Study On The Nitrogen And Phosphorus Removal Under Linkage Control Based On ORP In Carrousel Oxidation Ditch

As the completion of a number of sewage plants in the Three Gorges ReservoirRegion, its idea of protecting the water environment has shifted to effluent qualityimprovement and the energy-saving and consumption reduction of the built sewageplants. This has raised a higher claim of the operation and technique of the sewageplants in the reservoir region. This experiment takes the Changshou Sewage Plant as anexample, and thus launches a study of the promotion for the regulation and control ofthe technique of the Carrousel oxidation ditch of the sewage plants in the cities in thereservoir region.This test aims at the phase Ⅱ oxidation ditch under the mode of constant aeration,the oxygen requirement of the system changes with the influent water quality andquantity, Process operation parameters, microbial activity, the oxygen requirement ofconstant system and the aeration rate was not match, in some times system aeratedexcessively, this caused the effect of nitrate accumulation, and serious influence to eachindex of effluent. The test was based on the ORP specific guidance on process operation,and researched the relationship between ORP with technological parameter and nitrogenand phosphorus removal in oxidation ditch process, finally got the optimal control rangeof ORP to nitrogen and phosphorus removal,which guide process parameter control, andanalyzed the running effect before and after the regulation and operation stabilityanalysis, get the following conclusion:1) The main influencing factors of ORP in the aerobic zone of the oxidation ditchare DO, nitrate nitrogen, ammonia nitrogen, and has displayed a good relevant relationof the ratio of the density of those molar concentration, the relevant coefficient R2is0.906, the relational expression is as follows:2) The main influencing factors of the ORP in the strictly restrictive anoxic zone ofthe oxidation ditch（DO<0.2mg/L）are nitrate nitrogen, ammonia nitrogen, and hasdisplayed a good relevant relation of the ratio of the density of those molar concentration, the relevant coefficient R2is0.989, the relational expression is asfollows:3) The optimal control interval of ORP in the aerobic zone and the anoxic zone are0~50mV and100~150mV respectively, and the value of ORP is better close to the lowerlimit in the high temperature seasons; and in the low temperature the value of ORP isbetter close to the upper limit.4) The main influencing factors of the ORP in the anoxic zone is the quantity ofnitrate brought by the returned sludge and the density of the water reducing substances.When the ORP value is between-500mV and-300mV, it has a good effect ofphosphorus removal. At the same time, stabilization of the actual running is also veryimportant.5) The main linkage control parameters of the linkage control of ORP includes DO,the reflux ratio R. MLSS, SRT played as a auxiliary control parameter. And the value ofMLSS is better controlled between2800~3300mg/l, when in summer the value is betternear the lower limit and in winter upper limit. The sludge age is better controlledbetween6to8days. The pH value of the inflow water is stable and can satisfy theneeds of the basicity of nitrogen removal, and acts as a reference control parameter. TheHRT is defined by the quantity of the inflow water and it has a limited space for controland regulate, it acts as reference control parameter as well.6) The ORP linkage control and regulation has improved the efficiency of nitrogenand phosphorus removal by22.91%and13.49%respectively. And the powerconsumption of removing COD and TN per units has reduced by22.12%and25.47%correspondently. And the total power consumption has reduced about2868kW·h/d. Itthus realizes the target of the better effluent quality in summer and stably reaches thestandard and in winter and it has a significant effect of energy-saving and consumptionreduction.