OPTIMISED MANAGEMENT OF SEMI-AEROBIC LANDFILLING UNDER TROPICAL WET-DRY CONDITIONS

Abstract

The processes involved in semi-aerobic landfills are heavily influenced by local climate conditions and waste composition. In particular, when considering rainfall seasonality in a tropical climate, the lack of moisture during the dry season and heavy rainfalls during the wet season may negatively affect biodegradation processes and landfill emissions. The aim of the present study was to investigate the performance of semi-aerobic landfill under tropical dry-wet climate conditions and to assess the potential benefits afforded by appropriate management of water input when operating the landfill by overlaying a new layer of waste in each climate season. Six lab-scale lysimeters were operated in two phases to reproduce, on two subsequent waste layers, a sequence of dry and wet tropical seasons: two with an initial dry phase, two with an initial dry phase under controlled watering and two with an initial wet phase, during which leachate was stored to allow recirculation during the subsequent dry phase. In each pair of lysimeters one was filled with low putrescible content waste and the other with high putrescible content waste. Although appropriate management of water input significantly improved landfill performance under dry climate conditions, the overlaying of a new layer of waste in each climate season played a fundamental role in ensuring good stabilisation over the one year simulation period; following stabilisation, the landfill bottom layer acts as an internal attenuating biological filter. In particular, under initial dry conditions, final BOD COD and ammonia values detected were below 20mgO2/L, 200mgO2/L, and 30mgN/L, respectively.