Magnesium oxide(MgO)nanoadsorbents in wastewater treatment:A comprehensive review

Wastewater contamination by heavy metals and synthetic dyes presents a significant environmental challenge,necessitating effective and sustainable separation techniques.This review article provides a detailed examination of magnesium oxide(MgO)nanoparticles as an innovative nanoadsorbent for wastewater treatment,with a specific focus on heavy metal and dye removal.The review comprehensively explores various aspects of MgO nanoparticles,including their structural characteristics and synthesis techniques.The article delves into the morphology and crystallographic arrangement of MgO nanoparticles,offering insights into their structural attributes.Given the complexity of adsorption processes,the review identifies and analyzes parameters influencing the adsorption efficiency of MgO nanoparticles,such as temperature,pH,contact time,initial concentration,and co-existing ions.The interplay between these parameters and the adsorption capability of MgO nanoparticles emphasizes the importance of optimizing operational conditions.Furthermore,the review assesses various synthesis methods for MgO nanoparticles,including sol-gel,hydrothermal,precipitation,green synthesis,solvothermal,and template-assisted techniques.It discusses the advantages,limitations,and resulting nanoparticle characteristics of each method,enabling readers to grasp the implications of synthesis processes on adsorption efficiency.This comprehensive review consolidates current insights into the effectiveness of MgO nanoparticles as a potent nanoadsorbent for removing heavy metals and dyes from wastewater covering a wide spectrum of aspects related to MgO nanoparticles.Moreover,there is a need to investigate the use of MgO in the treatment of actual wastewater or river water,in order to leverage its cost-effectiveness and high efficiency for practical water treatment applications in real-time.

Cloud-Model-Based Feature Engineering to Analyze the Energy-Water Nexus of a Full-Scale Wastewater Treatment Plant

Wastewater treatment plants(WWTPs)are important and energy-intensive municipal infrastructures.High energy consumption and relatively low operating performance are major challenges from the perspective of carbon neutrality.However,water-energy nexus analysis and models for WWTPs have rarely been reported to date.In this study,a cloud-model-based energy consumption analysis(CMECA)of a WWTP was conducted to explore the relationship between influent and energy consumption by clustering its influent’s parameters.The principal component analysis(PCA)and K-means clustering were applied to classify the influent condition using water quality and volume data.The energy consumption of the WWTP is divided into five standard evaluation levels,and its cloud digital characteristics(CDCs)were extracted according to bilateral constraints and golden ratio methods.Our results showed that the energy consumption distribution gradually dispersed and deviated from the Gaussian distribution with decreased water concentration and quantity.The days with high energy efficiency were extracted via the clustering method from the influent category of excessive energy consumption,represented by a compact-type energy consumption distribution curve to identify the influent conditions that affect the steady distribution of energy consumption.The local WWTP has high energy consumption with 0.3613 kW·h·m^(-3)despite low influent concentration and volumes,across four consumption levels from low(I)to relatively high(IV),showing an unsatisfactory operation and management level.The average oxygenation capacity,internal reflux ratio,and external reflux ratio during high energy efficiency days recognized by further clustering were obtained(0.2924-0.3703 kg O_(2)·m^(-3),1.9576-2.4787,and 0.6603-0.8361,respectively),which could be used as a guide for the days with low energy efficiency.Consequently,this study offers a water-energy nexus analysis method to identify influent conditions with operational management anomalies and can be used as an empirical reference for the optimized operation of WWTPs.

Multimodal Machine Learning Guides Low Carbon Aeration Strategies in Urban Wastewater Treatment

The potential for reducing greenhouse gas(GHG)emissions and energy consumption in wastewater treatment can be realized through intelligent control,with machine learning(ML)and multimodality emerging as a promising solution.Here,we introduce an ML technique based on multimodal strategies,focusing specifically on intelligent aeration control in wastewater treatment plants(WWTPs).The generalization of the multimodal strategy is demonstrated on eight ML models.The results demonstrate that this multimodal strategy significantly enhances model indicators for ML in environmental science and the efficiency of aeration control,exhibiting exceptional performance and interpretability.Integrating random forest with visual models achieves the highest accuracy in forecasting aeration quantity in multimodal models,with a mean absolute percentage error of 4.4%and a coefficient of determination of 0.948.Practical testing in a full-scale plant reveals that the multimodal model can reduce operation costs by 19.8%compared to traditional fuzzy control methods.The potential application of these strategies in critical water science domains is discussed.To foster accessibility and promote widespread adoption,the multimodal ML models are freely available on GitHub,thereby eliminating technical barriers and encouraging the application of artificial intelligence in urban wastewater treatment.

