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Methods to extract the exopolymeric matrix from biofilms : a comparative study

To study the composition of a biofilm a previous extraction method is required to separate cells from the matrix. There are several methods reported in the literature; however they are not efficient or promote leakage of intracellular material. In this work several extraction methods were assayed in mixed culture and pure culture biofilms and their efficiency was evaluated by the amount of organic carbon, prote...

A new method for extraction of exopolymers from activated sludges

The exopolymeric matrix that surrounds the biomass greatly contributes to the efficiency of activated sludge systems. To study the composition of this matrix a preliminary extraction method is required. In this work three extraction methods (vapor, sonication and combined treatment by sonication and Dowex resin) were used and compared with a new method which uses glutaraldehyde. The extraction effectiveness was...

A new method for extraction of exopolymers from activated sludges

The exopolymeric matrix that surrounds the biomass greatly contributes to the efficiency of activated sludge systems. To study the composition of this matrix a preliminary extraction method is required. In this work three extraction methods (vapour, sonication and combined treatment by sonication and Dowex resin) were used and compared with a new method which uses glutaraldehyde. The extraction's effectiveness ...

Nitrification in a circulating bed reactor : pH and dissolved oxygen effects

Influence of dissolved oxygen on nitrification kinetics in a circulating bed re...

The influence of dissolved oxygen concentration in nitrification kinetics was studied in a new biofilm reactor, the circulating bed reactor (CBR). The study was carried out partly at laboratory scale with synthetic water containing inorganic carbon and nitrogen compounds, and partly at pilot scale for secondary and tertiary nitrification of municipal wastewater. The experimental results showed that either the a...

Influence of dissolved oxygen on the nitrification kinetics in a circulating be...

The influence of dissolved oxygen concentration on the nitrification kinetics was studied in the circulating bed reactor (CBR). The study was partly performed at laboratory scale with synthetic water, and partly at pilot scale with secondary effluent as feed water. The nitrifi- cation kinetics of the laboratory CBR as a function of the oxygen concentration can be described according to the half order and zero o...

Activity control in nitrifying biofilms : application of respirometric tests

Nitrification is the biological oxidation of ammonia to nitrate via nitrite. These reactions are performed by aerobic autotrophic microorganisms, commonly known as nitrifiers. The nitrifiers are generally constituted of ammonia oxidizing bacteria and nitrite oxidizing bacteria. They are very sensitive to environmental factors, namely the pH, which has its optimum value in the range of 7.5 to 8.5 (Sharma end Ahl...

Methods to extract the exopolymeric matrix from biofilms: a comparative study

To study biofilm composition a previous extraction method is required to separate cells from the matrix. There are several methods reported in the literature, however they are not efficient or promote leakage of intracellular material. In this work several extraction methods were assayed in mixed culture and pure culture biofilms and their efficiency was evaluated by the amount of organic carbon, proteins and i...

Influence of dissolved oxygen in nitrification kinetics in a circulating bed re...

The influence of dissolved oxygen concentration in nitrification kinetics was studied in a new biofilm reactor, the circulating bed reactor (CBR). The study was carried out partly at laboratory scale with synthetic water containing inorganic carbon and nitrogen compounds, and partly at pilot scale for secondary and tertiary nitrification of municipal wastewater. The experimental results showed that, either the ...

Control of nitrification efficiency in a new biofilm reactor

The study of the nitrification capacity of a new gas-lift circulating bed reactor (CBR) carried out with laboratory and industrial scale prototypes, showed a high nitrification rate (1.2-2 kgN mˉ³ dˉ¹) without any nitrite accumulation. A good nitrification performance 0.5-0.6 kgN mˉ³dˉ¹ was maintained even when the CODs/N-NH4 ratio was increased up to 1.8-3.4 (laboratory CBR) and 4-10 (industrial prototype). Th...