative humidity, pressure, flow rate, etc. The monitoring system allows remote control of the MVC based on a server, GateManager, and TightVNC. In this way, the proposed solution provides remote access to the hybrid system, being able to visualize gathered data in real time. A case study located in Cartagena (Spain) is used to assess the proposed solution. Collected data from temperature transmitters, pneumatic valves, level sensors, and power demand are included and discussed in the paper. These variables allow a subsequent forecasting process to estimate brine concentration values. Different sample times are included in this paper to minimize the collected data from the hybrid system within suitable operation conditions. This solution is suitable to be applied to other desalination processes and locations.

A comprehensive assessment of the economic and technical viability of a zero liquid discharge (ZLD) hybrid desalination system for water and salt recovery

Brine, a by-product of desalination and industrial facilities, is becoming more and more of an environmental issue. This comprehensive techno-economic assessment (TEA), focusing on the technical and economic aspects, investigates the performance and viability of a novel hybrid desalination brine treatment system known as zero liquid discharge (ZLD). Notably, this research represents the first instance of evaluating the feasibility and effectiveness of integrating three distinct desalination processes, namely brine concentrator (BC), high-pressure reverse osmosis (HPRO), and membrane-promoted crystallization (MPC), within a ZLD framework. The findings of this study demonstrate an exceptional water recovery rate of 97.04%, while the energy requirements stand at a reasonable level of 17.53 kWh/m3. Financially, the ZLD system proves to be at least 3.28 times more cost-effective than conventional evaporation ponds and offers comparable cost efficiency to alternatives such as land application and deep-well injection. Moreover, the ZLD system exhibits profitability potential by marketing both drinking water and solid salt or solely desalinated water. The daily profit from the sale of generated water varies from US$194.08 to US$281.41, with Greece and Cyprus attaining the lowest and highest profit, respectively. When considering the sale of both salt and water, the profit rises by 8% across all locations.

Design of a multistage hybrid desalination process for brine management and maximum water recovery

Hypersaline brine production from desalination plants causes huge environmental stress due to the untenable conventional discharge strategies. Particularly, brine production is expected to drastically increase in the coming few decades due to the increasing desalination capacity in attempts of forestalling water scarcity. Thereby, zero liquid discharge (ZLD) is a worth-considering solution for strategic brine management. ZLD or minimal liquid discharge (MLD) systems provide maximum water recovery with least or zero liquid waste generation and valuable salt production. In this work, a theoretical design of ZLD/MLD system is proposed for reverse osmosis (RO) brine management. Different scenarios are investigated utilizing multistage freeze desalination (FD) and its hybridization with multistage direct contact membrane distillation (DCMD), and eutectic freeze crystallization (EFC) technologies. The design is based on the experimental assessment of the indirect FD process at different feed salinities, i.e., 2 g/L to 155 g/L. FD experiments showed that ice quality is reduced at greater crystallinity levels and initial concentration. Moreover, a computational fluid dynamics (CFD) model is utilized to assess the performance of DCMD. A single DCMD module could produce 53 kg/(m2.h) of pure water operating with 69% thermal efficiency. Eventually, water recovery, water quality, as well as specific energy consumption (SEC) are evaluated for the whole system. Based on different configurations of the hybrid ZLD system, the proposed design can achieve water recovery between 40 and 93% with SEC range of 28-114 kWh/m3. Results also showed that the produced water quality exceeds drinkable water standards ( ≪ 500 mg/L). This work has provided great evidence in the practicality of ZLD/MLD systems for sustainable brine management.

Review on the escalating imperative of zero liquid discharge (ZLD) technology for sustainable water management and environmental resilience

This comprehensive review delves into the forefront of wastewater treatment technology, with a specific focus on the revolutionary concept of Zero Liquid Discharge (ZLD). (ZLD), underpinned by a sustainable ethos, aspires to accomplish total water reclamation, constituting a pivotal response to pressing environmental issues. The paper furnishes a historical panorama of (ZLD), elucidating its motivating factors and inherent merits. It navigates a spectrum of (ZLD) technologies encompassing thermal methodologies, (ZLD) synergized with Reverse Osmosis (RO), High-Efficiency Reverse Osmosis (HERO), Membrane Distillation (MD), Forward Osmosis (FO), and Electrodialysis Reversal (EDR). Moreover, the study casts a global purview over the deployment status of (ZLD) systems in pursuit of resource recovery, accentuating nations such as the United States, China, India, assorted European Union members, Canada, and Egypt. Meticulous case studies take center stage, underscoring intricate scenarios involving heavily contaminated effluents from challenging sectors including tanneries, textile mills, petroleum refineries, and paper mills. The report culminates by distilling sagacious observations and recommendations, emanating from a collaborative brainstorming endeavor. This compendium embarks on an enlightening journey through the evolution of wastewater treatment, (ZLD)'s ascendancy, and its transformative potential in recalibrating water management paradigms while harmonizing industrial progress with environmental stewardship.

