Joao Paulo Bassin | Universidade Federal do Rio de Janeiro (UFRJ) (original) (raw)

Papers by Joao Paulo Bassin

Water research, 2011

An aerobic granular sludge (AGS) reactor was run for 280 days to study the competition between Ph... more An aerobic granular sludge (AGS) reactor was run for 280 days to study the competition between Phosphate and Glycogen Accumulating Organisms (PAOs and GAOs) at high temperatures. Numerous researches have proven that in suspended sludge systems PAOs are outcompeted by GAOs at higher temperatures. In the following study a reactor was operated at 30 °C in which the P-removal efficiency declined from 79% to 32% after 69 days of operation when biomass removal for sludge retention time (SRT) control was established by effluent withdrawal. In a second attempt at 24 °C, efficiency of P-removal remained on average at 71 ± 5% for 76 days. Samples taken from different depths of the sludge bed analysed using Fluorescent in situ hybridization (FISH) microscopy techniques revealed a distinctive microbial community structure: bottom granules contained considerably more Accumulibacter (PAOs) compared to top granules that were dominated by Competibacter (GAOs). In a third phase the SRT was controlle...

Energy Procedia

Thousands of compounds are used and disposed of every day and many of them are not degraded in co... more Thousands of compounds are used and disposed of every day and many of them are not degraded in conventional treatment plants. It is necessary an alternative to eliminate these compounds. This can be done through electrooxidation technology, which was applied in this work to a mixture of pharmaceutical compounds including alprazolam (ALP), clonazepam (CLP), diazepam (DZP), lorazepam (LZP) and carbamazepine (CBZ) at 100 µg.L-1. The mixture was studied with different types of electrolytes and the neurotoxic effect of the treatment was evaluated. The best result was obtained with NaCl (0.5 g.L-1), leading to complete degradation of CLP, LZP and CBZ. Abstract Thousands of compounds are used and disposed of every day and many of them are not degraded in conventional treatment plants. It is necessary an alternative to eliminate these compounds. This can be done through electrooxidation technology, which was applied in this work to a mixture of pharmaceutical compounds including alprazolam (ALP), clonazepam (CLP), diazepam (DZP), lorazepam (LZP) and carbamazepine (CBZ) at 100 µg.L-1. The mixture was studied with different types of electrolytes and the neurotoxic effect of the treatment was evaluated. The best result was obtained with NaCl (0.5 g.L-1), leading to complete degradation of CLP, LZP and CBZ. 462 Morgana Bosio et al. / Energy Procedia 153 (2018) 461-465 2 Morgana Bosio et al. / Energy Procedia 00 (2018) 000-000

Environmental Technology, 2015

The accuracy of the Content should not be relied upon and should be independently verified with p... more The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden.

Bioresource technology, Jan 19, 2015

In this study, the impact of COD/N ratio and feeding regime on the dynamics of heterotrophs and n... more In this study, the impact of COD/N ratio and feeding regime on the dynamics of heterotrophs and nitrifiers in moving-bed biofilm reactors was addressed. Based on DGGE analysis of 16S rRNA genes, the influent COD was found to be the main factor determining the overall bacterial diversity. The amoA-gene-based analysis suggested that the dynamic behavior of the substrate in continuous and pulse-feeding reactors influenced the selection of specific ammonium-oxidizing bacteria (AOB) strains. Furthermore, AOB diversity was directly related to the applied COD/N ratio and ammonium-nitrogen load. Maximum specific ammonium oxidation rates observed under non-substrate-limiting conditions were observed to be proportional to the fraction of nitrifiers within the bacterial community. FISH analysis revealed that Nitrosomonas genus dominated the AOB community in all reactors. Moreover, Nitrospira was found to be the only nitrite-oxidizing bacteria (NOB) in the fully autotrophic system, whereas Nitr...

Environmental Technology, 2015

Petroleum refineries produce large amount of wastewaters, which often contain a wide range of dif... more Petroleum refineries produce large amount of wastewaters, which often contain a wide range of different compounds. Some of these constituents may be recalcitrant and therefore difficult to be treated biologically. This study evaluated the capability of an aerobic submerged fixed-bed reactor (ASFBR) containing a corrugated PVC support material for biofilm attachment to treat a complex and high-strength organic wastewater coming from a petroleum refinery. The reactor operation was divided into five experimental runs which lasted more than 250 days. During the reactor operation, the applied volumetric organic load was varied within the range of 0.5-2.4 kgCOD.m(-3).d(-1). Despite the inherent fluctuations on the characteristics of the complex wastewater and the slight decrease in the reactor performance when the influent organic load was increased, the ASFBR showed good stability and allowed to reach chemical oxygen demand, dissolved organic carbon and total suspended solids removals up to 91%, 90% and 92%, respectively. Appreciable ammonium removal was obtained (around 90%). Some challenging aspects of reactor operation such as biofilm quantification and important biofilm constituents (e.g. polysaccharides (PS) and proteins (PT)) were also addressed in this work. Average PS/volatile attached solids (VAS) and PT/VAS ratios were around 6% and 50%, respectively. The support material promoted biofilm attachment without appreciable loss of solids and allowed long-term operation without clogging. Microscopic observations of the microbial community revealed great diversity of higher organisms, such as protozoa and rotifers, suggesting that toxic compounds found in the wastewater were possibly removed in the biofilm.

