Wastewater Treatment Methods Research Articles

Implications of the operation of continuous granular activated carbon filters on the effluent quality.

Granular activated carbon (GAC) filtration is a commonly used method for advanced wastewater treatment. Filters can be operated continuously or discontinuously, with continuous operation not requiring feed flow interruption for backwashing and circulation (B/C). This study investigated the influence of B/C on the effluent quality of continuous filters. Two continuous GAC filters were operated for 1.5 years, with analysis of dissolved substances and particulate matter in the influent and effluent. The results indicated that various B/C modes had no impact on the removal of dissolved organic carbon and organic micropollutants (OMP), achieving an OMP removal of over 70% after 5,600 treated bed volumes (m3 treated wastewater per m3 GAC). However, it was evident that continuous B/C over 2-4 h resulted in increased turbidity, total suspended solids over 30 mg/L and total phosphorus concentrations of 1.3 mg/L in the filter effluent. Additionally, the study demonstrated that longer and more intensive B/C processes resulted in GAC size degradation with AC concentrations of up to 6.9 mg/L in the filter effluent, along with a change in GAC particle size. Furthermore, the importance of pre-filtration in reducing particulate matter in the filter influent and decreasing hydraulic head loss could be demonstrated.

Catalytic air oxidation of biogas slurry using Cu sub-nanocluster supported by mesoporous TiZrO4 and protected by SiO2 shell

Biogas slurry, an inevitable outcome of anaerobic digestion (AD), is a treatment burden for urban environmental management. In this study, two kinds of biogas slurry (slurry J and slurry C), collected from the AD plants in Japan and China, were treated using novel TiZrO4 @Cu and TiZrO4 @Cu@SiO2 multilayered hollow spheres containing Cu sub-nanoclusters as the catalyst. The results showed that the chemical oxygen demand (COD) was removed by 63 % for slurry J and 44 % for slurry C after 5 h. The Cu sub-nanoclusters acted as co-catalysts and active centers, facilitating rapid electron transfer to oxygen molecules and forming highly reactive •O2− and •OH species (Use slurry J as the based solution). These free radicals cleaved the interconnecting bonds between benzene rings, disintegrated the ring structure, formed intermediate compounds such as n-hexylic acid, and ultimately mineralized organic pollutants in biogas slurry into CO2 and H2O. At the same time, TiZrO4 @Cu@SiO2 had excellent stability due to the protection of the SiO2 shell and reduced threefold Cu leaching than TiZrO4 @Cu. The COD removal rate was always 60 % in six cycles in the slurry J. The new catalyst ensured the high performance of catalytic air oxidation at low temperatures, which has significant potential as an environmentally friendly and energy-saving method for organic wastewater treatment.

Overview of treatment methods of tannery wastewater

Overview of treatment methods of tannery wastewater

A Descriptive Study on Performance Evaluation of Sewage Treatment System

Abstract: As The rapid expansion of modern housing and industrialization around the cities has polluted environment. This trend was observed in many developed countries in the beginning of nineteenth century which resulted in the contamination of air, water, soil etc. with pollutants. If the pollutants are released in the environment and left untreated they would cause serious diseases in both humans and animals. Large scale pollution of water bodies around the globe became a major problem due to release of industrial and domestic waste directly in water streams. To prevent the leaching of pollutants in the ground water scientist developed various methods of wastewater treatment based on the hazardous chemicals and microorganisms, which were present in the untreated water. Modern sewage treatment plants were installed in big cities to treat the water released from households. Most STPs were designed based on the stringent criteria to check the pollutants levels in the treated water so that when it is released or recycled it is safe to the environment. Modern day STP plants have a high cost of operation due to huge power consumption. In order to reduce the pollutant levels in the wastewater this study was conducted using a Eco Bio Block (EBB) techniques with aeration and without aeration. A comparison of EBB was also carried out with MBBR technique. Our results show that when EBB technique was applied with aeration it is effective in reducing pollutant levels in the wastewater akin to MBBR. In addition, we tested the EBB without aeration and found that the treated waste water has relatively low levels of BOD, COD and turbidity, suggesting that the treated water can be utilized for landscaping and horticulture activities. Overall, the outcomes from this study are encouraging to adopt EBB in smaller towns and in small housing societies to treat the wastewater prior to release. The paper focuses on reviewing the various sewage treatment methods and their results.

