Glossary
Water treatment glossary: key terms defined
- BOD — Biochemical Oxygen Demand
- BOD is the amount of oxygen consumed by microorganisms as they break down organic matter in water, and is the core measure of organic load. CPCB limit for inland surface water discharge: ≤ 30 mg/L.
- COD — Chemical Oxygen Demand
- COD is the amount of oxygen needed to chemically oxidise the organic and inorganic matter in water. CPCB limit for inland surface water discharge: ≤ 250 mg/L.
- TDS — Total Dissolved Solids
- TDS is the total concentration of dissolved salts and minerals in water, measured in mg/L. It is removed by reverse osmosis (RO) membranes.
- KLD / MLD — Kilolitres per day / Million litres per day
- KLD and MLD are units of treatment plant capacity: kilolitres per day and million litres per day. 1 KLD = 1,000 litres per day; 1 MLD = 1,000 KLD.
- MEE — Multiple Effect Evaporator
- An MEE is a thermal evaporator that concentrates RO reject brine in a Zero Liquid Discharge system. It reduces the liquid volume to a thick slurry.
- ATFD — Agitated Thin Film Dryer
- An ATFD is a dryer that turns MEE concentrate into a dry salt residue, so that no liquid remains.
- ZLD — Zero Liquid Discharge
- ZLD is a wastewater treatment approach in which no liquid effluent leaves the facility. Water is recovered and recycled back into the process; what remains is a dry solid.