A potential limit for water recycling in industrial processes is the increase of compounds concen... more A potential limit for water recycling in industrial processes is the increase of compounds concentration in the remaining effluent whom biological treatability can be reduced. In this paper a procedure aimed at evaluating the compatibility of a recycling system with an existing WasteWater Treatment Plant (WWTP) is described. This is an objective of the LIFE funded project BATTLE (BAT for water reuse in TextiLE SMEs). The procedure is applied to a textile company (Stamperia di Martinengo srl) and its on-site biological WWTP as a case study. The effects of the water recycling scheme on the existing WWTP have been evaluated by means of an integrated approach of respirometric, titration and physico-chemical analysis and the implementation of an ASM1 model for the simulation of biological processes. In this case titration trials did not reveal any inhibitory effect on biological processes due to biodegradable and not biodegradable compound for water recycling ratio from 30% to 60%. Respirometric and titration tests allowed to successfully implement an ASM1 model which revealed that exceeding of COD and nitrogen limits set by law for effluent discharge is not expected even in the case of 50% recycling ratio.
Confronto tra i risultati ottenibili utilizzando due diverse
lampade UV, una a bassa ed una a me... more Confronto tra i risultati ottenibili utilizzando due diverse
lampade UV, una a bassa ed una a media pressione, nel trattamento combinato UV/H2O2 di soluzioni colorate
The role that tannins play in tannery wastewater treatment has been evaluated employing a pilot M... more The role that tannins play in tannery wastewater treatment has been evaluated employing a pilot Membrane Bioreactor (MBR) plant and a full scale Conventional Activated Sludge Process (CASP) plant conducted in parallel. The proposed methodology has established the preliminary use of respirometry to examine the biodegradability of a selection of commercial products (synthetic and natural tannins); the subsequent analysis, by means of spectrophotometric reading and RP-IPC (Reverse-Phase Ion-Pair) liquid chromatography, estimates the concentrations of natural tannins and naphthalenesulfonic tanning agents in the influent and effluent samples. The results show that a consistent percentage of the Total Organic Carbon (TOC) in the effluent of the biological phase of the plants is attributable to the presence of natural and synthetic (Sulfonated Naphthalene-Formaldehyde Condensates, SNFC) tannins (17% and 14% respectively). The titrimetric tests that were aimed at evaluating the levels of inhibition on the nitrifying biomass samples did not allow a direct inhibiting effect to be associated with the concentration levels of the tannin in the effluent. Nonetheless, the reduced specific growth rates of ammonium and nitrite oxidising bacteria imply that a strong environmental pressure is present, if not necessarily due to the concentration of tannins, due to the wastewater as a whole. The differences that have emerged by comparing the two technologies (CASP and MBR), in regards to the role that tannins play in terms of biodegradability, did not appear to be significant.
The application of respirometric and titrimetric techniques to evaluate kinetic parameters and st... more The application of respirometric and titrimetric techniques to evaluate kinetic parameters and stoichiometry of the sulphide-oxidising biomass is a new promising approach for biotechnological sulphide oxidation process monitoring. It was possible to estimate the yield coefficients of each oxidation step of sulphide to elemental sulphur and to sulphate using respirometric tests, while evaluating the behaviour of the biomass in endogenous conditions. Furthermore, it was demonstrated how the combined application of titrimetric and respirometric techniques enabled the monitoring of sulphur and sulphate formation as a function of the environmental conditions. This approach provided valuable information of the biological sulphide oxidation processes and preliminary results may be used as a starting point for the formulation and use of a mathematical model.
In questo lavoro si presentano i risultati di un’indagine
sperimentale rivolta a verificare l’ap... more In questo lavoro si presentano i risultati di un’indagine
sperimentale rivolta a verificare l’applicabilità e l’efficacia
dei bioreattori a membrana (MBR) nel trattamento dei reflui dell’industria del cuoio.
In this paper, a modified version of the IWA-ASM1 model capable of correctly simulating the produ... more In this paper, a modified version of the IWA-ASM1 model capable of correctly simulating the production of solids over a wide range of solids retention time (SRT) is presented. The parameters of the modified model have been estimated by integrating the results of respirometric and titrimetric tests with those of studies conducted on pilot scale plants that treat industrial wastewaters of differing characteristics. On the basis of the experimental results and their subsequent processing, it appears that the production of solids may be satisfactorily estimated using the modified model in which fractions XP and XI are supposed to be hydrolysable with a first-order kinetic. In the cases that were examined, the constant of the aforementioned kinetics was estimated to be ki=0.012 d-1 and ki=0.014 d-1, for tannery and textile wastewater respectively. A reliable calibration of the parameter ki was possible when data relative to the experiment conducted in the pilot plants for no less than 60 d and in conditions of complete solid retention was utilized.
In leather tanning industrial areas sulphide management represents a major problem. However, biol... more In leather tanning industrial areas sulphide management represents a major problem. However, biological sulphide oxidation to sulphur represents a convenient solution to this problem. Elemental sulphur is easy to separate and the process is highly efficient in terms of energy consumption and effluent quality. As the oxidation process is performed by specialized bacteria, selection of an appropriate microbial community is fundamental for obtaining a good yield.
Sulphur oxidizing bacteria (SOB) represent a wide-ranging and highly diversified group of microorganisms with the capability of oxidizing reduced sulphur compounds. Therefore, it is useful to select new microbes that are able to perform this process efficiently. For this purpose, an experimental membrane bioreactor for sulphide oxidation was set up, and the selected microbial community was characterized by constructing 16S rRNA gene libraries and subsequent
screening of clones. Fluorescence in situ hybridization (FISH) was then used to assess the relative abundance of different bacterial groups. Sulphide oxidation to elemental sulphur proceeded in an efficient (up to 79% conversion) and stable way in the bioreactor. Both analysis of clone libraries and FISH experiments revealed that the dominant operational taxonomic unit (OTU) in the bioreactor was constituted by Gammaproteobacteria belonging to the Halothiobacillaceae family. FISH performed with the specifically designed probe tios_434 demonstrated that this OTU constituted 90.671.3% of the bacterial community. Smaller fractions were represented by bacteria belonging to the classes Betaproteobacteria, Alphaproteobacteria, Deltaproteobacteria, Clostridia, Mollicutes, Sphingobacteria, Bacteroidetes and Chlorobia. Phylogenetic analysis revealed that clone sequences from the dominant OTU formed a stable clade (here called the TIOS44 cluster), within the Halothiobacillaceae family, with sequences from many organisms that have not yet been validly described. The data indicated that bacteria belonging to the TIOS44 cluster were responsible for the oxidation process.
