Degradation Of Organic Micropollutants Research Articles

Efficacy of 222 nm radiation on degradation of organic micropollutants in water

In this work, a dielectric barrier discharge (DBD) based exciplex lamp emitting radiation at far UV-C wavelength 222 nm has been reported. The developed UV source has been used for the degradation of organic micropollutants (OMPs), i.e., brilliant red 5B (BR-5B) and sulfamethoxazole (SMX) in a batch-scale reactor. The degradation of OMPs has been performed using an advanced oxidation process by loading hydrogen peroxide (H2O2) as a radical promotor. The degradation efficiency and energy yield in the case of BR-5B have been found twofold as compared to SMX at similar experimental conditions, because of its high molar absorption coefficient at 222 nm radiation.

New Perspectives on the Interactions between Adsorption and Degradation of Organic Micropollutants in Granular Activated Carbon Filters.

The removal of organic micropollutants in granular activated carbon (GAC) filters can be attributed to adsorption and biological degradation. These two processes can interact with each other or proceed independently. To illustrate the differences in their interaction, three 14C-labeled organic micropollutants with varying potentials for adsorption and biodegradation were selected to study their adsorption and biodegradation in columns with adsorbing (GAC) and non-adsorbing (sand) filter media. Using 14CO2 formation as a marker for biodegradation, we demonstrated that the biodegradation of poorly adsorbing N-nitrosodimethylamine (NDMA) was more sensitive to changes in the empty bed contact time (EBCT) compared with that of moderately adsorbing diclofenac. Further, diclofenac that had adsorbed under anoxic conditions could be degraded when molecular oxygen became available, and substantial biodegradation (≥60%) of diclofenac could be achieved with a 15 min EBCT in the GAC filter. These findings suggest that the retention of micropollutants in GAC filters, by prolonging the micropollutant residence time through adsorption, can enable longer time periods for degradations than what the hydraulic retention time would allow for. For the biologically recalcitrant compound carbamazepine, differences in breakthrough between the 14C-labeled and nonradiolabeled compounds revealed a substantial retention via successive adsorption-desorption, which could pose a potential challenge in the interpretation of GAC filter performance.

Biological degradation of organic micropollutants in GAC filters–temporal development and spatial variations

The capacity for organic micropollutant removal in granular activated carbon (GAC) filters for wastewater treatment changes over time. These changes are in general attributed to changes in adsorption, but may in some cases also be affected by biological degradation. Knowledge on the degradation of organic micropollutants, however, is scarce. In this work, the degradation of micropollutants in several full-scale GAC and sand filters was investigated through incubation experiments over a period of three years, using 14C-labeled organic micropollutants with different susceptibilities to biological degradation (ibuprofen, diclofenac, and carbamazepine), with parallel 16S rRNA gene sequencing. The results showed that the degradation of diclofenac and ibuprofen in GAC filters increased with increasing numbers of bed volumes when free oxygen was available in the filter, while variations over filter depth were limited. Despite relatively large differences in bacterial composition between filters, a degradation of diclofenac was consistently observed for the GAC filters that had been operated with high influent oxygen concentration (DO >8 mg/L). The results of this comprehensive experimental work provide an increased understanding of the interactions between microbial composition, filter material, and oxygen availability in the biological degradation of organic micropollutants in GAC filters.

Innovative mapping of groundwater redox status and cation exchange conditions in a GIS environment

Understanding the complexities of regional groundwater quality is crucial for managing groundwater resources. Groundwater quality assessment involves investigating specific dissolved groundwater components, for example, comparing them to established standards. To fully understand all aspects of groundwater quality, one should assess composite properties, one being the redox status and another being the cation exchange condition. The first may, for example, impose a control on the degradation of organic micropollutants. While groundwater numerical indices can be easily interpolated and visualised using various GIS applications, consistently mapping the redox status and cation exchange conditions as non-numerical indices remains challenging. Furthermore, no study has yet conducted a regional-scale mapping of cation exchange classes in a GIS environment using extensive groundwater samples. To deepen our understanding of these groundwater components, we employed ArcGIS in this study to map the redox and cation exchange conditions in two stages. First, we mapped the groundwater components of interest, including Cl, SO4, SO4/Cl, Fe, NO3 and base exchanges of Na and Mg, by the most appropriate interpolation method identified by a geostatistical analysis. Then, variables were combined, and the conditional functions were used in ArcMap's Math toolbox to determine redox status or cation exchange classes. Our innovative GIS method for mapping regional redox status and cation exchange conditions was developed for 3350 groundwater sampling locations in the coastal lowlands of the Western Netherlands. The method was successful, with generally 75%–95% similarity between predicted and observed situations for most classes. The introduced method is more straightforward than others and can map other non-numerical linguistic indices like Wilcox groundwater and irrigation water classifications, as well.

