Audrey Chai Yee Chieh
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Preferred name
Audrey Chai Yee Chieh
Official Name
Audrey, Chai Yee Chieh
Alternative Name
Chai, Audrey
Chai, A.
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Scopus Author ID
57222290582
Researcher ID
DWK-5766-2022

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  • Publication
    Effect of operating temperature in the anaerobic degradation of palm oil mill effluent: Process performance, microbial community, and biokinetic evaluation
    ( 2022-09-01)
    Audrey Chai Yee Chieh
    ;
    Wong Yee Shian
    ;
    Ong Soon An
    ;
    Nabilah Aminah Lutpi
    ;
    Sam Sung Ting
    ;
    Kee Wei Chin
    This research paper presents the thermophilic anaerobic digestion (TAD) of palm oil mill effluent (POME), which is an extension of a previously conducted mesophilic anaerobic digestion (MAD) study. An anaerobic suspended growth closed bioreactor was operated at various hydraulic retention times (HRT) between 24 and 8 days. The effect of operating temperature on the performance, microbial identification, and biokinetic coefficients was evaluated. Performance was quantified by the production of biogas and the chemical oxygen demand (COD) reduction efficiency. Biogas production in TAD (64.56 L/day) was higher than MAD (46.76 L/day). A higher COD reduction efficiency was also achieved in TAD (90.90%) compared to MAD (89.66%). Other than that, more species of methanogenic bacteria were also identified in TAD through 16S rDNA. Furthermore, the modified Monod model implemented in the biokinetic evaluation revealed that higher values of maximum substrate utilization rate (rx,max) and maximum specific biomass growth rate (μmax) contributed to the better performance in TAD. The high rx,max value explains the higher COD reduction efficiency obtained in TAD. The critical retention time (θC) in TAD is also higher than MAD, making it less prone to the washout of active microbes when operating near low retention times. Additionally, TAD also achieved higher methane yield (YCH4) as opposed to MAD. The extension study concluded that the TAD of POME demonstrated improved performance in terms of biogas production and COD reduction when evaluated against the previously conducted MAD.
      3
  • Publication
    Photocatalytic degradation of sugarcane vinasse using ZnO photocatalyst: operating parameters, kinetic studies, phytotoxicity assessments, and reusability
    ( 2021)
    Kee Wei Chin
    ;
    Wong Yee Shian
    ;
    Ong Soon An
    ;
    Nabilah Aminah Lutpi
    ;
    Sam Sung Ting
    ;
    Audrey Chai Yee Chieh
    ;
    Kim-Mun Eng
    Photocatalytic degradation performance is highly related to optimized operating parameters such as initial concentration, pH value, and catalyst dosage. In this study, the impact of various parameters on the photocatalytic degradation of anaerobi‑ cally digested vinasse (AnVE) has been determined through decolourization and chemical oxygen demand (COD) reduction efciency using zinc oxide (ZnO) photocatalyst. In this context, the application of photocatalytic degradation in treating sugarcane vinasse using ZnO is yet to be explored. The COD reduction efciency and decolourization achieved 83.40% and 99.29%, respectively, under the conditions of 250 mg/L initial COD concentration, pH 10, and 2.0 g/L catalyst dosage. The phytotoxicity assessment was also conducted to determine the toxicity of AnVE before and after treatment using mung bean (Vigna radiata). The reduction of root length and the weight of mung bean indicated that the sugarcane vinasse contains enormous amounts of organic substances that afect the plant's growth. The toxicity reduction in the AnVE solution can be proved by UV–Vis absorption spectra. Furthermore, the catalyst recovery achieved 93% in the reusability test. However, the COD reduction efciency and decolourization were reduced every cycle. It was due to the depletion of the active sites in the catalyst with the adsorption of organic molecules. Thus, it can be concluded that the photocatalytic degradation in the treatment of AnVE was efective in organic degradation, decolorization, toxicity reduction and can be reused after the recovery process.
      28  88
  • Publication
    Influence of Glucose Supplementation on the Organic Removal and Biomass Growth in Anaerobically Digested Vinasse (AnVE) by Using Aerobic Sequencing Batch Reactor (SBR)
    ( 2022-01-01)
    Kee Wei Chin
    ;
    Wong Yee Shian
    ;
    Ong Soon An
    ;
    Nabilah Aminah Lutpi
    ;
    Sam Sung Ting
    ;
    Audrey Chai Yee Chieh
    ;
    Deák G.
    This paper analyses the effect of glucose supplementation in the treatment of anaerobically digested vinasse (AnVE) through reduction performance and biomass growth by using aerobic SBR system. The result revealed that the COD and ammonium reduction with the addition of glucose supplementation (65.3 ± 6.0 and 30.0 ± 5.5%) was greater than the reactor without glucose supplementation (23.6 ± 10.8 and 18.7 ± 6.0%). This can be due to the additional glucose as the carbon source for microbe metabolism nutrients. The biomass growth in the reactor with glucose supplementation increased rapidly over time, while there was no obvious biomass growth shown in the reactor without the addition of glucose. It is because glucose supplementation increased biomass accumulation in biomass production. The increment of biomass in the reactor with glucose supplementation can be further explained by the F/M ratio and biomass yield. The F/M ratio reduced when the biomass growth increased. Thus, the biomass yield started to decrease after the operation in week 2, until it reached maximum biomass growth. Therefore, it concluded that the addition of glucose supplementation in the treatment of AnVE showed a positive effect on the removal performance and biomass growth by using aerobic SBR.
