Saint-Laurent, Canada
Saint-Laurent, Canada

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Ramdani A.,Ecole Polytechnique de Montréal | Dold P.,EnviroSim Associates Ltd | Gadbois A.,John Meunier Inc. | Deleris S.,Pirelli SpA | And 2 more authors.
Water Research | Year: 2012

The activated sludge process generates an endogenous residue (X E) as a result of heterotrophic biomass decay (X H). A literature review yielded limited information on the differences between X E and X H in terms of chemical composition and content of extracellular polymeric substances (EPS). The objective of this project was to characterize the chemical composition (x, y, z, a, b and c in C xH yO zN aP bS c) of the endogenous and the active fractions and EPS of activated sludge from well designed experiments. To isolate X H and X E in this study, activated sludge was generated in a 200L pilot-scale aerobic membrane bioreactor (MBR) fed with a soluble and completely biodegradable synthetic influent of sodium acetate as the sole carbon source. This influent, which contained no influent unbiodegradable organic or inorganic particulate matter, allowed the generation of a sludge composed essentially of two fractions: heterotrophic biomass X H and an endogenous residue X E, the nitrifying biomass being negligible. The endogenous decay rate and the active biomass fraction of the MBR sludge were determined in 21-day aerobic digestion batch tests by monitoring the VSS and OUR responses. Fractions of X H and X E were respectively 68% and 32% in run 1 (MBR at 5.2 day SRT) and 59% and 41% in run 2 (MBR at 10.4 day SRT). The endogenous residue was isolated by subjecting the MBR sludge to prolonged aerobic batch digestion for 3 weeks, and was characterized in terms of (a) elemental analysis for carbon, nitrogen, phosphorus and sulphur; and (b) content of EPS. The MBR sludge was characterized using the same procedures (a and b). Knowing the proportions of X H and X E in this sludge, it was possible to characterize X H by back calculation. Results from this investigation showed that the endogenous residue had a chemical composition different from that of the active biomass with a lower content of inorganic matter (1:4.2), of nitrogen (1:2.9), of phosphorus (1:5.3) and of sulphur (1:3.2) but a similar content of carbon (1:0.98). Based on these elemental analyses, chemical composition formulae for X H and X E were determined as CH 1.240O 0.375N 0.200P 0.0172S 0.0070 and CH 1.248O 0.492N 0.068P 0.0032S 0.0016, respectively. Data from EPS analyses also confirmed this difference in structure between X E and X H with an EPS content of 11-17% in X E versus 26-40% in X H. © 2011 Elsevier Ltd.


Ramdani A.,Ecole Polytechnique de Montréal | Dold P.,EnviroSim Associates Ltd. | Deleris S.,Veolia | Lamarre D.,John Meunier Inc. | And 2 more authors.
Water Research | Year: 2010

This study evaluated the potential biodegradability of the endogenous residue in activated sludge subjected to batch digestion under either non-aerated or alternating aerated and non-aerated conditions. Mixed liquor for the tests was generated in a 200 L pilot-scale aerobic membrane bioreactor (MBR) operated at a 5.2 days SRT. The MBR system was fed a soluble and completely biodegradable synthetic influent composed of sodium acetate as the sole carbon source. This influent, which contained no influent unbiodegradable organic or inorganic materials, allowed to generate sludge composed of essentially two fractions: a heterotrophic biomass XH and an endogenous residue XE, the nitrifying biomass being negligible (less than 2%). The endogenous decay rate and the active biomass fraction of the MBR sludge were determined in 21-day aerobic digestion batch tests by monitoring the VSS and OUR responses. Fractions of XH and XE: 68% and 32% were obtained, respectively, at a 5.2 days SRT. To assess the biodegradability of XE, two batch digestion units operated at 35 °C were run for 90 days using thickened sludge from the MBR system. In the first unit, anaerobic conditions were maintained while in the second unit, alternating aerated and non-aerated conditions were applied. Data for both units showed apparent partial biodegradation of the endogenous residue. Modeling the batch tests indicated endogenous residue decay rates of 0.005 d-1 and 0.012 d-1 for the anaerobic unit and the alternating aerated and non-aerated conditions, respectively. © 2009 Elsevier Ltd. All rights reserved.


