Lesson - Nitrification

Nitrification is an important and effective microbial process in the oxidation of ammonia in land and water environments. Two groups of organisms are involved in the nitrification process:

1. Ammonia-oxidizing bacteria, Nitrobacter
2. Nitrite-oxidizing bacteria, Nitrosoma

When nitrification occurs in chloraminated drinking water, the process may lower the water quality unless the nitrification process reaches completion. Incomplete or partial nitrification causes the production of nitrite from the growth of Nitrobacter bacteria. This nitrite, in turn, rapidly reduces free chlorine and can interfere with the measurement of free chlorine. The end result may be a loss of total chlorine and ammonia and an increase in the concentration of heterotrophic plate count bacteria. 

Factors influencing nitrification include the water temperature, the detention time in the reservoir or distribution system, excess ammonia in the water system, and the chloramine concentration used. Conditions that are most likely to lead to nitrification when using chloramines are a pH of 7.5 to 8.5, a water temperature of 77 to 86F, a free ammonia concentration in the water, and a dark environment. The danger in allowing nitrification 
episodes to occur is that the operator may be left with very low or no total chlorine residual. Total chlorine residual is the total concentration of chlorine in water, including the combined chlorine and the free available chlorine.

Drinking water regulations are constantly changing. The Interim Enhanced Surface Water Rule and the Disinfectant/Disinfection By-products Rule were passed in 1998 and further modifications of these rules have been developed. The goal of these rules was to increase the public protection from illness caused by Cryptosporidum, to limit the amount of certain potentially harmful disinfection by-products that may remain in drinking water after treatment.

Nitrification in the Distribution System

American Water Works a short excerpt of the problem of Nitrification. Please take noted what are the problems with it.

The information for this page s from book titled "Water Mathematics" Created by Mike Alvord, Regina Blasberg and Stephanie Anagnoson, Version 3.2 dated 2020.© 2018, California Community Colleges, Chancellor’s Office.
This work is licensed under a Creative Commons Attribution 4.0 International Licens