Publications by authors named "Zhiguo Yuan"

376 Publications

Roles of Oxygen in Methane-dependent Selenate Reduction in a Membrane Biofilm Reactor: Stimulation or Suppression.

Water Res 2021 Apr 14;198:117150. Epub 2021 Apr 14.

Advanced Water Management Centre, The University of Queensland, St Lucia, Brisbane, Queensland 4072, Australia. Electronic address:

Although methane (CH) has been proven to be able to serve as an electron donor for bio-reducing various oxidized contaminants (e.g., selenate (SeO)), little is known regarding the roles of oxygen in methane-based reduction processes. Here, a methane-based membrane biofilm reactor (MBfR) was established for evaluating the effects of oxygen supply rates on selenate reduction performance and microbial communities. The oxygen supply rate played a dual role (stimulatory or suppressive effect) in selenate reduction rates, depending on the presence or absence of dissolved oxygen (DO). Specifically, selenate reduction rate was substantially enhanced when an appropriate oxygen rate (e.g., 12 to 184 mg/Ld in this study) was supplied but with negligible DO. The highest selenate reduction rate (up to 34 mg-Se/Ld) was obtained under an oxygen supply rate of 184 mg/Ld. In contrast, excessive oxygen supply rate (626 mg/Ld) would significantly suppress selenate reduction rate under DO level of 3 mg/L. Accordingly, though the high oxygen supply rate (626 mg/Ld) would promote the expression of pmoA (5.9 × 10 copies g), the expression level of narG (a recognized gene to mediate selenate reduction) would be significantly downregulated (6.1 × 10 copies g), thus suppressing selenate reduction. In contrast, the expression of narG gene significantly increased to 2.8 × 10 copies g, and the expression of pmoA gene could still maintain at 1.1 × 10 copies g under an oxygen supply rate of 184 mg/Ld. High-throughput sequencing targeting 16S rRNA gene, pmoA, and narG collectively suggested Methylocystis acts as the major aerobic methanotroph, in synergy with Arthrobacter and Variovorax which likely jointly reduce selenate to selenite (SeO), and further to elemental selenium (Se). Methylocystis was predominant in the biofilm regardless of variations of oxygen supply rates, while Arthrobacter and Variovorax were sensitive to oxygen fluctuation. These findings provide insights into the effects of oxygen on methane-dependent selenate reduction and suggest that it is feasible to achieve a higher selenate removal by regulating oxygen supply rates.
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http://dx.doi.org/10.1016/j.watres.2021.117150DOI Listing
April 2021

Development of radio-frequency identification (RFID) sensors suitable for smart-monitoring applications in sewer systems.

Water Res 2021 Apr 5;198:117107. Epub 2021 Apr 5.

Department of Civil and Environmental Engineering, Faculty of Engineering, The University of Auckland, Symonds St, Auckland, 1010, New Zealand. Electronic address:

Sanitary and stormwater sewers are buried assets that play important roles in the prevention of diseases and the reduction of health risks for our societies. Due to their hidden nature, these assets are not frequently assessed and maintained to optimal conditions. The lack of maintenance can cause sewer blockages and overflows that result in the release of pathogens into the environment. For cities, monitoring sewer conditions on a large-scale can be costly, time-consuming, and labor-intensive if using current low-throughput technologies, such as dye testing or closed-circuit television. Alternatively, smart sensor systems can provide low-cost, high-throughput, and automatic data-driven features for real-time monitoring applications. In this study, we developed ultrahigh-frequency radio-frequency identification (UHF RFID)-based sensors that are flushable and suitable for sanitary and stormwater pipes quick surveys. 3D printed RFID sensors were designed to float at the water-air interface and minimize the water interference to RF signal communications. The optimal detection range was also determined to support the design and installation of the reader in various utility holes. Field trials demonstrated that the UHF RFID system is a low-cost, high-throughput, and robust solution for monitoring blockage, illicit-connection, and water flow in sewer networks.
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http://dx.doi.org/10.1016/j.watres.2021.117107DOI Listing
April 2021

3D-printed cell-free PCL-MECM scaffold with biomimetic micro-structure and micro-environment to enhance in situ meniscus regeneration.

Bioact Mater 2021 Oct 27;6(10):3620-3633. Epub 2021 Mar 27.

Institute of Orthopedics, The First Medical Center, Chinese PLA General Hospital; Beijing Key Lab of Regenerative Medicine in Orthopedics, Key Laboratory of Musculoskeletal Trauma & War Injuries PLA. No.28 Fuxing Road, Haidian District, Beijing 100853, People's Republic of China.

Despite intensive effort was made to regenerate injured meniscus by cell-free strategies through recruiting endogenous stem/progenitor cells, meniscus regeneration remains a great challenge in clinic. In this study, we found decellularized meniscal extracellular matrix (MECM) preserved native meniscal collagen and glycosaminoglycans which could be a good endogenous regeneration guider for stem cells. Moreover, MECM significantly promoted meniscal fibrochondrocytes viability and proliferation, increased the expression of type II collagen and proteoglycans in vitro. Meanwhile, we designed 3D-printed polycaprolactone (PCL) scaffolds which mimic the circumferential and radial collagen orientation in native meniscus. Taken these two advantages together, a micro-structure and micro-environment dually biomimetic cell-free scaffold was manipulated. This cell-free PCL-MECM scaffold displayed superior biocompatibility and yielded favorable biomechanical capacities closely to native meniscus. Strikingly, neo-menisci were regenerated within PCL-MECM scaffolds which were transplanted into knee joints underwent medial meniscectomy in rabbits and sheep models. Histological staining confirmed neo-menisci showed meniscus-like heterogeneous staining. Mankin scores showed PCL-MECM scaffold could protect articular cartilage well, and knee X-ray examination revealed same results. Knee magnetic resonance imaging (MRI) scanning also showed some neo-menisci in PCL-MECM scaffold group. In conclusion, PCL-MECM scaffold appears to optimize meniscus regeneration. This could represent a promising approach worthy of further investigation in preclinical applications.
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http://dx.doi.org/10.1016/j.bioactmat.2021.02.019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8039774PMC
October 2021

Hydrogen-driven microbial biogas upgrading: Advances, challenges and solutions.

Water Res 2021 Jun 5;197:117120. Epub 2021 Apr 5.

Advanced Water Management Centre, The University of Queensland, St Lucia, Brisbane, QLD 4072, Australia. Electronic address:

As a clean and renewable energy, biogas is an important alternative to fossil fuels. However, the high carbon dioxide (CO) content in biogas limits its value as a fuel. 'Biogas upgrading' is an advanced process which removes CO from biogas, thereby converting biogas to biomethane, which has a higher commercial value. Microbial technologies offer a sustainable and cost-effective way to upgrade biogas, removing CO using hydrogen (H) as electron donor, generated by surplus electricity from renewable wind or solar energy. Hydrogenotrophic methanogens can be applied to convert CO with H to methane (CH), or alternatively, homoacetogens can convert both CO and H into value-added chemicals. Here, we comprehensively review the current state of biogas generation and utilization, and describe the advances in biological, H-dependent biogas upgrading technologies, with particular attention to key challenges associated with the processes, e.g., metabolic limitations, low H transfer rate, and finite CO conversion rate. We also highlight several new strategies for overcoming technical barriers to achieve efficient CO conversion, including process optimization to eliminate metabolic limitation, novel reactor designs to improve H transfer rate and utilization efficiency, and employing advanced genetic engineering tools to generate more efficient microorganisms. The insights offered in this review will promote further exploration into microbial, H-driven biogas upgrading, towards addressing the global energy crisis and climate change associated with use of fossil fuels.
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http://dx.doi.org/10.1016/j.watres.2021.117120DOI Listing
June 2021

Biofunctionalized Structure and Ingredient Mimicking Scaffolds Achieving Recruitment and Chondrogenesis for Staged Cartilage Regeneration.

