How Artificial Aeration Improved Sewage Treatment of an Integrated Vertical-Flow Constructed Wetland

Artificial aeration was added to an integrated vertical-flow constructed wetland (called aerated IVCW hereafter) for improving water purification performance. The results showed that both oxygen levels and aerobic zones were increased in the wetland substrates. The electric potential (Eh) profiling demonstrated that artificial aeration maintained the pattern of sequential oxic-anoxic-oxic redox zones within the aerated IVCW chambers in winter, while only two oxic-anoxic zones were present inside the non-aerated IVCW in the cold seasons. The nitrification/denitrification processes and organic matter decomposition were enhanced by artificial aeration since the removal efficiency of NH4--N and BOD5 were significantly improved in all seasons, particularly in winter. It seemed that artificial aeration could compensate for the absence of plant-mediated oxygen supply, though the low temperatures and plant dieback still affected the removal efficiency of COD and TN in the winter. Eight hours of artificial aeration per day was sufficient to eliminate the significant accumulation of NO3--N previously observed in the effluent from continuously aerated subsurface-flow constructed wetlands. These results suggest that the aerated IVCW could treat domestic sewage more efficiently, especially in winter.