Development Of Integrated Process Based On Membrane Distillation For Wastewater With High Salinity And High Organic Compounds Concentration

Nowdays, wastewater from industry is damaging the environment and affecting human health. However, wastewater from industry is difficult to be treated especially those with high salinity and high organic compounds concentration. One example is resin wastewater. In this work, the treatment of epoxy resin wastewater through vacuum membrane distillation has been investigated. Furthermore, an intergrated process for recovering salt from the wastewater has been developed.Firstly, the wastewater from epoxy resin industry has been analyzed. There are bisphenol A, NaCl, glycerin and a small amount of ageing resin in the alkaline wastewater. According to the analytical result, the wastewater is treated by neutralization, filtration, membrane distillation and evaporative crystallization in turn.The effects of operation conditions in vacuum membrane distillation on water flux and salt rejection are investigated in detail. The operation conditions are ordinary pressure, temperature at 303~553K, flow rate from 40 to 60L/h, and the vacuum degree 0.4~0.95bar at downstream. The results show that the water flux increases with flow rate, temperature and vacuum degree. It is found that the water flux is greater when wastewater cycles in tub side than in shell side. After the wastewater with high salt concentration (10wt%) and COD value(7500ppm) has been treated through the vacuum membrane distillation, the COD and salt concentration of the permeate are less than 20ppm and 0.01wt% respectively, and the salt concentration of retention increases from 10wt% to 30wt%.In the pilot-plant of membrane distillation process, the water flux is 750ml/h.m~2, and rejection rate of salt is more than 99.9%. Finally, a preliminary design for treating wastewater with salt concentration of 100g/L and with yield of 60T/d has been finished.