3D Cellular Solar Crystallizer for Stable and Ultra-Efficient High-Salinity Wastewater Treatment

Recent developed interfacial solar brine crystallizers, which employ solar-driven water evaporation for salts crystallization from the near-saturation brine to achieve zero liquid discharge (ZLD) brine treatment, are promising due to their excellent energy efficiency and sustainability. However, most existing interfacial solar crystallizers are only tested using NaCl solution and failed to maintain high evaporation capability when treating real seawater due to the scaling problem caused by the crystallization of high-valent cations. Herein, an artificial tree solar crystallizer (ATSC) with a multi-branched and interconnected open-cell cellular structure that significantly increased evaporation surface is rationally designed, achieving an ultra-high evaporation rate (2.30 kg m-2  h-1 during 2 h exposure) and high energy efficiency (128%) in concentrated real seawater. The unit cell design of ATSC promoted salt crystallization on the outer frame rather than the inner voids, ensuring that salt crystallization does not affect the continuous transport of brine through the pores inside the unit cell, thus ATSC can maintain a stable evaporation rate of 1.94 kg m-2  h-1 on average in concentrated seawater for 80 h continuous exposure. The design concept of ATSC represents a major step forward toward ZLD treatment of high-salinity brine in many industrial processes is believed.

A review of the development in shale oil and gas wastewater desalination

The development of the shale oil and gas extraction industry has heightened concerns about shale oil and gas wastewater (SOGW). This review comprehensively summarizes, analyzes, and evaluates multiple issues in SOGW desalination. The detailed analysis of SOGW water quality and various disposal strategies with different water quality standards reveals the water quality characteristics and disposal status of SOGW, clarifying the necessity of desalination for the rational management of SOGW. Subsequently, potential and implemented technologies for SOGW desalination are reviewed, mainly including membrane-based, thermal-based, and adsorption-based desalination technologies, as well as bioelectrochemical desalination systems, and the research progress of these technologies in desalinating SOGW are highlighted. In addition, various pretreatment methods for SOGW desalination are comprehensively reviewed, and the synergistic effects on SOGW desalination that can be achieved by combining different desalination technologies are summarized. Renewable energy sources and waste heat are also discussed, which can be used to replace traditional fossil energy to drive SOGW desalination and reduce the negative impact of shale oil and gas exploitation on the environment. Moreover, real project cases for SOGW desalination are presented, and the full-scale or pilot-scale on-site treatment devices for SOGW desalination are summarized. In order to compare different desalination processes clearly, operational parameters and performance data of varying desalination processes, including feed salinity, water flux, salt removal rate, water recovery, energy consumption, and cost, are collected and analyzed, and the applicability of different desalination technologies in desalinating SOGW is qualitatively evaluated. Finally, the recovery of valuable inorganic resources in SOGW is discussed, which is a meaningful research direction for SOGW desalination. At present, the development of SOGW desalination has not reached a satisfactory level, and investing enough energy in SOGW desalination in the future is still necessary to achieve the optimal management of SOGW.

Effect of thermal characteristics on the chemical quality of real-brine treatment through hydrophilic fiber-based low-grade heat-powered humidification-dehumidification process

Considering the increasing demand for desalination plants and their byproduct brine, this study investigated a humidification-dehumidification (HDH) system for treating membrane distillation-generated real high-salinity brine using low-grade heat (45-70 ℃) to explore its feasibility for sustainable energy-efficient minimal liquid discharge. A novel super-hydrophilic fabric was adopted for accelerated humidification, and its impact on brine droplet miscarriage characteristics was evaluated. The influence of the operating fluid thermal properties (cycle 1: air preheating; cycle 2: air and brine dual-fluid preheating; and cycle 3: air post-heating after humidification) on the brine treatment efficiency, energy consumption, and chemical quality of freshwater produced was analyzed in detail to establish their characteristic nexus. It was identified that, during humidification, increasing the brine temperature (up to 55 ℃) influenced its ionic mobility, thereby promoting efficient separation of the salts/minerals and contributing to achieving better freshwater quality. Furthermore, although cycle 3 exhibited improved system thermal efficiency (gained output ratio equal to 1.77), its non-preheated air contributed to a negative effect of the reduced humidity ratio (∼17 g/kg), leading to a lower freshwater productivity of 67% than that of cycle 2 (29 g/kg and 70%). The present study also illustrates a novel effect of evaporative deposition occurring due to air-water interaction on the fabric humidifier surface, with an exploration of its effect on reducing freshwater chemical quality. The freshwater generated from optimum thermal cycle 2 exhibited reduced pH (by ∼63%), sodium (99.9%), chloride (99.9%), toxic boron (99.7%), and other chemical contaminants, thereby satisfying the major international water reuse standards.

Study on the Adsorption Properties of Oxalic Acid-Modified Cordierite Honeycomb Ceramics for Neutral Red Dyes

Removal of organic dyes from water by monolithic adsorbents is considered as an efficient and no-secondary pollution method. Herein, for the first time cordierite honeycomb ceramics (COR) treated with oxalic acid (CORA) were synthesized. This CORA exhibits outstanding removal efficiency toward the azo neutral red dyes (NR) from water. After optimizing the reaction conditions, the highest adsorption capacity of 7.35 mg·g^-1 and a removal rate of 98.89% could be achieved within 300 min. Furthermore, investigation of the adsorption kinetics indicated this adsorption process could be described as a pseudo-second-order kinetic model with k ₂ and q _e of 0.0114 g·mg^-1·min^-1 and 6.94 mg·g^-1, respectively. According to the fitting calculation, the adsorption isotherm could also be described as the Freundlich isotherm model. The removal efficiency could be maintained above 50% after 4 cycles, negating the need for toxic organic solvent extraction, offering a method for bringing the technology one step closer to industrial application and giving CORA promising potential in practical water treatment.