Inaccessible and Unaffordable? The State of Water and Sanitation Services in Nairobi, Kenya

As the limited water resources become increasingly stressed by factors such as rapid urbanization, population growth, and climate change, the need for sustainable urban water management is more important than in the past decades. A large part of the world’s population still lacks access to clean water and sanitation, making achieving Sustainable Development Goals a challenge. Water is an indispensable resource and plays an important role in ensuring the achievement of Sustainable Development Goals. Therefore, there is a need to prioritize research on the availability, affordability, and access of water resources to promote sustainable water resource management. In this study, we reviewed academic articles and published reports from various institutions and organizations to assess water sources, infrastructure, coverage, accessibility, and affordability of water and sanitation services in Nairobi County. The study identified Nairobi’s main water sources as municipal water, primarily from surface water and groundwater. However, the capacities of the water sources, treatment plants, and wastewater treatment plants were found to be insufficient, resulting in water shortages in most parts of the city.Most of the infrastructures were also found to be insufficient and old, contributing to water distribution inefficiencies, frequent leakages, and pipe bursts which hampers water reliability. The study suggests prioritizing the water and sanitation sector in government budgets to increase infrastructure development investments and funding. Appropriate wastewater treatment methods should also be adopted and implemented to enable wastewater to meet water consumption standards and be potentially integrated into supply systems.

Efficient Low-Temperature Nutrient Removal from Agricultural Digestate Using Microalgae

Humanity is facing an energy crisis triggered by the depletion of fossil fuels, rapid industrialization, and the growthof the global population. These trendsput an emphasis on searching for alternative energy sources. Additionally, the rising concentration of carbon dioxide in the atmosphere is driving climate change, which poses serious threats. In this scenario, microalgae emerge as a promising solution for both sustainable energy production and CO2 sequestration. Digestate, a nutrient-rich by-product of anaerobic digestion, is considered a cost-effective nutrient source for microalgae cultivation. Utilizing digestate not only enhances the sustainability and economic feasibility of microalgal biofuels but also offers a method for wastewater treatment. Nevertheless, the application of digestate is limited by its high optical density and substantialamount of total solids.In this study, several pretreatment methods were tested to increase the feasibility of digestate application for microalgae cultivation. Our findings show that various centrifugation methods and vacuum filtration decrease the content of total solids but are not effective in reducing optical density. Although the use of microalgae in treating various wastewaters has shown promising outcomes, the effectiveness of nutrient removal at low temperatures remainslargely unexplored.To fill this gap, green microalga Chlorella sorokiniana was cultivated in pretreated diluted liquid digestate in dynamic springtime weather conditions in a covered open race-way pond integrated into a biogas plant.During the cultivation, high solar irradiance and low temperatures were recorded resulting in suboptimal conditions for C. sorokinianagrowth. Although low productivity of C. sorokiniana was detected, the nutrient removal efficiency was high. C. sorokiniana could efficiently remove 83% of nitrogen and 85% of phosphorus showing very promising results of the use of microalgae for wastewater treatment in high latitude regions.

Recent advances and challenges of the green ZnO-based composites biosynthesized using plant extracts for water treatment.

Recently, there has been a notable rise in the prevalence of persistent pollutants in the environment, posing a significant hazard due to their toxicity and enduring nature. Conventional wastewater treatment methods employed in treatment plants rarely address these persistent pollutants adequately. Meanwhile, the concept of green synthesis has garnered considerable attention, owing to its environmentally friendly approach that utilizes fewer toxic chemicals and solvents. The utilization of materials derived from sustainable sources presents a promising avenue for solving pressing environmental concerns. Among the various sources of biological agents, plants stand out for their accessibility, eco-friendliness, and rich reserves of phytochemicals suitable for material synthesis. The plant extract-mediated synthesis of zinc oxide nanoparticles (ZnONPs) has emerged as a promising solution for applications in wastewater treatment. Thorough investigations into the factors influencing the properties of these green ZnONPs are essential to establish a detailed and reliable synthesis process. Major weaknesses inherent in ZnONPs can be addressed by changing the optical, magnetic, and interface properties through doping with various semiconductor materials. Consequently, research efforts to mitigate water pollution are being driven by both the future prospects and limitations of ZnO-based composites. This review underscores the recent advancements of plant extract-mediated ZnONP composites for water treatment.

