Floating Wetland Treating System by the Small Earth Nepal

Eutrophication Process, Pratuysh Kayastha, Scott Wilson Nepal, 2023

Lake pollutants such as industrial waste, agricultural waste, untreated sewage, etc. contain high concentrations of chemicals such as nitrogen (N₂), ammonia (NH₃), Orthophosphate (PO₄-3), Iron (Fe), and phosphorus (P). These chemicals are important nutrients for algae and thus, promote rapid growth in the algae population when accumulated in lakes. As such, the disposal of pollutants into lakes results in the bloom of the algae population. As algae consume soluble oxygen, the bloom of the algae population results in the decrease of soluble oxygen which then goes on to create a scarcity of soluble oxygen in lakes. This ultimately results in the loss of aquatic life.

The process described above is known as eutrophication. To counteract eutrophication and subsequent degradation of water quality and aquatic life, The Small Earth Nepal (SEN) has initiated a project known as Floating Wetland Treating System (FWTS). This project is supported by the Asia-Pacific Network for Global Research (APN) and is done in collaboration with the University of Dhaka (DU), Central University of Rajasthan (CURAJ), University of Yamanashi (UY), Kathmandu Valley Water Supply Management (KVWSM), Tribhuvan University Board (TU), University of Rhode Island (URI).

The project designed a raft containing approx. 50 Indian shot and/or Scarlet sage plants. As per the researcher working on this project, Ms. Ayaswori Byanju, the roots of these plants float freely in the lake water and absorbs nitrogen, ammonia, Orthophosphate, Iron, and phosphorus thereby reducing the concentration of nitrogen by 99.5%, ammonia by 90.2%, orthophosphate by 86.7% and iron by 61%. This would reduce the nutrients required for algae growth which could eventually reduce the algae population. This process was shown to free up the soluble oxygen in lakes that are otherwise consumed by high algae populations and thus, it was observed that soluble oxygen increased by 50%. This could result in a greater level of soluble oxygen being available for aquatic plants and animals. In this way, the project tried to restore aquatic ecology in lakes that were affected by eutrophication.

Photo Source: Small Earth Nepal