Biological Oxidation Research Articles

Synthesis and Antihypoxic Activity of 2-aryl-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydroquinoline-4-carboxylic Acids and Their Reaction Products with Substituted Hydrazines

Introduction. Hypoxia is a violation of oxidative processes in tissues that occur when oxygen is insufficiently supplied to them or when its utilization is disrupted during biological oxidation. Chronic hypoxic damage plays an important role in the occurrence and development of various diseases, which necessitates the synthesis of new compounds with antihypoxic activity.Aim. The purpose of this study is to synthesize and investigate the antihypoxic activity of 2-aryl-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydroquinoline-4-carboxylic acids and their reaction products with substituted hydrazines.Materials and methods. 2-Aryl-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydroquinoline-4-carboxylic acids (I–VI) were obtained with high yields as a result of the interaction of 4-aroyl-2,4-dioxobutane acids with 3-amino-5,5-dimethylcyclohex-2-enone. Interaction of 2-aryl-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydroquinoline-4-carboxylic acids with benzyl- and (2-phenylethyl)hydrazines 5-aryl-2-benzyl- and 2-(2-phenylethyl)-8,8-dimethyl-3,7,8,9-tetrahydro-2H-pyrido[4,3,2-de]cinnoline-3-ones (VII–XII) were obtained. As a result, 12 compounds were synthesized. The study of the antihypoxic activity of the obtained compounds was carried out in vivo on a model of normobaric hypoxia with hypercapnia.Results and discussion. The synthesized compounds were tested for the presence of antihypoxic action. The most pronounced antihypoxic activity is characteristic of compounds VI and VIII, which have a methoxy group and a methyl radical in the para-position of the phenyl substituent at C5, respectively. The presence of chlorine in the structure of compound III, fluorine in compound X and the absence of substituents (compounds I and VII) contribute to the prohypoxic effect. According to the results of the study, both quinolincarboxylic acids and pyridocinnolines are potential antihypoxants.Conclusion. A comparative analysis of the antihypoxic activity of the synthesized compounds was carried out, the relationship between their structure and severity of action was established, the most active substances were identified.

Evaluation of a novel pyridinium cation-linked styryl-based boronate probe for the detection of selected inflammation-related oxidants

Reactive oxygen and nitrogen species (RONS) are a range of chemical individuals produced by living cells that contribute to the proper functioning of organisms. Cells under oxidative and nitrative stress show excessive production of RONS (including hydrogen peroxide, H2O2, hypochlorous acid, HOCl, and peroxynitrite, ONOO−) which may result in a damage proteins, lipids, and genetic material. Thus, the development of probes for in vivo detection of such oxidants is an active area of research, focusing on molecular redox sensors, including boronate-caged fluorophores. Here, we report a boronate-based styryl probe with a cationic pyridinium moiety (BANEP+) for the fluorescent detection of selected biological oxidants in vitro and in vivo. We compare the chemical reactivity of the BANEP+ probe toward H2O2, HOCl, and ONOO− and examine the influence of the major intracellular non-enzymatic antioxidant molecule, glutathione (GSH). We demonstrate that, at the physiologically relevant GSH concentration, the BANEP+ probe is efficiently oxidized by peroxynitrite, forming its phenolic derivative HNEP+. GSH does not affect the fluorescence properties of the BANEP+ and HNEP+ dyes. Finally, we report the identification of a novel type of molecular marker, with the boronate moiety replaced by the iodine atom, formed from the probe in the presence of HOCl and iodide anion. We conclude that the reported chemical reactivity and structural features of the BANEP+ probe may be a basis for the development of new red fluorescent probes for in vitro and in vivo detection of ONOO−.

Optimizing Autotrophic Sulfide Oxidation in the Oxygen-Based Membrane Biofilm Reactor to Recover Elemental Sulfur.

