Nitrification Frequently Asked Questions NitrobacterNitrosomonas Note: There are other bacteria capable of nitrification. These are the only ones that.

Nitrification

Frequently Asked Questions

Nitrobacter Nitrosomonas

Note: There are other bacteria capable of nitrification. These are the only ones that can be viewed at 1000x phase contrast

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