Comparison of Equations

Table 4.22 contains a summary of selected equations developed to predict ammonia nitrogen and TKN removal in diffused-air aerated lagoons (Middlebrooks and

TABLE 4.20

Wastewater Characteristics and Operating Conditions for the Five Aerated Lagoons

System

TABLE 4.20

Wastewater Characteristics and Operating Conditions for the Five Aerated Lagoons

System

North

Parameter

Pawnee

Bixby

Koshkonong

Windber

Gulfport

BOD (mg/L)

473

368

85

173

178

COD (mg/L)

1G26

635

196

424

338

TKN (mg/L)

51.41

45.G4

15.3

24.33

26.5

NH3-N (mg/L)

26.32

29.58

1G.G4

22.85

15.7

Alkalinity (mg/L)

242

154

397

67

144

pH

6.8-7.4

6.1-7.1

7.2-7.4

5.6-6.9

6.7-7.5

Hydraulic loading rate

G.G213

G.G285

G.G423

G.G663

Organic loading rate (kg BOD5 ha-1 d-1)

Organic loading rate (kg BOD5 ha-1 d-1)

Detention time (d)

Source: Data from Earnest et al. (1978), Englande (1980), Gurnham et al. (1979), Polkowski (1979), Reid and Streebin (1979).

Pano, 1983). All of the equations have a common database; however, the data were used differently to develop several of the equations. The "System" column in Table 4.22 describes the lagoons or series of lagoons that were used to develop the equation. An explanation of the system combinations was presented above. These combinations of data were analyzed statistically, and the equations presented in Table 4.22 were selected based on the best statistical fit of the data for the various combinations that were tried. The combinations of data are not directly comparable, but the presentation in Table 4.22 takes into account the best statistical fit of the data.

A comparison of the hydraulic detention times calculated using the various formulas for TKN removal show that the maximum deviation between the maximum and minimum detention times calculated from the equation is 14%. In view of the wide variation in methods used to develop the various relationships, this is a very small deviation. All of the relationships are statistically significant at levels higher than 1%. The small difference in detention times calculated using all of the expressions establishes a good basis to apply any of the relationships in the design of lagoons to estimate TKN removal. Because of the simplicity of the plug-flow model and the fraction-removed model, it is recommended that these two be employed, with the others used as a check to ensure adequate removal in the event that unusual loading rates or BOD5 loading rates are encountered.

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