Biological sulfide oxidation is an efficient means to recover elemental sulfur (S0) as a valuable resource from sulfide-bearing wastewater. This work evaluated the autotrophic sulfide oxidation to S0 in the O2-based membrane biofilm reactor (O2-MBfR). High recovery of S0 (80-90% of influent S) and high sulfide oxidation (∼100%) were simultaneously achieved when the ratio of O2-delivery capacity to sulfide-to S0 surface loading (SL) (O2/S2- → S0 ratio) was around 1.5 (g O2/m2-day/g O2/m2-day). On average, most of the produced S0 was recovered in the MBfR effluent, although the biofilm could be a source or sink for S0. Shallow metagenomic analysis of the biofilm showed that the top sulfide-oxidizing genera present in all stages were Thauera, Thiomonas, Thauera_A, and Pseudomonas. Thiomonas or Pseudomonas was the most important genus in stages that produced almost only S0 (i.e., the O2/S2- → S0 ratio around 1.5 g of the O2/m2-day/g O2/m2-day). With a lower sulfide SL, the S0-producing genes were sqr and fccAB in Thiomonas. With a higher sulfide SL, the S0-producing genes were in the soxABDXYZ system in Pseudomonas. Thus, the biofilm community of the O2-MBfR adapted to different sulfide-to-S0 SLs and corresponding O2-delivery capacities. The results illustrate the potential for S0 recovery using the O2-MBfR.

Biological Oxidation of Manganese Mediated by the Fungus Neoroussoella solani MnF107

Manganese oxides are highly reactive minerals and influence the geochemical cycling of carbon, nutrients, and numerous metals in natural environments. Natural Mn oxides are believed to be dominantly formed by biotic processes. A marine Mn-oxidizing fungus Neoroussoella solani MnF107 was isolated and characterized in this study. SEM observations show that the Mn oxides are formed on the fungal hyphal surfaces and parts of the hypha are enveloped by Mn oxides. TEM observations show that the Mn oxides have a filamentous morphology and are formed in a matrix of EPS enveloping the fungal cell wall. Mineral phase analysis of the fungal Mn oxides by XRD indicates that it is poorly crystalline. Chemical oxidation state analysis of the fungal Mn oxides confirms that it is predominantly composed of Mn(IV), indicating that Mn(II) has been oxidized to Mn (IV) by the fungus.

A Transcriptome Array-Based Approach to Link SGLT-2 and Intrarenal Complement C5 Synthesis in Diabetic Nephropathy.

Diabetic nephropathy is a common microvascular complication of diabetes mellitus. It is characterized by progressive chronic kidney disease (CKD) with decline of kidney function by hyperfiltration. On a mechanistic level, activation of the complement system has been implicated in the pathogenesis of diabetic nephropathy. Therefore, here we pursued a transcriptome array-based approach to link intrarenal SGLT-2 and the synthesis of distinct complement components in diabetic nephropathy. Publicly available datasets for SLC5A2 (encoding SGLT-2) and complement system components were extracted specifically from microdissected tubulointerstitial (healthy controls: n = 31, diabetic nephropathy: n = 17) and glomerular compartments (healthy controls: n = 21, diabetic nephropathy: n = 12). First, we compared tubulointerstitial and glomerular log2SLC5A2 mRNA expression levels and confirmed a predominant synthesis within the tubulointerstitial compartment. Among various complement components and receptors, the only significant finding was a positive association between SLC5A2 and the tubulointerstitial synthesis of the complement component C5 in diabetic nephropathy (p = 0.0109). Finally, intrarenal expression of SLC5A2 was associated predominantly with pathways involved in metabolic processes. Interestingly, intrarenal complement C5 synthesis was also associated with enrichment of metabolic signaling pathways, overlapping with SLC5A2 for "metabolism" and "biological oxidations". These observations could be of relevance in the pathogenesis of diabetic nephropathy and implicate a mechanistic link between SGLT-2 and intrarenal complement synthesis.