Water Research, 2012

Settling velocity is a crucial parameter in granular sludge technology. In this study the effects... more Settling velocity is a crucial parameter in granular sludge technology. In this study the effects of temperature and salt concentrations on settling velocities of granular sludge particles were evaluated. A twofold slower settling velocity for the same granules was observed when the temperature of water decreases from 40 C to 5 C. Settling velocities also decreased with increasing salt concentrations. Experiments showed that when granules were not pre-incubated in a solution with increased salt concentration, they initially floated. The time dependent increase in mass and hence in settling speed of a granule due to salt diffusion into the granule was dependent on the granule diameter. The time needed for full salt equilibrium with the bulk liquid took 1 min for small particles from the top of the sludge bed and up to 30 min for big granules from the bottom of the sludge bed. These results suggest that temperature and salt concentration are important parameters to consider in the design, start-up and operation of granular sludge reactors and monitoring of these parameters will aid in a better control of the sludge management in anaerobic and aerobic granular sludge technology. The observations also give an explanation for previous reports which were suggesting that a start-up of granular sludge reactors is more difficult at low temperatures.

Journal of Hazardous Materials, 2011

Nitrification of saline wastewaters was investigated in bench-scale moving-bed biofilm reactors (... more Nitrification of saline wastewaters was investigated in bench-scale moving-bed biofilm reactors (MBBR). Wastewater from a chemical industry and domestic sewage, both treated by the activated sludge process, were fed to moving-bed reactors. The industrial wastewater contained 8000 mg Cl − /L and the salinity of the treated sewage was gradually increased until that level. Residual substances present in the treated industrial wastewater had a strong inhibitory effect on the nitrification process. Assays to determine inhibitory effects were performed with the industrial wastewater, which was submitted to ozonation and carbon adsorption pretreatments. The latter treatment was effective for dissolved organic carbon (DOC) removal and improved nitrification efficiency. Nitrification percentage of the treated domestic sewage was higher than 90% for all tested chloride concentrations up to 8000 mg/L. Results obtained in a sequencing batch reactor (SBR) were consistent with those attained in the MBBR systems, allowing tertiary nitrification and providing adequate conditions for adaptation of nitrifying microorganisms even under stressing and inhibitory conditions.

Journal of Biomechanics, 2007

Chemosphere, 2012

h i g h l i g h t s " Methods to measure specific rates of NH þ 4 ; NO À 2 and PO 3À 4 in aerobic... more h i g h l i g h t s " Methods to measure specific rates of NH þ 4 ; NO À 2 and PO 3À 4 in aerobic granular sludge are provided. " Optimized conditions for widely used methods to determine specific activities are suggested. " Gradual electron acceptor dosage is the most appropriate method to determine the maximum anoxic Puptake. " The maximum NH þ 4 and NO À 2 oxidation rate can be obtained in aerobic tests with crushed granules. " Biological oxygen monitor tests should be conducted with preaerated (3h) crushed granules.

Biotechnology and Bioengineering, 2012

Two lab-scale aerobic granular sludge sequencing batch reactors were operated at 20 and 30°C and ... more Two lab-scale aerobic granular sludge sequencing batch reactors were operated at 20 and 30°C and compared for phosphorus (P) removal efficiency and microbial community composition. P-removal efficiency was higher at 20°C (>90%) than at 30°C (60%) when the sludge retention time (SRT) was controlled at 30 days by removing excess sludge equally throughout the sludge bed. Samples analyzed by fluorescent in situ hybridization (FISH) indicated a segregation of biomass over the sludge bed: in the upper part, Candidatus Competibacter phosphatis (glycogen-accumulating organisms--GAOs) were dominant while in the bottom, Candidatus Accumulibacter phosphatis (polyphosphate-accumulating organisms--PAOs) dominated. In order to favour PAOs over GAOs and hence improve P-removal at 30°C, the SRT was controlled by discharging biomass mainly from the top of the sludge bed (80% of the excess sludge), while bottom granules were removed in minor proportions (20% of the excess sludge). With the selective sludge removal proposed, 100% P-removal efficiency was obtained in the reactor operated at 30°C. In the meantime, the biomass in the 30°C reactor changed in color from brownish-black to white. Big white granules appeared in this system and were completely dominated by PAOs (more than 90% of the microbial population), showing relatively high ash content compared to other granules. In the reactor operated at 20°C, P-removal efficiency remained stable above 90% regardless of the sludge removal procedure for SRT control. The results obtained in this study stress the importance of sludge discharge mainly from the top as well as in minor proportions from the bottom of the sludge bed to control the SRT in order to prevent significant growth of GAOs and remove enough accumulated P from the system, particularly at high temperatures (e.g., 30°C).

Biodegradation, 2009

A stirred vessel coupled with membrane unit containing cellulose acetate (0.45 m) membrane was u... more A stirred vessel coupled with membrane unit containing cellulose acetate (0.45 m) membrane was used to study the decolorization of anaerobically digested molasses spent wash (MSW). The soil collected from the MSW disposal site was used as inoculum to study the decolorization without addition of any additives. The same inoculum was used over a period of 163 days at room temperature to study the decolorization of 12.5% to 50% (v/v) MSW using different operational conditions. The reactor was entered in to the inhibition mode after the feeding of 50% MSW, which was restored 100% without changing any operational condition. The maximum decolorization obtained for 12.5% (v/v) MSW was 77.22±0.13%. The decolorization achieved for 25%, 37.5% and 50% (v/v) MSW was 70.41±0.12%, 56.47±0.17% and 48.78±0.09% respectively. Increase in the utilization of protein and reducing sugar was observed up to 25% MSW whereas, higher concentration showed decrease in the utilization. Results indicate 63% removal of chemical oxygen demand for 12.5% (v/v) MSW. Membrane flux which was significantly reduced after the feeding of 50% MSW was regenerated without changing the washing procedure however, 35% decrease in sample flux was observed over the continuous use of membrane for the period of 198 days.

