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 ℃) and warm season (24.6–29.8 ℃) 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 NO 3 − –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.