Role of cycle duration on the formation of quinoline-degraded aerobic granules in the aspect of sludge characteristics, extracellular polymeric substances and microbial communities

Characteristics and Mechanisms of Simultaneous Quinoline and Ammonium Nitrogen Removal by a Robust Bacterium Pseudomonas stutzeri H3

The discharge of organic and inorganic nitrogenous pollutants in wastewater leads to eutrophication and disrupts the ecological balance. Therefore, the pressing need for an effective treatment method has become increasingly evident. A robust bacterium Pseudomonas stutzeri H3 capable of simultaneous organic and inorganic nitrogen removal was isolated from the activated sludge in the coking wastewater treatment system. The optimal conditions for the simultaneous removal of ammonium nitrogen and quinoline were as follows: C/N ratio of 15-20, initial pH of 7-8, culture temperature of 30 °C, and shaking speed of 150-300 rpm. At 200 mg/L ammonium nitrogen and 100 mg/L quinoline, strain H3 achieved above 90% of removal efficiency, exhibiting excellent simultaneous nitrogen removal capabilities. The outstanding nitrogen removal efficiencies in the presence of quinoline and different inorganic nitrogen sources further confirmed the simultaneous organic and inorganic nitrogen removal capability of strain H3. The whole genome sequencing and nitrogen metabolic intermediates determination of strain H3 were performed to elucidate the gene function annotations, nitrogen removal function genes, and nitrogen metabolic pathways. The findings provide a promising pathway to treat the organic and inorganic nitrogenous pollutants in wastewater.

Behavior of carbon source type on the construction of aerobic granular sludge system and its removal of quinoline: A tortoise and hare race between starch and phenol

Coal chemical wastewater contains high concentrations of toxic organic pollutants such as quinoline and phenol. Microorganisms in aerobic granular sludge (AGS) are known to efficiently degrade organic matter. This study systematically compared the cultivation characteristics of quinoline-degrading aerobic granular sludge using starch (R1), a common carbon source, and phenol (R2), a toxic carbon source, as co-metabolizing substrates. The results indicated that R2 was more conducive to improving sludge settleability, biomass retention, and the growth of quinoline-degrading bacteria when a low quinoline concentration (30 mg/L) was applied. However, as the quinoline concentration increased, the granular sludge cultured with starch eventually outperformed phenol as a co-metabolizing substrate in terms of settling performance, biomass, and pollutant removal. Analysis of the pollutant degradation characteristics during a typical operation cycle revealed that the time required to degrade quinoline to approximately 5.5 mg/L was 150 min in R1 and 420 min in R2, indicating a higher reaction rate in R1. Acidovorax was identified as the dominant quinoline-degrading bacterium in both reactors. In addition, microbial differential analysis and functional genes indicated more pronounced bacterial differentiation in R1, enriched in Firmicutes and Deinococcaceae. the relative abundance of enzymes associated with quinoline degradation was higher in R1.

Effect of reactive oxygen species (ROS) produced by pyridine and quinoline on NH4+-N removal under phenol stress: The shift of nitrification pathway and its potential mechanisms

Pyridine and quinoline are typical nitrogenous heterocyclic compounds with different structures that are found in coking wastewater. However, neither the corresponding mechanism nor its effect on the degradation of NH4+-N under phenol stress is known. In this study, the effects of pyridine and quinoline degradation on NH4+-N removal under phenol stress were evaluated using three lab-scale sequencing batch reactors. The average NH4+-N removal efficiencies of the reactors were 99.46 %, 88.86 %, and 98.64 %. With the increased concentration of pyridine and quinoline, NH4+-N and NO3--N accumulated to 58.37 mg/L and 141.37 mg/L, respectively, due to the lack of an electron donor and anaerobic environment. The addition of pyridine and quinoline significantly improved antioxidant response and altered the nitrification pathway. The nitrification process shifted from the mediation of amo and hao to the mediation of Ncd2 due to oxidative stress induced by pyridine and quinoline. Furthermore, oxidative stress interferes with the metabolism of carbon sources, resulting in decreased biomass. These results provide a new perspective for coking wastewater treatment processes.