Applied Microbiology and Biotechnology, 2014

Salinity can adversely affect the performance of most biological processes involved in wastewater... more Salinity can adversely affect the performance of most biological processes involved in wastewater treatment. The effect of salt on the main conversion processes in an aerobic granular sludge (AGS) process accomplishing simultaneous organic matter, nitrogen, and phosphate removal was evaluated in this work. Hereto, an AGS sequencing batch reactor was subjected to different salt concentrations (0.2 to 20 g Cl − l −1). Granular structure was stable throughout the whole experimental period, although granule size decreased and a significant effluent turbidity was observed at the highest salinity tested. A weaker gel structure at higher salt concentrations was hypothesised to be the cause of such turbidity. Ammonium oxidation was not affected at any of the salt concentrations applied. However, nitrite oxidation was severely affected, especially at 20 g Cl − l −1 , in which a complete inhibition was observed. Consequently, high nitrite accumulation occurred. Phosphate removal was also found to be inhibited at the highest salt concentration tested. Complementary experiments have shown that a cascade inhibition effect took place: first, the deterioration of nitrite oxidation resulted in high nitrite concentrations and this in turn resulted in a detrimental effect to polyphosphateaccumulating organisms. By preventing the occurrence of the nitrification process and therefore avoiding the nitrite accumulation, the effect of salt concentrations on the bio-P removal process was shown to be negligible up to 13 g Cl − l −1. Salt concentrations equal to 20 g Cl − l −1 or higher in absence of nitrite also significantly reduced phosphate removal efficiency in the system.

Applied Microbiology and Biotechnology, 2012

In this study, we analysed the nitrifying microbial community (ammonium-oxidizing bacteria (AOB) ... more In this study, we analysed the nitrifying microbial community (ammonium-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB)) within three different aerobic granular sludge treatment systems as well as within one flocculent sludge system. Granular samples were taken from one pilot plant run on municipal wastewater as well as from two lab-scale reactors. Fluorescent in situ hybridization (FISH) and quantitative PCR (qPCR) showed that Nitrobacter was the dominant NOB in acetate-fed aerobic granules. In the conventional system, both Nitrospira and Nitrobacter were present in similar amounts. Remarkably, the NOB/AOB ratio in aerobic granular sludge was elevated but not in the conventional treatment plant suggesting that the growth of Nitrobacter within aerobic granular sludge, in particular, was partly uncoupled from the lithotrophic nitrite supply from AOB. This was supported by activity measurements which showed an approximately threefold higher nitrite oxidizing capacity than ammonium oxidizing capacity. Based on these findings, two hypotheses were considered: either Nitrobacter grew mixotrophically by acetate-dependent dissimilatory nitrate reduction (ping-pong effect) or a nitrite oxidation/nitrate reduction loop (nitrite loop) occurred in which denitrifiers reduced nitrate to nitrite supplying additional nitrite for the NOB apart from the AOB.

Applied Microbiology and Biotechnology, 2012

bacteria, floc characteristics, and microbial community structure accessed by fluorescent in situ... more bacteria, floc characteristics, and microbial community structure accessed by fluorescent in situ hybridization and polymerase chain reaction-denaturing gradient gel electrophoresis techniques was investigated. Two sequencing batch reactors (SRB 1 and SBR 2) treating synthetic wastewater were subjected to increasing salt concentrations. In SBR 1 , four salt concentrations (5, 10, 15, and 20 g NaCl/L) were tested, while in SBR 2 , only two salt concentrations (10 and 20 g NaCl/L) were applied in a more shock-wise manner. The two different salt adaptation strategies caused different changes in microbial community structure, but did not change the nitrification performance, suggesting that regardless of the different nitrifying bacterial community maintained stable within the salt range tested. Specific ammonium oxidation rates were more affected when salt increase was performed more rapidly and dropped 50% and 60% at 20 g NaCl/L for SBR 1 and SBR 2 , respectively. A gradual increase in NaCl concentration had a positive effect on the settling properties (i.e., reduction of sludge volume index), although it caused a higher amount of suspended solids in the effluent. Higher organisms (e.g., protozoa, nematodes, and rotifers) as well as filamentous bacteria could not withstand the high salt concentrations.

Applied and Environmental Microbiology, 2011

ABSTRACTThe long- and short-term effects of salt on biological nitrogen and phosphorus removal pr... more ABSTRACTThe long- and short-term effects of salt on biological nitrogen and phosphorus removal processes were studied in an aerobic granular sludge reactor. The microbial community structure was investigated by PCR-denaturing gradient gel electrophoresis (DGGE) on 16S rRNA andamoAgenes. PCR products obtained from genomic DNA and from rRNA after reverse transcription were compared to determine the presence of bacteria as well as the metabolically active fraction of bacteria. Fluorescencein situhybridization (FISH) was used to validate the PCR-based results and to quantify the dominant bacterial populations. The results demonstrated that ammonium removal efficiency was not affected by salt concentrations up to 33 g/liter NaCl. Conversely, a high accumulation of nitrite was observed above 22 g/liter NaCl, which coincided with the disappearance ofNitrospirasp. Phosphorus removal was severely affected by gradual salt increase. No P release or uptake was observed at steady-state operation...