Front Cell Dev Biol 2021 25;9:655440. Epub 2021 Mar 25.

Institute of Orthopedics, The First Medical Center, Chinese PLA General Hospital, Beijing Key Lab of Regenerative Medicine in Orthopedics, Key Laboratory of Musculoskeletal Trauma & War Injuries PLA, Beijing, China.

It remains scientifically challenging to regenerate injured cartilage in orthopedics. Recently, an endogenous cell recruitment strategy based on a combination of acellular scaffolds and chemoattractants to specifically and effectively recruit host cells and promote chondrogenic differentiation has brought new hope for articular cartilage regeneration. In this study, a transforming growth factor-β3 (TGF-β3)-loaded biomimetic natural scaffold based on demineralized cancellous bone (DCB) and acellular cartilage extracellular matrix (ECM) was developed and found to improve chondral repair by enhancing cell migration and chondrogenesis. The DCB/ECM scaffold has porous microstructures (pore size: 67.76 ± 8.95 μm; porosity: 71.04 ± 1.62%), allowing the prolonged release of TGF-β3 (up to 50% after 42 days ) and infrapatellar fat pad adipose-derived stem cells (IPFSCs) that maintain high cell viability (>96%) and favorable cell distribution and phenotype after seeding onto the DCB/ECM scaffold. The DCB/ECM scaffold itself can also provide a sustained release system to effectively promote IPFSC migration (nearly twofold ). Moreover, TGF-β3 loaded on scaffolds showed enhanced chondrogenic differentiation (such as collagen II, ACAN, and SOX9) of IPFSCs after 3 weeks of culture. After implanting the composite scaffold into the knee joints of rabbits, enhanced chondrogenic differentiation was discovered at 1, 2, and 4 weeks post-surgery, and improved repair of cartilage defects in terms of biochemical, biomechanical, radiological, and histological results was identified at 3 and 6 months post-implantation. To conclude, our study demonstrates that the growth factor (GF)-loaded scaffold can facilitate cell homing, migration, and chondrogenic differentiation and promote the reconstructive effects of cartilage formation, revealing that this staged regeneration strategy combined with endogenous cell recruitment and pro-chondrogenesis is promising for articular cartilage regeneration.
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http://dx.doi.org/10.3389/fcell.2021.655440DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8027342PMC
March 2021

Simultaneous removal of antibiotic resistant bacteria, antibiotic resistance genes, and micropollutants by a modified photo-Fenton process.

Water Res 2021 Jun 20;197:117075. Epub 2021 Mar 20.

Advanced Water Management Centre (AWMC), The University of Queensland, St Lucia, Brisbane, QLD, 4072, Australia. Electronic address:

Although photo-driven advanced oxidation processes (AOPs) have been developed to treat wastewater, few studies have investigated the feasibility of AOPs to simultaneously remove antibiotic resistant bacteria (ARB), antibiotic resistance genes (ARGs) and micropollutants (MPs). This study employed a modified photo-Fenton process using ethylenediamine-N,N'-disuccinic acid (EDDS) to chelate iron(III), thus maintaining the reaction pH in a neutral range. Simultaneous removal of ARB and associated extracellular (e-ARGs) and intracellular ARGs (i-ARGs), was assessed by bacterial cell culture, qPCR and atomic force microscopy. The removal of five MPs was also evaluated by liquid chromatography coupled with mass spectrometry. A low dose comprising 0.1 mM Fe(III), 0.2 mM EDDS, and 0.3 mM hydrogen peroxide (HO) was found to be effective for decreasing ARB by 6-log within 30 min, and e-ARGs by 6-log within 10 min. No ARB regrowth occurred after 48-h, suggesting that the proposed process is an effective disinfectant against ARB. Moreover, five recalcitrant MPs (carbamazepine, diclofenac, sulfamethoxazole, mecoprop and benzotriazole at an initial concentration of 10 μg/L each) were >99% removed after 30 min treatment in ultrapure water. The modified photo-Fenton process was also validated using synthetic wastewater and real secondary wastewater effluent as matrices, and results suggest the dosage should be doubled to ensure equivalent removal performance. Collectively, this study demonstrated that the modified process is an optimistic 'one-stop' solution to simultaneously mitigate both chemical and biological hazards.
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http://dx.doi.org/10.1016/j.watres.2021.117075DOI Listing
June 2021

Feasibility of methane bioconversion to methanol by acid-tolerant ammonia-oxidizing bacteria.

Water Res 2021 Jun 21;197:117077. Epub 2021 Mar 21.

Advanced Water Management Centre, The University of Queensland, St Lucia, QLD, 4072, Australia. Electronic address:

Bioconversion of biogas to value-added liquids has received increasing attention over the years. However, many biological processes are restricted under acidic conditions owing to the excessive carbon dioxide (CO, 30-40% v/v) in biogas. Here, using an enriched culture dominated by acid-tolerant ammonia-oxidizing bacteria (AOB) 'Candidatus Nitrosoglobus', this study examined the feasibility of producing methanol from methane in the CO-acidified environment (i.e. pH of 5.0). Within the tested dissolved methane range (0.1-0.9 mM), methane oxidation by the acid-tolerant AOB culture followed first-order kinetics, with the same rate constant (i.e. 0.43 (L/(g VSS‧h)) between pH 7.0 and 5.0. The acidic methane oxidation showed robustness against high dissolved concentrations of CO (up to 4.06 mM) and hydrogen sulfide (HS up to 0.11 mM), which led to a high methanol yield of about 30-40%. As such, the raw biogas containing toxic CO and HS can directly serve for methanol production by this acid-tolerant AOB culture, economizing a conventionally costly biogas upgradation process. Afterwards, two batch reactors fed with methane and oxygen intermittently both obtained a final concentration of 1.5 mM CHOH (equal to 72 mg chemical oxygen demand/L) in the liquid, suggesting it is a useful carbon source to enhance denitrification in wastewater treatment systems. In addition, ammonia availability was identified to be critical for a higher rate of this AOB-mediated methanol production. Overall, our results for the first time demonstrated the capability of a novel acid-tolerant AOB culture to oxidize methane, and also illustrated the technical feasibility to utilize raw biogas for methanol production at acidic conditions.
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http://dx.doi.org/10.1016/j.watres.2021.117077DOI Listing
June 2021

Biotrickling filter for the removal of volatile sulfur compounds from sewers: A review.

Chemosphere 2021 Mar 19;277:130333. Epub 2021 Mar 19.

