Developing Aero-Floating Treatment Wetland (AEROFTW) Scaffolds: A Non-Plastic Alternative to Conventional Plastic-Based FTWS

This research was conducted to explore the possibility of constructing floating treatment wetlands (FTWs) without using plastic materials. FTWs are floating platforms that hold plants on the water’s surface, letting roots dangle within the water column, to help remove contaminants from contaminated water, especially in stormwater ponds. Many conventional FTWs are made with plastic components, such as mats and plastic cup containers, which can release microplastics into the environment over time. The goal of this project was to design and test a new type of FTW that does not depend on plastics to support FTW flotation. The study took place at the South Carolina Water Resources Center in Pendleton, South Carolina, where all experiments were carried out at a small scale inside a greenhouse. The main material tested was an aero-glass aggregate, made of 99% recycled glass. These glass aggregates were evaluated for their ability to provide buoyancy to the floating structures. Because this new design primarily relied on these glass materials, we named it aeroFTWs. Additional natural and non-plastic materials including jute burlap fabric, jute twine, bamboo, and steel hardware cloth were used to complete the design and support the structure. We also assessed whether wetland plants could grow normally in this new design by measuring their root length and shoot height throughout the experiment. The project consisted of two experiments. In Experiment I, we used burlap fabric, jute twine, bamboo, and glass aggregates to construct the aeroFTWs. We evaluated the growth of saltmeadow cordgrass (Spartina patens). However, the burlap and twine iii materials degraded quickly, causing the structure to lose integrity and break apart. As a result, we were unable to continue collecting root length data for this experiment. In Experiment II, we developed a stronger design that included glass aggregates and steel hardware cloth. This version maintained its structure throughout the experiment and remained stable. Pickerelweed (Pontederia cordata) and cattail (Typha latifolia) were planted in this design. Both species grew, but their shoot and root development was less vigorous than expected. This may have been due to the absence of organic materials that could provide nutrients to the plants or lack of enough nuitrients in the water for the roots to absorb so the plants could develop further. We also used a CT scanner to observe how the roots interacted with the glass aggregates. The scans revealed that the roots grew both around and inside the small pores of the glass aggregates (pieces). This finding suggests that plant roots can help hold the aggregates together and may play an important role in maintaining structural stability if other materials begin to degrade. Overall, this study demonstrated that recycled glass aggregates are a promising alternative to plastics for constructing FTWs. However, further research is needed to continue improving aeroFTW design, identify other durable, non-plastic materials that can complement this design and better support healthy plant growth.