Combination of advanced biological systems and photocatalysis for the treatment of real hospital wastewater spiked with carbamazepine: A pilot-scale study

Over the past few decades, the increase in dependency on healthcare facilities has led to the generation of large quantities of hospital wastewater (HWW) rich in chemical oxygen demand (COD), total suspended solids (TSS), ammonia, recalcitrant pharmaceutically active compounds (PhACs), and other disease-causing microorganisms. Conventional treatment methods often cannot effectively remove the PhACs present in wastewater. Hence, hybrid processes comprising of biological treatment and advanced oxidation processes have been used recently to treat complex wastewater. The current study explores the performance of pilot-scale treatment of real HWW (3000 L/d) spiked with carbamazepine (CBZ) using combinations of moving and stationary bed bio-reactor-sedimentation tank (MBSST), aerated horizontal flow constructed wetland (AHFCW), and photocatalysis. The combination of MBSST and AHFCW could remove 85% COD, 93% TSS, 99% ammonia, and 30% CBZ. However, when the effluent of the AHFCW was subjected to photocatalysis, an enhanced CBZ removal of around 85% was observed. Furthermore, the intermediate products (IPs) formed after the photocatalysis was also less toxic than the IPs formed during the biological processes. The results of this study indicated that the developed pilot-scale treatment unit supplemented with photocatalysis could be used effectively to treat HWW.

BIOCONVERSION OF MEAT PROCESSING FATTY WASTE USING YEAST Y.LIPOLYTICA

A technology for the utilization of fat waste from meat processing based on a combination of physical and chemical effects and biological oxidation is proposed. The main chemical and microbiological parameters of the fat-containing phase of effluents of meat processing enterprises were determined. It was established that in the process of holding waste in a sludge collector (1…13 days) as a result of the vital activity of autochthonous microorganisms, the fat content decreases from 87 % to 58 %. The dominant organism of the autochthonous microflora of the waste is the fungus Geotrichum.sp. It was established that Yarrowia lipolytica yeast, selected for the substrate, is the most promising fat biodestructor. A method of pretreatment of the fat-containing solid phase of fatty effluents has been developed, which increases the efficiency of their consumption by the Yarrowia lipolytica culture. The basis of the method is the ultrasonic dispersion of fat mass, as a result of which the bioavailability of the substrate increases and, as a result, the specific growth rate and yield of microbial biomass increases by 11 % and 30 %, respectively. The methods of seed preparation are proposed, which allow to increase the efficiency of the main process according to the indicators: biomass yield (by 10.1 %); specific growth rate (from 0.20 to 0.26 h–1); protein content (by 16.7 %). The methods include the selection (5…7 passages) of high-performance clones, which is carried out in the directions of increasing affinity to the substrate and stress resistance to the action of hydrogen peroxide (2.5 g/l). The obtained results showed that when using yeast Yarrowia lipolytica for the biodestruction of fatty effluents, it is advisable to use both top-up and continuous methods of cultivation, which do not lead to significant changes in the quality of the obtained biomass. Yeast leaching was not observed in the top-up mode at 24 % withdrawal of culture liquid per hour, and in the case of continuous mode - at a flow rate of 0.24 h–1, while the protein and lipid content was 42.7 % and 7.2 %, 41.4 % and 7.9 %, respectively.

Sustainability Assessment of Dihydroxyacetone (DHA) Production from Glycerol: A Comparative Study between Biological and Catalytic Oxidation Routes

Sustainability Assessment of Dihydroxyacetone (DHA) Production from Glycerol: A Comparative Study between Biological and Catalytic Oxidation Routes

Ozone micron bubble pretreatment for antibiotic resistance genes reduction in hospital wastewater treatment