School of Civil, Mining & Environmental Engineering, University of Wollongong, NSW, Australia. Electronic address:

Volatile sulfur compounds (VSCs) were identified as the dominant priority odorants emitted from sewers, including hydrogen sulfide (HS), methyl mercaptan (MM), dimethyl disulfide (DMDS) and dimethyl sulfide (DMS). Biotrickling filter (BTF) is a widely-applied technology for odour abatement in sewers because of its relatively low operating cost and efficient HS removal. The authors review the mechanisms and performance of BTF for the removal of these four VSCs, and discuss the key influencing factors including of empty bed residence time (EBRT), pH, temperature, nutrients, water content, trickling operation and packing materials. Besides, measures to improve the VSCs removal in BTF are proposed in the context of key influencing factors. Finally, the review assesses the new challenges of BTF for sewer emissions treatment, namely with respect to the performance of BTF for greenhouse gases (GHG) treatment.
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http://dx.doi.org/10.1016/j.chemosphere.2021.130333DOI Listing
March 2021

Stoichiometric and kinetic characterization of an acid-tolerant ammonia oxidizer 'Candidatus Nitrosoglobus'.

Water Res 2021 May 9;196:117026. Epub 2021 Mar 9.

Advanced Water Management Centre, The University of Queensland, St Lucia, QLD 4072, Australia. Electronic address:

Recently, acidic (i.e. pH<5) nitrification in activated-sludge is attracting attention because it enables stable nitritation (NH → NO), and enhances sludge reduction and stabilization. However, the key acid-tolerant ammonia oxidizers involved are poorly understood. In this study, we performed stoichiometric and kinetic characterization of a new acid-tolerant ammonia-oxidizing bacterium (AOB) belonging to gamma-proteobacterium, Candidatus Nitrosoglobus. Ca. Nitrosoglobus was cultivated in activated-sludge in a laboratory membrane bioreactor over 200 days, with a relative abundance of 55.1 ± 0.5% (indicated by 16S rRNA gene amplicon sequencing) at the time of the characterization experiments. Among all known nitrifiers, Ca. Nitrosoglobus bears the highest resistance to nitrite, low pH, and free nitrous acid (FNA). These traits define Ca. Nitrosoglobus as an adversity-strategist that tends to prosper in acidic activated-sludge, where the low pH (< 5.0) and high levels of FNA (at parts per million levels) sustained and inhibited all other nitrifiers. In contrast, in the conventional pH-neutral activated-sludge process, Ca. Nitrosoglobus is less competitive with canonical AOB (e.g. Nitrosomonas) due to the relatively slow specific growth rate and low affinities to both oxygen and total ammonia. These results advance our understanding of acid-tolerant ammonia oxidizers, and support further development of the acidic activated-sludge process in which Ca. Nitrosoglobus can play a critical role.
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http://dx.doi.org/10.1016/j.watres.2021.117026DOI Listing
May 2021

Non-antibiotic pharmaceuticals promote the transmission of multidrug resistance plasmids through intra- and intergenera conjugation.

ISME J 2021 Mar 10. Epub 2021 Mar 10.

Advanced Water Management Centre, The University of Queensland, St. Lucia, Brisbane, QLD, Australia.

Antibiotic resistance is a global threat to public health. The use of antibiotics at sub-inhibitory concentrations has been recognized as an important factor in disseminating antibiotic resistance via horizontal gene transfer. Although non-antibiotic, human-targeted pharmaceuticals are widely used by society (95% of the pharmaceuticals market), the potential contribution to the spread of antibiotic resistance is not clear. Here, we report that commonly consumed, non-antibiotic pharmaceuticals, including nonsteroidal anti-inflammatories (ibuprofen, naproxen, diclofenac), a lipid-lowering drug (gemfibrozil), and a β-blocker (propranolol), at clinically and environmentally relevant concentrations, significantly accelerated the dissemination of antibiotic resistance via plasmid-borne bacterial conjugation. Various indicators were used to study the bacterial response to these drugs, including monitoring reactive oxygen species (ROS) and cell membrane permeability by flow cytometry, cell arrangement, and whole-genome RNA and protein sequencing. Enhanced conjugation correlated well with increased production of ROS and cell membrane permeability. Additionally, these non-antibiotic pharmaceuticals induced responses similar to those detected when bacteria are exposed to antibiotics, such as inducing the SOS response and enhancing efflux pumps. The findings advance understanding of the transfer of antibiotic resistance genes, emphasizing the concern that non-antibiotic, human-targeted pharmaceuticals enhance the spread of antibiotic resistance among bacterial populations.
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http://dx.doi.org/10.1038/s41396-021-00945-7DOI Listing
March 2021

An integrated strategy to enhance performance of anaerobic digestion of waste activated sludge.

Water Res 2021 May 25;195:116977. Epub 2021 Feb 25.

Advanced Water Management Centre, The University of Queensland, St Lucia, QLD 4072, Australia. Electronic address:

Anaerobic digestion (AD) is an essential process in wastewater treatment plants as it can reduce the amount of waste activated sludge (WAS) for disposal, and also enables the recovery of bioenergy (i.e. methane). Here, a new pretreatment method to enhance anaerobic digestion was achieved by treating thickened WAS (TWAS) with ferric (as FeCl) and nitrite simultaneously for 24-hour at room temperature. Biochemical methane potential tests showed markedly improved degradability in the pretreated TWAS, with a relative increase in hydrolysis rate by 30%. A comparative experiment with the operation of two continuous-flow anaerobic digesters further demonstrated the improvement in biogas quantity and quality, digestate disposal, and phosphorus recovery in the experimental digester. The dosed FeCl (i.e. ~6 mM) decreased the pH of TWAS to ~5, which led to the formation of free nitrous acid (FNA, HNO) at parts per million levels (i.e. ~6 mg N/L), after dosing nitrite at 250 mg NO-N/L. This FNA treatment caused a 26% increase in methane yield and volatile solids destruction, 55% reduction in the viscosity of sludge in digester, and 24% less polymer required in further digestate dewatering. In addition, the dosed Fe(III) was reduced to Fe(II) which precipitated sulfide and phosphorus, leading to decreased hydrogen sulfide concentration in biogas, and increased percentage of vivianite in the total crystalline iron species in digested sludge. Our study experimentally demonstrated that combined dosing of FeCl and nitrite is a useful pretreatment strategy for improving anaerobic digestion of WAS.
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http://dx.doi.org/10.1016/j.watres.2021.116977DOI Listing
May 2021

Acidic aerobic digestion of anaerobically-digested sludge enabled by a novel ammonia-oxidizing bacterium.

Water Res 2021 Apr 23;194:116962. Epub 2021 Feb 23.

