Ho Li Ngee
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Preferred name
Ho Li Ngee
Official Name
Ho, Li Ngee
Alternative Name
Li Ngee, Ho
Ho, Li Ngee
Ngee, Ho Li
Ho, L. N.
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Scopus Author ID
57219028372
Researcher ID
DDY-6348-2022

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Transformation from biofiltration unit to hybrid constructed wetland-microbial fuel cell: Improvement of wastewater treatment performance and energy recovery

2023-05-01 , Teoh T.P. , Koo C.J. , Ho Li Ngee , Wong Yee Shian , Nabilah Aminah Lutpi , Tan S.M. , Yap K.L. , Ong Soon An

This study aimed to compare the performance of biofiltration, constructed wetland, and constructed wetland microbial fuel cell (CW-MFC). The transformation from a biofiltration unit to a hybrid CW-MFC was demonstrated with the advantages of improvement of wastewater treatment while generating electricity simultaneously. The introduction of plants to the upper region of the bioreactor enhanced the DO level by 0.8 mg/L, ammonium removal by 5 %, and COD removal by 1 %. The integration of electrodes and external circuits stimulated the degradation rate of organic matter in the anodic region (1 % without aeration and 3 % with aeration) and produced 5.13 mW/m3 of maximum power density. Artificial aeration improved the nitrification efficiency by 38 % and further removed the residual COD to an efficiency of 99 %. The maximum power density was also increased by 3.2 times (16.71 mW/m3) with the aid of aeration. In treating higher organic loading wastewater (3M), the maximum power density showed a significant increment to 78.01 mW/m3 (4.6-fold) and the COD removal efficiency was 98 %. The ohmic overpotential dominated the proportion of total loss (67-91 %), which could be ascribed to the low ionic conductivity. The reduction in activation and concentration loss contributed to the lower internal resistance with the additional aeration and higher organic loading. Overall, the transformation from biofiltration to a hybrid CW-MFC system is worthwhile since the systems quite resemble while CW-MFC could improve the wastewater treatment as well as recover energy from the treated wastewater.

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Caffeine-containing wastewater treatment and bioelectricity generation in up-flow constructed wetland-microbial fuel cell: Influence of caffeine concentration, operating conditions, toxicity assessment, and degradation pathway

2022-04-01 , Teoh T.P. , Ong Soon An , Ho Li Ngee , Wong Yee Shian , Nabilah Aminah Lutpi , Oon Y.L. , Tan S.M. , Ong Y.P. , Yap K.L.

This study explored the potential of caffeine being utilized as the fuel for the microbes to produce electrons for electricity generation in up-flow constructed wetland-microbial fuel cell (UFCW-MFC). The effect of caffeine concentration was investigated to identify the availability of UFCW-MFC in the conversion of caffeine to electrons for electricity production; and the effect of operating conditions (circuit connection, supplementary aeration, and plant) was studied to determine their significance in the treatment of caffeine containing wastewater. The UFCW-MFC achieved about 98% of decaffeination efficiency regardless of caffeine concentration; while a decrease of efficiency was observed when UFCW-MFC operated without supplementary aeration and plant (~93%). COD removal efficiency decreased correspondingly to the increase of caffeine concentration, which could be contributed by the higher concentration of caffeine and its intermediates. The degradation pathway of caffeine in UFCW-MFC was explored in this study. It was remarkable that ammonia was produced and converted to ammonium ions during caffeine catabolism. Supplementary aeration and macrophyte play a crucial role in removing excess caffeine, intermediates as well as accumulated ammonium ions. The toxicity assessment revealed that caffeine was degraded to less toxic products. The closed circuit connection not only contributed to electricity generation but also enhanced the caffeine and COD removal efficiency by 4.6 and 5.4% in the anaerobic region, respectively. The increase of voltage and maximum power density from phase I to phase IV indicated that caffeine could be converted to electrons by the anaerobes for electricity production.

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Feasibility of UVA photocatalytic post-treatment of molasses wastewater: Effects on melanoidins removal, mineralization and oxidation of ammoniacal-nitrogen

2024-02-01 , Khalik W.F. , Ho Li Ngee , Ong Soon An , Thor S.H. , Yap K.L.

