INVESTIGATION OF THE POTENTIAL OF ARTIFICIAL FLOATING ISLANDS (AFIS) FOR WATER QUALITY IMPROVEMENT OF RESIDENTIAL WASTEWATER

Artificial Floating Islands (AFIs) is one phytoremediation technology involves the application of naturally occurring plants as floating hydroponic mats on the water surface, where emergent plants are inserted in a buoyant mat suspended in a floating support, with the crowns and the shoots growing above the water level while the root systems growing deeper into the water column. It has been documented as an efficient, environmentally friendly, and cost-effective method to improve water quality in many water bodies including ponds, river, lakes, and reservoirs. However, most studies on pollutants’ removal by AFIs were conducted in controlled conditions, such as in mesocosms and microcosms while applications of AFIs in natural (field) environments were much less reported. In addition, the pollutant-removal efficiency of AFI systems varies widely with changes in physical and chemical conditions, even for the same species of plants. Moreover, understanding of the microbial communities associated with plants in AFIs is still limited, especially for the effects of polyculture on microbial composition.

To fill the gaps identified, this study conducted a field experiment at the equalization basin of Plymouth Wastewater Treatment Plant in north-central Ohio, using two plant species native to Ohio, Carex comosa and Eleocharis obtusa. 12 AFI units were deployed between the supply line (inlet) and return line (outlet) of the basin, aligned in three linear systems parallel to each other. Four types of AFI units (AFI with C. comosa, AFI with E. obtusa, AFI with polyculture of two species, and AFI with no plant) were used to construct each linear system.

Specific objectives of this study include: (1) Assessing the removal efficiency of nutrients (organic and inorganic) and trace metals of AFI systems in a natural environment. (2) Comparing the performance of two plant species native to Ohio to establish a baseline of pollutant-removal efficiency for tested plant species. (3) Assessing the effect of polyculture of plant species on the performance of AFIs. (4) Comparing the microbial composition from the rhizosphere and root endosphere of the two plant species, and (5) Assessing the effect of polyculture on the diversity of microbial composition.