Identifying prospective water plants for reducing nutrients and total coliform in sub-surface constructed wetlands with limited oxygen

Abstract

Extensive aeration is required for constructed wetlands (CWs) since dissolved oxygen is essential in nutrients and pathogen removal. On the other hand, plants typically used in CWs can release oxygen into the system, lowering the need for external aeration. Hence, this study tried to uncover the oxygenation rate of three species of plants in the CWs system with limited oxygen and their capability to treat wastewater. Canna sp., Heliconia sp., and Typha sp. were used and compared to uptake nutrients and reduce coliform numbers in domestic wastewater using sub-surface CWs in low levels of initial oxygen. In the meantime, oxygen release from the plant root was monitored in real-time using an IoT-based module. On the detention time of 24 hours, CWs planted with Typha sp. were able to reduce 61% NH₄⁺ and 71% PO₄^3-. The system was also able to remove coliform with a magnitude of 1.39 log units. In addition, Typha sp. was observed to generate a higher oxygenation rate to the CWs system compared to the other two plants at 0.175 %/h, on average. These observations suggested that Typha sp. had the best prospect to be used in a sub-surface CWs system with the least external aeration needed.