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Papers by enrique sanchez

Process Biochemistry, 1996

Ammonia concentrations of 5 g N/litre or more inhibited thermophilic anaerobic digestion of cattl... more Ammonia concentrations of 5 g N/litre or more inhibited thermophilic anaerobic digestion of cattle manure in upflow anaerobic sludge blanket (UASB) reactors. A stable digestion of cattle manure could be maintained with ammonia concentrations up to 7 g N/litre after 6 months of ...

Biochemical Engineering Journal, 2002

... Kutz: Hindak 79/585 proved to be resistant with a satisfactory efficiency for cobalt biosorpt... more ... Kutz: Hindak 79/585 proved to be resistant with a satisfactory efficiency for cobalt biosorption from the ... 7. ACA Costa and SGF Leite , Metals bio-sorption by sodium alginate immobilized Chlorella homosphaera. ... GM Gadd and AJ Griffiths , Microorganisms and heavy metal toxicity ...

Journal of Biotechnology, 1996

A high rate anaerobic treatment of palm oil mill effluent (POME) was achieved in a two-stage up-f... more A high rate anaerobic treatment of palm oil mill effluent (POME) was achieved in a two-stage up-flow anaerobic sludge blanket (UASB) reactor. The acidogenic reactor acclimated rapidly to the wastewater and was tolerant to a suspended solids (SS) concentration of 5.4 g 1-r in the influent wastewater. Loading was gradually increased over a period of 100 days resulting in a satisfactory hydrolysis and acidification giving a maximum rate of acid production of 4.1 g I-' d _ ' acetic acid at a loading rate of 16.6 g I-' d-' COD at a hydraulic retention time of 0.9 days. An increase in alkalinity throughout the acclimatization maintained the effluent from the reactor at around pH 5.8. The methanogenic reactor was initially fed on dilutions of the effluent from the first stage reactor after pH adjustment. The loading was gradually increased, and then stepwise, to 60 g I-' dd' COD at which point COD removal efficiency had declined significantly and an accumulation of long-chain volatile fatty acids was observed. It was concluded that the reactor could work efficiently up to loadings of 30 g l-' dd' COD, whilst producing a good methane yield and a COD reduction of greater than 90%. Effluent recirculation alleviated the need for alkali additions to the feed of the methanogenic reactor and a direct coupling of the two reactors was achieved towards the end of the experimental run of 175 days. Both reactors showed granule formation with distinct morphological characteristics; these were observed to be formed after 80 days in the acidogenic reactor and after I IO days in the methanogenic reactor.

Process Biochemistry, 2001

A study of the effect of substrate concentration and temperature variation on batch anaerobic dig... more A study of the effect of substrate concentration and temperature variation on batch anaerobic digestion of piggery waste was carried out in laboratory-scale completely mixed reactors. The variation of chemical oxygen demand (COD), total volatile fatty acids (TVFA), alkalinity, pH and methane production with digestion time followed the same pattern at mesophilic (35°C) and ambient temperatures (16.8–29.5°C). The process was

Bioresource Technology, 2005

A study of anaerobic digestion of piggery wastewater was carried out in a laboratory-scale sludge... more A study of anaerobic digestion of piggery wastewater was carried out in a laboratory-scale sludge bed reactor as a secondary treatment. The effect of organic volumetric loading rates (B V ) in the range of 1.0-8.1 g TCOD/l d on the process performance was evaluated. The best results were obtained at B V equal to or lower than 4 g TCOD/l d. At higher B V values, the removal efficiency of the process decreased suddenly. A linear relationship was found between the effluent SCOD and the TVFA/alkalinity ratio (P ). A relationship was found among the different operational variables (B V , removal efficiency, effluent soluble COD, soluble COD removal rate (R), retention factor (/), specific microbial growth rate (l), methane production rate per volume of reactor and per volume of waste treated--Q M and q M , respectively) and the corresponding regression equations were obtained. An increase of B V determined a decrease of removal efficiency, / and q M and an increase of effluent soluble COD, l, R and Q M . The value of the maximum specific microbial growth rate (l M ) determined through the equation that correlated B V and l was found to be 0.19 d À1 . This value was of the same magnitude as those reported in other works of anaerobic digestion of piggery waste.

