Effect of recirculated leachate volume on MSW degradation

Landfilling represents the most economical method for the disposal of munic ipal solid waste (MSW). After depletion of the limited volume of air availa ble in void spaces of a waste bed, decomposition in a landfill takes place under anaerobic conditions. Anaerobic digestion requires moisture and a lac k of water is generally responsible for retarding degradation of MSW in con ventional landfills. Furthermore, the moisture that may be present is seldo m uniformly distributed. Bioreactor landfills are being researched as a mea ns to provide a rapid and predictable stabilisation of waste and landfill g as production. This is achieved primarily by control and management of the liquid flow within the landfill. The moisture content of waste and moisture movement through a waste bed are two distinct factors that affect MSW decomposition. A moist environment is critical for microbial activity; and flow of moisture is essential to mobi lize nutrients and evenly distribute microorganisms through a waste bed. Th e movement of moisture through a waste bed also provides improved mass tran sfer and prevents the development of stagnant zones. Experiments were carried out to understand how the amount of recirculated l eachate effects waste degradation in coupled pairs of stabilised and fresh waste reactors, Higher recirculation rates are shown to both improve solubi lisation of fresh waste, and also establish the methanogenic microbial Copu lation more quickly. In the best case, the organic fraction of the waste wa s essentially entirely degraded within 2 months.