1. Nitrification Frequently Asked Questions NitrobacterNitrosomonas Note: There are other bacteria capable of nitrification. These are the only ones that can be viewed at 1000x phase contrast

2. 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

3. 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

4. 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

5. 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

6. What compounds can inhibit nitrification? Heavy Metals Phenol Cyanide Amines Surfactants Sulfide Certain organic acids Chlorinated hydrocarbons Peracedic acid Quaternary ammonium Flourides

7. 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