Nitrite and nitrate were compared as electron acceptors to select for denitrifying phosphorous ac... more Nitrite and nitrate were compared as electron acceptors to select for denitrifying phosphorous accumulating
organisms (DPAO) in two integrated fixed film activated sludge (IFAS 1 and IFAS 2) systems operated
as sequencing batch reactors. The bench-scale experiment lasted one year and synthetic wastewater
was used as feed. During anoxic conditions 20 mg NO3
–N L1 were dosed into IFAS-1 and 20 mg NO2–
N L1 were dosed into IFAS-2. Long term phosphorous and ammonia removal via nitritation were
achieved in both systems and both attached and suspended biomass contributed to phosphorous and
ammonia removal. DPAO showed no specific adaptation to the electron acceptor as evidenced by short
term switch of feeding with nitrate or nitrite. Anoxic phosphorus uptake rate was significantly higher
with nitrite than with nitrate. Results showed that DPAO activity with nitrite could be integrated into
attached and suspended biomass of IFAS systems in long term operation.
A pilot scale test on a biotrickling filter packed with polyurethane foam cubes was carried out f... more A pilot scale test on a biotrickling filter packed with polyurethane foam cubes was carried out for 110 d at
high volumetric mass load (up to 280 g m3
bed h1) with the aim of studying the accumulation of solids in
the treatment of H2S.
Removal rate up to 245 g m3
bed h1 was obtained; however, an accumulation of gypsum, elemental
sulphur and, above all, inert biomass was identified as the cause of an increased pressure drop over
the long term. A mathematical model was applied and calibrated with the experimental results to
describe the accumulation of biomass. The model was capable of describing the accumulation of solids
and, corresponding to a solids retention time of 50 d, the observed yield resulted in 0.07 g of solids produced
g1 H2S removed. Respirometric tests showed that heterotrophic activity is inhibited at low pH
(pH < 2.3), and the contribution to biomass removal through decay was negligible.
A bench-scale sequencing batch reactor was used to study factors affecting the endogenous
decay ... more A bench-scale sequencing batch reactor was used to study factors affecting the endogenous
decay of the ammonium oxidizing biomass (AOB) in different operating conditions.
AOB decay was very sensitive to oxygen concentration, and increased up to 0.4 d1 for
oxygen concentration of 7 mg O2 L1. The decay in anaerobic conditions was shown to be
very low (0.03 d1) when compared to literature data.
The effect of nitrite and nitrate on AOB decay was also studied. The correlation was quite
weak suggesting that both nitrate and nitrite absence had little impact on decay which is
contrary to what is typically assumed in some of the existing process models. A simple
expression for the decay of AOB was proposed, calibrated and validated using the results of
batch kinetic tests and of the continuous sequencing batch reactor monitoring.
The maximum specific growth rates of both ammonium oxidizing bacteria (AOB) and nitrite oxidizing... more The maximum specific growth rates of both ammonium oxidizing bacteria (AOB) and nitrite oxidizing
bacteria (NOB) were investigated under varying aerobic solids retention time (SRTa) and in the presence/
absence of anoxic (alternating) conditions. Two bench SBRs, reactor R1 and R2, were run in parallel
for 150 d. Reactor R1 was operated in aerobic conditions while R2 operated in alternating anoxic/aerobic
conditions. The feed (synthetic wastewater), temperature, hydraulic retention time and mixing were
identical in both reactors. The SRTa in both reactors was, sequentially, set at four values: 5, 4, 3 and 2 d.
Kinetic tests with the biomasses from both reactors were carried out to estimate the maximum specific
growth rates (lmax) at each tested SRTa and decay rates, in both aerobic and anoxic conditions. The kinetic
parameters of nitrifier were estimated through the calibration of a two step nitrification–denitrification
activated sludge model.
ENVIRONMENTAL ENGINEERING AND MANAGEMENT JOURNAL, 2014
A pilot scale Upflow Anaerobic Filter (UAF) treating tannery wastewaters was operated for 160 day... more A pilot scale Upflow Anaerobic Filter (UAF) treating tannery wastewaters was operated for 160 days. The UAF was fed with low
COD/SO4
2- ratio (SO4
2- = 1810 mg L-1, CODtotal = 2530 mg L-1) for the investigation of sulphate and COD removal as a function
of substrates limitation and ammonia and sulphide inhibition. Sulphate-reducing bacteria (SRB) out-competed methanogenic
bacteria due to the low influent COD/SO4
2- ratio, the high concentration of sulphide and the presence of inhibiting compounds in
tannery wastewater. An average sulphate removal of 53% and an average COD removal of 42% were obtained. Ammonia and
sulphide concentrations were found to play a major role in the process, and their effect was quantified. A simplified mathematical
model was calibrated under semi-steady conditions and no substrate limitation, and used to describe sulphide and ammonia
inhibition. Half-inhibition constants for ammonia (KNH4) and sulphide (KHS) of 180 mg L-1 and 480 mg L-1, respectively, were
obtained. No improvements of the biodegradability between the untreated tannery wastewater and the UAF effluent were
observed through respirometric tests.
In this study a pilot-scale membrane bioreactor (MBR) and a conventional activated sludge plant (... more In this study a pilot-scale membrane bioreactor (MBR) and a conventional activated sludge plant (CASP),
treating the same tannery wastewaters and in the same operating conditions, have been compared in
order to evaluate the overall treatment efficiency, the presence and distribution of Gram negative bacteria
and the kinetics of nitrifying bacteria. Process efficiency was evaluated in terms of organic and nitrogen
compounds: the MBR showed a higher COD removal (+4%) and a more stable and complete
nitrification. The Gram negative bacteria were detected by fluorescent in situ hybridization (FISH) with
phylogenetic probes monitoring of a-, b- and c-Proteobacteria, of the main ammonia-oxidizing bacteria
(AOB) and nitrite-oxidizing bacteria of the Nitrobacter and Nitrospira genera. The results showed that
the main differences between the two sludges were: the higher abundance of a- and c-Proteobacteria
in the MBR bioreactor and the presence of AOB aggregates only on the surfaces of MBR flocs. Finally,
the titrimetric (pH-stat, DO-stat) tests showed similar values of the kinetic parameters of the nitrifiers
both in MBR and CASP sludge.