3D Printing of Solar Crystallizer with Polylactic Acid/Carbon Composites for Zero Liquid Discharge of High-Salinity Brine

Zero liquid discharge (ZLD) is a technique for treating high-salinity brine to obtain freshwater and/or salt using a solar interface evaporator. However, salt accumulation on the surface of the evaporator is a big challenge to maintaining stable water evaporation. In this study, a simple and easy-to-manufacture evaporator, also called a crystallizer, was designed and fabricated by 3D printing. The photothermal layer printed with polylactic acid/carbon composites had acceptable light absorption (93%) within the wavelength zone of 250 nm–2500 nm. The micron-sized voids formed during 3D printing provided abundant water transportation channels inside the crystallizer. After surface hydrophilic modification, the crystallizer had an ultra-hydrophilic channel structure and gravity-assisted salt recovery function. The results revealed that the angles between the photothermal layers affected the efficacy of solar evaporation and the yield of solid salt. The crystallizer with the angle of 90° between two photothermal layers could collect more solid salt than the three other designs with angles of 30°, 60°, and 120°, respectively. The crystallizer has high evaporation and salt crystallization efficiency in a high-salinity brine environment, which is expected to have application potentials in the zero liquid discharge of wastewater and valuable salt recovery.

Salinity and Mulching Effects on Nutrition and Production of Grafted Sour Passion Fruit

The Brazilian semiarid region stands out in terms of sour passion fruit production. Local climatic conditions (high air temperature and low rainfall), combined with its soil properties (rich in soluble salts), increase salinity effects on plants. This study was carried out in the experimental area "Macaquinhos" in Remígio-Paraíba (Brazil). The aim of this research was to evaluate the effect of mulching on grafted sour passion fruit under irrigation with moderately saline water. The experiment was conducted in split-plots in a 2 × (2 × 2) factorial scheme to evaluate the effects of the combination of irrigation water salinity of 0.5 dS m-1 (control) and 4.5 dS m-1 (main plot), passion fruit propagated by seed and grafted onto Passiflora cincinnata, with and without mulching (subplots), with four replicates and three plants per plot. The foliar Na concentration in grafted plants was 90.9% less than that of plants propagated via seeds; however, it did not affect fruit production. Plastic mulching, by reducing the absorption of toxic salts and promoting greater absorption of nutrients, contributed to greater production of sour passion fruit. Under irrigation with moderately saline water, the plastic film in the soil and seed propagation promote higher production of sour passion fruit.

Decarbonized and circular brine management/valorization for water & valuable resource recovery via minimal/zero liquid discharge (MLD/ZLD) strategies

Brine (saline wastewater/water) from desalination, salt lakes, and industrial activities (e.g., pharmaceutical industries, oil & gas industries) has received a lot of attention around the world due to its adverse impact on the environment. Currently, several disposal methods have been applied; however, these methods are nowadays unsustainable. To tackle this problem, brine treatment and valorization is considered a promising strategy to eliminate brine discharge and recover valuable resources such as water, minerals, salts, metals, and energy. Brine valorization and resource recovery can be achieved via minimal and zero liquid discharge (MLD & ZLD) desalination systems. Commercially successful technologies such as reverse osmosis (RO) and distillation cannot be adopted as standalone technologies due to restrictions (e.g., osmotic pressure, high-energy/corrosion). Nonetheless, novel technologies such as forward osmosis (FO), membrane distillation (MD) can treat brine of high salinity and present high recovery rates. The extraction of several ions from brines is technically feasible. The minerals/salts composed of major ions (i.e., Na⁺, Cl^-, Mg²⁺, Ca²⁺) can be useful in a variety of sectors, and their sale prices are reasonable. On the other hand, the extraction of scarce metals such as lithium, rubidium, and cesium can be extremely profitable as their sale prices are extremely higher compared to the sale prices of common salts. Nonetheless, the extraction of such precious metals is currently restricted to a laboratory scale. The MLD/ZLD systems have high energy consumption and thus are associated with high GHGs emissions as fossil fuels are commonly burned to produce the required energy. To make the MLD/ZLD systems more eco-friendly and carbon-neutral, the authors suggest integrating renewable energy sources such as solar energy, wind energy, geothermal energy, etc. Besides water, minerals, salts, metals, and energy can be harvested from brine. In particular, salinity gradient power can be generated. Salinity gradient power technologies have shown great potential in several bench-scale and pilot-scale implementations. Nonetheless, several improvements are required to promote their large-scale feasibility and viability. To establish a CO₂-free and circular global economy, intensive research and development efforts should continue to be directed toward brine valorization and resource recovery using MLD/ZLD systems.

Hydrogeochemical characteristics and processes of thermokarst lake and groundwater during the melting of the active layer in a permafrost region of the Qinghai-Tibet Plateau, China