Ozone micron bubble (OMB) treatment offers a promising approach to effectively eliminate Antibiotic Resistance Genes (ARGs) from infectious medical wastewater and mitigate the threat of drug resistance transmission. This study evaluated the effectiveness of OMB treatment for reducing ARGs from infectious medical wastewater in laboratory and on-site pilot treatment setups. In part, the presence of antibiotic residues in a hospital wastewater treatment plant (WWTP) and the impact of hospital wastewater on the distribution of ARGs in a wastewater collection system were also investigated. The results of wastewater collection system survey revealed a high prevalence of ARGs in the system, particularly mcr-1, largely originating from medical wastewater discharges. Furthermore, analysis of antibiotic residues in the hospital wastewater treatment system showed significant accumulation, particularly of quinolone antibiotics, in the biomass of the biological oxidation tank, suggesting a potential risk of ARG proliferation within the system. Comparison of wastewater samples from domestic and hospital WWTPs revealed a relatively higher abundance of ARGs in the latter, with differences ranging from 2.2 to sixfold between corresponding locations in the treatment plants. Notably, the biological oxidation unit of both WWTPs exhibited a greater proportion of ARGs among all sampled points, indicating the potential proliferation of ARGs within the biomass of the treatment units. ARG degradation experiments showed that OMB treatment resulted in a significantly lower CT value (9.3 mg O3 L−1 min) compared to ozone coarse bubble treatment (102 mg O3 L−1 min) under identical test conditions. Moreover, the use of OMB on site significantly reduced the accumulation of ARGs in hospital wastewater, underscoring its potential as an effective solution for mitigating ARG spread.

Rapid start-up of the biofilter for simultaneous manganese and ammonia removal at low temperature: Effects of phosphate and copper

In low-temperature environments, low nutrients such as inorganic salts limiting microbial proliferation further extended the start-up period of biofilters for drinking water treatment. This study explored the ammonia and manganese (Mn) removal performance and the relevant mechanisms under single and combined PO43− at 30 μg/L and Cu2+ at 10 μg/L. The start-up periods of R0 (control), R1 (Cu2+ single), R2 (PO43− single) and R3 (combined Cu2+ and PO43−) were 98, 82, 32 and 24 days, respectively. PO43− increased the concentration of extracellular polymeric substances (EPS) by stimulating cellular metabolism, which promoted the formation of biofilm. Additionally, the combined Cu2+ and PO43− significantly promoted the ammonia monooxygenase (AMO) and nitrite oxidoreductase (NXR) activities, which further facilitated the removal of ammonia. The combined Cu2+ and PO43− accelerated the conversion of NH4+-N to NO2−-N and NO2−-N to NO3−-N processes thereby reducing the inhibition of Mn removal by NH4+-N and NO2−-N, and the kinetics of biological manganese oxidation showed that the combined Cu2+ and PO43− increased the rate of Mn removal, which both promoted the Mn removal in the biofilters. Furthermore, the combined Cu2+ and PO43− supported the proliferation of functional microorganisms. In summary, the synergistic effect of Cu2+ and PO43− enhanced the Mn and ammonia removal performance and achieved rapid start-up of the biofilter at low temperatures.

Kinetic constraints for the formation of microniches for microaerophilic Fe(II) oxidation

