Pages: 12-22

Abstract

When being present on the organic matters in the anoxic conditions, several bacteria do this conversion (denitrification). The current study aimed at the investigation of the effects of a useful and cost-effective method for nitrogen removal. In the current study, through creation of the anaerobic respiration conditions (anoxic) in the second line of aeration unit with a high SRT, and an MLVSS rate of 4000mg/l, in the HRT (Hydraulic Retention Time) of 8 to 36 hours, in the wastewater treatment plant with the Extended Aeration Activated Sludge by the use of heterotrophic bacteria (Pseudomonas and alcaligenes), was proposed and analyzed. Many of different heterotrophs are responsible for anaerobic denitrification, which have been identified in the sludge from the household waste wells (soak away). The findings show a decrease in COD and BOD by more than 93% and 96%, respectively, and nitrogen and phosphorus removal efficiency up to 90% and 87%. The nitrification was completely done. Among all the bacteria separated in the current study, the Pseudomonas with a rate of 36.2% and Alacaligenes with a rate of 29.8%, were identified as the dominant species. The results of the current study showed that the advantages of the use of mentioned method would lead to the removal of the organic matters and nutrients, and activity of denitrifying bacteria, besides a significant reduction in algae growth. According to the results of the analysis by the T-Test, with two independent groups and in the significance level of 5%, there is a significant different between the aerobic and anoxic groups in terms of NH4 and NO2 amount, while in the significance level of 10%, there is a significant difference between the two groups in NO3 amount.