Denitrifying Bacteria

Facultative anaerobic bacteria or denitrifying bacteria are capable of using either free molecular oxygen, nitrate, or nitrite to degrade soluble cBOD in order to obtain carbon and energy for cellular growth and activity. Although denitrifying bacteria

TABLE 11.1 Industrial Wastewaters that Contain Nitrate or Nitrite

Industrial Wastewater Nitrate (NO3-) Nitrite (NO2-)

Corrosion inhibitor X

Leachate (pretreated) X X

Meat (flavoring) X

Meat (preservative) X

Meat (pretreated) X X

Steel X X

Floc particle diameter _ > 100 um

Floc particle diameter _ > 100 um

Dissolved oxygen concentration at the core of the floc particle = 0

FIGURE 11.1 Dissolved oxygen gradient.

Dissolved oxygen concentration at the core of the floc particle = 0

FIGURE 11.1 Dissolved oxygen gradient.

are capable of using free molecular oxygen, nitrate, and nitrite, the bacteria can only use one molecule at a time. They use the molecule that is available and provides the most carbon and energy for cellular growth and activity. Their preference always is for free molecular oxygen. When compared to the use of nitrate for the degradation of soluble cBOD, free molecular oxygen provides for more cellular growth (Equations 11.2 and 11.3) and more cellular energy (Equations 11.4 and 11.5).

1 pound of glucose + O2 denit rifying bacteria > 0.6 pound of cells (sludge) (11.2)

1 pound of glucose + NO3- denit rifying bacteria > 0.4 pound of cells (sludge) (11.3)

1 mole of glucose + O2 denit rifying bacteria > 686 kcal of energy (11.4)

1 mole of glucose + NO3- denit rifying bacteria > 636 kcal of energy (11.5)

Denitrifying bacteria enter activated sludge processes in fecal waste and through infiltration and inflow (I/I) as soil and water organisms. They are easily incorporated

TABLE 11.2 Genera of Activated Sludge Bacteria that Contain Denitrifying Species

Achromobacter

Acinetobacter

Agrobacterium

Alcaligens

Bacillus

Chromobacterium Corynebacterium Denitrobacillus Enterobacter

Escherichia

Flavobacterium

Glucononobacer

Holobacterium

Hyphomicrobium

Kingella

Methanonas

Moraxella

Neisseria

Paracoccus

Propionibacterium

Pseudomonas

Rhizobium

Rhodopseudomonas

Spirillum

Thiobacillus

Xanthomonas into floc particles. Some denitrifying bacteria are floc formers, while most denitrifying bacteria are incorporated into floc particles through compatible surface charge or the coating action of secretions from ciliated protozoa, rotifers, and free-living nematodes.

Denitrifying bacteria are present in billions per gram of floc particle and represent approximately 80% of all bacteria flocculated and dispersed in the activated sludge process. There are numerous genera of bacteria that contain species of denitrifying bacteria (Table 11.2). The genera that contain the most species of denitrifying bacteria include Alcaligens, Bacillus, and Pseudomonas.

Denitrifying bacteria reproduce quickly. The generation time for most is approximately 15-30 minutes. The enzymes necessary for the use of nitrate or nitrite are formed quickly under an anoxic condition or low dissolved oxygen condition.

Was this article helpful?

0 0
Losing Weight Without Starving

Losing Weight Without Starving

Tired of Trying To Loose Weight And It Never Works or You Have To Starve Yourself Well Here's A Weight Loss Plan That takes Care of Your Weight Problem And You Can Still Eat. In This Book, You’ll Learn How To Lose Weight And Not Feel Hungry! In An Easy Step-By-Step Process That Enables You To Feel Good About Loosing Weight As Well As Feeling Good Because Your Stomach Is Still Full.

Get My Free Ebook


Post a comment