Permafrost degradation and the development of thermokarst lakes are important factors driving the variability of regional hydrologic processes. Hydrogeochemical and isotopic analyses are important methods for investigating the hydrologic processes of thermokarst lakes. This study focused on comparing the chemical and hydrogeochemical characteristics between lake water and groundwater during the melting of the active layer in a typical thermokarst lake region on the Qinghai-Tibet Plateau (QTP). Ninety-five samples were collected during different periods of active layer melting and analyzed using statistical, isotope, hydrogeochemical, and modeling methods. Statistical results showed that the average concentrations of almost all ions were lower in lake water than in groundwater, with wider spatial variability in groundwater. The lake water is of the ClNa and HCO₃-Ca type with low TDS (total dissolved solids), whereas groundwater is of the HCO₃-Ca and mixed type (or transition type) with high TDS. The chemical types of the lake water and groundwater are mainly driven by rock weathering. In terms of the saturation index (SI), halite and gypsum are unsaturated dissolved, whereas dolomite and calcite are generally saturated. Evaporation significantly affects the chemical composition of groundwater, while the hydrochemical compositions of lake water are relatively stable under the joint control of evaporation, precipitation, surface runoff, and groundwater. The isotopic analysis results showed that the contribution of permafrost meltwater and precipitation to groundwater and lake water varied during different stages of active layer melting. According to hydrogeochemical modeling, the main chemical reactions in groundwater are the precipitation of calcite and the dissolution of halite, dolomite, and gypsum. The intensity of groundwater flow determines the degree of chemical reactions along the flow path at different stages of active layer melting. The findings can provide deeper insight into hydrogeochemical processes in thermokarst lake regions under the background of permafrost degradation.

Preparation of zeolitic imidazolate framework-67/wool fabric and its adsorption capacity for reactive dyes

Zeolitic imidazolate framework-67 (ZIF-67) formed by Co²⁺ and 2-methylimidazole (MIM) is widely used for adsorption and separation of pollutants. However, there are some disadvantages for ZIF-67 powder, such as strong electrostatic interaction and difficulty in recovery from the liquid phase. The available way to solve the above problems is choosing a suitable substrate to load ZIF-67. The amino and hydroxyl of wool fabrics effectively capture and fix ZIF-67, making it easy to separate ZIF-67 by taking out the composite materials from aqueous solution. In this study, ZIF-67/Wool fabric (ZW) was successfully prepared. The results show that ZIF-67 has better adsorption performance for reactive dyes with more sulfonic groups, higher molecular weight and lower steric resistance. The equilibrium adsorption capacity of ZW for reactive red 195 was 4.15 mg g^-1. The adsorption accorded with pseudo-second-order kinetic model and Langmuir isotherm. This study improved the application of ZIF-67, which provided a treatment method for dyeing wastewater and made it possible to recycle waste wool.

Resources recovery-Separation and recovery of copper from desalination brine through Lewatit TP 207 resin

Because of freshwater scarcity caused by extreme climate change, desalination technique has been developed in many countries to acquire freshwater. However, desalination plants worldwide not only produce freshwater but also generate large amounts of high salinity wastewater (brine). Brine discharge will decrease the concentration of dissolved oxygen in seawater and affect the organism's habitat. The only merit of the brine is that the concentrations of valuable metals in brine are higher than in seawater. Therefore, it is an opportunity to recover metals from brine and solve the environmental problem simultaneously. This study then aims to recover copper from brine through the ion exchange method. The research could be divided into three parts. To begin with, the saturated adsorption capacity of copper through Lewatit TP 207 resin was 30.58 mg/g, and the adsorption behavior was in accord with the Langmuir model. The optimal parameters of copper adsorption through the resin would be surveyed in the second part. The results demonstrated that 16.1 mg/l of copper could be adsorbed from brine under contacting period of 16 min, pH 14, L/S ratio of 2000, and temperature at 328 K. In addition, the thermodynamic parameters would also be explored to realize how the adsorption reaction was processed. Lastly, different agents and desorption parameters would be investigated to separate the copper from the resin. The copper compound and the resin could be obtained and regenerated after desorption. PRACTITIONER POINTS: Reusing desalination brine could reduce its amount of discharge and increase its value. A 16.1 mg/l of copper could be adsorbed from desalination brine through the Lewatit TP 207 system. The optimal parameters are contacting period of 16 min, pH 14, L/S ratio of 2000, and temperature at 328 K. After adsorbing, copper could be desorbed by HCl, and copper chloride could be acquired by vacuum drying the solutions. This is a method with the goal of laboratory-safe, low-cost, and high-energy efficiency.

Phytotoxicity complements chemical assessment for re-use and re-purposing of refinery wastes for soil amendment purposes after bioremediation

The objective of this study was to assess the suitability of onsite re-use of mature compost for landscaping and tree mulching, produced from the bioremediation of oily sludge from the refinery. Compost samples from the co-composting process were analysed for a range of contaminants, including a human health risk assessment fractionation (HRAF) of the remaining petroleum hydrocarbons, as well as a phytotoxicity test. The chemical characterisation demonstrated that the process removed more than 94% of the original petroleum hydrocarbons from the sludge, and the removal rates were high at 1155 mg/kg/day. The HRAF demonstrated no residual risks, posed by the petroleum hydrocarbons present in the compost to human health if used on-site when compared to the relevant Australian environmental investigation levels (ILs). However, the phytotoxicity assessment demonstrated that the compost was toxic to germinating lettuce. The gap in the literature this study addressed was to provide an estimate of the LD₅₀ and no effect concentration (NEC) for the compost using a standard plant bioassay containing a range of residual (aged) and bioremediated refinery process wastes, including petroleum hydrocarbons. The values estimated for LD₅₀ and NEC were approximately 125 and 43 mg/kg, respectively for compost containing residual petroleum hydrocarbon fractions, filling a gap in the current literature which has limited data on standard toxicity values that can be used in determining and informing commercial remediation strategies and their outcomes with aged sludges. Phytotoxicity was shown to be an important complement to conventional analyses and HRAF data when characterising the sludge, and understanding its potential for re-use. The novelty of the study is that it highlighted a gap in the complementary use of chemical and bioassay analyses for evaluating refinery waste remediation endpoints, which has potential for broader application to other projects.

