Water-extractable components released during composting of municipal solid waste

Composting of municipal solid waste (MSW) was studied in an attempt to better understand the composting process and concomitant changes occurring in the water-soluble fraction. Composting was performed in 1 m(3) plastic boxes and the following parameters were measured in the compost liquid phase: C/N ratio, electrical conductivity (EC), pH, dissolved organic carbon (DOC), optical density and soluble nitrogen forms. The C/N ratio and DOC levels exhibited high rates of change during the first 60-70 days, then stabilized. The pH of the compost followed a typical trend during composting, reaching neutrality at the end of the process. The ammonium level peaked during the thermophilic stage, whereas during maturation the ratio between N-NO3-/N-NH4+ increased to 4. The increasing level of NO3- during the last stage of composting can be used as an indicator of compost maturity, whereas the C/N ratio can serve only as an indicator of compost stability.