Comparison of two different ecological floating bio-reactors for pollution control in hyper-eutrophic freshwater

The use of ecological floating beds (EFBs) to control water pollution has been increasingly reported worldwide due to the severe situation of eutrophication in water bodies. In this study, two kinds of EFBs were set up under similar condition to compare their purification efficiency in hyper-eutrophic water. The conventional ecological floating bed (CEFB) was made of polystyrene foam board, and the enhanced ecological floating bio-reactor (EEFB) was designed as an innovative hollow, thin floating bed integrated with substrates of zeolite and limestone. The results showed that the EEFB increased treatment efficiency of total nitrogen (TN), total phosphate (TP), and ammonia nitrogen (NH4+-N) to 63.5%, 59.3%, and 68.0%, respectively. Plant accumulation was the main pathway for TN and TP removal in the CEFB. Microbial degradation played an increasingly important role in TN and TP removal in the EEFB. A higher concentration of nitrogen cycling bacteria was recorded in the EEFB than the CEFB (P < 0.05), suggesting that the substrates might enhanced the removal efficiency of the EEFB by promoting the growth of microorganisms rather than their absorption effect.