Ruben Mendez - Academia.edu (original) (raw)
Papers by Ruben Mendez
Brazilian Archives of Biology and Technology, 1999
... Gladys Vidal I* ; Manuel Soto II , Ramón Méndez III ; Juan Manuel Lema III. ... The biologica... more ... Gladys Vidal I* ; Manuel Soto II , Ramón Méndez III ; Juan Manuel Lema III. ... The biological removal of AOX in aerated systems seems to be more difficult for hardwood pulp bleaching effluents (Bryant and Amy, 1991), no removals being reported for Eucalyptus pulp bleaching ...
An ammonia loading rate of 4.1 kg N-NH 4 + /m 3 d was fully oxidized to nitrate using a nitrifyin... more An ammonia loading rate of 4.1 kg N-NH 4 + /m 3 d was fully oxidized to nitrate using a nitrifying airlift without biomass carrier. The developed sludge, with a concentration of 12 gVSS/L and high density (100 gVSS/L particle ), allowed particles to be retained with small diameter, having very low concentrations of solids in the effluent (5-10 mg VSS/L). The mean diameter of particles containing the majority of total biomass increased from 220 to 360 m during the operation time. The particle size analysis showed that the percentage of flocs with small diameter (1-3 m) is very high but the biomass content of these flocs is negligible with respect to the total biomass value. The oxygen transfer coefficient (K La ) was measured operating at different air flow rates, obtaining similar values during the overall operational period. The use of activated sludge without support gives high nitrifying rates with an easier fluidization and a lower critical air flow rate than in a biofilm airlift reactor.
Page 1. ISSN 0378-4738 = Water SA Vol. 24 No. 3 July 1998 245 Notation COD Chemical oxygen demand... more Page 1. ISSN 0378-4738 = Water SA Vol. 24 No. 3 July 1998 245 Notation COD Chemical oxygen demand (mg/l) HRT Hydraulic residence time NLR Nitrogen loading rate (g-TKN/l·d) OLR Organic loading rate (g-COD/l·d) SS ...
Three Circulating Floating Bed Reactors (CFBR) R1, R2 and R3 with 20% v/v of a plastic carrier wi... more Three Circulating Floating Bed Reactors (CFBR) R1, R2 and R3 with 20% v/v of a plastic carrier with different size distribution were operated to study the effect of the particles size of the carrier on biomass accumulation and nitrification performance. Operating conditions were similar in the three systems: ammonia concentrations around 50 mg-N-NH 4 + / L, ammonia loading rates up to 1.2 kg N-NH 4 + /m 3 · d and temperatures between 14 and 27ºC. Accumulation of nitrite was observed until day 65th. This was result both of the inhibition of nitrite oxidation by free ammonia until day 20th and the insignificant accumulation of a biomass with low nitrite oxidising capacity between days 20 and 65th. Ammonia conversion rate and removal efficiency were higher in the reactor with lower particle size, R3 (nitrification rate of 1.1 kg N-NH 4 + /m 3 · d and ammonia removal of 97% at 16ºC), than in R2 or R1 (nitrification rate of 1.0 kg N-NH 4 + /m 3 · d and ammonia removal of 90% at 16ºC). The better efficiency in R3 was obtained as a result of the higher specific surface of the biofilm developed. Biomass activity was similar in the three reactors (2.2 and 1.12 g N/g protein · d at 30 and 15ºC, respectively). Both the biomass evolution with time and biomass retention in the systems was practically not influenced by the size of particle. Biomass concentration of 1.2 g protein/L was retained in the carrier and up to 20% of the newly produced biomass was retained in the CFBRs.
Water Science & Technology
As a prelude to the individual papers describing the various anaerobic treatment process configur... more As a prelude to the individual papers describing the various anaerobic treatment process configurations, the anaerobic treatment process is described in terms of chemical reaction engineering. These descriptions are made in terms of kinetics, stoichiometry, ...
