Experimentai Study On Nitrogen Of Living Sewage With Pre-denitrification BAF

As the society attaching great importance to sewage treatment, a large numberof sewage treatment plants are currently invested and constructed in small towns.How to guarantee the water quality under the condition of low investment, less landoccupation and convenient operation management is the common goal of allvillages and towns government. The pre-denitrification BAF process is graduallybuilt and used, which has the unique advantages to meet the needs of thedevelopment of the sewage treatment. And this process is along physicalentrapment with biological treatment in the same reactor, which has the advantagesof little land occupation, low investment and good performance.Accordance with the test design requirements, we use the volcanic rock as thebiological filter material and use the pre-denitrification BAF technology to treat thesewage of Harbin Institute of Technology, and from which we target for the studyof the removal efficiency of COD, ammonia nitrogen and TN, exploring its laws toremove contaminants and analyzing the changes and transformation rules ofnitrogen compounds and then discuss the removal mechanism, which provides atheoretical basis for the technology used in the actual project.And the reflux ratio is its main factors affecting treatment efficacy at the sameas the hydraulic loading. Experimental results showed that the system was suitablefor the optimum reflux ratio of100%and the optimal hydraulic loading of2.02m/h.We operated the system in this condition, and according to the results we could seethat the removal of COD, ammonia nitrogen and TN performed well, with theremoval rate87.50%,95.37%and59.93%. Meanwhile, we found that the removalof COD and TN occurred mainly in the anaerobic reactor column, which rate was61.78%and53.06%, while the removal of ammonia relied mainly on thenitrification process.Study of the rules of DO and pH along the change showed that the DOconcentration decreased gradually in the anaerobic reaction column, increasing inthe aerobic reaction column. And pH is just to show the opposite trend.Researching the transformation of nitrogen compounds along the way, wesummarized that the ammonia nitrogen and nitrate converted into each other in theaerobic reaction column, which leaded to the low removal of TN; and in otherwords, we found that the removal of TN occurred mainly in the anaerobic reactorcolumn, where there were simultaneous nitrification and denitrification andanaerobic ammonia oxidation. In this experiment, we used a joint air and water backwash backwash way. Andafter the backwash, the removal efficiency of COD and ammonia nitrogen wasmomentarily down and returned to normal after6hours; and the backwash played asmall role on the effect of the removal of ammonia nitrogen.