Tide-tank system simulating mangrove wetland for removal of nutrients and heavy metals from wastewater

Kandelia candel plants were grown in a simulated tide-tank system in the greenhouse to determine the performance of the mangrove ecosystem in treating synthetic wastewater of various strengths (NW, 5NW and 25NW). NW had a strength similar to the natural municipal wastewater, while 5NW and 25NW had 5 and 25 times, respectively, the amount of nutrients and heavy metals as in NW. The system was flooded daily with artificial seawater to simulate the tidal regime. Synthetic wastewater was irrigated to the system three times a week for 3 months. The results of effluent characteristics showed that the removal efficiencies of nutrients and metals from the wastewater were nearly 98% (except for organic N) and 96%, respectively, in NW and 5NW tanks whereas those of 25NW tanks were 75% for nutrients, 92% for Cd, Cr, Cu and around 88% for Ni and Zn. This study demonstrated that the mangrove ecosystem had a very high capacity to retain or immobilize the nutrients and heavy metals in the wastewater suggesting mangrove wetland had inherent physical, chemical and biological properties for adsorption and utilization of nutrients and heavy metals.