Study On Oxygen Restoration Mechanism Of Constructed Rapid Infiltration System And Analyze On Flow Pattern

Constructed rapid infiltration (CRI) system is a whole new biology treatment system, developing step by step from the base of traditional land treatment by teacher ZHONG Zuo-shen of China University of Geosciences Beijing. Currently CRI is commonly used to treat domestic wastewater and slight concentration of river. This paper contains two main parts: First, through studying the air pressure change of the system, grasp the mechanism of oxygen restoration, explain the main oxygen restoration process of CRI system; Second, analyze CRI system's flow pattern by tracer testing. The main conclusions are:1,The study of closed CRI system(1) When sewage infiltrate into the system, the change of air pressure in the system is: the pressure in the system reach the peak negative pressure and come back to a tiny negative pressure in a little time, and then the tiny negative pressure last a long time.(2) At the same position of the system, the oxygen restoration balance time become longer with the running of the system.(3) At the period of culture experiment of biofilm, in the 50cm depth of the system, the correlate coefficients that oxygen restoration balance time being with adding time and infiltrating velocity are 0.86 and–0.82, but for the whole system the correlate coefficients are very low.(4) At the period of running steadily, the oxygen restoration balance times in the system's different parts are same, they have a high relativity with hydraulic load and adding time, and have a low relativity with infiltrating velocity.2,The air infiltrate into the system mainly from the surface of the medium, the experiment shows that it is difficult to make oxygen restoration from the bottom of the system.3,The effect of oxygen restoration have nothing to do with the position of the ventilating tubes. Adding the number of the ventilating tubes can enhance the capability of system oxygen restoration. In my experiment, from close to be with one ventilating tube and to be with two ventilating tubes, the system's oxygen restoration eliminate over 30min every time. Compare with the one ventilating tube's system, the system with two ventilating tubes raise 15% to the removal rate of ammonia nitrogen.4,CRI system's tracer testing shows, compare with pulse adding method, the continue adding method's results are more accurate and steady. The silver nitrate titration can substitute for electric conductivity to detect the concentration of the tracer. The result of tracer testing shows: before adding sewage CRI, system's real hydraulic retention time is in accordance with theory hydraulic retention time, there are not dead space and the phenomenon of short-circuiting; flow pattern of the system approximate the ideal plug flow; installing ventilating tube didn't make effect on the system's real hydraulic retention time.