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4/2/2019 Effect of C/N Ratio on the Removal of Nitrogen and Microbial Characteristics in the Water Saturated Denitrifying Section of a Two-Stage C... <br /> 52 36 <br /> c <br /> LA c� <br /> 48 32 c4 <br /> U44 ®Denitrifying bacteria 28 ZD <br /> 0 40 - nitrifying bacteria U <br /> 36 <br /> 24 <br /> 32 <br /> 20 <br /> 28 ca <br /> 24 16 c <br /> 20 <br /> 12 <br /> 16 <br /> J <br /> Q <br /> 12 8 a� <br /> r <br /> 8 = <br /> 4 -' <br /> 4 <br /> ".J <br /> 0 A- 0 <br /> T1 T2 T3 <br /> Experimental tests of two stages CRI system <br /> Figure 7 <br /> The number of denitrifying bacteria(106 CFU-(a sand)-[)and nitrifying bacteria(103 CFU•(g sand)-t)in <br /> the sand of the water-saturated denitrifying section. <br /> The numbers of denitrifying bacteria were a factor of 1000 higher, in the order of 106-107 CFU-(g <br /> sand)—', In particular in T3 their numbers peaked to 5.1 x 107 CFU-(g sand) 1,which was over 20 <br /> times higher than in T1,and 10 times higher than in T2. Therefore,under the water-saturated <br /> conditions applied, an increase of the C/N ratio in the influent promoted the proliferation of <br /> denitrifying bacteria as long as the nitrogen supply was sufficient. When the C/N ratio increased from 2 <br /> to 5, the number of denitrifying bacteria increased by more than one order of magnitude. Combining all <br /> results, it was found that the concentrations of TN and NO3--N in the second stage effluent decreased <br /> with an increase in numbers of denitrifying bacteria in the water-saturated denitrifying section. This <br /> suggests that the number of denitrifying bacteria presenting this section of the CRI is animportant <br /> factor determining the nitrogen removal performance, and this can be influenced by changing the C/N <br /> ratio. However,the specific relationship between the bacterial abundance and the nitrogen removal <br /> performance needs to be further explored. <br /> The amount of S-EPS,LB-EPS and TB-EPS in the formed biofilms was determined for the denitrifying <br /> section and the total EPS concentration was calculated as the sum of these fractions. The <br /> concentrations of proteins and carbohydrates were also determined,with results shown in Figure 8. <br /> Panels 8a and 8b show that the amount of biofilm S-EPS and LB-EPS was higher in T2 than in T1, <br /> probably as a result of the increased C/N ratio, though a further increase of this ratio in T3 did not <br /> https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6069465/ 13/18 <br />