      1  4
  • Publication
    Photocatalytic Degradation of Sugarcane Vinasse Using ZnO Photocatalyst: Operating Parameters, Kinetic Studies, Phytotoxicity Assessments, and Reusability
    ( 2022-02-01)
    Kee Wei Chin
    ;
    Wong Yee Shian
    ;
    Ong Soon An
    ;
    Nabilah Aminah Lutpi
    ;
    Sam Sung Ting
    ;
    Audrey Chai Yee Chieh
    ;
    Eng K.M.
    Abstract: Photocatalytic degradation performance is highly related to optimized operating parameters such as initial concentration, pH value, and catalyst dosage. In this study, the impact of various parameters on the photocatalytic degradation of anaerobically digested vinasse (AnVE) has been determined through decolourization and chemical oxygen demand (COD) reduction efficiency using zinc oxide (ZnO) photocatalyst. In this context, the application of photocatalytic degradation in treating sugarcane vinasse using ZnO is yet to be explored. The COD reduction efficiency and decolourization achieved 83.40% and 99.29%, respectively, under the conditions of 250 mg/L initial COD concentration, pH 10, and 2.0 g/L catalyst dosage. The phytotoxicity assessment was also conducted to determine the toxicity of AnVE before and after treatment using mung bean (Vigna radiata). The reduction of root length and the weight of mung bean indicated that the sugarcane vinasse contains enormous amounts of organic substances that affect the plant's growth. The toxicity reduction in the AnVE solution can be proved by UV–Vis absorption spectra. Furthermore, the catalyst recovery achieved 93% in the reusability test. However, the COD reduction efficiency and decolourization were reduced every cycle. It was due to the depletion of the active sites in the catalyst with the adsorption of organic molecules. Thus, it can be concluded that the photocatalytic degradation in the treatment of AnVE was effective in organic degradation, decolorization, toxicity reduction and can be reused after the recovery process. Graphical abstract: [Figure not available: see fulltext.].
      1  3
  • Publication
    Kinetic model discrimination on the biogas production in thermophilic co-digestion of sugarcane vinasse and water hyacinth
    ( 2022-08-01)
    Audrey Chai Yee Chieh
    ;
    Wong Yee Shian
    ;
    Ong Soon An
    ;
    Nabilah Aminah Lutpi
    ;
    Sam Sung Ting
    ;
    Kee Wei Chin
    ;
    Eng K.M.
    Co-digestion between sugarcane vinasse (Vn) and water hyacinth (WH) at various mixing ratios of 0:1, 1:0, 1:3, 3:1, and 1:1 was carried out under thermophilic conditions (55 Â°C) for 60 days. The effect of various mixing ratios on the pH changes, soluble chemical oxygen demand (sCOD) reduction, and cumulative biogas production was investigated. The first order, modified Gompertz, and logistic function kinetic models were selected to fit the experimental data. Model discrimination was conducted through the Akaike Information Criterion (AIC). The study revealed that co-digestion shows better performance compared to the mono-digestion of both substrates. Vn:WH mixing ratio 1:1 with inoculum to substrate ratio (ISR) of 0.38 g VSinoculum/g VSsubstrate is the most favorable ratio, achieving sCOD reduction efficiency and cumulative biogas production of 71.6% and 1229 mL, respectively. Model selection through AIC revealed that ratio 1:1 was best fitted to the logistic function kinetic model (R2 = 0.9897) with Ym and K values of 1232 mL and 31 mL/day, respectively.
      2
  • Publication
    Insights into modified sequencing batch reactor for the treatment of sugarcane vinasse: role of recirculation process
    ( 2022-12-01)
    Kee Wei Chin
    ;
    Wong Yee Shian
    ;
    Ong Soon An
    ;
    Nabilah Aminah Lutpi
    ;
    Sam Sung Ting
    ;
    Audrey Chai Yee Chieh
    ;
    Ng H.H.
    The application of the recirculation process in the biological wastewater treatment process was considered as an effective approach in promoting biomass retention and mixing intensity, enhancing the performance of treating wastewater. In this study, a recirculated sequencing batch reactor (R-SBR) was developed in the treatment of anaerobically digested vinasse. The comparative study of the conventional sequencing batch reactor (without recirculation process) and R-SBR was determined through the treatment performances and kinetic studies. The chemical oxygen demand and ammonium reduction of R-SBR (52.5 ± 8.0% and 31.7 ± 7.9%) were higher than the conventional sequencing batch reactor (31.8 ± 4.3% and 17.3 ± 5.3%) at the feed flow rate of 1.0 L/day. This result revealed that the enhancement of the mass transfer between activated sludge and substrate could improve the biodegradation of the R-SBR. Moreover, the effect of feed flow rate as a significant factor to achieve effective biodegradation was determined in the R-SBR system. The maximum chemical oxygen demand reduction (63.0%) and ammonium reduction (41.3%) of R-SBR were achieved at the lowest feed flow rate (1.0 L/day) from 1.0 to 5.0 L/day. The chemical oxygen demand reduction of R-SBR could be explained by using pseudo-first-order kinetics with rate constant (k1) (0.0356 day−1). The kinetic study revealed that the R-SBR achieved the most effective performance at the lowest feed flow rate. Thus, the recirculation process as a feasible process improved the treatment performance in the R-SBR system at low feed flow rate.
      5