The brown color of molasses wastewater is due to the presence of melanoidins which are toxic to human health and environment. In this study, combination of coagulation-flocculation process with UVA-photocatalytic degradation of raw and diluted molasses wastewater in the presence of zinc oxide (ZnO) and titanium dioxide (TiO2) as photocatalyst was investigated. The effect of various operating parameters, such as light irradiation, aeration, catalyst dosage and pH of molasses wastewater on the photocatalytic degradation process was examined. The pre-treated diluted molasses wastewater (2 DF) showed greater performance compared to pre-treated raw for both photocatalysts due to high penetration of light into the wastewater. The formation of •OH enhanced color intensity reduction rate of pre-treated raw and 2 DF molasses wastewater in the presence of light irradiation and aeration. The color removal efficiency of pre-treated raw and 2 DF molasses wastewater was better in alkaline medium (pH 10) when ZnO used as photocatalyst, meanwhile it achieved higher removal efficiency in acidic medium (pH 4) when TiO2 was used as photocatalyst. The mineralization and oxidation of ammoniacal-nitrogen of molasses wastewater showed enhanced performance in photocatalytic treatment.

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Microbial fuel cell for simultaneous caffeine removal and bioelectricity generation under various operational conditions in the anodic and cathodic chambers

2022-02-01 , Yap K.L. , Ho Li Ngee , Ong Soon An , Guo K. , Liew Y.M. , Oon Y.S. , Thor S.H. , Tan S.M. , Teoh T.P.

A series of studies of the effects of operational parameters including organic substrate loading concentration, initial caffeine concentration, circuit connection, external resistance and salinity were carried out to evaluate the optimal performance of a double chambered microbial fuel cell for the treatment of caffeine. The increment of organic substrate loading concentration at anode increased the maximum power density from 7.84 ± 0.59 to 14.18 ± 0.87 mW m−2 but deteriorated the removal efficiency of caffeine in which only half of the removal efficiency of caffeine attained at 72 h at 1.500 g L−1 acetate (46.28 ± 3.66 %) than that of 0.375 g L−1 (96.89 ± 0.48 %). Initial caffeine concentration of 20 mg L−1 (95.31 ± 1.83 %) achieved 2.40-fold higher removal efficiency of caffeine than that of 50 mg L−1 (39.58 ± 2.83 %) at 48 h as saturated caffeine molecules hindered the oxygen reduction reaction and thus, fewer hydroxyl radicals were produced for the decomposition of caffeine. An optimal external resistance of 1000 Ω exhibited the best performance in terms of pollutants removal efficiency and power generation than that of 500 and 5000 Ω. Sodium chloride concentration of 0.580 g L−1 produced the highest maximum power density of 11.78 ± 0.68 but reduced to 8.26 ± 0.41 mW m−2 at 0.696 g L−1 as high concentration of sodium ions caused dehydration of anodophilic cells which decreased the electron transfer ability of electrochemically active bacteria.

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Comparative study of dihydroxybenzene isomers degradation and bioelectricity generation using CuO as cathodic catalyst in double chambered microbial fuel cell

2022-10-01 , Yap K.L. , Ho Li Ngee , Ong Soon An , Guo K. , Liew Y.M. , Thor S.H. , Tan S.M. , Teoh T.P.

A double chambered microbial fuel cell (MFC) showed enormous capacity in the simultaneous degradation of synthetic wastewater and dihydroxybenzene isomers (catechol, resorcinol and hydroquinone) and concurrently with bioelectricity generation. Operating parameter such as effect of catalyst on MFC system was evaluated using bare carbon plate and copper (II) oxide (CuO) loaded carbon plate as cathodes, respectively, in terms of chemical oxygen demand (COD) and dihydroxybenzene isomers removal efficiency, maximum voltage output and power density. Results revealed that the application of CuO loaded carbon plate was more effective in the COD removal of synthetic wastewater in the anodic chamber and degradation of dihydroxybenzene isomers in the cathodic chamber. Compared with the bare carbon plate as cathode, the COD removal efficiency of synthetic wastewater, removal rate of dihydroxybenzene isomers and maximum voltage output increased 20, 100 and 31 %, respectively, when CuO was applied as cathodic catalyst. Among the dihydroxybenzene isomers, hydroquinone exhibited the best performance in both absence and presence of catalyst in the MFC. The position of the substituent of hydroxyl groups possessed significant effect on the reaction rate, reactivity and conductivity of dihydroxybenzene isomers. Hydroquinone was more susceptible to be degraded than that of catechol and resorcinol due to its lower dipole moment which eased the bond cleavage. The intermediate products of degradation of catechol, resorcinol and hydroquinone were determined using gas chromatograph-mass spectrometer and the degradation pathways were proposed.