Thermally assisted efficient electrochemical lithium extraction from simulated seawater

Extracting lithium electrochemically from seawater has the potential to resolve any future lithium shortage. However, electrochemical extraction only functions efficiently in high lithium concentration solutions. Herein, we discovered that lithium extraction is temperature and concentration dependent. Lithium extraction capacity (i.e., the mass of lithium extracted from the source solutions) and speed (i.e., the lithium extraction rate) in electrochemical extraction can be increased significantly in heated source solutions, especially at low lithium concentrations (e.g., < 3 mM) and high Na⁺/Li⁺ molar ratios (e.g., >1000). Comprehensive material characterization and mechanistic analyses revealed that the improved lithium extraction originates from boosted kinetics rather than thermodynamic equilibrium shifts. A higher temperature (i.e., 60 ^oC) mitigates the activation polarization of lithium intercalation, decreases charge transfer resistances, and improves lithium diffusion. Based on these understandings, we demonstrated that a thermally assisted electrochemical lithium extraction process could achieve rapid (36.8 mg g^-1 day^-1) and selective (51.79% purity) lithium extraction from simulated seawater with an ultrahigh Na⁺/Li⁺ molar ratio of 20,000. The integrated thermally regenerative electrochemical cycle can harvest thermal energy in heated source solutions, enabling a low electrical energy consumption (11.3-16.0 Wh mol^-1 lithium). Furthermore, the coupled thermal-driven membrane process in the system can also produce freshwater (13.2 kg m^-2 h^-1) as a byproduct. Given abundant low-grade thermal energy availability, the thermally assisted electrochemical lithium extraction process has excellent potential to realize mining lithium from seawater.

Tuning of Sm3+ and Er3+-doped TiO2 nanofibers for enhancement of the photocatalytic performance: Optimization of the photodegradation conditions

Titanium dioxide (TiO₂)-based nanofibers doped with samarium (Sm³⁺) and erbium (Er³⁺) at doping levels tuned in the range of 0.05-1.0% were prepared by the electrospinning-calcination method. The produced materials were well characterized by X-ray diffraction, SEM, EDX, and UV-vis diffuse reflectance spectroscopy. These one-dimensional nanostructures showed a crystalline structure with values of fiber diameters values between 60 and 100 nm. The best catalyst sample of this study was formulated as TiO₂:Sm (0.1%) and sintered at 600 °C. And, it was employed to intensify the photocatalytic process under visible-light irradiation. Likewise, the chemometric approach was applied to optimize the process. The results revealed that the rate constant for the photo-degradation of a cationic organic pollutant was significantly improved (k = 3.496 × 10^-1 min^-1). In terms of the reaction half-life, the intensification and optimization of the process led to a decrease in the half-life of the reaction from 68 to 2 min. And, these are outstanding findings for the photo-degradation process under visible-light irradiation. In addition, the total organic carbon (TOC) removal efficiencies were found to be 69.95% and 72.30% for the mineralization of MB and CIP, respectively, after a 360 min reaction time, which are significant results. Moreover, this material demonstrated remarkable photocatalytic activity for the degradation of ciprofloxacin (CIP) with a 99.6% removal efficiency and a rate constant of 4.292 × 10^-1 min^-1. Finally, the stability and reusability of this catalyst were demonstrated during five repetitive cycles of the CIP photodegradation.

Impact of anaerobic digestion on reactive nitrogen gas emissions from dairy slurry storage

Biogas digesters are commonly used to treat animal manure/slurry, and abundant digested slurry is generated during the digestion process. Gas emissions from digested and raw slurry may vary with the change in slurry parameters after digestion, but the mechanism is not well understood. Gas emissions from raw dairy slurry (RS) and digested dairy slurry (BS) during 98 days of storage were investigated in this study to evaluate the effects of anaerobic digestion on reactive nitrogen emissions from slurry storage. Results showed that much higher N₂O and NO emission and lower NH₃ emission was achieved in BS than in RS. The mean gaseous emission of RS and BS accounted for 27.8% ± 6.9% and 17.1% ± 2.3% of the initial TN for NH₃, 0.1% ± 0.1% and 3.5% ± 1.6% of the initial TN for N₂O, and 0.0% ± 0.0% and 0.2% ± 0.0% of the initial TN for NO, respectively. Among all detected N₂O-forming and reducing microbial genes, the abundance of amoA genes was the most closely related to N₂O flux (r = 0.54, p < 0.01). More aerobic conditions occurred in BS, and dissolved oxygen (DO) increased to 0.4-1.6 mg L^-1 after 35 days because the low organic matter of BS resulted in good infiltration of surface air into the slurry. The increased DO stimulated the growth of Nitrosomonas and the increase in amoA gene copies and contributed to the high N₂O and NO emissions in BS through the nitrification process. Vulcanibacillus, Thauera, Castellaniella, and Thermomonas were the major denitrifying bacteria that occurred in BS and caused an incomplete denitrification process, which could be another reason for the increase in N₂O and NO emissions from BS. Our study indicated that anaerobic digestion reduced the organic matter content of the slurry and caused an active microbial environment that facilitated the transformation of slurry N to N₂O in BS storage, thus lowering the NH₃ emission compared with RS storage. Therefore, aside from NH₃, N₂O should also be preferentially mitigated during BS storage because N₂O is a greenhouse gas with high global warming potential.

