Imperial College London

Dr Po-Heng (Henry) Lee

Faculty of EngineeringDepartment of Civil and Environmental Engineering

Senior Lecturer in Wastewater Engineering
 
 
 
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Contact

 

+44 (0)20 7594 5993po-heng.lee

 
 
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Location

 

310ASkempton BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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75 results found

Ji X, Leng L, Wu Z, Sung S, Lee PHet al., 2021, Underpinning unique genes in Ca. Brocadia sp. and its interspecies association potentials in a partial nitrification/anammox system with low-strength wastewater, Chemical Engineering Journal, Vol: 405, ISSN: 1385-8947

© 2020 Elsevier B.V. Anaerobic ammonia oxidation (anammox) incorporated with anaerobic treatment with sewage offers an energy-efficient option. With the substrate in scare from anaerobically-treated sewage, the dominated anammox species, their mechanisms, and interspecies interaction remain unclear. Here, we enriched and operated a partial nitrification (PN)- anammox (A) fluidized-bed bioreactor (FBR) containing granular activated carbon (GAC) inoculated from a conventional activated sludge with a synthetic low-strength wastewater under a dissolved oxygen concentration of 0.7 mg/L. It achieved over 53% of total nitrogen removal without anammox seed. Our meta-omics analyses revealed an enriched anammox strain affiliated to Ca. Brocadia sp. with a relative abundance of 11.18% and 26.96% in the bulk and biofilm, respectively. Genes encoding dissimilatory nitrate reduction to ammonium (DNRA) and heterotrophic anabolism in this strain were recovered, suggesting its potential in a flexible nitrogen stochiometric feed ratio through organics utilization. Furthermore, 17 and 19 high-quality draft genomes yielded from the bulk and biofilm, respectively support the interspecies interaction capacity between Ca. Brocadia sp. and other nitrogen cycle microorganisms through nitrite loop and vitamin B12 exchange. By offering such overlooked pathways and their interspecies linkages between Ca. Brocadia sp. and other microbes, our study facilitates its mainstream application.

Journal article

Huang X, Lee PH, 2021, Shortcut nitrification/denitrification through limited-oxygen supply with two extreme COD/N-and-ammonia active landfill leachates, Chemical Engineering Journal, Vol: 404, ISSN: 1385-8947

© 2020 Elsevier B.V. Shortcut nitrification/denitrification (N/DN) was carried out through limited dissolved oxygen supply (DO, 0.5–0.8 mg/L) with active air-stripping treated (COD/N of 10.1 and 615.7 mg N/L ammonia) and raw leachate (COD/N of 2.2 and 3596.3 mg N/L ammonia). The reactor demonstrated robust performance, achieving maximum removal rates of 5.33 kg COD/m3/d and 1.2 kg N/m3/d under 0.6 mg/L DO supply. 16S rRNA gene amplicon sequencing analysis revealed that Nitrosomonas holding around 1.0% responded to ammonia oxidation, while nitrite oxidizing bacteria were suppressed. For the air-stripping treated leachate, abundant and diverse denitrifying populations (e.g. Paracoccus, Pseudomonas, Roseimaritima, and Thauera) were likely responding for total nitrogen (TN) and COD removal. Feeding the raw leachate, apart from heterotrophic denitrifiers contributing to auxiliary COD and TN removal, lithotrophic denitrifiers using sulfur and/or sulfide as electron donors were associated with sulphur reducing bacteria, suggesting that the changing of feeding strength propelled a remarkable shift of denitrifying populations. An unexpected observation was found that Candidatus Anammoximicrobium sp., previously reported in dilute wastewaters, proliferated and accounted for 0.63% whilst the reactor was fed with active raw leachate (rich in ammonia nitrogen and COD). Functional profiles prediction suggested that methyl compounds metabolization and aromatic compounds degradation might actively perform. This study validated that the shortcut N/DN could be achieved by a limited oxygen supply for high COD/N wastewaters (e.g., over 9) and leads to immediately beneficial to the treatment of relevant wastewaters.

