Dominant Removal Research Articles

Efficient recovery of Pd(II) from nuclear wastewater using a functionalized covalent organic frameworks with uniform spherical structure: Size control, performance and mechanism insight

The efficient recovery of palladium from the spent nuclear fuel was of great significance to the sustainable development of nuclear energy. Herein, the uniform spherical COFs were constructed by a facile approach at room temperature, which were further surface functionalized by a thiol-ene “click” reaction to recover Pd(II). Microscopic and spectroscopic studies manifested that the formation mechanism and size of spherical COFs were greatly affected by the amount of catalyst and solvent type. The TAPB-BPTA-DTT and TAPB-BPTA-S-β-CD exhibited high Pd(II) recovery efficiency due to the introduction of sulfhydryl groups, and the maximum adsorption capacities were 489.3 and 234.3 mg/g, respectively. Meanwhile, the water environmental condition played an important role in the separation process, and the classical adsorption models demonstrated that monolayer chemisorption was the dominant removal mechanism. Mechanism analysis showed that the excellent adsorption performance was mainly attributed to the electrostatic interaction, physical absorption and chelation of N, O, and S groups with Pd(II). Thus, it is expected that this work could provide more insight into COFs materials, thereby promoting palladium removal advancements in the spent nuclear fuel.

Thermal Fluid Modeling Approaches in SAM for High Temperature Gas-Cooled Reactor Applications

This paper provides an overview of the unique modeling and simulation challenges and needs in the system and safety analysis of two common types of High Temperature Gas-cooled Reactor (HTGR) designs. The challenges are associated with the complex core geometry configurations and the change of the dominant heat removal mechanisms between normal operating conditions and decay heat removal transients. This requires that simulation tools utilize models with reasonable length scales and capture both the localized heat transfer and the core-scale heat transfer at the same time. To meet such analysis needs, different methodologies were developed. This includes adopting existing methods and further developing/improving them, as well as proposing innovative methods that leverage advanced computational frameworks such as the Multiphysics Object Oriented Simulation Environment (MOOSE).

Sulfamethoxazole removal and ammonium conversion in microalgae consortium: Physiological responses and microbial community changes

Microalgae (Mychonastes sp.) consortium was investigated for nutrient and antibiotics removal and its responses to varying sulfamethoxazole (SMX) concentrations (0–1000 μg/L) in ammonia-rich wastewater. The results showed that the introduction of SMX (100–1000 μg/L) slightly improved ammonium nitrogen removal efficiency instead of inhibition. Swift SMX degradation was observed across all SMX-treated systems, with the highest SMX removal efficiency (96 %) at an SMX concentration of 100 μg/L. Biodegradation remained the dominant SMX removal mechanism, contributing 78 % of SMX removal at an SMX concentration of 800 μg/L, while adsorption and photolysis played minor roles. Addition of SMX augmented biomass and lipid productivity, but decreased chlorophyll contents in the microalgae consortium. Furthermore, extracellular polymeric substance (EPS) production correlated positively with SMX input concentration, with the microalgae consortium exposed to 800 μg/L SMX displaying the most pronounced stimulation of protein production (51.5 ± 2.0 mg/g DCW) and polysaccharides production (74.8 ± 3.9 mg/g DCW). In response to an increase in SMX concentrations, enzyme activities associated with antioxidant defense, such as superoxide dismutase (SOD), peroxidase (POD) and malondialdehyde (MDA) increased, the catalase (CAT) decreased, indicating an initial defense mechanism. Concurrently, the relative abundance of Mychonastes sp. within the consortium rose from 87 % at 300 μg/L SMX to 99.9 % at 800 μg/L SMX. while Shannon indices of the bacterial community increased from 1.415 to 2.867. This shift inhibited the initially dominant Saprospiraceae bacteria, facilitating the profound increase of adapted Aquimonas. These findings demonstrate the feasibility of the simultaneous removal of antibiotics and nutrients from wastewater with a microalgae consortium system.

Development of a ReaxFF Reactive Force Field for Pt/Cl Systems with Application to Platinum Metal Etching with Chlorine and Hydrogen Chloride Gases.

