In order to improve removal efficiency of nitrogen

to enhance nitrogen removal process for low C/N ratio wastewater

and to accomplish denitrification

primary sludge was used as carbon source and NOx--N was added into primary fermentation system(PF) in this study.By investigating the variation of VFAs(volatile fatty acids)accumulation

NOx--N removal amount and VSS(volatile suspended solids) reduction

the fermentation and denitrification capacity of 4 different electron acceptor systems were contrasted.The results showed that VFAs had little accumulated for sole NO3--N and combined of NO2--N and NO3--N systems

while for sole NO2--N and anaerobic systems VFAs showed great accumulation

indicating that the use of carbon source was better for NO3--N and combined system.The total amount of removing electron acceptor for sole NO3--N

combined NO2--N and NO3--N and sole NO2--N systems were 1692 mg稬-1

1330 mg稬-1

1223 mg稬-1

respectively.Clearly sole NO3--N system had the best denitrification ability.Additionally

all these electron acceptor systems

with more than 60% VSS reduction

showed a great sludge reduction capacity

especially for NO3--N system

which reached about 67.9%

even though little decreased compared to the anaerobic system.In summary

for primary fermentation and denitrification system

using NO3--N as electron acceptor can achieve the best nitrogen removal efficiency and sludge reduction performance.