Individual and combined effects of silver nanoparticles and polyvinyl chloride microplastics on the activity and abundance of ammonia-oxidizing microorganisms from a wastewater treatment system

Response of wastewater treatment performance and bacterial community to original and aged polyvinyl chloride microplastics in sequencing batch reactors.

Abstract. Saukoly SA, Meitiniarti VI, Nugroho RA, Krave AS. 2024. Ammonium enrichment reduces the diversity and changes the composition of ammonia-oxidizing microbial communities in agricultural soil media. Biodiversitas 25: 916-923. Nitrification is the process of ammonium oxidation to form nitrites and nitrates. Ammonium availability in the soil is one of the factors influencing the activity, abundance, and diversity of ammonia-oxidizing microorganisms (AOM). This study aimed to determine the effect of enriching a soil media with different ammonium concentrations on the abundance and diversity of AOM as well as the potential for nitrification. Soil as the media was prepared from an agricultural land receiving cow dung sewage. The media was then placed in the microcosms, and was added to a nitrification medium containing ammonium at three levels; 0 (control soil), 200 (low ammonium-enriched soil), and 500 mg L-1 (high ammonium-enriched soil). The microcosms were further incubated for 42 days at room temperature. The nitrification potential determination was based on the formation of nitrite from ammonium oxidation. The abundance of AOM and the potential nitrification were measured every 14-day interval, including day 0 as the initial condition. The AOM composition was analyzed based on the similarity level of the amoA gene sequence to the NCBI BLAST GenBank database. However, this analysis was only conducted for the control and high ammonium-enriched soil. This study indicated that ammonium enrichment increased the nitrification activity and the abundance of AOM, but it decreased the diversity of AOM communities. There were positive correlations between nitrification and nitrate potential, as well as between ammonium content and AOM abundance. Negative correlations appeared between pH and nitrification potential, nitrate concentrations, ammonium concentrations, and MPN. The diversity of ammonium-oxidizing archaea (AOA) in the control soil was higher than in the high ammonium-enriched soil. The enrichment with ammonium also changed the AOA composition. The Candidatus Nitrosocosmicus oleophilus strain of the MY3 chromosome was the most dominant archaea in the control and high ammonium-enriched soil. This implies that the high diversity of AOA in this soil may be beneficial for further use of the soil as a source for inocula in the development of nitrifiers-based biofertilizers.

The effect of microplastics (MPs) retained in waste activated sludge (WAS) on anaerobic digestion (AD) performance has attracted more and more attention. However, their effect on thermophilic AD remains unclear. Here, the influence of polyvinyl chloride (PVC) MPs on methanogenesis and active microbial communities in mesophilic (37 °C) and thermophilic (55 °C) AD was investigated. The results showed that 1, 5, and 10 mg/L PVC MPs significantly promoted the cumulative methane yield in mesophilic AD by 5.62%, 7.36%, and 8.87%, respectively, while PVC MPs reduced that in thermophilic AD by 13.30%, 18.82%, and 19.99%, respectively. Moreover, propionate accumulation was only detected at the end of thermophilic AD with PVC MPs. Microbial community analysis indicated that PVC MPs in mesophilic AD enriched hydrolytic and acidifying bacteria (Candidatus Competibacter, Lentimicrobium, Romboutsia, etc.) together with acetoclastic methanogens (Methanosarcina, Methanosaeta). By contrast, most carbohydrate-hydrolyzing bacteria, propionate-oxidizing bacterium (Pelotomaculum), and Methanosarcina were inhibited by PVC MPs in thermophilic AD. Network analysis further suggested that PVC MPs significantly changed the relationship of key microorganisms in the AD process. A stronger correlation among the above genera occurred in mesophilic AD, which may promote the methanogenic performance. These results suggested that PVC MPs affected mesophilic and thermophilic AD of WAS via changing microbial activities and interaction.