In this study, we present the development of a ReaxFF Pt/Cl/H reactive force field designed to elucidate the etching process by Cl for Pt surfaces. The ReaxFF force field parameters were optimized based on a quantum mechanical training set, which included adsorption energies of Cl and dissociation of HCl on Pt(100) and Pt(111) surfaces, energy/volume relations of PtCl2 crystals, and Cl diffusion on Pt(100) and Pt(111) surfaces. The predictive capability of the force field was further established through molecular dynamics simulations, which investigated the interactions of Cl2 and HCl molecules with the (100) and (111) surfaces of c-Pt crystalline solid slabs. A comparative analysis revealed that the Pt (100) surface exhibited higher susceptibility to chlorination and etching, leading to a more dominant removal of surface Pt atoms, whereas the Pt (111) surface showed greater resistance to these processes. This resistance impeded the access of Cl atoms to the Pt surface, resulting in a slower formation of PtxCly molecules. The etching ratios between HCl and Cl2 were compared with experimental results, yielding satisfactory agreement. This indicates that the developed ReaxFF protocol serves as a valuable tool for studying atomistic-scale details of the etching process in platinum metal systems.

The convex relationship between plant cover and biomass: Implications for assessing species and community properties

AbstractQuestionsCover and biomass serve as common measures of species abundance in plant ecology. However, the underlying relationship between these two measures and its implications remain poorly understood. This makes results based on cover and biomass difficult to compare.LocationsWet meadow, southeast of České Budějovice, Czech Republic (48°57′ N, 14°36′ E).MethodWe developed theoretical expectations for systematic differences in characterizing vegetation using cover and biomass for species and community characteristics, including species diversity, temporal dynamics, and responses to experimental manipulations. We then tested these expectations using cover and biomass data from an experimental study of fertilization and dominant removal spanning 14 years (2001–2014).ResultsConsistent with our expectations, on average, species biomass corresponded to the power of species cover, with a power coefficient slightly below 3/2. Community diversity indices calculated using cover and biomass were tightly correlated but were higher for cover. Temporal variabilities based on cover and biomass for individual species were also correlated, but higher for biomass than cover. Though strongly correlated, cover data show much stronger asynchrony, suggesting higher importance of compensatory dynamics. However, using the sum of individual species' cover values as a measure of total community abundance or productivity is problematic. Such a measure is nearly independent of total biomass and leads to contradictory results when used to characterize temporal variability. Species‐ and community‐level responses to treatments were congruent between the measures.ConclusionsOur study provides theoretical background for a convex relationship between plant cover and biomass. The data analysis confirms the relationship and its consequences for describing species‐ and community‐level properties. Most characteristics are well correlated between cover and biomass, but with one metric systematically shifted higher in many cases. Total abundance is the most sensitive measure and is well characterized by sum of biomass, but not by sum of cover. Understanding these systematic differences allows meaningful comparison of studies based on biomass and cover.

Updated review on current approaches and challenges for poly- and perfluoroalkyl substances removal using activated carbon-based adsorbents

Per- and polyfluoroalkyl substances (PFAS) are persistent and toxic to the environment and human health. Activated carbon (AC) has been extensively investigated for the removal of PFAS and has shown promising candidates for PFAS removal. Up to date, a remarkable advancement has been achieved in PFAS removal using AC, still, the application remains challenging. The main objective of this article is to summarize the recent advancement in PFAS removal from water using activated carbon-based adsorbents. The dominant PFAS removal mechanisms using AC are electrostatic interaction, hydrophobic interaction, and ion-exchange. Additionally, this review highlighted the critical factors that influence PFAS removal using AC, including AC's properties, solution pH, ionic strength, and natural organic matter effects. Notably, the presence of natural organic matter significantly impacts PFAS adsorption performance using AC. Moreover, the review also discussed the current trend in regeneration techniques of spent AC for PFAS adsorption and the economic assessment for PFAS removal using AC from scale-up studies to establish cost-effective strategies for scaling up the process. Finally, the challenge and new perspective of AC for PFAS removal were discussed for future research advancement. This review presented the devising practical and environmentally approaches to tackle the challenges encountered by ACs in eliminating PFAS from water.