Abstract A pilot-scale membrane bioreactor (MBR) and
a conventional activated sludge system (CAS... more Abstract A pilot-scale membrane bioreactor (MBR) and
a conventional activated sludge system (CAS) were in
parallel operated to investigate the impact of the separation
technology on the structure and functionality of the selected
microbial community. Microbial communities as well
as nitrogen removal efficiency of the biomass were characterized.
Kinetics and microbial community structure
turned out to be duly correlated. The impact of the separation
technology on selective conditions and, in particular,
the higher variability of solid separation efficiency in CAS
with respect to MBR pilot plant possibly represented the
main factor influencing the selection of bacterial communities.
Concerning nitrifiers, bacteria of the genus Nitrospira
were predominant in the MBR. This was in accordance with
kinetics of nitrite-oxidizing bacteria that suggested the
presence of k-strategists, while r-strategists were selected in
the CAS plant, possibly because of the presence of transient
higher concentrations of nitrite (in the range of 0.05–0.18
and of 0.05–4.4 mg NO
2 -N L-1 in the MBR and CAS
effluents, respectively). An unexpectedly high presence of bacteria belonging to two specific phylogenetic clades of
Planctomycetes was found in both reactors.
Summer holidays as break-point in shaping a tannery sludge microbial community around a stable co... more Summer holidays as break-point in shaping a tannery sludge microbial community around a stable core microbiotaRecently, several investigations focused on the discovery of a bacterial consortium shared among different wastewater treatment plants (WWTPs). Nevertheless, the definition of a core microbiota over time represents the necessary counterpart in order to unravel the dynamics of bacterial communities in
these environments. Here we performed a monthly survey on the bacterial community of a consortial industrial plant. Objectives of this study were: (1) to identify a core microbiota constant over time; (2) to evaluate the temporal dynamics of the community during one year. A conspicuous and diversified core microbiota is constituted by operational taxonomic units which are present throughout the year in the plant. Community composition data confirm that the presence and abundance of bacteria in WWTPs is highly consistent at high taxonomic level. Our results indicate however a difference in microbial community structure between two groups of samples, identifying the summer holiday period as the break-point. Changes in the structure of the microbial community occur otherwise gradually, one month after another. Further studies will clarify how the size and diversity of the core microbiota could affect the observed dynamics.
Free nitrous acid (FNA) inhibition of anoxic and aerobic phosphorous removal in an integrated fix... more Free nitrous acid (FNA) inhibition of anoxic and aerobic phosphorous removal in an integrated fixed-film activated sludge (IFAS) system with different FNA adaptation was investigated. A bench scale sequencing batch reactor (SBR) with plastic media was operated in an anaerobic/anoxic/aerobic sequence. During the anoxic period, nitrite was fed into the reactor at different concentrations to select for biomass adapted to 0.06 and 0.4μg HNO2-NL-1 of FNA during anoxic stage in Phase I and II, respectively. Long term anoxic/aerobic phosphorus removal was achieved in the IFAS reactor in both phases. In Phase I, aerobic phosphorous uptake was inhibited at higher level compared with anoxic phosphorus uptake. In Phase II, DPAO in both suspended and attached forms could adapt and were not inhibited at FNA level four times higher than the adapted concentration. The PAO's aerobic activity in Phase II, did not show significant adaptation and was inhibited at slightly lower level compared with that in Phase I. The FNA inhibition of aerobic phosphorous uptake rate in attached biomass was 20% of that in suspended forms. In batch testes with the FNA level was raised to three times the adapted concentration, the contribution of attached biomass to overall anoxic and aerobic phosphorus uptake increased by 20% and 39%, respectively. The attached biomass could allow an IFAS system to be less inhibited and better maintain phosphorous removal at sudden FNA inhibition events
The impact of pH variation on aerobic granular sludge stability and performance was investigated.... more The impact of pH variation on aerobic granular sludge stability and performance was investigated. A nine-day alkaline (pH ¼ 9) and acidic (pH ¼ 6) pH shocks were imposed on mature granules with simultaneous chemical oxygen demand (COD), nitrogen and phosphorus removal. The imposed
alkaline pH shock (pH 9) reduced nitrogen and phosphorus removal efficiency from 88% and 98% to 66% and 50%, respectively, with no further recovery. However, acidic pH shock (pH 6) did not have major impacts on nutrient removal and the removal efficiencies recovered to their initial values after three days of operation under the new pH condition. Operating the reactors under alkaline pH induced granules breakage and resulted in an increased solids concentration in the effluent and in a significant decrease in the size of the bio-particles, while, acidic pH did not have significant impacts on granules stability. Changes in chemical structure and composition of extracellular polymeric substances (EPS) matrix were suggested as the main factors inducing granules instability under high pH.
A potential limit for water recycling in industrial processes is the increase of compounds concen... more A potential limit for water recycling in industrial processes is the increase of compounds concentration in the remaining effluent whom biological treatability can be reduced. In this paper a procedure aimed at evaluating the compatibility of a recycling system with an existing WasteWater Treatment Plant (WWTP) is described. This is an objective of the LIFE funded project BATTLE (BAT for water reuse in TextiLE SMEs). The procedure is applied to a textile company (Stamperia di Martinengo srl) and its on-site biological WWTP as a case study. The effects of the water recycling scheme on the existing WWTP have been evaluated by means of an integrated approach of respirometric, titration and physico-chemical analysis and the implementation of an ASM1 model for the simulation of biological processes. In this case titration trials did not reveal any inhibitory effect on biological processes due to biodegradable and not biodegradable compound for water recycling ratio from 30% to 60%. Respirometric and titration tests allowed to successfully implement an ASM1 model which revealed that exceeding of COD and nitrogen limits set by law for effluent discharge is not expected even in the case of 50% recycling ratio.
