Machine learning approaches to predict the photocatalytic performance of bismuth ferrite-based materials in the removal of malachite green.

This study focuses on the potential capability of numerous machine learning models, namely CatBoost, GradientBoosting, HistGradientBoosting, ExtraTrees, XGBoost, DecisionTree, Bagging, light gradient boosting machine (LGBM), GaussianProcess, artificial neural network (ANN), and light long short-term memory (LightLSTM). These models were investigated to predict the photocatalytic degradation of malachite green from wastewater using various NM-BiFeO3 composites. A comprehensive databank of 1200 data points was generated under various experimental conditions. The ten input variables selected were the catalyst type, reaction time, light intensity, initial concentration, catalyst loading, solution pH, humic acid concentration, anions, surface area, and pore volume of various photocatalysts. The MG dye degradation efficiency was selected as the output variable. An evaluation of the performance metrics suggested that the CatBoost model, with the highest test coefficient of determination (0.99) and lowest mean absolute error (0.64) and root-mean-square error (1.34), outperformed all other models. The CatBoost model showed that the photocatalytic reaction conditions were more important than the material properties. The modeling results suggested that the optimized process conditions were a light intensity of 105 W, catalyst loading of 1.5 g/L, initial MG dye concentration of 5 mg/L and solution pH of 7. Finally, the implications and drawbacks of the current study were stated in detail.

Recovering Nutrients from Waste Black Water Through Multi-Functional Mesoporous Silica.

In order to prevent the harmful effects in water phase such as eutrophication, industrial and urban sewages must be treated before discharging into the aquatic environment. In this work, amine grafted magnetic nanoporous silica materials are synthesized and applied as an adsorbent for the recovery of nutrients from waste black water. The magnetic force could separate the surface func-tionalized nanoporous silica materials from aqueous medium after treatment, and showed the higher adsorption capacity of nutrients than that of the original mesoporous silica. The multi-functional nanoporous silica adsorbents were effectively removed phosphate and nitrate at 20 °C with the maximum adsorption capacities of 42.5 and 34.9 mg/g, respectively. The overall results indicated that the synthesized multi-functional nanoporous silica sorbents can be a candidate material for the nutrient recovery in wastewater treatment system.

Development of a Polymeric Carbon Nanocomposite Hollow-Fiber Membrane for Wastewater Treatment.

This study investigated experimental parameters to fabricate polymeric carbon nanocomposite hollow-fiber membranes with graphene oxide and multi-walled carbon nanotubes. This case was different from that of flat-sheet type membranes in that the characteristics of the hollow-fiber type membranes were affected by the structure of the spinneret, the flow rate of the injected polymer and draw solution, and the mixing ratio. The membranes were characterized in terms of mechanical strength, porosity, hydrophilicity, and permeate flux using different solutions. The results reveal a mechanical strength of the carbon nanocomposite hollow-fiber membranes that is about 47.8% higher than that of hollow-fiber membranes without carbon nanomaterials. The porosity and surface hydrophilicity changed to produce more applicable membranes for water and wastewater treatment. As for the permeate flux, the nanocomposite membrane with graphene oxide showed a higher flux compared to the multi-walled carbon nanotubes membrane, which could be influenced by structural effects of the carbon materials.

The Water Quality Management for Recirculating Aquaculture System by Applying Nano Adsorption Technology.

In a fish farm, the water quality is important to ensure fish growth and farm productivity. However, the study of the quality of water using in aquaculture has been ignored until now. Although there are several methods to treat water, nanomaterials have not yet been applied for indoor fish farming because it may difficult to supply a sufficient amount of water, and the operating parameters have not been developed for recirculating aquaculture systems. Nanotechnology can be applied to treat water, specifically through adsorption and filtration, to produce drinking water from surface water and to treat wastewater by processing a high volume of effluent. The adsorption and filtration of seawater has also progressed to allow for desalination of seawater, and this is recognized as a necessary tool for extended treatment protocols of various types of seawater. This study investigated the treatment of aquaculture water using nano-porous adsorbents (e.g., pumice stone) to control the contaminants in seawater in order to maintain the water quality required for aquaculture. The results are used to derive an analytical relationship between the ionic species in aquaculture water, and this provides empirical parameters for a batch reactor for aquaculture. The quality of the influent and effluent for aquaculture is compared using time-series analyses to evaluate the reduction rate of ionic components and thus suggest the optimum condition for fish farming using bioreactor processes.

Biological fixed-film systems.