Advanced Water Management Centre, The University of Queensland, St Lucia, QLD 4072, Australia. Electronic address:

Anaerobic digestion is a commonly used process for the reduction and stabilization of wasted activated sludge generated in wastewater treatment plants. However, anaerobically-digested (AD) sludge is still a problematic waste stream due to its large volume and often poor quality. In this study, two aerobic digesters were set up to treat anaerobically-digested sludge, with one digester operated in self-generated acidic condition as the experimental reactor, and one at neutral pH as the control reactor. The acidic condition in the experimental reactor was driven by an inoculated special ammonia-oxidizing bacterium, 'Candidatus Nitrosoglobus', which can tolerate low pH. As a result of ammonium oxidation by Ca. Nitrosoglobus, the pH decreased to 4.8 ± 0.2 and nitrite accumulated to and stayed at 200.0 ± 17.2 mg N L, from which free nitrous acid (FNA) at 8.5 ± 1.8 mg HNON L formed in-situ. As a combined effect of low pH and high concentration of FNA, the experimental reactor reduced the total solids (TS), volatile solids (VS) and non-volatile solids (NVS) in the AD sludge by 25.2 ± 7.0%, 29.8 ± 4.3%, and 22.6 ± 5.5%, respectively. In contrast, the control reactor without Ca. Nitrosoglobus inoculation (operated at a near-neutral pH of 6.8 ± 0.3 and no FNA formation) only reduced VS in the AD sludge by 10.4 ± 4.3%, along with negligible NVS reduction. Additionally, the acidic aerobic digestion in the experimental reactor significantly stabilized AD sludge, decreasing the specific oxygen uptake rate (SOUR) to 0.5 ± 0.1 mg O gVS h and the most probable number (MPN) of Faecal Coliforms to 2.4 ± 0.1 log(MPN gTS), both of which meet USEPA standards for Class A biosolids. In comparison, the control reactor produced biosolids at Class B level only, with an SOUR of 1.8 ± 0.2 mg O gVS h and a Faecal Coliforms MPN of 3.6 ± 0.1 log(MPN gTS). By reducing the volume and improving the quality of the AD sludge, the acidic aerobic digestion of AD sludge enabled by Ca. Nitrosoglobus has the potential to significantly save the sludge disposal costs in wastewater treatment.
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http://dx.doi.org/10.1016/j.watres.2021.116962DOI Listing
April 2021

Rapid formation of granules coupling n-DAMO and anammox microorganisms to remove nitrogen.

Water Res 2021 Apr 23;194:116963. Epub 2021 Feb 23.

The University of Queensland, Advanced Water Management Centre, St Lucia, QLD 4072, Australia. Electronic address:

Granular sludge exhibits unique features, including rapid settling velocity, high loading rate and relative insensitivity against inhibitors, thus being a favorable platform for the cultivation of slow-growing and vulnerable microorganisms, such as anaerobic ammonium oxidation (anammox) bacteria and nitrite/nitrate-dependent anaerobic methane oxidation (n-DAMO) microorganisms. While anammox granules have been widely applied, little is known about how to speed up the granulation process of n-DAMO microorganisms, which grow even slower than anammox bacteria. In this study, we used mature anammox granules as biotic carriers to embed n-DAMO microorganisms, which obtained combined anammox + n-DAMO granules within 6 months. The results of whole-granule 16S rRNA gene amplicon sequencing showed the coexistence of anammox bacteria, n-DAMO bacteria and n-DAMO archaea. The microbial stratification along granule radius was further elucidated by cryosection-16S rRNA gene amplicon sequencing, showing the dominance of n-DAMO archaea and anammox bacteria at inner and outer layers, respectively. Moreover, the images of cryosection-fluorescence in situ hybridization (FISH) verified this stratification and also indicated a shift in microbial stratification. Specifically, n-DAMO bacteria and n-DAMO archaea attached to the anammox granule surface initially, which moved to the inner layer after 4-months operation. On the basis of combined anammox + n-DAMO granules, a practically useful nitrogen removal rate (1.0 kg N/m/d) was obtained from sidestream wastewater, which provides new avenue to remove nitrogen from wastewater using methane as carbon source.
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http://dx.doi.org/10.1016/j.watres.2021.116963DOI Listing
April 2021

Versatility of nitrite/nitrate-dependent anaerobic methane oxidation (n-DAMO): First demonstration with real wastewater.

Water Res 2021 Apr 8;194:116912. Epub 2021 Feb 8.

Advanced Water Management Centre, The University of Queensland, St. Lucia, Queensland 4072, Australia. Electronic address:

Nitrite/nitrate-dependent anaerobic methane oxidation (n-DAMO) processes have been proven effective for nitrogen removal from synthetic wastewater. However, the demonstration using real wastewater has not been achieved yet. To this end, this study investigated the versatile applications of n-DAMO process in real wastewater treatment for the first time. Two methane-based membrane biofilm reactors (MBfRs) were employed to combine anammox and n-DAMO microorganisms, targeting nitrogen removal in mainstream (i.e., domestic sewage) and sidestream (i.e., anaerobic digestion liquor), respectively. Considering various technologies in sewage treatment, three different technical routes, including nitritation + methane-based MBfR, partial nitritation + methane-based MBfR and partial nitritation + anammox + methane-based MBfR, were investigated comprehensively, all producing effluent quality with total nitrogen (TN) at 5 mg N/L or less. Regarding the sidestream treatment, the methane-based MBfR also removed up to 96% TN from the partially nitrified anaerobic digestion liquor at a practically useful rate of 0.5 kg N/m/d. Microbial communities revealed by 16S rRNA gene amplicon sequencing indicated the dominance of n-DAMO archaea in both reactors, along with the existence of anammox bacteria and n-DAMO bacteria. As the first demonstration of n-DAMO process in real wastewater, this study comprehensively confirmed the applicability of using methane as carbon source to remove nitrogen from both mainstream and sidestream wastewater, supporting their adoption by industries in practice.
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http://dx.doi.org/10.1016/j.watres.2021.116912DOI Listing
April 2021

Simultaneous nitrate and sulfate dependent anaerobic oxidation of methane linking carbon, nitrogen and sulfur cycles.

Water Res 2021 Apr 13;194:116928. Epub 2021 Feb 13.

State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, No.73, Huanghe Road, Nangang District, Harbin, Heilongjiang, 150090, China.

ANaerobic MEthanotrophic (ANME) archaea are critical microorganisms mitigating methane emission from anoxic zones. In previous studies, sulfate-dependent anaerobic oxidation of methane (AOM) and nitrate-dependent AOM, performed by different clades of ANME archaea, were detected in marine sediments and freshwater environments, respectively. This study shows that simultaneous sulfate- and nitrate-dependent AOM can be mediated by a clade of ANME archaea, which may occur in estuaries and coastal zones, at the interface of marine and freshwater environments enriched with sulfate and nitrate. Long-term (~1,200 days) performance data of a bioreactor, metagenomic analysis and batch experiments demonstrated that ANME-2d not only conducted AOM coupled to reduction of nitrate to nitrite, but also coupled to the conversion of sulfate to sulfide, in collaboration with sulfate-reducing bacteria (SRB). Sulfide was oxidized back to sulfate by sulfide-oxidizing autotrophic denitrifiers with nitrate or nitrite as electron acceptors, in turn alleviating sulfide accumulation. In addition, dissimilatory nitrate reduction to ammonium performed by ANME-2d was detected, providing substrates to Anammox. Metatranscriptomic analysis revealed significant upregulation of flaB in ANME-2d and pilA in Desulfococcus, which likely resulted in the formation of unique nanonets connecting cells and expanding within the biofilm, and putatively providing structural links between ANME-2d and SRB for electron transfer. Simultaneous nitrate- and sulfate-dependent AOM as observed in this study could be an important link between the carbon, nitrogen and sulfur cycles in natural environments, such as nearshore environments.
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http://dx.doi.org/10.1016/j.watres.2021.116928DOI Listing
April 2021

Robust Nitritation Sustained by Acid-Tolerant Ammonia-Oxidizing Bacteria.