Journal article

Nobu MK, Narihiro T, Mei R, Kamagata Y, Lee PKH, Lee P-H, McInerney MJ, Liu W-Tet al., 2020, Catabolism and interactions of uncultured organisms shaped by eco-thermodynamics in methanogenic bioprocesses., Microbiome, Vol: 8

BACKGROUND: Current understanding of the carbon cycle in methanogenic environments involves trophic interactions such as interspecies H2 transfer between organotrophs and methanogens. However, many metabolic processes are thermodynamically sensitive to H2 accumulation and can be inhibited by H2 produced from co-occurring metabolisms. Strategies for driving thermodynamically competing metabolisms in methanogenic environments remain unexplored. RESULTS: To uncover how anaerobes combat this H2 conflict in situ, we employ metagenomics and metatranscriptomics to revisit a model ecosystem that has inspired many foundational discoveries in anaerobic ecology-methanogenic bioreactors. Through analysis of 17 anaerobic digesters, we recovered 1343 high-quality metagenome-assembled genomes and corresponding gene expression profiles for uncultured lineages spanning 66 phyla and reconstructed their metabolic capacities. We discovered that diverse uncultured populations can drive H2-sensitive metabolisms through (i) metabolic coupling with concurrent H2-tolerant catabolism, (ii) forgoing H2 generation in favor of interspecies transfer of formate and electrons (cytochrome- and pili-mediated) to avoid thermodynamic conflict, and (iii) integration of low-concentration O2 metabolism as an ancillary thermodynamics-enhancing electron sink. Archaeal populations support these processes through unique methanogenic metabolisms-highly favorable H2 oxidation driven by methyl-reducing methanogenesis and tripartite uptake of formate, electrons, and acetate. CONCLUSION: Integration of omics and eco-thermodynamics revealed overlooked behavior and interactions of uncultured organisms, including coupling favorable and unfavorable metabolisms, shifting from H2 to formate transfer, respiring low-concentration O2, performing direct interspecies electron transfer, and interacting with high H2-affinity methanogenesis. These findings shed light on how microorganisms overcome a critical obstacle in m

Journal article

Wei SP, Stensel HD, Nguyen Quoc B, Stahl DA, Huang X, Lee P-H, Winkler M-KHet al., 2020, Flocs in disguise? High granule abundance found in continuous-flow activated sludge treatment plants., Water Res, Vol: 179

To date, high performance of full-scale aerobic granular sludge (AGS) technology has been demonstrated on a global scale. Its further integration with existing continuous flow activated sludge (CFAS) treatment plants is the next logical step. All granular sludge reactors operated in sequencing batch reactors (SBR) mode with anaerobic feeding conditions select for growth of phosphorus and glycogen accumulating organisms (PAO and GAO, respectively), which are known to enhance sludge settling characteristics. Therefore, we hypothesized that AGS are commonly present at full-scale CFAS processes with enhanced biological phosphorus removal (EBPR) and low sludge volume index (SVI). This hypothesis was confirmed at 13 EBPR plants, where granules were found present (at plants where SVI was lower than 100 ml/g) with a strong correlation between high granule abundance and low SVI. A wide range of granule abundance was found among the plants, ranging from 0.5% to as high as 80%. Evaluations of the EBPR plant process configurations showed that high granule abundances may be related to selector design features such as high anaerobic food to mass (F/M) ratios, unmixed in-line fermentation, and high influent soluble COD fraction. Granules were also observed at a non-EBPR plant with an aerobic selector receiving high F/M feeds. Quantitative PCR and 16S rRNA gene sequencing analyses revealed higher relative gene abundance of Accumulibacter PAO and Competibacter GAO in the granules over flocs, as well as a correlation between granule abundance and some possible EPS producers such as Flavobacterium and Competibacter. Our results indicated that process configurations that select for slow-growing or EPS-producing heterotrophs play an important role for granule formation in full-scale CFAS systems as previously shown in SBR configurations.

Journal article

Lam TYC, Mei R, Wu Z, Lee PKH, Liu W-T, Lee P-Het al., 2020, Superior resolution characterisation of microbial diversity in anaerobic digesters using full-length 16S rRNA gene amplicon sequencing., Water Res, Vol: 178

In the past decade, the characterisation of the microbial community in anaerobic digestion was primarily done by using high-throughput short-read amplicon sequencing. However, the short-read approach has inherent primer bias and low phylogenetic resolution. Our previous study using Illumina MiSeq suggested that the heterogeneity of AD microbiome was operation-driven. To advance our knowledge towards the complexity of the AD microbiome, we performed full-length 16S rRNA gene amplicon sequencing using PacBio Sequel for a more accurate phylogenetic identification. To this end, purified DNA samples from 19 global anaerobic digesters were sequenced. Sixteen methanogenic archaea were identified at the species level. Among them, Methanosarcina horonobensis and Methanosarcina flavescens had significant presence under specific operating conditions. Methanothrix concilii presented in all digesters sequenced. Unexpectedly, over 90% of the Smithella detected were closely related to alkane-degrading Smithella strains D17 and M82, not Smithella propionica. Using LEfSe and network analysis, the interspecies relationship between the fermentative and syntrophic bacteria was addressed. Comparison of the short- and long-read sequencing results were performed and discussed. From sample preparation to data analysis, this work characterised the digester microbiomes in a superior resolution.

