16 research outputs found
Biodegradability and toxicity of styrene in the anaerobic digestion process
Start-up and operation of an Upflow Anaerobic Sludge Blanket (UASB) reactor fed with an industrial effluent from
a polymer synthesis plant containing 6 mg styrene 1ˉ¹ was unstable. In batch assays with 200 mg styrene 1ˉ¹, 74%
of styrene was degraded at a rate of 7 ml methane gˉ¹ volatile suspended solids.day, without a lag phase. The
toxicity limit (IC50) of styrene was 1.4 mM for the acetoclastic activity, 0.45 and 1.6 mM for the methanogenic
activity in the presence of 30 mM of propionate and ethanol respectively. Instability of UASB operation was
attributed to other compounds such as acrylates or detergents present in the industrial effluent.Project ALFA - ALR/B-73011/94.04-4.0181.9
Análisis de imagen para la cuantificación de cambios morfológicos en biomasa granular, inducidos por la presencia de nitrato en reactores EGSB
Cuatro reactores EGSB (R1-R4) fueron operados a velocidades
de carga orgánica de 10 kgCOD/(m³.d), tiempos de retención hidráulicos
de 3.6 h, velocidades superficiales de 10 m/h y diferentes
concentraciones de nitrato a la entrada, 0, 20, 60 y 100 mgN-NO3-/L en
R1, R2, R3 and R4, respectivamente. Después de 20 dÃas de operación
continua, la biomasa granular fue caracterizada en términos de: (i)
morfologÃa por análisis de imagen cuantitativo; (ii) actividad
metanogénica especÃfica en presencia de acetato, butirato, propionato,
etanol y una mezcla gaseosa de H2CO2; velocidad de sedimentación. El
parámetro LfA, definido como el cuociente entre la longitud total de
filamentos y el área total proyectada, fue determinado y se observó que
es suficientemente sensible para la cuantificación de diferencias
morfológicas inducidas por la presencia de nitrato. Aunque el
crecimiento de estructuras filamentosas en la superficie de los gránulos
fue evidente, no hubo una disminución notable en la velocidad de
sedimentación de los gránulos, probablemente porque durante el
perÃodo de operación los gránulos crecieron en tamaño. En el reactor
R4 se observó un mayor washout que en R1, R2 y R3.Fundação para a Ciência e Tecnologia (FCT
Recovery of acetoclastic activity in anaerobic granular sludge, monitored by methanogenic activity measurements and image analysis
The specific acetoclastic activity (SAA) of anaerobic granular sludge was
recovered in a lab scale EGSB reactor. The inoculum presented a very low
acetoclastic activity (0.81+/-2.48mg COD-CH4/gVSS.day). Ethanol was fed
at a COD concentration of 1.5g/L, as sole organic carbon source to promote
the biogas production through the hydrogenophilic pathway. During the
operation period the specific methanogenic activity (SMA)1 in the presence
of acetate, propionate, butyrate, ethanol and H2/CO2, and the biomass
morphology were quantified. The SAA steadily increased as expected by the
reactor performance, achieving a value of 183+/-13mg COD-CH4/gVSS.day
at day 108. From the SMA results it was suggested that, until day 62, the
initial methane production rate was dominated by the hydrogenotrophic
population and afterwards, the developed acetoclastic activity started to play
a role in the initial methane production from ethanol. Until day 62 the ratio
between the filaments length and aggregates projected area (LfA)2 increased
due to the breakdown of granules inside the reactor, after that decreased and
granules development was simultaneous with the increase of the SAA.
Percentage of aggregates in size range 0.1 to 1mm (equivalent diameter)
increased until day 40 due to granules fragmentation. When the system
achieved a steady state, the aggregates size increased
Image analysis to quantify morphological changes in granular sludge induced by nitrate in EGSB reactors
Four EGSB reactors (R1 to R4) were operated at an organic loading rate of 10 kgCOD/(m³.d),
hydraulic retention time of 3.6 h, upflow velocity of 10 m/h and different influent nitrate concentrations (0, 20,
60 and 100 mgN-NO_3-/L for R1, R2, R3 and R4, respectively. After about 20 days of operation, the granular
sludge was characterized for: (i) morphology by quantitative image analysis; (ii) specific methanogenic
activity in the presence of acetate, propionate, butyrate, ethanol and H_2/CO_2; (iii) settling velocity. LfA
parameter, defined as the ratio of total filaments length to total projected area, was determined and was
sensitive to quantify the different surface morphology, induced by nitrate to the granular sludge. Although
the growth of filamentous structures was evident, no significant decrease on the settling velocity was
observed, most likely because granules grew during the trial period. A higher washout occurred in R4, as
compared to R1, R2 and R3.Grant SFRH/BD/3187/2000.Fundação para a Ciência e a Tecnologia (FCT) – PRAXIS XXI/BD/20325/99
Quantitative image analysis as a diagnostic tool for identifying structural changes during a revival process of anaerobic granular sludge
Due to unspecified operational problems, the specific acetoclastic activity (SAA) of the
anaerobic granular sludge present in an industrial UASB reactor was considerably damaged (from 250 to less than 10mL CH4@STP/gVSS.d), significantly reducing the biogas production of that industrial unit. The hydrogenotrophic methanogenic activity exhibited a value of 600mL CH4@STP/gVSS.d, the settling velocity was 31.479.8 m/h, the average equivalent
diameter was 0.9270.43mm, and about 70% of the VSS were structured in aggregates larger than 1mm.
