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.
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Wastewater Engineering




Linvil G. Rich
Alumni Professor Emeritus
Department of Environmental
 Engineering and Science

Clemson University - 
Clemson, SC 29634-0919 USA
Tel. (864) 656-5575; Fax (864) 656-0672


Technical Number 1




In spite of the fact that effluent BOD5 is a key parameter in many discharge permits for aerated lagoons, it is the most misleading. Most effluent BOD5 data are flawed as the result of being inflated by nitrification that occurs in the BOD5 test itself. It has been reported that as many as 60 percent of the BOD5 violations nationally may have been caused by nitrification in the BOD5 test rather than by improper design or operation (Hall and Foxen 1983). Consequently, millions of dollars may have been spent needlessly on new treatment facilities.

    The total BOD of a wastewater is composed of two components – a carbonaceous oxygen demand and a nitrogenous oxygen demand. Traditionally, because of the slow growth rates of those organisms that exert the nitrogenous demand, it has been assumed that no nitrogenous demand is exerted during the 5-day BOD5 test. Although, such assumption is valid when the test is performed on untreated municipal wastewaters, it is not valid when performed on secondary effluents, especially those from aerated lagoons. The BOD5 of effluents from the latter are almost always inflated by a nitrogenous component. Moreover, unlike the carbonaceous demand which is proportional to the concentration of the biodegradable carbon constituents in the effluent, the nitrogenous demand exerted during the 5-day test is proportional to the number of nitrifying organisms that happen to be caught in the sample being tested. Thus the argument that the test provides insight on the impact that the effluent will have on the receiving water can not be defended. Neither can the practice of making waste-load allocations from models that contain both a BOD5 (assumed to be a measure of the carbonaceous demand) and a nitrogenous demand.

The severity of the problem is illustrated in Figs. 1 and 2. Figure 1 compares the effluent BOD5 with the CBOD5 (carbonaceous component of the BOD5). The CBOD5 is determined by using a nitrification suppressant in the BOD5 test. Figure 2 compares the two parameters in filtered samples. Note should taken of the magnitude of the nitrification factor in the 5-day test. Similar magnitudes are observed in effluents from aerated lagoons in warmer climates.


Figure 1
click on graph to enlarge


Figure 1 above illustrates Effluent BOD5 and CBOD5 data from an aerated lagoon system in Maine that treats a domestic wastewater. (Courtesy of George Bloom, Woodard and Curran, Engrs. Taken from Rich (1999))

aerated lagoons



Figure 2
click on graph to enlarge

Nitrification in the BOD5 test has been thoroughly researched and documented (Young 1973; Dague 1981; Barth 1981; Carter 1983; Chapman et al. 1991). Such nitrification can be eliminated by the use of commercially available nitrification inhibitors, a practice recommended by Standard Methods (1995). Chapman et al. (1991) demonstrated that by cleaning the sampler tubing weekly with chlorine bleach, nitrification in the BOD5 test can be reduced. The U.S. EPA has given their approval to the use of a nitrification inhibitor, provided that the effluent permit states the limit in terms of the CBOD5 instead of the BOD5. Arguing that secondary BOD5 limits were initially established on the basis of values flawed by nitrification, the EPA has suggested that the CBOD5 limit for secondary treatment be 25 mg/L rather than the 30 mg/L allowed when the limit is stated in terms of BOD5 (Hall and Foxen 1983). Considering the fact that the nitrification component of the BOD5 is generally at least 5 mg/L and frequently as high as 50 mg/L, the 25 mg/L limit appears to impose no handicap.

In summary, BOD5 is an ambiguous parameter when applied to secondary effluents, especially those of aerated lagoons, and should not be used. Instead, use should be made of the CBOD5 test which specifically measures the concentration of the biodegradable carbonaceous materials.


Barth, E. F. (1981). “To inhibit or not to inhibit: that is the question.” J. Wat. Pollut. Control Fed., 53(11), 1651-1652.

Carter, K. B. (1984). “30/30 hindsight.” J. Wat. Pollut. Control Fed., 56(4), 301-305.

Chapman et al. (1991). “Minimizing the impact of nitrification in nitrifying wastewaters.” Operations Forum, WPCF, Sept. 14-16.

Dague, R. E. (1981). “Inhibition of nitrogenous BOD and treatment plant performance evaluation.” J. Wat. Pollut. Control Fed., 53(12), 1738-1741.

Hall, J. C. and Foxen, R. J. (1983). “Nitrification in the BOD test increases POTW noncompliance.” J. Wat. Pollut. Control Fed., 55(12), 1461-1469.

Rich, L. G. (1999). High Performance Aerated Lagoon Systems. American Academy of Environmental Engineers.

Young, J. C. (1973). “Chemical methods for nitrification control.” J. Wat. Pollut. Control Fed., 45(4), 637-646.

Technical Note 1 Effluent BOD5 - A Misleading Parameter For the Performance of Aerated Lagoons Treating Municipal Waste
Technical Note 2 Aerated Lagoon Effluents
Technical Note 3 Control of Algae
Technical Note 4 Nitrites and Their Impact on Effluent Chlorination
Technical Note 5 Aerated Lagoons for Secondary Effluent
Technical Note 6

Nitrification in Aerated Lagoons With Intermittent Sand Filters

Technical Note 7

Mixed Liquor Recycle (MLR) Lagoon Nitrification System

Technical Note 8 Facultative Lagoons - A Different Technology
Technical Note 9 Sludge Accumulation in High Performance Aerated Lagoon Systems
Technical Note 10

Ammonia Feed Back in the Sludge of a CFID Nitirification System



aerated lagoons

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