Showing papers by "Marcelo Zaiat published in 2007"

Long-term operating performance of a poultry slaughterhouse wastewater treatment plant

Abstract: This paper evaluates the performance and process stability of a full-scale poultry slaughterhouse wastewater treatment plant in removing organic matter over a 4-year operation. The wastewater treatment system is composed of rotary and static screens, an equalization tank, a dissolved-air flotation (DAF) system and two upflow anaerobic sludge blanket (UASB) reactors. The operating strategy for UASB reactors to treat slaughterhouse wastewater involves the use of a tank to dampen fluctuations in flow and organic load, a DAF system to remove oil and grease (O&G) and suspended solids (SS) and an intermittent operation. Surface-loading rates of 1.6 ± 0.4 m 3 /m 2 h applied to the DAF system in the operation under study resulted in O&G and SS removal efficiencies of 51 ± 16% and 37 ± 16%, respectively. The organic loading rate of 1.6 ± 0.4 kg COD/m 3 day and the upflow velocities of 0.3 ± 0.1 m/h applied to the UASB reactors resulted in a similar and satisfactory performance, showing total chemical oxygen demand and soluble chemical oxygen demand removal efficiencies of 67% and 85%, respectively. Although the organic matter removal efficiencies of the treatment plant reached about 90%, the nutrients concentrations in the treated effluent pointed to the need for advanced wastewater treatment.

Kinetics of BTEX degradation in a packed-bed anaerobic reactor

Abstract: The ever-increasing diversity of industrial activity is responsible for the discharge of compounds that are toxic or difficult to degrade into the environment. Some of the compounds found in surface and ground waters, usually deriving from the contamination of oil-based products, are benzene, toluene, ethylbenzene and xylenes (BTEX). To remove these compounds from contaminated water, a bench-scale horizontal-flow anaerobic immobilized biomass reactor, containing anaerobic biomass from various sources immobilized in polyurethane foam matrices, was employed to treat a synthetic substrate composed of protein, carbohydrates and BTEX solution in ethanol, as well as a BTEX solution in ethanol as the sole carbon source. The reactor removed up to 15.0 mg/l of each BTEX compound over a hydraulic detention time of 11.4 h. A first-order kinetic model fitted the experimental data well, showing correlation coefficients higher than 0.994. The apparent first-order coefficient values, \(k_{1}^{\rm app}\), ranged from 8.4±1.5 day−1 for benzene to 10.7±1.4 day−1 for o-xylene in the presence of ethanol, protein and carbohydrates, and from 10.0±2.0 day−1 for benzene to 13.0±1.7 day−1 for o-xylene in the presence of ethanol. The BTEX degradation rates estimated here were 10- to 94-fold higher than those found in reports on microcosm studies.

Domestic sewage treatment in a pilot-scale anaerobic sequencing batch biofilm reactor (ASBBR)

Abstract: This paper presents and discusses data obtained from 125 days of operation of an anaerobic sequencing batch biofilm reactor (ASBBR) containing biomass immobilized in inert support (polyurethane foam cubes) applied for the treatment of domestic sewage. The reactor, with a total volume of 1.2 m3, was operated in 8-hour cycles treating 0.65 m3 per batch. Each batch cycle comprised feeding (2 h), reaction (5 h), discharge (0.5 h) and idle (0.5 h). The reactor took approximately 20 days to reach operational stability, confirming that anaerobic fixed film reactors require a shorter start-up period than anaerobic suspended growth reactors. Under stable operating conditions after the startup period, the mean values of COD removal efficiency and effluent total COD achieved 66% and 133 (±39) mg l−1, respectively, demonstrating the potential applicability of this reactor configuration for treating domestic sewage. Even so, a post-treatment unit is required as occurs generally when anaerobic reactors are applied for domestic sewage treatment.

Whey Treatment by AnSBBR with Circulation: Effects of Organic Loading, Shock Loads, and Alkalinity Supplementation

Abstract: The main objective of this work was to investigate the effect of volumetric loading rate (VLR), shock load, and alkalinity supplementation on the efficiency and stability of an Anaerobic Sequencing Batch Biofilm Reactor (AnSBBR) containing polyurethane foam cubes. Mixing in the reactor, which was kept at 30 ± 1°C, occurred by recirculating the liquid phase. The reactor treated 2.5 l cheese whey in 8-h cycles, at concentrations of 1, 2, and 4 g COD l−1, which corresponded to VLRs of 3, 6, and 12 g COD l−1 day−1, respectively. Application of single-cycle shock loads of 6, 12, and 24 g COD l−1 day−1 did not impair reactor performance. In addition, for VLRs of 3, 6, and 12 g COD l−1 day−1, alkalinity supplementation to the influent, at the end of each assay, could be reduced to 75, 50, and 50%, respectively, in relation to supplementation at the beginning of the assay. During reactor operation a viscous polymer-like material was formed between the polyurethane foam cubes, which increased at higher VLR. Finally, addition of salts to the influent improved reactor efficiency.

Influência da glicose sobre o consumo de fenol por Aspergillus niger an 400 em reatores em batelada

Abstract: Batch reactors were inoculated with Aspergillus niger AN 400 to remove phenol from synthetic media with and without glucose. The experiment was set by: five blank reactors (group 1) with media containing only phenol; five reactors (group 2) inoculated with fungi and with media containing only phenol; and five reactors (group 3) inoculated with fungi and with media containing phenol and glucose (5 g/L). These reactors were kept at 30°C under stirring of 200 rpm during 5 days. The mean initial concentrations of phenol and COD were 323 mg/L and 696 mg COD/L for the media without glucose, and 6058 mg COD/L for the media containing glucose. The reactors of group 2 removed 48% of phenol and 21% of COD, while the reactors of group 3 removed 100% of phenol and 93% of COD. There was no significant reduction of phenol and COD in the blank reactors. The assimilation was the main pathway of phenol removal.

