3. Results and analysis
3.1. Adaptation of Ottelia to the four simulated sewages
Considering 10 days as the counting cycle, the number of flowers was counted from first flowering to June 1 as the total number of flowers on June 1, and that from June 1–11 as the total number of flower on June 11. Given that the flowering phase of Ottelia is 2 days, the possibility of repeated counts could not be ruled out, and the number of flowers for each group was only for relative comparison. During the whole cultivation period, the total number of flowers in groups A, B, and C was 122, 62, and 5, respectively, whereas flowering was not observed in group D, as shown in Fig. 1.