Bioresource Technology, 2001

The effect of different natural zeolite concentrations on the anaerobic digestion of piggery wast... more The effect of different natural zeolite concentrations on the anaerobic digestion of piggery waste was studied. Natural zeolite doses in the range 0.2-10 g/l of wastewater were used in batch experiments, which were carried out at temperatures between 27 degrees C and 30 degrees C. Total chemical oxygen demand (COD), total and volatile solids, ammonia and organic nitrogen, pH, total volatile fatty acids (TVFA), alkalinity (Alk) and accumulative methane production were determined during 30 days of digestion. The anaerobic digestion process was favored by the addition of natural zeolite at doses between 2 and 4 g/l and increasingly inhibited at doses beyond 6 g/l. A first-order kinetic model of COD removal was used to determine the apparent kinetic constants of the process. The kinetic constant values increased with the zeolite amount up to a concentration of 4 g/l. The values of the maximum accumulative methane production (Gm) increased until zeolite concentrations of 2-4 g/l. The addition of zeolite reduced the values of the TVFA/ Alk ratio while increasing the pH values, and these facts could contribute to the process failure at zeolite doses of 10 g/l.

Ecological Indicators, 2007

The use of the water quality index (WQI) and the dissolved oxygen deficit (D) as simple indicator... more The use of the water quality index (WQI) and the dissolved oxygen deficit (D) as simple indicators of the watersheds pollution was investigated and compared in the Municipality of Las Rozas (north-west of Madrid, Spain). The quality of the water in Guadarrama and Manzanares rivers and Paris Park ponds, the main watersheds of this area was investigated during 2 years (from September 2001 to September 2003). It was found that the WQI was very useful for the classification of the waters monitored. The WQI was 70, which corresponds to ''good'' quality water at the sampling point 1 (entrance of Las Rozas) and decreased to around 64 (medium quality) at the sampling point 6 (outlet of Las Rozas) in the case of Guadarrama River. The WQI was around 65 in the influents of Manzanares River. Finally, in Paris Park the WQI ranged from around 72-55, which corresponded to a classification from ''good'' to ''medium'' quality, respectively. A high linear relationship between the WQI and the dissolved oxygen deficit (D) was found. Therefore, a fast determination of WQI may be carried out knowing the values of D, which are easily obtainable by field measurements. It was found an influence of the climate conditions on the values of WQI and D. #

Process Biochemistry, 1996

Ammonia concentrations of 5 g N/litre or more inhibited thermophilic anaerobic digestion of cattl... more Ammonia concentrations of 5 g N/litre or more inhibited thermophilic anaerobic digestion of cattle manure in upflow anaerobic sludge blanket (UASB) reactors. A stable digestion of cattle manure could be maintained with ammonia concentrations up to 7 g N/litre after 6 months of ...

Biochemical Engineering Journal, 2002

... Kutz: Hindak 79/585 proved to be resistant with a satisfactory efficiency for cobalt biosorpt... more ... Kutz: Hindak 79/585 proved to be resistant with a satisfactory efficiency for cobalt biosorption from the ... 7. ACA Costa and SGF Leite , Metals bio-sorption by sodium alginate immobilized Chlorella homosphaera. ... GM Gadd and AJ Griffiths , Microorganisms and heavy metal toxicity ...

Journal of Biotechnology, 1996

A high rate anaerobic treatment of palm oil mill effluent (POME) was achieved in a two-stage up-f... more A high rate anaerobic treatment of palm oil mill effluent (POME) was achieved in a two-stage up-flow anaerobic sludge blanket (UASB) reactor. The acidogenic reactor acclimated rapidly to the wastewater and was tolerant to a suspended solids (SS) concentration of 5.4 g 1-r in the influent wastewater. Loading was gradually increased over a period of 100 days resulting in a satisfactory hydrolysis and acidification giving a maximum rate of acid production of 4.1 g I-' d _ ' acetic acid at a loading rate of 16.6 g I-' d-' COD at a hydraulic retention time of 0.9 days. An increase in alkalinity throughout the acclimatization maintained the effluent from the reactor at around pH 5.8. The methanogenic reactor was initially fed on dilutions of the effluent from the first stage reactor after pH adjustment. The loading was gradually increased, and then stepwise, to 60 g I-' dd' COD at which point COD removal efficiency had declined significantly and an accumulation of long-chain volatile fatty acids was observed. It was concluded that the reactor could work efficiently up to loadings of 30 g l-' dd' COD, whilst producing a good methane yield and a COD reduction of greater than 90%. Effluent recirculation alleviated the need for alkali additions to the feed of the methanogenic reactor and a direct coupling of the two reactors was achieved towards the end of the experimental run of 175 days. Both reactors showed granule formation with distinct morphological characteristics; these were observed to be formed after 80 days in the acidogenic reactor and after I IO days in the methanogenic reactor.