Inhibition of denitrification and enhancement of microbial interactions in the AGS system by high concentrations of quinoline

Quinoline represents a highly toxic and structurally stable nitrogen-containing heterocyclic compound in coking wastewater, posing a potential threat to human beings and the ecological environment. In this study, we investigated the impact of gradually elevating quinoline concentration on pollutant removal efficiency, sludge characteristics, microbial community and their interactions in the aerobic granular sludge (AGS) system. The results demonstrated that AGS was capable of effectively degrading quinoline, with a final removal rate of 90 mg/L quinoline reaching 98.54 ± 0.28%. Notably, the denitrification process was significantly impeded in the presence of 90 mg/L quinoline, with the Phase D effluent displaying a notably high NO3--N concentration of 37.09 ± 21.81 mg/L, primarily attributed to the reduced abundance of norank_f_A4b bacteria. As the quinoline concentration increased, the sludge particle size diminished from 3.46 to 2.60 mm, while the settling performance deteriorated significantly, escalating from 31.29 ± 1.63 mL/g to 62.32 ± 2.87 mL/g. Meanwhile, the protein (PN) content in EPS gradually increased (from 19.87 ± 0.88 mg/g MLVSS to 51.22 ± 3.21 mg/g MLVSS), while the polysaccharide (PS) content fluctuated. Quinoline profoundly modified microbial community composition and structure, with deterministic processes dominating community assembly. Network analysis indicated intensified and complex microbial interactions at 90 mg/L quinoline, characterized by significantly higher positive correlations. In addition, rare taxa (RT) dominated the network nodes, with 74 of 93 key species belonging to RT, highlighting their pivotal roles in sustaining system functions and strengthening microbial connections. This study provides new insights into the effects of quinoline on microbial community structure and interactions in AGS system.

Mechanism of self-supporting montmorillonite composite material for bio-enhanced degradation of chlorotetracycline: Electron transfer and microbial response

The efficient degradation of antibiotics holds significant implications for mitigating environmental pollution. This study synthesized a montmorillonite chitosan composite material (MMT-CS) using the gel template method. Subsequently, a bio-enhanced reactor was constructed to facilitate the degradation of chlorotetracycline (CTC). The addition of MMT-CS composite material enables the degradation of different concentrations of CTC. MMT-CS, a conductive carrier, effectively promotes microbial adhesion and boosts the metabolic activity of functional microorganisms. Additionally, it facilitates the maintenance of microbial activity under CTC pressure by promoting the secretion of extracellular polymeric substances, increasing critical enzyme activity, and enhancing the electron transfer capacity within the system. In this MMT-CS bio-enhanced process, Paracoccus (11.4%) and Bacillus (3.9%) are utilized as essential bacteria genes. The results of metabolic pathways prediction indicated significant enhancements in membrane-transport, nucleotide-metabolism, replication-repair, and lipid-metabolism. Thus, the developed self-supporting MMT-CS bio-enhanced process ensured the stability of the system during the removal of antibiotics.

Biological activity and molecular mechanism of inactivation of Microcystis aeruginosa by ultrasound irradiation

Harmful algal blooms (HABs) significantly impact on water quality and ecological balance. Ultrasound irradiation has proven to be an effective method for algal control. Nevertheless, the molecular mechanisms underlying the inactivation of M. aeruginosa by ultrasound are still unknown. In this study, the physiological activity and molecular mechanism of algal cells exposed to different frequencies of ultrasound were studied. The results indicated a pronounced inhibition of algal cell growth by high-frequency, high-dose ultrasound. Moreover, with increasing ultrasound dosage, there was a higher percentage of algal cell membrane ruptures. SEM and TEM observed obvious disruptions in membrane structure and internal matrix. Hydroxyl radicals generated by high-frequency ultrasound inflicted substantial cell membrane damage, while increased antioxidant enzyme activities fortified cells against oxidative stress. Following 2 min of ultrasound irradiation at 740 kHz, significant differential gene expression occurred in various aspects, including energy metabolism, carbohydrate metabolism, and environmental information processing pathways. Moreover, ultrasound irradiation influenced DNA repair and cellular apoptosis, suggesting that the algal cells underwent biological stress to counteract the damage caused by ultrasound. These findings reveal that ultrasound irradiation inactivates algae by destroying their cell structures and metabolic pathways, thereby achieving the purpose of algal suppression.

