Evaporation process for treating high-salinity industrial wastewater at low temperatures and ambient pressure

Abstract

High-salinity industrial wastewater is difficult to treat. In this study, an evaporation process for use in cooling towers and seawater desalination was adapted to treating high-salinity wastewater under gentle operating conditions. Real wastewater and simulated wastewater containing sodium chloride and glucose were used in this study. An evaporation unit, with an evaporation rate of 5 L/h, was designed and installed in the laboratory. Analysis revealed the effects of operating factors on the quality of condensed water, as well as the relationship between the mass transfer coefficient and wastewater characteristics. The results showed that for the selected system, when the inlet air speed was below 2.5 m/s and the wastewater flow rate was below 1.0 m³/h, the total dissolved solids and the chemical oxygen demand removal efficiencies could reach up to 99.9%. The most significant difference between the mass transfer coefficients of the clean water and simulated wastewater was 30.9% under identical operating conditions. The equation of the mass transfer coefficient considering the density, viscosity, and saturated vapor pressure of wastewater was built to predict the mass transfer efficiency for this process. A case study using real wastewater from a pharmaceutical factory illustrated that the system performed well in practical situations. The predicted mass transfer coefficient agreed well with the measured value. In summary, the developed evaporation system has good prospects for the treatment of high-salinity industrial wastewater.

Keywords:

• Wastewater treatment
• Evaporation
• Low temperature and ambient pressure
• Mass transfer coefficient
• Wastewater characteristics

Acknowledgements

The authors gratefully acknowledge the financial support from the National Natural Science Foundation of China (grant number 50978118). The authors are thankful to Dr Shuang Tong, at China University of Geosciences (Beijing) and Dr Samuel Ma, at Texas A&M University for their technical assistance.