Wastewater Treatment Technologies Research Articles

Preparation of sulfur-doped porous carbon from polyphenylene sulfide waste for photothermal conversion materials to achieve solar-driven water evaporation.

In recent years, solar-driven photothermal water evaporation technology for seawater desalination and wastewater treatment has developed rapidly, which is of great significance for addressing the issue of freshwater scarcity. However, due to the high costs associated with the manufacturing, maintenance, and operation of such devices, their application remains challenging in remote and resource-scarce regions. Due to its excellent light absorption capability in the near-infrared region, high hydrophilicity, and stable chemical properties, coupled with the low cost of recycling waste carbonized polyphenylene sulfide, this material is an excellent choice as a photothermal material for solar-driven water evaporation devices. Ordinary wood in nature usually has a highly regenerative porous structure, which is a natural water transport channel that facilitates the transport of water from the bottom to the top, allowing it to be rapidly converted into vapor. Based on this characteristic, this article innovatively proposes to prepare waste polyphenylene sulfide from porous carbonized materials (KCP) as the photothermal conversion material for novel photothermal water evaporation devices, achieving solar-driven water evaporation. This material efficiently facilitates the conversion between solar and thermal energies and exhibits excellent hydrophilicity, thereby enabling the rapid utilization of absorbed solar energy for water evaporation on the surface of the evaporator. In this study, a porous carbonized polyphenylene sulfide photothermal water evaporator (KCP-wood) was fabricated by using freeze-drying and in situ coating to load the photothermal conversion material onto a wood substrate. Under simulated one-sun irradiation, this evaporator achieved a water evaporation rate of 2.41 kg m-2 h-1 and a photothermal conversion efficiency of 91.3%. Additionally, a systematic study was conducted on the photothermal performance of various light-water evaporators, encompassing photothermal conversion efficiency, stability, thermal conductivity, and anti-fouling capabilities. Finally, the practical performance of the light-water evaporator under various environmental conditions was validated, demonstrating its excellent stability and durability. It is capable of effectively applying to high-efficiency water resource utilization and solar energy conversion fields.

Research Progress in Photocatalytic-Coupled Microbial Electrochemical Technology in Wastewater Treatment

Research Progress in Photocatalytic-Coupled Microbial Electrochemical Technology in Wastewater Treatment

Evolutionary trends and development of constructed wetland coupled microbial fuel cell: A decade of development.

Constructed wetland coupled microbial fuel cells (CW-MFC) have gained considerable attention as an innovative sustainable technology for simultaneous wastewater treatment and bio-electricity generation since its inception in 2012. This study, which employed bibliometrics of research articles and patent analysis, is a comprehensive investigation into the evolutionary trend and development status of CW-MFC. We analyzed 85 patents and 247 research articles using structured and unstructured data. By using the logistic model and econometric analysis, we predicted the technological life cycle and investigated the factors driving the development of CW-MFC. In addition, this study discusses the innovative hotspots, research and innovative trends, and key contributors at the forefront of this green infrastructure. The study results show that CW-MFC technology has gained greater interest under the influence of national and international policies, market demand, economic growth, and national R&D expenditure, highlighting its global impact. The study also showed that CW-MFC was predominantly distributed in Asia, with China at the forefront. The technology evolution path from both patents and papers showed the transition of research and development from the performance evaluation of CW-MFC with conventional-based technology to the current study focused on system optimization by exploring designs and component factors to enhance efficiency. Furthermore, the technological maturity (TMR) of CW-MFC was determined using the logistic model to be 50.5%, with significant potential for further development (R2=0.98). Overall, this study provides a comprehensive understanding of the current trends of CW-MFC development and provides forecasting and direction for future developments.

Mechanism of molecular communication and bacterial community succession in microalgal bacterial biofilms under different photoperiods.

Microalgal-bacterial biofilms are a competitive wastewater treatment technology. This study investigated the impact of photoperiod on the characteristics and performance of these biofilms in treating pig farm wastewater. Under continuous lighting (L-24h), we observed optimal NH4+-N removal efficiency, minimal chlorophyll levels, and peak concentrations of polysaccharides and c-di-GMP. The concentration of c-di-GMP, strongly correlated with the dominant genera Brevundimonas, Devosia, and Comamonas, modulated the maturation of microalgal-bacterial biofilms. The formation of these biofilms promoted NH4+-N removal. SEM imaging under L-24h conditions revealed microalgae and bacteria intimately bound by extracellular polymeric substances. Overall, this study unveiled the mechanisms of molecular communication and bacterial community succession within microalgal-bacterial biofilms under varying photoperiods.

