Page 520 - Industrial Wastewater Treatment, Recycling and Reuse

490 Industrial Wastewater Treatment, Recycling, and Reuse

discharge but also to lead to water conservation, which is critical for regions
experiencing water scarcity. This chapter first outlines the challenges faced
in developing and maintaining ZLD and then delves into various aspects of
overcoming these challenges and finding practical solutions to avoid liquid
effluent. Technological aspects are discussed in this regard, addressing
effective recovery of water, along with different case studies pertaining to
the greater part of the chemical industry.

13.2 ZERO LIQUID DISCHARGE

Any process or combination of processes, by virtue of which there is no liquid
effluent, or discharge from a process plant

It implies that wastewater is treated and effectively recycled and reused such
that there is no effluent discharge. ZLD is usually accomplished by concen-
trating the effluent using various techniques, including membrane-based and
multi effect evaporation based systems. ZLD involves:
• The elimination of the liquid waste effluent stream from the plant
• The recycling of recovered water and solids
• The establishment of no liquid pollutant norms.

13.2.1 Challenges of ZLD
There are several challenges facing those trying to develop and implement
ZLD. Some of these challenges include:
• Developingahighrecoverysystemtocapturemorethan95%ofwastewater
• Effluent composition
• Effluent characteristics and related corrosion and temperature issues
• Material compatibility
• Operating cost for the treatment.
The challenge is to select the appropriate technologies based on wastewater
characteristics and volumes. Thus, techno-economic considerations are
important in devising a zero discharge strategy.

13.2.2 Accurate Analysis of Generated Effluent
For zero discharge technology to work efficiently, it is essential to obtain
accurate analyses of generated effluents. Some of the key parameters to be
determined are as follows:
▪ Total dissolved solids (TDS): This parameter determines the evaporation
duty and salt handling capacity.