Chang-Ping Yu

Biodegradation potential of wastewater micropollutants by ammonia-oxidizing bacteria

This study examined the biodegradation potential of three wastewater micropollutants (triclosan, bisphenol A, and ibuprofen) by Nitrosomonas europaea and mixed ammonia-oxidizing bacteria in nitrifying activated sludge. N. europaea could degrade triclosan and bisphenol A, but not ibuprofen. The degradation was observed only in the absence of allylthiourea (an inhibitor for ammonia monooxygenase (AMO)), suggesting that AMO might be responsible for triclosan and bisphenol A degradation. Competitive inhibition among ammonia, triclosan, and bisphenol A was observed. Inactivation of N. europaea was observed after degrading a mixture of triclosan and bisphenol A. The inactivation might be due to product toxicity and/or antimicrobial effect of triclosan; however, the causes of the inactivation were not determined. Regardless of the presence of the AMO inhibitor, three micropollutants were degraded by two different nitrified activated sludge samples. The results suggested that both ammonia-oxidizing bacteria and heterotrophic microorganisms in the activated sludge can degrade triclosan and bisphenol A. On the other hand, ibuprofen was more likely degraded by heterotrophic microorganisms in the activated sludge.

Seasonal variation in the occurrence and removal of pharmaceuticals and personal care products in a wastewater treatment plant in Xiamen, China

The occurrence and seasonal variation of 50 pharmaceuticals and personal care products (PPCPs) in a wastewater treatment plant (WWTP) in Xiamen, China was investigated over a period of one year. Among the targets, 39 PPCPs were detected in the influent. The highest concentration was observed for acetaminophen, with the average concentration in the influent of 2963.5ng/L. The seasonal variation of PPCPs in the influent was observed. For most pharmaceuticals, highest concentrations were in March 2013, followed by December 2012, while the concentrations were lower in August 2012 and May 2013. Among the detected PPCPs, 14 targets could be removed more than 50% in the WWTP. The activated sludge treatment process contributed to most of PPCP removal, while the adsorption to the particles in the primary treatment and the transformation under UV radiation in the disinfection treatment also contributed to the PPCP removal. Among the detected PPCPs in the influent, 36 PPCPs could be detected in the final effluent of the WWTP. Significantly higher concentrations of PPCPs were observed in effluent samples collected in March 2013 compared to other seasons, suggesting higher concentrations of PPCPs could be discharged into the surrounding seawater during this period.

Interaction of silver nanoparticles with pure nitrifying bacteria

In this study, Nitrosomonas europaea ATCC 19718 was exposed to silver nanoparticles (AgNPs) of different particle size (7±3 and 40±14nm) and different coatings (polyvinyl alcohol and adenosine triphosphate disodium). For all different AgNPs used in the study, large aggregates were gradually formed after addition of AgNPs into the media containing N. europaea. The scanning electron microscopy and energy dispersive X-ray spectroscopy of the microstructures suggested that bacterial cells and electrolytes had significant effects on AgNP aggregation. Size- and coating-dependent inhibition of ammonia oxidation by AgNPs was observed, and our analysis suggested that the inhibition was not only due to the released dissolved silver, but also the dispersity of AgNPs in the culture media. Electron microscopy images showed AgNPs could cause the damage of cell wall of N. europaea and make the nucleoids disintegrated and condensed next to cell membrane. Surface-enhanced Raman scattering signals also implied the damage of cell membrane caused by AgNPs. Further protein expression analysis revealed that AgNPs would inhibit important protein functions, including biosynthesis, gene expression, energy production and nitrification to further cause toxicity to N. europaea. Our findings explain the susceptibility of N. europaea to inhibition by AgNPs and the possible interaction between each other. Future research is needed to characterize these effects in more complex cultures and media such as activated sludge and wastewater.

