Mass Balance and Measuring Plant Performance - Basic Mathematics for Water and Wastewater Operators - page 191

BOD in = 247 mg/L

BOD out = 17 mg/L

93% Removal

FIGURE 13.3 Illustration for Example 13.3.

Solution:

(247 mg/L − 17 mg/L) × 100

%Removal = = 93%

247 mg/L

u nit p roCess p erforManCe and e ffiCienCy
Equation 13.1 is also used to determine unit process efficiency. The concentration
entering the unit and the concentration leaving the unit (e.g., primary, secondary) are
used to determine the unit performance.

■ Example 13.4
Problem: As shown in Figure 13.4, the primary influent BOD is 235 mg/L, and the
primary effluent BOD is 169 mg/L. What is the percent removal?

Solution:

(235 mg/L − 169 mg/L) × 100

%Removal = = 28%

235 mg/L

BOD in = 235 mg/L

BOD out = 169 mg/L

28% Removal

FIGURE 13.4 Illustration for Example 13.4.