Confronto tra i risultati ottenibili utilizzando due diverse
lampade UV, una a bassa ed una a me... more Confronto tra i risultati ottenibili utilizzando due diverse
lampade UV, una a bassa ed una a media pressione, nel trattamento combinato UV/H2O2 di soluzioni colorate
The role that tannins play in tannery wastewater treatment has been evaluated employing a pilot M... more The role that tannins play in tannery wastewater treatment has been evaluated employing a pilot Membrane Bioreactor (MBR) plant and a full scale Conventional Activated Sludge Process (CASP) plant conducted in parallel. The proposed methodology has established the preliminary use of respirometry to examine the biodegradability of a selection of commercial products (synthetic and natural tannins); the subsequent analysis, by means of spectrophotometric reading and RP-IPC (Reverse-Phase Ion-Pair) liquid chromatography, estimates the concentrations of natural tannins and naphthalenesulfonic tanning agents in the influent and effluent samples. The results show that a consistent percentage of the Total Organic Carbon (TOC) in the effluent of the biological phase of the plants is attributable to the presence of natural and synthetic (Sulfonated Naphthalene-Formaldehyde Condensates, SNFC) tannins (17% and 14% respectively). The titrimetric tests that were aimed at evaluating the levels of inhibition on the nitrifying biomass samples did not allow a direct inhibiting effect to be associated with the concentration levels of the tannin in the effluent. Nonetheless, the reduced specific growth rates of ammonium and nitrite oxidising bacteria imply that a strong environmental pressure is present, if not necessarily due to the concentration of tannins, due to the wastewater as a whole. The differences that have emerged by comparing the two technologies (CASP and MBR), in regards to the role that tannins play in terms of biodegradability, did not appear to be significant.
The application of respirometric and titrimetric techniques to evaluate kinetic parameters and st... more The application of respirometric and titrimetric techniques to evaluate kinetic parameters and stoichiometry of the sulphide-oxidising biomass is a new promising approach for biotechnological sulphide oxidation process monitoring. It was possible to estimate the yield coefficients of each oxidation step of sulphide to elemental sulphur and to sulphate using respirometric tests, while evaluating the behaviour of the biomass in endogenous conditions. Furthermore, it was demonstrated how the combined application of titrimetric and respirometric techniques enabled the monitoring of sulphur and sulphate formation as a function of the environmental conditions. This approach provided valuable information of the biological sulphide oxidation processes and preliminary results may be used as a starting point for the formulation and use of a mathematical model.
In questo lavoro si presentano i risultati di un’indagine
sperimentale rivolta a verificare l’ap... more In questo lavoro si presentano i risultati di un’indagine
sperimentale rivolta a verificare l’applicabilità e l’efficacia
dei bioreattori a membrana (MBR) nel trattamento dei reflui dell’industria del cuoio.
In this paper, a modified version of the IWA-ASM1 model capable of correctly simulating the produ... more In this paper, a modified version of the IWA-ASM1 model capable of correctly simulating the production of solids over a wide range of solids retention time (SRT) is presented. The parameters of the modified model have been estimated by integrating the results of respirometric and titrimetric tests with those of studies conducted on pilot scale plants that treat industrial wastewaters of differing characteristics. On the basis of the experimental results and their subsequent processing, it appears that the production of solids may be satisfactorily estimated using the modified model in which fractions XP and XI are supposed to be hydrolysable with a first-order kinetic. In the cases that were examined, the constant of the aforementioned kinetics was estimated to be ki=0.012 d-1 and ki=0.014 d-1, for tannery and textile wastewater respectively. A reliable calibration of the parameter ki was possible when data relative to the experiment conducted in the pilot plants for no less than 60 d and in conditions of complete solid retention was utilized.
In leather tanning industrial areas sulphide management represents a major problem. However, biol... more In leather tanning industrial areas sulphide management represents a major problem. However, biological sulphide oxidation to sulphur represents a convenient solution to this problem. Elemental sulphur is easy to separate and the process is highly efficient in terms of energy consumption and effluent quality. As the oxidation process is performed by specialized bacteria, selection of an appropriate microbial community is fundamental for obtaining a good yield.
Sulphur oxidizing bacteria (SOB) represent a wide-ranging and highly diversified group of microorganisms with the capability of oxidizing reduced sulphur compounds. Therefore, it is useful to select new microbes that are able to perform this process efficiently. For this purpose, an experimental membrane bioreactor for sulphide oxidation was set up, and the selected microbial community was characterized by constructing 16S rRNA gene libraries and subsequent
screening of clones. Fluorescence in situ hybridization (FISH) was then used to assess the relative abundance of different bacterial groups. Sulphide oxidation to elemental sulphur proceeded in an efficient (up to 79% conversion) and stable way in the bioreactor. Both analysis of clone libraries and FISH experiments revealed that the dominant operational taxonomic unit (OTU) in the bioreactor was constituted by Gammaproteobacteria belonging to the Halothiobacillaceae family. FISH performed with the specifically designed probe tios_434 demonstrated that this OTU constituted 90.671.3% of the bacterial community. Smaller fractions were represented by bacteria belonging to the classes Betaproteobacteria, Alphaproteobacteria, Deltaproteobacteria, Clostridia, Mollicutes, Sphingobacteria, Bacteroidetes and Chlorobia. Phylogenetic analysis revealed that clone sequences from the dominant OTU formed a stable clade (here called the TIOS44 cluster), within the Halothiobacillaceae family, with sequences from many organisms that have not yet been validly described. The data indicated that bacteria belonging to the TIOS44 cluster were responsible for the oxidation process.
Nitrite and nitrate were compared as electron acceptors to select for denitrifying phosphorous ac... more Nitrite and nitrate were compared as electron acceptors to select for denitrifying phosphorous accumulating
organisms (DPAO) in two integrated fixed film activated sludge (IFAS 1 and IFAS 2) systems operated
as sequencing batch reactors. The bench-scale experiment lasted one year and synthetic wastewater
was used as feed. During anoxic conditions 20 mg NO3
–N L1 were dosed into IFAS-1 and 20 mg NO2–
N L1 were dosed into IFAS-2. Long term phosphorous and ammonia removal via nitritation were
achieved in both systems and both attached and suspended biomass contributed to phosphorous and
ammonia removal. DPAO showed no specific adaptation to the electron acceptor as evidenced by short
term switch of feeding with nitrate or nitrite. Anoxic phosphorus uptake rate was significantly higher
with nitrite than with nitrate. Results showed that DPAO activity with nitrite could be integrated into
attached and suspended biomass of IFAS systems in long term operation.
A pilot scale test on a biotrickling filter packed with polyurethane foam cubes was carried out f... more A pilot scale test on a biotrickling filter packed with polyurethane foam cubes was carried out for 110 d at
high volumetric mass load (up to 280 g m3
bed h1) with the aim of studying the accumulation of solids in
the treatment of H2S.
Removal rate up to 245 g m3
bed h1 was obtained; however, an accumulation of gypsum, elemental
sulphur and, above all, inert biomass was identified as the cause of an increased pressure drop over
the long term. A mathematical model was applied and calibrated with the experimental results to
describe the accumulation of biomass. The model was capable of describing the accumulation of solids
and, corresponding to a solids retention time of 50 d, the observed yield resulted in 0.07 g of solids produced
g1 H2S removed. Respirometric tests showed that heterotrophic activity is inhibited at low pH
(pH < 2.3), and the contribution to biomass removal through decay was negligible.