Inhibition of phosphorus removal performance in activated sludge by Fe(III) exposure: transitions in dominant metabolic pathways.

Simultaneous chemical phosphorus removal process using iron salts (Fe(III)) has been widely utilized in wastewater treatment to meet increasingly stringent discharge standards. However, the inhibitory effect of Fe(III) on the biological phosphorus removal system remains a topic of debate, with its precise mechanism yet to be fully understood. Batch and long-term exposure experiments were conducted in six sequencing batch reactors (SBRs) operating for 155 days. Synthetic wastewater containing various Fe/P ratios (i.e., Fe/P = 1, 1.2, 1.5, 1.8, and 2) was slowly poured into the SBRs during the experimental period to assess the effects of acute and chronic Fe(III) exposure on polyphosphate-accumulating organism (PAO) growth and phosphorus metabolism. Experimental results revealed that prolonged Fe(III) exposure induced a transition in the dominant phosphorus removal mechanism within activated sludge, resulting in a diminished availability of phosphorus for bio-metabolism. In Fe(III)-treated groups, intracellular phosphorus storage ranged from 3.11 to 7.67 mg/g VSS, representing only 26.01 to 64.13% of the control. Although the abundance of widely reported PAOs (Candidatus Accumulibacter) was 30.15% in the experimental group, phosphorus release and uptake were strongly inhibited by high dosage of Fe(III). Furthermore, the abundance of functional genes associated with key enzymes in the glycogen metabolism pathway increased while those related to the polyphosphate metabolism pathway decreased under chronic Fe(III) stress. These findings collectively suggest that the energy generated from polyhydroxyalkanoates oxidation in PAOs primarily facilitated glycogen metabolism rather than promoting phosphorus uptake. Consequently, the dominant metabolic pathway of communities shifted from polyphosphate-accumulating metabolism to glycogen-accumulating metabolism as the major contributor to the decreased biological phosphorus removal performance.

Long‐term effects of meadow management on seed bank diversity and composition

AbstractAimsOligotrophic grasslands are habitats that host among the most diverse plant communities in Europe. Altering management regimes by either intensifying or ceasing management is known to decrease plant diversity. Yet, despite its importance for the recovery of plant communities after disturbances, little is known about whether seed banks are also affected by changes in management. Here, we investigate the effect of management practices on a meadow seed bank using a long‐term manipulative experiment. We focus on the response of the seed bank to the treatments, and the relationship between the seed bank and the vegetation response.MethodsThe study was conducted in a species‐rich wet meadow. The experiment consists of a factorial combination of fertilization, mowing, and removal of the dominant species. After 20 years of management, the seed bank was sampled seasonally at two soil layer depths. Standing vegetation was recorded in June at the peak of vegetation.ResultsAll seed bank characteristics varied between soil layers. Mowing decreased seed density and diversity, while fertilization significantly affected the species composition. Dominant removal had no effect on the seed bank. While seed bank diversity was not correlated to vegetation diversity, individual species' responses to mowing and fertilization were positively correlated in the seed bank and the vegetation.ConclusionsOur results show that long‐term management influences the seed bank down to 10 cm of soil depth. Whereas mowing apparently reduced seed density and diversity, the effects of fertilization on these characteristics were harder to interpret. After 20 years, most species had concordant responses to both mowing and fertilization, indicating a low legacy of previous management regimes on the seed bank. Our study reveals that the intensification of grassland management has a profound effect on plant diversity by directly affecting plant communities and their seed‐bank‐driven recovery potential.

Effects and mechanism of uranium(VI) removal by wood biochar loaded with MnFe2O4

BackgroundUranium (U) seriously threatens environmental health due to its chemical and radioactivity toxicity unless it is immobilized by adsorption materials. MethodsHere, MnFe2O4 was used to modify biochar derived from apple tree branches to obtain MnFe2O4-biochar (MFBC), which was used for U(VI) removal. The mechanisms were explored by advanced analytical techniques, including scanning electron microscopy combined with energy dispersive X-ray spectroscopy (SEM-EDS), Brunauer-Emmett-Teller (BET), vibrating sample magnetometer (VSM), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Significant findingsThe MFBC displayed a considerable adsorption rate of U(VI), with a maximum adsorption capacity of 83.00 mg/g at pH 6.0 and 313 K. The removal behavior was well described by the Freundlich and pseudo-second-order kinetic models. The dominant removal mechanism was complexation between the negatively charged O-containing groups on the MFBC and the positively charged U(VI). This work demonstrates the potential of MFBC to remediate U(VI)-contaminated wastewater.

