Clean Up Wastewater from PV Solar Panel Manufacturing
Photovoltaic panels, like computer chips are essentially semiconductor wafers made with silicon. Some of the newer PV materials may use toxic metals such as cadmium and selenium. In addition, PV modules are often imbedded with chemicals. The wastewater produced by PV manufacturing contains many hazardous chemicals, including heavy metals, halogenated compounds, acids and organic contaminants. Treatment and disposal of these toxic contaminants, therefore raises many technical and regulatory concerns. Currently, most manufacturers cope with the large amounts of contaminated wastewater by treatment and disposal. The waste is usually concentrated through bag filters - often at high costs - and is then sent to a waste disposal company.
As an alternative, ThermoEnergy offers a Zero Liquid Discharge (ZLD) system that is based on vacuum evaporation and flash distillation. Our system is actually able to distill purified water out of the waste stream, recycling almost 100% of the water, and nearly eliminating the need to add potable water to the process. More than 90% of the process chemicals and acids can be concentrated out of the waste stream and then reused in the manufacturing process as-is, or after minimal treatment.
In this process, the wastewater is heated in a reaction chamber under conditions of low pressure. The water in the solution evaporates into a vapor that rises through the vessel, and is then captured and condensed into a distillate of pure water which can then be used again in the rinsing process. Because the water evaporates at lower temperatures under vacuum conditions, less energy is needed to heat the effluent, and the system does not need to be constructed from special heat-resistant materials.
The remaining waste becomes more and more concentrated until the contaminants condense into solid form and can then be removed and reused in the manufacturing process. Because the water is recycled and the chemicals are reused, the amounts of wastewater and hazardous waste are reduced, or even eliminated. Some versions of this technology can enable PV manufacturers to operate without RCRA discharge permits for wastewater or hazardous waste and avoid the associated costs.