为丰富微塑料与有机污染物间的相互作用机制相关数据,以3-羟基菲(3-OHP, C14H10O)为菲单羟基衍生物代表污染物,聚氯乙烯(PVC)微塑料为研究对象,研究了PVC微塑料在水环境中对3-OHP的吸附行为,并就相关吸附机制进行了深入探讨。该研究借助扫描电镜(SEM)、X射线衍射仪(XRD)、傅里叶红外光谱(FT-IR)等仪器对PVC微塑料进行表征,利用紫外分光光度计得出目标污染物的紫外吸收光谱标准曲线,标准曲线拟合相关系数(R2)>0.99。为保证紫外吸收光谱的准确性,污染物浓度梯度设置为吸光度(Abs)大于0.438,之后根据标准曲线方程计算其浓度,结合相关吸附模型(吸附动力学、吸附等温线和吸附热力学)并配合密度泛函理论(density functional theory, DFT)探讨了在水环境中PVC微塑料对3-OHP的吸附机制。结果如下:(1)吸附动力学实验结果显示伪二级动力学模型拟合程度最好,吸附动力学拟合系数R2=0.998。因此,PVC吸附3-OHP可能是以表面吸附和外液膜扩散的吸附方式,吸附发生24 h后的平衡吸附量为36.866 μg/g; (2)吸附等温线实验表明Langmuir和Freundlich等温线模型拟合度较高,吸附等温线拟合系数R 2分别为0.956和0.907,更加适合描述PVC对3-OHP的吸附过程,吸附模式主要为单层吸附,也存在小部分多层吸附,PVC对3-OHP的最大吸附量为408 μg/g; (3)吸附热力学结果显示PVC微塑料对3-OHP的吸附效率随着温度升高而降低,这表明PVC对3-OHP的吸附为自发、放热的吸附反应;(4)盐度实验结果表明,盐度对3-OHP在PVC上的吸附效率影响不大;(5)DFT理论计算结果表明PVC对3-OHP结合能相对较低,因此推测PVC对3-OHP的主要吸附机制可能是疏水作用,还可能存在弱氢键作用、卤素键作用以及π-π共轭作用。研究揭示了PVC微塑料与有机物相互作用方式,明确了PVC微塑料对3-OHP的吸附模式,探讨了PVC微塑料对3-OHP的相互作用机制,有助于更好地了解PVC微塑料在水溶液中的环境行为。该研究为科学评价微塑料的环境影响提供数据参考,并进一步补充了微塑料的毒理学机制数据。

Waste plastic conversion involves the treatment of plastic waste to transform in different forms of energy (heat, electricity, liquid fuels). Plastic can be converted into different forms of biofuel via thermochemical conversion methods (gasification, pyrolysis and liquefaction). Algal biomass can be converted into different forms of biofuel (crude bio-oil, bioethanol, biogas, biodiesel and bio-hydrogen) well as value added chemicals. Microalgal cells can accumulate more lipids over a shorter life cycle, they are discussed as a promising feedstock for third-generation biodiesel. The utilization of microalgae as biofuel feedstocks offers an economic, ecofriendly alternative to the use of fossil fuels the aim of microplastics (MPs) removals. Interactions between MPs and microalgal cells could enhance several important features for possible microalgal harvest and MPs accumulation. One hypothesis is microalgal biomass hypothesis can accumulate lipids and carbohydrates under microplastic stress, supporting biomass conversion into biodiesel and bioethanol. In such systems, algal cells act as bio-scavengers for MPs, binding the particles to algal surfaces or incorporating them into their cells; they are filtered from the water body and finally destroyed by further downstream processing of the polluted biomass. In this study, in order to determine biofuel (1-butanol) and methane gas [CH4(g)] production; High- and low-density polyethylene (HDPE and LDPE), polypropylene (PP), and polyvinyl chloride (PVC) MPs were removed using biomass composed of microalgae Chlamydomonas reinhardtii and Chlorella vulgaris. The algal inhibition test results proved that small groups of MPs with a size of ≈ 100 nm did not show algal inhibition. According to the algae inhibition test results, the production of 1-butanol from 100 mg/l microalgae biomass under aerobic conditions were determined as 93 ml/g for HDPE, 236 ml/g for LDPE, 387 ml/g for PP and 459 ml/g for PVC. According to the algae inhibition test results, the production of CH4(g) from 400 mg/l microalgae biomass under anaerobic conditions were measured as 452 ml/g for HDPE, 510 ml/g for LDPE, 529 ml/g for PP and 541 ml/g for PVC. 91.26%, 94.52%, 98.34% and 96.17% energy recoveries were measured for HDPE, LDPE, PP and PVC MPs, respectively, after microalgae biomass experiments, at pH=7.0 and at 35oC. Maximum 98.34% energy recovery was obtained for PP MPs after microalgae biomass experiments, at pH=7.0 and at 35oC.

Microplastics drive microbial assembly, their interactions, and metagenomic functions in two soils with distinct pH and heavy metal availability

Influence of biodegradable polybutylene succinate and non-biodegradable polyvinyl chloride microplastics on anammox sludge: Performance evaluation, suppression effect and metagenomic analysis

Microplastics (MPs) and the typical hydrophilic organic pollutant Malachite green (MG) are frequently detected in sewage treatment plants. Potassium permanganate (KMnO4) pre-oxidation is an economical and effective technology in wastewater treatment. It is important to study the surface physicochemical characteristics of MPs and understand their fate in wastewater treatment plants after pre-oxidation. In this study, Polyvinyl chloride (PVC) MPs were treated by single and composite KMnO4 pre-oxidation with different pH values. After the pre-oxidation treatment, the appearance of OMn spectra and surface nanoparticles indicated the oxides (MnO2) were produced on the MPs surface. Moreover, the adhesion of MnO2 is helpful to improve the hydrophilicity and adsorption capacity of MG. The adsorption capacity of pristine PVC for MG was 2.6 mg/g. But the adsorption capacity increased to 7.0 mg/g for single oxidation and 140.7 mg/g for composite oxidation, respectively. The desorption experiment results indicate the pre-oxidation process could reduce the release efficiency of MG from the PVC MPs due to the better binding of surface MnO2 nanoparticles to MG. However, the total desorption capacity is still high. which illustrates that there is a high potential risk of MG which can transfer from the surface of the PVC MPs to the gastrointestinal fluids.