The ammonium adsorption properties of aerobic granular sludge, activated sludge and anammox granu... more The ammonium adsorption properties of aerobic granular sludge, activated sludge and anammox granules have been investigated. During operation of a pilot-scale aerobic granular sludge reactor, a positive relation between the influent ammonium concentration and the ammonium adsorbed was observed. Aerobic granular sludge exhibited much higher adsorption capacity compared to activated sludge and anammox granules. At an equilibrium ammonium concentration of 30 mg N/L, adsorption obtained with activated sludge and anammox granules was around 0.2 mg NH4-N/g VSS, while aerobic granular sludge from lab- and pilot-scale exhibited an adsorption of 1.7 and 0.9 mg NH4-N/g VSS, respectively. No difference in the ammonium adsorption was observed in lab-scale reactors operated at different temperatures (20 and 30 °C). In a lab-scale reactor fed with saline wastewater, we observed that the amount of ammonium adsorbed considerably decreased when the salt concentration increased. The results indicate that adsorption or better ion exchange of ammonium should be incorporated into models for nitrification/denitrification, certainly when aerobic granular sludge is used.

Critical Care, 2012

The removal of nutrients such as nitrogen and phosphorus from both domestic and industrial wastew... more The removal of nutrients such as nitrogen and phosphorus from both domestic and industrial wastewaters is imperative since they potentially harm the environment. One of the main consequences of excessive availability of nitrogen and phosphorus in aquatic ecosystems (freshwater, marine and estuarine) is the overgrowth of algae and other aquatic plants, a phenomenon designated as eutrophication. Algae and aquatic plants induce depletion of oxygen in water basins, resulting in massive death of eukaryotic organisms in the ecosystem and a decrease in biodiversity. Human activities have increased the input of nutrients to aquatic resources beyond its natural capacity to assimilate them, resulting in acceleration of the eutrophication process. Nutrient removal from wastewaters by biological processes is cost effective and offers many advantages compared to physical-chemical processes. Essentially, biological nitrogen (nitrification and denitrification) and phosphorus removal involves a series of biochemical processes carried out in an appropriate sequence of aerobic, anoxic and anaerobic environments. In conventional activated sludge-based processes, these conditions are provided in separate tanks (multistage treatment processes), demanding large land areas for the wastewater treatment plant installation. The low biomass concentrations in the traditional activated sludge systems and especially the need for clarifiers for biosolid-liquid separation contribute to the large footprint of activated sludge-based sewage treatment plants. Generally, wastewater treatment systems are located in densely populated urban areas, where space is scarce. In this context, new compact technologies with a reduced footprint are required. Moreover, the increasing pollution in water resources as a consequence of enormous discharge of untreated sewage into receiving waters imposes the necessity for upgrading the wastewater treatment plants to meet stringent effluent regulations posed by environmental agencies. Most of the new technological developments in compact sewage treatment processes rely on biofilm- and granular-based systems with a high biomass retention capacity, resulting in higher volumetric treatment capacities and minimized space requirement. The research described in this thesis aimed at the investigation of several important aspects regarding biological nutrient removal in compact systems such as moving-bed biofilm reactors (MBBR), aerobic granular sludge reactors (AGS) and sequencing batch reactors with suspended biomass. Different issues related to organic matter, nitrogen and phosphorus removal were addressed in this work. The first aim of the research described in this thesis was to investigate how different operational conditions (e.g., influent composition and feeding regime) influence the development of nitrifying biofilms in moving bed biofilm reactors (MBBR). In this particular study, the nitrification process was also carefully evaluated. To fulfil the objectives, analytical methods and molecular techniques (such as fluorescent in situ hybridization) were combined to provide further insight into the enrichment of the biofilm for nitrifiers. In order to obtain better control of the different moving bed systems operated in parallel and to understand the effect of particular variables on biofilm development and nitrification process, a synthetic medium was used to feed all the MBBRs. Strategies to speed up the formation of enriched nitrifying biofilms and the feasibility of applying a sequentially operated moving bed reactor for the treatment of high-strength ammonium wastewater are described in this work, presented in Chapter 2. It was shown that the application of a heterotrophic start-up phase decreased the time required for the development of nitrifying biofilms in MBBRs. The findings of this research can potentially be used in industrial applications, most notably when nitrification should be accomplished in wastewaters with limited or no organic carbon. Inoculation of a MBBR operated on a pulse-feeding sequencing batch regime with biomass detached from other MBBR systems was also found to reduce the time necessary to develop an enriched nitrifying biofilm. Aerobic granular sludge (AGS) is a promising technology for wastewater treatment. Several studies have investigated the simultaneous nitrogen and phosphate removal in AGS systems. However, none of them specified the impact of specific subpopulations of polyphosphate-accumulating organisms (PAOs) on phosphate and nitrogen conversions. Recent research efforts exploring the characteristics of PAOs have shown new insights about these microorganisms, classifying them according to their capability of using nitrite and/or nitrate as electron acceptor for denitrification. Taking into account the new discoveries regarding these organisms, a complete characterization of the main process conversions occurring in aerobic granular sludge reactors applied for simultaneous...

