## 3 Results  
### Effects of RY86 Concentration on CW Effluent Quality  
During runs 1-15 conducted from 12 September through 30 November 2022, R86-containing wastewater was treated in the CWs in the sequencing batch mode under HRT of 5 days. Figure 2 shows the air temperature, evapotranspiration ratio, and the effluent RY86 concentration.  
Figure 2: Time courses of RY86 concentration (**A**), air temperature (**B**), and evapotranspiration (**C**) in CWs treating R86-containing wastewater.  
During runs 1-3 at temperatures higher than 25 \({}^{\circ}\)C in September, evaporation of wastewater in the unplanted CW was 10-35%, resulting in the effluent RY86 concentration of 12-15 mg/L, higher than 10 mg/L in wastewater. Evapotranspiration in the planted CWs was 30-50%. However, the effluent RY86 concentration was 6.6-7.7 mg/L in the Cattail-CW and 4.2-4.9 mg/L in the Papyrus-CW, indicating a marked degree of removal of RY86 by the presence of the plants. The effluent DO concentrations were 4.2-7.3 mg/L in the unplanted CW, 3.8-4.8 mg/L in the Cattail-CW, and 5.9-6.3 mg/L in the papyrus-CW.  
For runs 4-6, evaporation/evapotranspiration with 6-15% in the unplanted CW and 26-62% in the planted CWs. The RY86 concentration in wastewater at 20 mg/L was lowered to 16.8-21.0 mg/L in the unplanted CW, 9.1-13.1 mg/L in the Cattail-CW, and 5.1-8.5 mg/L in the Papyrus-CW. For Runs 7-9, evaporation/evapotranspiration was 8-21% in the unplanted CW and 30-47% in the planted CWs. The RY86 concentration in wastewater at 30 mg/L was lowered to 26.3-29.2 mg/L in the unplanted CW, 14.6-19.0 mg/L in the Cattail-CW, and 9.8-11.0 mg/L in the Papyrus-CW. For runs 10-12, evaporation/evaptotranspiration was 8-13% in the unplanted CW and 17-46% in the planted CWs.  
The RY86 concentration in wastewater at 40 mg/L was lowered to 36.5-39.9 mg/L in the unplanted CW, 21.2-28.6 mg/L in the Cattail-CW, and 10.9-13.4 mg/L in the Papyrus-CW.  
For runs 13-15 at 12-15 \({}^{\circ}\)C in November, evaporation/evapotranspiration was only 5-9% in the unplanted CW and 15-32% in the planted CWs. The RY86 concentration was set as 50 mg/L in wastewater, and it was 45.5-47.9 mg/L in the unplanted CW, 29.4-35.3 mg/L in the Cattail-CW, and 14.5-18.5 mg/L in the Papyrus-CW. The effluent DO concentration was 9.2-9.7 mg/L in the unplanted CW, 5.4-6.6 mg/L in the cattail-CW, and 7.6-8.3 mg/L in the Papyrus-CW, suggesting DO consumption by respiration of the plants and microorganisms in the rhizosphere.  
Figure 3 shows the typical absorbance spectra of wastewater containing 50 mg/L RY86 and its treated water in run 15. The absorbance of wastewater peaked at 416 nm. This peak value of effluent was markedly lower in the Cattail-CW and the Papyrus-CW. However, little or no decrease in the peak was observed in the unplanted CW. Apparent peak shift was not observed in the effluent samples. The main removal mechanism for RY86 in the CWs was regarded as adsorption to the roots and uptake by the plants.  
Figure 3: Absorbance spectra of wastewater and effluent of CWs: wastewater containing 50 mg/L RY86 **(a)**, effluent of the unplanted CW **(b)**, the Cattail-CW **(c)**, and the Papyrus-CW **(d)**.  
Relations between the RY86 concentration in wastewater and its mass removal for runs 1-15 at HRT of 5 days are summarized in Figure 4. The RY86 removal in the unplanted CW was less than 20% for 10-50 mg/L RY86. The removal values in the Cattail-CW and the Papyrus-CW were, respectively, 50-68% and 73-84%. The slight decrease in the removal with increase in the RY86 concentration was probably attributable to the effect of decreasing temperature.