Environ Sci Technol 2021 02 14;55(3):2048-2056. Epub 2021 Jan 14.

Advanced Water Management Centre, The University of Queensland, St Lucia, Brisbane, QLD 4072, Australia.

Oxidation of ammonium to nitrite rather than nitrate, , nitritation, is critical for autotrophic nitrogen removal. This study demonstrates a robust nitritation process in treating low-strength wastewater, obtained from a mixture of real mainstream sewage with sidestream anaerobic digestion liquor. This is achieved through cultivating acid-tolerant ammonia-oxidizing bacteria (AOB) in a laboratory nitrifying bioreactor at pH 4.5-5.0. It was shown that nitrite accumulation with a high NO/(NO + NO) ratio of 95 ± 5% was stably maintained for more than 300 days, and the obtained volumetric NH removal rate (, 188 ± 14 mg N L d) was practically useful. 16S rRNA gene sequencing analyses indicated the dominance of new AOB, " Nitrosoglobus," in the nitrifying guild (, 1.90 ± 0.08% in the total community), with the disappearance of typical activated sludge nitrifying microorganisms, including , , and . This is the first identification of Nitrosoglobus as key ammonia oxidizers in a wastewater treatment system. It was found that Nitrosoglobus can tolerate low pH (<5.0), and free nitrous acid (FNA) at levels that inhibit AOB and nitrite-oxidizing bacteria (NOB) commonly found in wastewater treatment processes. The inhibition of NOB leads to accumulation of nitrite (NO), which along with protons (H) also produced in ammonium oxidation generates and sustains FNA at 3.0 ± 1.4 mg HNO-N L. As such, robust PN was achieved under acidic conditions, with a complete absence of NOB. Compared to previous nitritation systems, this acidic nitritation process is featured by a higher nitric oxide (NO) but a lower nitrous oxide (NO) emission level, with the emission factors estimated at 1.57 ± 0.08 and 0.57 ± 0.03%, respectively, of influent ammonium nitrogen load.
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http://dx.doi.org/10.1021/acs.est.0c05181DOI Listing
February 2021

A partial hemi-resurfacing preliminary study of a novel magnetic resonance imaging compatible polyetheretherketone mini-prosthesis for focal osteochondral defects.

J Orthop Translat 2021 Jan 20;26:67-73. Epub 2020 Mar 20.

Department of Bone and Joint Surgery, Renji Hospital, School of Medicine, Shanghai Jiaotong University, Shanghai, China.

Background: The use of partial articular resurfacing surgery with a mini-implant has been gradually increasing; the implant is mainly made of cobalt-chromium metal material, and cartilage changes cannot be monitored after implantation. Thus, we aimed to develop a novel local articular resurfacing polyetheretherketone (PEEK) mini-implant and investigate its feasibility for postoperative magnetic resonance imaging (MRI) monitoring of implant location, bone changes, and cartilage degeneration without artefacts.

Methods: Nine skeletally mature female standardised goats were used and divided into the sham, PEEK, and cobalt-chromium-molybdenum alloy (Co-Cr-Mo) groups. The animals underwent local articular resurfacing operation with Co-Cr-Mo alloy (Co-Cr-Mo group) and PEEK (PEEK group) mini-implants. X-ray, computed tomography, and MRI examinations were performed at 12 weeks postoperatively. The sham group underwent a similar surgical procedure to expose the femoral head but without implantation. Gross necropsy and surface topography measurement of the articular cartilage of the acetabulum were performed after sacrificing the animals. Imaging artefacts and opposing cartilage degeneration in the acetabulum were also examined.

Results: Cartilage damage occurred in both the Co-Cr-Mo and PEEK groups, and the damaged cartilage area was markedly larger in the Co-Cr-Mo group than in the PEEK group, as assessed by gross necropsy and histological staining. The mean surface roughness of the opposing cartilage was approximately 65.3, 117.4, and 188.4 ​μm ​at 12 weeks in the sham, PEEK, and Co-Cr-Mo groups, respectively. The Co-Cr-Mo mini-implant was visualised on radiographs, but computed tomography and MR images were markedly affected by artefacts, whereas the opposing cartilage and surrounding tissue were clear on MR images in the PEEK group. Opposing cartilage damage and subchondral bone marrow oedema could be detected by MRI in the PEEK group.

Conclusions: The PEEK mini-implant can be a novel alternative to the Co-Cr-Mo mini-implant in articular resurfacing to treat focal osteochondral defects with less cartilage damage. It is feasible to postoperatively monitor the PEEK implant location, surrounding bone changes, and opposing cartilage degeneration by MRI without artefacts.

The Translational Potential Of This Article: The use of MRI to monitor changes in the opposing cartilage after prosthesis implantation has not been widely applied because MR images are generally affected by artefacts generated by the metal prosthesis. This study revealed that the PEEK mini-implant can be a novel alternative to the Co-Cr-Mo mini-implant in articular resurfacing to treat focal osteochondral defects, and it is feasible to monitor the PEEK implant location, surrounding bone changes, and opposing cartilage damage/degeneration by MRI without artefacts postoperatively.
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http://dx.doi.org/10.1016/j.jot.2020.02.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7773958PMC
January 2021

Microbial Perchlorate Reduction Driven by Ethane and Propane.

Environ Sci Technol 2021 02 12;55(3):2006-2015. Epub 2021 Jan 12.

Advanced Water Management Centre, The University of Queensland, St Lucia, Brisbane, Queensland 4072, Australia.

Previous studies demonstrated that methane can be used as an electron donor to microbially remove various oxidized contaminants in groundwater. Natural gas, which is more widely available and less expensive than purified methane, is potentially an alternative source of methane. However, natural gas commonly contains a considerable amount of ethane (CH) and propane (CH), in addition to methane. It is important that these gaseous alkanes are also utilized along with methane to avoid emissions. Here, we demonstrate that perchlorate (ClO), a frequently reported contaminant in groundwater, can be microbially reduced to chloride (Cl) driven by CH or CH under oxygen-limiting conditions. Two independent membrane biofilm reactors (MBfRs) supplied with CH and CH, respectively, were operated in parallel to biologically reduce ClO. The continuous ClO removal during long-term MBfR operation combined with the concurrent CH/CH consumption and ClO reduction in batch tests confirms that ClO reduction was associated with CH or CH oxidation. Polyhydroxyalkanoates (PHAs) were synthesized in the presence of CH or CH and were subsequently utilized for supporting ClO bio-reduction in the absence of gaseous alkanes. Analysis by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) showed that transcript abundance of (encoding alpha hydroxylase subunit of CH/CH monooxygenase) was positively correlated to the consumption rates of CH/CH, while (encoding a catalytic subunit of perchlorate reductase) was positively correlated to the consumption of ClO. High-throughput sequencing targeting 16S rRNA, , and indicated that was the dominant microorganism oxidizing CH/CH, while may be the major perchlorate-reducing bacterium in the biofilms. These findings shed light on microbial ClO reduction driven by CH and CH, facilitating the development of cost-effective strategies for ex situ groundwater remediation.
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http://dx.doi.org/10.1021/acs.est.0c04103DOI Listing
February 2021

Hierarchical macro-microporous WPU-ECM scaffolds combined with Microfracture Promote Articular Cartilage Regeneration in Rabbits.