Mechanisms of copper and zinc bioremoval by microalgae and bacteria grown in nutrient rich wastewaters

Swine farming produces large quantities of nutrient-rich wastewater, which often contains metals such as Cu and Zn, used as feed additives for pigs. These metals must be removed from the wastewater before discharge but their retention in the biomass can limit its subsequent utilization. Photobioreactors are a very promising alternative for swine wastewater treatment, as the consortium of microalgae and bacteria growing symbiotically in these reactors allows high nutrient and metal removal efficiency at moderate costs. This work studies the mechanisms of removal of Cu(II) and Zn(II) by the two types of microorganisms growing in these photobioreactors. A microalga commonly used in wastewater treatment (Scenedesmus almeriensis) and an activated sludge were kept in contact with synthetic wastewater containing 100 mg/L of Cu and Zn. After 72 h, Scenedesmus almeriensis removed 43% of Cu and 45% of Zn, while activated sludge removed 78% of Cu and 96% of Zn. Single and sequential extractions of the biomasses using different extracting reagents revealed that biosorption on protonable groups is the dominant removal mechanisms. Mild reagents solubilized 69% of Cu and 94% of Zn from the microalgae and 76% of Cu and 93% of Zn from the activated sludge. Low metal concentrations in the oxidizable and residual fractions evidenced minimal bioaccumulation inside the cells. FTIR and ESEM-EDX analysis confirmed biosorption by ion exchange and complexation as the main metal remediation mechanisms. The weak bonds of the biosorbed Cu and Zn ions are beneficial for the valorization of biomass and the obtaining of safe bioproducts.

Warming enhances the negative effects of shrub removal on phosphorus mineralization potential

Shrubs have developed various mechanisms for soil phosphorus utilization. Shrub encroachment caused by climate warming alters organic phosphorus mineralization capability by promoting available phosphorus absorption and mediating root exudates. However, few studies have explored how warming regulates the effects of dominant shrubs on soil organic phosphorus mineralization capability. We provide insights into warming, dominant shrub removal, and their interactive effects on the soil organic phosphorus mineralization potential in the Qinghai-Tibetan Plateau. Real-time polymerase chain reaction was used to quantify the soil microbial phosphatase genes (phoC and phoD), which can characterize the soil organic phosphate mineralization potential. We found that warming had no significant effect on the soil organic phosphate-mineralized components (total phosphate, organic phosphate, and available phosphate), genes (phoC and phoD), or enzymes (acid and alkaline phosphatases). Shrub removal negatively influenced the organic phosphate-mineralized components and genes. It significantly decreased soil organic phosphate mineralization gene copy numbers only under warming conditions. Warming increased fungal richness and buffered the effects of shrub removal on bacterial richness and gene copy numbers. However, the change in the microbial community was not the main factor affecting organic phosphate mineralization. We found only phoC copy number had significant correlation to AP. Structural equation modelling revealed that shrub removal and the interaction between warming and shrub removal had a negative direct effect on phoC copy numbers. We concluded that warming increases the negative effect of shrub removal on phosphorus mineralization potential, providing a theoretical basis for shrub encroachment on soil phosphate mineralization under warming conditions.