The technical papers published in 2019 regarding wastewater treatment and microbial films were classified into two categories: biofilm and biofilm reactors. The biofilm category includes biofilm formation, biofilm consortia, bacterial signals, biofouling, extracellular polymeric substances, and biofilm membrane bioreactors. The biofilm reactors category provides recent information on rotating biological contactors, fluidized-bed biofilm reactors, integrated fixed-film activated sludge, moving-bed biofilm reactors, packed-bed biofilm reactors, sequencing biofilm batch reactors, and trickling filters.

Melanin pigments extracted from horsehair as antibacterial agents.

Here we present the important findings related to biologically derived pigments for potential use as antibacterial agents. Melanin biopigments extracted from Equus ferus hair exhibit a homogeneous elliptical microstructure with highly ordered semicrystalline features. Spectroscopic analysis indicates that melanin contains a high degree of redox active catechol groups, which can produce reactive oxygen species. The antibacterial activity of melanins was tested by incubating Escherichia coli and Staphylococcus aureus with melanins. The results showed 100% bacterial growth inhibition within 4 h. This finding suggests that melanin pigments may serve as naturally occurring antibacterial agents with unique redox chemistry and reactive oxygen species generation capability.

Evaluating membrane fouling potentials of dissolved organic matter in brackish water.

Isolating dissolved organic matter (DOM) is a preliminary step that improves the accuracy of its characterization. In this study, DOM in brackish water was clearly separated and evaluated by multiple characterization analyses. The sample was divided into three fractions by preparative high-performance liquid chromatography (preparative HPLC) according to molecular size. The homogeneity of each fraction was estimated by analytical size exclusion chromatography (SEC) and fluorescence excitation-emission matrix (FEEM). Pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) and liquid chromatography-organic carbon detection (LC-OCD) were used to characterize the physicochemical properties of each fraction. Py-GC/MS revealed that Fraction 1 consisted of evenly distributed organic matter in order polysaccharides, proteins, polyhydroxy aromatics, lignins, and lipids. However, Fraction 2 was primarily composed of dominant lipids and low portion of proteins, and Fraction 3 was composed predominantly of lignins and lipids. The LC-OCD results showed that Fractions 1 and 2 had similar organic carbon (OC) compositions: a humic substance (ca. 37%), building blocks (ca. 10%), and neutrals (ca. 37%), whereas Fraction 3 contained a high proportion of neutrals (62%). In the fouling experiments, the distinct DOM characteristics in each fraction resulted in different declining flux behaviors, ranked as: Fraction 2 > Fraction 1 > Fraction 3.

Removal of Heavy Metal Ion in Wastewater by Dendritic Nano-Structured Complex Material.

The specific adsorbents for the removal of heavy metal were synthesized by polyamidoamine dendrimer and blast furnace slag, and their physico-chemical properties were evaluated in this study. The batch experiment was evaluated the adsorptive water treatment capability of adsorbent, and the zeta potential and surface morphology were analyzed for evaluating of the material. In result, 10% volume loading adsorbent presented the high yields of heavy metal adsorption in water phase, and Cr (III) interacted highly with dendrimer adsorbents. Furthermore, it was evaluated that the adsorption properties of dendrimer adsorbent were increased with increasing the ligand-to-metal charge-transfer.

Reduction of Fluoride in Water Phase by Micro-Nano Bubble Pretreatment Process.

Fluoride is important to aquatic environment and health aspects, and the optimal fluoride concentration in water is below 1 mg/L. In this study, the micro-nano bubble pretreatment was applied to remove fluoride ions in the water phase. The pH control by calcium hydroxide (Ca(OH)2), and coagulation processes with poly aluminum chloride (PAC), aluminum sulfate (Alum), F900 and two kinds of polymer named as A-polymer and A430P polymer were applied for the pretreated wastewater. In results, the combination of PAC and A430P polymer with micro-nano bubble pretreated wastewater showed a higher fluoride removal than the case of other combinations. In chemical oxygen demand (COD) removal, the combination of Alum and A430P polymer with micro-nano bubble pretreated wastewater showed the best removal efficiency (64.6%) while the COD removal without pretreatment was 71.4% for fluoride and 57.2% for COD.

Biological Fixed Film.

The review includes scientific literatures published in the year of 2017 regarding the uses of biofilm and bioreactor to treat wastewater. Topics considered are: biofilm formation and factors that impact biofilm formation; extracellular polymeric substance from biofilms; biofilm consortia and quorum sensing; biofilm associated phage; biofilm reactors; and biofilm in bioelectrochemical systems.