Simultaneous nutrient-abundant hydroponic wastewater treatment, direct carbon capture, and bioenergy harvesting using microalgae–microbial fuel cells

Hydroponics has increasingly been recognized as an important agricultural method due to its stable crop yields under rapidly changing environmental conditions. However, the efficient treatment of nutrient-rich hydroponic wastewater remains a major challenge. This study investigates the effect of anodic pH on the performance of microalgae–microbial fuel cells (mMFCs), focusing on bioelectricity generation, photosynthetic oxygen supply, nutrient removal and recovery, and carbon capture. The mMFC system achieved a maximum power density of 122.5mW/m², a chemical oxygen demand removal efficiency of 93.7%, and an anode-side total nitrogen removal efficiency of 27.5% at an acidic anodic pH. In addition, the cathode chamber had a total ammonium nitrogen removal efficiency of 22.6%, which was ascribed to a combination of ammonium migration and subsequent nitrogen assimilation, and a phosphate removal efficiency of 100%, likely due to microalgal uptake and adsorption. The mMFC also effectively captured CO2 with an algal biomass yield of 0.01379g·L-1·d-1 and a CO₂ fixation rate of 0.02528g·L-1·d-1. These findings provide insights into the optimization of mMFCs as a sustainable solution for managing nutrient-rich hydroponic wastewater, contributing to energy-efficient and resource-recovering wastewater treatment technologies.

Integrated Wastewater Treatment Technology: Efficiency of Lime and Eichhornia crassipes for Agricultural Irrigation

Introduction: wastewater treatment for irrigation is a pressing challenge in rural areas, especially in communities where agriculture depends on contaminated water sources. This study focused on developing a low-cost, sustainable technology tailored to the needs of vulnerable populations.Methods: the efficiency of a combined treatment using lime and water hyacinth (Eichhornia crassipes) was evaluated in Joa, Ecuador. A completely randomized experimental design was employed to assess changes in key physicochemical parameters, including electrical conductivity, hardness, pH, nitrates, and sulfates, before and after the treatments.Results: water hyacinth reduced water hardness significantly, from 218 mg/L to 154 mg/L of CaCO₃, while lime controlled pH, maintaining it near neutral (7,4) with precise dosing. Despite these improvements, the combination showed limitations in reducing nitrates and sulfates to meet local regulatory standards. Nevertheless, the treatments enhanced overall water quality, making it more suitable for agricultural purposes.Conclusions: the combined use of lime and water hyacinth represents a feasible, eco-friendly solution for treating agricultural wastewater in resource-constrained settings. While effective in improving water quality, further studies are needed to optimize the system, explore scalability, and evaluate its long-term impact on soil and crop productivity

Biomass‐Derived Carbon Nanomaterials: Synthesis and Applications in Textile Wastewater Treatment, Sensors, Energy Storage, and Conversion Technologies

ABSTRACTPlant life has dominated this planet from the beginning of time. With over 82% of biomass (BM) coming from plants, primarily trees, plants are the dominant form of life on Earth. BM represents a readily available, ecologically favorable, and renewable low‐cost carbon source. Its rational disposal has emerged as a critical challenge in modern times due to its widespread generation from farming, manufacturing, and forestry activities. Nanotechnology (NT) has enormous potential for a wide range of BM‐related applications, including BM development, processing technique, modification, and utilization. Richard Feynman, a physicist who later won the Nobel Prize in Physics, presented a discussion in 1959 titled “There's Plenty of Room at the Bottom.” This address was the beginning of the New Theory of Physics, which is NT, where he discusses the potential of NT for manipulating matter at the atomic level. In recent years, there has been a significant surge in interest surrounding carbon nanomaterials (CNMs), specifically carbon nanotubes (CNTs) and graphene. These materials have captured the interest of researchers due to their extraordinary characteristics and widespread applications. Utilizing BM as a source shows great potential in creating functional carbon materials (CMs) due to its sustainability, affordability, and high carbon content. Nowadays, CNMs derived from BM have been a popular area of study. Various structures, synthesis techniques, and widespread applications of CNMs have been documented. Thus, this review provides a detailed overview that outlines the latest technological advancements in the fabrication of BM‐derived CMs. It also studies the production of high‐value‐added CNMs from BM and delves into the utilization of BM‐based CNMs as a precursor for textile wastewater treatment. Furthermore, this study also outlines the progress of BM‐derived CNMs in supercapacitors (SCs), sensors, battery electrode materials, fuel cells (FCs), and E‐textiles, showcasing their pivotal role in advancing sustainable technologies for the future.