Journal article

Kim M, Lam TYC, Tan G-YA, Lee P-H, Kim Jet al., 2020, Use of polymeric scouring agent as fluidized media in anaerobic fluidized bed membrane bioreactor for wastewater treatment: System performance and microbial, JOURNAL OF MEMBRANE SCIENCE, Vol: 606, ISSN: 0376-7388

Journal article

Xu L, Pang Y, Huang D, Zhuang H, Luo T, Lee P-H, Liu W, Zhang S, Feng Let al., 2020, Increasing ammonia recovery from high-level ammonium wastewater via adding sodium sulfate to prevent nitrogen generation in the cathode., Environ Res, Vol: 186

The high-level ammonium-nitrogen (NH4+-N) is a contaminant for aqueous environment but a potential hydrogen fuel. This study investigated an approach of increasing ammonia recovery via adding sodium sulfate of 0-1.5 M to prevent from nitrogen generation. The results of experiment tests, electrochemical analysis and MD simulation demonstrated that the added Na2SO4 assisted ammonium transport inhibited nitrogen gas generation in a certain concentration range. In electric double layer (EDL), with Na2SO4 concentration increasing, both the migration velocities of NH4+ and Na+ are accelerated for Na2SO4 of 0-0.25 M, whereas they are decelerated for concentrate Na2SO4 that 0.5 M). A thick layer formed by Na+ that imposed a fierce competitive adsorption blocked the migration of NH4+ and the transportation of electrons. The decrease of electrons and the accumulation of water molecules caused the potential drop in the EDL. 0.25 M Na2SO4 was the optimal concentration from the aspect of ion transports. The results obtained in this study can allow the manipulation of EDI capacity optimization.

Journal article

Lee P-H, 2020, Energy-efficient single-stage nitrite shunt denitrification with saline sewage through concise dissolved oxygen (DO) supply: Process performance and microbial communities, Microorganisms, Vol: 8, Pages: 1-13, ISSN: 2076-2607

Single-stage nitrite shunt denitrification (through nitrite rather than nitrate) with low dissolved oxygen (DO) supply is a better alternative in terms of energy-efficiency, short-footprint, and low C/N-ratio requirement. This study investigates the optimal DO level with temperature effect, with saline sewage at the fixed hydraulic and solids retention times of 8 h and 8 d, respectively. Moreover, 16S rRNA gene sequencing analysis corresponding with total nitrogen (TN) and chemical oxygen demand (COD) removals in each operating condition were performed. Results showed that DO of 0.3 mg/L at 20 °C achieved over 60.7% and over 97.9% of TN and COD removal, respectively, suggesting that such condition achieved effective nitrite-oxidizing bacteria inhibition and efficient denitrification. An unexpected finding was that sulfur-reducing Haematobacter and nitrogen-fixing Geofilum and Shinella were highly abundant with the copredominance of ammonia-oxidizing Comamonas and Nitrosomonas, nitrite-oxidizing Limnohabitans, and denitrifying Simplicispira, Castellaniella, and Nitratireductor. Further, canonical correspondence analysis (CCA) with respect to the operating conditions associated with phenotype prediction via R-based tool Tax4Fun was performed for a preliminary diagnosis of microbial functionality. The effects of DO, temperature, nitrite, and nitrate in various extents toward each predominant microbe were discussed. Collectively, DO is likely pivotal in single-stage nitrite shunt denitrification, as well as microbial communities, for energy-efficient saline sewage treatment.

Journal article

Ji X, Wang Y, Lee P-H, 2020, Evolution of microbial dynamics with the introduction of real seawater portions in a low-strength feeding anammox process., Appl Microbiol Biotechnol, Vol: 104, Pages: 5593-5604

The salinity effect on anammox bacteria has been widely reported; however, rare studies describe the microbial dynamics of anammox-based process response to the introduction of real seawater at mainstream conditions. In this study, an anammox process at mainstream conditions without pre-enriching anammox bacteria was shifted to the feeds of a synthetic wastewater with a portion of seawater mixture. It achieved over 0.180 kg-N/(m3 day) of nitrogen removal rate with an additional seawater proportion of 20% in the influent. The bacterial biodiversity was significantly increased with the increase of seawater proportions. High relative abundance of anammox bacteria (34.24-39.92%) related to Ca. Brocadia was enriched and acclimated to the saline environment. However, the introduction of seawater caused the enrichment of nitrite-oxidizing Ca. Nitrospira, which was responsible for the deterioration of nitrogen removal efficiency. Possible adaptation metabolisms in anammox bacteria and other nitrogen transforming bacteria are discussed. These results highlight the importance of microbial diversity for anammox process under the saline environments of 20% and 40% seawater composition.