Disentangling the influence of microplastics and their chemical additives on a model detritivore system

Polyvinyl chloride (PVC) plastic fragments release Pb additives that are bioavailable in zebrafish

Exploring the adsorption behavior of benzotriazoles and benzothiazoles on polyvinyl chloride microplastics in the water environment

Ammonia oxidation by microorganisms is a critical process in the nitrogen cycle. In this study, four soil samples collected from a desert zone in an iron-exploration area and others from farmland and planted forest soil in an iron mine surrounding area. We analyzed the abundance and diversity of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in iron-mining area near the Miyun reservoir using ammonia monooxygenase. A subunit gene (amoA) as molecular biomarker. Quantitative polymerase chain reaction was applied to explore the relationships between the abundance of AOA and AOB and soil physicochemical parameters. The results showed that AOA were more abundant than AOB and may play a more dominant role in the ammonia-oxidizing process in the whole region. PCR-denaturing gradient gel electrophoresis was used to analyze the structural changes of AOA and AOB. The results showed that AOB were much more diverse than AOA. Nitrosospira cluster three constitute the majority of AOB, and AOA were dominated by group 1.1b in the soil. Redundancy analysis was performed to explore the physicochemical parameters potentially important to AOA and AOB. Soil characteristics (i.e. water, ammonia, organic carbon, total nitrogen, available phosphorus, and soil type) were proposed to potentially contribute to the distributions of AOB, whereas Cd was also closely correlated to the distributions of AOB. The community of AOA correlated with ammonium and water contents. These results highlight the importance of multiple drivers in microbial niche formation as well as their affect on ammonia oxidizer composition, both which have significant consequences for ecosystem nitrogen functioning.

Simulation of the effects of microplastics on the microbial community structure and nitrogen cycle of paddy soil

The co-existence of microplastics (MPs) and methamphetamine (METH) in aquatic ecosystems has been widely reported; however, the joint toxicity and associated mechanisms remain unclear. Here, zebrafish larvae were exposed individually or jointly to polystyrene (PS) and polyvinyl chloride (PVC) MPs (20 mg/L) and METH (1 and 5 mg/L) for 10 days. The mortality, behavioral functions, and histopathology of fish from different groups were determined. PS MPs posed a stronger lethal risk to fish than PVC MPs, while the addition of METH at 5 mg/L significantly increased mortality. Obvious deposition of MPs was observed in the larvae's intestinal tract in the exposure groups. Meanwhile, treatment with MPs induced intestinal deposits and intestinal hydrops in the fish, and this effect was enhanced with the addition of METH. Furthermore, MPs significantly suppressed the locomotor activation of zebrafish larvae, showing extended immobility duration and lower velocity. METH stimulated the outcome of PS but had no effect on the fish exposed to PVC. However, combined exposure to MPs and METH significantly increased the turn angle, which declined in individual MP exposure groups. RNA sequencing and gene quantitative analysis demonstrated that exposure to PS MPs and METH activated the MAPK signaling pathway and the C-type lectin signaling pathway of fish, while joint exposure to PVC MPs and METH stimulated steroid hormone synthesis pathways and the C-type lectin signaling pathway in zebrafish, contributing to cellular apoptosis and immune responses. This study contributes to the understanding of the joint toxicity of microplastics and pharmaceuticals to zebrafish, highlighting the significance of mitigating microplastic pollution to preserve the health of aquatic organisms and human beings.

Biodegradation is the most environmentally friendly and, at the same time, economically acceptable approach to removing various pollutants from the environment. However, its efficiency in removing microplastics (MPs) from the environment is generally low. The successful biodegradation of MPs requires microorganisms capable of producing enzymes that degrade MP polymers into compounds that the microorganisms can use as a source of carbon and energy. Therefore, scientists are screening and characterizing microorganisms that can degrade MPs more efficiently. These microorganisms are often isolated from sites contaminated with MPs because the microorganisms living there are adapted to these pollutants and should be able to better degrade MPs. In this study, five bacterial strains and five yeast strains were isolated from various environmental samples including activated sludge, compost, river sediment, and biowaste. Among them, screening was performed for bacteria and yeasts with the highest potential for the biodegradation of polystyrene (PS) and polyvinyl chloride (PVC) MPs, and the bacterium Delftia acidovorans and the yeast Candida parapsilosis were identified as the best candidates. Optimization of biodegradation of the selected MPs by each of these two microorganisms was performed, focusing on the influence of cell density, agitation speed and pH of the medium. It was found that within the selected experimental ranges, high values of cell density, low agitation speed, and a slightly basic medium favored the biodegradation of PS and PVC MPs by Delftia acidovorans. In the case of Candida parapsilosis, favorable conditions also included high cell density followed by a slightly higher, but not maximum, agitation speed and a weakly acidic medium. Broad spectroscopic and imaging methods indicated that Delftia acidovorans and Candida parapsilosis better adapt to PVC MPs to use it as a carbon and energy source.