Eugenio Foresti

Treatment of Domestic Sewage in Horizontal-Flow Anaerobic Immobilized Biomass (HAIB) Reactor

This paper focuses on the evaluation of the start-up period and the performance of a pilot-scale horizontal-flow anaerobic immobilized biomass (HAIB) reactor treating pre-screened domestic sewage. The pilot-scale HAIB reactor comprises a 14.5 cm internal diameter PVC tube 14.4 m long divided into five stages of 2.88 m each. Polyurethane foam cubic matrices with 1 cm sides were used as support for biomass immobilization. The reactor was operated at the mean hydraulic detention time of 4.3 hours and the experimental results presented refer to 15 weeks of operation at mean sewage temperature of 25°C and mean liquid flow rate of 20 l h−1. The mean chemical oxygen demand (COD) of the sewage, based on composed samples, was found to be 350 mg l−1. A short start-up period lasting nearly 8 weeks was observed by monitoring several parameters such as COD, biogas composition, methane concentration and total volatile acid (TVA) concentration. By the end of the start-up period onward, the effluent COD attained approximately constant values of 100 mg l−1 and 75 mg l−1 for non-filtered and filtered samples.

Kinetics, Mass Transfer and Hydrodynamics in a Packed Bed Aerobic Reactor Fed with Anaerobically Treated Domestic Sewage

This study presents an assessment of the kinetic, mass transfer and hydrodynamic parameters of a pilot-scale fixed bed reactor containing immobilized biomass in polyurethane matrices and fed with the effluent of a horizontal-flow fixed bed anaerobic reactor, which was used to treat domestic sewage. It was found that the liquid-solid and intra-particle mass transfer resistances significantly affected the overall oxygen consumption rate and that mechanical agitation could minimize such resistances. The volumetric oxygen transfer coefficient (kLa) values for superficial air velocities between 8.4 cm min&minus1 and 57.0 cm min&minus1 varied from 20.8 h&minus1 to 58.8 h&minus1 for tap water, and 16.8 h&minus1 to 53.0 h&minus1 for the anaerobic pre-treated effluent. The intrinsic oxygen uptake rate was estimated to be 19.9 mgO2 gVSS&minus1 h&minus1. A first-order kinetic model with residual concentration was considered to adequately represent the COD removal rate, whereas nitrogen conversion was considered to be well represented by a model of pseudo-first-order reaction in series. It was also found that the ammonium conversion to nitrite was the limiting step of the overall nitrogen conversion rate. The hydrodynamic behavior of the reactor was represented by three to four completely mixed reactors in series.

Remoção de etanol e benzeno em reator anaeróbio horizontal de leito fixo na presença de sulfato

In this study it is reported the operation of a horizontal-flow anaerobic immobilized biomass (HAIB) reactor under sulfate-reducing condition which was also exposed to different amounts of ethanol and benzene. The HAIB reactor comprised of an immobilized biomass on polyurethane foam and ferrous and sodium sulfate solutions were used (91 and 550 mg.l-1, respectively), to promote a sulfate-reducing environment. Benzene was added at an initial concentration of 2.0 mg.l-1 followed by an increased to 9 e 10 mg.l-1, respectively. Ethanol was added at an initial concentration of 170 mg.l-1 followed by an increased range of 960 mg.l-1. The reactor was operated at 30 (± 2) oC with hydraulic detention time of 12 h. Organic matter removal efficiency of 90% with a maximum benzene degradation rate of 0.07 mg benzene.mg-1VSS.d-1. Thus, this work corroborate the data obtained for Cattony et al (2005) and also demonstrate that compact units of HAIB reactors, under sulfate reducing conditions, are a potential alternative for in situ aromatic compounds bioremediation.