What is the MLSS if the FF=2.50, PF=1.25, HF=54?

To find the Mixed Liquor Suspended Solids (MLSS), the formula commonly used is:

MLSS = FF × PF × HF.

In this case, we have the following values:

• FF (Food to micro-organism ratio) is 2.50,

• PF (Pump Factor) is 1.25,

• HF (Hydraulic Factor) is 54.

Plugging in these values:

MLSS = 2.50 × 1.25 × 54.

Calculating this step-by-step:

1. First, multiply the FF and PF:

2.50 × 1.25 = 3.125.

2. Next, multiply that result by the HF:

3.125 × 54 = 168.75 LF.

The correct answer of 168.75 LF represents the concentration of mixed liquor suspended solids in a septic system, which provides valuable insight for septic system design and management. This helps ensure that treatment processes are effectively removing contaminants, which is crucial for maintaining environmental hygiene and safety.

Thus, the correct choice is indeed the one that matches this computation.