Table 1 shows that the CW removal rates of TP and TN were 23.02% and 21.78%, respectively, far lower than that of the COD. However, when compared with the TP and TN in the duck pond water (Fig.7), the difference was significant (Table 2). The TP and TN of the duck pond rose to 11.67 and 14.94 mg/L, while those of the CW were 6.62 and 9.95 mg/L, respectively. Although this was a sharp decline, these TP and TN levels were still high. This was related to the treatment capacity of the CW. With the temperature falling, water hyacinths as well as other biological organisms, especially microbes, slowed their activities and growth, resulting in less effective removal of TP and TN.