ABSTRACT
A mixed population of bacteria from bottom sludge of nitrogen wastewater reservoir was incubated in continuous culture in medium containing 1000 mg nitrate nitrogen/l and starch. Maximal efficiency of denitrification was 5 mg N/l/h. Marked changes in participation of denitrifying bacteria (16-76%) among total number of bacteria was observed, this being dependent on the ratio of starch concentration (CS) to nitrogen concentration (CN) in the medium. The optimal CS/CN ratio ensuring highest participation of denitrifying bacteria was 3.2. The amount of starch required for the denitrification of a defined quantity of nitrogen is negatively correlated (r = -0.98) with the frequency of the occurrence of denitrifying bacteria (XD) and is: CS = (5.53-0.028XD) CN. The denitrifying bacteria in continuous culture were dominated, depending on CS/CN ratio and flow rate of medium, by Alcaligenes faecalis, Paracoccus denitrificans or Pseudomonas mendocina, that is species unable to hydrolyse starch.
Subject(s)
Bacteria/metabolism , Nitrogen/metabolism , Starch/pharmacology , Carbon/metabolism , Culture Media , Nitrates/metabolismABSTRACT
A mixed population of bacteria from industrial nitrogen wastewaters was incubated in continuous culture in medium containing 1000-1300 mg nitrate nitrogen per litre and maltose as a source of organic carbon. Maximal efficiency of denitrification was 8.6 mg N/1/h. The participation of denitrifying bacteria in the culture varied from 0% to about 80%, depending on the ratio of maltose concentration (CM) to nitrogen concentration (CN) in the medium. The optimal CM/CN ratio ensuring the greatest selection of denitrifying bacteria was 5.0, which calculated per organic carbon (CC/CN) gave the value of 2.1. The amount of maltose needed to denitrify a defined amount of nitrogens was negatively correlated (rxy = -0.95) with the frequency of denitrifying bacteria (XD) in the culture and was: CM = (4.20-0.026XD)CN. The denitrifying bacteria isolated from the studied continuous culture were dominated by Alcaligenes faecalis and Pseudomonas mendocina.
Subject(s)
Alcaligenes/metabolism , Maltose/metabolism , Nitrates/metabolism , Pseudomonas/metabolism , Water Microbiology , Water Pollution , Alcaligenes/isolation & purification , Culture Media , Industrial Waste , Pseudomonas/isolation & purification , Water Pollutants, ChemicalABSTRACT
The effect of methanol, ethanol, acetic acid and glucose together with NaNO2 or KNO3 (1,000 mg N/l) on the intensity of denitrification and selection of denitrifying bacteria from the bottom sludge of nitrogenous wastewater reservoir was examined. Denitrification was found to be the most efficient in medium with ethanol or acetic acid. The presence of glucose facilitated the selection of Alcaligenes faecalis whereas the other carbon sources enabled the selection of bacteria of the genus Pseudomonas: methanol -- P. fluorescens, ethanol -- P. mendocina. In medium with acetic acid species selection depends on the form of nitrogen: NaNO2 -- P. fluorescens, KNO3 -- P. aeruginosa.