致 谢
这次毕业设计，我认真细致地对各构筑物进行了设计，对每个构筑物由陌生到比较熟悉，从中学到了很多知识。同时我体会到实际与理论之间的确存在不少差异，以及许多理论上的变形。
通过这次毕业设计，我提高了自己独立分析解决问题的能力，掌握了净水厂的基本流程设计的步骤，要求，原则等，为以后的学习与工作奠定了基础。
由于知识水平所限，净水厂设计仍然存在许多不足，但是整个设计过程是自己独立完成，也算作是对大学四年学习的一个总结。在设计过程中得到了曹昉老师认真细致的指导。在此，特向老师表示衷心的感谢。
英文文献:
Oxidize the ditch craft in dirty water handle of
application and development
Summary: This text expatiated primarily the Carrousel oxidizes the construction, craft mechanism of the ditch and circulate the problem exsited in the process with the homologous the method of solution.Finally, introduce the Carrousel oxidize the latest research progress of the ditch and pointed out the future and main research direction.
Key phrase: The Carrousel oxidizes the ditch divideds by the phosphor takes off the nitrogen construction mechanism
Application and Development of Carrousel Oxidation Ditch Process on Wastewater Treatment
Key words: Carrousel; oxidation ditch; nitrogen and phosphor removal; structure;techniques
1. Foreword
The oxidation ditch —a continuous circulation spirit pond( Continuous loop reactor), is a kind of activated sludges. The oxidation ditch wastewater treatment technology was developed successfully in the 1950 by Dutch Health Engineering Research Institute. Since it was first put into use in the Netherlands in 1954,because of the good treatment effluent, stable operation , convenient management and so on,it has been widely applied in sewage and industrial wastewater treatment at home and abroad.
Currently applied widely oxidation ditch types include:The Pasveer oxidation ditch、 the Carrousel oxidation ditch、Orbal oxidation ditch、the type of T oxidation ditch（the type of three ditchs)、the type of DE oxidation ditch and the integral whole oxidation ditch.These oxidation ditch, because of the difference of esse in construction with circulating, therefore they have each characteristic.This text will introduce the construction, mechanism, existent problem and latest developments of Carrousel oxidize ditches primarily.
2. The construction of the Carrousel oxidation ditch
The Carrousel oxidation ditch is developed to manufacture by Dutch DHV company in 1967. on the basis of the original Carrousel oxidation ditch,the company of DHV and another company of its in the USA invent the system of Carrousel 2000(see chart 1),realizing the higher requirement of the function of biological nitrogen and phosphorus removal.And now,there are more than 850 Carrousel oxidation ditch and Carrousel 2000 system being running in the world.
The figure below shows: Carrousel oxidation ditch use orientation control aeration and stirring apparatus, to intermixture transmission level speed, thus causes the intermixture which mixes to be mobile in the oxidation ditch closed channel internal recycling. Therefore the oxidation ditch has the special hydraulics fluid state, both has the complete mixed style reactor's characteristic, and has the drift type reactor's characteristic.In the ditch has the obvious dissolved oxygen concentration gradient. The oxidation ditch cross section is the rectangle or the trapezoid. The planform many are the ellipse. In the ditch, the water depth is 2.5~4.5m generally. The wide depth compared to it is 2:1, it also has the water depth to reach 7m, and the fluent average velocity is 0.3m/s. The oxidation ditch aeration mixing device has the superficial insolation internal combustion engine, the aeration extension to brush or the turntable, the jet flow aeration, the drive pipe type aeration and the promotion tubular insolation internal combustion engine and so on, in recent years coordinated
the use also to have submarine driver unit.
Figure 1： Carrousel 2000 system graphic charts
3. Carrousel oxidation ditch mechanism
3.1 Carrousel oxidation ditch sewage treatment principle
The initial general Carrousel oxidation ditch process with sewage sludge directly back into the oxidation ditch system. Surface aerators to DO concentrations of dissolved oxygen in the mixture to about 2 ~ 3mg / L. In this fully mixed with oxygen under the conditions of micro-organisms get enough oxygen to remove BOD; the same time, ammonia was oxidized to nitrate and nitrite, this time, the mixture at aerobic condition. In the aerator downstream from the aeration zone of the turbulent flow state into the stratosphere after the state maintain a minimum flow rate of water flow, ensuring activated sludge in suspension (mean velocity> 0.3m / s). Microbial oxidation of dissolved oxygen consumed in water, until the DO value is zero, the mixture was hypoxia. After anoxic denitrification zone, the mixture into the aerobic zone to complete a cycle. The system, BOD degradation is a continuous process, nitrification and denitrification occurred in the same pool. As the structural limitations, such oxidation ditch Although you can place an effective BOD, but the limited capacity of nitrogen and phosphorus removal.
Nitrogen and phosphorus removal in order to obtain better results, Carrousel
2000 Carrousel oxidation ditch system in general an increase of an anaerobic zone and the anaerobic zone (also known as pre-denitrification zone). All return sludge and 10-30% of the sewage into the anaerobic zone, the sludge can be returned in the residual nitrate nitrogen in the oxygen and carbon conditions, 10-30% complete denitrification, oxygen tank for the future must create absolute oxygen conditions. Meanwhile, the anaerobic zone and bacteria to soluble BOD into VFA, phosphate accumulating bacteria get into VFA to the same PHB, the required energy from the hydrolysis of phosphorus and lead to the release of phosphate. Anaerobic zone within the installation of water into the blender anaerobic zone, the so-called anaerobic tanks mixture is neither molecular oxygen nor oxygen compounds (nitrate), in anaerobic conditions ,70-90% of the sewage can be provide sufficient carbon to phosphorus accumulating the full release of phosphorus. Anaerobic zone followed by a general Carrousel oxidation ditch system, further complete the removal of BOD, nitrogen and phosphorus. Finally, the mixture of oxygen-rich zone in the oxidation ditch discharge, the oxygen-rich environment, excessive uptake of phosphorus accumulating bacteria, the transfer of phosphorus from water to sludge, with sludge removal system. Thus, in the Carrousel 2000 system, were well completed the removal of BOD, COD and nitrogen and phosphorus removal.
Integrated with the process of Kunming is the first wastewater treatment plant [9], the second wastewater treatment center in Changsha City [10] and Luohe run effects of sewage treatment plants can be seen: after Carrousel 2000 system after treatment, BOD, COD, SS removal rate reached 90%, TN removal efficiency reached 80%, TP removal rates reached 90%.
3.2 Carrousel oxidation ditch impact factors of phosphorus and nitrogen removal
Carrousel Oxidation Ditch affect phosphorus removal sludge age is the main factor, nitrate concentration and substrate concentration. Research shows that when the total sludge age of 8 ~ 10d when the activated sludge for maximum phosphorus content of 4% of the amount of dry sludge, heterotrophic bacteria for the quality of 11%, but more than 15d, sewage sludge age maximum phosphorus content in soil