Water quality prediction and carbon reduction mechanisms in wastewater treatment in Northwest cities using Random Forest Regression model

With the accelerated urbanization and economic development in Northwest China, the efficiency of urban wastewater treatment and the importance of water quality management have become increasingly significant. This work aims to explore urban wastewater treatment and carbon reduction mechanisms in Northwest China to alleviate water resource pressure. By utilizing online monitoring data from pilot systems, it conducts an in-depth analysis of the impacts of different wastewater treatment processes on water quality parameters. This work pays particular attention to their impact on key indicators such as Chemical Oxygen Demand (COD), NH4+-N, Total Phosphorus (TP), and Total Nitrogen (TN), and the application of predictive models. The work first establishes a Random Forest Regression (RFR) model. The RFR algorithm integrates Bagging ensemble learning and random subspace theory to construct multiple decision trees and aggregate their predictions, thereby enhancing the model’s prediction accuracy and stability. Using bootstrap sampling, the RFR model generates multiple training subsets from the original data and randomly selects subsets of variables to construct regression trees. Its performance in predicting various water quality indicators is then evaluated. The results show that the RFR model exhibits excellent performance, achieving high levels of prediction accuracy and stability for all indicators. For example, the R2 for COD prediction is 0.99954, while the R2 values for NH4+-N, TP, and TN predictions reach 0.99989. Compared to five other models, the RFR model demonstrates the best performance across all water quality indicator predictions. This work provides critical support for optimizing wastewater treatment technologies and developing water resource management policies. These findings also offer essential theoretical and empirical insights for the future improvement of urban wastewater treatment technologies and water resource management decision-making.

Congo red dye adsorption using ZnAl layered double hydroxide fabricated using hydrothermal methods

Industrial dye pollutants, particularly azo dyes like Congo red, pose significant environmental and health risks due to their toxic and non-biodegradable nature. This study assesses ZnAl Layered Double Hydroxide (ZnAl LDH) as an effective adsorbent, incorporating comprehensive materials characterization and adsorption isotherm analyses. Materials characterization using SEM and XRD confirmed the structural integrity and morphological suitability of ZnAl LDH for dye adsorption. Results demonstrated that ZnAl LDH, particularly the HMTA-based variant (h-ZnAl LDH), achieved superior adsorption capacities of up to 17.8 mg/g, significantly outperforming the urea-based (u-ZnAl LDH) with capacity of 12.3 mg/g. Kinetic analysis showed that the pseudo-second-order (PSO) model provided a better fit (R2 = 0.995) than the pseudo-first-order (PFO) model, indicating that chemisorption plays a dominant role in the adsorption mechanism. The adsorption process was also best described by the Langmuir isotherm model (R2 = 0.989), indicating monolayer adsorption on a homogeneous surface, while the Freundlich model (R2 = 0.944) also provided a reasonable fit, suggesting some degree of multilayer adsorption on heterogeneous surfaces. The superior performance of HMTA-based ZnAl LDH presents a significant advancement in wastewater treatment technologies

Photocatalytic degradations of organic pollutants in wastewater using hydrothermally grown ZnO nanoparticles