Preparation of adsorptive polyethyleneimine/polyvinyl chloride electrospun nanofiber membrane: Characterization and application

Landfilling and burning plastic waste, especially waste polyvinyl chloride (PVC), can produce highly toxic and carcinogenic by-products that threaten the ecosystem and human health. However, there is still a lack of proper methods for waste PVC recycling. Therefore, developing feasible ways for waste PVC recovery is urgently needed. The purpose of this study is to analyze the characteristics of PVC-based adsorptive nanofiber membranes and test their ability for the treatment of wastewater containing Cibacron Brilliant Yellow 3G-P, a widely used reactive dye. The polyethylenimine/polyvinyl chloride membrane (PEI/PVCM) was characterized by FTIR, FE-SEM, TGA, tensile analysis, water contact angle measurement, and zeta-potential analysis. The FTIR analysis confirmed that the PEI has successfully crosslinked with PVC. The FE-SEM images showed that the nanofibers constituting PEI/PVCM are compact with an average fiber diameter of 181 nm. The TGA results showed that the membrane was able to remain stable in wastewater below 150 °C. The average stress and strain of the PEI/PVCM were 7.64 ± 0.32 MPa and 934.14 ± 48.12%, respectively. The water contact angle and zeta potential analysis showed that after the introduction of PEI, the membrane converted from hydrophobic to hydrophilic, and the pH_pzc was increased from 3.1 to 1.08. The pure water flux of the membrane was measured at 0.1 MPa and the result was 3013 ± 60 L/m²‧h. The wastewater purification capability of PEI/PVCM was measured at an initial dye concentration of 10 ppm and pH 4-9 at 0.1 MPa. The reusability of PEI/PVCM was verified through three adsorption-desorption cycles. The results demonstrated that the PEI/PVCM is a reusable membrane for efficient purification of wastewater containing reactive dyes over a wide pH range (pH 4-8).

A review of ammonia removal using a biofilm-based reactor and its challenges

Extensive growth of industries leads to uncontrolled ammonia releases to environment. This can result in significant degradation of the aquatic ecology as well as significant health concerns for humans. Knowing the mechanism of ammonia elimination is the simplest approach to comprehending it. Ammonia has been commonly converted to less hazardous substances either in the form of nitrate or nitrogen gas. Ammonia has been converted into nitrite by ammonia-oxidizing bacteria and further reduced to nitrate by nitrite-oxidizing bacteria in aerobic conditions. Denitrification takes place in an anoxic phase and nitrate is converted into nitrogen gas. It is challenging to remove ammonia by employing technologies that do not incur particularly high costs. Thus, this review paper is focused on biofilm reactors that utilize the nitrification process. Many research publications and patents on biofilm wastewater treatment have been published. However, only a tiny percentage of these projects are for full-scale applications, and the majority of the work was completed within the last few decades. The physicochemical approaches such as ammonia adsorption, coagulation-flocculation, and membrane separation, as well as conventional biological treatments including activated sludge, microalgae, and bacteria biofilm, are briefly addressed in this review paper. The effectiveness of biofilm reactors in removing ammonia was compared, and the microbes that effectively remove ammonia were thoroughly discussed. Overall, biofilm reactors can remove up to 99.7% ammonia from streams with a concentration in range of 16-900 mg/L. As many challenges were identified for ammonia removal using biofilm at a commercial scale, this study offers future perspectives on how to address the most pressing biofilm issues. This review may also improve our understanding of biofilm technologies for the removal of ammonia as well as polishing unit in wastewater treatment plants for the water reuse and recycling, supporting the circular economy concept.

Towards a sustainable organic waste supply chain: A comparison of centralized and decentralized systems

Proper disposal of Municipal Solid (MSW) waste is an important issue as it causes land, air, and water pollution. Organic MSW provides a habitat environment to insects and often it spreads dangerous diseases. Major reasons identified behind this as the non-separation of MSW at the source and lack of facilities (bins) in the appropriate place for collection of wastes. The present study has proposed an integrated three-stage model to provide a solution to the problem of (i) allocation of the bin for waste collection, (ii) allocation and comparison of centralized and decentralized composting plants, and finally, (iii) vehicle routing for waste collection. The proposed generic model is applied to an Indian city, Bilaspur located in the state of Chhattisgarh. From the results, it is observed that the first stage model provides an optimal number of bins required and allocation of it at minimum cost. Taking it as input for the second stage model, it identifies the best locations for centralized and decentralized composting plants. The result also reveals that decentralized composting plants are more economical than centralized plants. Finally, the third stage of the model identifies the vehicle routing for the waste collection considering both centralized and decentralized plants to minimize the cost. Further, sensitivity analysis is carried out on collection rate and participation percentage parameters to draw additional insights for better management of MSW.