Water research, 2011

An aerobic granular sludge (AGS) reactor was run for 280 days to study the competition between Ph... more An aerobic granular sludge (AGS) reactor was run for 280 days to study the competition between Phosphate and Glycogen Accumulating Organisms (PAOs and GAOs) at high temperatures. Numerous researches have proven that in suspended sludge systems PAOs are outcompeted by GAOs at higher temperatures. In the following study a reactor was operated at 30 °C in which the P-removal efficiency declined from 79% to 32% after 69 days of operation when biomass removal for sludge retention time (SRT) control was established by effluent withdrawal. In a second attempt at 24 °C, efficiency of P-removal remained on average at 71 ± 5% for 76 days. Samples taken from different depths of the sludge bed analysed using Fluorescent in situ hybridization (FISH) microscopy techniques revealed a distinctive microbial community structure: bottom granules contained considerably more Accumulibacter (PAOs) compared to top granules that were dominated by Competibacter (GAOs). In a third phase the SRT was controlle...

Energy Procedia

Thousands of compounds are used and disposed of every day and many of them are not degraded in co... more Thousands of compounds are used and disposed of every day and many of them are not degraded in conventional treatment plants. It is necessary an alternative to eliminate these compounds. This can be done through electrooxidation technology, which was applied in this work to a mixture of pharmaceutical compounds including alprazolam (ALP), clonazepam (CLP), diazepam (DZP), lorazepam (LZP) and carbamazepine (CBZ) at 100 µg.L-1. The mixture was studied with different types of electrolytes and the neurotoxic effect of the treatment was evaluated. The best result was obtained with NaCl (0.5 g.L-1), leading to complete degradation of CLP, LZP and CBZ. Abstract Thousands of compounds are used and disposed of every day and many of them are not degraded in conventional treatment plants. It is necessary an alternative to eliminate these compounds. This can be done through electrooxidation technology, which was applied in this work to a mixture of pharmaceutical compounds including alprazolam (ALP), clonazepam (CLP), diazepam (DZP), lorazepam (LZP) and carbamazepine (CBZ) at 100 µg.L-1. The mixture was studied with different types of electrolytes and the neurotoxic effect of the treatment was evaluated. The best result was obtained with NaCl (0.5 g.L-1), leading to complete degradation of CLP, LZP and CBZ. 462 Morgana Bosio et al. / Energy Procedia 153 (2018) 461-465 2 Morgana Bosio et al. / Energy Procedia 00 (2018) 000-000

Environmental Technology, 2015

The accuracy of the Content should not be relied upon and should be independently verified with p... more The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden.

Bioresource technology, Jan 19, 2015

In this study, the impact of COD/N ratio and feeding regime on the dynamics of heterotrophs and n... more In this study, the impact of COD/N ratio and feeding regime on the dynamics of heterotrophs and nitrifiers in moving-bed biofilm reactors was addressed. Based on DGGE analysis of 16S rRNA genes, the influent COD was found to be the main factor determining the overall bacterial diversity. The amoA-gene-based analysis suggested that the dynamic behavior of the substrate in continuous and pulse-feeding reactors influenced the selection of specific ammonium-oxidizing bacteria (AOB) strains. Furthermore, AOB diversity was directly related to the applied COD/N ratio and ammonium-nitrogen load. Maximum specific ammonium oxidation rates observed under non-substrate-limiting conditions were observed to be proportional to the fraction of nitrifiers within the bacterial community. FISH analysis revealed that Nitrosomonas genus dominated the AOB community in all reactors. Moreover, Nitrospira was found to be the only nitrite-oxidizing bacteria (NOB) in the fully autotrophic system, whereas Nitr...

Environmental Technology, 2015

Petroleum refineries produce large amount of wastewaters, which often contain a wide range of dif... more Petroleum refineries produce large amount of wastewaters, which often contain a wide range of different compounds. Some of these constituents may be recalcitrant and therefore difficult to be treated biologically. This study evaluated the capability of an aerobic submerged fixed-bed reactor (ASFBR) containing a corrugated PVC support material for biofilm attachment to treat a complex and high-strength organic wastewater coming from a petroleum refinery. The reactor operation was divided into five experimental runs which lasted more than 250 days. During the reactor operation, the applied volumetric organic load was varied within the range of 0.5-2.4 kgCOD.m(-3).d(-1). Despite the inherent fluctuations on the characteristics of the complex wastewater and the slight decrease in the reactor performance when the influent organic load was increased, the ASFBR showed good stability and allowed to reach chemical oxygen demand, dissolved organic carbon and total suspended solids removals up to 91%, 90% and 92%, respectively. Appreciable ammonium removal was obtained (around 90%). Some challenging aspects of reactor operation such as biofilm quantification and important biofilm constituents (e.g. polysaccharides (PS) and proteins (PT)) were also addressed in this work. Average PS/volatile attached solids (VAS) and PT/VAS ratios were around 6% and 50%, respectively. The support material promoted biofilm attachment without appreciable loss of solids and allowed long-term operation without clogging. Microscopic observations of the microbial community revealed great diversity of higher organisms, such as protozoa and rotifers, suggesting that toxic compounds found in the wastewater were possibly removed in the biofilm.

