Abstract
The lab-scale upflow anaerobic biofilm reactor was successfully operated for the treatment of synthetic wastewater with high nitrogen load by Anammox (anaerobic ammonium oxidation) process. During the entire period of operation, the reactor temperature was kept at 35±1°C. The operational strategy consisted of both increasing the ammonium and nitrite concentrations from 60 to 700mgN/L and from 80 to 920 mgN/L, respectively and decreasing the hydraulic retention time from 24 to 6 h, at each step. The highest achieved removal efficiency of ammonium and nitrite were 91 and 93%, respectively. Consequently, due to their acceptable performance for nitrogen removal in previous researches, modified Stover-Kincannon and Grau second-order models were used in this study. According to the experiment results, the model validity testing showed that the Stover-Kincannon model was a little more appropriate for the description of nitrogen removal in the reactor, even though both models gave high correlation coefficients (R2=0.999).
Highlights
Due to lower operation cost and energy saving, the use of biological treatment process is recommended in order to treat the effluents with high concentrations of ammonium before discharging them into water resources
Due to the gradual decrease of HRT and increase of nitrogen loading rate to the highest 5 gN/L.d, ammonium removal efficiency reduced from 93% to 86%
Due to the gradual decreasing of HRT and increase of nitrogen loading rate to the highest value, 5 g N/L d, ammonium removal efficiency reduced from 93% to 86%
Summary
Due to lower operation cost and energy saving, the use of biological treatment process is recommended in order to treat the effluents with high concentrations of ammonium before discharging them into water resources. Among the above mentioned processes, Anammox is an innovative process that was discovered in the 1990s and has shown noticeable results for the removal of ammonium and nitrogenous compounds from wastewater [3]. In this process, ammonia in the presence of nitrite as the electron acceptor oxidizes to nitrogen gas under anoxic conditions [4]. It is an autotrophic process that consumes less than 40% oxygen without requiring an organic carbon source for denitrification. It oxidizes 55-60% of ammonium to nitrite and the remaining of ammonium will be oxidized with nitrite at a reasonable time during this process [6]
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