A bench-scale sequencing batch reactor was used to study factors affecting the endogenous
decay ... more A bench-scale sequencing batch reactor was used to study factors affecting the endogenous
decay of the ammonium oxidizing biomass (AOB) in different operating conditions.
AOB decay was very sensitive to oxygen concentration, and increased up to 0.4 d1 for
oxygen concentration of 7 mg O2 L1. The decay in anaerobic conditions was shown to be
very low (0.03 d1) when compared to literature data.
The effect of nitrite and nitrate on AOB decay was also studied. The correlation was quite
weak suggesting that both nitrate and nitrite absence had little impact on decay which is
contrary to what is typically assumed in some of the existing process models. A simple
expression for the decay of AOB was proposed, calibrated and validated using the results of
batch kinetic tests and of the continuous sequencing batch reactor monitoring.
The maximum specific growth rates of both ammonium oxidizing bacteria (AOB) and nitrite oxidizing... more The maximum specific growth rates of both ammonium oxidizing bacteria (AOB) and nitrite oxidizing
bacteria (NOB) were investigated under varying aerobic solids retention time (SRTa) and in the presence/
absence of anoxic (alternating) conditions. Two bench SBRs, reactor R1 and R2, were run in parallel
for 150 d. Reactor R1 was operated in aerobic conditions while R2 operated in alternating anoxic/aerobic
conditions. The feed (synthetic wastewater), temperature, hydraulic retention time and mixing were
identical in both reactors. The SRTa in both reactors was, sequentially, set at four values: 5, 4, 3 and 2 d.
Kinetic tests with the biomasses from both reactors were carried out to estimate the maximum specific
growth rates (lmax) at each tested SRTa and decay rates, in both aerobic and anoxic conditions. The kinetic
parameters of nitrifier were estimated through the calibration of a two step nitrification–denitrification
activated sludge model.
ENVIRONMENTAL ENGINEERING AND MANAGEMENT JOURNAL, 2014
A pilot scale Upflow Anaerobic Filter (UAF) treating tannery wastewaters was operated for 160 day... more A pilot scale Upflow Anaerobic Filter (UAF) treating tannery wastewaters was operated for 160 days. The UAF was fed with low
COD/SO4
2- ratio (SO4
2- = 1810 mg L-1, CODtotal = 2530 mg L-1) for the investigation of sulphate and COD removal as a function
of substrates limitation and ammonia and sulphide inhibition. Sulphate-reducing bacteria (SRB) out-competed methanogenic
bacteria due to the low influent COD/SO4
2- ratio, the high concentration of sulphide and the presence of inhibiting compounds in
tannery wastewater. An average sulphate removal of 53% and an average COD removal of 42% were obtained. Ammonia and
sulphide concentrations were found to play a major role in the process, and their effect was quantified. A simplified mathematical
model was calibrated under semi-steady conditions and no substrate limitation, and used to describe sulphide and ammonia
inhibition. Half-inhibition constants for ammonia (KNH4) and sulphide (KHS) of 180 mg L-1 and 480 mg L-1, respectively, were
obtained. No improvements of the biodegradability between the untreated tannery wastewater and the UAF effluent were
observed through respirometric tests.
In this study a pilot-scale membrane bioreactor (MBR) and a conventional activated sludge plant (... more In this study a pilot-scale membrane bioreactor (MBR) and a conventional activated sludge plant (CASP),
treating the same tannery wastewaters and in the same operating conditions, have been compared in
order to evaluate the overall treatment efficiency, the presence and distribution of Gram negative bacteria
and the kinetics of nitrifying bacteria. Process efficiency was evaluated in terms of organic and nitrogen
compounds: the MBR showed a higher COD removal (+4%) and a more stable and complete
nitrification. The Gram negative bacteria were detected by fluorescent in situ hybridization (FISH) with
phylogenetic probes monitoring of a-, b- and c-Proteobacteria, of the main ammonia-oxidizing bacteria
(AOB) and nitrite-oxidizing bacteria of the Nitrobacter and Nitrospira genera. The results showed that
the main differences between the two sludges were: the higher abundance of a- and c-Proteobacteria
in the MBR bioreactor and the presence of AOB aggregates only on the surfaces of MBR flocs. Finally,
the titrimetric (pH-stat, DO-stat) tests showed similar values of the kinetic parameters of the nitrifiers
both in MBR and CASP sludge.
Abstract A pilot-scale membrane bioreactor (MBR) and
a conventional activated sludge system (CAS... more Abstract A pilot-scale membrane bioreactor (MBR) and
a conventional activated sludge system (CAS) were in
parallel operated to investigate the impact of the separation
technology on the structure and functionality of the selected
microbial community. Microbial communities as well
as nitrogen removal efficiency of the biomass were characterized.
Kinetics and microbial community structure
turned out to be duly correlated. The impact of the separation
technology on selective conditions and, in particular,
the higher variability of solid separation efficiency in CAS
with respect to MBR pilot plant possibly represented the
main factor influencing the selection of bacterial communities.
Concerning nitrifiers, bacteria of the genus Nitrospira
were predominant in the MBR. This was in accordance with
kinetics of nitrite-oxidizing bacteria that suggested the
presence of k-strategists, while r-strategists were selected in
the CAS plant, possibly because of the presence of transient
higher concentrations of nitrite (in the range of 0.05–0.18
and of 0.05–4.4 mg NO
2 -N L-1 in the MBR and CAS
effluents, respectively). An unexpectedly high presence of bacteria belonging to two specific phylogenetic clades of
Planctomycetes was found in both reactors.
Summer holidays as break-point in shaping a tannery sludge microbial community around a stable co... more Summer holidays as break-point in shaping a tannery sludge microbial community around a stable core microbiotaRecently, several investigations focused on the discovery of a bacterial consortium shared among different wastewater treatment plants (WWTPs). Nevertheless, the definition of a core microbiota over time represents the necessary counterpart in order to unravel the dynamics of bacterial communities in
these environments. Here we performed a monthly survey on the bacterial community of a consortial industrial plant. Objectives of this study were: (1) to identify a core microbiota constant over time; (2) to evaluate the temporal dynamics of the community during one year. A conspicuous and diversified core microbiota is constituted by operational taxonomic units which are present throughout the year in the plant. Community composition data confirm that the presence and abundance of bacteria in WWTPs is highly consistent at high taxonomic level. Our results indicate however a difference in microbial community structure between two groups of samples, identifying the summer holiday period as the break-point. Changes in the structure of the microbial community occur otherwise gradually, one month after another. Further studies will clarify how the size and diversity of the core microbiota could affect the observed dynamics.
