What is MLSS & MLVSS | Standard Range of MLSS and MLVSS | Low MLSS | High MLSS.

In this video, we explain MLSS (Mixed Liquor Suspended Solids) and MLVSS (Mixed Liquor Volatile Suspended Solids) in a simple and practical way for ETP/STP operation. 🔹 What is MLSS? MLSS represents the total concentration of suspended solids (biomass + inert matter) present in the aeration tank. It indicates how much sludge is available for biological treatment. 🔹 What is MLVSS? MLVSS is the organic (volatile) portion of MLSS, mainly representing active microorganisms responsible for pollutant removal. Standard MLSS & MLVSS Range ✔ Typical MLSS Range: • 2,000 – 4,000 mg/L (Conventional ASP) • Up to 6,000 mg/L (Extended Aeration / MBR) ✔ MLVSS as % of MLSS: • 65% – 80% of MLSS (Healthy biomass) MLVSS / MLSS Ratio – What It Indicates 🔸 0.65 – 0.80 → Healthy and active sludge 🔸 Below 0.6 → High inert solids / old sludge 🔸 Above 0.85 → Very young sludge / shock load Low MLSS – Causes & Effects ⚠ Causes: • Excess sludge wasting • Low organic load • Toxic shock • Short sludge age ⚠ Effects: • Poor BOD/COD removal • Low settling sludge • Process instability High MLSS – Causes & Effects ⚠ Causes: • Inadequate sludge wasting • High influent load • Poor sludge settleability ⚠ Effects: • Low DO in aeration tank • High power consumption • Sludge bulking & foaming Low MLVSS – What It Means ❌ Indicates less active biomass ❌ More inorganic or dead sludge ❌ Reduced biological treatment efficiency Key Takeaways ✅ MLSS shows total sludge concentration ✅ MLVSS shows active biomass strength ✅ MLVSS/MLSS ratio is critical for process control ✅ Proper sludge wasting maintains plant health 📌 This video is useful for: ETP/STP Operators | Environmental Engineers | Plant Utilities | Process Engineers 🔔 Subscribe to Industrial Guru for practical industrial operation knowledge.