Plants' use of leachate derived from municipal solid waste.

Leachate was collected from a watertight pit at a landfill center dealing mainly with household refuse and plant waste. This effluent was characterized by a moderate organic matter content, a pH slightly higher than neutral and strong electrical conductivity. This latter was due to the presence of chlorides, Na, K, and ammonium. The organic content could be divided into two fractions: Fraction A consisting of large molecules (5000 Da and above) and Fraction B of smaller (between 300 to 1000 Da), more acidic molecules. The presence of phenols (sinapic acid, acetosyringone, and pyrogallol) could be identified in the leachate as a whole. A biological treatment of this leachate, involving methanization followed by aerated lagooning, was set up on the site: this led to a reduction of nearly 60% in the organic content and almost total elimination of the ammonium. This treatment was not however sufficient to allow direct evacuation of the resulting effluent into the surface ground water. As heavy metals were absent from this effluent, the leachates from this landfill site could possibly be envisaged in the fertilization of soil-grown crops or for furrow irrigation-fertilization of tree plantations. The effect of irrigating soil-grown plants with a solution of leachate was examined using pots of ryegrass (Lolium sp.). Application of solutions containing dilutions of 1 to 400 mL L(-1) of this effluent had a highly favorable effect on plant growth. Toxicity phenomen a were apparent above this concentration. The optimum effect on ryegass growth, under the conditions of this trial, was obtained by watering each pot with 30 mL of a solution containing 400 mL L(-1) of leachate, every 2 d. This solution improved water and N nutrition in these plants