The effects of aerobic/anoxic period sequence on aerobic granulation and COD/N treatment efficiency

• Published in: Bioresource technology 2013-11, Vol.148, p.149-156
• Main Authors: Erşan, Yusuf Çağatay, Erguder, Tuba Hande
• Format: Article
• Language: English
• Subjects: Aerobiosis; Ammonia - analysis; Anaerobiosis; Biological and medical sciences; Biological Oxygen Demand Analysis; Bioreactors - microbiology; Denitrification; Extracellular polymeric substance (EPS); Extracellular Space - chemistry; Fundamental and applied biological sciences. Psychology; Granular materials; Granulation; Granule; Granules; Hydrogen-Ion Concentration; Inhibition; Nitrification; Nitrogen - isolation & purification; Nitrogen removal; Particle Size; Polysaccharides - chemistry; Reactors; Sewage - chemistry; Simultaneous nitrification–denitrification; Sludge; Sulfates; Sulfates - analysis; Sulfides; Sulfides - analysis; Water Purification - methods
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2013.08.096

•Aerobic granules were developed by both anoxic–aerobic and aerobic–anoxic periods.•More stable granules of greater sizes were developed at anoxic–aerobic period.•Post-anoxic application resulted in granule disintegration due to lack of carbon.•Sulfide and NH3–N inhibited both COD and TAN removal efficiency.•Sulfide-related inhibition is more severe for TAN oxidation. The effects of period sequence (anoxic–aerobic and aerobic–anoxic) on aerobic granulation from suspended seed sludge, and COD, N removal efficiencies were investigated in two sequencing batch reactors. More stable granules with greater sizes (1.8–3.5mm) were developed in R1 (anoxic–aerobic sequence). Yet, no significant difference was observed between the reactors in terms of removal efficiencies. Under optimum operational conditions, 92–95% COD, 89–90% TAN and 38–46% total nitrogen removal efficiencies were achieved. The anoxic–aerobic period sequence (R1) resulted in almost complete denitrification during anoxic periods while aerobic–anoxic sequence (R2) led to nitrate accumulation due to limited-carbon source and further granule disintegration. NH3–N concentration of 15–28mg/L was found to inhibit COD removal up to 30%. This study also revealed the inhibitory sulfide production during anoxic periods. Sulfate concentration of 52.6–70.2mg/L was found to promote sulfate reduction and sulfide generation (0.24–0.62mg/L) which, together with free-ammonia, inhibited TAN oxidation by 10–50%.