Context dependence of warming‐induced shifts in montane soil microbial functions

Abstract High elevation and latitude ecosystems are experiencing high levels of anthropogenic atmospheric warming. Climate warming may directly change soil microbial activity and alter ecosystem carbon dynamics and productivity, but increasing evidence suggests these responses may depend on other biotic factors such as plant community composition and abiotic factors such as moisture. We examined how abiotic (warming) and biotic (presence of dominant plant species) factors interact to affect soil microbial processes. Our experiment deployed the independent and combined treatments of experimental warming and dominant plant species removal in a high and low elevation montane meadows. We analysed multiple soil microbial responses to warming and the presence of a dominant plant at three times throughout the growing season, including soil respiration, microbial metabolic functional diversity, microbial biomass carbon and nitrogen, and extracellular enzyme potential activity. Overall, there were few independent microbial responses to either the warming or the removal treatments. There was a significant interaction between warming and the removal of a dominant plant species, where microbial biomass and the activity of some microbial enzymes were lower in warmed plots where the dominant species was removed relative to control plots. The effect of warming on extracellular enzyme activity was typically observed only at the high‐elevation site. In contrast, we found that effects of warming were consistent across the growing season, despite strong temporal variation in microbial properties. Our results emphasize the need to further consider soil microbial responses to warming under multiple environments, including shifts in both biotic and abiotic factors, to aid in predictions of carbon dynamics under future global change. Read the free Plain Language Summary for this article on the Journal blog.

Sustainable large-scale Fe3O4/carbon for enhanced polystyrene nanoplastics removal through magnetic adsorption coagulation

The omnipresence of nanoplastics in natural water sources raises significant environmental and health concerns due to their challenging removal and potential to transport harmful pollutants. These particles pose threats to terrestrial and aquatic ecosystems, as well as human health, inducing inflammation and oxidative stress. In response, this study focused on an innovative Fe3O4/C nano-adsorbent, derived from discarded printer cartridge toner, for tackling the removal of polystyrene nanoplastics (PS-NPs) through magnetic adsorption coagulation (MAC) with polyaluminum chloride (PACl) as a coagulant. Extensive experimentation achieved a remarkable 99 % removal efficiency at a desirability function value of 0.868 under optimum conditions (pH = 8, adsorbent dosage 2.5 mg, contact time 2 min, PACl concentration 17.5 mg/L, PS-NPs concentration 75 mg/L) with an R2 = 0.9997, a CV% = 0.730 and an Adeq Precision = 122.837. The dominant removal mechanism involved adsorption bridging and electrostatic interaction between PS-NPs and Fe3O4/C in the presence of PACl. Findings covered adsorption kinetics, isotherms, and thermodynamics, adhering to the pseudo-second-order model (R2 = 0.996), Langmuir (R2 = 0.9912) isotherm and negative value of ΔG° (−8.899) as an endothermic adsorption process. The results demonstrated a maximum adsorption capacity of 523 mg/g, showcasing the effectiveness of the approach. Furthermore, the Fe3O4/C material exhibited robust reusability and stability, owing to its magnetite properties. The primary goal was to engineer a magnetic recoverable nano-adsorbent from discarded toner, contributing to cost reduction, streamlined coagulation processes, reduced coagulant consumption, and significantly improved micro/nanoplastics removal.

Ammonolysis of Glyoxal at the Air‐Water Nanodroplet Interface

AbstractThe reactions of glyoxal (CHO)2) with amines in cloud processes contribute to the formation of brown carbon and oligomer particles in the atmosphere. However, their molecular mechanisms remain unknown. Herein, we investigate the ammonolysis mechanisms of glyoxal with amines at the air‐water nanodroplet interface. We identified three and two distinct pathways for the ammonolysis of glyoxal with dimethylamine and methylamine by using metadynamics simulations at the air‐water nanodroplet interface, respectively. Notably, the stepwise pathways mediated by the water dimer for the reactions of glyoxal with dimethylamine and methylamine display the lowest free energy barriers of 3.6 and 4.9 kcal ⋅ mol−1, respectively. These results showed that the air‐water nanodroplet ammonolysis reactions of glyoxal with dimethylamine and methylamine were more feasible and occurred at faster rates than the corresponding gas phase ammonolysis, the OH+(CHO)2 reaction, and the aqueous phase reaction of glyoxal, leading to the dominant removal of glyoxal. Our results provide new and important insight into the reactions between carbonyl compounds and amines, which are crucial in forming nitrogen‐containing aerosol particles.

Ammonolysis of Glyoxal at the Air-Water Nanodroplet Interface.

