What is the Difference Between MLSS and MLVSS?
🆚 Go to Comparative Table 🆚The key difference between MLSS (Mixed Liquor Suspended Solids) and MLVSS (Mixed Liquor Volatile Suspended Solids) lies in the type of solids they measure. MLSS measures the total solids weight in a given sample, while MLVSS measures the total volatile fraction of the total solids in the same sample. Both terms are important in analytical chemistry, mainly in wastewater treatment plants, to evaluate the treatment process by analyzing the total solid content in the tanks.
- MLSS: This measures the total concentration of mixed liquor suspended (non-soluble) solids in the aeration basin of an activated sludge system. The solid content in MLSS includes microorganisms and non-biodegradable suspended matter. MLSS testing is crucial in determining the operational behavior of the system, as well as sludge wasting and recycling rates.
- MLVSS: This measures the total volatile fraction of the total solids in the given sample. The volatile solids remaining after the MLSS filter has been ignited to 550°C represent the biological portion of the MLVSS, which is considered the part of the MLSS responsible for BOD (biochemical oxygen demand) reduction. In some cases, fiber, cellulose, and other organic solids are included in the MLVSS.
In summary, MLSS and MLVSS are both used to measure solid content in wastewater treatment processes, but MLSS measures the total solids weight, while MLVSS measures the total volatile fraction of the solids.
Comparative Table: MLSS vs MLVSS
Here is a table comparing MLSS (Mixed Liquor Suspended Solids) and MLVSS (Mixed Liquor Volatile Suspended Solids):
| Parameter | MLSS (Mixed Liquor Suspended Solids) | MLVSS (Mixed Liquor Volatile Suspended Solids) |
|---|---|---|
| Measurement | Represents the total concentration of solids in the aeration tank, including both inert and organic solids. | Represents the total volatile fraction of the total solids in the sample, including biomass, non-degradable volatile suspended solids, and inert inorganic solid substances. |
| Concentration Range | Typically between 2,000 to 4,000 mg/L for conventional activated sludge plants. | Between 70% and 80% of the MLSS value. |
| Importance | Used to evaluate the treatment process in wastewater treatment plants by analyzing the total solid content in the tanks. | Provides an indirect measure of the concentration of microorganisms in the aeration tank. |
| Calculation | Calculated by multiplying the MLSS value by the MLVSS/MLSS ratio (usually around 0.80). |
Please note that the units for MLSS and MLVSS are typically milligrams per liter (mg/L) or grams per liter (g/L).