Use of aerobic granules for treating synthetic high-strength ammonium wastewaters

Abstract

In this work, two identical sequencing batch reactors (SBRs) with mature aerobic granules were utilized to treat synthetic high-strength ammonium wastewaters with chemical oxygen demand (COD)/total nitrogen (TN) ratios of 3.9–6.9. The contributions of various mechanisms to the removal of ammonium were determined. Ammonium levels of 600–2000 mg-N l−1 had little adverse effect on the COD removal rate (91.6%–95.3%) with an influent COD of 4490–9860 mg l−1. The TN removal rate was slightly reduced from 71.3% to 59.6% as the influent ammonium concentration was increased from 600 to 2000 mg-N l−1. Experimental results indicated that aerobic granules removed 94.5% of COD and 59.6% of TN in the treatment of synthetic high-strength wastewater (9860 mg-COD l−1 and 2000 mg -N l−1) during a 12 h cycle. Granular adsorption, air stripping and conversion by nitrification/denitrification were responsible for removing 9%, 15% and 76%, respectively, of the total removed -N. Dissolved oxygen (DO) was a useful process indicator of the biological reactions in the treatment of high-level ammonium wastewaters.