MLD (MLD)
Also known as: Million Litres per Day · million litres per day · ML/day · 1000 KLD
MLD (Million Litres per Day) is a unit measuring large-scale liquid flow equal to 1,000,000 litres per day (1,000 KLD or 1,000 m³/day). It is used in India to express the capacity of city sewage treatment plants, water supply systems, and large industrial liquid discharge volumes.
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What is MLD?
MLD (Million Litres per Day) is the standard Indian unit for large-scale liquid flow, equal to 1,000,000 litres per day, 1,000 KLD, or 1,000 cubic metres per day. MLD is reserved for municipal-scale water supply, sewage treatment plants, river abstraction, and large industrial complexes — flows that exceed the convenient range of KLD. Most Indian recycling and CBG plants are sized in KLD; only large clusters of operations or city-scale infrastructure reach MLD.
Common MLD reference points:
- Municipal STPs — typical Indian city STPs range from 5 MLD (small towns) to 500+ MLD (metros). Delhi's combined STP capacity exceeds 2,400 MLD across 35 plants; Mumbai's is around 2,600 MLD
- Common Effluent Treatment Plants (CETPs) — industrial clusters in Gujarat (Ankleshwar, Vapi), Maharashtra (Tarapur, Dombivli), Tamil Nadu (Tirupur) operate CETPs of 5–50 MLD treating effluent from hundreds of small units
- Water supply mains — bulk water transmission pipelines are sized in MLD; a town of 100,000 population needs roughly 13–18 MLD of water supply at Indian per-capita norms
- Industrial water intake — large refineries, steel plants, and thermal power plants consume 50–500 MLD
MLD-scale effluent infrastructure carries proportionally larger capex and regulatory burden. A 10 MLD CETP costs ₹40–100 crore in capex and requires:
- Environmental Clearance — Category B1 under EIA Notification 2006
- HOWM Authorisation — for any hazardous waste handling
- OCEMS — continuous monitoring of flow, pH, BOD/COD, TDS, with public-facing dashboard
- Sludge management — bio-solids generation typically 20–50 tonnes per MLD per year, requiring dedicated dewatering and disposal
For CBG and recycling entrepreneurs, MLD-scale operations are uncommon at single-plant level but relevant when locating in industrial estates or SEZs that operate CETPs. Discharge agreements with the CETP operator typically specify volumetric KLD or MLD allocations, pre-treatment quality (so the CETP can handle the load), and fees per KL discharged. Exceeding allocation is the most common dispute, particularly during plant ramp-up when actual flows differ from design.
Common questions about MLD
Plain-English answers to what people most often ask.
What is the full form of MLD?
What is the difference between MLD and KLD?
When do recycling or CBG plants encounter MLD in their permit documents?
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