In order to study the recovery of the SAA, this sludge was collected and inoculated in a
lab-scale expanded granular sludge blanket (EGSB) reactor. Ethanol was fed as the sole
carbon source during a trial period of 106 days. Process monitoring included COD removal efficiency, methane production, and periodic determination of the specific methanogenic activity in the presence of acetate, propionate, butyrate, ethanol and H2/CO2.
Quantitative image analysis allowed for information to be obtained on granular fragmentation/erosion and filaments release. During the first operational period, biogas production was mainly due to the hydrogenotrophic activity. However, after 40 days, the SAA steadily increased
achieving a maximum value of 183713mL CH4@STP/gVSS.d. The onset of SAA recovery, granules breakdown and filaments release to the bulk occurred simultaneously. Further increase in SAA was accompanied by granular growth. In the last 25 days of operation, the size distribution was stable with more than 80% of projected area of aggregates corresponding to granules larger than 1mm (equivalent diameter). Confocal images from FISH hybridized sections of the granules showed that after SAA recovery, the granules developed an organized structure where an acidogenic/acetogenic external layer was apparent. Granular fragmentation and increase of filaments in the bulk, simultaneously with the increase in the acetoclastic activity are described for the first time and might represent a structural response of granular sludge to promote the optimal substrate uptake at minimal diffusion limitations.Fundação para a Ciência e a Tecnologia (FCT) - Grants SFRH/BD/3187/2000, SFRH/BD/13317/2003, Project POCTI/BIO/37934/2001
Grants SFRH/BD/3187/2000, SFRH/BD/13317/200
Image analysis as a tool to recognize anaerobic granulation time
Image analysis techniques were used to monitor the development of anaerobic granules into an EGSB reactor fed with a synthetic substrate based on glucose (30-40% COD) and volatile fatty acids (70-60% COD) during 400 days. Two types of objects were recognized and quantified: aggregates and free filaments. The aggregates were classified into five ranges based on the equivalent diameter: smaller than 11.3 mm (residual), between 11.3 and 35.7 mm, between 35.7 and 112.8 mm, between 112.8 and 356.8 mm and larger than 356.8 mm. For each size range the following parameters were measured: projected area, number of aggregates, width, length, perimeter, and convex envelop. For filaments, the measurements were: number of free filaments and total free filament length. Other parameters were calculated based upon this data: average equivalent diameter, percentage in number of aggregates, percentage in total area, fractal dimensions and a shape factor (P2A), based on the perimeter and on the projected area. Besides, a new parameter was defined in terms of the ratio of filament length to total floc area (LfA). It showed to be very sensitive to the changes in the morphology of the developing granules, and, based upon our granule definition, it was used to determine the granulation time (θg) in our system (120 days). The P_2A factor allowed the quantification of aggregates roughness and was much more sensitive than fractal dimensions. The study was complemented with measurements of specific methanogenic activity (SMA) of the granules in presence of acetate, propionate, butyrate, ethanol and a gas mixture of hydrogen/carbon dioxide.Fundação para a Ciência e a Tecnologia (FCT) - PRAXIS XXI/BD/20325/99 , SFRH/BD/3187/2000
Development of image analysis techniques as a tool to detect and quantify morphological changes in anaerobic sludge : II. application to a granule deterioration process triggered by contact with oleic acid
Image analysis techniques are applied to monitor
the morphological changes in granular sludge present in an
expanded granular sludge blanket (EGSB) reactor fed with
oleic acid. Deterioration of granular sludge was monitored
along the trial period by measuring the percentage of aggregates
smaller than 1 mm (in terms of Feret diameter)
either in terms of projected area or in terms of number
of aggregates. A good correlation was obtained between
these values and the percentage of aggregates smaller
than 1 mm were physically sorted and quantified by the
volatile suspended solid content. The ratio of total filaments
length to cross-sectional area of aggregates defined
as LfA, was applied to quantify the dispersion level of
the granular sludge, which increased until day 141 and
remained almost invariant afterwards. LfA was sensitive to
the sludge deterioration process and was able to indicate,
with the anticipation of about 1 month, the most significant
biomass washout episode that occurred in the trial period.