In Situ Study of the Antibacterial Activity and Mechanism of Action of Silver Nanoparticles by Surface-Enhanced Raman Spectroscopy

Silver nanoparticles (Ag NPs) are extensively used as an antibacterial additive in commercial products and their release has caused environmental risk. However, conventional methods for the toxicity detection of Ag NPs are very time consuming and the mechanisms of action are not clear. We developed a new, in situ, rapid, and sensitive fingerprinting approach, using surface-enhanced Raman spectroscopy (SERS), to study the antibacterial activity and mechanism of Ag NPs of 80 and 18 nm (Ag80 and Ag18, respectively), by using the strong electromagnetic enhancement generated by Ag NPs. Sensitive spectra changes representing various biomolecules in bacteria were observed with increasing concentrations of Ag NPs. They not only allowed SERS to monitor the antibacterial activity of Ag NPs of different sizes in different water media but also to study the antibacterial mechanism at the molecular level. Ag18 were found to be more toxic than Ag80 in water, but their toxicity declined to a similar level in the PBS medium. The antibacterial mechanism was proposed on the basis of a careful identification of the chemical origins by comparing the SERS spectra with model compounds. The dramatic change in protein, hypoxanthine, adenosine, and guanosine bands suggested that Ag NPs have a significant impact on the protein and metabolic processes of purine. Finally, by adding nontoxic and SERS active Au NPs, SERS was successfully utilized to study the action mode of the NPs unable to produce an observable SERS signal. This work opens a window for the future extensive SERS studies of the antibacterial mechanism of a great variety of non-SERS-active NPs.

Seasonal and spatial variations of PPCP occurrence, removal and mass loading in three wastewater treatment plants located in different urbanization areas in Xiamen, China

The occurrence and fate of 48 pharmaceuticals and personal care products (PPCPs) in three wastewater treatment plants (WWTPs) located in different urbanization areas in Xiamen, China was investigated over one year. Results showed that PPCPs were widely detected, but the major PPCPs in the influent, effluent, and sludge were different. Spatial and seasonal variations of PPCP levels in the influent and sludge were observed. The removal efficiencies for most PPCPs were similar among the three WWTPs, although they employed different biological treatment processes. Furthermore, the mass loadings per inhabitant of most pharmaceuticals had a positive correlation with the urbanization levels, indicating that most pharmaceutical usage was higher in the urban core compared to the suburban zones. The total mass loadings of all the 48 PPCPs in the effluent and waste sludge showed close proportions, which suggested the importance of proper waste sludge disposal to prevent a large quantity of PPCPs from entering the environment.

Microbial degradation of steroidal estrogens

Steroidal estrogens, widespread in the environment, are contaminants of potential concern because exposure to these compounds can cause adverse impacts on aquatic life. Intensive research efforts have been undertaken in order to better understand the environmental occurrence of these compounds. In addition to physical/chemical reactions, biological processes - microbial biodegradation of steroidal estrogens - play a vital role in determining the fate and transport of these compounds in built and natural environments. This review summarizes the current state of knowledge on the microbiology of estrogen biodegradation. Aerobic and anaerobic estrogen-degrading microorganisms are phylogenetically diverse; they are mainly isolated from soils, activated sludge, dental plaque and intestines. Estrogens can be degraded via growth-linked and non-growth-linked reactions, as well as through abiotic degradation in the presence of selective microorganisms. Current knowledge on estrogen biodegradation kinetics and pathways is limited. Molecular methods are useful in deciphering estrogen-degrading microbial community and tracking the quantity of known degraders in bioreactors with different operating conditions. Future research efforts aimed at bridging knowledge gaps on estrogen biodegradation are also proposed.

Pharmaceuticals and personal care products in a mesoscale subtropical watershed and their application as sewage markers

This study comprehensively analyzed 23 classes of 51 pharmaceuticals and personal care products (PPCPs) in the two major prongs of Jiulong River and its estuary in southeast China, where the levels of the targeted PPCPs were mostly unknown. For both Jiulong River and its estuary, nine PPCPs were detected with 100% detection frequencies including two anti-inflammatory and analgesic drugs (ketoprofen and diclofenac acid), a stimulant (caffeine), a plasticizer (bisphenol A), two preservatives (methyl paraben and propyl paraben), two antimicrobials (triclosan and triclocarban) and a β-blocks (metoprolol), among which bisphenol A and caffeine accounted for more than 60% in concentrations. PPCPs generally had higher concentrations in dry season than normal season and wet season, while certain PPCPs, such as UV filters, showed higher concentrations in wet season, which were presumed to be related to their usage patterns. The concentrations of PPCPs were significantly correlated to several quality parameters of the surface water. The selected sewage markers were also used to track sewage in the studied river and the ratios of easily removed markers and conservative markers were used to identify the contribution of raw or treated sewage input. From our result, Jiulong River and its estuary were likely polluted by potential discharge of raw sewage.

