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Effect of centrifuged and non-centrifuged sludge on UASB start-up
Conference paper   Open access

Effect of centrifuged and non-centrifuged sludge on UASB start-up

D.O. Tenorio, Goen Ho and Robyn Gibbs
17th Biennial Conference of the International Association on Water Quality. Water Quality International '94 (Budapest, Hungary, 24/07/1994–30/07/1994)
25/07/1994
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Abstract

UASB start-up abattoir stabilization pond sludge centrifuged non-centrifuged sludge volatile fatty acids Environmental engineering Waste management, reduction, reuse and recycling Water and waste services Environmentally sustainable commercial services and tourism
The start-up of UASB reactors using non-centrifuged and centrifuged waste stabilization pond sludge was studied to determine whether there was any advantage in the use of concentrated sludge. Two identical reactors were filled with 30 g VSS/L of reactor; one with non-centrifuged and the other with centrifuged sludge. A mixture of acetic, butyric and propionic acid was used as substrate. The reactors were operated in 3 stages of one week each with decreasing hydraulic residence time and attained a final loading of 16 g COD/L of reactor-day over a period of 21 days. The sludge performance was assessed based on acid degradation, COD reduction and methane production. Severe sludge washout occurred early in stage I for non-centrifuged sludge, while for centrifuged sludge the severe washout took place later in stage II. VSS retained in the reactor was higher for non-centrifuged sludge at the end of stage III. The specific activity of the sludge at the end of stage 3 was 0.83 g COD removed/g VSS (13.4 g COD removed/L of reactor-day) for non centrifuged and 0.77 g COD removed/g VSS (11.7 gCOD removed/L of reactor-day) for centrifuged sludge. The difference in sludge performance was due to the low degradation of propionic acid in stage III for centrifuged sludge. The potential advantage of using centrifuged sludge over non-centrifuged sludge in UASB start-up was the smaller initial volume occupied inside the reactor, which reduced washout in the initial stage. Washout at a later stage when loading was increased appeared to preferentially remove propionic degrading bacteria.

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