Ramdani A.,Ecole Polytechnique de Montréal | Dold P.,EnviroSim Associates Ltd. | Gadbois A.,John Meunier Inc. | Deleris S.,Pirelli SpA | And 2 more authors.
Water Research | Year: 2012

The goal of this study was to determine the effect of a long sludge retention time on the biodegradation of the endogenous residue in membrane digestion units receiving a daily feed of sludge and operated under either aerobic or intermittently aerated (22 h off-2 h on) conditions. The mixed liquor for these experiments was generated in a 10.4 day sludge retention time membrane bioreactor fed with a synthetic and completely biodegradable influent with acetate as the sole carbon source. It had uniform characteristics and consisted of only two components, heterotrophic biomass X H and endogenous residue X E. Membrane digestion unit experiments were conducted for 80 days without any sludge wastage except for some sampling. The dynamic behaviour of generation and consumption of filtered organic digestion products was characterized in the membrane digestion unit systems using three pore filter sizes. Results from this investigation indicated that the colloidal matter with size between 0.04 μm and 0.45 μm was shown to contain a recalcitrant fraction possibly composed of polysaccharides bound to proteins which accumulated in the membrane digestion unit under both conditions. Modelling the membrane digestion unit results by considering a first-order decay of the endogenous residue allowed to determine values of the endogenous residue decay rate of 0.0065 and 0.0072 d -1 under fully aerobic and intermittently aerated conditions, respectively. The effect of temperature on the endogenous decay rate was assessed for the intermittently aerated conditions in batch tests using thickened sludge from tests gave an endogenous decay rate constant of 0.0075 d -1 at 20 °C and an Arrhenius temperature correction factor of 1.033. © 2012 Elsevier Ltd.


Sperandio M.,Toulouse 1 University Capitole | Labelle M.-A.,Ecole Polytechnique de Montréal | Ramdani A.,Ecole Polytechnique de Montréal | Gadbois A.,John Meunier Inc | And 3 more authors.
Water Science and Technology | Year: 2013

Activated sludge models have assumed that a portion of organic solids in municipal wastewater influent is unbiodegradable. Also, it is assumed that solids from biomass decay cannot be degraded further. The paper evaluates these assumptions based on data from systems operating at higher than typical sludge retention times (SRTs), including membrane bioreactor systems with total solids retention (no intentional sludge wastage). Data from over 30 references and with SRTs of up to 400 d were analysed. A modified model that considers the possible degradation of the two components is proposed. First order degradation rates of approximately 0.007 d-1 for both components appear to improve sludge production estimates. Factors possibly influencing these degradation rates such as wastewater characteristics and bioavailability are discussed. © IWA Publishing 2013.


Mansour-Geoffrion M.,Ecole Polytechnique de Montréal | Dold P.L.,EnviroSim Associates | Lamarre D.,John Meunier Inc. | Gadbois A.,John Meunier Inc. | And 2 more authors.
Minerals Engineering | Year: 2010

Typically, 15-45% of the mixed liquor (sludge) in biological wastewater treatment plants (WWTPs) consists of inorganic (fixed) suspended solids. A portion of these inorganic compounds is grit (sand) originating from the influent. Grit accumulation impacts WWTP design and operating costs as these unbiodegradable solids reduce the effective treatment capacity of the bioreactor and other unit operations that must be sized to carry this material. The goal of this study was to characterize the performance of a hydrocyclone to selectively separate grit from activated sludge. Laboratory experiments were conducted with a 13 mm diameter Krebs hydrocyclone treating sludge from eight WWTPs. Reduced efficiencies of 17 ± 7% on fixed suspended solids and 9 ± 6% on volatile suspended solids were obtained. Grade efficiency curves enabled the development of a modified definition for cut size useful for this application. The characterization of hydrocyclone performance for grit removal from activated sludge will enable modelling of the process for integration into wastewater treatment simulators used for process performance prediction and design. © 2009 Elsevier Ltd. All rights reserved.


Labelle M.-A.,Ecole Polytechnique de Montréal | Ramdani A.,Ecole Polytechnique de Montréal | Deleris S.,Veolia | Gadbois A.,John Meunier Inc. | And 2 more authors.
Water Science and Technology | Year: 2011

Coupling the activated sludge and the ozonation processes is an efficient, although expensive, solution for sludge reduction. A better knowledge of the mechanisms involved in the degradation of various sludge fractions by ozone is needed to optimize the coupled process. The objectives of this study were to determine the biodegradability of ozone-solubilized endogenous residue, the action of ozone on the active biomass and the solubilization yield of these two main sludge fractions. Batch tests were conducted with slug input of ozone stock solution into fresh or aerobically digested synthetic sludge. Biodegradability of the solubilized endogenous residue was increased by ozonation by up to 0.27 g BOD 5/g COD i. Ozone caused biomass lysis, as opposed to an increase in maintenance needs, as shown by a correlation between the decrease in microbial activity and viability. Lysis caused by ozonation was associated with a solubilization of 20% of the lyzed cell COD mass. Solubilization yields were of 9.6 and of 1.9 to 3.6 g COD/g O 3 for fresh and aerobically digested sludge, respectively. Design of sludge ozonation processes should account for the variability between the solubilization yield and biodegradability of the various sludge fractions. © IWA Publishing 2011.