Free nitrous acid (FNA) inhibition of anoxic and aerobic phosphorous removal in an integrated fix... more Free nitrous acid (FNA) inhibition of anoxic and aerobic phosphorous removal in an integrated fixed-film activated sludge (IFAS) system with different FNA adaptation was investigated. A bench scale sequencing batch reactor (SBR) with plastic media was operated in an anaerobic/anoxic/aerobic sequence. During the anoxic period, nitrite was fed into the reactor at different concentrations to select for biomass adapted to 0.06 and 0.4μg HNO2-NL-1 of FNA during anoxic stage in Phase I and II, respectively. Long term anoxic/aerobic phosphorus removal was achieved in the IFAS reactor in both phases. In Phase I, aerobic phosphorous uptake was inhibited at higher level compared with anoxic phosphorus uptake. In Phase II, DPAO in both suspended and attached forms could adapt and were not inhibited at FNA level four times higher than the adapted concentration. The PAO's aerobic activity in Phase II, did not show significant adaptation and was inhibited at slightly lower level compared with that in Phase I. The FNA inhibition of aerobic phosphorous uptake rate in attached biomass was 20% of that in suspended forms. In batch testes with the FNA level was raised to three times the adapted concentration, the contribution of attached biomass to overall anoxic and aerobic phosphorus uptake increased by 20% and 39%, respectively. The attached biomass could allow an IFAS system to be less inhibited and better maintain phosphorous removal at sudden FNA inhibition events
The impact of pH variation on aerobic granular sludge stability and performance was investigated.... more The impact of pH variation on aerobic granular sludge stability and performance was investigated. A nine-day alkaline (pH ¼ 9) and acidic (pH ¼ 6) pH shocks were imposed on mature granules with simultaneous chemical oxygen demand (COD), nitrogen and phosphorus removal. The imposed
alkaline pH shock (pH 9) reduced nitrogen and phosphorus removal efficiency from 88% and 98% to 66% and 50%, respectively, with no further recovery. However, acidic pH shock (pH 6) did not have major impacts on nutrient removal and the removal efficiencies recovered to their initial values after three days of operation under the new pH condition. Operating the reactors under alkaline pH induced granules breakage and resulted in an increased solids concentration in the effluent and in a significant decrease in the size of the bio-particles, while, acidic pH did not have significant impacts on granules stability. Changes in chemical structure and composition of extracellular polymeric substances (EPS) matrix were suggested as the main factors inducing granules instability under high pH.
L’efficienza del processo di digestione anaerobica applicato ai fanghi conciari è valutata attrav... more L’efficienza del processo di digestione anaerobica applicato ai fanghi conciari è valutata attraverso test a scala banco e scala pilota. La peculiarità delle matrici selezionate ha richiesto l’applicazione di pretrattamenti mirati e l’utilizzo di inoculi acclimatati per il raggiungimento di rese significative. Test a scala banco hanno permesso di identificare la sequenza ottimale di pretrattamento e le condizioni operative in grado di massimizzare l’efficienza del processo di digestione in termini di metano prodotto. Sono stati inoltre condotti test in continuo di co-digestione di fango conciario e fango civile che hanno permesso di identificare le condizioni limite di trattamento delle matrici selezionate nel corso del progetto. Summary The efficiency of the anaerobic of tannery sludge have been evaluated through tests in bench and pilot scale. The characteristics of the selected tannery sludges required the application of targeted pretreatments and the use of acclimated inoculum to achieve significant yields. Bench scale tests allowed to identify the optimal sequence of pre-treatments and operational conditions to maximize the efficiency of the digestion process in terms of methane production. Continuous co-digestion test were conducted using tannery and civil sludge to identify the boundary conditions for the treatment of the selected tannery sludge.
Un Filtro Anaerobico a flusso ascensionale (UAF) a scala pilota con letto costituito da supporti ... more Un Filtro Anaerobico a flusso ascensionale (UAF) a scala pilota con letto costituito da supporti plastici e' stato utilizzato per il trattamento anaerobico di reflui conciari precedentemente soggetti a sedimentazione primaria. Il refluo trattato presenta un elevato rapporto tra Solfati (1800 mgSO 4 2-/l) e COD (2261 mg/l), tale da causare fenomeni di competizione tra la biomassa solfatoriduttrice e quella metanigena. Nell'arco dei 7 mesi di test, operando con 24 h di tempo di ritenzione idraulica, non si è osservata produzione di metano. Sono state ottenute, invece, rimozioni dei solfati superiori al 90% e del COD comprese tra il 20 ed il 60%. Riduzioni del 50% dell'efficienza di rimozione percentuale dei solfati sono state ottenute con concentrazioni di NH 4 + e di solfuri superiori rispettivamente a 120 mg/L e 250 mg/L. Il trattamento combinato anaerobico+aerobico non determina un aumento della biodegradabilita' complessiva del refluo rispetto al solo trattamento aerobico. L'applicazione di un processo a due stadi (solfatoriduzione-metanizzazone) appare dunque interessante da valutare, riducendo al minimo l'influenza della solfato riduzione sul processo di produzione di metano nel secondo stadio. Summary A pilot scale Anaerobic Filter (UAF), with plastic filling material, was used for anaerobic treatment of tannery wastewaters. The test lasted 7 months and the hydraulic retention time was 24 h. Due to the influent Sulphate/COD ratio, the sulphate reducing bacteria outcompeted the methanogens and no production of methane was observed. With HRT of 24h a removal of sulphate higher than 90% was obtained in the presence of a COD removal in the range 20-60%. A marked loss of the sulphate reduction efficiency with concentrations of NH 4 + and sulphide higher, respectively, than 120 mg/l and 250 mg/l were
Anoxic phosphorous uptake and partial nitrification in integrated fixed film activated sludge (IF... more Anoxic phosphorous uptake and partial nitrification in integrated fixed film activated sludge (IFAS) system
