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Modification of the activated sludge model for chemical dosage

Frontiers of Environmental Science & Engineering 2015年第4期9卷 694-701页

作者： Shuai MA Siyu ZENG Xin DONG Jining CHEN Gustaf OLSSON State Key Joint Laboratory of Environment Simulation and Pollution Control School of Environment Tsinghua University Beijing 100084 China Department of Industrial Electrical Engineering and Automation Lund University Lund SE-22100 Sweden

Full-scale experiments have been carried out to adapt the activated sludge model ASM2d to include the influence of metal dosage （Fe^3＋ and Al^3＋） for phosphorus removal. Phosphorus removal rates, nitrification rates, as well as pH and sludge settling performance, were evaluated as functions of the metal dosages. Furthermore, models relating certain parameters to the dosage of chemicals have been derived. Corresponding parameters in the ASM2d and the secondary settler models, included in the Benchmark Simulation model No 1 （BSM1）, have been modified to take the metal influence into consideration. Based on the effluent limits and penalty policy of China, an equivalent evaluation method was derived for the total cost assessment. A large number of 300-day steady-state and 14-day open-loop dynamic simulations were performed to demonstrate the difference in behavior between the original and the modified BSM1. The results show that 1） both in low and high mole concentrations, Fe^3＋ addition results in a higher phosphorus removal rate than Al^3＋; 2） the sludge settling velocity will increase due to the metal addition; 3） the respiration rate of the activated sludge is decreased more by the dosage of Al^3＋ than Fe^3＋; 4） the inhibition of Al^3＋ on the nitrification rate is stronger than that of Fe^3＋; 5） the total operating cost will reach the minimum point for smaller dosages of Fe^3＋, but always increase with Al^3＋ addition.

关键词： activated sludge model chemical precipitation benchmark simulation model phosphorus removal,respiratory rate sludge settling

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An Adaptive Time-Step Backward Differentiation Algorithm to Solve Stiff Ordinary Differential Equations: Application to Solve activated sludge models

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American Journal of Computational Mathematics 2016年第4期6卷 298-312页

作者： Jamal Alikhani Bahareh Shoghli Ujjal Kumar Bhowmik Arash Massoudieh Department of Electrical Engineering and Computer Science The Catholic University of America Washington DC USA Department of Civil Engineering The Catholic University of America Washington DC USA Department of Civil Engineering University of North Dakota Grand Forks ND USA

A backward differentiation formula (BDF) has been shown to be an effective way to solve a system of ordinary differential equations (ODEs) that have some degree of stiffness. However, sometimes, due to high-frequency variations in the external time series of boundary conditions, a small time-step is required to solve the ODE system throughout the entire simulation period, which can lead to a high computational cost, slower response, and need for more memory resources. One possible strategy to overcome this problem is to dynamically adjust the time-step with respect to the system’s stiffness. Therefore, small time-steps can be applied when needed, and larger time-steps can be used when allowable. This paper presents a new algorithm for adjusting the dynamic time-step based on a BDF discretization method. The parameters used to dynamically adjust the size of the time-step can be optimally specified to result in a minimum computation time and reasonable accuracy for a particular case of ODEs. The proposed algorithm was applied to solve the system of ODEs obtained from an activated sludge model (ASM) for biological wastewater treatment processes. The algorithm was tested for various solver parameters, and the optimum set of three adjustable parameters that represented minimum computation time was identified. In addition, the accuracy of the algorithm was evaluated for various sets of solver parameters.

关键词： Adaptive Time-Step Backward Differentiation Formula activated sludge model Ordinary Differential Equation Stiffness Computation Time

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Cost-performance analysis of nutrient removal in a full-scale oxidation ditch process based on kinetic modeling

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Journal of Environmental Sciences 2013年第1期25卷 26-32页

作者： Zheng Li Rong Qi Bo Wang Zhe Zou Guohong Wei Min Yang State Key Laboratory of Environmental Aquatic Chemistry Research Center for Eco-Environmental SciencesChinese Academy of Sciences Beijing Urban Construction Environmental Protection Investment & Development Co. Ltd.

A full-scale oxidation ditch process for treating sewage was simulated with the ASM2d model and optimized for minimal cost with acceptable performance in terms of ammonium and phosphorus removal. A unified index was introduced by integrating operational costs （aeration energy and sludge production） with effluent violations for performance evaluation. Scenario analysis showed that, in comparison with the baseline （all of the 9 aerators activated）, the strategy of activating 5 aerators could save aeration energy significantly with an ammonium violation below 10%. sludge discharge scenario analysis showed that a sludge discharge flow of 250- 300 ma/day （solid retention time （SRT）, 13-15 days） was appropriate for the enhancement of phosphorus removal without excessive sludge production. The proposed optimal control strategy was： activating 5 rotating disks operated with a mode of ＂111100100＂（＂1＂ represents activation and ＂0＂ represents inactivation） for aeration and sludge discharge flow of 200 m3/day （SRT, 19 days）. Compared with the baseline, this strategy could achieve ammonium violation below 10% and TP violation below 30% with substantial reduction of aeration energy cost （46%） and minimal increment of sludge production （〈 2%）. This study provides a useful approach for the optimization of process operation and control.