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Converting synthetic azo dye and real textile wastewater into clean energy by using synthesized CuO/C as photocathode in dual-photoelectrode photocatalytic fuel cell

2023-04-01 , Khalik W.F. , Ho Li Ngee , Ong Soon An , Lai N.B. , Thor S.H. , Yap K.L.

Cathode in photocatalytic fuel cell (PFC) plays a crucial role in degradation of organic contaminants. In this study, synthesized copper oxide (CuO) was loaded on carbon plate and used as photocathode in PFC for degradation of synthetic azo dye Reactive Black 5 (RB5) and real textile wastewater. Morphology and structural phase of the synthesized CuO were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Several operating parameters had been investigated such as light irradiation, initial dye concentration, and pH of azo dye solution within 6 h of irradiation time. The lowest initial concentration of RB5 (10 mg L−1) achieved 100% color removal compared to the highest initial concentration (40 mg L−1) which only achieved 77.1% color removal within 6 h of irradiation time. The influence of external resistance was significant in electricity generation but trivial in dye degradation efficiency. The external resistance of 6000 Ω yielded highest maximum power density, with Pmax of 0.2631 Î¼W cm−2, followed by 1000 Ω (0.2196 Î¼W cm−2) and 8000 Ω (0.1587 Î¼W cm−2), respectively. The real textile wastewater with dilution ratio (DR) 1:6 yielded the highest energy conversion efficiency, η (3.62%), followed by DR 1:4 (3.19%) and DR 1:2 (1.96%), respectively.

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Primary insights into the effects of organic pollutants and carbon-based cathode materials in a double chambered microbial fuel cell integrated electrocatalytic process

2021-12-01 , Yap K.L. , Ho Li Ngee , Ong Soon An , Guo K. , Liew Yun Ming , Oon Y.S. , Thor S.H. , Tan S.M. , Teoh T.P.

Cathode plays an important role on the oxygen reduction reaction (ORR) reactivity in the microbial fuel cell integrated electrocatalytic process for the effective degradation of organic pollutants. Comparative study of caffeine and phenol as the organic pollutants in the cathodic chamber was investigated in terms of removal efficiency and bioelectricity generation. Results revealed that the highest removal efficiency of phenol (96.89 ± 1.26%) and maximum power density (33.37 ± 4.62 mW m−2) were attained by copper (II) oxide loaded carbon felt (CuO/CF) cathode. Besides, the removal efficiency of phenol was nearly 12-fold higher (24.85 ± 1.36%) using CuO/CF cathode compared with that of caffeine (2.14 ± 0.36%) at the first 24 h. The effect of carbon-based cathode materials on the mineralization of caffeine in the cathodic chamber was evaluated using carbon felt (CF) and carbon plate (CP). Both CuO/CP and bare CP cathodes surpassed CuO/CF and bare CF cathodes in the chemical oxygen demand (COD) removal and bioelectricity generation. Higher crystallinity nature and electrical conductivity (3.57 × 105 Ω−1 m−1) of CP compared with that of amorphous structure and lower electrical conductivity of bare CF (3.33 × 104 Ω−1 m−1) contributed to higher ORR reactivity and efficient transport of electrons for bioelectricity generation. The COD removal efficiency of synthetic wastewater in the anodic chamber and bioelectricity generation of this integrated system were affected by the types of organic pollutants and carbon-based cathode materials in the cathodic chamber.

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Crucial roles of aeration and catalyst on caffeine removal and bioelectricity generation in a double chambered microbial fuel cell integrated electrocatalytic process

2021-02-01 , Yap K.L. , Ho Li Ngee , Ong Soon An , Guo K. , Oon Y.S. , Ong Y.P. , Thor S.H.