Role of solids retention time and alternating aerobic-anoxic conditions in the selection of nitri... more Role of solids retention time and alternating aerobic-anoxic conditions in the selection of nitrifying biomass in activated sludge systems
In Italia ci sono oltre 1300 concerie, con una produzione annua di 130 milioni di metri quadrati ... more In Italia ci sono oltre 1300 concerie, con una produzione annua di 130 milioni di metri quadrati di pellami e 35.000 tonnellate di cuoio. Del Distretto Conciario Toscano fanno parte 560 aziende. Il processo industriale genera un grande quantitativo di rifiuti solidi e 15-30m3 di acqua reflua per tonnellata di prodotto finito. Il Consorzio Cuoiodepur (San Miniato-Pisa) tratta reflui derivanti dai processi di concia al vegetale. All’impianto confluiscono mediamente 1.300.000m3/anno di reflui, da cui deriva una produzione di fango con caratteristiche quali: elevato carico organico; alto contenuto di metalli; presenza di solfati e composti lentamente biodegradabili. L’attuale filiera di trattamento fanghi prevede l’ispessimento, la disidratazione, l’essiccamento termico e la produzione di fertilizzante mediante miscelazione con sottoprodotti organici del processo industriale di concia. Nonostante i vantaggi legati al recupero agronomico, negli ultimi anni la ricerca è volta allo sfruttamento, mediante processi anaerobici, dell’elevato potenziale energetico dei fanghi conciari e di relative miscele con sottoprodotti del processo industriale. In letteratura sono presenti test anaerobici su fanghi da concia al cromo, mentre mancano prove con fanghi derivanti dalla concia al vegetale, questi ultimi contengono probabili inibenti come i tannini. La ricerca ha lo scopo di valutare la fattibilità tecnica ed economica del trattamento anaerobico dei fanghi primari derivanti da concia al vegetale mediante test a scala di laboratorio in condizioni mesofile. Miscele in proporzioni crescenti (fino a 1:1.5) di fango conciario e di mixed liquor di un impianto a fanghi attivi che tratta reflui civili sono state utilizzate come alimentazione per circa 8 mesi, di due reattori a scala banco alimentati in continuo. I risultati hanno permesso di identificare nell’acclimatamento della biomassa un fattore determinante per l’efficienza del processo e di ottenere rimozioni di SSV del 24% con una produzione media di biogas di 0.129 Nm3/kgSSV e 0.160 Nm3/kgSSV rispettivamente.
volumetrici (50–280 g/m letto 3 h) superiori a quelli dei convezionali BTF, bassi tempi di contat... more volumetrici (50–280 g/m letto 3 h) superiori a quelli dei convezionali BTF, bassi tempi di contatto e concentrazioni influenti di H 2 S fortemente variabili nel tempo (60–250 mg/m 3). Il pH e' stato mantenuto all'interno del range (1,6–1.8) mediante l'aggiunta di acqua di pozzo arricchita con macronutrienti. In condizioni di funzionamento ottimali sono state raggiunte elevatissime capacita' di eliminazione dell H 2 S (fino a 230 g H 2 S/m 3 letto h), comparabili con quelle tipiche dei convenzionali scrubber chimici; tali efficienze di rimozione sono diminuite, parallelamente all'insorgere di elevate perdite di carico nel letto filtrante, all'aumentare della quantità di biomassa non attiva nel letto. L'elevata concentrazione di materiale inerte che comporta, tra l'altro,una progressiva riduzione dell'altezza del letto (> 30%) e un aumento delle perdite di carico (>100%) è apparso il fattore determinate nel calo delle prestazioni. Summary A pilot scale biotrickling filter (BTF) was used to evaluate the long term response of the system to highly loaded streams of H 2 S. The experiment was carried out with high volumetric mass loads (from 50 to 280 g/m bed 3 h), short contact time and highly variable H 2 S concentrations (65 – 250 mg/m 3). Polyurethane foam cubes were used as filling media. The pH was controlled between 1.6 and 1.8 through the dosing of tap water enriched with macronutrients. The system showed very high volumetric removal rates (up to 230 mg H 2 S/m
A Conventional Activated Sludge (CAS) system and a Membrane Bioreactor (MBR) were bioaugmented wi... more A Conventional Activated Sludge (CAS) system and a Membrane Bioreactor (MBR) were bioaugmented with a same nitrifying biomass selected in a side-stream MBR fed with a high nitrogen-loaded influent. Microbial communities evolution was monitored and comparatively analysed through bio-molecular investigation (FISH and T-RFLP techniques) followed by statistical analyses. The bioaugmentation process caused, indeed, a conspicuous increase of nitrifying bacteria of the genera Nitrosomonas and Nitrobacter in both the inoculated CAS and MBR reactors. The overall structure of the microbial community was actually changed in these reactors, although not evolving toward an overlapping with that of the side-stream community. Finally, the effect of bioaugmentation was significantly more pronounced on the biomass of the MBR reactor with respect to the CAS
Authotrophic denitrification with sulphide using nitrate as electron acceptor were investigated a... more Authotrophic denitrification with sulphide using nitrate as electron acceptor were investigated at bench scale at different HRT (5 and 20 d). The results indicated that the process allows to achieve complete sulphide removal in all testes conditions. Tested sulphide loads were estimated from the H2S produced in a pilot scale anaerobic digester treating vegetable tannery primary sludge; nitrogen loads originated from the nitrification of the supernatant. Average nitrogen removal efficiencies higher than 80% were observed in all the tested conditions once steady state was reached.
Due to sulphide limitation, an incomplete denitrification have been observed and nitrite and thiosulphate tend to accumulate especially in the presence of variable environmental conditions.
Autotrophic denitrification efficiency and intermediate sulphur compounds production have been simulated using a two step denitrification and three step sulphide oxidation model. The model allowed to estimate those parameters that can affect the production of biomass in a hypotetic real scale Biotrickling filter for biogas desulphurization, as the SOB yield factor (0.6 mgXSOB(COD) mgS-1) and decay coefficients (0.06 d-1).
SULFUR OXIDIZING BACTERIA COMMUNITY: CHARACTERIZATION AND MONITORING IN A REACTOR FOR SULFIDE REM... more SULFUR OXIDIZING BACTERIA COMMUNITY: CHARACTERIZATION AND MONITORING IN A REACTOR FOR SULFIDE REMOVAL FROM INDUSTRIAL WASTE.