Bioact Mater 2021 Jul 22;6(7):1932-1944. Epub 2020 Dec 22.

Institute of Orthopedics, Chinese PLA General Hospital, Beijing Key Lab of Regenerative Medicine in Orthopedics, Key Laboratory of Musculoskeletal Trauma & War Injuries PLA, No.28 Fuxing Road, Haidian District, Beijing, 100853, People's Republic of China.

Tissue engineering provides a promising avenue for treating cartilage defects. However, great challenges remain in the development of structurally and functionally optimized scaffolds for cartilage repair and regeneration. In this study, decellularized cartilage extracellular matrix (ECM) and waterborne polyurethane (WPU) were employed to construct WPU and WPU-ECM scaffolds by water-based 3D printing using low-temperature deposition manufacturing (LDM) system, which combines rapid deposition manufacturing with phase separation techniques. The scaffolds successfully achieved hierarchical macro-microporous structures. After adding ECM, WPU scaffolds were markedly optimized in terms of porosity, hydrophilia and bioactive components. Moreover, the optimized WPU-ECM scaffolds were found to be more suitable for cell distribution, adhesion, and proliferation than the WPU scaffolds. Most importantly, the WPU-ECM scaffold could facilitate the production of glycosaminoglycan (GAG) and collagen and the upregulation of cartilage-specific genes. These results indicated that the WPU-ECM scaffold with hierarchical macro-microporous structures could recreate a favorable microenvironment for cell adhesion, proliferation, differentiation, and ECM production. studies further revealed that the hierarchical macro-microporous WPU-ECM scaffold combined with the microfracture procedure successfully regenerated hyaline cartilage in a rabbit model. Six months after implantation, the repaired cartilage showed a similar histological structure and mechanical performance to that of normal cartilage. In conclusion, the hierarchical macro-microporous WPU-ECM scaffold may be a promising candidate for cartilage tissue engineering applications in the future.
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http://dx.doi.org/10.1016/j.bioactmat.2020.12.009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7772526PMC
July 2021

Advances and prospects in biomimetic multilayered scaffolds for articular cartilage regeneration.

Regen Biomater 2020 Dec 30;7(6):527-542. Epub 2020 Sep 30.

School of Medicine, Nankai University, No. 94 Weijin Road, Nankai District, Tianjin 300071, China.

Due to the sophisticated hierarchical structure and limited reparability of articular cartilage (AC), the ideal regeneration of AC defects has been a major challenge in the field of regenerative medicine. As defects progress, they often extend from the cartilage layer to the subchondral bone and ultimately lead to osteoarthritis. Tissue engineering techniques bring new hope for AC regeneration. To meet the regenerative requirements of the heterogeneous and layered structure of native AC tissue, a substantial number of multilayered biomimetic scaffolds have been studied. Ideal multilayered scaffolds should generate zone-specific functional tissue similar to native AC tissue. This review focuses on the current status of multilayered scaffolds developed for AC defect repair, including design strategies based on the degree of defect severity and the zone-specific characteristics of AC tissue, the selection and composition of biomaterials, and techniques for design and manufacturing. The challenges and future perspectives of biomimetic multilayered scaffold strategies for AC regeneration are also discussed.
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http://dx.doi.org/10.1093/rb/rbaa042DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7748444PMC
December 2020

Transformation of phthalates and their metabolites in wastewater under different sewer conditions.

Water Res 2021 Feb 15;190:116754. Epub 2020 Dec 15.

Queensland Alliance for Environmental Health Sciences (QAEHS), The University of Queensland, 4102, Brisbane, Australia. Electronic address:

There is an increasing demand to monitor the human exposure to phthalates, and a few studies have used phthalate metabolites in wastewater to estimate exposure to these chemicals in the population. However, it is suspected that the stability of phthalates and phthalate metabolites during sewer transport can influence the final estimates. In this study, we used laboratory sewer reactors to evaluate the in-sewer transformation of phthalates and their metabolites, and deconjugation of phthalate metabolites. We found concentrations of parent phthalates decreased quickly over time while the concentrations of phthalate metabolites increased significantly for most compounds, indicating that parent phthalate compounds are partly transformed into their metabolites in the sewer. Our assessment of the deconjugation of glucuronide-conjugated phthalate metabolites found that this process did not significantly affect the concentrations of phthalate metabolites in the wastewater, with the relative difference ranging from -16% to 7% between enzymatically treated samples and control group. Additionally, our results showed that phthalate metabolites could be subject to rapid degradation during the incubation process. Our findings suggested that the level of phthalate metabolites in sewage could be strongly influenced by the in-sewer transformation of the parent phthalates and of themselves, and could not be assumed as uniquely the results of urinary excretion after human exposure to parent phthalates.
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http://dx.doi.org/10.1016/j.watres.2020.116754DOI Listing
February 2021

An investigation into the impacts of water demand management and decentralized water recycling on excess sewer sediment deposition.

J Environ Manage 2021 Feb 10;279:111788. Epub 2020 Dec 10.

Cooperative Research Centre for Water Sensitive Cities, Level 1, 8 Scenic Boulevard (Building 74), Monash University, Clayton, VIC, 3800, Australia; Advanced Water Management Centre, Level 4, Gehrmann Laboratories Building (60), The University of Queensland, St Lucia, QLD, 4072, Australia. Electronic address:

Sewers are a critical part of the urban water system and represent a considerable investment due to the presence of extensive networks in many cities. Consequently, excess sewer sediment deposition, from changed inflow conditions or lack of appropriate sewer infrastructure, can lead to significantly increased maintenance and operational costs. The main aim of this manuscript is to quantify the potential impacts of reduced inflow and increased sediment concentrations from the implementation of sustainable water practices, such as Decentralized Water Recycling and Water Demand Management, on excess sediment deposition in gravity sewers. Experiments in a sewer pilot plant, with municipal wastewater, and modelling using a comprehensive local-scale sewer sediment model were used in conjunction to address this aim. Results from both these methods indicated that a reduction in inflows from the moderate implementation of sustainable water practices had a large impact on the quantity of sediment deposited in gravity sewers. However, further modelling showed that the reduction in bed erosion during peak flows for the same implementations of sustainable water practices occurred more gradually. Overall, our findings showed that in existing gravity sewer mains with reasonable slope and flow velocities, a moderate decrease in peak flow velocity of around 15% due to the implementation of Decentralized Water Recycling and Water Demand Management was unlikely to result in a net increase of sediment deposition. Future work in this area could focus on confirming these findings through case studies in the field or on long-term pilot studies with detailed bed height and density measurements.
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http://dx.doi.org/10.1016/j.jenvman.2020.111788DOI Listing
February 2021

The impact of primary sedimentation on the use of iron-rich drinking water sludge on the urban wastewater system.

J Hazard Mater 2021 01 22;402:124051. Epub 2020 Sep 22.