Journal article

Wu P-H, Lai Y-Z, Zhang Y-P, Sil MC, Lee P-HH, Wei T-C, Chen C-Met al., 2020, Organosiloxane Monolayers Terminated with Amine Groups as Adhesives for Si Metallization, ACS APPLIED NANO MATERIALS, Vol: 3, Pages: 3741-3749, ISSN: 2574-0970

Journal article

Alvarado V, Hsu S-C, Lam C-M, Lee P-Het al., 2020, Beyond Energy Balance: Environmental Trade-Offs of Organics Capture and Low Carbon-to-Nitrogen Ratio Sewage Treatment Systems, ENVIRONMENTAL SCIENCE & TECHNOLOGY, Vol: 54, Pages: 4746-4757, ISSN: 0013-936X

Journal article

Li B, Zheng T, Ran S, Sun M, Shang J, Hu H, Lee P-H, Boles STet al., 2020, Performance Recovery in Degraded Carbon-Based Electrodes for Capacitive Deionization, ENVIRONMENTAL SCIENCE & TECHNOLOGY, Vol: 54, Pages: 1848-1856, ISSN: 0013-936X

Journal article

Nguyen D, Wu Z, Shrestha S, Lee P-H, Raskin L, Khanal SKet al., 2019, Intermittent micro-aeration: New strategy to control volatile fatty acid accumulation in high organic loading anaerobic digestion., Water Res, Vol: 166

This study developed an intermittent oxidation-reduction potential (ORP)-controlled micro-aeration system for high solids anaerobic digestion (AD) of lignocellulosic biomass without volatile fatty acids (VFA) accumulation at high organic loading rate (OLR). Traditional AD of Napier grass, a model lignocellulosic biomass, at an OLR of 5 g volatile solids (VS)/L/day resulted in an accumulation of total VFA concentration up to 9.2 g/L as acetic acid (HAc) equivalent, causing rapid drops in pH and methane yield, and driving the digester to the verge of failure. Once intermittent (every 24 h) ORP-controlled micro-aeration (at ORP of -470 mV) was initiated, the total VFA concentration rapidly decreased to 3.0 g HAc/L and the methane yield improved, resulting in stable digester performance without the need for alkalinity supplementation or OLR reduction. By combining reactor performance results, mass balance analyses, microbial community characterization data, and a bioenergetic evaluation, this study suggested that rapid VFA conversion and CH4 production were carried out by facultative anaerobes and hydrogenotrophic methanogens under micro-aerobic conditions. This novel operating approach can be applied as an effective control strategy for high OLR AD processes especially in the event of VFA accumulation.

Journal article

Ji X, Wu Z, Sung S, Lee P-Het al., 2019, Metagenomics and metatranscriptomics analyses reveal oxygen detoxification and mixotrophic potentials of an enriched anammox culture in a continuous stirred-tank reactor., Water Res, Vol: 166

The metabolisms of anaerobic ammonium oxidation (anammox) bacteria related to ammonia oxidation with nitrite reduction and autotrophic carbon fixation have been extensively observed. However, little is known about the specific metabolic pathways associated with oxygen detoxification and organic carbon utilization. To this end, we obtained high abundance of anammox species (∼50%) in a lab-scale continuous stirred-tank reactor (CSTR) at room temperature without strict anaerobic condition. The draft genome of the dominant anammox bacteria affiliated to Ca. Brocadia sp. was recovered. Its metabolic pathways and genes expression were reconstructed and examined through metagenomic and metatranscriptomic analyses. Interestingly, the results suggested that this anammox lineage likely performs oxygen detoxification with genes encoding superoxide dismutase (SOD) and cytochrome c peroxidase (Ccp). Moreover, the Ccp-activated hydrogen peroxide (intermediate of oxygen detoxification) reduction might be energetically beneficial for the observed acetate conversion related to cell synthesis of Ca. Brocadia sp. This study offers a comprehensive understanding on the diverse metabolic activities in anammox species affiliated to Ca. Brocadia sp., and expanded the applicability of anammox process.

