Transcript What is Nitrification?

Nitrification
Nitrobacter
Nitrosomonas
Note: There are other bacteria capable of
nitrification. These are the only ones that
can be viewed at 1000x phase contrast
Frequently Asked Questions
What are the Forms of Nitrogen?
• Total Nitrogen= organic N + inorganic N
• TKN (Total Kjeldahl Nitrogen)= ammonia
and organic nitrogen (particulate and
soluble)
• Organic Nitrogen- Proteins, peptides,
nucleic acids, urea, other synthetic
organic compounds
• Nitrate, Nitrite, Nitrogen Gas
• Ammonia N- NH3/ NH4
• TIN (Total Inorganic Nitrogen)= nitrate +
nitrite + ammonia
What is Nitrification?
• Nitrification is an aerobic process that involves the
conversion of ammonia to nitrite and then nitrate
through nitrifying bacteria
• Nitrosomonas, as well as other nitrifying bacteria
convert ammonia to nitrite
• Nitrobacter, as well as other nitrifying bacteria
convert nitrite to nitrate
• The bacteria in wastewater treatment will remove
some nitrogen as a nutrient, and the remaining
nitrogen may need to undergo this process if there
is an ammonia limit for the plant
What’s the difference between
ammonium and ammonia?
• For scientific purposes, ammonia and ammonia are
often grouped together and referred to as
ammonia
• Ammonium (NH4+) is the ionized form of ammonia
which is oxidized by nitrifying bacteria
• The relationship between ammonium and
ammonia (NH3) depends on pH and to a lesser
extend, the temperature.
• Un-ionized ammonia (NH3) is the toxic form and
will predominate at higher pH.
• In general, less than 10% of ammonia is in the toxic
form at pH <8
• Ammonium is relatively non-toxic and
predominates at lower pH values
• At any pH, more toxic ammonia is present in
warmer water than in cooler water
What are the needed operating
parameters for nitrification?
• Dissolved Oxygen: Generally 2 mg/L or more is
recommended to ensure aerobic conditions.
• 4.57 lbs of dissolved oxygen are consumed for every lb
of ammonium converted to nitrate
• pH: 7-8.5
• Temperature: Nitrifying bacteria prefer
temperatures between 15-30 degrees C
• nitrification rates will decrease at cooler temperatures
• Alkalinity: Alkalinity is the food source for nitrifying
bacteria.
• For every part ammonium converted to nitrate, 7.14
parts alkalinity are consumed.
• Generally, it is good practice to maintain 60 mg/L or
more alkalinity residual in the mixed liquor
• Sludge Age: Due to slow growth rates of nitrifying
bacteria, generally a 5 day sludge age or more is
recommended for nitrification
What compounds can inhibit
nitrification?
• Heavy Metals
• Phenol
• Cyanide
• Amines
• Surfactants
• Sulfide
• Certain organic acids
• Chlorinated hydrocarbons
• Peracedic acid
• Quaternary ammonium
• Flourides
What should I do if the ammonia
suddenly spikes in my effluent?
• A microscopic evaluation is recommended to look
for any signs of inhibition or stress to the other
bacteria
• It is generally accepted practice to increase the
sludge age (decrease the wasting rate) to allow
more time for nitrifying bacteria to grow
• Ensure that the proper conditions for nitrification
are present (see previous slide)
• If, and only if the proper conditions are in place and
there are no inhibitory compounds present, reseeding
the plant with nitrifying bacteria via bio augmentation
is a common practice
• A nitrogen balance of the plant can be estimated to
determine if the increase of ammonia in the
effluent is simply due to more ammonia in the
influent
• Always document operational decisions, especially
in the event of a potential non-compliance
situation.
• Your operational log book could serve as a legal
document