Effect of bicarbonate alkalinity on gravimetric solids analysis in anaerobic wastewater treatment

Abstract: La alcalinidad bicarbonatica tiene papel fundamental en la estabilidad de reactores biologicos aplicados al tratamiento de aguas residuales, principalmente en sistemas anaerobios. Como algunas aguas residuales pueden sufrir severa acidificacion, en algunos casos es necesaria la adicion de una fuente externa de alcalinidad para que el proceso sea conducido de forma estable. En ese contexto, se evaluo el efecto de la adicion de bicarbonato de sodio sobre la determinacion de la concentracion de solidos. La metodologia consistio en la evaluacion de las concentraciones de solidos (solidos totales - ST, solidos volatiles totales - SVT y solidos fijos totales - SFT) en muestras conteniendo suero de queso y acidos volatiles (para simulacion de efluentes de reactores anaerobios). Los valores de ST, SVT y SFT fueran fuertemente influenciados, principalmente debido al aumento de los SFT. Ese efecto fue cuantificado relacionandose los valores experimentales con los teoricos, determinados por las reacciones estequiometricas de la descomposicion del bicarbonato de sodio y otros compuestos formados (acetato de sodio y propionato de sodio) con el aumento de la temperatura. Asi, como un de los principales parametros de evaluacion de sistemas de tratamiento de aguas residuales es la remocion de solidos presentes en el medio, la concentracion de solidos puede ser evaluada de forma mas adecuada teniendo en cuenta la determinacion de los solidos fijos debido a las sales inorganicas. Esa metodologia es considerada adecuada cuando se adiciona grande cantidad de alcalinizad a la agua residual.

Removal of nitrogen and organic matter in a radial-flow aerobic-anoxic immobilized biomass reactor used in the posttreatment of anaerobically treated effluent.

Abstract: This work reports on the removal of organic matter and nitrogen in a radial-flow aerobic-anoxic immobilized biomass (RAIB) reactor fed with domestic sewage pretreated in a horizontal-flow anaerobic immobilized biomass (HAIB) reactor. Polyurethane foam was used as support material for biomass attachment in both reactors. In batch experiments, a first-order kinetic model with residual concentration represented the organic matter removal rate, whereas nitrogen conversion followed a pseudo-first-order reaction in series model, with kinetic constants k1 (ammonium to nitrite) and k2 (nitrite to nitrate) of 0.25 and 6.62 h−1, respectively. The RAIB reactor was operated in continuous-flow mode and changes in the airflow rate and hydraulic retention time were found to interfere in the apparent kinetic constants to the nitritation (k1) and nitratation (k2). Nitrification and denitrification were achieved in the partially aerated RAIB reactor operating with hydraulic retention times of 3.3 h and 2.7 h in the aerobic and anoxic zones, respectively. Ethanol was added in the anoxic zone of the reactor to promote denitrification. The effluent flow of the RAIB reactor presented a COD of 52 mg l−1, and concentrations of 2 mg \( {\text{N}} - {\text{NH}}^{ + }_{4} {\text{ l}}^{{ - 1}} \), 1.24 mg \( {\text{N}} - {\text{NO}}^{ - }_{2} {\text{ l}}^{{ - 1}} \) and 3.46 mg \( {\text{N}} - {\text{NO}}^{ - }_{3} {\text{ l}}^{{ - 1}} \).

Influence of temperature on performance of an anaerobic sequencing biofilm batch reactor with circulation applied to treatment of low-strength wastewater.

Abstract: The effect of temperature on the performance of an anaerobic sequencing biofilm batch reactor (ASBBR) with liquid-phase recirculation was assessed. Assays were performed using a recirculation velocity of 0.20 cm/s, 8-h cycles, and an average treated synthetic wastewater volume of 2 L/cycle with a concentration of 500 mg of Chemical Oxygen Demand (COD)/L. Operation temperatures were 15, 20, 25, 30, and 35°C. At 25, 30, and 35°C, organic matter removal efficiencies for filtered samples ranged from 81 to 83%. At lower temperatures, namely 15 and 20°C, removal efficiency decreased significantly to 61 and 65%, respectively. A first-order model could be fitted to the experimental concentration profile values. The first-order kinetic parameter value of this model varied from 0.46 to 0.81 h1 considering the lowest and highest temperature studied. Moreover, analysis of the removal profile values allowed fitting of an Arrhenius-type equation with an activation energy of 5715 cal/mol.

Effect of bicarbonate alkalinity on gravimetric solids analysis in anaerobic wastewater treatment

Abstract: SUMMARY Bicarbonate alkalinity plays an important role in the stability of biological reactors used in wastewater treatment, primarily in anaerobic systems. As some wastewaters tend to acidify readily, addition of an external alkali source may be necessary to maintain process stability. An assessment was made of the effect of sodium bicarbonate addition on the determination of solids concentration. The methodology consisted in accompanying a series of solids concentrations (total solids, TS; total volatile solids, TVS; and total fixed solids, TFS) in samples containing cheese whey and volatile acids used to simulate anaerobic reactor effluents. TS, TVS and TFS showed to be strongly affected by NaHCO3 addition, mainly due to an increase in TFS. This effect could be quantified by relating the experimental values to the theoretical ones from the stoichiometric equations for NaHCO3 decomposition and other compounds (sodium acetate and sodium propionate) formation with temperature increase. In this way, as one of the main parameters of assessing liquid effluent treat ment systems is the reduction in solids present in the medium, the concentration of solids can be quantified more adequately by determining fixed solids from the inorganic salts present. This methodology showed to be adequate in cases where a significant amount of alkali is added.