Progress of Dye Wastewater Treatment Methods

Progress of Dye Wastewater Treatment Methods

Bio-electrochemical degradation of carbamazepine (CBZ): A comprehensive study on effectiveness, degradation pathway, and toxicological assessment

Recent attention on the detrimental effects of pharmaceutically active compounds (PhACs) in natural water has spurred researchers to develop advanced wastewater treatment methods. Carbamazepine (CBZ), a widely recognized anticonvulsant, has often been a primary focus in numerous studies due to its prevalence and resistance to breaking down. This study aims to explore the effectiveness of a bio-electrochemical system in breaking down CBZ in polluted water and to assess the potential harmful effects of the treated wastewater. The results revealed bio-electro degradation process demonstrated a collaborative effect, achieving the highest CBZ degradation compared to electrodegradation and biodegradation techniques. Notably, a maximum CBZ degradation efficiency of 92.01% was attained using the bio-electrochemical system under specific conditions: Initial CBZ concentration of 60 mg/L, pH level at 7, 0.5% (v/v) inoculum dose, and an applied potential of 10 mV. The degradation pathway established by identifying intermediate products via High-Performance Liquid Chromatography-Mass Spectrometry, revealed the complete breakdown of CBZ without any toxic intermediates or end products. This finding was further validated through in vitro and in vivo toxicity assays, confirming the absence of harmful remnants after the degradation process.

Hydrothermal synthesis of high crystallinity ZSM-5 zeolite from coal gasification coarse slag and mother liquor circulation for efficient coal chemical wastewater purification.

A hydrothermal synthesis method was developed to produce high crystallinity ZSM-5 zeolite using coal gasification coarse slag (CGCS) as the raw material. Instead of the expensive NaOH(s.), Na2SiO3(s.) was utilized to activate, depolymerize, and recombine Si and Al elements in the CGCS. The mother liquor circulation technology was employed to recover and reuse raw materials and residual reagents (Na2SiO3(aq.) and TPABr), reducing waste emissions and enhancing resource utilization efficiency. The synthesized ZSM-5 had a specific surface area of 455.675 m2g-1, pore volume of 0.284 cm3g-1, and pore diameter of 2.496nm. The influence of various factors on the morphology and crystallinity of ZSM-5 was investigated, resulting in the production of ZSM-5 with higher specific surface area and pore volume. Adsorption experiments showed that WU-ZSM-5 exhibited a removal efficiency of 85% for ammonia nitrogen (NH4+-N(aq.)), validating its effectiveness in coal chemical wastewater purification. The mother liquor recycling technology enabled zero-emission utilization of solid waste resources and improved the utilization rate of alkali and template to 90%. These results demonstrate the potential application of the developed method in the efficient treatment of coal chemical wastewater.

Enhanced Low-Energy Chemical Oxygen Demand (COD) Removal in Aeration-Free Conditions through Pulse-Rotating Bio-Contactors Enriched with Glycogen-Accumulating Organisms

This study presents an innovative pulse-rotating biological contactor (P-RBC) designed to enrich glycogen-accumulating organisms (GAOs), thereby facilitating low-energy chemical oxygen demand (COD) removal. It then investigates the impact of rotational speed and hydraulic retention time (HRT) on GAO enrichment and COD removal efficiency. Optimized conditions at lower speeds and longer HRTs significantly enhance GAO proliferation and Polyhydroxyalkanoate (PHA) synthesis, the key to COD removal. Noteworthy findings include a maximum GAO abundance of 21.34% at a half round per hour (rph) rotating speed, which correlates with a 90.2% COD removal rate and an HRT of 6 h, yielding a 21.23% GAO abundance and 89.8% COD removal. This study also explores various carbon sources for PHA synthesis, with sodium acetate proving the most effective. Compared to other wastewater treatment methods, P-RBC demonstrates minimal energy consumption (0.09 kWh per ton of wastewater), highlighting its potential as a sustainable and effective approach for wastewater treatment.

Preparation of Newly Polymer-Coated Microbial Pellets and Their Adsorption and Degradation Properties for Oil-Containing Wastewater.