1.-Technologies based on aerobic granular biomass Biological wastewater treatment is often accomp... more 1.-Technologies based on aerobic granular biomass Biological wastewater treatment is often accomplished by means of conventional activated sludge systems. In general, activated sludge has relatively poor settling characteristics with values of sludge volumetric index (SVI) around 100-200 mL/g VSS and settling velocities lower than 1 m/h. The interest in applying aerobic granular systems is mainly related to the compactness of its design in comparison to conventional activated sludge wastewater treatment systems. Experiments performed at laboratory scale indicated that, in aerobic granular reactors, organic matter removal efficiencies ranged between 80 and 98%, while nitrogen removal efficiencies were slightly lower (70 -95%). The physical properties of the aerobic granular biomass showed values of SVI lower than 60 mL/g VSS, densities larger than 10 g VSS/L and mean feret diameter (D feret) that ranged between 1.0 and 3.5 mm. These results obtained at laboratory scale showed the pot...
Environmental Technology Letters, 1989
Semi‐micro determinations of the COD of wastewaters can err considerably if chloride is present. ... more Semi‐micro determinations of the COD of wastewaters can err considerably if chloride is present. This article reports the degree to which accuracy is influenced by 1) COD itself; 2) the concentration of the masking agent HgSO4 in the digesting solution; 3) the presence of other salts, which is especially relevant in the case of water of marine origin; and 4)
Abstract}A lab-scale hybrid upflow sludge bed-filter (USBF) reactor was employed to carry out met... more Abstract}A lab-scale hybrid upflow sludge bed-filter (USBF) reactor was employed to carry out methanogenesis and denitrification of the effluent from an anaerobic industrial reactor (EAIR) in a fish canning industry. The reactor was initially inoculated with methanogenic sludge and there were two different operational steps. During the first step (Step I: days 1-61), the methanogenic process was carried out at organic loading rates (OLR) of 1.0-1.25 g COD l À 1 d À 1 reaching COD removal percentages of 80%. During the second step (Step II: days 62-109) nitrate was added as KNO 3 to the industrial effluent and the OLR was varied between 1.0 and 1.25 g COD l À 1 d À 1 . Two different nitrogen loads of 0.10 and 0.22 g NO À 3 2N l À 1 d À 1 were applied and these led to nitrogen removal percentages of around 100% in both cases and COD removal percentages of around 80%. Carbon to nitrogen ratio (C : N) in the influent was maintained at 2.0 and eventually it was increased to 3.0, by means of glucose addition, to control the denitrification process. From these results it is possible to establish that wastewater produced in a fish canning industry can be used as a carbon source for denitrification and that denitrifying microorganisms were present in the initially methanogenic sludge. Biomass productions of 0.23 and 0.61 g VSS : g TOC fed for Steps I and II, respectively, were calculated from carbon global balances, showing an increase in biomass growth due to denitrification. #
Water Research, 1990
ABSTRACT
Water Science and Technology, 1997
Fisheries Processing, 1994
ABSTRACT
Water Science & Technology, 2011
An airlift reactor using zeolite particles as carrier material was used for the nitrification of ... more An airlift reactor using zeolite particles as carrier material was used for the nitrification of effluents from the aquaculture industry. During the start-up the nitrogen concentration was kept around 100 mg NH 4 þ -N/L to develop the nitrifying population. Later it was decreased down to around 3 mg NH 4 þ -N/L and the dilution rate was increased up to 4.8 d À1 in order to simulate the conditions in a an aquaculture waster treatment system. A nitrogen loading rate (NLR) of 535 mg NH 4 þ -N/m 2 d was fully oxidized to nitrate. Higher values of NLRs caused nitrite accumulation. A second biofilm reactor was fed with a synthetic medium containing 50 mg NH 4 þ -N/L which simulated the effluents from anaerobic units treating domestic wastewater.
