Aerial view of the Warren, Maine lagoon system. Photo courtesy of Woodard and Curran.

Lagoon Systems In Maine 

Systems In Maine

An Informational Resource for
Operators of Lagoon Systems

Mars Hill Wastewater Lagoon System - Mars Hill  Maine. Photo Courtesy of Wright-Pierce Engineers.
 Mission  |  Search  |  Acknowledgements  | Discussion Group |  Contact Us  | Links

Design & Operation
Lagoon Aeration
Tech Papers
Operation Articles
Lagoons In Maine
The Laboratory
Maine Lagoon News
Lagoon Biology

2003 Maine Wastewater Salary Survey as conducted by the Maine Wastewater Control Association

2003 Maine Wastewater Rate Survey conducted by the Maine Rural Water Association

Maine DEP Monthly
O & M Newsletter

Maine and WEF's
Operation Forum

Penobscot Watershed and Development of a TMDL 

EPA Binational Toxics

Maine Rural Water

Maine Wastewater
Operator Certification

Maine Is Technology

Maine Wastewater Control Association

Maine WasteWater Control Association

Wastewater Engineering


Nitrogen in Wastewater

If It’s Not Ammonia, Then What Form Of Nitrogen Is It?

(The secret life of the other three nitrogen players in wastewater.)

Tim Loftus

The last article covered nitrogen in wastewater and in the environment, focusing specifically on ammonia-nitrogen, its collection, preservation, and analysis. This article will review some of the important aspects of the other forms of nitrogen in wastewater – organic nitrogen, nitrate-nitrogen, and nitrite-nitrogen.

Organic nitrogen is somewhat of a misnomer. The term “organic nitrogen” in wastewater does not represent all the nitrogen found in organic matter; it is only a portion of it, mostly consisting of protein, urea, and certain components of cells (like nucleic acids). So when you review organic nitrogen results, you are looking at the results of a test-defined method. Only when analysts all follow the same methods for organic nitrogen analyses can the results be compared.

Fortunately chemists have developed a standardized test to do just that. It is called Total Kjeldahl Nitrogen (TKN) analysis, where the result is the total of the organic nitrogen plus any ammonia-nitrogen in a sample. For TKN, a sample is digested using a particular cocktail of chemicals to convert the organic nitrogen portion of the sample into ammonia. The sample is further distilled and the ammonia concentration is determined using one of the accepted EPA procedures. From a replicate sample, the ammonia-only concentration is determined. The difference between the TKN value (organic and ammonia combined) and the ammonia value will be the organic nitrogen.

Samples for TKN can be collected in either glass or plastic bottles. After a pH adjustment to less than 2 using sulfuric acid and cooled to 4 degrees C, a sample will have a holding time of up to twenty-eight days before analysis.

Typically, less than one percent of the nitrogen in raw wastewater is in the form of nitrates (NO3 -) or nitrites (NO2 -). So why be concerned about this type of nitrogen? Most of the nitrates and nitrites found in a treatment facility are a result of biological action in the mixed liquor. Under the right conditions in biological treatment, a lot of the organic nitrogen is decomposed into ammonia. Certain bacteria then oxidize the ammonia to nitrite. Other bacteria further oxidize the nitrite to nitrate. As a result, nitrates are very often the most predominant nitrogen compound leaving a biological treatment facility.

Under low oxygen conditions in a wastewater treatment facility or in the environment, some types of microorganisms that require oxygen to survive can scavenge the needed oxygen from nitrate molecules, converting the nitrate to nitrogen gas in the process. Uncontrolled, this can cause a lot of matter to float, either in a wastewater treatment facility clarifier designed for matter to sink, or in the environment where sediment therefore becomes mobile and may locate to undesirable locations downstream.

For NPDES purposes, the only approved procedure for nitrite analysis is a fairly straightforward colorimetric method. After the sample is pH adjusted, the nitrite is reacted with another chemical creating a reddish-purple solution. The intensity of this color is related to the concentration of nitrite. Samples for nitrite analyses can be collected in either glass or plastic containers. Holding time is only forty-eight hours at 4 degrees C.

The most common way to analyze for nitrate in a sample is to convert the nitrate to nitrite either by a cadmium reduction column or by using hydrazine sulfate. The resulting solution is then analyzed for nitrite. A replicate sample with no nitrate-to-nitrite conversion is analyzed for nitrite only and the difference in value between the two samples is the nitrate value. Samples for nitrate-nitrite analyses can be collected in either glass or plastic containers. After a pH adjustment to less than 2 using sulfuric acid and cooled to 4 degrees C, a sample will have a holding time of up to twenty-eight days before analysis.

The analysis of nitrogen is important in assessing the impact of this nutrient on our wastewater facilities and in our local waterways. Knowing which form of nitrogen is prevalent in a system will help in determining the appropriate treatment or remedial actions, if needed.

The information in this article is very general. As usual, check your federal, state, and local regulations. You may have additional requirements that you must meet. Approved methods for NPDES reporting purposes are listed in Chapter 40 of the Code of Federal Regulations, part 136.  

    If you have any questions, suggestions, or comments, please contact LPC Chair Paul Fitzgibbons at (401) 222-6780 ext 118 ( or Tim Loftus at (508) 949-3865 ( You can also visit our website at Once on the website, press the Lab Practices button.                




Top of Maine Wastewater Lagoon systems


  Copyright 2003 |  Home | Site Map                                          

Search  |  Contact Us  | Links