Abstract
The full-scale constructed wetland treating wastewater from PET bottle recycle plant was investigated and its treatment performance for 29 months was evaluated. This constructed wetland may be the first full-scale system to treat industrial wastewater other than from livestock industry. The lab-scale experiment reproducing the clogging happened in the constructed wetland was also performed to clarify factors causing clogging. It was found that the BOD5：N：P ratio in raw wastewater was 100：0.30－0.43：0.01－0.02, which proportion of nitrogen and phosphorus against BOD5 were significantly lower compared with reasonable proportion for biofilm formation and plant growth. The BOD5, CODCr, T－N, T－P, and SS removal efficiencies for 29 months were 78, 77, 76, 81, and 65％, respectively. The treatment performance fluctuated, and BOD5 and CODCr removal efficiencies did not always satisfied National Effluent Standards. The treatment performances in the second year, especially during the winter seasons were quite low. It was because of overflow involved in clogging. Based on the biodegradable property of organic polymer flocculating agent （OPFA） and the results of lab-scale experiment, it was indicated that the clogging was caused by OPFA used for a pre-treatment of effluent from waste PET bottle washing process. These results suggest that the property of OPFA should be considered when coagulation sedimentation process is used for a pre-treatment of constructed wetland.