Journal article

Leng L, Wang Y, Yang P, Narihiro T, Nobu MK, Tan AGY, Lee HPHet al., 2019, Unravelling a microbial synergy to boost caproate production via carboxylates chain elongation with ethanol, HKIE Transactions Hong Kong Institution of Engineers, Vol: 26, Pages: 63-71, ISSN: 1023-697X

© 2019 The Hong Kong Institution of Engineers. Chain elongation of volatile fatty acids for medium chain fatty acids production (e.g. caproate) is an attractive approach to treat wastewater anaerobically and recover resource simultaneously. Undefined microbial consortia can be tailored to achieve chain elongation process with selective enrichment from anaerobic digestion sludge, which has advantages over pure culture approach for cost-efficient application. Whilst the metabolic pathway of the dominant caproate producer, Clostridium kluyveri, has been annotated, the role of other coexisting abundant microbiomes remained unclear. To this end, an ethanol-acetate fermentation inoculated with fresh digestion sludge at optimal conditions was conducted. Also, physiological study, thermodynamics and 16 S rRNA gene sequencing to elucidate the biological process by linking the system performance and dominant microbiomes were integrated. Results revealed a possible synergistic network in which C. kluyveri and three co-dominant species, Desulfovibrio vulgaris, Fusobacterium varium and Acetoanaerobium sticklandii coexisted. D. vulgaris and A. sticklandii (F. varium) were likely to boost the carboxylates chain elongation by stimulating ethanol oxidation and butyrate production through a syntrophic partnership with hydrogen (H2) serving as an electron messenger. This study unveils a synergistic microbial network to boost caproate production in mixed culture carboxylates chain elongation.

Journal article

Alvarado VI, Hsu S-C, Wu Z, Lam C-M, Leng L, Zhuang H, Lee P-Het al., 2019, A Standardized Stoichiometric Life-Cycle Inventory for Enhanced Specificity in Environmental Assessment of Sewage Treatment., Environ Sci Technol, Vol: 53, Pages: 5111-5123

In recent years, many life-cycle assessments (LCAs) have been applied to the field of sewage treatment (ST). However, most LCAs lack systematic data collection (DC) and processing methods for inventories of conventional ST (CST), much less for recently developed technologies. In addition, the use of site-generic databases results in LCAs that lack the representativeness and understanding of the regional environmental impacts and trade-offs between different impact categories, especially nutrient enrichment and toxicity-related categories. These shortcomings make comparative evaluation and implementation more challenging. In order to assist in the decision-making process, a novel stoichiometric life-cycle inventory (S-LCI) for ST was developed. In the S-LCI, biochemical pathways derived from elemental analyses combined with process-engineering calculations enable steady-state comparison of the water, air, and soil emissions of any sewage and sludge sample treated through the ST configurations analyzed herein. The DC required for the estimation of the foreground data for a CST is summarized in a 41-item checklist. Moreover, the S-LCI was validated for CST by comparing the S-LCI with actual ST plant operations performed in Hong Kong. A novel energy-derived ST inventory is developed and compared here with the CST. The resulting inventories are ready to be integrated into the SimaPro software for life cycle impact assessment as illustrated by the case study. Using the S-LCI not only helps to standardize the DC and processing, but it also enhances the level of specificity by using sample characterization and site-specific data. The EcoInvent database, which contains a single sample characterization per Swiss and global average ST plant class could be expanded by using the S-LCI.

Journal article

Wang J, Zhao Y-Y, Lee P-H, Wu Ket al., 2019, Computational analysis of non-heme iron-oxo formation by direct NO release in nitrite reduction., Phys Chem Chem Phys, Vol: 21, Pages: 6643-6650

A direct NO-releasing reaction of nitrite catalyzed by [N(afaCy)3Fe(OTf)]+ (afa (azafulvene-amine); OTf (trifluoromethanesulfonate); Cy (cyclohexyl)) was investigated using density functional theory (DFT) with D3 dispersion correction. The complex featured a secondary coordination sphere that facilitated the formation of the iron-oxo product [N(afaCy)3FeO]+ with three (Fe)OH-N hydrogen bonds. As a high-spin iron(ii), the O-binding initial intermediate Fe(O)-nitrito was thermodynamically favorable in the S = 2 state. The cleavage of the (Fe)O-NO bond was performed by a β-electron shift to produce Fe(iii)-O by electron rearrangement in the S = 5/2 state. The different electron configurations are responsible for the structural properties, the valence of iron in the complexes, and the pathways of the reactions. Moreover, the two different H-bonds, (Fe)OH-N and (Fe)O-HN (by O-protonation), in the product complexes played a role in determining the reaction channels by impacting the N-H bond rotation. Thus, an exothermic sequence of conversions Fe(ii) → Fe(iii)-O → Fe(iii)-OH → Fe(iii)-O was established for the targeted product formation. This process provided a clue to build two key intermediates, iron-oxo and iron-hydroxo, in a variety of biological and synthetic systems. The results of this study are in agreement with experimental observations and describe the roles of H-bonding in nitrite reduction catalyzed by the non-heme iron complex.