Digital Twins for Wastewater Treatment:A Technical Review

The digital twins concept enhances modeling and simulation through the integration of real-time data and feedback.This review elucidates the foundational elements of digital twins,covering their concept,entities,domains,and key technologies.More specifically,we investigate the transformative potential of digital twins for the wastewater treatment engineering sector.Our discussion highlights the application of digital twins to wastewater treatment plants(WWTPs)and sewage networks,hardware(i.e.,facilities and pipes,sensors for water quality and activated sludge,hydrodynamics,and power consumption),and software(i.e.,knowledge-based and data-driven models,mechanistic models,hybrid twins,control methods,and the Internet of Things).Furthermore,two cases are provided,followed by an assessment of current challenges in and perspectives on the application of digital twins in WWTPs.This review serves as an essential primer for wastewater engineers navigating the digital paradigm shift.

Ecological Wastewater Treatment System in a School Environment Using a Horizontal Flow Biological Reactor: The Case of Typha

The overarching goal of this study is to offer an effective and sustainable solution to the challenges of sanitation in rural and school settings in the northern region of Senegal. The study explores a wastewater treatment approach based on phytoremediation, with a particular focus on the use of horizontally-flowing reed bed filters. Furthermore, it aims to adapt and optimize these systems for the specific needs of Senegal, focusing on wastewater in school environments. Thus, we constructed a horizontally-flowing reed bed filter, planted with Typha, at the Ndiébène Gandiol school in Senegal. We will investigate the efficiency of wastewater treatment by this horizontally-flowing reed bed filter, emphasizing the role of the plant used: Typha. The filter is described in detail, specifying its dimensions, its composition of flint gravel, and the choice of plants, namely Typha. The experimental protocol is detailed, describing the sampling at the entrance and exit of the filter to evaluate water quality. The parameters analyzed include Chemical Oxygen Demand (COD), Biochemical Oxygen Demand over 5 days (BOD5), suspended solids, ammonium, nitrates, phosphates, pH, conductivity, and fecal coliforms. The results indicate a significant improvement in water quality after treatment. COD, BOD5, suspended solids, and fecal coliforms are greatly reduced, thus demonstrating the efficacy of the Typha filter. However, nitrate concentrations remain relatively stable, suggesting room for improvement in their elimination. A perspective of reuse of the treated water is considered, showing that the effluents from the planted filter meet Senegalese and international standards for irrigation. The findings suggest that these waters could be used for a variety of crops, thereby reducing the pressure on freshwater resources. In conclusion, the Typha-based filtration system shows promising results for improving water quality in this region of Senegal. However, adjustments are necessary for more effective nitrate removal. This study paves the way for sustainable use of treated wastewater for irrigation, thus contributing to food security and the preservation of water resources.

Ecological Wastewater Treatment System Using a Horizontal Flow Biological Reactor: The Case of Vetiver

Confronted with the challenge of wastewater management, particularly in the school environment of Senegal, our study set out to achieve multiple objectives. Following field surveys, laboratory analyses of wastewater samples were carried out, revealing a significant pollutant load. In the community of Gandiol, near Saint-Louis (Senegal), the school of Ndiebene Gandiol 1 faces significant sanitation challenges. Our study aimed to address this issue by using a constructed filter composed of two filtering bed cells measuring 12 × 8.5 m, preceded by a septic tank. We particularly focused on the influence of Vetiver;a plant chosen for its purification potential. Our analyses showed remarkable efficiency of the filter. Elimination rates reached 95% for 5-Day Biochemical Oxygen Demand (BOD5), 91% for Chemical Oxygen Demand (COD), and 92% for SS, far exceeding the Senegalese standards set at 50 mg/L, 200 mg/L, and 40 mg/L, respectively. Furthermore, the concentration of fecal coliforms was reduced to 176 FCU/100mL, well below the Senegalese threshold of 2000 FCU/100mL and close to the World Health Organization’s (WHO) recommendation of 1000 FCU/100mL. However, despite these promising results, some parameters, particularly the concentration of certain pollutants, approached the thresholds defined by European legislation. For example, for Suspended Solids (SS), the post-treatment level of 3 mg/L was well below the Senegalese standard but edged close to the European minimum of 10 mg/L. In conclusion, the Vetiver filter demonstrated a remarkable ability to treat school wastewater, offering high pollutant elimination percentages. These results suggest significant opportunities for the reuse of treated water, potentially in areas such as irrigation, though some adjustments may be necessary to meet the strictest standards such as those of the European union (EU).