Water Research, 2012

Settling velocity is a crucial parameter in granular sludge technology. In this study the effects... more Settling velocity is a crucial parameter in granular sludge technology. In this study the effects of temperature and salt concentrations on settling velocities of granular sludge particles were evaluated. A twofold slower settling velocity for the same granules was observed when the temperature of water decreases from 40 C to 5 C. Settling velocities also decreased with increasing salt concentrations. Experiments showed that when granules were not pre-incubated in a solution with increased salt concentration, they initially floated. The time dependent increase in mass and hence in settling speed of a granule due to salt diffusion into the granule was dependent on the granule diameter. The time needed for full salt equilibrium with the bulk liquid took 1 min for small particles from the top of the sludge bed and up to 30 min for big granules from the bottom of the sludge bed. These results suggest that temperature and salt concentration are important parameters to consider in the design, start-up and operation of granular sludge reactors and monitoring of these parameters will aid in a better control of the sludge management in anaerobic and aerobic granular sludge technology. The observations also give an explanation for previous reports which were suggesting that a start-up of granular sludge reactors is more difficult at low temperatures.

Journal of Hazardous Materials, 2011

Nitrification of saline wastewaters was investigated in bench-scale moving-bed biofilm reactors (... more Nitrification of saline wastewaters was investigated in bench-scale moving-bed biofilm reactors (MBBR). Wastewater from a chemical industry and domestic sewage, both treated by the activated sludge process, were fed to moving-bed reactors. The industrial wastewater contained 8000 mg Cl − /L and the salinity of the treated sewage was gradually increased until that level. Residual substances present in the treated industrial wastewater had a strong inhibitory effect on the nitrification process. Assays to determine inhibitory effects were performed with the industrial wastewater, which was submitted to ozonation and carbon adsorption pretreatments. The latter treatment was effective for dissolved organic carbon (DOC) removal and improved nitrification efficiency. Nitrification percentage of the treated domestic sewage was higher than 90% for all tested chloride concentrations up to 8000 mg/L. Results obtained in a sequencing batch reactor (SBR) were consistent with those attained in the MBBR systems, allowing tertiary nitrification and providing adequate conditions for adaptation of nitrifying microorganisms even under stressing and inhibitory conditions.

Journal of Biomechanics, 2007

Chemosphere, 2012

h i g h l i g h t s " Methods to measure specific rates of NH þ 4 ; NO À 2 and PO 3À 4 in aerobic... more h i g h l i g h t s " Methods to measure specific rates of NH þ 4 ; NO À 2 and PO 3À 4 in aerobic granular sludge are provided. " Optimized conditions for widely used methods to determine specific activities are suggested. " Gradual electron acceptor dosage is the most appropriate method to determine the maximum anoxic Puptake. " The maximum NH þ 4 and NO À 2 oxidation rate can be obtained in aerobic tests with crushed granules. " Biological oxygen monitor tests should be conducted with preaerated (3h) crushed granules.

Biotechnology and Bioengineering, 2012

Two lab-scale aerobic granular sludge sequencing batch reactors were operated at 20 and 30°C and ... more Two lab-scale aerobic granular sludge sequencing batch reactors were operated at 20 and 30°C and compared for phosphorus (P) removal efficiency and microbial community composition. P-removal efficiency was higher at 20°C (>90%) than at 30°C (60%) when the sludge retention time (SRT) was controlled at 30 days by removing excess sludge equally throughout the sludge bed. Samples analyzed by fluorescent in situ hybridization (FISH) indicated a segregation of biomass over the sludge bed: in the upper part, Candidatus Competibacter phosphatis (glycogen-accumulating organisms--GAOs) were dominant while in the bottom, Candidatus Accumulibacter phosphatis (polyphosphate-accumulating organisms--PAOs) dominated. In order to favour PAOs over GAOs and hence improve P-removal at 30°C, the SRT was controlled by discharging biomass mainly from the top of the sludge bed (80% of the excess sludge), while bottom granules were removed in minor proportions (20% of the excess sludge). With the selective sludge removal proposed, 100% P-removal efficiency was obtained in the reactor operated at 30°C. In the meantime, the biomass in the 30°C reactor changed in color from brownish-black to white. Big white granules appeared in this system and were completely dominated by PAOs (more than 90% of the microbial population), showing relatively high ash content compared to other granules. In the reactor operated at 20°C, P-removal efficiency remained stable above 90% regardless of the sludge removal procedure for SRT control. The results obtained in this study stress the importance of sludge discharge mainly from the top as well as in minor proportions from the bottom of the sludge bed to control the SRT in order to prevent significant growth of GAOs and remove enough accumulated P from the system, particularly at high temperatures (e.g., 30°C).

Biodegradation, 2009

A stirred vessel coupled with membrane unit containing cellulose acetate (0.45 m) membrane was u... more A stirred vessel coupled with membrane unit containing cellulose acetate (0.45 m) membrane was used to study the decolorization of anaerobically digested molasses spent wash (MSW). The soil collected from the MSW disposal site was used as inoculum to study the decolorization without addition of any additives. The same inoculum was used over a period of 163 days at room temperature to study the decolorization of 12.5% to 50% (v/v) MSW using different operational conditions. The reactor was entered in to the inhibition mode after the feeding of 50% MSW, which was restored 100% without changing any operational condition. The maximum decolorization obtained for 12.5% (v/v) MSW was 77.22±0.13%. The decolorization achieved for 25%, 37.5% and 50% (v/v) MSW was 70.41±0.12%, 56.47±0.17% and 48.78±0.09% respectively. Increase in the utilization of protein and reducing sugar was observed up to 25% MSW whereas, higher concentration showed decrease in the utilization. Results indicate 63% removal of chemical oxygen demand for 12.5% (v/v) MSW. Membrane flux which was significantly reduced after the feeding of 50% MSW was regenerated without changing the washing procedure however, 35% decrease in sample flux was observed over the continuous use of membrane for the period of 198 days.