Journal article

Liang Q, Zhuang H, Lu M, Wang Q, Attalage D, Hsu S-C, Chen W-H, Xing D, Lee P-Het al., 2019, Multi-agent simulation regulated by microbe-oriented thermodynamics and kinetics equations for exploiting interspecies dynamics and evolution between methanogenesis, sulfidogenesis, hydrogenesis and exoelectrogenesis., J Hazard Mater, Vol: 366, Pages: 573-581

Multi-agent simulation (MAS) regulated by microbe-oriented thermodynamics and kinetics equations were performed for exploiting the interspecies dynamics and evolution in anaerobic respiration and bioelectrochemical systems. A newly-defined kinetically thermodynamic parameter is recognized microbes as agents in various conditions, including electron donors and acceptors, temperature, pH, etc. For verification of the MAS, the treatment of synthetic wastewater containing glucose and acetate was evaluated in four 25°C laboratory-scale reactors with different electron acceptors and cathode materials that had potential for methanogenesis, hydrogenesis, sulfidogenesis and exoelectrogenesis. Within 1000 h operation, the reactors performance and microbial structures using 16S rRNA sequencing matched with the MAS, suggesting acetoclastic exoelectrogenesis predominance (Geobacter). After 2400 h, MAS observed the co-existence of acetoclastic methanogenesis and acetoclastic and propionate exoelectrogenesis, as was reported previously. Such microbial evolution from the short-term to long-term operation likely resulted from the glucose-driven propionate. The MAS developed is applicable in a wide range of complex engineering and natural ecosystems.

Journal article

Yang Z, Li H, Yang J, Feng S, Liu X, Zhao J, Qu W, Li P, Feng Y, Lee PH, Shih Ket al., 2019, Nanosized Copper Selenide Functionalized Zeolitic Imidazolate Framework-8 (CuSe/ZIF-8) for Efficient Immobilization of Gas-Phase Elemental Mercury, Advanced Functional Materials, ISSN: 1616-301X

© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim A key challenge in elemental mercury (Hg 0 ) decontamination from flue gas lies in the design of a sorbent with abundant reactive adsorption sites that exhibit high affinity toward Hg 0 to simultaneously achieve rapid capture and large capacity. Herein, zeolitic imidazolate framework-8 (ZIF-8) supported copper selenide (CuSe) nanocomposites are synthesized by a newly designed two-step surfactant-assisted method. The as-prepared CuSe/ZIF-8 with CuSe to ZIF-8 mass ratio of 80% (0.8NC-ZIF) exhibits unparalleled performance toward Hg 0 adsorption with equilibrium capacity and average rate reaching 309.8 mg g −1 and 105.3 µg g −1 min −1 , respectively, surpassing all reported metal sulfides and traditional activated-carbon-based sorbents. The impressive performance of 0.8NC-ZIF for Hg 0 immobilization is primarily attributed to the adequate exposure of the Se-terminated sites with high affinity toward Hg 0 resulted from the layered structure of CuSe. The adsorbed mercury selenide exhibits even higher stability than the most stable natural mercury ore—that is, mercury sulfide—hence minimizing its environmental impact when the CuSe/ZIF-8 sorbent is dumped. This work provides a new mindset for future design of sorbents for efficient Hg 0 capture from industrial flue gas. The results also justify the candidature of CuSe/ZIF to be applicable for mercury pollution remediation in real-world conditions.

Journal article

Yang P, Tan G-YA, Aslam M, Kim J, Lee P-Het al., 2019, Metatranscriptomic evidence for classical and RuBisCO-mediated CO2 reduction to methane facilitated by direct interspecies electron transfer in a methanogenic system, SCIENTIFIC REPORTS, Vol: 9, ISSN: 2045-2322

Journal article

Zhang H, Ruan Y, Feng Y, Su M, Diao Z, Chen D, Hou L, Lee P-H, Shih K, Kong Let al., 2019, Solvent-free hydrothermal synthesis of gamma-aluminum oxide nanoparticles with selective adsorption of Congo red., J Colloid Interface Sci, Vol: 536, Pages: 180-188

Aluminum hydroxide and oxide have been widely used for decontamination due to their environmentally friendly nature and cost effectiveness. Aluminum (hydro) oxides are the main phases of aluminum-derived environment materials. Herein, the solvent-free hydrothermal synthesis of gamma-aluminum oxide (γ-Al2O3) nanoparticles and phase transformation of AlOOH into γ-Al2O3 are reported. Hydrothermal treatment of NH3·H2O-induced aluminum precipitate resulted in the formation of AlOOH, which was an intermediate product of γ-Al2O3. AlOOH was transformed into highly crystalline 20-nm γ-Al2O3 particles through calcination at 500 °C due to dehydration. The transformation was confirmed through X-ray diffraction (XRD) and thermogravimetric (TG) analyses. The resulting γ-Al2O3 had superior adsorption ability for the anionic Congo red (CR) dye than for the cationic methylene blue (MB) and malachite green (MG) dyes. The selective adsorption ability of CR instead of MB was attributed to the electrostatic attraction and hydrogen bonds between the amino group and azo double bond of CR, and between the amino group and hydroxyl group in γ-Al2O3. Thus, this study investigated crystalline phase transformation into γ-Al2O3 and selective adsorption capacity of CR, which provides important information regarding the synthesis of crystalline γ-Al2O3 adsorbent, with selective adsorption ability for decontamination applications.

