| Denitrification in three floating-plant systems, including two subspecies of hyacinth and duckweed, and foamy board system were investigated by batch cultivation at a low water temperature of 6.8～7.2℃. Effect of initial COD on the system at a water temperature of 6.4～11.2℃ was also discussed. The results were obtained as follows: DO was one of the important factors, NH4+-N removals in aerobic condition were 61%～88% in overall period. NH4+-N removal in plant systems was higher than that in the foamy board and control systems while differences of TN and COD removals among plant system, foamy board system and control system were determined by the floating-plant type. The increase of initial COD concentration, followed by the decrease of DO from >4 mg/L to 0 mg/L, resulted in an obvious improvement of NO3--N removal. However, it had a less effect on other water quality norms such as COD, TN and NH4+-N. |
