Water/Wastewater Laboratory Calculations - Basic Mathematics for Water and Wastewater Operators - page 240

■ Example 16.13
Problem: A settleability test is conducted on a sample of MLSS. What is percent
settleable solids if 420 mL settle in the 2000-mL graduate?

Solution:

Settledsolids(mL)
2000

420 mL
2000 mL

%Settleable solids = ×= ×= 100 100 21%

-mLsample

■ Example 16.14
Problem: A 2000-mL sample of activated biosolids is tested for settleability. If the
settled solids are measured as 410 mL, what is the percent settled solids?

Solution:

Settledsolids(mL)
2000

410 mL
2000 mL

%Settleable solids = ×= ×= 100 100 20 .%

-mLsample

SETTLEABLE SOLIDS
The settleable solids test is an easy, quantitative method to measure sediment found
in wastewater. An Imhoff cone (see Figure 16.2) is filled with 1 L of sample waste-
water, stirred, and allowed to settle for 60 min. The settleable solids test, unlike the
settleability test, is conducted on samples from the sedimentation tank or clarifier
influent and effluent to determine percent removal of settleable solids. The percent
settleable solids is determined by the following equation:

removed(mL/L)
Settledsolidsininfluent(mL/L)

Settled solids

%Settleable solids removed = ×100 (16.13)

Imhoff cone

Settled solids (mL)

FIGURE 16.2 1-liter Imhoff cone.