Contribution of Azolla filiculoides to hydrazine elimination from water

Abstract

In this research we report the significant effect of the floating water fern Azolla filiculoides on the elimination of hydrazine (N2H4) from water, which is a remarkable role for an aquatic plant. Hydrazine is a highly toxic compound for human health and biodiversity with wide industrial applications. In search of a practical way for hydrazine removal from an industrial wastewater, we studied the possible ability of certain aquatic lower plants to consume hydrazine. In greenhouse experiments, algal samples including Cladophora glomerata, Cosmarium sp. and Chlorella sp. did not show a significant effect on the rate of hydrazine elimination from water. However, A. filiculoides showed considerable growth when using hydrazine as the sole source of nitrogen. It was able to tolerate up to 4 mg/l hydrazine in the nutrient solution. During more than one month at the scale of 1/1000, Azolla removed hydrazine from boiler blowdown in the real conditions of a combined-cycle power plant. To our knowledge, this is the first observation of hydrazine consumption by a eukaryotic structure. Although we have discussed some possibilities, the exact mechanism of the process remains to be uncovered. On the other hand, considering the well-known abilities for bioremediation of a large number of contaminants from water, Azolla would be able to work as part of a cost effective system for remediation of hydrazine along with many other pollutants from different kinds of contaminated water. However, using Azolla in a hydrazine remediation system needs detailed feasibility studies to take various considerations into account.