The effects of aeration and catalyst on caffeine removal in the cathodic chamber and electricity generation of a double chambered microbial fuel cell (MFC) integrated electrocatalytic process were investigated. The overall performances of MFC in caffeine removal and electricity generation were significantly enhanced under the presence of copper (II) oxide (CuO) and aeration. CuO was synthesized using a hydrothermal method and was immobilized on the carbon plate for application as cathode. The CuO particles and CuO loaded carbon plate (CuO/C) were characterized by using X-ray diffractometer and scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy. The effective transfer of electrons from anodic chamber to cathodic chamber for oxygen reduction reaction (ORR) accelerated the removal of caffeine using CuO/C cathode under aerated condition. Results revealed that 15-fold higher removal efficiency of caffeine was obtained using CuO/C cathode (52.16 %) as compared with that of bare carbon plate (bare C) (3.41 %) at the first 24 h under aerated condition. The highest maximum power density and current density (28.75 mW m-2 and 253.33 mA m-2) were obtained for CuO/C cathode under aerated condition. Bare C cathode possessed the lowest maximum power density and current density (9.75 mW m-2 and 106.67 mA m-2) under unaerated condition. The circuit connection greatly improved the chemical oxygen demand removal of synthetic wastewater in the anodic chamber when the cathodic chamber was under aerated condition. The detailed mechanisms of the effects of CuO catalyst and aeration on the ORR at cathodic chamber were discussed.

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Insights into the decolorization of mono and diazo dyes in single and binary dyes containing wastewater and electricity generation in up-flow constructed wetland coupled microbial fuel cell

2023-02-01 , Teoh T.P. , Ong Soon An , Ho Li Ngee , Wong Yee Shian , Nabilah Aminah Lutpi , Oon Y.L. , Tan S.M. , Ong Y.P. , Yap K.L.

The treatment of single and binary azo dyes, as well as the effect of the circuit connection, aeration, and plant on the performance of UFCW-MFC, were explored in this study. The decolorization efficiency of Remazol Yellow FG (RY) (single dye: 98.2 %; binary dye: 92.3 %) was higher than Reactive Black 5 (RB5) (single: 92.3 %; binary: 86.7 %), which could be due to monoazo dye (RY) requiring fewer electrons to break the azo bond compared to the diazo dye (RB5). In contrast, the higher decolorization rate of RB5 in binary dye indicated the removal rate was affected by the electron-withdrawing groups in the dye structure. The closed circuit enhanced about 2% of color and 4% of COD removal. Aeration improved the COD removal by 6%, which could be contributed by the mineralization of intermediates. The toxicity of azo dyes was reduced by 11–26% and the degradation pathways were proposed. The dye removal by the plants was increased with a higher contact time. RB5 was more favorable to be uptook by the plant as RB5 holds a higher partial positive charge. 127.39 (RY), 125.82 (RB5), and 58.66 mW/m3 (binary) of maximum power density were generated. The lower power production in treating the binary dye could be due to more electrons being utilized for the degradation of higher dye concentration. Overall, the UFCW-MFC operated in a closed circuit, aerated, and planted conditions achieved the optimum performance in treating binary azo dyes containing wastewater (dye: 87–92%; COD: 91%) compared to the other conditions (dye: 83–92%; COD: 78–87%).

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Enhancement of energy recovery from caffeine wastewater in constructed wetland-microbial fuel cell through operating conditions

2023-01-01 , Teoh T.P. , Ong Soon An , Ho Li Ngee , Wong Yee Shian , Nabilah Aminah Lutpi , Tan S.M. , Ong Y.P. , Yap K.L.

The enhancement of up-flow constructed wetland-microbial fuel cell (UFCW-MFC) performance in energy retrieval from caffeine containing wastewater has been explored via various operating conditions (hydraulic retention time (HRT), multianode (MA), multicathode current collector (MC), external resistance). The anaerobic decaffeination and COD removal improved by 37 and 12% as the HRT extended from 1 to 5 d. The increment in contact time between the microbes and organic substrates promoted the degradation and contributed to higher power output (3.4-fold), CE (eightfold), and NER (14–16-fold). The MA and MC connections facilitated the electron transfer rate and the degradation rate of organic substrates in the multiple anodic zones, which enhanced the removal efficiency in the anaerobic compartment (Caffeine: 4.2%; COD: 7.4%) and led to higher electricity generation (Power: 4.7-fold) and energy recovery (CE: 1.4-fold; NER: 2.3–2.5-fold) compared to SA. The lower external resistance favored the growth of electrogens and induced higher electron flux, where the best treatment performance and electricity production was obtained when the external resistance approached the internal resistance. Overall, it was noteworthy that the optimum operating conditions were achieved with 5 d HRT, MA, and MC connection along with external resistance of 200 Ω, which significantly outperformed the initial conditions (1 d HRT, SA connection, and 1000 Ω) by 43.7 and 29.8% of caffeine and COD removal in the anaerobic compartment, respectively as well as 14-fold of power generation.

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