Abstract

TERREROS-MECALCO, J. et al. Anaerobic digestion of primary and secondary sludge in two serial UASB reactors. Rev. Mex. Ing. Quím [online]. 2009, vol.8, n.2, pp.153-161. ISSN 1665-2738.

The present research studies of mesophilic hydrolysis (AM) and stabilization under thermophilic methanogenic conditions (MT) for a mixture of primary sludge (PS) and secondary sludge (SS) using two serial Upflow Anaerobic Sludge Blanket reactors (UASB). The AM and MT reactors were operated at 32 ± 2 °C and 56 ± 1 °C, respectively with different rates of PS:SS in the supply, without stir or recirculation at different hydraulic retention times (HRT). The AM reactor showed the optimal results in the stage V, HRT of 2 days, solid retention times (SRT) of 18.1 for a PS:SS rate of 50:50, and volumetric loading (Bv) of 3.6 kg DQO/m3.d., and it was observed a COD removal efficiency of 56.8%, soluble COD production of 48.3%, volatile suspended solids (VSS) removal of 68.6% using a hydrolysis rate of 0.16 kg/m3.d. The MT reactor showed the optimal stabilization for HRT on the 6^th day of operation, methane (CH₄) production of 107.7 mL CH₄/ Kg VSS_removed, VSS removal of 66%, faecal coliform elimination of 8.5 Log₁₀ and reduction for helminth eggs of 85%. Partition in two stages of the sludge anaerobic treatment allowed us to achieve higher hydrolysis of the organic matter with lower SRT than those reported for completely stirred reactors; furthermore reduction of helminth eggs was similar to other previous reports.

Keywords : UASB; sludge; hydrolysis; pathogens; stabilization.

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