Influence of medium composition on the characteristics of a denitrifying biofilm formed by Alcaligenes denitrificans in a fluidised bed reactor

Abstract

The influence of the ratio carbon/nitrogen and phosphorus concentration on the performance of a biofilm fluidised bed reactor used for denitrification and on the properties of the biofilm was studied. Although the removal efficiencies of C and N reached steady-state values, the thickness of the biofilm steadily increased. The dry density of the biofilm did not seem to be dependent on the loading conditions, although a denser biofilm was obtained when there was no nutrient limitation that corresponded to the complete removal of nitrate and carbon. The composition of the biofilm in terms of proteins and polysaccharides changed with the C/N ratio and P concentrations. Higher denitrifying activities, which were obtained with increasing P concentrations, were related with higher protein content, since metabolism was shifted from polysaccharide production towards cell production. The thickness and the density of the biofilms were related mainly with the shear stress in the reactor and the composition of biofilms was dependent on the composition of the medium and related with higher activities of the microorganisms.

Denitrification of a landfill leachate with high nitrate concentration in an anoxic rotating biological contactor

“…Considering that influent phosphorus concentration can significantly affect the denitrifying process (Alves et al 2002;Teixeira and Oliveira 2000), in an attempt to make the microbial community consume the leachate organic matter, P-PO 4 3-influent concentration was changed to 10 mg l -1 , from day 20 onwards. Phosphorus concentration was selected according to Welander et al (1998).…”

Characterization of sulfate-reducing bacteria dominated surface communities during start-up of a down-flow fluidized bed reactor

“…The results (Table 3) showed a remarkable steady ratio around 2, irrespective of the amount of biomass, indicating that there was not a concomitant increase due to the nutritional regime (ethanol vs. acetate). This ratio has been shown to increase in denitrifying biofilms, as a function of phosphorous enrichment [4], suggesting that limitation of nutrients may stimulate polysaccharide biosynthesis as adaptive strategy within the community.…”

“…This medium was supplemented in the beginning with a mixture of lactate-ethanol to enrich the SRB population; afterward ethanol was the only substrate. According to the desired chemical oxygen demand (COD), sulfate (SO 4 2-) was also supplemented as Na 2 SO 4 to maintain a COD/SO 4 2-ratio of 0.6 (g/g) during reactor operation as shown in Table 1. The pH of the medium was adjusted to 6.5 with sodium bicarbonate.…”

“…The sulfate-reducing specific activity was determined in 70 mL serum bottles using ethanol, lactate or acetate as individual substrates at 1 g COD/L, 1.5 g SO 4 2-/L was added to the basal mineral medium to obtain a COD/SO 4 2-ratio of 0.6 (g/g), the pH was adjusted to 6.5 with sodium bicarbonate. The bottles contained 5 mL of carrier material recently withdrawn from the reactor and 65 mL of basal mineral medium (no headspace) supplemented with sulfate and 1 g COD/L as lactate or acetate.…”

The New Methods for Purifying the Industrial Effluents by Submerged Biofilm Reactors

“…The influence of the ratio carbon-nitrogen and phosphorus concentration on the performance of a biofilm fluidized bed reactor has already bee used for denitrification [2]. The thickness and the density of the biofilms were related mainly with the shear stress in the reactor and the composition of biofilms was dependent on the composition of the medium and related with higher activities of the microorganisms.…”