Pre and post-granulation performance of UASB System treating high-strength industrial effluent

Performance of a high-rate anaerobic treatment system prior to and after the formation of granular sludge was investigated. The 500-L UASB pilot was set up to receive effluent from a medium-size traditional slaughterhouse without blood recovery. The system was inoculated with mesophilic municipal anaerobic digested sludge for the startup and was fed influent with a total COD in the range of 3000-5000 mg/L. It was operated at 26-29 oC. After six months of operation, indications of granule formation were observed. It was possible to increase OLR from 14 to 25 kg COD/m.d (SLR of 2.3 kg COD/kg VSS.d) with the onset of granulation. At an upflow velocity of 0.8-1 m/h superior COD removal efficiencies of up to 85% was achieved with reduced potential of sludge washout. These granules were dark brownish with a diameter of 1-4 mm and a settling velocity of 20 m/hr. SS and VSS of the granules’ layer were 55-68 and 45-57 g/L, respectively with a specific gravity of 1.3. SEM and TEM analyses indicated rod-shaped and filamentous Methanothrix bacteria as well as Methanosarcina cocci aggregates. Microstructures were an intertwined syntropic association between acetogenic and methanogenic microbial populations with diverse morphologies. X-ray analysis of mineral contents showed a high calcium phosphate apparently related to exracellular polymers of the shell structure. INTRODUCTION Several studies has been conducted to evaluate anaerobic degradation of slaughterhouse effluent but none report indications of granule formation. Martinez et al (1995) reports 82% of soluble COD removal at OLR of 1.8. In another study, Ruiz, et. al(1997) report better performance of UASB at OLRs of 1-6.5 compared to anaerobic filters. Low organic loadings reported may be due to the absence of high activity granules. This study was undertaken to evaluate pre and post granulation performance of UASB system treating high-strength effluent from a traditional salughterhouse with no provision for blood recovery. MATERIALS AND METHODS The 500-L effective volume square (50 cm x 50 cm) Plexiglas pilot used in this study (figure 1) was set up downstream of a medium-size traditional slaugherhouse without blood recovery. Nine sampling ports (20 and 30-cm apart at bottom and top, respectively) were provided to quantify sludge characteristic at different elevations along the reactor. Routine analyses were performed using procedures outlined in Standard Methods (APHA, 1985). 1 Author to whom correspondence should be made.