Oxidation of Fe(II) by oxygen (O2) at circumneutral pH occurs abiotically or is mediated by microaerophilic Fe(II)-oxidizing bacteria. Abiotic Fe(II) oxidation(s) compete with microbial processes and the relative contribution of abiotic reactions depend on the chemical conditions, e.g. PO2, pH and the presence and identity of ferric (oxyhydr)oxide mineral surfaces, catalyzing the heterogeneous reaction. At circumneutral pH, abiotic Fe(II) oxidation proceeds rapidly, which raises the question how and to which extent neutrophilic microaerophilic Fe(II)-oxidizing bacteria can compete with chemical reactions and gain metabolic energy from microbial Fe(II) oxidation. In this study, we have investigated the environmental constraints for microaerophilic Fe(II) oxidation in a film layer characterized by diffusive supply of both atmospheric O2 (from the top) and dissolved Fe(II) (from the bottom) by use of a numerical model. A coupled diffusion–reaction model was tested at different chemical (pH and alkalinity gradients) and physical (film layer thickness) parameters to investigate their effects on the relative contributions of different reactions (abiotic homogeneous, heterogeneous and biological Fe(II) oxidation) to the overall (net) Fe(II) oxidation. A first order rate constant for biological oxidation was derived from experimental data from simplifcation of a Monod rate law to be 0.06 h−1. The simulations demonstrate distinct spatial oxidation rate patterns for all of the considered reactions. Microaerophilic Fe(II) oxidation is predominant at a uniform pH 6 and a film thickness z of 1 mm with minor importance at pH 7. Maximum biological rates were on the order of 7∙10-10 mol L−1 s−1 and are in the range of experimentally observed values. Minimum rates were close to the thermodynamic limit. In the presence of a pH gradient and z ≤ 1 mm, two distinct zones were observed: an upper zone dominated by abiotic Fe(II) oxidation (pH ∼ 7) and a lower zone dominated by microaerophilic Fe(II) oxidation (pH < 6.3), while the position and extent of the zones depend on the alkalinity. Such separation is strongly amplified for thinner films (z = 0.2 mm). The importance of heterogenous oxidation depends both on the pH and the amount of ferric (oxyhydr)oxides formed which increases with decreasing diffusive O2 supply at z > 1 mm. In combination with high resolution imaging of pH values in a biofilm, our simulations underpin the importance of pH gradients in allowing for the formation of microniches. The conditions suitable for microaerophilic Fe(II) oxidation can be predicted based on reaction time scales and three factors were identified to be especially important: i) a pH low enough (<6.3) to outcompete abiotic processes; ii) sufficiently fast diffusive supply of Fe(II) (e.g. by Fe(III)-reducing bacteria or chemical processes) with O2 concentrations below 150 μmol L−1; iii) sufficient energy gain from Fe(II) oxidation reaction considering the thermodynamic factor FT. We end by discussing strategies that Fe(II)-oxidizing microorganisms can employ to enhance their competitiveness against abiotic reactions.

Effect of Fe(II) on manganese removal in biofilters: Microbial community, formation of manganese oxide and related mechanisms

In this study, different concentrations of Fe(II) (0, 1.00, 7.00 mg/L) were introduced to investigate the effect on the removal of Mn(II) in the biofilter. Fe(II) significantly inhibited the removal of Mn and prolonged the start-up of biofilters, the start-up periods for the biofilters with different Fe(II) concentrations (0, 1.00 and 7.00 mg/L) were 24, 30 and 46 days, respectively. The study showed that Fe(II) and the Fe(III) oxyhydroxides generated from Fe(II) oxidation inhibited the removal of Mn(II) by affecting the proliferation of manganese-oxidizing bacteria (MnOB) and the activity of manganese oxides (MnOx) in the biofilter. On day 20, the total MnOB genera proportions were 13.44 %, 13.35 % and 20.09 % with different Fe(II) concentrations (0, 1.00, 7.00 mg/L), respectively. The addition of Fe(II) significantly impeded the proliferation of Pseudomonas, Acinetobacter and Arthrobacter, but enhanced the proliferation of Hyphomicrobium and Sphingopyxis. On day 60, the abundance of total MnOB was reduced obviously in three biofilters (6.95 %, 6.44 % and 9.76 %). This indicated that the biological oxidation of Mn dominates during the initial operation stage of the filter layer, while the chemical auto-catalytic oxidation of active MnOx dominates in the later stages. The contribution of Mn removal by biological oxidation was positively correlated with the abundance of MnOB, and batch experiments confirmed this conclusion. Moreover, the addition of Fe(II) reduced MnOx activity by suppressing the production of high-reactivity intermediate-Mn(III), and Fe(III) oxyhydroxides hindered the formation of mature MnOx films on the surface of the filter media.