Journal article

Feng Y, Qing W, Kong L, Li H, Wu D, Fan Y, Lee P-H, Shih Ket al., 2019, Factors and mechanisms that influence the reactivity of trivalent copper: A novel oxidant for selective degradation of antibiotics., Water Res, Vol: 149, Pages: 1-8

Trivalent copper complexes are active intermediates in aquatic redox reactions that involve copper ions or structural copper, but their reactivity and selectivity toward pollutants remain unknown. We characterized copper(III) periodate, a representative trivalent copper compound, with phenol and several antibiotics as model contaminants. The results show that Cu(III) is highly reactive to phenol degradation; near-complete degradation was achieved after 10 min at a molar ratio of 3:1 (Cu[III]: phenol). Common alcohols, including methanol and 2-propanol, showed pH-dependent reactivity for Cu(III). In contrast to aquo trivalent copper ions that react rapidly with tert-butanol, Cu(III) showed limited reactivity toward tert-butanol. A mechanistic investigation showed that the degradation was caused by direct oxidation by Cu(III) and that no hydroxyl radicals were involved. Common water components such as chloride ions did not influence the reaction, which suggests that the use of Cu(III) may help mitigate the generation of chlorinated products. As a one-electron oxidant, Cu(III) showed high reactivity to degrade electron-rich compounds; the concentrations of sulfamethazine, sulfamethoxazole, and sulfadiazine (100 μg/L) were reduced to 1.8, 7.5, and 42.5 ng/L, respectively, after 2 min of reaction with 10 μM Cu(III). These results demonstrate a novel and highly efficient oxidant for selective removal of ubiquitous micropollutants from water bodies.

Journal article

Wu Z, Meng H, Huang X, Wang Q, Chen W-H, Gu J-D, Lee P-Het al., 2019, Salinity-driven heterogeneity toward anammox distribution and growth kinetics., Appl Microbiol Biotechnol, Vol: 103, Pages: 1953-1960

Anaerobic ammonium oxidation (anammox) has been widely applied for biological nitrogen removal in freshwater systems, and there is a potential for its extension in saline water systems. In this study, the abundance and biodiversity of anammox bacteria were investigated in both saline and freshwater full-scale sewage treatment plants (STPs). The anammox bacteria were widely found in four tested STPs with abundance of 105-107 copies per mL of 16S rRNA gene. Phylogenetic results showed that Ca. Scalindua and Ca. Brocadia dominated in saline and freshwater STPs, respectively. Ca. Kuenenia dominated in one of freshwater STPs. However, redundancy discriminate analysis (RDA) indicates the distribution of Ca. Kuenenia in both saline and freshwater conditions. To further elucidate these observations, the Monod model was integrated with Gauss equation for the evaluation of salinity-induced kinetics. Model results reveal that when nitrite concentration (SNO2-) is higher than nitrite affinity constant (KNO2-), salinity (over ~ 3.0%) is responsible for Candidatus Scalindua dominance over Candidatus Kuenenia. Conversely, in nitrite-depleted conditions (KNO2- ≥ SNO2-), high nitrite affinity leads to the predominance of Ca. Scalindua in all salinities. This study provides fundamental insights into saline anammox applications.

Journal article

Wei S, David Stensel H, Quoc BN, Lee PH, Huang X, Winkler MKHet al., 2019, What's in your sludge? Hunting for baby granules in full-scale activated sludge treatment plants, Pages: 1318-1323

© 2019 Water Environment Federation Mixed liquor from continuous flow activated sludge (CFAS) facilities with enhanced biological phosphorus removal (EBPR) contained 0.5 to 80.2 percent granules based on 212-um sieve size. The so-called baby granules were relatively small (mostly less than 400 - 600 µm in diameter), displayed smooth morphology and dense core, resulted in lower SVI30, and had higher abundance of PAO and GAO than the floc. Higher % granules were related to anaerobic staging and more available biodegradable sCOD. This work is the first to show that granules are indeed commonly present in CFAS facilities and to observe types of systems and factors that encourage granular growth. Methods to assess granular presence in CFAS facilities have been shown.