Applied Microbiology and Biotechnology, 2014

Salinity can adversely affect the performance of most biological processes involved in wastewater... more Salinity can adversely affect the performance of most biological processes involved in wastewater treatment. The effect of salt on the main conversion processes in an aerobic granular sludge (AGS) process accomplishing simultaneous organic matter, nitrogen, and phosphate removal was evaluated in this work. Hereto, an AGS sequencing batch reactor was subjected to different salt concentrations (0.2 to 20 g Cl − l −1). Granular structure was stable throughout the whole experimental period, although granule size decreased and a significant effluent turbidity was observed at the highest salinity tested. A weaker gel structure at higher salt concentrations was hypothesised to be the cause of such turbidity. Ammonium oxidation was not affected at any of the salt concentrations applied. However, nitrite oxidation was severely affected, especially at 20 g Cl − l −1 , in which a complete inhibition was observed. Consequently, high nitrite accumulation occurred. Phosphate removal was also found to be inhibited at the highest salt concentration tested. Complementary experiments have shown that a cascade inhibition effect took place: first, the deterioration of nitrite oxidation resulted in high nitrite concentrations and this in turn resulted in a detrimental effect to polyphosphateaccumulating organisms. By preventing the occurrence of the nitrification process and therefore avoiding the nitrite accumulation, the effect of salt concentrations on the bio-P removal process was shown to be negligible up to 13 g Cl − l −1. Salt concentrations equal to 20 g Cl − l −1 or higher in absence of nitrite also significantly reduced phosphate removal efficiency in the system.

Applied Microbiology and Biotechnology, 2012

In this study, we analysed the nitrifying microbial community (ammonium-oxidizing bacteria (AOB) ... more In this study, we analysed the nitrifying microbial community (ammonium-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB)) within three different aerobic granular sludge treatment systems as well as within one flocculent sludge system. Granular samples were taken from one pilot plant run on municipal wastewater as well as from two lab-scale reactors. Fluorescent in situ hybridization (FISH) and quantitative PCR (qPCR) showed that Nitrobacter was the dominant NOB in acetate-fed aerobic granules. In the conventional system, both Nitrospira and Nitrobacter were present in similar amounts. Remarkably, the NOB/AOB ratio in aerobic granular sludge was elevated but not in the conventional treatment plant suggesting that the growth of Nitrobacter within aerobic granular sludge, in particular, was partly uncoupled from the lithotrophic nitrite supply from AOB. This was supported by activity measurements which showed an approximately threefold higher nitrite oxidizing capacity than ammonium oxidizing capacity. Based on these findings, two hypotheses were considered: either Nitrobacter grew mixotrophically by acetate-dependent dissimilatory nitrate reduction (ping-pong effect) or a nitrite oxidation/nitrate reduction loop (nitrite loop) occurred in which denitrifiers reduced nitrate to nitrite supplying additional nitrite for the NOB apart from the AOB.

Applied Microbiology and Biotechnology, 2012

bacteria, floc characteristics, and microbial community structure accessed by fluorescent in situ... more bacteria, floc characteristics, and microbial community structure accessed by fluorescent in situ hybridization and polymerase chain reaction-denaturing gradient gel electrophoresis techniques was investigated. Two sequencing batch reactors (SRB 1 and SBR 2) treating synthetic wastewater were subjected to increasing salt concentrations. In SBR 1 , four salt concentrations (5, 10, 15, and 20 g NaCl/L) were tested, while in SBR 2 , only two salt concentrations (10 and 20 g NaCl/L) were applied in a more shock-wise manner. The two different salt adaptation strategies caused different changes in microbial community structure, but did not change the nitrification performance, suggesting that regardless of the different nitrifying bacterial community maintained stable within the salt range tested. Specific ammonium oxidation rates were more affected when salt increase was performed more rapidly and dropped 50% and 60% at 20 g NaCl/L for SBR 1 and SBR 2 , respectively. A gradual increase in NaCl concentration had a positive effect on the settling properties (i.e., reduction of sludge volume index), although it caused a higher amount of suspended solids in the effluent. Higher organisms (e.g., protozoa, nematodes, and rotifers) as well as filamentous bacteria could not withstand the high salt concentrations.

Applied and Environmental Microbiology, 2011

ABSTRACTThe long- and short-term effects of salt on biological nitrogen and phosphorus removal pr... more ABSTRACTThe long- and short-term effects of salt on biological nitrogen and phosphorus removal processes were studied in an aerobic granular sludge reactor. The microbial community structure was investigated by PCR-denaturing gradient gel electrophoresis (DGGE) on 16S rRNA andamoAgenes. PCR products obtained from genomic DNA and from rRNA after reverse transcription were compared to determine the presence of bacteria as well as the metabolically active fraction of bacteria. Fluorescencein situhybridization (FISH) was used to validate the PCR-based results and to quantify the dominant bacterial populations. The results demonstrated that ammonium removal efficiency was not affected by salt concentrations up to 33 g/liter NaCl. Conversely, a high accumulation of nitrite was observed above 22 g/liter NaCl, which coincided with the disappearance ofNitrospirasp. Phosphorus removal was severely affected by gradual salt increase. No P release or uptake was observed at steady-state operation...