Nano-Sized Fume Biogas Production from Food Waster Using Semi-Continuous Anaerobic Digester.

In this study, the nano-sized fume biogas production from food waste was investigated using lab scale semi-continuous stirred tank reactor (SCSTR) at 35 °C with 30d HRT and 30L working volume. The mesophilic digestion test was performed with three different feed materials (food waste) and food to microorganism (F/M) ratios (0.13, 0.34, and 0.27) in the same experiment. The results showed that the F/M ratios significantly affected the biogas production rate. The highest production rate was obtained at F/M ratio of 0.13. Nano-sized fume biogas produced in anaerobic digestion consists of 68.7% CH4, 31.2% CO2 and 30~200 nm particle. The average nano-sized fume biogas and methane production of digester were 29.96 L/Kg versus day-1 and 20.58 L/Kg versus day-1, respectively. The CH4 could be calculated as the heat energy 1.85 Kcal/Kg VS day-1. The digestion was operated without addition of chemicals or nutrients into the system.

Environmental Applications of Nano-Sized Recycled Aggregates: The Effect of Sterilization and Adsorption.

To evaluate the sterilize efficiency of nano-sized recycled aggregates (RAs), several types of RAs were examined for the purpose of environmental stamping out procedure. The poultry (e.g., chicken) was selected as a target livestock of epidemic disease, and the blast furnace slag (BFS), fly ash (FA), slaked lime (SL), nano-cerium (n-Ce) and shell (Sh) were used as the RAs materials. The fermented solution of effective microorganisms (EM) was added to decompose the target livestock. Various kinds of lab-scale reactor were operated to examine the effects of RAs volume; high and low volume of RAs (e.g., 1.89 w/v% and 1.14 w/v% of RA in solution, respectively), and the effects of EM concentration (e.g., concentrated solution (100%) and diluted solution (12.5%)) with tested in different reaction time. The number of microorganisms after batch tests was counted for the sterilized effects of RAs, and organic matters (e.g., chemical oxygen demand (COD)) and inorganic matters (e.g., suspended solids (SS), heavy metals and potential ions) were analyzed before and after adsorption process. The cases of SL and n-Ce showed high removal of microorganism in the batch of high concentrated EM for 20 days. However the other RA materials were less effective on the sterilization especially in lower volume of RAs. In diluted EM (e.g., 12.5%) tests, most RAs have high sterilization efficiencies in the short periods of batch reaction regardless of RAs types, and it was more effective with longer reaction time. The BFS and n-Ce exhibited higher surface area than others and they adsorbed highly heavy metals in water. The results suggested that the concentration of target organism was the most important to determine sterilization and adsorption properties of RAs.

Biological Fixed Film.

The review includes scientific and technical literature published in the year of 2016 regarding the uses of biofilm and bioreactors to treat wastewater. Topics considered are: biofilm formation and factors that impact biofilm formation; extracellular polymeric substances (EPS) from biofilms; biofilm consortia, quorum sensing and quenching; biofilm reactors and biofilm in bioelectrochemical systems.

Microbial community analysis of bulk sludge/cake layers and biofouling-causing microbial consortia in a full-scale aerobic membrane bioreactor.

Pyrosequencing was used to investigate biofouling-causing microbial consortia at the community level in bulk sludge and cake layers within a full-scale membrane bioreactor (MBR). The analysis revealed Chao's estimates of total operational taxonomic units (OTUs) of 1726, 1806, and 1362 for bulk sludge, cake outer layer, and cake inner layer, respectively. The bulk sludge and cake outer layer OTUs clustered together, whereas the cake inner layer OTUs formed a separate group, indicating that environmental conditions affected the microbial community composition within the MBR. Bacteroidetes, Proteobacteria, and Chloroflexi were the dominant phyla in both the bulk sludge and the cake layers. Comparison at the genus level showed twelve distinct genera in the cake layers that were absent in bulk sludge. Twenty distinct genera were recorded in the inner cake layer. Those genera are likely the microbial colonization pioneers in full-scale membrane bioreactors.

The Effects of Pore Volume and Compressive Strength on the Nano-Sized Recycling Material Mixtures.

