Biotoxicity evaluation by bioassays can assist in a general assessment of the possible hazardous effects of chemicals (including known and unknown ones) existing in water on aquatic life and human health. Table 2 shows the results of an array of bioassays regarding the reclaimed water and lake water and indicates the remarkable action of the landscape lake, which is equivalent to open storage of the reclaimed water under natural conditions, for a substantial reduction of the biological toxicity from the residual hazardous substances (Ma et al. 2018).
Biotoxicity comparison of the reclaimed water and lake water
| Bioassay . | Luminescent bacteria . | Alga Chlorella vulgaris . | Larva zebrafish . | SOS/Umu . | |
|---|---|---|---|---|---|
| Vibrio fischeri . | Vibrio qinghaiensis . | ||||
| Index | TEQphenol | TEQphenol | Inhibition | Mortality | TEQ4-NQO |
| Reclaimed water | 7.1 ± 1.1 mg/L | 18.9 ± 0.8 mg/L | 19.1 ± 0.4% | 14.6 ± 2.1% | 4.6 ± 0.1 μg/L |
| Lake water | 4.1 ± 0.5 mg/L | 6.3 ± 0.4 mg/L | 8.9 ± 1.0% | ND | 0.5 ± 0.1 μg/L |
| Bioassay . | Luminescent bacteria . | Alga Chlorella vulgaris . | Larva zebrafish . | SOS/Umu . | |
|---|---|---|---|---|---|
| Vibrio fischeri . | Vibrio qinghaiensis . | ||||
| Index | TEQphenol | TEQphenol | Inhibition | Mortality | TEQ4-NQO |
| Reclaimed water | 7.1 ± 1.1 mg/L | 18.9 ± 0.8 mg/L | 19.1 ± 0.4% | 14.6 ± 2.1% | 4.6 ± 0.1 μg/L |
| Lake water | 4.1 ± 0.5 mg/L | 6.3 ± 0.4 mg/L | 8.9 ± 1.0% | ND | 0.5 ± 0.1 μg/L |
Notes: (1) Samples were collected during a 7-month period after the whole system (shown in Figure 3) had been put into continuous operation for 5 years. (2) TEQ: toxic equivalent concentration with phenol as a reference compound for luminescent bacteria assays and 4-nitroquinoline-N-oxide (4-NQO) as a reference compound for the SOS/Umu assay.