The effect of operational conditions on the hydrodynamic characteristics of the sludge bed in UASB reactors

• Published in: Water science and technology Vol. 64; no. 9; pp. 1935 - 1941
• Main Authors: Leitão, R C, Santaellla, S T, van Haandel, A C, Zeeman, G, Lettinga, G
• Format: Journal Article
• Language: English
• Published: England IWA Publishing 01-01-2011
• Subjects: Activated sludge; afvalwaterbehandeling; anaerobic treatment; anaërobe behandeling; Bioreactors; Chemical oxygen demand; design; Evaluation; expansie; expansion; expansion characteristics; geactiveerd slib; granular sludge; Hydraulic retention time; Hydraulic shock; Hydraulics; hydrodynamic dispersion; Hydrodynamics; hydrodynamische dispersie; Influents; Kinetics; Mathematical models; Pilot Projects; purification plants; Reactors; retentie; Retention; Retention time; settleability; settling characteristics; sewage; Sewage - analysis; Shock loads; slibzuivering; Sludge; Sludge bed; Sludge bed reactors; sludge treatment; Upflow anaerobic sludge blanket reactors; velocity; volume; volume index; waste water treatment; Wastewater; Wastewater treatment; Water Purification - instrumentation; Water Purification - methods; zuiveringsinstallaties
• ISSN: 0273-1223; 1996-9732
• DOI: 10.2166/wst.2011.628

This work aims to evaluate the hydrodynamic properties of the sludge bed of Upflow Anaerobic Sludge Blanket (UASB) reactors based on its settleability and expansion characteristics. The methodologies used for the evaluation of the settleability of aerobic activated sludge, and for the expansibility of a sludge bed of Expanded Granular Sludge Bed reactors and Fluidised Bed Reactors were adapted and applied to the particular characteristics of the sludge of UASB reactors. An easy-to-build experimental set-up was developed to assess the parameters necessary for the equations of settleability and of expansibility. The results obtained from the sludges of seven differently operated reactors show that, for the treatment of low strength wastewater, settleability increased and expansibility decreased at decreased hydraulic retention time, from 6 to 1 h, and/or increased influent concentrations, from 136 to approximately 800 mg chemical oxygen demand/L. The results also show that it is useless to design an UASB reactor with a longer hydraulic retention time to cope with hydraulic shock loads, as a more expansible sludge will develop at such condition.