Jakarta, BRIN Public Relations. Cynthia Henny, a researcher from the Limnology Research Center of the National Research and Innovation Agency (BRIN), won the 2021 (2nd) Hitachi Global Foundation Asia Innovation Award, under the category of Encouragement Award, for her research related to improvement of the water quality and restoration of the Lake Maninjau ecosystem, through application of an integrated aeration and floating wetland management system.

Lake Maninjau is a tectonic-volcanic lake located in Agam Regency, West Sumatra. Naturally, this lake has a high sulfur gas content in the bottom layer.

In the rainy season, sulfur gas often naturally rises to the surface of the lake or when there is a reversal of anoxic subsoil water mass to the surface triggered by wind, resulting in an oxygen deficit.

This natural phenomenon known locally as “tubo belerang” or sulfur poison is further exacerbated by exploitation of the lake’s resources through fish farming or known as Keramba Jaring Apung (KJA), or floating net cage during which the lake often experiences mass fish deaths.

“Naturally, volcanic lakes contain high sulfide gas. However, this condition in this lake is exacerbated by the existence of KJA that have existed for more than the last two decades, resulting in a massive decline of the lake water quality, eutrophication, hypoxic conditions, loss of biodiversity, and mass fish deaths,” explained Cynthia.

Starting in 2018, she and her team through the national priority research activities and in collaboration with the Ministry of Environment and Forestry and the local communities apply an integrated aeration and floating wetland management system as an effort to reduce the pollutant load due to KJA exploitation activities and increase water oxygen at critical times when sulfide gas rises to the surface of the lake.

“This system aims to improve the quality of the lake water, increase the oxygen level, maintain fish population and other lake biota and further improve the ecosystem health and increase the ecological benefits,” he added.

In more detail, Cynthia explained, floating wet land management is carried out by planting water or land plants in a floating medium, such as water jasmine. The roots of these plants are let loose penetrating the planting medium, which functions to absorb pollutants, such as nutrients or organic contaminants in the water as the cause of eutrophication and decrease of the lake water quality.

“Plants such as water jasmine are chosen because they are strong and wave resistant. The roots are not liked by fish, so the plants can grow, and fish can take cover beneath the plants,” explained Cynthia.

The floating wetland management system is then combined with an aeration system. There are two aeration systems used, namely the Fountain Aeration system and the ultrafine-bubble generator (nozzle).

The Fountain Aeration system, continued Cynthia, helps the movement of lake water by spraying water into the air so as to stimulate oxygen back into the water.

“This system helps agitate the water surface, such as a fountain, water from the lake is sprayed into the air thereby stimulating the presence of oxygen back into the water. The impact of oxygen stimulation from this system is indeed small in a an area of only 1 to 3 meters,” she said.

Ultrafine-bubble generator (nozzle) is installed beside the floating wetland treatment. This system serves to supply oxygen taken from the air, then put into the water, thereby increasing the oxygen level in the lake water.

“It works like a diffuser. This system supplies oxygen taken from the air, then the oxygen is put into the water, resulting in very small bubbles that increase the oxygen level in the water,” she explained.

The ultrafine-bubble generator (nozzle) has the effect of increasing the oxygen level in a larger area, 4 to 5 meters and the oxygen can last longer in the water.

In addition to improving the quality of water that is beneficial to the lake ecosystem, the integrated floating wetland management system and aeration ultimately have an impact on increasing the catch of local fish farmers in the area around the system.

“The residents admit that their fish catch has increased in the installation area of ​​this system in Lake Maninjau,” said Cynthia.

In addition to Cynthia, another BRIN researcher, Yenny Meliana, a researcher in the field of chemical engineering, won the Outstanding Innovation Award for her research on green-tech plant-based pesticides to handle water and soil pollution for a sustainable environment.

Two representatives from Indonesia also won the Encouragement Award category, namely Edwan Kardena from the Bandung Institute of Technology, and Jamaluddin Jompa from Hasanuddin University (tnt).