Papers by Keyword: Dissolved Oxygen (DO)

Abstract: The oxygen supply, propelling and mixing performance optimization conditions of a reactor are studied by adopting a pilot-scale system and a production test system for an improved Carrousel oxidation ditch, including the influence of flow velocity on the mass transfer of DO, the influence of the flow state on the denitrification and energy conservation of the oxidation ditch, and the influence of the particle sizes of floc inactivated sludge on simultaneous nitrification and denitrification (SND). The results indicate that as the flow velocity increases, the mass transfer of DO is better. The appropriate operating condition is regulated and controlled so that the denitrification efficiency of the system can be improved. The starting number of aeration wheels is reduced from 5 to 2, the particle sizes of large-ratio floc in the activated sludge are increased from 20 to 130 μm, and the removal rate of total nitrogen is improved from 44%-49% to 69%-75%.

Abstract: Dissolved oxygen transfer in an aeration pond was studied by numerical method in this paper. 2d water pond current induced by water-wheel aerators and oxygen transfer process was simulated by finite volume method. In order to verify the relationships between current and dissolved oxygen transfer, we set 4 layout styles with 4 aerators in a water pond. It is proved that different layout styles induce different flow structures and dissolved oxygen distribution. Traditional layout (style a) is not the best way for oxygen transfer, and other styles (style b, c &d) are all superior to the traditional layout. But water flow structures are not the same results. Water circulation performance is style a, c, b, d in sequence. Style c (flow to corners along pond wall) is the best way by comprehensive consideration of both water circulation performances and dissolved oxygen distribution.

Abstract: Phosphate buffer solution (PBS) was exposed for different times to static magnetic field (MF) generated from six neodymium magnet (B=250mT) at flow conditions. The PBS conductivity and DO were measured as a function of time following the application of MF. It was found that the MF increases the PBS conductivity, and decreases the DO; they all have largest effect at the flow rate of 3m/s. Besides electrochemical reasons, this maybe can explains why the MFC have good performance by exposure to MF.

Abstract: Analyzing the seasonal variation of water quality, the indices which include total iron, pH, temperature, DO, alkalinity and hardness were of high statistical significance, and total iron had a high correlation with temperature, which influences many parameters influencing iron release, such as DO, solution viscosity, thermodynamic properties and microbial activity. Therefore, it can be concluded that temperature is a main factor that affects iron release in seasonal change for drinking water distribution systems. Variation in season and temperature should be paid attention to in practice of water supply.

Abstract: The work describes the constructions of optical fiber based minimal invasive sensing system to measure pH and dissolved oxygen using sol-gel membranes which are attached internally in any transparent container. The disposable sensing membranes are very thin size and prepared as fluorescent dye doped in silica film using simple procedures. The sensor characteristics such as response time, linearity, repeatability and reversibility are evaluated and the performance of the sensor also compared with commercial meters. The experiments such as, chemical stability and photo stability are also carried out. The detection limit of pH sensor is found between 3 pH and 10 pH, however good sensitivity is obtained for the ranges from 4 pH and 9 pH with the response time of 7 seconds. Non-linear response is obtained for dissolved oxygen sensor and it is made linear by applying Stern-Volmer equation. The oxygen sensor shows good sensitivity in the ranges from 2 mg/L to 8 mg/L.

Abstract: Based on these characteristics of dissolved oxygen control in sewage treatment aeration process, such as nonlinearity, large time delay in a timely manner and difficult to model accurately, this paper puts forward an intelligent control strategy of dissolved oxygen. First, according to feed water quality parameters and environmental factors, we build a rule-based multistage fuzzy controller to make intelligent dynamic dissolved oxygen value setting. Then the feedforward tracking and constant value control are proceed, according to error source and threshold we use fuzzy tracking, fuzzy PID separation control and compound control of the major and minor loop cascade control to stabilize the given value of dissolved oxygen. The system is fast and steady which is proved by simulation and experiment results.

Abstract: The purpose of the paper is to demonstrate that the age of porous diffusers manufactured by ceramic, plastic or other porous materials declined. Following theoretical and experimental researches, the author built a new type of fine bubble generator whose nozzle plate is manufactured by spark erosion. The constructive solution of the fine bubble generator is presented; the scheme of the experimental stand developed at POLITEHNICA University of Bucharest is subsequently exposed. The final section of the paper presents the results of the experimental research, which are compared to data existing in specialty literature.

Abstract: Biological nitrification and denitrification via nitrite pathway is technically feasible and economically favorable, especially when wastewater with high ammonium concentrations or low C/N ratios is treated. Therefore, it has attracted more and more attention. It is very important to maintain partial nitrification of ammonium to nitrite. In this paper, the factors that influence operation and efficiency of nitrification and denitrification via nitrite are discussed, including DO concentration, carbon source, aeration pattern, PH, temperature and high free ammonia. High ammonia concentration and temperature are prone to accomplish of short-cut nitrification and denitrification, but limit application in practice. Finally, the review discussed the future challenges for application of short-cut nitrification and denitrification.

Abstract: The performance of adjustable head fall mixer is studied in a pilot experiment. Experimental results indicate that the dispersal efficiency increases with the space between grids and mixing pipe, which could be up to 96%. When the flow rate increases more than 31%, the dispersal efficiency decreases a little but still above 96%. It is demonstrated that special coagulant injection head makes significant contribution to improving the mixer efficiency. The almost same turbidity of sedimentation effluent could be achieved with less coagulant, thus 30% chemical can be saved. Dissolved oxygen increases 2.5 mg/L in the mixing unit, which will benefit the following processes.

Abstract: Excessive propagation of Tubifex tubifex in eutrophic source water can result in the emergence of them in the drinking water plant, which has been a troublesome problem in recent years. Our objectives were to investigate the driving force of drift and quantify the influence of temperature and DO on the worm drift. Results showed that one of the major driving forces of the worm drift was water flow, which exhibited its effect by direct shear stress on the worm or inducing sediment suspension. The worm drift rates were increased with the decrease of temperature and DO content. The results confirmed that worm drift from sediment to overlying water, which was induced by water flow and could be influenced by temperature, DO content and sediment property was the main cause of worm pollution in drinking water plant.