Elucidating the enhanced role of carbonate radical in propranolol degradation by UV/peroxymonosulfate system

Carbonate radical (CO3•−) has been proved to be an important secondary radical in advanced oxidation processes due to various radical reactions involved HCO3−/CO32−. However, the roles and contributions of CO3•− in organic micropollutant degradation have not been explored systematically. Here, we quantified the impact of CO3•− on the degradation kinetics of propranolol, a representative pollutant in the UV/peroxymonosulfate (PMS) system, by constructing a steady-state radical model. Substantially, the measured values were coincident with the predictive values, and the contributions of CO3•− on propranolol degradation were the water matrix-dependent. Propranolol degradation increased by 130% in UV/PMS system containing 10 mM HCO3−, and the contribution of CO3•− was as high as 58%. Relatively high pH values are beneficial for propranolol degradation in pure water containing HCO3−, and the contributions of CO3•− also enhanced, while an inverse phenomenon was shown for the effects of propranolol concentrations. Dissolved organic matter exhibited significant scavenging effects on HO•, SO4•−, and CO3•−, substantially retarding the elimination process. The developed model successfully predicted oxidation degradation kinetics of propranolol in actual sewage, and CO3•− contribution was up to 93%, which in indicative of the important role of CO3•− in organic micropollutant removal via AOPs treatment.

Fast sintering of titania monoliths for photocatalytic degradation of organic micropollutants

Scalable solutions to efficiently remove organic micropollutants from water are urgently needed to address the significant adverse health effects their accumulation causes on the environment and in humans. Solutions based on slurries of titania (TiO2) nanoparticles, while effective in the lab, cannot be scaled up due to cost and environmental concerns. Conversely, titania monolithic structures are not photoactive as high sintering temperatures result in the predominance of the non-photoactive rutile phase. In this work the combination of 3D printing and fast sintering allowed, for the first time, to obtain titania monoliths which are mechanically stable and retain their photoactivity. The latter arises from the anatase-rich composition of the monoliths, a result not possible using convectional sintering methods. To demonstrate their photoactivity, the porous monoliths were used in a recirculating flow reactor to degrade primidone, a widely used drug and ubiquitous micropollutant. Results for the best performing monolith showed a quantum yield value of 1.1 × 10−5and an electrical energy per order value of 13 kWh m−3, both significantly outperforming literature data. These results show a clear route to scaling-up the fabrication of photocatalytically active titania monoliths capable of effectively degrading organic micropollutants in water, whose presence is a major health and environmental hazard.

Fate of antibiotics and hormones during hydrothermal carbonization of poultry litter: degradation kinetics and toxicity assessment of filtrates and hydrochars

This study investigated degradation kinetics of five selected organic micropollutants (OMPs) present in poultry litter (namely: sulfadiazine, tetracycline, and doxycycline hyclate (antibiotics); estrone and 17-β-estradiol (hormones)) during hydrothermal carbonization (HTC) treatment as the temperature stepwise increased to 250 °C. All five pure OMPs were completely degraded before 250 °C was reached during the HTC process. Nevertheless, presence of poultry litter slowed down the degradation of OMPs. Through elemental mass balance calculation, it is noted that after 15 min (temperature less than 137 °C), 69–82% of organic carbon and 50–66% of organic nitrogen initially consisting part of the target antibiotics were fully mineralized. Both HTC filtrates and hydrochars obtained from poultry litter inhibited Escherichia coli and Bacillus subtilis growth. A combination of high salinity, high nutrients, dissolved organic carbon, and other ions in the filtrate as well as the adsorption of OMPs on hydrochars were probably the reason for the high toxicity.