Water Research, 1997
Two methanogenic cultures were grown in the presence of p-cresol as sole carbon source or togethe... more Two methanogenic cultures were grown in the presence of p-cresol as sole carbon source or together with a mixture of volatile fatty acids (VFA). Both batch cultures produced methane from VFA in the pre,;ence of p-cresol, up to concentrations of about 200 ppm, in a first experiment, without significant activity inhibition. After several transfers, one of the cultures tolerated higher p-cresol concentrations. Only that culture, originating from industrial effluents contaminated with phenolic compounds, was able to remove p-cresol which was completely degraded to methane and carbon dioxide with p-hydroxybenzoate, propionate and acetate as detectable intermediate compounds. These intermediates did not accumulate in the medium. The addition of VFA as auxilliary carbon sources very slightly delayed p-cresol removal in batch assays but allowed, on the contrary, the use of higher p-cresol influent co:acentrations in continuous UASB reactors than in the absence of VFA. With a mixture of p-cresol:VFA at a COD ratio of 2:1, complete COD degradation was reached when operating at an hydraulic retention time (HRT) of 0.67 day and at an influent concentration of 650 ppm p-cresol. When operating Ltnder the same conditions in the absence of VFA, around 80% p-cresol was removed although a near complete degradation was reached at influent p-cresol concentrations of 400 ppm working at a H RT of 0.8 day. © 1997 Elsevier Science Ltd NOMENCLATURE HRT = hydraulic retention time OLR = organic loading rate VFA = volatile fi~tty acids COD = chemical oxygen demand TOC = total organic carbon
Water Research, 2003
Wastewater containing formaldehyde and urea was treated using a coupled system consisting of a bi... more Wastewater containing formaldehyde and urea was treated using a coupled system consisting of a biofilm airlift suspension (BAS) reactor and an anoxic upflow sludge blanket (USB) reactor. The anoxic USB reactor was used to carry out denitrification and urea hydrolysis, while the BAS reactor was used to carry out nitrification.
We describe a Bayesian Reasoning Framework (BRF) that supports business rule operations for on-li... more We describe a Bayesian Reasoning Framework (BRF) that supports business rule operations for on-line information systems. BRF comprises a three-layer environment with business information systems at the top, a middle-ware Bayesian reasoning server, and a ...
Brazilian Archives of Biology and Technology, 1999
... Gladys Vidal I* ; Manuel Soto II , Ramón Méndez III ; Juan Manuel Lema III. ... The biologica... more ... Gladys Vidal I* ; Manuel Soto II , Ramón Méndez III ; Juan Manuel Lema III. ... The biological removal of AOX in aerated systems seems to be more difficult for hardwood pulp bleaching effluents (Bryant and Amy, 1991), no removals being reported for Eucalyptus pulp bleaching ...
An ammonia loading rate of 4.1 kg N-NH 4 + /m 3 d was fully oxidized to nitrate using a nitrifyin... more An ammonia loading rate of 4.1 kg N-NH 4 + /m 3 d was fully oxidized to nitrate using a nitrifying airlift without biomass carrier. The developed sludge, with a concentration of 12 gVSS/L and high density (100 gVSS/L particle ), allowed particles to be retained with small diameter, having very low concentrations of solids in the effluent (5-10 mg VSS/L). The mean diameter of particles containing the majority of total biomass increased from 220 to 360 m during the operation time. The particle size analysis showed that the percentage of flocs with small diameter (1-3 m) is very high but the biomass content of these flocs is negligible with respect to the total biomass value. The oxygen transfer coefficient (K La ) was measured operating at different air flow rates, obtaining similar values during the overall operational period. The use of activated sludge without support gives high nitrifying rates with an easier fluidization and a lower critical air flow rate than in a biofilm airlift reactor.
Page 1. ISSN 0378-4738 = Water SA Vol. 24 No. 3 July 1998 245 Notation COD Chemical oxygen demand... more Page 1. ISSN 0378-4738 = Water SA Vol. 24 No. 3 July 1998 245 Notation COD Chemical oxygen demand (mg/l) HRT Hydraulic residence time NLR Nitrogen loading rate (g-TKN/l·d) OLR Organic loading rate (g-COD/l·d) SS ...
