Journal of School of Public Health and

Background and Aim: High concentrations of organic compounds and ammonia and entry of toxic pollutants lead to a low efficiency of direct biological treatment of landfill leachate. The aim of this study was to determine the efficiency of a repeated fed-batch biological reactor with powdered active carbon (PAC) for landfill leachate treatment.

Methods and Materials: Raw leach ate was pretreated by coagulation and flocculation processes and, then, the ammonia was removed by air stripping at a high pH, before biological treatment. The pretreated leach ate was treated bio-treated in an aeration tank by the repeated fed-batch method. Three cycles of 1×40, 5×8, and 4×10 hours were attempted in the absence and presence of 2 g PAC /L.

Results: Results indicate that the presence of PAC increased the COD removal efficiency significantly. The initial COD effluent was 3900 mg/L. Its values were 169 mg/L and 622 mg/L in the presence and absence of 2 g/L PAC, respectively, for the cycle of 5×8 h.

Conclusion: Based on the results of this study and findings of other investogations in this field, it can be concluded that repeated fed-batch bio-reactor has is quite effective for treatment of pretreated leachate.

Background and Aim: Problems related to conventional Fenton oxidation, including neccesity of having a low pH and production of considerable amounts of sludge, have prompted researchers to consider chelating agents to improve the pH operating range and iron nano-oxide particles to reduce excess sludge. The main objective of this study was to remove pyrene from contaminated soils by a modified Fenton oxidation method  at neutral pH.

Materials and Methods: Experiments were conducted using various concentrations of H2O2 (0-500 mM), iron nano-oxides (0-60 mM), reaction times (0.5-24 hours) and several chelating agents, namely, sodium pyrophosphate, ethylene diamine tetra-acetic acid, sodium citrate, fulvic and humic acids, to eliminate pyrene from soil (concentrations of 100-500 mg/kg).

Results: The efficiency of removal of pyrene at an initial concentration of 100 mg/kg was 99 % at the following reaction conditions: H2O2 and iron nano-oxide concentrations of 300 mM and 30 mM, respectively pH=3 and a reaction time of 6 hours. The initial pyrene concentration of 100 mg/kg decreased to 7 mg/kg at optimum conditions using sodium pyrophosphate as the chelating agent at pH 7.    

Conclusion: The modified Fenton oxidation method, using iron nano-oxide at optimum conditions as defined in this research, is an efficient alternative for chemical remediation or pre-treatment of soils contaminated wih pyrene at neutral pH.