In order to assess the impact of different carbon/nitrogen (C/N) on anoxic/aerobic sequencing batch reactor (SBR) nitrosation system

the C/N was adjusted to 0

2/3

1

4/3

2

3

6 at room temperature (18-20 ℃). The results showed that the activated sludge system with the influent chemical oxygen demand (COD) loading and ammonia loading of 0.2 and 0.3 kg/(m3·d) successfully achieved nitritation only after 24 d. It needed more time to achieve nitritation with no COD in influent. When the C/N was less than 6

the system maintained good nitritation performance with the nitrosation rate of over 90%. When the C/N was 6

the nitrosation rate dropped to 70%. When the C/N was 4/3

the heterotrophic bacteria used the influent COD for denitrification adequately

the total nitrogen removal efficiency reached 49.8%

and the COD removal efficiency remained above 80%. Because the sludge system lacked the carbon source

the total nitrogen removal efficiency increased with the increase of the C/N when it was less than 4/3. When the C/N was 4/3 to 2

the COD and total nitrogen removal efficiencies almost remained unchanged. When the C/N was 2 to 6

due to the reduction of influent ammonia loading

the removal efficiencies of COD and total nitrogen showed a downward trend. At the end of operation (154 d)

COD and total nitrogen removal efficiencies were 64.8% and 18%

respectively. When the C/N increased due to an increase in COD

the proteins (PN) tended to increase gradually

and polysaccharides (PS) almost did not change

while the decrease in ammonia caused an increase in the C/N

PN and PS decreased

but the value of PN/PS increased.