In this study, the effect on pore volume and compressive strength was investigated using nano-sized blast furnace slag (BFS), fly ash (FA), and desulfurized gypsum (DG). In the chemical compositions of BFS and FA, the sum of the four ingredients, CaO, SiO2, A12O3, and MgO were shown to account for 97% and 87%, respectively. Particles smaller than 50 nm were shown to be distributed in the range of 47.9% to 50.7%, particles larger than 50 nm but smaller than 100 nm were distributed in the range of 19.0% to 29.1%, and particles sized 100 nm or larger were shown to be distributed in the range of 21.3% to 23.2%. As a result of analysis carried out using an scanning electron microscope (SEM), it was found that BFS, FA, and DS are mixtures of smooth spherical particles and unevenly shaped materials. As to the dependence of pore volume, which depends on pore size and compressive strength, the volume of pores of sizes between 3 and 10 nm showed a proportional trend where volume increases and, as a result, compressive strength also increases as the material age increases. Moreover, the volume of pores sized between 10 and 100 nm showed an inversely proportional trend where volume decreases and, as a result, compressive strength also decreases as the material age increases.

Biological Fixed Film.

The review includes literature published in the year of 2015 regarding the uses of biofilm in full-scale and lab-scale bioreactors to treat wastewater. The topics considered include biofilm formation and factors impacting biofilm formation; extracellular polymeric substance from biofilms; biofilm consortia and quorum sensing; biofilm reactors and biofilm in bioelectrochemical systems.

Adsorption of Magnesium Sulfate from Desulfurization Industrial Wastewater by Nano-Cerium Loaded Recycled Aggregates.

In this research, the recycled aggregates (RAs) from blast furnace were solidified with nano-cerium (Ce), and applied to reduce the ionic species (e.g., magnesium sulfate) in the desulfurization industrial wastewater. Static batch experiments were performed based on different loading of recycled aggregates. Sulfate sorption isotherm studies were performed by Langmuir adsorption model. The physical morphologies were determined using scanning electron microscope. The results presented that the partial ions were captured with the different loading of the recycled aggregates during the batch tests. It was observed that 8 hr batch reaction equilibrated the electrical conductivity reduction, and 13% mass loading was estimated an optimal dosage of adsorbent. This study showed the nano-Ce loaded RAs could reduce ionic species in wastewater, and expected to be an economical adsorbent for wastewater treatment process.

Desalination of Basal Water by Mesoporous Carbons Nanocomposite Membrane.

The hydro-transportation process used to obtain bitumen from the Alberta oil sands produces large volume of basal depressurization water (BDW), which contains high salt concentrations. In this research, thin-film nanocomposite (TFN) membrane technology applied to treat BDW in lab-scale, and evaluated water properties before and after the treatment. The average rejection ratios of ionic species were 95.2% and 92.8% by TFN membrane (with ordered mesoporous carbons (OMCs)) and thin-film composite (TFC) (without OMCs) membrane, respectively. The turbidity and total dissolved solids (TDS) were completely rejected in all treatment conditions. Interestingly, the water flux of TFN membrane was dramatically increased compared to TFC membrane. The increase of water flux was believed to be caused by the increased membrane surface hydrophilicity and nano-pore effects by the OMCs.

Co-adsorption of Trichloroethylene and Arsenate by Iron-Impregnated Granular Activated Carbon.

Co-adsorption of trichloroethylene (TCE) and arsenate [As(V)] was investigated using modified granular activated carbons (GAC): untreated, sodium hypochlorite-treated (NaClO-GAC), and NaClO with iron-treated GAC (NaClO/Fe-GAC). Batch experiments of single- [TCE or As(V)] and binary- [TCE and As(V)] components solutions are evaluated through Langmuir and Freundlich isotherm models and adsorption kinetic tests. In the single-component system, the adsorption capacity of As(V) was increased by the NaClO-GAC and the NaClO/Fe-GAC. The untreated GAC showed a low adsorption capacity for As(V). Adsorption of TCE by the NaClO/Fe-GAC was maximized, with an increased Freundlich constant. Removal of TCE in the binary-component system was decreased 15% by the untreated GAC, and NaClO- and NaClO/Fe-GAC showed similar efficiency to the single-component system because of the different chemical status of the GAC surfaces. Results of the adsorption isotherms of As(V) in the binary-component system were similar to adsorption isotherms of the single-component system. The adsorption affinities of single- and binary-component systems corresponded with electron transfer, competitive adsorption, and physicochemical properties.

Biological Fixed Film.

The review includes literatures published in the year of 2014 regarding the uses of biofilm and bioreactor to treat wastewater. Topics considered are: biofilm formation and factors that impact biofilm formation; extracellular polymeric substance from biofilms; biofilm consortia and quorum sensing; biofilm reactors and biofilm in bioelectrochemical systems.