Process Biochemistry, 2001

A study of the effect of substrate concentration and temperature variation on batch anaerobic dig... more A study of the effect of substrate concentration and temperature variation on batch anaerobic digestion of piggery waste was carried out in laboratory-scale completely mixed reactors. The variation of chemical oxygen demand (COD), total volatile fatty acids (TVFA), alkalinity, pH and methane production with digestion time followed the same pattern at mesophilic (35°C) and ambient temperatures (16.8–29.5°C). The process was

Bioresource Technology, 2005

A study of anaerobic digestion of piggery wastewater was carried out in a laboratory-scale sludge... more A study of anaerobic digestion of piggery wastewater was carried out in a laboratory-scale sludge bed reactor as a secondary treatment. The effect of organic volumetric loading rates (B V ) in the range of 1.0-8.1 g TCOD/l d on the process performance was evaluated. The best results were obtained at B V equal to or lower than 4 g TCOD/l d. At higher B V values, the removal efficiency of the process decreased suddenly. A linear relationship was found between the effluent SCOD and the TVFA/alkalinity ratio (P ). A relationship was found among the different operational variables (B V , removal efficiency, effluent soluble COD, soluble COD removal rate (R), retention factor (/), specific microbial growth rate (l), methane production rate per volume of reactor and per volume of waste treated--Q M and q M , respectively) and the corresponding regression equations were obtained. An increase of B V determined a decrease of removal efficiency, / and q M and an increase of effluent soluble COD, l, R and Q M . The value of the maximum specific microbial growth rate (l M ) determined through the equation that correlated B V and l was found to be 0.19 d À1 . This value was of the same magnitude as those reported in other works of anaerobic digestion of piggery waste.

Bioresource Technology, 2001

The effect of different natural zeolite concentrations on the anaerobic digestion of piggery wast... more The effect of different natural zeolite concentrations on the anaerobic digestion of piggery waste was studied. Natural zeolite doses in the range 0.2-10 g/l of wastewater were used in batch experiments, which were carried out at temperatures between 27 degrees C and 30 degrees C. Total chemical oxygen demand (COD), total and volatile solids, ammonia and organic nitrogen, pH, total volatile fatty acids (TVFA), alkalinity (Alk) and accumulative methane production were determined during 30 days of digestion. The anaerobic digestion process was favored by the addition of natural zeolite at doses between 2 and 4 g/l and increasingly inhibited at doses beyond 6 g/l. A first-order kinetic model of COD removal was used to determine the apparent kinetic constants of the process. The kinetic constant values increased with the zeolite amount up to a concentration of 4 g/l. The values of the maximum accumulative methane production (Gm) increased until zeolite concentrations of 2-4 g/l. The addition of zeolite reduced the values of the TVFA/ Alk ratio while increasing the pH values, and these facts could contribute to the process failure at zeolite doses of 10 g/l.

Ecological Indicators, 2007

The use of the water quality index (WQI) and the dissolved oxygen deficit (D) as simple indicator... more The use of the water quality index (WQI) and the dissolved oxygen deficit (D) as simple indicators of the watersheds pollution was investigated and compared in the Municipality of Las Rozas (north-west of Madrid, Spain). The quality of the water in Guadarrama and Manzanares rivers and Paris Park ponds, the main watersheds of this area was investigated during 2 years (from September 2001 to September 2003). It was found that the WQI was very useful for the classification of the waters monitored. The WQI was 70, which corresponds to ''good'' quality water at the sampling point 1 (entrance of Las Rozas) and decreased to around 64 (medium quality) at the sampling point 6 (outlet of Las Rozas) in the case of Guadarrama River. The WQI was around 65 in the influents of Manzanares River. Finally, in Paris Park the WQI ranged from around 72-55, which corresponded to a classification from ''good'' to ''medium'' quality, respectively. A high linear relationship between the WQI and the dissolved oxygen deficit (D) was found. Therefore, a fast determination of WQI may be carried out knowing the values of D, which are easily obtainable by field measurements. It was found an influence of the climate conditions on the values of WQI and D. #