Three Circulating Floating Bed Reactors (CFBR) R1, R2 and R3 with 20% v/v of a plastic carrier wi... more Three Circulating Floating Bed Reactors (CFBR) R1, R2 and R3 with 20% v/v of a plastic carrier with different size distribution were operated to study the effect of the particles size of the carrier on biomass accumulation and nitrification performance. Operating conditions were similar in the three systems: ammonia concentrations around 50 mg-N-NH 4 + / L, ammonia loading rates up to 1.2 kg N-NH 4 + /m 3 · d and temperatures between 14 and 27ºC. Accumulation of nitrite was observed until day 65th. This was result both of the inhibition of nitrite oxidation by free ammonia until day 20th and the insignificant accumulation of a biomass with low nitrite oxidising capacity between days 20 and 65th. Ammonia conversion rate and removal efficiency were higher in the reactor with lower particle size, R3 (nitrification rate of 1.1 kg N-NH 4 + /m 3 · d and ammonia removal of 97% at 16ºC), than in R2 or R1 (nitrification rate of 1.0 kg N-NH 4 + /m 3 · d and ammonia removal of 90% at 16ºC). The better efficiency in R3 was obtained as a result of the higher specific surface of the biofilm developed. Biomass activity was similar in the three reactors (2.2 and 1.12 g N/g protein · d at 30 and 15ºC, respectively). Both the biomass evolution with time and biomass retention in the systems was practically not influenced by the size of particle. Biomass concentration of 1.2 g protein/L was retained in the carrier and up to 20% of the newly produced biomass was retained in the CFBRs.
Water Science & Technology
As a prelude to the individual papers describing the various anaerobic treatment process configur... more As a prelude to the individual papers describing the various anaerobic treatment process configurations, the anaerobic treatment process is described in terms of chemical reaction engineering. These descriptions are made in terms of kinetics, stoichiometry, ...
1.-Technologies based on aerobic granular biomass Biological wastewater treatment is often accomp... more 1.-Technologies based on aerobic granular biomass Biological wastewater treatment is often accomplished by means of conventional activated sludge systems. In general, activated sludge has relatively poor settling characteristics with values of sludge volumetric index (SVI) around 100-200 mL/g VSS and settling velocities lower than 1 m/h. The interest in applying aerobic granular systems is mainly related to the compactness of its design in comparison to conventional activated sludge wastewater treatment systems. Experiments performed at laboratory scale indicated that, in aerobic granular reactors, organic matter removal efficiencies ranged between 80 and 98%, while nitrogen removal efficiencies were slightly lower (70 -95%). The physical properties of the aerobic granular biomass showed values of SVI lower than 60 mL/g VSS, densities larger than 10 g VSS/L and mean feret diameter (D feret) that ranged between 1.0 and 3.5 mm. These results obtained at laboratory scale showed the pot...
