Question

Multiple effect evaporator is commonly used, in the zero liquid discharge (ZLD) scheme, for ________

• A. oxidation of organic pollutants
• B. precipitation of heavy metals
• C. concentrating reverse osmosis (RO) reject salts
• D. performing selective ion exchange

Hint:

In Zero Liquid Discharge (ZLD) processes, RO is typically followed by MEE and crystallizers. RO removes most water, and MEE handles the concentrated brine, making it an essential step for salt concentration.

Answer 1

The Correct Option is C

Step 1: Understanding the role of multiple effect evaporators (MEE) in ZLD.
In a Zero Liquid Discharge (ZLD) system, the goal is to recover as much clean water as possible and minimize liquid waste. After reverse osmosis (RO), the reject water still contains a high concentration of dissolved salts and needs further treatment.

Step 2: Application of MEE.
A multiple effect evaporator is used to concentrate these RO reject salts by evaporating water in stages using the steam economy principle. This significantly reduces the volume of liquid waste.

Step 3: Conclusion.
Hence, the main purpose of MEE in ZLD is to concentrate the RO reject salts, preparing them for final crystallization or disposal.