MicrosoftInternetExplorer4
Background and Objectives: Contamination of drinking water sources with nitrate may
cause adverse effects on human health. Due to operational and maintenance
problems of physicochemical nitrate removal processes, using biological
denitrification processes have been performed. The aim of this study is to
evaluate nitrate removal efficiency from drinking water using autotrophic
denitrifying bacteria immobilized on sulfur impregnated activated carbon in a
fluidized bed bioreactor.
Materials and Methods: After impregnating activated carbon by sulfur as a microorganism carriers and
enrichment and inoculation of denitrifying bacteria, a laboratory-scale
fluidized bed bioreactor was operated. Nitrate removal efficiency, nitrite,
turbidity, hardness and TOC in the effluent were examined during the whole experiment
under various conditions including constant influent nitrate concentration as
90 mg NO3--N/l corresponding to different HRT ranging from 5.53 to 1.5 hr.
Results: We found
that the denitrification rates was
depended on the hydraulic retention time and the nitrate removal efficiency was
up to 98% and nitrite concentration was
lower than 1mg/l at optimum HRT=2.4 hr respectively. Moreover, there was no
difference in hardness between influent and effluent due to supplying sodium
bicarbonate as carbon source for denitrifying bacteria. However pH, TOC, hardness, and turbidity of
the effluent met the W.H.O guidelines for drinking water.
Conclusion: This
study demonstrated that an innovative carrier
as sulfur impregnated activated carbon could be
used as both the biofilm
carrier and energy source for
treating nitrate contaminated drinking water in the
lab-scale fluidized bed bioreactor.