Conference paper

Jing H, Wang Y, Lee PH, Leu SYet al., 2019, Substrate-related features to maximize bioenergy potential of chemical enhanced primary treatment sludge, Pages: 926-933, ISSN: 1876-6102

© 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of ICAE2018 - The 10th International Conference on Applied Energy. Primary treatment is a major component in modern sewage treatment systems; and chemical enhanced primary treatment (CEPT) process can further enhance its performance for energy recovery or process improvement. With significant benefits on small footprint and sludge dewaterability, CEPT process has been selected and applied as the major wastewater treatment technology in Hong Kong. CEPT sludge, similarly in composition to typical primary sludge, is rich in organic contents and therefore can serve as a proper source for bioenergy production after anaerobic digestion (AD). The heating value of CEPT sludge can be higher than that of secondary sludge, which is mainly composed of slowly degradable organics and microorganisms. If neglecting energy consumed to produce the coagulant a CEPT-AD system shall drive the wastewater treatment process from energy-negative practice to energy-neutral or even energy-positive systems. This paper demonstrates some of the most important substrate-related features to increase the bioenergy production in the CEPT-AD system. Attentions have been paid particularly on the analysis of physiochemical characteristics of the CEPT sludge and their impacts to the biological system with heterotrophic species. An innovative sulfide oxidation process was presented with experimental evidence to overcome the potential problems of sulfide induced growth inhibition of methanogens. It was expected that the new process could reduce approximately 0.744 kWh/m3 of energy consumption in comparing with conventional activated sludge process without nutrient removal.

Conference paper

Leng L, Nobu MK, Narihiro T, Yang P, Amy Tan G-Y, Lee P-Het al., 2019, Shaping microbial consortia in coupling glycerol fermentation and carboxylate chain elongation for Co-production of 1,3-propanediol and caproate: Pathways and mechanisms, Water Research, Vol: 148, Pages: 281-291, ISSN: 0043-1354

Journal article

Wang Q, Tan G-YA, Azari M, Huang X, Denecke M, Men Y, Jung J-Y, Okabe S, Ali M, Huang Y-T, Wu Z, Lo W-H, Gu J-D, Lin J-G, Lee P-Het al., 2018, Insights into the roles of anammox bacteria in post-treatment of anaerobically-treated sewage, CRITICAL REVIEWS IN ENVIRONMENTAL SCIENCE AND TECHNOLOGY, Vol: 48, Pages: 655-684, ISSN: 1064-3389

Journal article

Yang P, Leng L, Tan GYA, Dong C, Leu SY, Chen WH, Lee PHet al., 2018, Upgrading lignocellulosic ethanol for caproate production via chain elongation fermentation, International Biodeterioration and Biodegradation, Vol: 135, Pages: 103-109, ISSN: 0964-8305

© 2018 Chain elongation is a promising mixed culture bioprocess to convert acetate into medium chain carboxylates with ethanol as an electron donor. Caproate production using lignocellulosic ethanol (LE) as feedstock via chain elongation fermentation was examined in this study. Meanwhile, the effects of yeast extract and cellulose containing in the LE were investigated separately. Fermentation performance showed that the lag phase of caproate production were shortened in experimental group LE (4 days), yeast extract (6 days), and cellulose (9 days) compared with the control group (17 days) without extra supplement. The insufficiency of electron donor, ethanol, limited further elongation into caproate, resulting in comparable caproate yields and carbon conversion ratios in four experimental groups. Microbial community and microbial kinetics analysis revealed that yeast extract could be metabolized by protein-utilizing bacteria into short chain carboxylates (SCCs), which facilitated biological chain elongation. Meanwhile, yeast extract boosted microbial growth by serving as nitrogen and other nutrient sources. Furthermore, cellulose was utilized and further converted into SCCs, or even caproate, by cellulolytic bacteria. Together, caproate production was enhanced with high microbial activities and intermediates formation using LE. This study upgrades LE into a higher energy density product, caproate, via the energy-efficient chain elongation fermentation.

Journal article

Yang Z, Li H, Liu X, Li P, Yang J, Lee P-H, Shih Ket al., 2018, Promotional effect of CuO loading on the catalytic activity and SO2 resistance of MnOx/TiO2 catalyst for simultaneous NO reduction and Hg-0 oxidation, FUEL, Vol: 227, Pages: 79-88, ISSN: 0016-2361

Journal article

Feng Y, Li H, Wu D, Liao C, Fan Y, Lee P-H, Shih Ket al., 2018, Supported palladium nanoparticles as highly efficient catalysts for radical production: Support-dependent synergistic effects, CHEMOSPHERE, Vol: 207, Pages: 27-32, ISSN: 0045-6535

Journal article

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