Water is the lifeblood of everything on earth, nourishing and nurturing all forms of life, while also contributing to the development of civilization. However, with the rapid development of economic construction, especially the accelerated process of modern industrialization, the pollution of oily sewage is becoming increasingly serious, affecting the ecological balance and human health. The efficient elimination of pollutants in sewage is, therefore, particularly urgent. In this paper, a core-shell microbial reactor (MPFA@CNF-SA-AM) was fabricated by using nanocellulose and sodium alginate (SA) particles embedded with microorganisms as the core and lipophilic and hydrophobic fly ash as the outer shell layer. Compared with that of free microorganisms and cellulose and SA aerogel pellets loading with microorganisms (CNF-SA-AM), which has a degradation efficiency of 60.69 and 82.89%, respectively, the MPFA@CNF-SA-AM possesses a highest degradation efficiency of 90.60% within 240 h. So that this self-floating microbial reactor has selective adsorption properties to achieve oil-water separation in oily wastewater and high effective degradation of organic pollutants with low cost. The adsorption curves of MPFA@CNF-SA-AM for diesel and n-hexadecane were studied. The results showed that the adsorption follows the Freundlich model and is a multimolecular layer of physical adsorption. In addition, the degradation mechanism of diesel oil was studied by gas chromatography-mass spectrometry. The results showed that diesel oil was selectively adsorbed to the interior of MPFA@CNF-SA-AM, and it was degraded by enzymes in microorganisms into n-hexadecanol, n-hexadecaldehyde, and n-hexadecanoic acid in turn, and finally converted to water and carbon dioxide. Compared with existing oily wastewater treatment methods, this green and pollution-free dual-functional core-shell microbial reactor has the characteristics of easy preparation, high efficiency, flexibility, and large-scale degradation. It provides a new, effective green choice for oily wastewater purification and on-site oil spill accidents.

Simulation and Experimental Study of Circulatory Flash Evaporation System for High-Salt Wastewater Treatment

Treatment methods for high-salt wastewater mainly consist of physical methods, chemical methods and biological methods. However, there are some problems, such as slow treatment speed, high investment costs and low treatment efficiency. To address NaCl solutions, in this study, a circulatory flash system was designed based on gas–liquid equilibrium, mass conservation equation and energy conservation equation. A circulatory flash evaporation simulation and a static flash evaporation experiment were conducted on NaCl solutions under various operating conditions to investigate the effects of heating temperature, flash pressure and initial NaCl concentration on the circulatory flash evaporation system. The significance of each factor’s influence on the evaporation fraction and energy consumption was examined through static flash experiments. The simulation results demonstrated that increasing the heating temperature, decreasing the flash pressure and having a higher initial NaCl concentration could enhance the treatment capacity of high-salt wastewater. The flow rate of vapor outlets increased with higher heating temperature but decreased as the flash pressure rose. The experimental results demonstrated that flash evaporation pressure was the primary factor influencing both the evaporation fraction and the energy consumption per unit mass of vapor produced. It was observed that with an increase in heating temperature, the flash pressure decreased and there was a corresponding decrease in energy consumption per unit mass of vapor produced. The optimal experimental conditions were achieved at a heating temperature of 99 °C, a flash pressure of 15 kPa, and an initial NaCl concentration of 20%.

Novel silver vanadate coupled semiconductor nanocomposites for effective removal of toxic organics

One of the world's most important challenges is the lack of access to clean water, and researchers are working tirelessly to find a solution. Nanotechnology-treated water is superior to conventionally treated water since it contains no hazardous microorganisms or organic dyes. In this study, the influence of light on Ag3VO4 nanocomposites doped with synthesized ZnO nanoparticles was analyzed. SEM, FTIR, XRD, XPS, and UV–vis spectroscopy were just some of the methods used to characterize the as-prepared nanocomposites. An Ag3VO4/ZnO nanocomposite was used to successfully adsorb and photodegrade Acid Green-16(AG-16), and Acid Red-72(AR-72) from an aqueous solution. Visible light dramatically accelerates the adsorption and photodegradation of the Ag3VO4/ZnO nanocomposite compared to complete darkness. 77.52 %, 82.86 %, and 89.56 % of AG-16 and 77.11 %, 82.74 %, and 87.91 % of AR-72 were removed by the ZnO, Ag3VO4, and Ag3VO4/ZnO nanocomposites, respectively, in less than 60 min. However, visible-light photodegradation is more successful than adsorption alone in removing AG-16 and AR-72. In this pioneering study, we assess the catalytic performance of newly synthesized ZnO incorporated Ag3VO4 nanocomposites for the UV-assisted degradation of organic dyes. Our study presents an innovative catalyst system that exhibits improved efficiency and holds promise for implementation in environmentally sustainable wastewater treatment methods.