Advanced Oxidation Wastewater Treatment of 3 LPS of an Avocado Sauce Company,at Morelia,Michoacan,Mexico

This paper describes the wastewater treatment of 3 liters per second of capacity of discharges of capacity,from the avocado washed,as well as the production of avocado sauce.Effluents were pretreated with a grease and oil trap and contained small amounts of oil and grease,dissolved and total solids,organic matter and trace of organic and inorganic compounds from the vitamins and minerals of avocado.The treatment train is located in an small surface and the train is integrated with coagulation in line with alumina in a static mixer,rapid filtration in two steps,double advanced oxidation with ozone and heterocyclic photocatalysis with a nanofilm of zinc oxide as,photocatalyzer and final adsorption of refractory compounds with activated charcoal.The treated wastewater meets the environmental regulation to urban sewerage discharges of the city,according to the results of a Mexican Certified Laboratory.

Performance of a Horizontal Flow Constructed Reed Bed Filter for Municipal Wastewater Treatment: The Case Study of the Prototype Installed at Gaston Berger University, Saint-Louis, Senegal

In Saint-Louis, Senegal, a constructed wetland with horizontal flow reed beds (FHa and FHb) has demonstrated significant efficacy in treating municipal wastewater. Analyzing various treatment stages, the system showed only a slight temperature variation, from an influent average of 26.3°C to an effluent of 24.7°C. Electrical conductivity decreased from 1331 mS/cm to 974.5 mS/cm post-primary treatment, with suspended solids (SS) dramatically reduced from 718.9 mg/L to 5.7 mg/L in the final effluent. Biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) saw a notable decrease, from initial levels of 655.6 mg/L and 1240 mg/L to 2.3 mg/L and 71.3 mg/L, respectively. Nitrogenous compounds (N-TN) and phosphates () also decreased significantly, indicating the system’s nutrient removal capacity. Microbiological analysis revealed a reduction in fecal coliforms from 7.5 Ulog/100ml to 1.8 Ulog/100ml and a complete elimination of helminth eggs. The presence of Phragmites and Typha was instrumental in enhancing these reductions. The system’s compliance with the Senegalese standards for disposal into natural environments, WHO recommendations for unrestricted water reuse in irrigation, and the European legislation for water reuse was established. The effluent quality met the stringent criteria for various classes of agricultural reuse, illustrating the system’s potential for sustainable water management. This wetland model presents a robust solution for water-stressed regions, ensuring environmental protection while supporting agricultural needs. The study calls for ongoing research to further refine the system for optimal, reliable wastewater treatment and water resource sustainability.

Electricity generation during wastewater treatment by a microbial fuel cell coupled with constructed wetland

A membrane-less constructed wetland microbial fuel cell （CW-MFC） is constructed and operated under continuous flow with a hydraulic retention time （HRT） of 2 d. Fed with glucose, the CW-MFC generates a stable current density of over 2 A/m3 with a resistor of 1 kΩ and has a chemical oxygen demand （COD） removal efficiency of more than 90% after the startup of 2 to 3 d. A series of systems with the electrode spacings of 10, 20, 30 and 40 cm are compared. It is found that the container with the electrode spacing of 20 cm gains the highest voltage of 560 mV, the highest power density of 0. 149 W/m 3, and the highest Coulombic efficiency of 0.313%. It also has the highest COD removal efficiency of 94. 9%. In addition, the dissolved oxygen （DO） concentrations are observed as the lowest level in the middle of all the CW-MFC reactors. The results show that the more COD is removed, the greater power is generated, and the relatively higher Coulombic efficiency will be achieved. The present study indicates that the CW-MFC process can be used as a cost-effective and environmentally friendly wastewater treatment with simultaneous power generation.