The increasing prevalence of organic pollutants in wastewater poses a significant environmental challenge due to their persistence and harmful effects. Photocatalysis using semiconductor nanoparticles, such as ZnO, has emerged as a promising approach for pollutant degradation, but optimizing the structural and functional properties of these materials remains a critical challenge. In this study, ZnO nanoparticles were synthesized via a hydrothermal method with varying durations (4, 6, and 8 hours) to investigate the impact of synthesis time on their photocatalytic efficiency. The structural and compositional properties were characterized using SEM, XRD, and EDS analyses, revealing that longer synthesis times improve crystallinity and alter the Zn:O atomic ratio, affecting defect density and stoichiometry. Photocatalytic performance was evaluated through the degradation of an organic pollutant under UV illumination. ZnO-6h exhibited the highest rate constant (k=0.017 min−1), outperforming ZnO-4h (k=0.016 min−1) and ZnO-8h (k=0.013 min−1). This superior activity is attributed to an optimal combination of high crystallinity, intermediate morphology, and the presence of oxygen vacancies that enhance charge carrier dynamics. The findings demonstrate that synthesis duration is a critical parameter in tuning the structural and photocatalytic properties of ZnO nanoparticles. This study provides insights into the design of ZnO-based photocatalysts and underscores their potential for environmental remediation. Future research could extend these findings by exploring scalability and pollutant-specific applications, paving the way for more efficient wastewater treatment technologies.

Microplastic occurrence and fate in the South African environment: a review

This review examines the occurrence and fate of microplastics (MPs) in freshwater, marine, and terrestrial environments in South Africa. MPs were found in Tshwane and Johannesburg in drinking water samples, with concentrations as high as 0.189 particles/L. Concentrations in freshwater bodies were greater, sometimes reaching 0.33–56 particles/L. MP levels in marine sediments were greater than many worldwide averages, particularly along the southeast coast (up to 45,867 particles/kg) and the MP levels in air were 1–5 particles/m3. These values are in line with figures around the globe which stand at 0.1–10 particles/L, and 0.3–10 particles/m3 for water, and air respectively. Low-density PE, PP, and PE-HD were the most prevalent polymers identified. Although there is little data, inappropriate disposal of waste is a major cause of soil contamination, which is a serious concern. The study highlights how important it is to conduct more research to close knowledge gaps, especially regarding MPs in groundwater and their impact on human health. The findings emphasise the necessity of improved wastewater treatment technologies, public awareness initiatives, and stronger laws governing single-use plastics. Standardizing MPs detection techniques, improving our knowledge of MPs fate and transport, and estimating the effects of MPs exposure to human health should be the main goals for future research. Effective cooperation between researchers, legislators, and industry is necessary for mitigation initiatives to be successful.

Adsorption of pentavalent vanadium and hexavalent chromium from vanadium extraction wastewater using modified diatomite

Vanadium extraction from vanadium (V) slag generates wastewater containing a large number of pentavalent vanadium [V (V)] and hexavalent chromium [Cr (VI)], posing environmental and health risks if discharged untreated. This study investigated the use of Fe2SO4 · 7H2O-modified diatomite as an adsorbent for removing V (V) and Cr (VI) from vanadium extraction wastewater (VEW). Static adsorption experiments were conducted to assess the adsorption capacity and removal efficiency of modified diatomite under varying conditions of adsorbent dosage, pH, and contact time. The results indicated removal rates of 97.4% for V (V) and 65.8% for Cr (VI) at pH 5, using 3 g of adsorbent dosage over 1440 min. In comparison with unmodified diatomite, the modified version exhibited a 667% increase in V (V) removal and a 531% increase in Cr (VI) removal, indicating significant enhancement in adsorption capacity post-modification. Adsorption capacity decreased with increasing dosage of modified diatomite. Moreover, the adsorbent under acidic conditions demonstrated superior adsorption effectiveness over neutral and alkaline conditions. Furthermore, the kinetics model revealed that adsorption followed Pseudo-second-order and Elovich kinetics, indicating chemisorption and complexation with active functional groups as dominant mechanisms. This study elucidated the effectiveness mechanisms of diatomite modification, paving the way for enhanced V (V) and Cr (VI) removal technologies in industrial wastewater treatment.

Application of microalgae in wastewater treatment with special reference to emerging contaminants: a step towards sustainability

Emerging contaminants includes diverse types of synthetic or natural chemical compounds which are not detected, monitored, or controlled in the environment regularly and are released from anthropogenic activities. Substantial quantities of emerging contaminants can be found in the wastewater, originating from agro-industrial and industrial outlets, containing oil and grease, heavy metals, and harmful chemicals. Different species of microalgae can be applied in biological remediation of such contaminants in wastewater. This research emphasizes the multifaceted roles of microalgae in wastewater treatment in context of pollutants, especially the removal of emerging contaminants. A comprehensive overview of different emerging contaminant removal processes was conveyed through an in-depth examination and depiction of the uptake mechanisms employed by microalgae in wastewater treatment in this review. The final section of this review focuses on the articulation of difficulties and prospects for the future of microalgae-based wastewater treatment technology. It is subsequently established how the microalgal technologies for emerging contaminant remediation can be helpful to achieve Sustainable Development Goals (SDGs). This review establishes the connection between phytoremediation technologies with Sustainable Development, and shows how successful implementation of such technologies can lead to the remediation of emerging contaminants and effective management of wastewater.

