Landfill Leachate Recirculation Methods Effects on Leachate Flow Patterns and Degradation
AbstractLeachate recirculation increases moisture content and flow and thereby increases biodegradation of solid organic materials and of the leachate. Channeling, the rapid confined flow through narrow pores, leads to rapid discharges and creates large dry pockets in landfills. An automated moisture flow measurement system was installed to compare leachate flow patterns and leachate COD degradation in four cells. In two cells leachate was recirculated in pulses of 128 L every two weeks. The same volume was recirculated continually in the other two. The flow patterns evolved quickly and stayed in the same locations throughout the eighteen-month test period. Continual recirculation cells did not exhibit higher average flows, but the variation of flows was much lower than in pulse-recirculation cells. Continually recirculated leachate produced more consistent flows throughout the cross-section of the waste. No difference in the COD degradation rates was demonstrated, possibly because of dilution effects of make-up water. Neither recirculation method prevented channeling. New approaches to moisture content measurement and to leachate recirculation must be developed to achieve higher and more consistent moisture contents and flows in heterogeneous waste layers.
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