Novel insights into the impact of anticancer drugs on the performance and microbial communities of a continuous-flow aerobic granular sludge system

Anticancer drugs are frequently found in domestic wastewater, but knowledge of their impacts on wastewater treatment processes is limited. The effects of three levels of concentrations (low, medium, and high) of three anticancer drugs on physicochemical parameters and prokaryotic communities of a continuous-flow aerobic granular sludge (AGS) system were examined. Drugs at medium and high concentrations reduced the removal of total nitrogen and organic matter during the first 15 days of operation by approximately 15-20 % compared to a control, but these effects disappeared afterward. Removal efficiencies of drugs were in the range of 51.2-100 % depending on the concentration level. Drugs at medium and high concentrations reduced the abundance and diversity and altered the composition of prokaryotic communities. Specific taxa were linked to variations in performance parameters after the addition of the drugs. This study provides improved knowledge of the impacts of anticancer drugs in AGS systems operated in continuous-flow reactor.

Changes in microbial community during hydrolyzed sludge reduction

In this study, the effects of different enzymes (lysozyme, α-amylase and neutral protease) on sludge hydrolysis efficiency and microbial community in sequencing batch reactor (SBR) were introduced. The results showed that the hydrolysis efficiencies of the three enzymes were 48.5, 22.5 and 31%, respectively, compared with the accumulated sludge discharge of the blank control group. However, it has varying degrees of impact on the effluent quality, and the denitrification and phosphorus removal effect of the system deteriorates. The lysozyme that achieves the optimal sludge hydrolysis effect of 48.5% has the greatest impact on the chemical oxygen demand (COD), total nitrogen (TN), and nitrate nitrogen (NO3--N) of the effluent. The sludge samples of the control group and the groups supplemented with different enzyme preparations were subjected to high-throughput sequencing. It was found that the number of OTUs (Operational Taxonomic Units) of the samples was lysozyme > α-amylase > blank control > neutral protease. Moreover, the abundance grade curve of the sludge samples supplemented with lysozyme and α-amylase was smoother, and the community richness and diversity were improved by lysozyme and α-amylase. The species diversity of the sludge supplemented with lysozyme and neutral protease was great, and the community succession was obvious. The introduction of enzymes did not change the main microbial communities of the sludge, which were mainly Proteobacteria, Actinobacteria and Bacteroidetes. The effects of three enzyme preparations on sludge reduction and microbial diversity during pilot operation were analyzed, the gap in microbial research was filled, which provided theoretical value for the practical operation of enzymatic sludge reduction.

Sunlight-driven intimately coupled photocatalysis and biodegradation (SDICPB): A sustainable approach for enhanced detoxification of triclosan

Triclosan is considered as recalcitrant contaminant difficult to degrade from the contaminated wastewater. Thus, promising, and sustainable treatment method is necessary to remove triclosan from the wastewater. Intimately coupled photocatalysis and biodegradation (ICPB) is an emerging, low-cost, efficient, and eco-friendly method for the removal of recalcitrant pollutants. In this study BiOI photocatalyst coated bacterial biofilm developed at carbon felt for efficient degradation and mineralization of triclosan was studied. Based on the characterization of BiOI prepared using methanol had lower band gap 1.85 eV which favors lower recombination of electron-hole pair and higher charge separation which ascribed to enhanced photocatalytic activity. ICPB exhibits 89% of triclosan degradation under direct sunlight exposure. The results showed that production of reactive oxygen species hydroxyl radical and superoxide radical anion played crucial role in the degradation of triclosan into biodegradable metabolites further the bacterial communities mineralized the biodegradable metabolites into water and carbon dioxide. The confocal laser scanning electron microscope results emphasized that interior of the biocarrier shows a large number of live bacterial cells existing in the photocatalyst-coated carrier, where the little toxic effect on bacterial biofilm occurred on the exterior of the carrier. The extracellular polymeric substances characterization result remarkable confirms that which could act as sacrificial agent of photoholes further helped by preventing the toxicity to the bacterial biofilm from the reactive oxygen species and triclosan. Hence, this promising approach can be a possible alternative method for the wastewater treatment polluted with triclosan.