The Removal of Organic Pollutants and Ammonia Nitrogen from High-Salt Wastewater by the Electro-Chlorination Process and Its Mechanism

Electro-chlorination (E-Cl) is an emerging and promising electrochemical advanced oxidation technology for wastewater treatment with the advantages of high efficiency, deep mineralization, a green process, and easy operation. It was found that the mechanism of pollutant removal by electro-chlorination mainly involves an indirect oxidation process, in which pollutant removal is mainly driven by the intermediate active species, especially RCS and chlorine radicals, with a strong oxidization ability produced at the anodes. In this work, we summarized the principles and pathways of the removal/degradation of pollutants (organic pollutants and ammonia nitrogen) by E-Cl and the major affecting factors including the applied current density, voltage, electrolyte concentration, initial pH value, etc. In the E-Cl system, the DSA and BDD electrodes were the most widely used electrode materials. The flow-through electrode reactor was considered to be the most promising reactor since it had a high porosity and large pore size, which could effectively improve the mass transfer efficiency and electron transfer efficiency of the reaction. Of the many detection methods for chlorine radicals and RCS, electron paramagnetic resonance (EPR) and spectrophotometry with N, N-diethyl-1,4-phenylenediamine sulfate (DPD) as the chromogenic agent were the two most widely used methods. Overall, the E-Cl process had excellent performance and prospects in treating salt-containing wastewater.

Presence of Pharmaceutical Residues in the Seawater of Arctic Archipelago: Assessing the Potential Routes of the Pharmaceutical Pollution

The occurrence of seven commonly used pharmaceuticals, including diclofenac, fenoprofen, ketoprofen, ibuprofen, naproxen, carbamazepine, clofibric acid, gemfibrozil, estrone, 17β-estradiol, and 17α-ethynylestradiol, was investigated in the seawater of the Arctic during the summer of 2022. Seawater samples were subject to liquid-liquid extraction and solid-phase extraction (SPE). The concentrations of pharmaceuticals in the seawater samples were quantified with high-performance liquid chromatography (HPLC) and a DAD detector. The most abundant pharmaceuticals in the seawater were ibuprofen, with a range of 130-220 ng/L, and the highest concentration was obtained for 17α-ethynylestradiol with a level of 350 ng/L. We discussed possible reasons for pharmaceutical pollution, including the impact on marine species, the role of wastewater treatment technologies, and the potential long-range transportation of pharmaceutical residues via sea surface currents.

Emerging trends and future perspectives in adsorption technologies for water and wastewater treatment: A sunrise or sunset horizon?

Adsorption technology has been a focal point of water and wastewater treatment engineering research for over a century, yielding numerous scientific publications. These studies have primarily concentrated on developing efficient adsorbent materials, understanding adsorption mechanisms and characteristics, and investigating the removal of conventional or emerging pollutants. A common objective cited in most of these reports is the practical application of the adsorption process in municipal water or wastewater treatment plants, aiming to enhance water quality and safety. However, the majority of these studies overlook issues related to technology transfer, thereby widening the gap between academic recommendations and their practical implementation in industry. In this review, we trace the evolution of adsorption technology in water and wastewater treatment, evaluating its application viability and highlighting the approaches that hold the greatest promise for the future. Furthermore, we propose strategies for scientists and engineers dedicated to advancing research efforts that translate into industrially viable adsorption technologies for water treatment. While the practical effectiveness of adsorption technologies may not fully align with academic enthusiasm, this critical evaluation should not dismiss their potential as future technology since adsorption retains significant and distinct advantages that merit further exploration.

Sustainable Technology for Wastewater Treatment and Climatic Change Mitigation using an Innovative Vermifiltration Approach

Sustainable Technology for Wastewater Treatment and Climatic Change Mitigation using an Innovative Vermifiltration Approach

Ecological restoration orientated application and modification of constructed wetland substrates.