Study on influencing factors of Coal Microbial Flotation Desulfurization

This study systematically investigates the influence of various factors on microbial flotation desulfurization of coal, with a particular focus on removing organic sulfur. The parameters examined encompass particle size, pretreatment time, bacteria species, bacterial concentration, forms of sulfur occurrence, ash yield, and coal rank. The study aims to develop a thorough understanding of the desulfurization process and establish a theoretical framework for advancing clean coal technology and efficient coal utilization. Stringent control was maintained over parameters such as particle size, pretreatment time, bacterial species, and bacterial concentration. Various forms of sulfur and coal rank were considered to evaluate their impact on desulfurization. Correlation analysis was conducted to investigate the relationship between ash yield reduction and the extent of desulfurization. Thiobacillus ferrooxidans and Rhodotorula mucilaginosa were employed in the experimental setup to assess their efficacy in microbial flotation desulfurization. The results demonstrate that microbial flotation desulfurization achieved the highest removal efficiency for organic sulfur, reaching 79.65%. Notably, the desulfurization of organic sulfur exhibited an increasing trend with decreasing coal rank. Correlation analysis reveals a positive correlation between ash yield and desulfurization, suggesting that high mineral matter content in coal facilitates microbial flotation desulfurization and enhances biological oxidation. Comparative analysis of single strain and mixed strain experiments revealed varying degrees of improvement in desulfurization extent, with the mixed-bacteria system exhibiting the most effective removal of organic sulfur, which suggests that Rhodotorula mucilaginosa can significantly enhance microbial flotation desulfurization. Overall, this research provides systematic insights into the influence of process conditions and geological factors on coal desulfurization. The study establishes a theoretical foundation for the development of clean coal technology and the efficient utilization of coal resources, contributing to the advancement of environmentally friendly practices in the coal industry.

The interactive effect of environmental factors on methane oxidation in a continental landfill bio-cover

In the current study, the interactive effect of environmental factors was studied in an active bio-cover after two years of operation and experiencing a wide range of temperatures across the seasons (<0 ℃ to >45 ℃) in a continental climate condition. The studied environmental factors includes moisture content (MC), temperature, and initial CH4 concentration that were observed to have the most controlling effect on the CH4 oxidation in the bio-cover over two years of field-scale measurements. Therefore, selected environmental factors were modeled to determine their interactive effect on CH4 oxidation potential in the bio-cover material including Yard Waste and Leaf Compost (YWLC) and Biosolids Compost (BSC) (1:4). The compost was taken from the active bio-cover in October 2018 with a compost temperature between 10 and 15 ℃. The expectation was that the methanotrophic biomass would be adapted to the seasonal in situ conditions. While the effects of individual environmental factors on biological CH4 oxidation have been described in a previous long term study, their interactive effects in the bio-cover compost materials had not been explored. Therefore, interactive effects of environmental factors were investigated with a Box–Behnken Design adopting a Response Surface Methodology to develop a statistical model and determine the optimal conditions for the CH4 oxidation in the compost mixture sampled. To do so, 17 batch incubations were conducted at the MC of 20 %, 40 %, and 60 %, temperatures of 15, 30, and 45 ℃, and initial CH4 concentrations of 10 %, 20 %, and 30 %. The maximum value of CH4 oxidation rate obtained from the model was 2.20 mgCH4.gdw−1.d−1 with optimum MC of 47.4 %, temperature of 32.7 ℃, and initial CH4 concentration of 23.8 %. A parabolic curve for MC and temperature was observed simultaneously, and there was no significant difference between CH4 oxidation rates at 20 % and 30 % initial CH4 concentration. The model was then validated experimentally. The results of this study showed that the current compost mixture, collected from this bio-cover accustomed to fluctuations in temperature and MC, selected for a community of methanotrophs capable of effective operation over a wide range of summer compost temperatures and MCs, but was ill-adapted to spring and fall temperatures when the bio-cover temperature descends below 15 ℃, including when the bio-cover sample was taken for the current analyses.

Recent advances in methanol production from methanotrophs.

