Effluent of municipal secondary treatment was chosen、raw water to re一start up the 0/A bio- logical sarxl filters which stopped running nearly five months, in the way of increasing hydraulic load grad- ually. The secondary start- up speed, the removal effect of nitrogen and cardon, the influen of C/N ra- do on removal effect of nitrogen and carbon were mainly studied. The resups showed that the membrane at- torched on the surface of quartz sand‘not dead, the 0/A biological sand filters can back to normal run in a very short time. During stable operation, the average removal of CODS_Cr and NH₄⁺一Nwere 45. 53% and 65. 50% respectively, and the average concentration of CODS_Cr and NH₄⁺一N in effluent were 48. 5Omg/L and 4. 12mg/L respectively. The removal efficiency of 0/A biological sand filters is high for total nitrogen when the C/N ratio us 5. 0; the removal rate of total nitrogen reaches above 30%，the average concentration of TN in effluent is lower than 15 mg/L. The effluent quality met the first A class standard of “urban sewage treatment plant pollutant discharge standard"(GB 18918- 2002).