Research on the Purification Performance of a Floating Island System Treating the Effluent of WWTP Under Different Seasons

In order to improve the purification performance of the floating island under fluctuated temperature and flow, a floating island system was constructed through Rumex japonicus Houtt (RJH), Iris sibirica (IS), and artificial aquatic mat (AAM) to treat the effluent from secondary clarifier. The performances under different flow in cold season (6.9-17.9 degrees C) and warm season (24.6-29.8 degrees C) were investigated. The results showed AAM was the main nitrification unit enriched with Nitrosomonas (0.1134-0.1832%) and Nitrospira (0.1914-1.8124%). The matrix of IS and RJH provided an ideal denitrification place enriched with Azospira (0.3724-0.4411%, 0.2902-0.7517%), and abundant Pseudomonas was found on the root of RJH (12.32-13.67%). Under the same flow, the nitrification activity was bigger in warm season; there was a close correlation between the removal efficiencies of total nitrogen (TN) and NO3--N (R-2 = 0.9940) in cold season. This study clarified the variations of microbial communities of the floating island systems under different temperatures and hydraulic retention times (HRTs) and provided guidance to compensate in-situ purification performance through optimizing plant species and constitution.