Research Progress on the Application of Magnesium Hydroxide in the Industrial Wastewater Treatment Filed

The research progress on the application of magnesium compounds (magnesium hydroxide,light calcined magnesia,magnesium chloride,sea water,brine,dry brine,etc.) which were represented by magnesium hydroxide in the wastewater treatment filed was comprehensively commentated.Meanwhile,the prospects of application were discussed.Considering the magnesium resources in China were characterized with rich classes,abundant reserves,vast distribution and high quality,it's important to make great efforts to research and exploit magnesium products,especially the exploitation of their meticulous use way.It had the practical significance for the sustainable development of economy in China.

Bicarbonate activation of hydrogen peroxide: A new emerging technology for wastewater treatment

The serious limitations of available technologies for decontamination of wastewater have compelled researchers to search for alternative solutions. Catalytic treatment with hydrogen peroxide, which appears to be one of the most efficient treatment systems, is able to degrade various organics with the help of powerful ·OH radicals. This review focuses on recent progress in the use of bicarbonate activated hydrogen peroxide for wastewater treatment. The introduction of bicarbonate to pollutant treatment has led to appreciable improvements, not only in process efficiency, but also in process stability. This review describes in detail the applications of this process in homogeneous and heterogeneous systems. The enhanced degradation, limited or lack of leaching during heterogeneous degradation, and prolonged catalysts stability during degradation are salient features of this system. This review provides readers with new knowledge regarding bicarbonate, including the fact that it does not always harm pollutant degradation, and can significantly benefit degradation under some conditions.

Community analysis of ammonia-oxidizing bacteria in activated sludge of eight wastewater treatment systems

We investigated the communities of ammonia-oxidizing bacteria （AOB） in activated sludge collected from eight wastewater treatment systems using polymerase chain reaction （PCR） followed by terminal restriction fragment length polymorphism （T-RFLP）, cloning, and sequencing of the α-subunit of the ammonia monooxygenase gene （amoA）. The T-RFLP fingerprint analyses showed that different wastewater treatment systems harbored distinct AOB communities. However, there was no remarkable difference among the AOB T- RFLP profiles from different parts of the same system. The T-RFLP fingerprints showed that a full-scale wastewater treatment plant （WWTP） contained a larger number of dominant AOB species than a pilot-scale reactor. The source of influent affected the AOB community, and the WWTPs treating domestic wastewater contained a higher AOB diversity than those receiving mixed domestic and industrial wastewater. However, the AOB community structure was little affected by the treatment process in this study. Phylogenetic analysis of the cloned amoA genes clearly indicated that all the dominant AOB in the systems was closely related to Nitrosomonas spp. not to Nitrosospira spp. Members of the Nitrosomonas oligotropha and Nitrosomonas communis clusters were found in all samples, while members of Nitrosomonas europaea cluster occurred in some systems.

An innovative integrated oxidation ditch with vertical circle(IODVC) for wastewater treatment

The oxidation ditch process is economic and efficient for wastewater treatment, but its application is limited in case where land is costly due to its large land area required. An innovative integrated oxidation ditch with vertical circle(IODVC) system was developed to treat domestic and industrial wastewater aiming to save land area. The new system consists of a single channel divided into two ditches(the top one and the bottom one by a plate), a brush, and an innovative integral clarifier. Different from the horizontal circle of the conventional oxidation ditch, the flow of IODVC system recycles from the top zone to the bottom zone in the vertical circle as the brush is running, and then the IODVC saved land area required by about 50% compared with a conventional oxidation ditch with an intrachannel clarifier. The innovative integral clarifier is effective for separation of liquid and solids, and is preferably positioned at the opposite end of the brush in the ditch. It does not affect the hydrodynamic characteristics of the mixed liquor in the ditch, and the sludge can automatically return to the down ditch without any pump. In this study, experiments of domestic and dye wastewater treatment were carried out in bench scale and in full scale, respectively. Results clearly showed that the IODVC efficiently removed pollutants in the wastewaters, i.e., the average of COD removals for domestic and dye wastewater treatment were 95% and 90%, respectively, and that the IODVC process may provide a cost effective way for full scale dye wastewater treatment.

