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Wastewater treatment is in a dilemma: more energy and efforts have to be put forth to obtain an effluent with better quality, while a significant amount of sludge is generated and the treatment or disposal expenses are high. Even if the sludge is disposed of properly, the components can be released and pollute the environment again. Therefore, conversion and recovery of the contaminants to resources is the way out of the dilemma. An ion exchange membrane (IEM) is a special type of membrane, which allows charged solutes to pass through it while retaining uncharged components. Attributed to this character, IEMs are taking more important roles in separation and conversion processes recently. They act as key elements in many resource recovery systems, such as in separation and concentration, salt valorization, energy conversion, and even in microbial systems. This review summarizes the important processes for waste conversion and resource recovery from wastewaters by using IEMs. Drawbacks and perspectives are summarized in view of the development of the processes and the membranes.

Aim: To increase the transformation rate of L L-sorbose to 2-keto-L L-gulonic (2-KLG) acid in a two-step process of L L-ascrobic acid manufacture by ion beam. Methods and Results: Gluconobacter oxydans (GO29) and Bacillus megaterium (BM80) were used in the present study. Ion implantation was carried out with the heavy ion implantation facility at the institute of Plasma Physics in China. 2-KLG in whole culture broth was determined by iodometry. Mutants were screened by singlecolony isolation and 2-KLG accumulation in broth. GO29 and BM80 were implanted by either hydrogen ions (H + ) or nitrogen ions (N + ) with various doses, respectively. The average transformation rate of GM112-302 bred by ion beam in Gram-molecule was increased from 79AE3 to 94AE5% after eight passages in shaking flasks. Furthermore, in 180-ton fermentors in Jiangsu Jiangshan Pharmaceutical Co. Ltd, the transformation rate was stable at 92AE0%, indicating a producer could get 0AE99 kg of gulonic acid from 1AE0 kg of sorbose. Conclusion: Ion beam as a new mutation source had potential advantages in breeding. Comparing with original mixture GO29 and BM80, GM112-302 is more efficient in accumulating 2-KLG, especially at the later phase. Significance and Impact of the Study: GM112-302 bred by ion beam implantation dramatically increased the transformation rate by 19AE2%, which greatly increased efficiency and reduced the cost of L L-ascorbic acid manufacture in a two-step process.