A Comparative assessment of the phyto-desalination rates of duckweed and water hyacinth in brackish water

Abstract

Brackish surface water is a challenge for most estuarine communities to meet the water requirement for agricultural purposes. Desalination plants on the other hand, are costly and energy consuming method to run. This research compares the possible use of duckweed and water hyacinth for their phyto-desalination rates of brackish water. Three replicates containing about 100 g of each aquatic macrophytes in a trough with 10 litres of brackish water (salinity 7.69 ppt) were studied daily for 6 days.  Electrical conductivity (EC), pH, total dissolved solids (TDS) and salinity were the measured water parameters thereafter, the treatment means were calculated. Results showed that maximum reductions of most of the water parameter were observed after 3 days of the research for both aquatic macrophytes. A reduction of EC by 16.4 %, TDS by 16.3 % and salinity by 20.7 % for duckweed while for water hyacinth, a reduction of EC by 20 %, TDS by 19 % and salinity by 29.1 % were observed. Thereafter, both aquatic macrophytes started showing signs of nutrient starvation and a reduced rate of desalination. This can be addressed by removing the spent and wilting aquatic plants and re-introducing fresh ones in 3 days intervals until desalination is achieved. Anova shows that there was significant difference between pre-and post-treatment values at 95 % confidence level in EC for both duckweed and water hyacinth treatment and also in TDS and salinity for water hyacinth treatment. This suggests potency of water hyacinth in the desalination of brackish water for crop irrigation and other agricultural purposes.