Plants' use of leachate derived from municipal solid waste

Leachate was collected from a watertight pit at a landfill center dealing m ainly with household refuse and plant waste. This effluent was characterize d by a moderate organic matter content, a pH slightly higher than neutral a nd strong electrical conductivity. This latter was due to the presence of c hlorides, Na, K, and ammonium. The organic content could be divided into tw o fractions: Fraction A consisting of large molecules (5000 Da and above) a nd Fraction B of smaller (between 300 to 1000 Da), more acidic molecules. T he presence of phenols (sinapic acid, acetosyringone, and pyrogallol) could be identified in the leachate as a whale. A biological treatment of this l eachate, involving methanization followed by aerated lagooning, was set up on the site: this led to a reduction of nearly 60% in the organic content a nd almost total elimination of the ammonium. This treatment was not however sufficient to allow direct evacuation of the resulting effluent into the s urface ground water. As heavy metals were absent from this effluent, the le achates from this landfill site could possibly be envisaged in the fertiliz ation of sop-grown crops or for furrow irrigation-fertilization of tree pla ntations. The effect of irrigating soil-grown plants with a solution of lea chate was examined using pots of ryegrass (Lolium sp.). Application of solu tions containing dilutions of 1 to 400 mL L-1 of this effluent had a highly favorable effect on plant growth. Toxicity phenomena were apparent above t his concentration. The optimum effect on ryegrass growth, under the conditi ons of this trial, was obtained by watering each pot with 30 mL of a soluti on containing 400 mt L-1 of leachate, every 2 d. This solution improved wat er and N nutrition in these plants.