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4/2/2019 Effect of ON Ratio on the Removal of Nitrogen and Microbial Characteristics in the Water Saturated Denitrifying Section of a Two-Stage C... elevate S-EPS and LB-EPS further. Their concentrations all remained below 10 mg/g SS. In contrast, " the fraction of TB-EPS (panel 8c)was higher in T2 than in T1,and higher still in T3,with ` concentrations exceeding 10 mg/g SS. The total EPS reached nearly 30 mg/g SS in T3 (panel 8d). This increase in biofilm EPS as a result of the increase by ON ratio was mostly attributed to TB-EPS, confirming that TB-EPS is the key factor affecting the concentration of total EPS [19]. 10 y a-I'rntan in S.1 I'S 9 -+•-Poecm m I b -0--CarNkdrate in S+PS t l'arthhyJratc in!ii t o- g -T-Tanl S-FPS � 8 �-I nr11 B.I.Iti __► 7 r f `r' -, ' ♦ E T 6 5 5 �— -_.- __ • - 4 . 2 !_ T1 T2 TJ T1 T2 T3 E%pedmeatal tests oftwo stages CRI system [spettmenl:d festa of twn steges CRI%)stern a h 14 40 160 -+-I'mtcm m 11 LPS t total WS 12 em +CarKANdrate in 1'WFPS 36 Pcrceape of prnkut m total W., 140 �-I ural I Il-F:PS v: <•,IYnrnma),a.d carlxeh\'trate m tnul F.PS U 30 120 E t0 E --+ v a 25 100- a H ��• y 20 80 6 0 15 60 r j C to �-- 41i u u v 2 + 5 2U � t 0 � 0 0 T T, 72 T3 , T2 T3 I:spenntcnial tests 0f two stages CRI sytwrt f.rpcnmental tests of two stages('RI s}stem J Figure 8 The concentrations of EPS(triangles),and its protein(squares)and carbohydrate(circles)fractions(all expressed as mg/g SS)in the sand of the second stage system.(a)S-EPS;(b)LB-EPS;(c)TB-EPS;(d) Total EPS.The percentages of protein and carbohydrate fractions in total EPS are also shown as bars in (d) The comparisons of protein and carbohydrate fractions of EPS between T1, T2 and T3 produced a less clear picture,with an increase for proteins as a result of increased ON ratio in S-EPS and TB-EPS but not in LB-EPS. For the carbohydrate fraction, the trends were in the opposite direction(Figure 8). The reason for these observations may be that as long as the nitrogen source was sufficient in the influent, addition of extra glucose could promote the formation of protein in S-EPS, but this limited the production of carbohydrates due to competition. The fractions of both protein and carbohydrate were increased in TB-EPS when the C/N ratio was increased(Figure 8c),which indicated that the increase of carbon source could simultaneously promote the increase of protein and carbohydrate concentrations in biofilm TB-EPS. Moreover,the contents of protein and carbohydrate in total EPS (Figure 8d) showed the same changing trends as those of TB-EPS, which indicates that increasing the ON ratio in the https://www.ncbi.nim.nih.gov/pmc/articles/PMC6069465/ 14/18