关键词： activated sludge model cost-performance analysis oxidation ditch nutrient removal

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Comparison of conventional and inverted A^2/O processes:Phosphorus release and uptake behaviors

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Journal of Environmental Sciences 2012年第4期24卷 571-578页

作者： Rong Qi Tao Yu Zheng Li Dong Li Takashi Mino Tadashi Shoji Kochi Fujie Min Yang State Key Laboratory of Environmental Aquatic Chemistry Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China Department of Socio-Cultural Environmental Studies Graduate School of Frontier SciencesThe University of TokyoKashiwaJapan Graduate School of Environment and Information Sciences Yokohama National UniversityYokohamaKanagawa 240-850Japan

Two full-scale systems operated in parallel, a conventional A2/O system consisting of anaerobic, anoxic and oxic compartments in succession and an inverted system consisting of anoxic, anaerobic and oxic compartments without internal recycle, were compared in terms of their phosphorus removal performance, with an emphasis on phosphate （P） release behaviors, using both operational data and simulation results. The inverted system exhibited better long-term phosphorus removal performance （0.2 ± 0.3 vs. 0.7 ±0.7 mg/L）, which should be attributed to the higher P release rate （0.79 vs. 0.60 kg P/（kg ***）） in the non-aerated compartments. The P release occurred in both the anoxic and anaerobic compartments of the inverted system, resulting in more efficient P release. Although the abundances of the ＇Candidatus Accumulibacter phosphatis＇ population in the two systems were quite similar （（19.1 ＋ 3.27）% and （18.4 ＋ 4.15）% of the total microbe （DAPI stained particles） population in the inverted and conventional systems, respectively, by fluorescence in situ hybridization （FISH））, the high-concentration DAPI staining results show that the abundances of the whole polyphosphate accumulating organisms （PAOs） in the aerobic ends were quite different （the average ratios of the poly-P granules to total microbes （DAPI stained particles） were （45 ±4.18）% and （35 ± 5.39）%, respectively）. Both the operational data and simulation results showed that the inverted system retained more abundant PAO populations due to its special configuration, which permitted efficient P release in the non-aerated compartment and better P removal,

关键词： phosphate release and uptake A2/O process inverted A2/O process activated sludge model

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Simulation of long-term nutrient removal in a full-scale closed-loop bioreactor for sewage treatment： an example of Bayesian inference

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Frontiers of Environmental Science & Engineering 2015年第3期9卷 534-544页

作者： Zheng LI Rong QI Wei AN Takashi MINO Tadashi SHOJI Willy VERSTRAETE Jian GU Shengtao LI Shiwei XU Min YANG State Key Laboratory of Environmental Aquatic Chemistry Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100086 China Socio-Cultural Environmental Studies the University of Tokyo Kashiwa City 277-8563 Japan Environmental Science Research Laboratory Central Research Institute of Electric Power Industry Chiba 270-1194 Japan Laboratory of Microbial Ecology and Technology (LabMET) Ghent University Gent 9000 Belgium Beijing Drainage Group Co. Ltd Beijing 100044 China

In this study, the performance of nitrogen and phosphorus removal in a full-scale closed-loop bioreactor （oxidation ditch） system was simulated using the ASM2d model. Routine data describing the process for two years were compiled for calibration and validation. To overcome the identifiability problem, the classic Bayesian inference approach was utilized for parameter estimation. The calibrated model could describe the long-term trend of nutrient removal and short-term variations of the process performance, showing that the Bayesian method was a reliable and useful tool for the parameter estimation of the activated sludge models. The anoxic phosphate uptake by polyphosphate accumulating organisms （PAO） contributed 71.2% of the total Poly-P storage, which reveals the dominance of denitrifying phosphorus removal process under the oxygen limiting conditions. It was found that 58.7% of the anoxic Poly-P storage and denitrification by PAO in the reactor was achieved in the aerated compartment, implying that the PAO＇s anoxic activity was significantly stimulated by the low dissolved oxygen （DO） level in this compartment due to the oxygen gradient caused by brush aerator.

关键词： activated sludge model Bayesian inference biological nutrient removal closed-loop bioreactor oxidation ditch denitrifying polyphosphate accumulating organisms

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