Control For The Dissolved Oxygen And Nitrate Nitrogen Removal System In The Wastewater Treatment

The removing of organic substrates in the wastewater concerns with thedissolved oxygen and the microorganism in the treatment system. So in thisthesis, the author focused on the controlling of the dissolved oxygen andnitrate nitrogen removal. Based on the activated sludge model NO.1, theauthor established model of one basin, and to test and verify the quality of thissystem, the author compared the effluent quality between one basin systemand the benchmark simulation model no.1(BSM1).Firstly, based on the one basin system, the author researched thecharacters of heterotrophy bacteria, organics and dissolved oxygen (DO), andthen constructing the DO simulation platform and identified the relationshipbetween oxygen transfer rate and DO. Based on the internal model controltheory, the author improved PID parameters tuning rules by setting theovershoot of the system and after ceaselessly change the model and choosethe optimal tuning factor. The simulation turned out that the improvedparameters tuning rules can provide better result in the DO control and theorganics removal. Secondly, to obtain better nitrate nitrogen removal result,the author researched the relation of the influent flow rate, external carbonresources and nitrate nitrogen. And based on the identified models, the authorcompared two different control methods to find the better strategy. With thehelp of the nitrate nitrogen simulation platform, the author found the nitratenitrogen feed forward-feedback control method was more efficient in nitratenitrogen removing and also needed less external carbon in the same time.