Biomedical subjects

Yong-Zhen Peng

Publications and source records attributed to Yong-Zhen Peng.

10 recordsLinked to original sources

PubMed2005

[Stability of shortcut nitrification-denitrification].

The effects of temperature and aeration time on the stability of shortcut nitrification-denitrification are studied specially in some experiments are carried on a sequencing batch reactor (SBR) fed with soybean wastewater. Results show that shortcut nitrification-denitrification achieved by controlling temperature was not stable until the temperature was more than 28 degrees C. In addition, for the first time strong effect of excess aeration on shortcut nitrification-denitrification is observed. When the system run under excess aeration for twelve days, the type of nitrification turned from shortcut nitrification which nitrosation rate (NO2(-)-N/NOx(-) -N) was more than 96% to complete nitrification which nitrosation rate (NO2(-) -N/NOx(-) -N) was less than 39.3%. So, in order to make shortcut nitrification-denitrification run stably, real-time process control must be used.

Bioreactors↗

PubMed2005

Study of control strategy and simulation in anoxic-oxic nitrogen removal process.

The control strategy and simulation of external carbon addition were specially studied in an anoxic-oxic (A/O) process with low carbon: nitrogen (C/N) domestic wastewater. The control strategy aimed to adjust the flow rate of external carbon dosage to the anoxic zone, thus the concentration of nitrate plus nitrite (NOx(-) -N) in the anoxic zone was kept closed to the set point. The relationship was studied between the NOx(-) -N concentration in the anoxic zone (S(NO)) and the dosage of external carbon, and the results showed that the removal efficiency of the total nitrogen (TN) could not be largely improved by double dosage of carbon source when S(NO) reached about 2 mg/L. Through keeping S(NO) at the level of about 2 mg/L, the demand of effluent quality could be met and the carbon dosage could be optimized. Based on the Activated Sludge Model No. 1 (ASM No. 1), a simplified mathematical model of external carbon dosage was developed. Simulation results showed that PI controller and feed-forward PI controller both had good dynamic response and steady precision. And feed-forward PI controller had better control effects due to its consideration of influent disturbances.

Bioreactors↗

PubMed2005

Automatic control strategy for step feed anoxic/aerobic biological nitrogen removal process.

Control of sludge age and mixed liquid suspended solids concentration in the activated sludge process is critical for ensuring effective wastewater treatment. A nonlinear dynamic model for a step-feed activated sludge process was developed in this study. The system is based on the control of the sludge age and mixed liquor suspended solids in the aerator of last stage by adjusting the sludge recycle and wastage flow rates respectively. The simulation results showed that the sludge age remained nearly constant at a value of 16 d in the variation of the influent characteristics. The mixed liquor suspended solids in the aerator of last stage were also maintained to a desired value of 2500 g/m3 by adjusting wastage flow rates.

Bioreactors↗

PubMed2005

[Experiment study on real-time controlling rules of A/O nitrogen removal process].

The aim of this work is operational optimization of an A/O process in the lab plant with synthetic wastewater for improving nitrogen removal efficiency. Ammonia control aims at maintaining the required concentration of ammonia in the effluent by manipulating the dissolved oxygen (DO) set point and aeration volumes. Nitrate control aims at the optimal use of the denitrification potential at any moment by continuously adjusting the internal recirculation flow or (and) external carbon addition flow in order to maintain a desired nitrate set point in the anoxic zone. The control strategies have been based on a hierarchical structure where a high level or supervisory control selects the set point of the low level or conventional controllers. Results indicated that it was possible to increase nitrogen removal efficiency, improve the effluent water quality, save energy, and reduce operating costs.

Ammonia↗

PubMed2004

Denitrifying phosphorus removal in a continuously-flow A2N two-sludge process.

The Anaerobic-Anoxic/Nitrification (A2N) system is a continuous-flow, two-sludge process in which Poly-p bacteria are capable of taking up phosphate under anoxic conditions using nitrate as an electron acceptor. The process is very efficient because it maximizes the utilization of organic substrate for phosphorus and nitrogen removal. Further, the process solves the competition for organic substrate among Poly-p organisms and denitrifies as well as the problem of overgrowing of slow nitrifiers by fast organotrophs. An experimental lab-scale A2N system fed with domestic sewage was tested over a period of 260 days. The purpose of the experiment was to examine phosphorus removal capacity of a modified A2N two-sludge system. Factors affecting phosphorus and nitrogen removal by the A2N system were investigated. These factors were the influent COD TN ratio. Sludge Retention Time (SRT), Bypass Sludgy Flow rate (BSF), and Return Sludge Flow rate (RSF). Results indicated that optimum conditions for phosphorus and nitrogen removal were the influent COD/TN ratio around 6.49, the SRT of 14 days, and the BSF and RSF were fixed about 26%-33% of inffuent flow rate.