Selective electrophilic attack towards organic micropollutants with superior Fenton-like activity by biochar-supported cobalt single-atom catalyst

The global shortage of freshwater and inadequate supply of clean water have necessitated the implementation of robust technologies for wastewater purification, and Fenton-like chemistry is a highly-promising approach. However, realizing the rapid Fenton-like chemistry for high-efficiency degradation of organic micropollutants (OMs) remains challenging. Herein, one novel system was constructed by a Co single-atom catalyst activating peroxymonosulfate (PMS), and the optimal system (SA-Co-NBC-0.2/PMS) achieved unprecedented catalytic performance towards a model OM [Iohexol (IOH)], i.e., almost 100% decay ratio in only 10 min (the observed rate constant: 0.444 min−1) with high electrophilic species 1O2 (singlet oxygen) generation. Theoretical calculations unveiled that Co-N4 sites preferred to adsorb the terminal-O of PMS (more negative adsorption energy than other O sites: –32.67 kcal/mol), promoting the oxidation of PMS to generate 1O2. Iodine (I)23 (0.1097), I24 (0.1154) and I25 (0.0898) on IOH with higher f– electrophilic values were thus identified as the main attack sites. Furthermore, 16S ribosomal RNA high-throughput sequencing and quantitative structure–activity relationship analysis illustrated the environmentally-benign property of the SA-Co-NBC-0.2 and the tapering ecological risk during IOH degradation process. Significantly, this work comprehensively checked the competence of the SA-Co-NBC-0.2/PMS system for organics abatement in practical wastewater.

Efficient charge carrier separation over carbon-rich graphitic carbon nitride for remarkably improved photocatalytic performance in emerging organic micropollutant degradation and H2 production

Graphitic carbon nitride (g-C3N4) shows great potentials in visible-light-driven catalytic oxidation of organic micropollutants to harmless products and reduction of water to H2 but suffers from drawback of sluggish charge carrier separation and transfer dynamics. To overcome this drawback, here a novel point defect engineering strategy, by a nicotinic acid or barbituric acid-assisted supramolecule self-assembly of dicyandiamide followed by thermal polymerization, is designed to prepare pyridine unit-incorporated g-C3N4 (CPyr-CNx) and carbon atom self-doped g-C3N4 (C-CNx). The strategy leads to well-regulated chemical structures of CPyr-CNx and C-CNx and thus the precisely controlled electronic structures. The CPyr-CNx and C-CNx both exhibit remarkably improved visible-light photocatalytic activity in degradation of emerging organic micropollutants (methylparaben, acetaminophen and bisphenol A) and water-splitting to H2 production in comparison of bulk g-C3N4 and carbon-rich g-C3N4 prepared by a direct thermal copolymerization of nicotinic acid or barbituric acid with dicyandiamide, and their photocatalytic redox activity depends on carbon doping level. Experimental results combined with theoretical simulations reveal that the superior photocatalytic redox performance of CPyr-CNx and C-CNx is mainly dominated by the significantly boosted charge carrier separation and transfer dynamics driven by carbon doping induced-local electric field and -midgap states, which finally generates abundant reactive oxidation species including •O2− anion radicals, •OH radicals and 1O2 for the deep oxidation of target organic micropollutants to significantly reduce their ecotoxicity; additionally, such efficient charge carrier separation and transfer also favors high mobility for free electron-involved photocatalytic H2 evolution reaction.

Membrane-based electrospun poly-cyclodextrin nanofibers coated with ZnO nanograins by ALD: Ultrafiltration blended photocatalysis for degradation of organic micropollutants

