ABSTRACT Nitrogen removal via nitrite allows operational cost reduction in wastewater treatment o... more ABSTRACT Nitrogen removal via nitrite allows operational cost reduction in wastewater treatment of effluents with a low COD/N-NH4+ ratio, due to lower oxygen requirements for partial nitrification and a further diminishing in requirements of the external carbon source for the denitrification step. Two nitrifying systems - a suspended activated sludge (AS) reactor, and an airlift biofilm (AB) reactor-were compared to determine the best alternative for obtaining a maximum nitrite buildup. Both systems were operated under similar operational conditions; synthetic feed of ammonia nitrogen was applied to both reactors, at an ammonia loading rate (ALR) of 3.3 kg N-NH4+/m(3) and an hydraulic retention time of 4.3 h. Nitrite accumulation was studied by means of controlling dissolved oxygen (DO) concentration, keeping both pH and temperature constant. Similar results were obtained in both systems. In the activated sludge reactor maximum nitrite accumulation was achieved at 0.7 and at 3.5 mg DO/L in the airlift reactor. The obtained results showed that at a similar percentage of nitrite accumulation, the K(L)a value of the airlift reactor was always 3.6 times higher than the value obtained in the activated sludge reactor; however, the airflows required were similar in both reactors. The operation of nitrifying systems (biofilm and suspended biomass reactors) with low oxygen concentration to obtain nitrite accumulation make possible a decrease of required airflow, even at small nitrite accumulation. Airflow savings of 38 and 58% were obtained for the activated sludge reactor and the airlift reactor, respectively, at 15% of nitrite accumulation. When 40% of nitrite accumulation was detected in the activated sludge reactor and the airlift reactor, a savings of 80% and 65% were obtained, respectively.
A new technique for measuring the size distribution of anaerobic granular sludge, which involves ... more A new technique for measuring the size distribution of anaerobic granular sludge, which involves the use of digital image analysis, is presented. Sludge samples are embedded in gelatin, spread over glass dishes, which are then placed over a flat-bed scanner where an image is captured. The images are processed with an image analysis software. The technique is simple, reliable and
Journal of Environmental Science and Health, Part A, 2013
The influence of initial pH and sulfate concentration on the anaerobic digestion of tannery waste... more The influence of initial pH and sulfate concentration on the anaerobic digestion of tannery wastewater was studied using the specific methanogenic activity (SMA) test. The SMA tests were performed with a chemical oxygen demand (COD) concentration of 6.5 g/L and SO(-2)4 concentrations of 1.95, 3.90, 6.50, 8.45 and 10.4 g/L. The effect of pH was studied at pH 6.8; 6.4 and 6.1. It was found that methane production took place under all conditions, but the use of SO(-2)4 concentrations higher than 8.45 g/L and initial pH levels lower than 6.4 caused a decrease of up to 73% of methane production. The influence of pH was significant only for SO(-2 4 concentrations lower than 8.45 g/L, with up to 50% inhibition. Specific methanogenic activity for COD/SO(-2)4 ratios lower than 0.77 depends basically on this ratio and not on the initial pH value under the conditions of the study.
Journal of the American Oil Chemists' Society, 2001
Rosa rubiginosa seed oil is valuable for cosmetics and phar-maceuticals as a reducer of dermal sc... more Rosa rubiginosa seed oil is valuable for cosmetics and phar-maceuticals as a reducer of dermal scars, color spots, and wrinkles from the skin surface. Although vast land areas in Chile are committed to this crop, the seeds are still underex-ploited or, in the best case, exported for ...
ABSTRACT Nitrogen removal via nitrite allows operational cost reduction in wastewater treatment o... more ABSTRACT Nitrogen removal via nitrite allows operational cost reduction in wastewater treatment of effluents with a low COD/N-NH4+ ratio, due to lower oxygen requirements for partial nitrification and a further diminishing in requirements of the external carbon source for the denitrification step. Two nitrifying systems - a suspended activated sludge (AS) reactor, and an airlift biofilm (AB) reactor-were compared to determine the best alternative for obtaining a maximum nitrite buildup. Both systems were operated under similar operational conditions; synthetic feed of ammonia nitrogen was applied to both reactors, at an ammonia loading rate (ALR) of 3.3 kg N-NH4+/m(3) and an hydraulic retention time of 4.3 h. Nitrite accumulation was studied by means of controlling dissolved oxygen (DO) concentration, keeping both pH and temperature constant. Similar results were obtained in both systems. In the activated sludge reactor maximum nitrite accumulation was achieved at 0.7 and at 3.5 mg DO/L in the airlift reactor. The obtained results showed that at a similar percentage of nitrite accumulation, the K(L)a value of the airlift reactor was always 3.6 times higher than the value obtained in the activated sludge reactor; however, the airflows required were similar in both reactors. The operation of nitrifying systems (biofilm and suspended biomass reactors) with low oxygen concentration to obtain nitrite accumulation make possible a decrease of required airflow, even at small nitrite accumulation. Airflow savings of 38 and 58% were obtained for the activated sludge reactor and the airlift reactor, respectively, at 15% of nitrite accumulation. When 40% of nitrite accumulation was detected in the activated sludge reactor and the airlift reactor, a savings of 80% and 65% were obtained, respectively.
A new technique for measuring the size distribution of anaerobic granular sludge, which involves ... more A new technique for measuring the size distribution of anaerobic granular sludge, which involves the use of digital image analysis, is presented. Sludge samples are embedded in gelatin, spread over glass dishes, which are then placed over a flat-bed scanner where an image is captured. The images are processed with an image analysis software. The technique is simple, reliable and
Journal of Environmental Science and Health, Part A, 2013
The influence of initial pH and sulfate concentration on the anaerobic digestion of tannery waste... more The influence of initial pH and sulfate concentration on the anaerobic digestion of tannery wastewater was studied using the specific methanogenic activity (SMA) test. The SMA tests were performed with a chemical oxygen demand (COD) concentration of 6.5 g/L and SO(-2)4 concentrations of 1.95, 3.90, 6.50, 8.45 and 10.4 g/L. The effect of pH was studied at pH 6.8; 6.4 and 6.1. It was found that methane production took place under all conditions, but the use of SO(-2)4 concentrations higher than 8.45 g/L and initial pH levels lower than 6.4 caused a decrease of up to 73% of methane production. The influence of pH was significant only for SO(-2 4 concentrations lower than 8.45 g/L, with up to 50% inhibition. Specific methanogenic activity for COD/SO(-2)4 ratios lower than 0.77 depends basically on this ratio and not on the initial pH value under the conditions of the study.
Journal of the American Oil Chemists' Society, 2001
Rosa rubiginosa seed oil is valuable for cosmetics and phar-maceuticals as a reducer of dermal sc... more Rosa rubiginosa seed oil is valuable for cosmetics and phar-maceuticals as a reducer of dermal scars, color spots, and wrinkles from the skin surface. Although vast land areas in Chile are committed to this crop, the seeds are still underex-ploited or, in the best case, exported for ...
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