Scaling of reverse osmosis (RO) membrane surface is one of the main problems in desalination proc- esses. To mitigate scales, organic anti-scalants are often used. If the dosages of anti-scalants are reduced, by using other much cheaper scale inhibitors, RO running cost will decrease greatly. The present paper investigated the inhi- bition of CaCO3 precipitation by zinc ions in RO system. The results show that the zinc ion concentration of 2mg?L-1 was able to exert a marked suppression effect on both bulk precipitation of CaCO3 and on membrane scaling on waters of moderate hardness.
Reverse osmosis (RO) desalination is universally recognized as the most cost effective technology for desalting both brackish water and sea-water.The design of the vast majority of RO desalination plants is based on spiral wound membrane modules.Though spiral wound modules show overall favorable performance, there is still much room for improving their flow performance and thereby lowering water costs.Improved module design could be achieved by better understanding of the geometric and operating parameters that determine the complex flow patterns in a spiral wound module.It is widely recognized that flow maldistribution can have a negative impact on module performance.Residence time distribution (RTD) tests have a potential for on-line detection of such defects.In the present study, RTD techniques were used to characterize the degree of uniformity of flow in the membrane passages and diagnose flow distribution defects.RTD data showed that feed pressure had no effect at all on the magnitude of the dispersion coefficient indicating no distortion of the flow passages by pressure increase.Significant deviation from ideal plug flow was found in the laboratory size and industrial size RO systems.In both systems, the dispersion coefficient increased roughly linearly with the Reynolds number.