Challenges and opportunities of terahertz technology in construction and demolition waste management

Construction and demolition waste are one of the largest waste streams generated in the EU by volume. They consist of materials such as concrete, bricks, gypsum, wood, glass, metals, foams, plastics, solvents, asbestos, asphalt, and excavated soil. Nowadays, many of them can be recycled, some even endlessly. This research attempts to contribute to the non-destructive characterization of such a waste with a novel method using terahertz radiation. By combining terahertz imaging and spectroscopy, we performed analytical characterization of selected building materials. The results demonstrate that terahertz technology allows an inside view into some of the non-conducting building materials. THz imaging can detect and visualize the organic solvents in the insulation material, which are often disposed of together with construction and demolition waste. It can also visualize the content of foreign objects or hazardous and toxic substances, which is important for their separation in the recyclate according to the type of the material. Furthermore, THz spectra reveal some spectral lines that can differentiate between different plastics and polymers within the frequency range of 1.0-4.5 THz due to different material structures and chemical compositions. Such results significantly contribute to the decision of which product meets all the standards, which can be returned to the production process due to irregularities or may be disposed of as waste. The only way to reduce construction and demolition waste in the future is to encourage the adoption of innovative technologies like terahertz spectroscopy in combination with traditional methods. This approach can bring some changes also to the construction design philosophy toward more sustainable buildings with minimum end-of-life demolition.

Model-based water accounting for integrated assessment of water resources systems at the basin scale

Agricultural activities in the concept of integrated water resources management play a vital role. Especially in dry and semi-dry regions, agricultural activities have the largest share of water consumption. By employing a model-based approach using modified Soil and Water Assessment Tool (SWAT agro-hydrological model), this study has prepared Water Accounting Plus (WA+) framework requirements to investigate different conditions of supply and demand in wet (1985-2000) and dry (2001-2015) periods in a semi-dry basin (Karkheh River Basin) in Iran. Our assessments based on WA+ show decreasing 10% (21.65 to 19.29 Billion Cubic Meters (BCM)/year) of precipitation in the dry period caused a 4% (0.13 BCM/year) decline in natural evapotranspiration. However, the basin experienced a 24% increment in evapotranspiration from agricultural activities at the same period, and runoff was approximately halved (2.45 BCM/year). Therefore, especially in downstream parts, surface water withdrawal has decreased by 18%. These new conditions have put pressure on groundwater resources. The aquifer extraction and total withdrawal for irrigation have grown by about 17% and 4%, respectively. Finally, it is evident that the manageable water has diminished due to climate change; not only the managed water consumption in the basin has not reduced, but it has also highly risen. The current study results help water authorities arrange new hydrological and climatic conditions strategies.

Biochar as a potential strategy for remediation of contaminated mining soils: Mechanisms, applications, and future perspectives

Soil heavy metal contamination caused by mining activities is a global issue. These heavy metals can be enriched in plants and animals through the food chain, and eventually transferred to the human system and threatening public health. Biochar, as an environmentally friendly soil remediation agent, can effectively immobilize heavy metals in soil. However, most researchers concern more about the remediation effect and mechanism of biochar for industrial and agricultural contaminated soil, while related reviews focusing on mining soil remediation are limited. Furthermore, the remediation effect of soil in mining areas is affected by many factors, such as physicochemical properties of biochar, pyrolysis conditions, soil conditions, mining environment and application method, which can lead to great differences in the remediation effect of biochar in diverse mining areas. Therefore, it is necessary to systematically unravel the relevant knowledge of biochar remediation, which can also provide a guide for future studies on biochar remediation of contaminated soils in mining areas. The present paper first reviews the negative effects of mining activities on soil and the advantages of biochar relative to other remediation methods, followed by the mechanism and influencing factors of biochar on reducing heavy metal migration and bioavailability in mining soil were systematically summarized. Finally, the main research directions and development trends in the future are pointed out, and suggestions for future development are proposed.

Environmental factors associated with the filamentous green algae Cladophora blooms: A mesocosm experiment in a shallow eutrophic lake

The process of ecological restoration in eutrophic lakes, often results in the blooming of the filamentous green algae Cladophora. This consequently affects the growth of submerged plants and the restoration of vegetation. However, the blooming process of Cladophora and the environmental factors affecting their growth are poorly understood. This has become a difficult problem in the management of lakes. The study therefore focused on succession process of Cladophora blooms and their driving factors through mesocosm experiments in Caohai Lake. The results of our experiment indicated that Cladophora growth was mainly affected by water temperature, turbidity and soluble reactive phosphorus concentration of the habitat where Elodea nuttallii and Cladophora coexist. Nuisance Cladophora was mainly affected by turbidity (>19.24 NTU) when the water temperature was above 15.7 °C. With increasing Cladophora biomass and decreasing turbidity (<4.88 NTU), Cladophora biomass accumulation was mainly limited by the soluble reactive phosphorus concentration (<3.2 μg/L). Recorded turbidity range of 9.54-13.19 NTU was found to cause dramatic changes in the biomass of Cladophora. The results also showed that the outbreak of Cladophora blooms was mainly attributed to turbidity when the water temperature was appropriate in eutrophic lakes. These findings suggest that successful management efforts should strengthen the monitoring of transparency change in addition to controlling the phosphorus concentration to limit the Cladophora overgrowth on lake ecological restoration.

