ENVIRONMENTAL IMPACTS OF ZERO LIQUID DISCHARGE TECHNOLOGIES

Abstract

As water scarcity becomes more and more severe, to recover and reuse water in the industrial systems attracts much attention all over the world. Zero Liquid Discharge (ZLD), an ambitious industrial wastewater treatment technology, aims to eliminate any liquid waste leaving the treatment systems. The technology has been developing rapidly nowadays, raising from thermal systems to varieties of membrane systems including Reverse Osmosis, Forward Osmosis, Electrodialysis, Bipolar Electrodialysis, as well as Membrane Distillation. Considering the energy consumption, chemical inputs, and membrane uses for each system, I utilized Life Cycle Assessment (LCA) to compare the environmental performance of six ZLD systems. I set the functional unit at 10,000 m3 feedwater treated, which reflects 4.3-91.0 hours operation of the treatment plants for current capacity in large urban centers. As a result, BMED is the most environmentally friendly ZLD technology, consuming about 34,438 kWh of electricity per functional unit, compared with 260,640 kWh for conventional thermal systems. Using coal powered electricity as the energy source, BMED ZLD systems could reduce CO2 emissions by up to 82.1% compared with conventional thermal systems. Electricity power sources are also an influential factor for environmental impacts. Using electricity from cleaner energy power plants helps reduce CO2 emissions and other environmental impacts. In a BMED system, the ecosystem impact of using nuclear powered electricity would be only 1.9% of that of using coal powered energy.