Mixed Liquor Suspended Solid Calculator

MLSS Formula:

\[ MLSS = \frac{(Sewage\ Flow \times Influent\ BOD)}{(Food\ to\ Microorganism\ Ratio \times Volume\ of\ Tank)} \]

Sewage Flow (Q):

m³

Influent BOD (Qi):

kg/m³

Food to Microorganism Ratio (FM):

Volume of Tank (V):

m³

Mixed Liquor Suspended Solid (MLSS):

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1. What is Mixed Liquor Suspended Solid (MLSS)?

MLSS is the concentration of suspended solids in the mixed liquor within an aeration tank during the activated sludge process. It represents the biomass concentration and is a key parameter in wastewater treatment plant operation.

2. How Does the Calculator Work?

The calculator uses the MLSS formula:

\[ MLSS = \frac{(Q \times Qi)}{(FM \times V)} \]

Where:

\( Q \) — Sewage Flow (m³)
\( Qi \) — Influent BOD (kg/m³)
\( FM \) — Food to Microorganism Ratio
\( V \) — Volume of Tank (m³)

Explanation: The formula calculates the concentration of suspended solids by considering the incoming food load relative to the microbial mass in the treatment system.

3. Importance of MLSS Calculation

Details: MLSS is crucial for monitoring and controlling the activated sludge process. It helps determine the appropriate sludge age, ensure proper treatment efficiency, and maintain optimal microbial activity in the aeration tank.

4. Using the Calculator

Tips: Enter sewage flow in cubic meters, influent BOD in kg/m³, food to microorganism ratio (dimensionless), and tank volume in cubic meters. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical range for MLSS in activated sludge systems?
A: MLSS typically ranges from 1500-4000 mg/L (1.5-4.0 kg/m³) in conventional activated sludge systems, depending on the process design and wastewater characteristics.

Q2: How does MLSS affect treatment efficiency?
A: Higher MLSS concentrations generally improve treatment efficiency but require more oxygen and may lead to settling problems if too high.

Q3: What is the relationship between MLSS and F/M ratio?
A: F/M ratio (Food to Microorganism ratio) is inversely proportional to MLSS. Higher MLSS results in lower F/M ratio, indicating more microorganisms available per unit of food.

Q4: How often should MLSS be measured?
A: MLSS should be measured daily in most treatment plants to ensure proper process control and make necessary adjustments to wasting rates.

Q5: What factors can affect MLSS concentrations?
A: Factors include wastewater strength, temperature, sludge age, wasting rates, aeration efficiency, and settling characteristics of the sludge.