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

摘要

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 chemical oxygen demand (COD) in the range of 3000-6000 mg/L. It was operated at 26-29 °C. After the formation of granules, it was possible to gradually increase the organic loading rate (OLR) up to 11.9 kg COD/m~3.d. 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. The 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. Scanning and transmission electron microscopy 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.