Granulation in high-load denitrifying upflow sludge bed (USB) pulsed reactors

• Published in: Water research (Oxford) Vol. 40; no. 5; pp. 871 - 880
• Main Authors: Franco, A., Roca, E., Lema, J.M.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.03.2006; Elsevier Science
• Subjects: activated sludge; Ammonia - analysis; Ammonia - metabolism; anaerobic digesters; anoxic upflow sludge bed; Applied sciences; Biological and medical sciences; Biological treatment of waters; Biomass; Biotechnology; Carbon Dioxide - analysis; Denitrifying bacteria; effluents; Environment and pollution; equipment performance; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Gases - analysis; General purification processes; Glucose - metabolism; Granulation; granules; Industrial applications and implications. Economical aspects; Methane - analysis; methanogenic granules; Nitrites - analysis; Nitrites - chemistry; Nitrogen - chemistry; nitrogen loading rate; organic loading rate; Oxygen; Pollution; pollution control; Pulsation; Sewage - chemistry; Time Factors; Upflow sludge bed; Waste Disposal, Fluid - instrumentation; Waste Disposal, Fluid - methods; Wastewaters; water pollution; Water treatment and pollution; Upflow sludge bed; Denitrifying bacteria; Granulation; Pulsation; Anaerobiosis; Activated sludge; Bioreactor; Methanogenesis; Pulsation Upflow sludge bed Denitrifying bacteria Granulation; Denitrification; Upflow anaerobic sludge blanket reactor; Waste water purification; Pulsating flow; Biological purification
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2005.11.044

In this work, the effect of the application of a pulse system to anoxic upflow sludge bed (USB) denitrifying reactors for enhancing sludge granulation was studied. In all, three 0.8 L reactors (two operated with flow pulsation, P1 with effluent recycling and P2 without recycling, and one without pulsation and effluent recycling, no pulsation (NP)) were fed with a mixture of NaNO 3 and glucose and inoculated with methanogenic granular sludge. The organic loading rate (OLR) and the nitrogen loading rate (NLR) were progressively increased and, at the end of the experiment, extremely high values were obtained (67.5 kg COD/m 3 d and 11.25 kg N ‐ N O 3 - /m 3 d). Ammonia and nitrite accumulation in reactor NP were important in the maturation stage, decreasing the denitrification efficiency to 90%, while in reactor P1 only low nitrite values were obtained in the last few days of the experiment. In reactor P2, nitrogen removal was 100% most of the time. Several operational problems (flotation and the subsequent wash out of biomass) appeared in the NP reactor when working at high denitrifying loading rates, while in reactors P1 and P2 there were no notable problems, mainly due to the good characteristics of the sludge developed and the efficient degasification produced by the pulsing flow. The sludge formed in the NP reactor presented a flocculent structure and a total disintegration of the initial methanogenic granules occurred, while a small-sized granular biomass with a high specific density was developed in the pulsed reactors due to the shear stress produced.