Constructed wetlands (CWs) have gained recognition as an environmentally friendly and cost-efficient option for treating municipal, industrial, and agricultural wastewater. They treat wastewater by harnessing the combined action of physical, chemical, and biological processes within substrates, plants, and microorganisms, with substrates exerting the greatest influence on the life cycle and purification efficiency of the system. This review provides an in-depth discussion on the development and performance of various substrate types used in CWs, including natural materials, ore-based materials, biomass materials, waste materials, and modified and novel materials. Key substrate modification techniques are summarized in detail, such as acid-base treatment, metal doping, compound modification, and heat treatment, which enhance structural and functional properties to improve pollutant removal. The paper also systematically explores the mechanisms of introducing methods like inorganic electronic enhancement and describes their applications in improving pollutant removal in CW systems. This review provides a holistic evaluation of substrate classification and optimization strategies and a prospective discussion of their challenges and opportunities in practical applications. It contributes to the creation of more efficient and sustainable materials for CW systems and provides theoretical support for selecting and optimizing substrates, thereby driving progress in wastewater treatment technology.

Column Experiment of a Single-Stage Multi-Soil-Layering System with Horizontal Flow

A multi-soil-layering system (MSL) is a biphasic soil-based wastewater treatment technology. In this study, two MSL columns with different soil mixture block (SMB) thicknesses were fed synthetic wastewater and monitored (i.e., organic matter and nutrients) to investigate the treatment performance of MSLs with horizontal flow (HF) orientation. The average removal efficiencies for System 1 (small SMBs) were 54%, 69%, 79%, 99%, and 95% for COD, TP, TN, NH3-N, and NO3--N, respectively, and 45%, 80%, 75%, 98%, and 85% for System 2 (large SMBs). The results suggest the primary function of SMBs in HF-MSLs is to provide phosphorous treatment. For nitrogen, unlike what has been found in other vertical flow (VF) MSL studies, denitrification was not a limiting factor. It is hypothesized (a) nitrification was facilitated by the permeable layer (PL, zeolite) and (b) the saturated conditions inherent to HF-MSLs promoted the growth of a heterogenous PL biofilm, proliferating denitrifying microorganisms. Based on the literature, it is theorized that organic matter (COD) removal was likely inhibited by the combination of competing bacterial species, insufficient aeration, a high influ-ent C/N ratio (12:1), and a relatively low HRT (~ 3 hrs). Overall, the bench scale removal efficiency results produced show the HF-MSL systems tested perform comparatively with VF-MSLs in addition to providing complete nitrogen removal. The findings from this intro-ductory investigation suggest HF-MSLs warrant further study. More research is needed (e.g., biological assessment) to validate the inter-pretations presented herein.

Development of complex wastewater treatment of galvanizing lines

The prospective of increasing of environmental safety level for industrial enterprises as a result of the implementation of new complex wastewater treatment technology are considered. An analysis of literary sources was carried out regarding the effectiveness of the existing methods of wastewater treatment that contain compounds of heavy metals. The efficiency of iron ion extraction was investigated by processing of steel pickling solutions using the ferritization with various activation methods of the reaction mixture. X-ray phase analysis of the obtained ferritization sediments confirmed the presence of highly dispersed ferromagnetic phases of iron oxides and oxyhydroxides. The sorption capacity of magnetite sediment obtained by ferritization on the efficiency of zinc ion extraction from the wastewater of the galvanic line was studied. The influence of pH value and ultrasound on sorption treatment of washing wastewater by magnetite sediment was determined. When using ultrasound for sorbent treatment and raising the pH to 10, the residual concentration of zinc ions in the washing wastewater decreases to 0.31 mg/dm3, the degree of purification is 98.9%. Such water meets the standards for its use in the operations of washing parts at electroplating facilities or discharge into the city's central sewage system. The prospects for the utilization of spent sorbents in powder paint and varnish materials as a result of the inclusion in their composition of ferritization products obtained from electroplating waste are considered. The use of ferromagnetic waste from sorption treatment improves the corrosion resistance of the resulting coatings compared to traditional ones. The implementation of research results at enterprises will prevent environmental pollution by toxic substances, change outdated production technologies and obtain from production waste materials for corrosion protection of metal construction.