Membranes with simultaneous selective adsorption functionality and excellent photocatalytic response have been proposed for water remediation, especially for treating textile and industrial wastewater. However, state-of-the-art membranes are easily fouled by pollutant adsorption that impacts their reusability. Here we report the development of a crosslinked electrospun poly-cyclodextrin (Poly-CD) nanofiber (NF) membrane coated by atomic layer deposition (ALD) with ZnO nanograins for the removal of pollutants from wastewater. The inherent high affinity of poly-CD NFs favored the selective adsorption of cationic impurities, and the reactive oxygen species produced by photoirradiation of the ZnO surface effectively degraded adsorbed contaminants. The NFMs has signifies that, even under the dark, they have a removal efficiency of around 80% which may be due to the high adsorption nature. Further, these NFM are highly reusable while decorating the ZnO nanograins on the NFM, which degraded the adsorbed pollutant and opened up the active site to further adsorb the dye molecule on the poly-CD surface. Under the static mode, the ZnO(100)@poly-CD NFM achieved the highest MB removal efficiency of 94.3%, followed by ZnO(25)@poly-CD, ZnO(200)@poly-CD, and poly-CD, which had removal rates of 91.3%, 87.7%, and 83.1%, respectively in 120 min of photoirradiation. Modulating the photocatalytic reaction in a flow channel, ZnO(100)@poly-CD nanofibrous membranes (NFMs) achieved 2.19-fold higher removal efficiencies (98.6% in 60 min) in a flow-through filtration system than under static conditions (a non-filtration method). Furthermore, the flow-through mode promoted the mass transfer of pollutants through NFMs, which increased reactive oxygen species production by inhibiting electron-hole recombination. Furthermore, the inherent self-cleaning function conferred by the photocatalytic activity of surface ZnO increased membrane structural stability and provided a faster removal rate.

Nitrilotriacetic acid-assisted Mn(II) activated periodate for rapid and long-lasting degradation of carbamazepine: The importance of Mn(IV)-oxo species.

Periodate-based (PI, IO4-) oxidation processes for pollutant elimination have gained increased attention in recent years. This study shows that nitrilotriacetic acid (NTA) can assist trace Mn(II) in activating PI for fast and long-lasting degradation of carbamazepine (CBZ) (100% degradation in 2min). PI can oxidize Mn(II) to permanganate(MnO4-, Mn(VII)) in the presence of NTA, which indicates the important role of transient manganese-oxo species. 18O isotope labeling experiments using methyl phenyl sulfoxide (PMSO) as a probe further confirmed the formation of manganese-oxo species. The chemical stoichiometric relationship (PI consumption: PMSO2 generation) and theoretical calculation suggested that Mn(IV)-oxo-NTA species were the main reactive species. The NTA-chelated manganese facilitated direct oxygen transfer from PI to Mn(II)-NTA and prevented hydrolysis and agglomeration of transient manganese-oxo species. PI was transformed completely to stable and nontoxic iodate but not lower-valent toxic iodine species (i.e., HOI, I2, and I-). The degradation pathways and mechanisms of CBZ were investigated using mass spectrometry and density functional theory (DFT) calculation. This study provided a steady and highly efficient choice for the quick degradation of organic micropollutants and broadened the perspective on the evolution mechanism of manganese intermediates in the Mn(II)/NTA/PI system.

Review of Photochemical Activity of Dissolved Black Carbon in Aquatic Environments: Primary Influencing Factors and Mechanisms

Dissolved black carbon (DBC), the particular component of black carbon that can be dissolved in the water, which accounts for ~10% of the organic carbon cycle in the earth’s water body, is an essential member of the dissolved organic matter (DOM) pool. In contrast to DOM, DBC has a higher proportion of conjugated benzene rings, which can more efficiently encourage the degradation of organic micropollutants in the aquatic environment or more rapidly generate reactive oxygen species to photodegrade the organic micropollutants. Therefore, it is of great significance to study the changes and mechanisms of DBC photochemical activity affected by different factors in the water environment. Our work reviewed the main influencing factors and mechanisms of the photochemical activity of DBC. It focuses on the methodologies for the quantitative and qualitative investigation of the photochemical activity of DBC, the impact of the biomass source, the pyrolysis temperature of biochar, and the primary water environmental parameters on the photochemical activity of DBC and the indirect photodegradation of pollutants. Based on this, a potential future study of DBC photochemical activity has been prospected.

