Suitability of Pistia stratiotes Linn. and Spirodela polyrrhiza Trev. for the Removal of Pollutants in Oil Polluted Water Bodies

Abstract

The suitability of water lettuce (Pistia stratiotes, Linn.) and greater duckweed (Spirodela polyrrhiza, Trev.) was tested under laboratory conditions in order to evaluate their potential role in the recovery of crude oil polluted water bodies. The Water Soluble Fraction (WSF) of the crude oil was prepared to concentration levels of 12.5, 25, 50 and 100 per cent. The plant number, percentage survival, dry weights and shoot/root ratio of the plants showed a significant decrease (P<0.05) with increasing concentration of the WSF. The plant number and percentage survival of S. polyrrhiza was higher than that of P. stratiotes although its percentage survival was affected at higher treatment levels. No death was recorded for S. polyrrhiza. P. stratiotes showed a sign of die back, yellowing of leaves, tip burning and eventual death at 50% and 100% exposure to the WSF. Low concentration levels of 12.5% and 25% WSF enhanced shoot growth in the plants, while high concentration levels (50% and 100% WSF) stimulated root growth. Although it showed 100% mortality on exposure to crude petroleum oil, this paper advocates biological treatment of oil polluted water bodies not only for the economic aspect but mainly for ecological reasons. The present study is relevant in the quest for environmentally friendly processes for the remediation of polluted processes.

Keywords: Pistia stratiotes, Spirodela polyrrhiza, suitability, water soluble fraction, crude oil

Discovery and Innovation Vol. 19 (2) 2007: pp. 102-107