Advanced Water Management Centre, The University of Queensland, St Lucia, QLD 4072, Australia. Electronic address:

The impact of primary sedimentation on the multiple use of iron in an urban wastewater system was investigated. Our previous work showed that in-sewer iron-rich drinking water sludge (DWS) dosing exhibited multiple benefits in the downstream processes. However, the system studied did not include a primary settler. We hypothesised that primary sedimentation could significantly change the characteristics of the wastewater flowing to the bioreactor, particularly its particulate components. This could in turn influence the availability of iron for phosphate removal from wastewater and/or sulfide removal in the anaerobic sludge digester. Long-term (~4 months) experiments were carried out on two laboratory-scale wastewater systems, each comprising sewers reactors, a primary sedimentation tank, a wastewater treatment reactor, and an anaerobic sludge digester. It was found the majority (85%) of the Fe contained in the sewer effluent was present in the primary sludge with the remaining (15%) staying in the primary effluent. This significantly affected the flow-on effect of Fe on the phosphate removal during wastewater treatment, removing only 1.2 ± 0.1 mgP L, as compared to 3.5 ± 0.1 mgP L achieved previously in the absence of a primary settler. However, the P to Fe removal ratio was 0.32 mgP/mgFe, similar to the ratio observed previously without primary sedimentation (0.36 mgP/mgFe). The dissolved sulfide removal in the anaerobic digester was 2.7 ± 0.5 mgS L, substantially lower than 7.2 ± 0.3 mgS L previously attained without primary sedimentation. This suggests that Fe in the primary sludge was not completely available for dissolved sulfide removal in the digester. However, the dewaterability of the anaerobically digested sludge improved with a relative increase of 25.0 ± 0.9%, compared to the 21.7 ± 0.6%, previously observed without primary sedimentation. The results demonstrated that primary sedimentation reduced the effectiveness to deliver the benefits of the in-sewer DWS dosing strategy, but the results are still favourable.
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http://dx.doi.org/10.1016/j.jhazmat.2020.124051DOI Listing
January 2021

Study of free nitrous acid (FNA)-based elimination of sulfamethoxazole: Kinetics, transformation pathways, and toxicity assessment.

Water Res 2021 Feb 11;189:116629. Epub 2020 Nov 11.

State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, China, 100084. Electronic address:

Free nitrous acid (FNA)-based applications have been broadly adopted in the development of novel wastewater management technologies, but a basic understanding of the effect of the chemical properties of FNA on the elimination of micropollutants is still lacking. This study aims to comprehensively evaluate FNA-based elimination of sulfamethoxazole (SMX), which is a typical species of sulphonamide antibiotics. Batch experiments were conducted under different influencing factors to investigate the antibiotics elimination processes. We found that FNA showed specific efficacy on sulphonamides characterized by sulfonamide and aniline functional groups, such as SMX. SMX degradation was affected by the initial SMX concentration, FNA concentration and solution pH and described by d[SMX]/dt=-0.29e[SMX][FNA]. The cationic forms of SMX were more reactive towards FNA-based active components. Sulfonamide bond (S-N or C-S bonds) cleavage, nitrosubstitution, deamination and radical oxidation were proposed to be the relevant transformation pathways. The FNA-based technique was not effective for diminishing toxicity, but this process could strongly control antibacterial activity.
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http://dx.doi.org/10.1016/j.watres.2020.116629DOI Listing
February 2021

Anaerobic Oxidation of Methane Coupled with Dissimilatory Nitrate Reduction to Ammonium Fuels Anaerobic Ammonium Oxidation.

Environ Sci Technol 2021 01 13;55(2):1197-1208. Epub 2020 Nov 13.

School of Environment, State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, No. 73, Huanghe Road, Nangang, Harbin 150090, Heilongjiang, China.

Nitrate/nitrite-dependent anaerobic methane oxidation (n-DAMO) is critical for mitigating methane emission and returning reactive nitrogen to the atmosphere. The genomes of n-DAMO archaea show that they have the potential to couple anaerobic oxidation of methane to dissimilatory nitrate reduction to ammonium (DNRA). However, physiological details of DNRA for n-DAMO archaea were not reported yet. This work demonstrated n-DAMO archaea coupling the anaerobic oxidation of methane to DNRA, which fueled Anammox in a methane-fed membrane biofilm reactor with nitrate as only electron acceptor. Microelectrode analysis revealed that ammonium accumulated where nitrite built up in the biofilm. Ammonium production and significant upregulation of gene expression for DNRA were detected in suspended n-DAMO culture with nitrite exposure, indicating that nitrite triggered DNRA by n-DAMO archaea. N-labeling batch experiments revealed that n-DAMO archaea produced ammonium from nitrate rather than from external nitrite. Localized gradients of nitrite produced by n-DAMO archaea in biofilms induced ammonium production via the DNRA process, which promoted nitrite consumption by Anammox bacteria and in turn helped n-DAMO archaea resist stress from nitrite. As biofilms predominate in various ecosystems, anaerobic oxidation of methane coupled with DNRA could be an important link between the global carbon and nitrogen cycles that should be investigated in future research.
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http://dx.doi.org/10.1021/acs.est.0c02664DOI Listing
January 2021

Critical Factors Facilitating Nitrotoga To Be Prevalent Nitrite-Oxidizing Bacteria in Activated Sludge.

Environ Sci Technol 2020 12 12;54(23):15414-15423. Epub 2020 Nov 12.

State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China.

Nitrite oxidation is the primary pathway that generates nitrate in engineered systems. However, little is known about the role of a novel nitrite-oxidizing bacteria (NOB) genus Nitrotoga in activated sludge systems. To elucidate key factors that impact NOB community composition, laboratory-scale sequencing batch reactors (SBRs) were designed and operated under the same conditions as real wastewater treatment plants to achieve considerable nitrogen removal and similar community; then, different conditions including temperature (T), dissolved oxygen (DO), free nitrous acid (FNA), and free ammonia (FA) were applied. The 16S rRNA gene-based PCR and sequence analysis illustrated that . Nitrotoga were abundant even at ambient temperature, thus further challenging the previous conception of them being solely cold-adapted. . Nitrotoga are less competitive than during oxygen deficiency, indicating its lower affinity to dissolved oxygen. . Nitrotoga are the dominant nitrite oxidizers under regular exposure to FNA and FA due to their relatively higher resistance than other NOB toward these two effective biocides. Therefore, this study demonstrates that . Nitrotoga can play an important role in biological nitrogen removal and also highlights the need for multiple strategies for NOB suppression for the next-generation, shortcut nitrogen removal.
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http://dx.doi.org/10.1021/acs.est.0c04192DOI Listing
December 2020

Formation and partitioning behaviour of perfluoroalkyl acids (PFAAs) in waste activated sludge during anaerobic digestion.

Water Res 2021 Feb 30;189:116583. Epub 2020 Oct 30.

