In The BOD5/COD ratio in the PP leachate was close to 0.1 throughout the study, whereas its average ratio in the MP leachate was 0.37 (Fig. 4). For the MP, the BOD5/COD ratio increased up to 0.74 in the fifth month, stabilizing at 0.51 ± 0.9, and then started to decrease, stabilizing at approximately 0.2 after 25 months. A low BOD5/COD ratio indicates that in the MP and PP,biodegradable organic matter is efficiently consumed in situ by the consortia of microorganisms or has been already been depleted. In the case of the Norg/N–NH4 ratio, the lowest value was observed in the leachate generated by the PP.