The reactions of glyoxal (CHO)2 ) with amines in cloud processes contribute to the formation of brown carbon and oligomer particles in the atmosphere. However, their molecular mechanisms remain unknown. Herein, we investigate the ammonolysis mechanisms of glyoxal with amines at the air-water nanodroplet interface. We identified three and two distinct pathways for the ammonolysis of glyoxal with dimethylamine and methylamine by using metadynamics simulations at the air-water nanodroplet interface, respectively. Notably, the stepwise pathways mediated by the water dimer for the reactions of glyoxal with dimethylamine and methylamine display the lowest free energy barriers of 3.6 and 4.9 kcal ⋅ mol-1 , respectively. These results showed that the air-water nanodroplet ammonolysis reactions of glyoxal with dimethylamine and methylamine were more feasible and occurred at faster rates than the corresponding gas phase ammonolysis, the OH+(CHO)2 reaction, and the aqueous phase reaction of glyoxal, leading to the dominant removal of glyoxal. Our results provide new and important insight into the reactions between carbonyl compounds and amines, which are crucial in forming nitrogen-containing aerosol particles.

Biomineralization mechanism and remediation of Cu, Pb and Zn by indigenous ureolytic bacteria B. intermedia TSBOI

Microbially induced carbonate precipitation (MICP) is an effective and eco-friendly technology for remediating heavy metal-contaminated sites. In this study, we investigated the response discrepancies and proposed the dominant removal mechanism of the ureolytic bacteria Brucella intermedia TSBOI for different heavy metal species (Cu, Pb and Zn) under concentration gradients (0.1, 0.2, 0.4, 0.8, and 1.6 mmol/L), and explored the remediation of soil heavy metal pollution by B. intermedia TSBOI under laboratory conditions. The results showed that the heavy metal concentration significantly affected the bacterial cell concentration, urease activity, cell morphology, surface functional groups, and removal efficiency of B. intermedia TSBOI. The presence of Ca2+ negatively affected the biomass and urease activity to some extent but had a non-negligible positive effect of removing heavy metals and was more conducive to the formation and precipitation of biomineralization products. The ability of B. intermedia TSBOI to produce urease intracellularly and secrete it in large quantities to act extracellularly is key to the sustained immobilization of heavy metals and the outstanding performance of B. intermedia TSBOI bacterial solution. The results of heavy metal-contaminated soil remediation showed that B. intermedia TSBOI effectively increased the proportion of carbonate-bound states of Cu, Pb and Zn in the soil and reduced the bioavailability of heavy metals within 30 days. B. intermedia TSBOI could adapt fully to the soil environment and became a dominant genus.

Photocatalytic properties of ZnO nanoparticle coating on porous ceramic substrates with varying porosities produced from fly ash and red mud

AbstractIn order to improve filtering efficacy, nanoparticles are often deposited as photocatalytic degrading agents onto porous ceramics. This study aimed to deposit ZnO nanoparticles on ceramic substrates produced from fly ash and red mud with adjustable porosity and investigate their photocatalytic properties. To achieve this goal, at first porous ceramics were produced and sintered at various temperature/time intervals. It was observed that sintering at 800°C for 120 min provided a proper structure and porosity. In addition, MgO replacement with MgCO3 lowered the water absorption of the samples from 25.63% to 11.45%. The samples were then coated with ZnO nanoparticles using the sol–gel method and the ZnO structures obtained were micron‐sized plates. It was observed that increasing porosity increased the ZnO amount and accordingly the photocatalytic properties of the products. During the adsorption tests conducted in the dark, the coated ceramic samples were stained with MB with a maximum MB adsorption ratio of ∼14%. On the other hand, no visible MB stain was observed on the samples that were exposed to UV irradiation, and the MB removal after the UV irradiation was 93.6%; therefore, it was concluded that the dominant MB removal mechanism was photocatalytic.

A pilot-scale SNAD-MBBR process for treating anaerobic digester liquor of swine wastewater: performance and microbial community.

