This study investigated the effects of alkalinity on the anaerobic treatment of the
organic solid wastes collected from the kitchen of Engineering Faculty in Dokuz Eylul
University, Izmir, Turkey and the leachate characteristics treated in three simulated
landfill anaerobic bioreactors. All of the reactors were operated with leachate recirculation.
One reactor was operated without alkalinity addition. The second reactor was operated
by the addition of 3 g l-1 d-1 of NaHCO3 alkalinity to the leachate and the third
reactor was operated by the addition of 6 g l-1 d-1 NaHCO3 alkalinity to the leachate.
After 65 d of anaerobic incubation, it was observed that the chemical oxygen demand
(COD), volatile fatty acids (VFA) concentrations, and biochemical oxygen demand to
chemical oxygen demand (BOD5/COD) ratios in the leachate samples produced from the
alkalinity added reactors were lower than the control reactor while the pH values
were higher than the control reactor. The COD values were measured as 18900, 3800
and 2900 mg l-1 while the VFA concentrations were 6900, 1400 and 1290 mg l-1, respectively,
in the leachate samples of the control, and reactors containing 3 g l-1 NaHCO3 and
6 g l-1 NaHCO3 after 65 d of anaerobic incubation. The total nitrogen (TN), total
phosphorus (TP) and ammonium nitrogen (NH4-N) concentrations in organic solid waste
(OSW) significantly reduced in the reactor containing 6 g l-1 NaHCO3 by d 65. The
values of pH were 6.54, 7.19 and 7.31, after 65 d of anaerobic incubation, respectively,
in the aforementioned reactors results in neutral environmental conditions in alkalinity
added reactors. Methane percentage of the control, reactors containing 3 g l-1 NaHCO3
and 6 g l-1 NaHCO3 were 37%, 64% and 65%, respectively, after 65 d of incubation.
BOD5/COD ratios of 0.27 and 0.25 were achieved in the 3 and 6 g l-1 NaHCO3 containing
reactors, indicating a better OSW stabilization. Alkalinity addition reduced the waste
quantity, the organic content of the solid waste and the biodegradation time.