The ammonium adsorption properties of aerobic granular sludge, activated sludge and anammox granu... more The ammonium adsorption properties of aerobic granular sludge, activated sludge and anammox granules have been investigated. During operation of a pilot-scale aerobic granular sludge reactor, a positive relation between the influent ammonium concentration and the ammonium adsorbed was observed. Aerobic granular sludge exhibited much higher adsorption capacity compared to activated sludge and anammox granules. At an equilibrium ammonium concentration of 30 mg N/L, adsorption obtained with activated sludge and anammox granules was around 0.2 mg NH4-N/g VSS, while aerobic granular sludge from lab- and pilot-scale exhibited an adsorption of 1.7 and 0.9 mg NH4-N/g VSS, respectively. No difference in the ammonium adsorption was observed in lab-scale reactors operated at different temperatures (20 and 30 °C). In a lab-scale reactor fed with saline wastewater, we observed that the amount of ammonium adsorbed considerably decreased when the salt concentration increased. The results indicate that adsorption or better ion exchange of ammonium should be incorporated into models for nitrification/denitrification, certainly when aerobic granular sludge is used.

Critical Care, 2012

The removal of nutrients such as nitrogen and phosphorus from both domestic and industrial wastew... more The removal of nutrients such as nitrogen and phosphorus from both domestic and industrial wastewaters is imperative since they potentially harm the environment. One of the main consequences of excessive availability of nitrogen and phosphorus in aquatic ecosystems (freshwater, marine and estuarine) is the overgrowth of algae and other aquatic plants, a phenomenon designated as eutrophication. Algae and aquatic plants induce depletion of oxygen in water basins, resulting in massive death of eukaryotic organisms in the ecosystem and a decrease in biodiversity. Human activities have increased the input of nutrients to aquatic resources beyond its natural capacity to assimilate them, resulting in acceleration of the eutrophication process. Nutrient removal from wastewaters by biological processes is cost effective and offers many advantages compared to physical-chemical processes. Essentially, biological nitrogen (nitrification and denitrification) and phosphorus removal involves a series of biochemical processes carried out in an appropriate sequence of aerobic, anoxic and anaerobic environments. In conventional activated sludge-based processes, these conditions are provided in separate tanks (multistage treatment processes), demanding large land areas for the wastewater treatment plant installation. The low biomass concentrations in the traditional activated sludge systems and especially the need for clarifiers for biosolid-liquid separation contribute to the large footprint of activated sludge-based sewage treatment plants. Generally, wastewater treatment systems are located in densely populated urban areas, where space is scarce. In this context, new compact technologies with a reduced footprint are required. Moreover, the increasing pollution in water resources as a consequence of enormous discharge of untreated sewage into receiving waters imposes the necessity for upgrading the wastewater treatment plants to meet stringent effluent regulations posed by environmental agencies. Most of the new technological developments in compact sewage treatment processes rely on biofilm- and granular-based systems with a high biomass retention capacity, resulting in higher volumetric treatment capacities and minimized space requirement. The research described in this thesis aimed at the investigation of several important aspects regarding biological nutrient removal in compact systems such as moving-bed biofilm reactors (MBBR), aerobic granular sludge reactors (AGS) and sequencing batch reactors with suspended biomass. Different issues related to organic matter, nitrogen and phosphorus removal were addressed in this work. The first aim of the research described in this thesis was to investigate how different operational conditions (e.g., influent composition and feeding regime) influence the development of nitrifying biofilms in moving bed biofilm reactors (MBBR). In this particular study, the nitrification process was also carefully evaluated. To fulfil the objectives, analytical methods and molecular techniques (such as fluorescent in situ hybridization) were combined to provide further insight into the enrichment of the biofilm for nitrifiers. In order to obtain better control of the different moving bed systems operated in parallel and to understand the effect of particular variables on biofilm development and nitrification process, a synthetic medium was used to feed all the MBBRs. Strategies to speed up the formation of enriched nitrifying biofilms and the feasibility of applying a sequentially operated moving bed reactor for the treatment of high-strength ammonium wastewater are described in this work, presented in Chapter 2. It was shown that the application of a heterotrophic start-up phase decreased the time required for the development of nitrifying biofilms in MBBRs. The findings of this research can potentially be used in industrial applications, most notably when nitrification should be accomplished in wastewaters with limited or no organic carbon. Inoculation of a MBBR operated on a pulse-feeding sequencing batch regime with biomass detached from other MBBR systems was also found to reduce the time necessary to develop an enriched nitrifying biofilm. Aerobic granular sludge (AGS) is a promising technology for wastewater treatment. Several studies have investigated the simultaneous nitrogen and phosphate removal in AGS systems. However, none of them specified the impact of specific subpopulations of polyphosphate-accumulating organisms (PAOs) on phosphate and nitrogen conversions. Recent research efforts exploring the characteristics of PAOs have shown new insights about these microorganisms, classifying them according to their capability of using nitrite and/or nitrate as electron acceptor for denitrification. Taking into account the new discoveries regarding these organisms, a complete characterization of the main process conversions occurring in aerobic granular sludge reactors applied for simultaneous...