Methanol, the simplest aliphatic molecule of the alcohol family, finds diverse range of applications as an industrial solvent, a precursor for producing other chemicals (e.g., dimethyl ether, acetic acid and formaldehyde), and a potential fuel. There are conventional chemical routes for methanol production such as, steam reforming of natural gas to form syngas, followed by catalytic conversion into methanol; direct catalytic oxidation of methane, or hydrogenation of carbon dioxide. However, these chemical routes are limited by the requirement for expensive catalysts and extreme process conditions, and plausible environmental implications. Alternatively, methanotrophic microorganisms are being explored as biological alternative for methanol production, under milder process conditions, bypassing the requirement for chemical catalysts, and without imposing any adverse environmental impact. Methanotrophs possess inherent metabolic pathways for methanol production via biological methane oxidation or carbon dioxide reduction, thus offering a surplus advantage pertaining to the sequestration of two major greenhouse gases. This review sheds light on the recent advances in methanotrophic methanol production including metabolic pathways, feedstocks, metabolic engineering, and bioprocess engineering approaches. Furthermore, various reactor configurations are discussed in view of the challenges associated with solubility and mass transfer limitations in methanotrophic gas fermentation systems.

Bioaugmentation treatment of coal chemical reverse osmosis concentrate in biological contact oxidation system coupled with ozone pretreatment

With the zero discharge requirements of coal chemical industry in China, reverse osmosis technology and fractional crystallization technology have been applied to recover water and valuable salts. Organic matter significantly inhibits salt crystallization, therefore it is urgent to remove organic matter from coal chemical reverse osmosis concentrate (CCROC) efficiently and economically. Common biological systems have the bottlenecks of long start-up period and poor pollutants removal efficiency due to the inhibition of toxic compounds and high salinity to the microorganisms. In this work, a self-prepared halotolerant bacteria preparation (HBP, mixture of screened Bacillus, Pseudomonas, and Halomonas with strong degrading capacity of CCROC) was inoculated into different biochemical systems (activated sludge and biological contact oxidation in sequencing batch reactor) to try to enhance the pollutants removal of extremely refractory CCROC (BOD5/COD of 0.05). The results showed that HBP increased the total organic carbon (TOC) removal efficiency from 8% to 15% in activated sludge system. In addition, biological contact oxidation reactor (BCOR) could better retain the HBP, leading to a higher TOC removal efficiency (20%). Typically, the inoculation of HBP without activated sludge in BCOR contributed to the highest TOC removal (28%). The class Bacilli (genus Bacillus) was dominant during the start-up and stable period of this bioaugmented treatment process. To further increase the pollutants removal, ozone oxidation pretreatment was conducted prior to biological treatment to break the ring structures. The total TOC removal increased to 42% under the combined treatment, while the dominant classes in biofilms shifted to Actinobacteria, Gammaproteobacteria, Alphaproteobacteria, and Bacteroidia. This study provided an effective approach for CCROC treatment with industrial application potentials.

Study on the Effect of AO-Coupled Constructed Wetlands on Conventional and Trace Organic Pollutant Treatment.

In this study, a pilot-scale integrated process was developed, which combined the integrated biological contact oxidation technology (AO) and the improved constructed wetland technology. The results showed significant removal efficiency for both conventional and trace organic pollutants. The average removal efficiencies for COD, NH4+-N, and TP were 78.52, 85.95, and 49.47%, respectively. For trace organic pollutants, triclocarban, triclosan, and sulfadiazine, the removal efficiencies reached 60.14, 57.42, and 84.29%, respectively. The AO stage played a crucial role in removing trace organic pollutants, achieving removal efficiencies of 37.28, 43.44, and 83.82% for triclocarban, triclosan, and sulfadiazine, respectively. Subsequent treatment using improved constructed wetland technology with coal slag + gravel fillers demonstrated the highest removal efficiency, with average efficiencies of 68.66, 63.38, and 81.32% for triclocarban, triclosan, and sulfadiazine, respectively. Correlation analysis revealed positive correlations between temperature, precipitation, and the removal efficiency of COD, NH4+-N, and TP, while negative correlations were observed with the removal efficiency of triclocarban, triclosan, and sulfadiazine. Furthermore, the influent concentrations of triclocarban and triclosan were significantly negatively correlated with the removal efficiency of COD and TP. The presence of triclocarban and triclosan potentially reduced the microbial diversity and hindered sludge sedimentation performance.