Environmental Technology Letters, 1989
Semi‐micro determinations of the COD of wastewaters can err considerably if chloride is present. ... more Semi‐micro determinations of the COD of wastewaters can err considerably if chloride is present. This article reports the degree to which accuracy is influenced by 1) COD itself; 2) the concentration of the masking agent HgSO4 in the digesting solution; 3) the presence of other salts, which is especially relevant in the case of water of marine origin; and 4)
Abstract}A lab-scale hybrid upflow sludge bed-filter (USBF) reactor was employed to carry out met... more Abstract}A lab-scale hybrid upflow sludge bed-filter (USBF) reactor was employed to carry out methanogenesis and denitrification of the effluent from an anaerobic industrial reactor (EAIR) in a fish canning industry. The reactor was initially inoculated with methanogenic sludge and there were two different operational steps. During the first step (Step I: days 1-61), the methanogenic process was carried out at organic loading rates (OLR) of 1.0-1.25 g COD l À 1 d À 1 reaching COD removal percentages of 80%. During the second step (Step II: days 62-109) nitrate was added as KNO 3 to the industrial effluent and the OLR was varied between 1.0 and 1.25 g COD l À 1 d À 1 . Two different nitrogen loads of 0.10 and 0.22 g NO À 3 2N l À 1 d À 1 were applied and these led to nitrogen removal percentages of around 100% in both cases and COD removal percentages of around 80%. Carbon to nitrogen ratio (C : N) in the influent was maintained at 2.0 and eventually it was increased to 3.0, by means of glucose addition, to control the denitrification process. From these results it is possible to establish that wastewater produced in a fish canning industry can be used as a carbon source for denitrification and that denitrifying microorganisms were present in the initially methanogenic sludge. Biomass productions of 0.23 and 0.61 g VSS : g TOC fed for Steps I and II, respectively, were calculated from carbon global balances, showing an increase in biomass growth due to denitrification. #
Water Research, 1990
ABSTRACT
Water Science and Technology, 1997
Fisheries Processing, 1994
ABSTRACT
Water Science & Technology, 2011
An airlift reactor using zeolite particles as carrier material was used for the nitrification of ... more An airlift reactor using zeolite particles as carrier material was used for the nitrification of effluents from the aquaculture industry. During the start-up the nitrogen concentration was kept around 100 mg NH 4 þ -N/L to develop the nitrifying population. Later it was decreased down to around 3 mg NH 4 þ -N/L and the dilution rate was increased up to 4.8 d À1 in order to simulate the conditions in a an aquaculture waster treatment system. A nitrogen loading rate (NLR) of 535 mg NH 4 þ -N/m 2 d was fully oxidized to nitrate. Higher values of NLRs caused nitrite accumulation. A second biofilm reactor was fed with a synthetic medium containing 50 mg NH 4 þ -N/L which simulated the effluents from anaerobic units treating domestic wastewater.
Water Research, 1997
Two methanogenic cultures were grown in the presence of p-cresol as sole carbon source or togethe... more Two methanogenic cultures were grown in the presence of p-cresol as sole carbon source or together with a mixture of volatile fatty acids (VFA). Both batch cultures produced methane from VFA in the pre,;ence of p-cresol, up to concentrations of about 200 ppm, in a first experiment, without significant activity inhibition. After several transfers, one of the cultures tolerated higher p-cresol concentrations. Only that culture, originating from industrial effluents contaminated with phenolic compounds, was able to remove p-cresol which was completely degraded to methane and carbon dioxide with p-hydroxybenzoate, propionate and acetate as detectable intermediate compounds. These intermediates did not accumulate in the medium. The addition of VFA as auxilliary carbon sources very slightly delayed p-cresol removal in batch assays but allowed, on the contrary, the use of higher p-cresol influent co:acentrations in continuous UASB reactors than in the absence of VFA. With a mixture of p-cresol:VFA at a COD ratio of 2:1, complete COD degradation was reached when operating at an hydraulic retention time (HRT) of 0.67 day and at an influent concentration of 650 ppm p-cresol. When operating Ltnder the same conditions in the absence of VFA, around 80% p-cresol was removed although a near complete degradation was reached at influent p-cresol concentrations of 400 ppm working at a H RT of 0.8 day. © 1997 Elsevier Science Ltd NOMENCLATURE HRT = hydraulic retention time OLR = organic loading rate VFA = volatile fi~tty acids COD = chemical oxygen demand TOC = total organic carbon
Water Research, 2003
Wastewater containing formaldehyde and urea was treated using a coupled system consisting of a bi... more Wastewater containing formaldehyde and urea was treated using a coupled system consisting of a biofilm airlift suspension (BAS) reactor and an anoxic upflow sludge blanket (USB) reactor. The anoxic USB reactor was used to carry out denitrification and urea hydrolysis, while the BAS reactor was used to carry out nitrification.
We describe a Bayesian Reasoning Framework (BRF) that supports business rule operations for on-li... more We describe a Bayesian Reasoning Framework (BRF) that supports business rule operations for on-line information systems. BRF comprises a three-layer environment with business information systems at the top, a middle-ware Bayesian reasoning server, and a ...