Biological nutrient removal in sequencing batch reactor with different number of steps.

Nutrient removal from synthetic wastewater was carried out by using a labscale sequencing batch reactor. Three different operations consisting of different numbers of steps were tested and their performances were compared. These operations were the three-step operation consisting of anaerobic(An)/anoxic(Ax)/oxic(Ox) steps; the four-step (An/Ox/Ax/Ox), and the five-step (An/Ax/ Ox/Ax/Ox) operations. Effects of number of operating stages and the total cycle time on COD, nitrogen (NH₄-N, NO₃-N) and phosphate (PO₄-P) removal from synthetic wastewater were investigated. Experiments were carried out with a constant sludge age of 10 days. The highest nutrient removals were realized by using the five-step operation with percent COD, NH₄-N, NO₃-N and PO₄-P removals of 94%, 90%, 64% and 57%, respectively. Re-moval efficiencies of COD and NH₄-N in three- and four-step operations were slightly higher than those of the five-step operation However,NO₃-N and PO₄ -P removal efficiencies obtained by the five-step operation were clearly higher than those for the other operations. Therefore, the five-step operation with 10.5 h overall cycle time was selected as the most appropriate one for effective nutrient removal. [ABSTRACT FROM AUTHOR]