BITUMEN PLANT WASTEWATER TREATMENT

Wastewater from oil refineries is considered toxic and dangerous to the environment and human health, because their composition is complex, they are capable of forming other compounds, undergoing changes over time, and the constancy of most organic compounds, the strength of chemical bonds, undoubtedly complicate their biological and chemical oxidation and decomposition. Treatment plants consist of stages of mechanical, physico-chemical and biological treatment. In most cases, even a combination of these purification methods cannot purify the water to the required level. Considering that water is the only consumable resource, it is important not only to purify it in accordance with the requirements, but also to update the purification methods for use in other necessary industries. The issue under consideration is aimed at wastewater treatment of the Aktau bitumen processing plant. The article presents the results of a study of the evaporation of wastewater from a bitumen plant in a solar installation without reagents. Laboratory experiments have shown the possibility of wastewater treatment by distillation at lower temperatures and pressures. Along with the wastewater treatment of a bitumen plant without reagents, it can also be considered as a source of the release of precious metals.

A biological strategy for sulfide control in sewers: Removing sulfide by sulfur-oxidizing bacteria

Sulfide produced from sewers is considered one of the dominant threats to public health and sewer lifespan due to its toxicity and corrosiveness. In this study, we developed an environmentally friendly strategy for gaseous sulfide control by enriching indigenous sulfur-oxidizing bacteria (SOB) from sewer sediment. Ceramics acted as bio-carriers for immobilizing SOB for practical use in a lab-scale sewer reactor. 16 S rRNA gene sequences revealed that the SOB consortium was successfully enriched, with Thiobacillus, Pseudomonas, and Alcaligenes occupying a dominant abundance of 64.7% in the microbial community. Metabolic pathway analysis in different acclimatization stages indicates that microorganisms could convert thiosulfate and sulfide into elemental sulfur after enrichment and immobilization. A continuous experiment in lab-scale sewer reactors confirmed an efficient result for sulfide removal with hydrogen sulfide reduction of 43.9% and 85.1% under high-sulfur load and low-sulfur load conditions, respectively. This study shed light on the promising application for sewer sulfide control by biological sulfur oxidation strategy.

Suaeda australis and its associated rhizosphere microbiota: a comparison of the nutrient removal potential between different shrimp farm sediments in New Caledonia.

Shrimp rearing generate organic waste that is trapped in the pond sediment. In excess, these wastes may impair aquaculture ecosystem and shrimps' health. To promote the biological oxidation of accumulated organic waste, the pond is drained and dried at the end of each production cycle. However, this practice is not always conducive to maintaining microbial decomposition activities in sediments. Shrimp production in New Caledonia is no exception to this problem of pollution of pond bottoms. One promising way of treating this waste would be bioremediation, using a native halophyte plant and its microbiota. Thus, this study explored the nutrient removal potential of Suaeda australis and its microbiota on sediments from four shrimp farms. Suaeda australis was grown in an experimental greenhouse for 6 months. In order to mimic the drying out of the sediments, pots containing only sediments were left to dry in the open air without halophytes. An analysis of the chemical composition and active microbiota was carried out initially and after 6 months in the sediments of the halophyte cultures and in the dry sediments for each farm, respectively. In the initial state, the chemical parameters and the microbial diversity of the sediment varied considerably from one farm to another. Growing Suaeda australis reduced the nitrogen, phosphorus and sulfur content in all type of sediment. However, this reduction varied significantly from one sediment to another. The rhizosphere of Suaeda australis is mainly composed of micro-organisms belonging to the Alphaproteobacteria class. However, the families recruited from this class vary depending on the farm in question. Depending on the sediment, the variation in microbiota leads to different putative biochemical functions. For two of the farms, a similar reduction in nitrogen concentration was observed in both dry and cultivated sediments. This suggests that certain initial chemical characteristics of the sediments influence the nutrient removal efficiency of Suaeda australis. Our study therefore highlights the need to control the pH of sediments before cultivation or in dry sediments in order to ensure optimal microbial decomposition of organic waste and nutrient cycling.