Fate of sulfamerazine by synchronous adsorption and photocatalysis dependent on natural organic matter properties

ABSTRACT Natural organic matter (NOM) can impede the removal of organic micro-pollutants (OMPs) through several mechanisms, including inner filter effect, competition with the target OMP, and radical scavenging, during synchronous adsorption/photocatalysis of multi-functional composites. In this study, the fate and inhibitory mechanisms of sulfamerazine (SMZ, a model OMP) that occurred in presence of seven different NOM samples (i.e. three standard NOM surrogates, a river water sample, a carbon filter effluent and two different sand filter effluents) during the adsorption/photocatalysis by a composite of Bi2O3-TiO2 supported on powdered activated carbon (Bi2O3-TiO2/PAC, abbreviated as BTP) when exposed to visible light irradiation were revealed. The results indicated that adsorption played a greater attribution than photocatalysis on SMZ removal. The primary impediment to the adsorption and photocatalytic degradation of SMZ was attributed to the presence of terrestrial-derived, humic-like NOM fractions with high aromaticity. The adsorption efficacy of SMZ was weakened by the absorption of NOM and its degradation products onto the BTP surface. The inner filter effect, competition between NOM and SMZ, and radical scavenging were responsible for the reduced photocatalysis of SMZ. In the cases of real water matrices, the presence of inorganic anion and co-existed NOM reduced the removal of SMZ. In summary, the findings of this work offer a comprehensive comprehension of the impact of NOM fractions on photocatalysis, emphasizing the necessity to examine the interplay between NOM and background inorganic constituents in the degradation of OMP via adsorption/photocatalysis.

Triphenylamine–Anthracene-Based Conjugated Microporous Polymers for the Detection and Photocatalytic Degradation of Organic Micropollutants

Triphenylamine (TPA)–anthracene (AN)-based conjugated microporous polymers (CMPs), namely PTPA-AN-9,10 and PTPA-AN-2,6, were synthesized by the Suzuki–Miyaura cross-coupling reaction of tris(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-amine with 9,10-dibromoanthracene and 2,6-dibromoanthracene, respectively. The as-synthesized polymers exhibited cauliflower-like nanoscale morphology , high Brunauer–Emmett–Teller surface area of 362 m2/g, and thermal stability up to 458 °C in the case of PTPA-AN-2,6. Interestingly, PTPA-AN-9,10 showed bright cyan fluorescence in tetrahydrofuran dispersion and exhibited fluorescence-based sensing of various nitroaromatics, where 2,4,6-trinitrophenol exhibited the lowest limit of detection of 34 μM and the highest Stern–Volmer constant (KSV) of 5.8 × 103 L mol–1. On the other hand, PTPA-AN-2,6 showed efficient photocatalytic reduction of various nitroaromatic micropollutants such as p-nitrophenol (p-NP) (k = 0.164 min–1 and turnover frequency (TOF) = 0.769 h–1) and degradation of Congo red from water with ultrafast kinetics (k = 0.047 min–1 and TOF = 0.024 h–1) which are much better than most of the previously reported CMPs. These polymers were recovered using simple filtration and were recycled four to five times without losing their catalytic efficiency significantly for p-NP reduction as well as dye degradation. In general, TPA-based CMPs have been used as efficient multitasking materials for the sensing of nitroaromatic micropollutants and photocatalytic degradation of Congo red dye as well as p-NP to its value-added product p-aminophenol.

Photocatalytic degradation of organic micropollutants under UV-A and visible light irradiation by exfoliated g-C3N4 catalysts

In the present study, the photocatalytic performance of exfoliated graphitic carbon nitride (g-C3N4) catalysts, with enhanced properties and response in UV and visible light irradiation, was evaluated for the removal of selected contaminants i.e., diuron, bisphenol A and ethyl paraben. Commercial TiO2 Degussa P25 was also used as a reference photocatalyst. The g-C3N4 catalysts demonstrated good photocatalytic activity which in some cases is comparable to TiO2 Degussa P25 leading to high removal percentages of the studied micropollutants under UV-A light irradiation. In contrast to TiO2 Degussa P25, g-C3N4 catalysts were also able to degrade the studied micropollutants under visible light irradiation. For all the studied g-C3N4 catalysts under both UV-A and visible light irradiation, the overall degradation rate decreases in the order of bisphenol A > diuron > ethyl paraben. Among the studied g-C3N4, the chemically exfoliated catalyst (g-C3N4-CHEM) showed superior photocatalytic activity under UV-A light irradiation due to its enhanced characteristics, such as pore volume and specific surface area and ~ 82.0 % in 6 min, ~75.7 % in 15 min and ~ 96.3 % in 40 min removals were achieved for BPA, DIU and EP, respectively. Under visible light irradiation, the thermally exfoliated catalyst (g-C3N4-THERM) demonstrated the best photocatalytic performance and the degradation ranged from ~29.5 to 59.4 % after 120 min. EPR data revealed that the three g-C3N4 semiconductors generate mainly O2•−, whereas TiO2 Degussa P25 generates both HO• and O2•−, the latter only under UV-A light irradiation. Nevertheless, the indirect formation of HO• in the case of g-C3N4 should also be considered. Hydroxylation, oxidation, dealkylation, dechlorination and ring opening were the main degradation pathways. The process proceeded without significant alterations in toxicity levels. Based on the results, heterogeneous photocatalysis using g-C3N4 catalysts is a promising method for the removal of organic micropollutants without the formation of harmful transformation products.