Preparation, characterization, and photocatalytic performance of atmospheric plasma-sprayed TiO2/Al2O3 coatings on glass substrates

Conventional methods for wastewater treatment are not always efficient in persistent organic pollutant degradation processes. Therefore, low-cost and effective methods of their removal from sewage are constantly sought. This study presents an attempt to fabricate thermally sprayed ceramic coatings on glass and their characterization. Granulation of TiO2, Al2O3, and their blends in different mass ratios was done. Assessment of actual density and specific surface area was performed, and TiO2, Al2O3, and TiO2/Al2O3 were then used as a coating material for the deposition on glass substrates in atmospheric plasma spraying. Surface analysis of coatings was done by evaluating their roughness and wettability. Both powder and coatings samples were characterized using the X-ray diffraction method and scanning electron microscopy. The photocatalytic activity was estimated in the Eosin Y degradation process under UV light. UV–Vis spectroscopy was applied to observe the changes in the dye concentration. Additional tests for color measurements before and after photodegradation were carried out using a sphere spectrophotometer in CIELab color space. Particle size distribution was examined for the powder samples after the granulation and d50 was stated at 48.42–63.28 µm. Characterization of coatings via roughness measurements showed the average roughness of a surface equal to 4.90–9.65 µm. Moreover, most of the coatings appeared to be hydrophobic with water contact angles between 100° and 130°. All of the coatings showed Eosin Y degradation ability and the highest efficiency was reached for 100T/C, A75T/C, and A50T/C samples and stated at 71%, 62%, and 51%, respectively.Graphical abstract

Natural mineral raw materials as granular filtering materials in industrial and waste water treatment

Analysis of currently existing methods of natural and waste water treatment from heavy metals has shown that one of the most promising is the sorption method using natural inorganic materials as sorbents: zeolite, diatomite, and vermiculite. The relevance of the topic is dictated by the need to develop an original technology of wastewater treatment and water treatment, which allows constant monitoring of the level of pollution of natural waters by industrial wastewater from metallurgical enterprises. The proposed methods of sorbent modification create a basis for studying the structure, porosity, and sorption capabilities of the mentioned natural materials. All three minerals: zeolite, diatomite, and vermiculite belong to highly porous, structured materials, promising for use as stable sorption systems in water treatment and water purification. The influence of physical and chemical characteristics of natural sorbents and the application of new promising environmentally safe materials and reagents for water treatment are considered. The sorption of copper ions on natural zeolite material before and after its modification by hydrothermal method was investigated. The activity of sorbents was estimated by the value of sorption capacity, i.e. the amount of heavy metal ions absorbed by a unit mass of sorbent based on zeolite and its modified form.

Multifunctional g-C3N4-PDI/MOF-545-NH2 photocatalyst for Enhanced CO2 reduction and aniline oxidation

The use of solar energy to convert CO2 into clean energy is one of the ideal strategies for achieving carbon neutrality. However, the rapid recombination of photogenerated electron holes, the complexity of the reduction products and the consumption of sacrificial materials severely limit its development and application. In this work, g-C3N4-PDI (CNP) and MOF-545-NH2 (MNH) were prepared by calcination and hydrothermal methods, respectively, and CNP/MNH photocatalysts were prepared by in situ growth of MNH on CNP surface. The photocatalytic CO2 conversion reaction of CNP/MNH in triethanolamine and aniline solutions was investigated. Experiments show that the prepared CNP/MNH catalyst has excellent photocatalytic performance. When triethanolamine was used as a sacrificial agent, the yield of CH4 reached 192.7 μmol·g−1·h−1 (selectivity 92.94 %). In particular, while the catalyst realizes the conversion of CO2 in the aniline solution, it is surprising to find that part of the CO2 is converted to ethanol. The catalyst’s photochemical properties, CO2 reduction pathway, and aniline oxidation products were characterized by XPS, UV–vis DRS, PL, electrochemistry, zeta potential, ESR, GC–MS and in-situ infrared spectroscopy. The results show that the modification of the catalyst and the formation of heterojunction not only increase the adsorption of CO2, but also accelerate the process of photogenerated electron migration, which plays an important role in the process of carbon dioxide conversion. This study provides a new perspective for the design of photocatalytic CO2 conversion catalysts, and also provides a feasible method for aniline wastewater treatment.

