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AGROIWATECH Résumé de rapport

Project ID: ICA2-CT-2002-10010
Financé au titre de: FP5-INCO 2
Pays: Bosnia and Herzegovina

Assessment of the effect of degree of wastewater acidification on the development of anaerobic granular sludge from low grade seed sludge

The effect of the rate of acidification of the influent wastewater onto performance of anaerobic digestion of agro-industrial wastewater was evaluated. Three UASB reactors (25 litres each) were inoculated with low-grade seed sludge and subsequently fed with a synthetic wastewater consisting of sucrose, volatile fatty acids, nutrients and trace elements. The volatile fatty acids (VFA) were acetate, propionate and butyrate in the ratio 2:1:1 (based on COD).

The sucrose: VFA ratio differed in each reactor; . 1:10, 1:1 and 10:1 respectively. The reactors were started at a low loading rate (0.9-1.2 kg/m3day), that was being increased slowly to 4 gCOD/Lday. In order to maintain a required up-flow velocity and promote mixing and sludge bed expansion, re-circulation was introduced. Up-flow velocity was gradually increased. The operational temperature was 300C. After 163 days of continuous experiment the following amount of biomass was found: UASB 1 reactor - 27.1 g/L; UASB 2 33.7 g/L and UASB 3 -35.4 g/L.

The lowest CODVFA removal effect was estimated in UASB 1 reactor, where the VFA concentration were lower in comparison with the other two reactors. CODVFA removal effects in the reactors with 50 and 90% of VFA were very high: UASB 2 reactor (50% VFA) - 93.6% and UASB 3 reactor (90% VFA) - 96.3%. The sludge particles showed a great variety with prevailing fraction of small particles.

Reported by

Milosa Obilica, 51
Bosnia and Herzegovina