Hoang V.,University of Ottawa | Delatolla R.,University of Ottawa | Laflamme E.,John Meunier Inc. | Gadbois A.,John Meunier Inc.
Water Environment Research | Year: 2014

Biological treatment is the most common and economical means of ammonia removal in wastewater; however, nitrification rates can become completely impeded at cold temperatures. Attached growth processes and, specifically, moving bed biofilm reactors (MBBRs) have shown promise with respect to low-temperature nitrification. In this study, two laboratory MBBRs were used to investigate MBBR nitrification rates at 20, 5, and 1°C. Furthermore, the solids detached by the MBBR reactors were investigated and Arrhenius temperature correction models used to predict nitrification rates after long-term low-temperature exposure was evaluated. The nitrification rate at 5°C was 66 ± 3.9% and 64 ± 3.7% compared to the rate measured at 20°C for reactors 1 and 2, respectively. The nitrification rates at 1°C over a 4-month exposure period compared to the rate at 20°C were 18.7 ± 5.5% and 15.7 ± 4.7% for the two reactors. The quantity of solids detached from the MBBR biocarriers was low and the mass of biofilm per carrier did not vary significantly at 20°C compared to that after long-term exposure at 1°C. Lastly, a temperature correction model based on exposure time to cold temperatures showed a strong correlation to the calculated ammonia removal rates relative to 20°C following a gradual acclimatization period to cold temperatures.


Hoang V.,University of Ottawa | Delatolla R.,University of Ottawa | Abujamel T.,University of Ottawa | Mottawea W.,University of Ottawa | And 3 more authors.
Water Research | Year: 2014

This study aims to investigate moving bed biofilm reactor (MBBR) nitrification rates, nitrifying biofilm morphology, biomass viability as well as bacterial community shifts during long-term exposure to 1°C. Long-term exposure to 1°C is the key operational condition for potential ammonia removal upgrade units to numerous northern region treatment systems. The average laboratory MBBR ammonia removal rate after long-term exposure to 1°C was measured to be 18±5.1% as compared to the average removal rate at 20°C. Biofilm morphology and specifically the thickness along with biomass viability at various depths in the biofilm were investigated using variable pressure electron scanning microscope (VPSEM) imaging and confocal laser scanning microscope (CLSM) imaging in combination with viability live/dead staining. The biofilm thickness along with the number of viable cells showed significant increases after long-term exposure to 1°C. Hence, this study observed nitrifying bacteria with higher activities at warm temperatures and a slightly greater quantity of nitrifying bacteria with lower activities at cold temperatures in nitrifying MBBR biofilms. Using DNA sequencing analysis, Nitrosomonas and Nitrosospira (ammonia oxidizers) as well as Nitrospira (nitrite oxidizer) were identified and no population shift was observed between 20°C and after long-term exposure to 1°C. © 2013 Elsevier Ltd.


PubMed | University of Ottawa and John Meunier Inc.
Type: | Journal: Water research | Year: 2014

This study aims to investigate moving bed biofilm reactor (MBBR) nitrification rates, nitrifying biofilm morphology, biomass viability as well as bacterial community shifts during long-term exposure to 1C. Long-term exposure to 1C is the key operational condition for potential ammonia removal upgrade units to numerous northern region treatment systems. The average laboratory MBBR ammonia removal rate after long-term exposure to 1C was measured to be 185.1% as compared to the average removal rate at 20C. Biofilm morphology and specifically the thickness along with biomass viability at various depths in the biofilm were investigated using variable pressure electron scanning microscope (VPSEM) imaging and confocal laser scanning microscope (CLSM) imaging in combination with viability live/dead staining. The biofilm thickness along with the number of viable cells showed significant increases after long-term exposure to 1C. Hence, this study observed nitrifying bacteria with higher activities at warm temperatures and a slightly greater quantity of nitrifying bacteria with lower activities at cold temperatures in nitrifying MBBR biofilms. Using DNA sequencing analysis, Nitrosomonas and Nitrosospira (ammonia oxidizers) as well as Nitrospira (nitrite oxidizer) were identified and no population shift was observed between 20C and after long-term exposure to 1C.

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