Assessing the effectiveness of nature-based solutions to mitigate cyanobacteria blooms and remove toxins from...

Cyanobacterial blooms (CyanoHABs) and their associated toxins pose a significant threat to public health and water quality. A novel approach called Multi-Soil-Layering (MSL) has been developed and demonstrated to effectively and sustainably remove CyanoHABs and cyanotoxins from water. This study evaluated the MSL's ability to remove CyanoHABs on a laboratory scale. Two MSL mesocosms were designed to treat well water contaminated with Microcystis aeruginosa and MC-LR. These consisted of alternating permeable layers of a pozzolan and soil mixture layers arranged in a brick-layer pattern. The MSL1 used a sandy soil containing 8 % clay, while the MSL2 used a soil with a high clay content of 54 %. The mesocosms were continuously fed with a synthetic bloom at a hydraulic loading rate of 200 L m^-2 day^-1. The MSL systems effectively removed up to 90 % of the organic matter and nutrients. In addition, both MSL mesocosms were highly efficient at removing cyanobacteria cells and microcystins from the water, achieving a removal rate of over 99 %. Furthermore, both MSL substrates demonstrated the ability to adsorb and biodegrade MC-LR. These results suggest that MSL ecotechnology could be an effective and sustainable solution for removing cyanoHABs from freshwater ecosystems.