Artificial ecosystems as models for studying microbial communities influenced by nitrogen and sul... more Artificial ecosystems as models for studying microbial communities influenced by nitrogen and sulfur compounds: a one-year monitoring of tannery wastewaters
Exploring the complex microbial community of activated sludge sampled from an industrial tannery... more Exploring the complex microbial community of activated sludge sampled from an industrial tannery wastewater treatment plant by Illumina MiSeq
Microbial community dynamics in an industrial tannery wastewater treatment plant: a one-year moni... more Microbial community dynamics in an industrial tannery wastewater treatment plant: a one-year monitoring by Illumina sequencing
SELECTION OF AUTOCHTHONOUS AND ALLOCHTHONOUS FUNGAL STRAINS FOR THE TREATMENT OF RECALCITRANT WAS... more SELECTION OF AUTOCHTHONOUS AND ALLOCHTHONOUS FUNGAL STRAINS FOR THE TREATMENT OF RECALCITRANT WASTEWATERS
This book describes the latest research advances, innovations, and applications in the field of w... more This book describes the latest research advances, innovations, and applications in the field of water management and environmental engineering as presented by leading researchers, engineers, life scientists and practitioners from around the world at the Frontiers International Conference on Wastewater Treatment (FICWTM), held in Palermo, Italy in May 2017. The topics covered are highly diverse and include the physical processes of mixing and dispersion, biological developments and mathematical modeling, such as computational fluid dynamics in wastewater, MBBR and hybrid systems, membrane bioreactors, anaerobic digestion, reduction of greenhouse gases from wastewater treatment plants, and energy optimization.
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Articles by G. Munz
COD/SO4
2- ratio (SO4
2- = 1810 mg L-1, CODtotal = 2530 mg L-1) for the investigation of sulphate and COD removal as a function
of substrates limitation and ammonia and sulphide inhibition. Sulphate-reducing bacteria (SRB) out-competed methanogenic
bacteria due to the low influent COD/SO4
2- ratio, the high concentration of sulphide and the presence of inhibiting compounds in
tannery wastewater. An average sulphate removal of 53% and an average COD removal of 42% were obtained. Ammonia and
sulphide concentrations were found to play a major role in the process, and their effect was quantified. A simplified mathematical
model was calibrated under semi-steady conditions and no substrate limitation, and used to describe sulphide and ammonia
inhibition. Half-inhibition constants for ammonia (KNH4) and sulphide (KHS) of 180 mg L-1 and 480 mg L-1, respectively, were
obtained. No improvements of the biodegradability between the untreated tannery wastewater and the UAF effluent were
observed through respirometric tests.
a conventional activated sludge system (CAS) were in
parallel operated to investigate the impact of the separation
technology on the structure and functionality of the selected
microbial community. Microbial communities as well
as nitrogen removal efficiency of the biomass were characterized.
Kinetics and microbial community structure
turned out to be duly correlated. The impact of the separation
technology on selective conditions and, in particular,
the higher variability of solid separation efficiency in CAS
with respect to MBR pilot plant possibly represented the
main factor influencing the selection of bacterial communities.
Concerning nitrifiers, bacteria of the genus Nitrospira
were predominant in the MBR. This was in accordance with
kinetics of nitrite-oxidizing bacteria that suggested the
presence of k-strategists, while r-strategists were selected in
the CAS plant, possibly because of the presence of transient
higher concentrations of nitrite (in the range of 0.05–0.18
and of 0.05–4.4 mg NO
2 -N L-1 in the MBR and CAS
effluents, respectively). An unexpectedly high presence of bacteria belonging to two specific phylogenetic clades of
Planctomycetes was found in both reactors.
these environments. Here we performed a monthly survey on the bacterial community of a consortial industrial plant. Objectives of this study were: (1) to identify a core microbiota constant over time; (2) to evaluate the temporal dynamics of the community during one year. A conspicuous and diversified core microbiota is constituted by operational taxonomic units which are present throughout the year in the plant. Community composition data confirm that the presence and abundance of bacteria in WWTPs is highly consistent at high taxonomic level. Our results indicate however a difference in microbial community structure between two groups of samples, identifying the summer holiday period as the break-point. Changes in the structure of the microbial community occur otherwise gradually, one month after another. Further studies will clarify how the size and diversity of the core microbiota could affect the observed dynamics.
COD/SO4
2- ratio (SO4
2- = 1810 mg L-1, CODtotal = 2530 mg L-1) for the investigation of sulphate and COD removal as a function
of substrates limitation and ammonia and sulphide inhibition. Sulphate-reducing bacteria (SRB) out-competed methanogenic
bacteria due to the low influent COD/SO4
2- ratio, the high concentration of sulphide and the presence of inhibiting compounds in
tannery wastewater. An average sulphate removal of 53% and an average COD removal of 42% were obtained. Ammonia and
sulphide concentrations were found to play a major role in the process, and their effect was quantified. A simplified mathematical
model was calibrated under semi-steady conditions and no substrate limitation, and used to describe sulphide and ammonia
inhibition. Half-inhibition constants for ammonia (KNH4) and sulphide (KHS) of 180 mg L-1 and 480 mg L-1, respectively, were
obtained. No improvements of the biodegradability between the untreated tannery wastewater and the UAF effluent were
observed through respirometric tests.
a conventional activated sludge system (CAS) were in
parallel operated to investigate the impact of the separation
technology on the structure and functionality of the selected
microbial community. Microbial communities as well
as nitrogen removal efficiency of the biomass were characterized.
Kinetics and microbial community structure
turned out to be duly correlated. The impact of the separation
technology on selective conditions and, in particular,
the higher variability of solid separation efficiency in CAS
with respect to MBR pilot plant possibly represented the
main factor influencing the selection of bacterial communities.
Concerning nitrifiers, bacteria of the genus Nitrospira
were predominant in the MBR. This was in accordance with
kinetics of nitrite-oxidizing bacteria that suggested the
presence of k-strategists, while r-strategists were selected in
the CAS plant, possibly because of the presence of transient
higher concentrations of nitrite (in the range of 0.05–0.18
and of 0.05–4.4 mg NO
2 -N L-1 in the MBR and CAS
effluents, respectively). An unexpectedly high presence of bacteria belonging to two specific phylogenetic clades of
Planctomycetes was found in both reactors.
these environments. Here we performed a monthly survey on the bacterial community of a consortial industrial plant. Objectives of this study were: (1) to identify a core microbiota constant over time; (2) to evaluate the temporal dynamics of the community during one year. A conspicuous and diversified core microbiota is constituted by operational taxonomic units which are present throughout the year in the plant. Community composition data confirm that the presence and abundance of bacteria in WWTPs is highly consistent at high taxonomic level. Our results indicate however a difference in microbial community structure between two groups of samples, identifying the summer holiday period as the break-point. Changes in the structure of the microbial community occur otherwise gradually, one month after another. Further studies will clarify how the size and diversity of the core microbiota could affect the observed dynamics.