Efficiency of duckweed (Lemnaceae) for the desalination and treatment of agricultural drainage water in detention reservoirs

Abstract

High levels of soil salinity and water mineralization are one of the major problems in arid and semi-arid areas, in particular in Central Asia and North Africa. Besides technological water management solutions, accompanying methods of phytoremediation have been scientifically proven in detention ponds which are integrated into irrigation drainage systems. We report on investigation methods concerning the salt uptake potential of the aquatic macrophytes Lemnaceae (duckweed), and regarding technical construction requirements to enhance the purification of drainage water in water reservoirs. The assessment of this method was carried out under laboratory conditions at the Leibniz Centre for Agricultural Landscape Research (ZALF). The results demonstrate that the salt uptake behaviour of duckweed in the form of enclosure in its tissues depends on the degree of salinisation and the initial biomass density. The uptake effect can be described as a first-order decay reaction. The decay/uptake depends on the residence time within the water body. To maximize the detention time in reservoirs the effect of baffles and inlet constructions in the reservoir are investigated using 2D hydraulic modelling with the model package TELEMAC. Therefore, this method is proposed for Central Asian regions as a measure to be taken against high levels of salinity in water bodies.