Advanced Water Management Centre, The University of Queensland, St. Lucia, QLD 4072, Australia. Electronic address:

The formation and fate of perfluoroalkyl acids (PFAAs) in sludge during anaerobic digestion (AD) is of global importance since the sludge is a significant source of PFAAs to the environment. The formation of PFAAs from polyfluorinated compounds, namely PFAA precursors, is poorly understood in AD. This study aims to investigate the formation of PFAAs from precursors and their partitioning behaviour in waste activated sludge (WAS) during AD process. To achieve this, three isotope-labelled PFAAs were spiked and monitored along with indigenous PFAAs and precursors over eight weeks in a laboratory-scale anaerobic digester, fed with sludge from a local wastewater treatment plant and operated with a hydraulic retention time of 12 days under 35 ℃. In addition to isotope-labelled PFAAs, twelve native PFAAs and eight polyfluorinated compounds were detected in the feed and digested sludges. A mass-balance model, validated by the spiking experiment, was applied to predict the concentrations of PFAAs and precursors assuming no formation/degradation in AD. The measured concentrations of short-chain PFAAs (perfluoroalkyl carboxylates (PFCAs): C < 8; perfluoroalkane sulfonates (PFSAs): C < 6) in the AD sludge were significantly (p < 0.05) higher than the model-predicted concentrations, indicating the formation of these PFAAs from precursors in AD. In contrast, the formation of long-chain PFAAs (PFCAs: C ≥ 8; PFSAs: C ≥ 6) was not observed. Moreover, the degradation of two polyfluoroalkyl phosphates (PAPs) (6:2 PAP and 6:2/8:2 diPAP) occurred, evidenced by their measured concentrations that were statistically lower than the mass-balance predictions. Further, the AD process reduced the amount of PFAAs absorbed/adsorbed to sludge, particularly for the long-chain ones, due to the breakdown of solids.
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http://dx.doi.org/10.1016/j.watres.2020.116583DOI Listing
February 2021

Structural changes in model compounds of sludge extracellular polymeric substances caused by exposure to free nitrous acid.

Water Res 2021 Jan 23;188:116553. Epub 2020 Oct 23.

Advanced Water Management Centre (AWMC), The University of Queensland, QLD 4072, Australia. Electronic address:

Previous studies demonstrate that free nitrous acid (FNA i.e. HNO) detaches sewer biofilms, breaks down flocs of waste activated sludge (WAS) and enhances biogas production from WAS. This suggests possible interactions of FNA with organic extracellular polymeric substances (EPS) that bind the cells into biofilms or sludge flocs. This study evaluates the chemical interactions and reaction mechanisms between FNA and molecules representative of key EPS in biofilm and sludge flocs. Molecules chosen to represent components found in the extracellular polymeric matrix were treated with FNA at 6.09 mgN/L (NO = 250 mgN/L, pH = 5.0 ± 0.2, T = 22 °C) for 24 hours (conditions typically used in applications) so as to consider the hypothesized chemical interactions and the consequent reaction pathways. A number of analytical techniques were employed to measure the molecular changes in the EPS molecules including; proton (H) nuclear magnetic resonance spectroscopy (NMR), electrospray ionisation mass spectrometry (ESI-MS) and gel permeation chromatography (GPC). The results demonstrated that FNA broke down a range of large EPS molecules including carbohydrates, protein and lipids to smaller molecules. Two mechanistic pathways have been proposed including electrophilic substitution, whereby the nitrosium ion (NO) was the reactive electrophile, and oxidative radical reactions, through which the nitrogen radicals (NO, NO) and reactive nitrogen intermediates (RNIs) (e.g. NO and NO) formed from the decomposition of FNA became part of the reaction products. Larger, more complex organic molecules such as humic acid, required higher concentrations of FNA (6.09 mgN/L or greater) to cause molecular breakdown, whereas smaller molecules, such as calcium alginate, was broken down at lower concentrations (3.04 mgN/L). The study contributes to the understanding of the fundamental mechanisms behind the application of FNA for biofilm control and flocular sludge disintegration.
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http://dx.doi.org/10.1016/j.watres.2020.116553DOI Listing
January 2021

Enhancing methane oxidation in a bioelectrochemical membrane reactor using a soluble electron mediator.

Biotechnol Biofuels 2020 16;13:173. Epub 2020 Oct 16.

Advanced Water Management Centre, Faculty of Engineering, Architecture and Information Technology, The University of Queensland, Brisbane, 4072 Australia.

Background: Bioelectrochemical methane oxidation catalysed by anaerobic methanotrophic archaea (ANME) is constrained by limited methane bioavailability as well as by slow kinetics of extracellular electron transfer (EET) of ANME. In this study, we tested a combination of two strategies to improve the performance of methane-driven bioelectrochemical systems that includes (1) the use of hollow fibre membranes (HFMs) for efficient methane delivery to the ANME organisms and (2) the amendment of ferricyanide, an effective soluble redox mediator, to the liquid medium to enable electrochemical bridging between the ANME organisms and the anode, as well as to promote EET kinetics of ANME.

Results: The combined use of HFMs and the soluble mediator increased the performance of ANME-based bioelectrochemical methane oxidation, enabling the delivery of up to 196 mA m, thereby outperforming the control system by 244 times when HFMs were pressurized at 1.6 bar.

Conclusions: Improving methane delivery and EET are critical to enhance the performance of bioelectrochemical methane oxidation. This work demonstrates that by process engineering optimization, energy recovery from methane through its direct oxidation at relevant rates is feasible.
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http://dx.doi.org/10.1186/s13068-020-01808-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7568384PMC
October 2020

Advanced Polymer-Based Drug Delivery Strategies for Meniscal Regeneration.

Tissue Eng Part B Rev 2020 Oct 27. Epub 2020 Oct 27.

School of Medicine, Nankai University, Tianjin, China.

The meniscus plays a critical role in maintaining knee joint homeostasis. Injuries to the meniscus, especially considering the limited self-healing capacity of the avascular region, continue to be a challenge and are often treated by (partial) meniscectomy, which has been identified to cause osteoarthritis. Currently, meniscus tissue engineering focuses on providing extracellular matrix (ECM)-mimicking scaffolds to direct the inherent meniscal regeneration process, and it has been found that various stimuli are essential. Numerous bioactive factors present benefits in regulating cell fate, tissue development, and healing, but lack an optimal delivery system. More recently, bioengineers have developed various polymer-based drug delivery systems (PDDSs), which are beneficial in terms of the favorable properties of polymers as well as novel delivery strategies. Engineered PDDSs aim to provide not only an ECM-mimicking microenvironment but also the controlled release of bioactive factors with release profiles tailored according to the biological concerns and properties of the factors. In this review, both different polymers and bioactive factors involved in meniscal regeneration are discussed, as well as potential candidate systems, with examples of recent progress. This article aims to summarize drug delivery strategies in meniscal regeneration, with a focus on novel delivery strategies rather than on specific delivery carriers. The current challenges and future prospects for the structural and functional regeneration of the meniscus are also discussed. Impact statement Meniscal injury remains a clinical Gordian knot owing to the limited healing potential of the region, restricted surgical approaches, and risk of inducing osteoarthritis. Existing tissue engineering scaffolds that provide mechanical support and a favorable microenvironment also lack biological cues. Advanced polymer-based delivery strategies consisting of polymers incorporating bioactive factors have emerged as a promising direction. This article primarily reviews the types and applications of biopolymers and bioactive factors in meniscal regeneration. Importantly, various carrier systems and drug delivery strategies are discussed with the hope of inspiring further advancements in this field.
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http://dx.doi.org/10.1089/ten.TEB.2020.0156DOI Listing
October 2020