Ji Fan

Laval University, Quebec City, Quebec, Canada

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Publications (5)10.34 Total impact

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    ABSTRACT: Based on the activated sludge model no.3 (ASM3), a new kinetic expression describing substrate removal and biomass growth mechanism occurring in activated sludge system under aerobic condition was established. The new model proposed that under feast condition, one part of substrate was utilized directly for biomass growth and the other part was stored as internal storage products and simultaneously the storage products were used for biomass growth. The model was successfully calibrated on oxygen uptake rate (OUR) data and off-line soluble chemical oxygen demand (COD) dynamic variations obtained from batch experiments with biomass from a full-scale wastewater treatment plant (WWTP). OUR predictions with the calibrated model could reasonably describe the OUR profile after pulse addition of acetate, i.e., the OUR transiently reached a very high level, and then increased gradually to a maximum level until the initial substrate was taken up for storage and biomass growth. This new model also, for the first time, highlighted the significant effect of the biomass storage products concentration before pulse addition of acetate on OUR profile.
    No preview · Article · Aug 2012 · Chemical Engineering Science
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    ABSTRACT: In order to further investigate activated sludge system for better carbon metabolism and nitrogen removal with less energy consumption, a new kinetic model was established. The detailed description of the proposed model was introduced for understanding the mechanisms involved in the activated sludge system, especially simultaneous substrate storage and biomass growth (SSSG) processes and soluble microbial product generation. The evaluation of the proposed model was demonstrated by a lab-scale sequencing batch reactor (SBR) operated with three different sets, i.e., aeration/non-aeration (set 1), non-aeration/aeration/non-aeration (set 2), and alternating aeration/non-aeration (set 3) processes. The purpose was to investigate carbon metabolism under multiple aerobic/anoxic conditions. The calibrated results showed quite an acceptable model fit to the on-line measured dissolved oxygen (DO) data for the three SBR sets. Predictions of the calibrated model were successfully confirmed using off-line analyses of soluble chemical oxygen demands (COD) and nitrogen dynamic variations, respectively. The simulated results showed that more SMP was generated under aerobic condition than that under anoxic condition, and more nitrate (S (NO)) consumption resulted in less SMP generation, i.e., approximately 7% and 57% less extra carbon source in sets 2 and 3 were required to remove 8% and 58% of S (NO), respectively, compared with set 1. And the kinetics of SSSG process in the proposed model was indirectly validated by comparisons between experimental DO profiles and simulations. Therefore, the new model provides an effective technique for better optimizing the effluent COD and nitrogen with low energy cost in biological wastewater treatment plants.
    No preview · Article · Jan 2012 · Applied Microbiology and Biotechnology
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    ABSTRACT: Soluble microbial products (SMPs) are considered as the main organic components in wastewater treatment plant effluent from biological wastewater treatment systems. To investigate and explore SMP metabolism pathway for further treatment and control, two innovative mechanistically based activated sludge models were developed by extension of activated sludge model no.3 (ASM3). One was the model by combining SMP formation and degradation (ASM3-SMP model) processes with ASM3, and the other by combining both SMP and simultaneous substrate storage and growth (SSSG) mechanisms with ASM3 (SSSG-ASM3-SMP model). The detailed schematic modification and process supplements were introduced for comprehensively understanding all the mechanisms involved in the activated sludge process. The evaluations of these two models were demonstrated by a laboratory-scale sequencing batch reactor (SBR) operated under aerated/non-aerated conditions. The simulated and measured results indicated that SMP comprised about 83% of total soluble chemical oxygen demand (SCOD) in which biomass-associated products (BAPs) were predominant compared with utilization-associated products (UAPs). It also elucidated that there should be a minimum SMP value as the reactive time increases continuously and this conclusion could be used to optimize effluent SCOD in activated sludge processes. The comparative results among ASM3, ASM3-SMP and SSSG-ASM3-SMP models and the experimental measurements (SCOD, ammonia and nitrate nitrogen) showed clearly the best agreement with SSSG-ASM3-SMP simulation values (R = 0.993), strongly suggesting that both SMP formation and degradation and SSSG mechanisms are necessary in biologically activated sludge modeling for municipal wastewater treatment.
    No preview · Article · Jul 2011 · Bioprocess and Biosystems Engineering
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    ABSTRACT: As a metabolite of lipid regulators, clofibric acid (CA) was investigated in this study for its ultraviolet (UV) degradation at monochromatic wavelength of 185 nm using Milli-Q water and sewage treatment plant (STP) effluent. The effects of CA initial concentration, solution pH, humic acid (HA), nitrate and bicarbonate anions on CA degradation performances were evaluated. All CA degradation patterns well fitted the pseudo-first-order kinetic model. The results showed that OH generated from water photolysis by UV185 irradiation was involved, resulting in indirect CA photolysis but contributed less to the whole CA removal when compared to the main direct photolysis process. Acid condition favored slightly to CA degradation and other constituents in solution, such as HA (5.0-100.0 mg L(-1)), nitrate and bicarbonate anions (1.0x10(-3) mol L(-1) and 0.1 mol L(-1)), had negative effects on CA degradation. When using real STP effluent CA degradation could reach 97.4% (without filtration) and 99.3% (with filtration) after 1 hr irradiation, showing its potential mean in pharmaceuticals removal in UV disinfection unit. Mineralization tests showed that rapid chloride ion release happened, resulting in no chlorinated intermediates accumulation, and those non-chlorinated intermediate products could further be nearly completely degraded to CO2 and H2O after 6 hrs.
    No preview · Article · Dec 2009 · Water Science & Technology
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    ABSTRACT: A modified model based on the activated sludge model no. 3 was established to simulate a full-scale municipal wastewater treatment plant in Shanghai, China. The activated sludge model no. 3 was modified to describe the simultaneous storage and growth processes occurring in activated sludge systems under aerobic and anoxic conditions. The mechanism of soluble microbial product formation and degradation by microorganisms was considered in this proposed model. Three months simulation was conducted including soluble chemical oxygen demand, NH4(+)-N, NO(X)(-)-N and T-N parameters, and compared with measured data from the Quyang wastewater treatment plant. Results indicated that the calculated effluent chemical oxygen demand and NH4(+)-N using this proposed model were in good agreement with the measured data. Results also showed that besides inert soluble organic matter contributing to the effluent chemical oxygen demand, soluble microbial products played an important part in the effluent chemical oxygen demand and, therefore, demonstrated that these products composed an important portion of effluent soluble chemical oxygen demand in wastewater treatment plants and should not be neglected.
    No preview · Article · Jul 2009 · Environmental Technology