In this pilot-scale study, simultaneous partial nitrification, anammox, and denitrification (SNAD) process was achieved successfully in a moving bed biofilm reactor (MBBR) for treating anaerobic digester liquor of swine wastewater. After 95days of operation, when the total nitrogen loading rate of SNAD-MBBR process was 1.09kg TN/m3/day, the total nitrogen removal rate could reach 0.87kg TN/m3/day, and the removal efficiencies of ammonium and total nitrogen were 92.0% and 79.7%, respectively. The optimum pH and temperature for SNAD-MBBR process were 8.5 and 35°C, respectively, and the optimum dissolved oxygen for SNAD1 and SNAD2 were 0.30 and 0.07mg/L, respectively. The 16S rRNA sequencing suggested that Candidatus Kuenenia, Candidatus Brocadia, Nitrosomonas, and Denitratisoma were the dominant nitrogen removal bacteria. Some of the co-existing bacteria (Truepera, Limnobacter, and Anaerolineaceae uncultured) promoted ammonium oxidation and guaranteed the growth of the anammox bacteria under adverse environmental conditions. Overall, this study demonstrated that the SNAD-MBBR process would be an energy-saving and cost-effective method for the removal of nitrogen from swine wastewater and provided important process parameters for stable operation of the full-scale SNAD process.

Optimization of a continuous hybrid moving bed biofilm reactor and constructed wetland system for the treatment of paracetamol-spiked domestic wastewater

A continuous system of moving bed biofilm reactor (MBBR) integrated with horizontal subsurface flow constructed wetland (HSSFCW) followed by a sedimentation tank (PUMBBR-CW) was used for the removal of chemical oxygen demand (COD), ammonia (NH4+), and paracetamol. The removal performance of the reactor was analyzed by varying the initial concentration of the pollutants, hydraulic retention time (HRT), and COD to NH4+ ratio (C/N ratio). Polyurethane foam (PUF) waste was used as the bio-carrier in the MBBR system. Microbial degradation, plant uptake, and substrate adsorption were the most dominant removal mechanisms in the PUMBBR-CW. Further insights into the degradation mechanisms were investigated by characterizing the substrate and bio-carrier and analyzing the degradation by-products. More than 95 % of COD removal was achieved with 30.6 h HRT and 550 mg/L initial concentration at a C/N ratio of 10. At 30.6 h HRT and a C/N ratio of 4, 87 % NH4+ and 94 % paracetamol removal were achieved. The low C/N ratio favors paracetamol removal, as the microorganism uses paracetamol as the sole carbon source under low C/N conditions. Moreover, it was found that paracetamol was uptake and stored in the Canna indica L. plant leaves (216 µg/g). An artificial neural network (ANN) was developed to find the optimum operating condition with maximum removal efficiency. The PUMBBR-CW system effectively overcame the drawbacks of conventional wastewater technologies, such as high footprint, variable pollutant loads, and high maintenance. Hence, it can be used as a highly efficient method of treating wastewater.

Clustering micropollutants and estimating rate constants of sorption and biodegradation using machine learning approaches

Effluent from wastewater treatment plants is considered an important source of micropollutants (MPs) in aquatic environments. However, monitoring MPs in effluents is often inefficient owing to the variety in their types. Thus, this study derived marker constituents to estimate the behavior of MPs in each cluster using the self-organizing map (SOM), a machine learning-based clustering analysis method. In SOM analysis, the physicochemical properties, functional groups, and the initial biotransformation rules of 29 out 42 MPs were used to ultimately estimate the degradation rate constants of 13 MPs. Consequently, when the physicochemical properties and functional groups were considered, SOM analysis showed outstanding performance to label MPs with an accuracy value of 0.75 for each aerobic and anoxic condition. Based on the clustering results, 11 MPs were determined to be marker constituents under each aerobic and anoxic condition. Moreover, an estimation method for the rate constants of unlabeled MPs was successfully developed using the identified markers with the random forest classifier. The proposed algorithm could estimate both sorption and biotransformation of MPs regardless of dominant removal mechanisms, whether the MPs were removed by sorption or biotransformation. An accuracy of 0.77 was calculated for estimating rate constants under both aerobic and anoxic conditions, which is remarkably higher than those reported previously. The proposed procedure could be extended further to efficiently monitor MPs in effluents.