Sludge reduction with Tubificidae and the impact on the performance of the wastewater treatment process

To reduce excess sludge, a Tubificidae reactor was combined with an integrated oxidation ditch with vertical circle （IODVC）, and a new integrated system was developed for wastewater treatment, A pilot-scale of this integrated system was tested to investigate the sludge reduction with Tubificidae and the impact on effluent quality and sludge production. The dominant worm was Branchnria Sowerbyi in the Tubificidae reactor after inoculation of Branchnria Sowerbyi and Limnodrilns sp., and the maximal volume density of wet Tubificidae in vessels of the Tubificidae reactor was 17600 g/m^3. Two operational modes, treating the excess sludge （first mode） and the returned sludge （second mode） of IODVC by the Tubificidae reactor, were used in this experiment. The results showed that the excess sludge reduction rate was 46.4% in the first mode, and the average sludge yield of the integrated system was 6.19× 10^-5 kg SS/kg COD in the second mode. Though the sludge returned to IODVC via the Tubificidae reactor, it had little impact on the effluent quality and the sludge characteristics of the IODVC. No new type of recalcitrant substance in the supernatant was discharged into the environment when the sludge was treated by Tubificidae. The experimental results also indicated that no significant changes occurred on the viscosity, specific resistance, and the floc size distribution of the sludge.

Levels and distributions of polychlorinated biphenyls in sewage sludge of urban wastewater treatment plants

Concentrations of polychlorinated biphenyls （PCBs） have been measured in sewage sludge samples from 8 urban wastewater treatment plants in Beijing, China. The PCB congeners were analyzed by isotope dilution high resolution gas chromatography/high resolution mass spectrometry method. The concentration of PCBs ranged from 65.6 to 157 ng/g dry weight （dw）, with a mean value of 101 ng/g dw. The dioxin-like PCB WHO-TEQs （World Health Organization-Toxic Equivalents） of the sludge were lower than 1 pg /g dw. Consequently, all the concentrations of PCBs in sludge samples were below the upper limit for land application according to the Chinese legislation law for agriculture use. The PCB homologue profiles in sludge samples were dominated by tri-CBs and tetra- CBs. Similar distributions have been found in one of the Chinese PCB commercial products. The patterns of dioxin-like and indicator congeners observed in this study were quite similar in all samples. The predominant congener for dioxin-like and indicator PCBs were PCB-118 and PCB-28, respectively, while PCB-126 had the highest TEQ value.

Fluidized-Bed Bioreactor Applications for Biological Wastewater Treatment： A Review of Research and Developments

Wastewater treatment is a process that is vital to protecting both the environment and human health. At present, the most cost-effective way of treating wastewater is with biological treatment processes such as the activated sludge process, despite their long operating times. However, population increases have created a demand for more efficient means of wastewater treatment, Fluidization has been demonstrated to in- crease the efficiency of many processes in chemical and biochemical engineering, but it has not been widely used in large-scale wastewater treatment. At the University of Western Ontario, the circulating fluidized-bed bioreactor （CFBBR） was developed for treating wastewater. In this process, carrier particles develop a biofilm composed of bacteria and other microbes. The excellent mixing and mass transfer characteristics inherent to fluidization make this process very effective at treating both municipal and industrial wastewater. Studies of lab- and pilot-scale systems showed that the CFBBR can remove over 90% of the influent organic matter and 80% of the nitrogen, and produces less than one-third as much biological sludge as the activated sludge process. Due to its high efficiency, the CFBBR can also be used to treat wastewaters with high organic solid concentrations, which are more difficult to treat with conventional methods because they require longer residence times; the CFBBR can also be used to reduce the system size and footprint. In addition, it is much better at handling and recovering from dynamic loadings （i.e., varying influent volume and concentrations） than current systems. Overall, the CFBBR has been shown to be a very effective means of treating wastewa- ter, and to be capable of treating larger volumes of wastewater using a smaller reactor volume and a shorter residence time. In addition, its compact design holds potential for more geographically localized and isolat- ed wastewater treatment systems.

