Zero liquid discharge - a topic for the future

Given the shortage of water resources and the increasing costs for water treatment and waste water disposal, the demand for new recycling technologies is rising.The subject of reducing waste water volumes to the point where waste water can be avoided entirely, as well as the multiple use of treated waste water, is the most discussed topic in water management in the steel industry.
At the same time, ‘zero liquid discharge’ (ZLD) concepts are being considered for individual branches of industry for a variety of reasons. When it comes to their implementation, however, priority is given to economic factors. The degree of implementation depends on the economic and ecological boundary conditions.From the treatment of the available water using measures integrated into the production process – up to waste water treatment – ZLD applies to the entire process chain.


ZLD – What is it?

Zero Liquid Discharge is a process that is beneficial to industrial enterprises as well as to the environment because it cuts down on expenses and no effluent - or liquid discharge - is being generated.

The target ZLD is reached by:

  • Systematic and consequent recovery of water from effluent
  • Separation by evaporation of water/ wastewater in evaporators, crystallizers and condensate recovery.
  • Conversion of liquid elements of wastewater into disposable/ reusable solids, such as sludge, salt
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ZLD solution with conventional procedure

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Conventional End-of-pipe Technology

  1. Waste water to be discharged
  2. Chemicals /additives to be deposited

⇒ Both represent a source of valuable substances!

Integrated and zero-emission technology

Trend:
Increasing demand for integrated and zero-emission technologies instead of end-of-pipe-technologies due to environmental constraints and raw water shortages.

Prerequisites for reasonible usage:
⇒ Integrated and zero-emission-technologies have to be cost efficient.


ZLD – Example

Wastewater treatment at a tin plate production facility
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ZLD System

ZLD systems employ the most advanced wastewater treatment technologies to purify and recycle virtually all of the wastewater produced.

Also, zero liquid discharge technologies help industries to meet discharge and water reuse requirements, enabling businesses to:

  • Treat and recover valuable products from waste streams.
  • Better manage processed water.

Advantages:

  • Decrease of the raw water consumption by 75-80%
  • Especially recommended for arid areas
  • Means of choice with high environmental credentials

Disadavantages:

  • Additional investment for evaporator and crystallizing units