Adsorption of vanadium (V) ions from the aqueous solutions on different biomass-derived biochars

The paper presents the results of the studies on the vanadium (V) ions removal from the aqueous solutions in the adsorption process on biochars from different biomass types (cow manure BC1, wet distiller grains BC2, spent mushroom substrates BC3). The adsorbents were characterized by means of the SEM-EDS, FTIR, XRD and XPS techniques. The influence of adsorbent type and basic process parameters, such as pH and metal ion concentration in aqueous phase, adsorbent dose and time of contact of phases on the efficiency of V(V) was determined. Based on the obtained results, the mechanism and kinetics of the adsorption processes occurring on the biochar originating from the wet distiller grains as adsorbents with the greatest affinity for the V(V) ions were characterized, using isotherm models of Langmuir, Freundlich, Temkin and Dubinin-Radushkevich and pseudo-first-order, pseudo-second-order as well as intraparticle diffusion kinetic models. Under the constant process conditions (pH = 3.0; m = 0.5 g; c₀ = 50 mg/L) the order of V(V) ions removal from aqueous solutions was as follows: BC2 > BC1 = BC3. The biochar BC2 exhibited the maximum sorption capacity of 1.61 mg V(V)/g. The experimental kinetic data show the adsorption course according to the pseudo-second order model.

Quantification and health risk assessment of nitrate in southern districts of Tehran, Iran

Nitrate is a common contaminant of drinking water. Due to its adverse health effects, this study aimed to determine nitrate levels in six southern districts of Tehran. A total of 148 samples were taken from tap waters. In 84.46% (n = 125) of the samples, the nitrate concentration was below national and WHO limits (50 mg/L); however, 15.54% (n = 23) were in violation of the criteria. The total mean concentration of nitrate was 36.15 mg/L (±14.74) ranging from 4.52 to 80.83 mg/L. The overall hazard quotient (HQ) for age groups were ordered as Children (1.71) &gt; Infants (1.24) &gt; Teenagers (1.2) &gt; Adults (0.96). In all districts, the HQ values for infants and children groups were greater than 1, indicating potential adverse health risks. In teenagers age group, only the HQ estimations of districts 10 (HQ = 0.93) and 11 (HQ = 0.74) were lower than 1 and in adults age group, the estimated HQ values for districts were lower than 1 with the exception for district 19 (HQ = 1.19). The sensitivity analysis (SA) showed that nitrate content plays a major role in the value of the assessed risk.

Preparation and Modification of PVDF Membrane and Study on Its Anti-Fouling and Anti-Wetting Properties

Membrane distillation (MD) has unique advantages in the treatment of high-salt wastewater because it can make full use of low-grade heat sources. The high salinity mine water in western mining areas of China is rich in Ca2+, Mg2+, SO42− and HCO3−. In the MD process, the inorganic substances in the feed will cause membrane fouling. At the same time, low surface tension organic substances which could be introduced in the mining process will cause irreversible membrane wetting. To improve the anti-fouling and anti-wetting properties of the membrane, the PVDF omniphobic membrane in this paper was prepared by electrospinning. The water contact angle (WCA) can reach 153°. Direct contact membrane distillation (DCMD) was then used for treating high-salinity mine water. The results show that, compared with the unmodified membranes, the flux reduction rate of the omniphobic membrane was reduced by 34% in 20 h, showing good anti-fouling property. More importantly, the omniphobic membrane cannot be wetted easily by the feed containing 0.3 mmol/L SDS. The extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory was used to analyze the free energy of the interface interaction between the membrane and pollutants, aiming to show that the omniphobic membrane was more difficult to pollute. The result was consistent with the flux variation in the DCMD process, providing an effective basis for explaining the mechanism of membrane fouling and membrane wetting.

Assessment of groundwater arsenic contamination using machine learning in Varanasi, Uttar Pradesh, India

This paper presents a machine learning approach for classification of arsenic (As) levels as safe and unsafe in groundwater samples collected from the Indo-Gangetic region. As water is essential for sustaining life, heavy metals like arsenic pose a public health concern. In this study, various tree-based machine learning models namely Random Forest, Optimized Forest, CS Forest, SPAARC, and REP Tree algorithms have been applied to classify water samples. As per the guidelines of the World Health Organization (WHO), the arsenic concentration in water should not exceed 10 μg/L. The groundwater quality parameter was ranked using a classifier attribute evaluator for training and testing the models. Parameters obtained from the confusion matrix, such as accuracy, precision, recall, and FPR, were used to analyze the performance of models. Among all models, Optimized Forest outperforms other classifier as it has a high accuracy of 80.64%, a precision of 80.70%, recall of 97.87%, and a low FPR of 73.33%. The Optimized Forest model can be used to test new water samples for classification of arsenic in groundwater samples.

Removal of Recalcitrant Compounds from Winery Wastewater by Electrochemical Oxidation

The electro-oxidation of recalcitrant compounds, phthalic acid, tyrosol, and catechin was studied in simulated and real winery wastewater samples using a boron-doped diamond (BDD) anode. In the simulated samples, catechin, although presenting a higher removal rate than that of phthalic acid and tyrosol, attained lower combustion efficiency, indicating that this compound is readily converted into other products rather than being completely oxidized. On the other hand, phthalic acid was easily mineralized. Regarding the electro-oxidation assays performed with the spiked winery wastewater, recalcitrant compounds and overall organic load removal rates increased with applied current density (j), but the removal efficiency of recalcitrant compounds decreased with the increase in j, and the specific energy consumption was significantly raised. The increase in treatment time showed to be a feasible solution for the WW treatment at lower j. After 14 h treatment at 300 A m−2, phthalic acid, tyrosol, and catechin removals above 99.9% were achieved, with a chemical oxygen demand removal of 98.3%. Moreover, the biodegradability index was increased to 0.99, and toxicity towards Daphnia magna was reduced 1.3-fold, showing that the electro-oxidation process using a BDD anode is a feasible solution for the treatment of winery wastewaters, including phthalic acid, tyrosol, and catechin degradation.