A mechanism of filaments’ release, detachment and selective
washout was proposed to explain the action of
LfA from this viewpoint. The equivalent diameter of the
bottom aggregates larger than 1 mm increased with the
increase on the amount of long chain fatty acids associated
with the biomass by mechanisms of adsorption, precipitation,
or entrapment. After a threshold value of about 200 mg COD-LCFA gVSS (COD = chemical oxygen demand;
LCFA = long chain fatty acids; VSS = volatile
suspended solids), a migration of granular sludge from the
bottom to a top-floating layer was evident.Instituto Cooperação CientÃfica e Tecnológica Internacional (ICCTI), Ambassade de France in Portugal - Project 203 B4.Fundação para a Ciência e a Tecnologia (FCT) – PRAXIS XXI/BD/20326/99, PRAXIS XXI/BD/20325/99
Monitoring granular stability in an industrial UASB reactor treating brewery wastewater
An industrial scale UASB reactor treating a brewery wastewater was monitored during several
months, in order to assess the usefulness of a morphological parameter relating the filaments length to the
projected area of aggregates, LfA, to anticipate washout problems. It was observed that a selective washout
of filamentous bacterial forms could explain the decrease of the acetoclastic and hydrogenophilic activity
observed in the trial period. This selective washout was predicted by a peak in LfA that occurred just before
a steady increase in the effluent VSS values.Grant SFRH/BD/3187/2000.Fundação para a Ciência e a Tecnologia (FCT) – PRAXIS XXI/BD/20325/99
Efeito da diluição na caracterização da biomassa de sistemas de tratamentos de efluentes por análise de imagem
O estudo da biomassa de sistemas de tratamento de efluentes por análise de
imagem permite avaliar o seu estado de agregação assim como acompanhar as
modificações por ela sofrida quando submetida a choques orgânicos ou hidráulicos.
Certos processos de tratamento trabalham com uma forte concentração em biomassa, o
que obriga a uma diluição prévia. O presente estudo avalia o efeito desta diluição sobre a
caracterização da biomassa aeróbia e anaeróbia (agregada sob a forma de flocos ou
grânulos ou isolada). Os resultados obtidos indicam que este efeito varia segundo a
origem e tipo da biomassa e o tipo de água utilizada na diluição. Foi observado que a
diluição provoca inicialmente um aumento do tamanho dos flocos para em seguida
provocar a sua ruptura. Devido a fortes variações sofridas sobretudo em relação Ã
quantificação das bactérias filamentosas, recomenda-se a opção por uma diluição e sua
manutenção até o fim do experimento.The study by image analysis of biomass in wastewater treatment systems
allow us to evaluate its aggregation state and to relate its changes to changes in the
process operation conditions. In some processes, a high biomass concentration is used
and dilution is necessary for visualisation by optical microscopy. The effect of the
dilution factor on the measured characteristics of aerobic and anaerobic bacteria
(aggregated as flocs or granules, or isolated) has been investigated. The results indicate
that the effect depends on the origin and type of biomass and on the kind of water used
for dilution. Dilution induces initially an increase of the floc size. The flocs are disrupted
when the dilution factor is high. Due to the observed variations on the quantification of
filamentous bacteria, it is recommended to select initially an appropriate dilution factor
and to maintain it for the whole experiment.Brasil. Ministério da Ciência e Tecnologia. Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq).Fundação para a Ciência e a Tecnologia (FCT).Embaixada de França em Portugal.Ministério da Ciência e Tecnologia. Instituto de Cooperação CientÃfica e Tecnológica Internacional (ICCTI)
Strategies to Suppress Hydrogen-Consuming Microorganisms Affect Macro and Micro Scale Structure and Microbiology of Granular Sludge
Treatment of anaerobic granules with heat and
two chemical treatments, contacting with 2-bromoethanesulfonate
(BES) and with BESþChloroform, were applied
to suppress hydrogen-consuming microorganisms. Three
mesophilic expanded granular sludge bed (EGSB) reactors—
RHeat, RBES, and RBESþChlo—were inoculated with
the treated sludges and fed with synthetic sugar-based
wastewater (5 gCOD L 1, HRT 20–12 h). Morphological
integrity of granules and bacterial communities were
assessed by quantitative image analysis and 16S rRNA gene
based techniques, respectively. Hydrogen production
in RHeat was under 300mLH2 L 1 day 1, with a transient
peak of 1,000 mLH2 L 1 day 1 after decreasing HRT.
In RBESþChlo hydrogen production rate did not exceed
300mLH2 L 1 day 1 and there was granule fragmentation,
release of free filaments from aggregates, and decrease of
granule density. In RBES, there was an initial period with
unstable hydrogen production, but a pulse of BES triggered
its production rate to 700 200mLH2 L 1 day 1. This
strategy did not affect granules structure significantly. Bacteria
branching within Clostridiaceae and Ruminococcaceae
were present in this sludge. This work demonstrates that,
methods applied to suppress H2-consuming microorganisms
can cause changes in the macro- and microstructure of
granular sludge, which can be incompatible with the operation
of high-rate reactors.European Community fund FEDER
Contract grant number: FCOMP-01-0124-FEDER-007087; PTDC/BIO/69745/2006; SFRH/
BD/29823/2006; SFRH/BD/48965/2008Fundação para a Ciência e a Tecnologia (FCT