NITROGEN AND PHOSPHOROUS REMOVAL FROM LEACHATE BY DUCKWEED (Lemna minor)

Two separate experiments were conducted during the months of June and September, 2014 to investigate the nutrient (nitrogen and phosphorous) removal from leachate by growing duckweed, Lemna minor in various leachate dilutions under natural climatic conditions of Islamabad, Pakistan. The highest uptake of nitrogen and phosphorous by duckweed was 95% and 90%, respectively, whereas the highest growth rate of duckweed was 6.4 g.m(-2).day(-1) during both experiments. The highest rates of nitrogen and phosphorous removal from leachate media were 380 and 200 mg.m(-2).day(-1), respectively, during both experiments. Nutrient uptake by duckweed and its growth rate was rapid at more diluted leachate whereas the nutrient removal rates from leachate media were higher in more concentrated leachate. The duckweed growth and its nutrient uptake ability under natural climatic conditions were directly affected by seasonal climatic variations. Relatively higher temperature and more intense solar radiation were more favorable for the duckweed growth and its nutrient uptake ability. Both parameters can be improved by pre-acclimation of duckweed with leachate which prevents the lag phase of the duckweed growth.