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Our project aimed to examine the ability of native duckweed (Lemna minor) to remove nutrients from farmyard pollutants. The results were then used to design a prototype remediation tank to facilitate the timely removal of nitrates and phosphates from effluents while allowing farmers to produce a cheap nutritious feed for cattle.
Firstly, fixed masses of Lemna minor duckweed were placed into dairy washing and silage effluent solutions of varying concentration for 20 days. The effectiveness of the species at nutrient removal was identified through studies of nitrate and phosphate concentrations while changes in duckweed mass indicated the suitability of each as a growth medium. The impact of duckweed remediation of pollutant water quality was investigated through studies of Daphnia magna survival following one-hour incubation with each sample. Feeding trials were carried out to determine the palatability of the duckweed while commercial nutrient analysis was used to identify if the feed was sufficiently nutritious for cattle.
Studies of the nutrient composition of pollutant samples during remediation found that the species effectively removed key nutrients from each solution for use in formation of nucleic acids, amino acids, and chlorophyll (nitrates) or for cell division promotion in roots to enhance nutrient uptake (phosphates). Such findings were supported by observations during Daphnia water quality trials with remediated samples showing higher survival rates compared to un-remediated controls. Findings from the investigation on the change in duckweed mass during remediation revealed that low concentrations of both pollutants act as suitable growth media for duckweed.
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