Selective degradation of organic micropollutants by activation of peroxymonosulfate by Se@NC: Role of Se doping and nonradical pathway mechanism

In this study, Se@NC-x decorated with Se was successfully prepared via two-step calcination with zeolitic imidazole framework (ZIF) as a precursor. Mechanistic studies show that PMS would be adsorbed onto the surface of Se@NC-900 to form an active complex (Se@NC-900/PMS*), and the active Se@NC-900/PMS* could oxidize phenol by the rapid decomposition of PMS. Specifically, electrons are extracted by Se@NC-900/PMS* and then transferred to the surface of Se@NC-900, which can trigger the degradation of phenol. Notably, it is found that the local charge redistribution caused by the doping of Se can activate the catalytic potential of the intrinsically inert carbon skeleton through density flooding theory (DFT) calculations. The XLogP, ΔE, VIP, and ELUMO (Se@NC/PMS)-HOMO (pollutants) and degradation rate constants of different micropollutants were correlated well linearly. This indicates that the Se@NC-900/PMS system has a great selectivity for the degradation of pollutants. Overall, these findings not only illustrate the role of Se in tuning the electronic structure of Se@NC-x to enhance the activation of PMS, but also bridge the gap in our knowledge about the physicochemical properties and degradation performance of Se@NC catalysts.

Isoporous catalytic ceramic membranes for ultrafast contaminants elimination through boosting confined radicals

Catalytic membrane based oxidation-filtration processes (AOP-CM), a derivative concept of membrane process that combines physical separation and chemical oxidation, offers a high-efficient water purification strategy. However, the application of AOP-CM was still hampered by the low heterogeneous AOPs efficiency of catalytic membranes. In order to improve the heterogeneous AOP efficiency, an isoporous AlOx/La2CoMnO6-δ ceramic membrane (IAPCM) with nano-confinement characteristics was prepared via sol–gel based block copolymer self-assembly route. Benefiting from the well-designed pore structure, IAPCM exhibited excellent pure water permeance (313 L·m−2·h−1·bar−1) and size-exclusion performance (complete rejection of MS2 phages with a diameter of ∼ 20 nm). With the addition of peroxymonosulfate (PMS), IAPCM achieved ultrafast degradation of organic micropollutants (e.g. atrazine, carbamazepine and sulfamethazine) at 0.5 bar (equivalent to a retention time of 4.3 × 10−4 s). Finite-Element analysis confirmed that high-concentration radical fields were generated in the confined nanoscale-pores within the isoporous La2CoMnO6-δ layer. The boosted mass transfer rates and high-concentration radical fields induced ultrafast degradation of micropollutants in IAPCM based oxidation-filtration system. This work highlights the significance of pore structure design for high-performance AOP-CM processes.

