Inorganic Solids Development in a Pilot-Scale Anaerobic Reactor Treating Municipal Solid Waste Landfill Leachate

A 30-L hybrid upflow anaerobic sludge bed filter (UASBF) reactor was operated for 9 months on-site at a municipal solid waste landfill in western Massachusetts. Total chemical oxygen demand (COD) removals exceeded 85% at organic loading rates as great as 10${\rm kg}/{\rm m}^{3}\cdot {\rm d}$. However, periodic monitoring of sludge profiles in the unpacked region indicated that the granular sludge bed was becoming compacted and mineralized. After 9 months of operation, total solids concentrations were approximately 450 g/kg, with approximately 80% of the total solids being fixed. Excessive inorganic scale accumulation on the interior reactor surfaces resulted in operational problems, and forced the eventual shutdown of the reactor. Evidence of reduced sludge activity resulting from the presence of metal precipitates indicates that pretreatment for metals removal is necessary prior to anaerobic treatment.