Bacteria↗

PubMed2004

Nitrogen removal influence factors in A/O process and decision trees for nitrification/denitrification system.

In order to improve nitrogen removal in anoxic/oxic(A/O) process effectively for treating domestic wastewaters, the influence factors, DO(dissolved oxygen), nitrate recirculation, sludge recycle, SRT(solids residence time), influent COD/TN and HRT(hydraulic retention time) were studied. Results indicated that it was possible to increase nitrogen removal by using corresponding control strategies, such as, adjusting the DO set point according to effluent ammonia concentration; manipulating nitrate recirculation flow according to nitrate concentration at the end of anoxic zone. Based on the experiments results, a knowledge-based approach for supervision of the nitrogen removal problems was considered, and decision trees for diagnosing nitrification and denitrification problems were built and successfully applied to A/O process.

Decision Trees↗

PubMed2003

Nitrogen removal via nitrite at normal temperature in A/O process.

In order to study the nitrogen removal via nitrite at normal temperature in anoxic/oxic (A/O) process for treating domestic wastewater, the influence of pH, free ammonia (FA), dissolved oxygen (DO), and hydraulic retention time (HRT) were studied. Results indicated that it was possible to remove nitrogen via nitrite in A/O process, if the temperature was between 18 and 25 degrees C and pH was below 7.5. Even if FA was as low as 0.06 mg NH3-N/L, it would inhibit the nitrobacteria. However, FA could not be the sole factor. Whether denitrification went thoroughly or not could affect the nitrification pathway. If denitrification went well, nitrite accumulation could recover in a short while. Nitritification lagged nitratification, so that short HRT would help nitrite accumulation. On the other hand, extended aeration would reduce nitrite accumulation.

Nitrites↗

PubMed2003

Using oxidation-reduction potential (ORP) and pH value for process control of shortcut nitrification-denitrification.

A new low cost technology for simultaneous carbon-nitrogen removal from soybean wastewater has been developed in this study. The technology is performed through shortcut nitrification-denitrification. The process operated under realtime control of aeration and mixing time. The shortcut nitrification-denitrification in sequencing batch reactor (SBR) was achieved efficiently and steadily by controlling temperature (28 +/- 0.5 degrees C) and using real-time control strategies. This enabled the prevention of nitrite oxidation, leading to lower operational costs. The feasibility of oxidation-reduction potential (ORP) and pH value as control parameter for shortcut nitrification-denitrification process was also investigated. Results showed that the average removal efficiency of ammonium was more than 95%, and nitrosation rate (NO2(-)-N/NOx(-)-N) was reached to 96%. At the same time, the variation of oxidation--reduction potential (ORP) and pH value was well related to organic matter degradation and ammonium oxidation in SBR. So that judgment on the ending of nitrification and denitrification can be based on the inflection point on the varied curve of ORP and pH throughout each SBR processing cycle, and thus reducing aeration and mixing time for saving energy source. The method saves organic energy up to 40% of chemical oxygen demand (COD) in denitrification process, which should reduce the need for an extra external source of organic carbon. Shorter hydraulic retention time should allow the volume of the reactors to diminish, and thus diminish investment costs. Lower oxygen demand of about 25% gives lower exploitation costs.

Agriculture↗

PubMed2003

A study on prediction of the bio-toxicity of substituted benzene based on artificial neural network.

Quantitative Structure-Activity Relationship (QSAR) between the bio-toxicity of seventy-eight kinds of substituted benzene chemicals to yeast Saccharomyces cerevisiae (1g(1/Cmiz)) and the components of vertex degree autocorrelation vectors (values of A, B, C and D) was studied by using the software of Artificial Neural Network (ANN). The key factors of the autocorrelation descriptors for the 1g (1/Cmiz) value of yeast Saccharomyces cerevisiae, A [0], A [1], C [3], C [5] and D [3] were selected from twenty-four descriptors, and were explained theoretically in this paper. The QSAR-ANN model has been used to predict the bio-toxicity of twenty-three substituted benzene chemicals. The correlation between Cmiz and LC50 was also discussed, and the liner correlation equation between them was established.

Benzene↗

PubMed2002

Study on the screening of molecular structure parameter in QSAR model.

Based on the analysis of information flow through the Artificial Neural Network (ANN), a new screening rule of the molecular structure parameter in Quantitative Structure-Activity Relationship (QSAR) was presented by comparing of the values of connection weights and biases of the ANN model. The result showed that model quality and prediction ability of QSAR model, which was constructed by screening structural parameter with ANN, were better than by the method with MLR. The method established the foundation for further study in the mechanism research of the bio-toxicity of organic chemicals.

Animals↗