Highly efficient ZnO photocatalytic foam reactors for micropollutant degradation

The efficient removal of organic micropollutants, pharmaceuticals, pesticides, drugs, and others, remains an unsolved challenge in water treatment. Although photocatalysis has proven highly effective at degrading these substances, its large-scale implementation has been so far hampered by technical and economic concerns. This work describes the development and characterization of novel highly efficient, self-supporting photocatalytic ZnO foams for the degradation of organic micropollutants. A systematic investigation of flow rate, catalyst length and stability under both recirculating and single-pass conditions was conducted using carbamazepine as a UV-recalcitrant model pollutant. Under recirculation, 95 % degradation was achieved with photocatalyst quantum yield of 1.2 × 10−3 and electrical energy per order (EEO) as low as 24 kWh m−3, values outperforming current technology, slurry and immobilised systems. For single-pass tests, complete degradation was achieved in 30 min, with the quantum yield increasing to 6.3 × 10−3, and an EEO of 36 kWh m−3. These values also outperform those for slurries, immobilised and other foam photocatalyst reported in the literature under similar conditions. The low energy consumption of these newly developed photocatalytic foams, combined with their high quantum yield and stability, provides a realistic path towards practical implementation of photocatalytic processes in water treatment, addressing the limitations of existing slurry and immobilised photocatalytic technology.

Role of ammonia-oxidizing microorganisms in the removal of organic micropollutants during simulated riverbank filtration

Biodegradation plays an important role in the removal of organic micropollutants (OMPs) during riverbank filtration (RBF) for drinking water production. The ability of ammonia-oxidizing microorganisms (AOM) to remove OMPs has attracted increasing attention. However, the distribution of AOM in RBF and its role in the degradation of OMPs remains unknown. In this study, the behavior of 128 selected OMPs and the distribution of AOM and their roles in the degradation of OMPs in RBF were explored by column and batch experiments simulating the first meter of the riverbank. The results showed that the selected OMPs were effectively removed (82/128 OMPs, >70% removal) primarily by biodegradation and partly by adsorption. Inefficiently removed OMPs tended to have low molecular weights, low log P, and contain secondary amides, secondary sulfonamides, secondary ketimines, and benzyls. In terms of the microbial communities, the relative abundance of AOM increased from 0.1%–0.2% (inlet-sand) to 5.3%–5.9% (outlet-sand), which was dominated by ammonia-oxidizing archaea whose relative abundance increased from 23%–72% (inlet-sand) to 97% (outlet-sand). Comammox accounted for 23%–64% in the inlet-sand and 1% in the outlet-sand. The abundances of AOM amoA genes kept stable in the inlet-sand of control columns, while decreased by 78% in the treatment columns, suggesting the inhibition effect of allylthiourea (ATU) on AOM. It is observed that AOM played an important role in the degradation of OMPs, where its inhibition led to the corresponding inhibition of 32 OMPs (5/32 were completely suppressed). In particular, OMPs with low molecular weights and containing primary amides, secondary amides, benzyls, and secondary sulfonamides were more likely to be removed by AOM. This study reveals the vital role of AOM in the removal of OMPs, deepens our understanding of the degradation of OMPs in RBF, and offers valuable insights into the physiochemical properties of OMPs and their AOM co-metabolic potential.

Design of hydrodynamic cavitation assisted intensified tertiary treatment unit for effective degradation of organic micropollutants in pharmaceutical industrial effluent: A Case study with triclosan

Increasing occurrence of micropollutants and trace amount of persistent organic contaminants (POC's) in the wastewater streams even after the well-established conventional treatment is a threat to human health, aquatic entities, and constitute a formidable challenge for the ecological security. In this regard, hydrodynamic cavitation based advanced oxidation treatment has attracted extensive attention towards removal of such micro scale pollutants from wastewater streams in the present scenario. Hence, the present work demonstrates the design and application of a rotating hydrodynamic cavitation (RHC) reactor with stator-rotor arrangement for effective degradation of organic micropollutants (triclosan being taken as the target pollutant) from tertiary effluents occurring in the pharmaceutical sector. The process performance was evaluated through optimization of geometric parameters of the reactor, various operating parameters as well as by studying the sole and synergistic performance of the HC process combined with other AOPs. The maximum degradation of Triclosan (TCS) achieved by RHC alone was found to be 35.2 % and in synergism, with ozone, a maximum of 97.6 % degradation was observed. Further, to ensure the mineralization of the components, total organic carbon (TOC) contents of the samples were measured and the degradation pathway was predicted through LC-MS analysis. The techno-economic feasibility of the process were understood through economic and energetic analysis and technology transfer was done for replicating the same study for a pilot scale reactor.