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: Formaldehyde is an organic chemical with widespread applications as a raw material in many industries. Industrial effluents with high contents of formaldehyde should be treated because of their carcinogenic and mutagenic effects. The objective of this study was to determine the efficacy of the anaerobic sequence batch biofilm reactor (ASBBR) for formaldehyde biodegradation.

Materials and Methods: A laboratory-scale ASBBR with a total volume of 6 liters was used.  The efficacy of the reactor was determined in 9 stages with organic loading rates of 0.54 to 7.09 Kg COD/m³.d.

Results: The best removal efficiency for COD and formaldehyde were 94% and 99%, respectively, with an organic loading of 0.54 KgCOD/m³.d.The lowest efficiencies were 48% and 63.1%, respectively, with an organic loading of 7.09 KgCOD/m³.d.

Conclusion: Based on the findings, it can be concluded that ASBBR is a viable, efficient and reliable technology for treatment of industrial wastewaters containing formaldehyde.

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.