Design And Implementation Of COD Testing Apparatus Based On Electrochemistry

Nowadays,the problem of the water pollution are becoming more serious,which threaten our daily life and economic development,so,more and more attention have been paid to monitor and treat the pollution.Chemical oxygen demand(COD) is an integrative index for evaluating the degree of organic pollution in water,and is one of the important parameters in water quality monitoring,and is also a main index of the total emission reduction target in the 11th 5-Year plan,therefore,the COD testing apparatus play an important role in water quality monitoring.Now there are many kinds of COD testing apparatus and they are designed in different test principles.The aim of this subject is to design a COD testing apparatus which is high accuracy,low cost,short detection time and without secondary pollution through electrochemical technique.The development of COD testing apparatus involves the three aspects:the selection of the COD measuring method,the design of hardware system and the design of software system of COD testing apparatus.Based on detailed analysis of COD detection technologies and current development situation of detecting instruments,comparing to other measurement technique,this paper selects the electrochemical measurement technology based on oxidation method of hydroxyl radical(·OH) which uses tri-electrode electrochemical sensor.The instrument consists of upper subsystem and lower subsystem.The upper subsystem adopts the embedded system which is used widely in automation instruments to control of working process of the COD testing apparatus system.The applications are programmed with Embedded Visual C++ on the platform of Windows CE embedded operation system.The lower subsystem uses AT89S8252 single-chip microcoputer as core,the applications are programmed with C51 programming language.It realize the sensor control,signal acquisition and processing,and data transmission,and so on.The communication between upper and lower subsystem is based on RS232 serial port.In this paper,a COD testing apparatus with simplified operation,short analysis time and no secondary pollution has been developed.The accuracy test has been carried out through circuit model of the electrochemistry sensors and compare with CHI650B electrochemistry workstation using real water sample.The results show that the COD testing apparatus is high measuring result and wide application prospect.