Invasive lignocellulose-based plants bio-sorbents for the elimination of nitrites of emerging concern from water

The regulation of nitrite levels in potable water is primarily motivated by the potential for excessive amounts to induce methemoglobinemia, which is also referred to as blue baby syndrome. Human and industrial activities generate and release nitrite-containing wastewater into water bodies, thereby endangering ecosystem health and contaminating water sources. Biosorption is an alternative and environmentally beneficial method of wastewater treatment. These methods have several advantages over conventional methods, including their cost-effectiveness, accessibility, and reusability. This study investigates the viability of utilizing guava leaf, neem leaf, orange peel, banana peel, and custard apple leaf as bio-sorbents for the removal of nitrite from contaminated water. One hundred percent removal efficiency is the result of this endeavor. Following an examination of all six bio-sorbents, it was observed that the guava leaf bio-sorbents exhibited the most effective performance in the removal of nitrite from water. Additionally, the impacts of various parameters including contact duration, agitation speed, adsorbent dosage, pH, and temperature are also investigated. Additionally, prior to utilization, the biomass may undergo physical and chemical modifications. To enhance the analysis of each bio-sorbent, a range of characterization techniques are utilized, including XRD, SEM-EDX, FTIR, and BET analysis. Economic feasibility can be achieved by regenerating and reprocessing the bio-sorbent subsequent to the nitrites removal process.

Investigating a batch-flow photocatalytic LED system for diclofenac removal in wastewater treatment plants: Assessing the influence of reaction conditions on photocatalytic efficiency

This work introduces an innovative batch-flow photocatalytic LED system aimed at efficiently removing diclofenac from wastewater. The study highlights the novelty of fabricating TiO2-loaded carbon fiber photocatalysts through a hydrothermal process, exhibiting a blue shift in their absorption spectrum and enhancing their photon absorption capability. A crucial design feature is the spectral matching between the LED light source and the photocatalyst, which is critical for achieving high photodegradation efficiency. A significant innovation of our study is the testing of the system under real conditions at an operational sewage treatment plant. Here, the designed system demonstrated high efficacy in degrading diclofenac across various treatment stages, highlighting its robustness and adaptability to changing environmental conditions. The highest degradation efficiency was achieved with sewage from the secondary settling tank, where nearly 90 % efficiency was observed after 6 h of irradiation. Moreover, the use of renewable energy sources emphasizes the system's sustainability, presenting a greener alternative to traditional wastewater treatment methods. The investigation not only showcases the system's effectiveness in diclofenac degradation but also its adaptability and stability under real-world conditions, marking a significant advancement in sustainable wastewater treatment technologies.

Life cycle assessment and techno-economic analysis of nanotechnology-based wastewater treatment: Status, challenges and future prospectives

BackgroundWater pollution is a pressing concern stemming from both natural and anthropogenic activities. The challenges associated with water treatment technologies are adsorption (fouling and corrosion of the adsorbent), flocculation (increased sludge generation and high operation cost), ion exchange (high cost and improper ion removal), chemical precipitation (sludge generation), and membrane technologies (membrane fouling and storage). These technologies have been overstretched and struggle to meet increasingly stringent water quality standards. More recent progress has been made in using nanotechnology for wastewater treatment. Nano-technology offers several advantages over traditional technologies. Many nano-based technologies support reuse, require less space, produce fewer toxic intermediates, and are adaptable to support the emerging concept of decentralized water treatment. An essential aspect of this review is a detailed techno-economic analysis, assessing the long-term viability of nanotechnology-based wastewater treatment methods from an economic standpoint. MethodsThis review outlines the current state of nanotechnology in wastewater treatment, addressing environmental and economic aspects, challenges, and future potential. Significant findingsUnderstanding the sustainability and feasibility of these innovative technologies is crucial for their successful integration into wastewater treatment practices, ensuring a more effective and environmentally friendly approach to water remediation.