Influence of pretreated activated sludge for electricity generation in microbial fuel cell application.

Influence of different pretreated sludge for electricity generation in microbial fuel cells (MFCs) was investigated in this study. Pre-treatment has shown significant improvement in MFC electricity productivity especially from microwave treated sludge. Higher COD reduction in the MFC has been revealed from microwave treated sludge with 55% for total and 85% for soluble COD, respectively. Nonetheless, longer ozonation treatment did not give additional advantage compared to the raw sludge. On the other hand, samples from anodes were analyzed using the 16S rRNA gene-based pyrosequencing technique for microbial community analysis. There was substantial difference in community compositions among MFCs fed with different pretreated sludge. Bacteroidetes was the abundant bacterial phylum dominated in anodes of higher productivity MFCs. These results demonstrate that using waste sludge as the substrate in MFCs could achieve both sludge reduction and electricity generation, and proper pre-treatment of sludge could improve the overall process performance.

Removal of silver nanoparticles by coagulation processes

Commercial use of silver nanoparticles (AgNPs) will lead to a potential route for human exposure via potable water. Coagulation followed by sedimentation, as a conventional technique in the drinking water treatment facilities, may become an important barrier to prevent human from AgNP exposures. This study investigated the removal of AgNP suspensions by four regular coagulants. In the aluminum sulfate and ferric chloride coagulation systems, the water parameters slightly affected the AgNP removal. However, in the poly aluminum chloride and polyferric sulfate coagulation systems, the optimal removal efficiencies were achieved at pH 7.5, while higher or lower of pH could reduce the AgNP removal. Besides, the increasing natural organic matter (NOM) would reduce the AgNP removal, while Ca(2+) and suspended solids concentrations would also affect the AgNP removal. In addition, results from the transmission electron microscopy and X-ray diffraction showed AgNPs or silver-containing nanoparticles were adsorbed onto the flocs. Finally, natural water samples were used to validate AgNP removal by coagulation. This study suggests that in the case of release of AgNPs into the source water, the traditional water treatment process, coagulation/sedimentation, can remove AgNPs and minimize the silver ion concentration under the well-optimized conditions.

Transformation of Bisphenol A and Alkylphenols by Ammonia-Oxidizing Bacteria through Nitration

Transformation of bisphenol A (BPA) by ammonia-oxidizing bacteria (AOB) Nitrosomonas europaea ATCC 19718 was investigated. On the basis of the ultraperformance liquid chromatography (UPLC) coupled to quadrupole time-of-flight mass spectrometry (Q-TOF MS) and nuclear magnetic resonance analysis, we found N. europaea could transform BPA into nitro- and dinitro-BPA, suggesting that abiotic nitration between the biogenic nitrite and BPA played a major role in the transformation of BPA in the batch AOB system. Nitrite concentrations, temperature, and pH values were the major factors to influence the reaction rate. Furthermore, the yeast estrogenic screening assay showed that the formed nitro- and dinitro-BPA had much less estrogenic activity as compared with its parent compound BPA. Similar reactions of abiotic nitration were considered for 4-n-nonylphenol (nNP) and 4-n-octylphenol (nOP) since nitro-nNP and nitro-nOP were detected by UPLC-Q-TOF MS. In addition, results from the local wastewater treatment plant (WWTP) showed the occurrence of nitro-BPA and dinitro-BPA during the biological treatment process and in the effluent, indicating that nitration of BPA is also a pathway for removal of BPA. Results of this study provided implication that AOB in the WWTPs might contribute to removal of selected endocrine-disrupting compounds (EDCs) through abiotic nitritation.