A pilot scale anoxic/oxic membrane bioreactor(A/O MBR) for woolen mill dyeing wastewater treatment

A pilot scale(10 m 3/d) anoxic/oxic membrane bioreactor(A/O MBR) was tested for dyeing wastewater treatment of woolen mill without wasting sludge in 125 days operation. Results showed that the effluent quality was excellent, i.e. effluent COD less than 25 mg/L, BOD 5 under 5 mg/L, turbidity lower than 0 65 NTU, and colour less than 30 DT, and met with the reuse water standard of China. The removal rates of COD, BOD 5, colour, and turbidity were 92 4%, 98 4%, 74% and 98 9%, respectively. Constant flux operation mode was carried out in this study, and backwash was effective for reducing membrane fouling and maintaining constant flux. Membrane fouling had heavy impact on energy consumption. More attention should be paid on pipe selection and design for the sidestream MBR system, too.

A system combining microbial fuel cell with photobioreactor for continuous domestic wastewater treatment and bioelectricity generation

A coupled system consisting of an upflow membrane-less microbial fuel cell (upflow ML-MFC) and a photobioreactor was developed, and its effectiveness for continuous wastewater treatment and electricity production was evaluated. Wastewater was fed to the upflow ML-MFC to remove chemical oxygen demand (COD), phosphorus and nitrogen with simultaneous electricity generation. The effluent from the cathode compartment of the upflow ML-MFC was then continuously fed to an external photobioreactor for removing the remaining phosphorus and nitrogen using microalgae. Alone, the upflow ML-MFC produces a maximum power density of 481 mW/m 3 , and obtains 77.9% COD, 23.5% total phosphorus (TP) and 97.6% NH4+-N removals. When combined with the photobioreactor, the system achieves 99.3% TP and 99.0% NH4+-N total removal. These results show both the effectiveness and the potential application of the coupled system to continuously treat domestic wastewater and simultaneously generate electricity and biomass.

Treatment of chitin-producing wastewater by micro-electrolysis-contact oxidization

The technique of micro-electrolysis-contact oxidization was exploited to treat chitin-producing wastewater. Results showed that Fe-C micro-electrolysis can remove about 30% CODcr, raise pH from 0.7 to 5.5. The CODcr removal efficiency by biochemical process can be more than 80%. During a half year抯 operation, the whole system worked very stably and had good results, as proved by the fact that every quality indicator of effluent met the expected discharge stan-dards; which means that chitin wastewater can be treated by the technique of micro-electrolysis, contact oxidization.

Effect of powdered activated carbon on Chinese traditional medicine wastewater treatment in submerged membrane bioreactor with electronic control backwashing

Chinese traditional medicine wastewater, rich in macromolecule and easy to foam in aerobic biodegradation such as Glycosides, was treated by two identical bench-scale aerobic submerged membrane bioreactors （SMBRs） operated in parallel under the same feed, equipped with the same electronic control backwashing device. One was used as the control SMBR （CSMBR） while the other was dosed with powdered activated carbon （PAC） （PAC-amended SMBR, PSMBR）. The backwashing interval was 5 min. One suction period was about 90 min by adjusting preestablished backwashing vacuum and pump frequency. The average flux of CSMBR during a steady periodic state of 24 d （576 h） was 5.87 L/h with average hydraulic residence time （HRT） of 5.97 h and that of PSMBR during a steady periodic state of 30 d （720 h） was 5.85 L/h with average HRT of 5.99 h. The average total chemical oxygen demand （COD） removal efficiency of CSMBR was 89.29% with average organic loading rate （OLR） at 4.16 kg COD/（m^3.d） while that of PSMBR was 89.79% with average OLR at 5.50 kg COD/（m^3.d）. COD concentration in the effluent of both SMBRs achieved the second level of the general wastewater effluent standard GB8978-1996 for the raw medicine material industry （300 mg/L）. Hence, SMBR with electronic control backwashing was a viable process for medium-strength Chinese traditional medicine wastewater treatment. Moreover, the increasing rates of preestablished backwashing vacuum, pump frequency, and vacuum and flux loss caused by mixed liquor in PSMBR all lagged compared to those in CSMBR; thus the actual operating time of the PSMBR system without membrane cleaning was extended by up to 1.25 times in contrast with the CSMBR system, and the average total COD removal efficiency of PSMBR was enhanced with higher average OLR.