Ochando-Pulido Javier Miguel
Chemical Engineering Department, University of Granada, 18071 Granada, Spain E-mail:
Water Sci Technol. 2017 Dec;76(11-12):2968-2978. doi: 10.2166/wst.2017.444.
Proper membrane process design can be a difficult task to accomplish when fouling is present, and must be faced. Engineers usually consider the project variables concerning productivity and selectivity and follow these targets. However, in the presence of fouling, additional parameters must be considered, implying better knowledge of fouling phenomena. One possible solution to increase the reliability of a process is the use of stable control systems. This article reports a suitable method to reach this target, based on the boundary flux theory. The knowledge of the boundary flux values permits avoidance of high fouling operating conditions on a selected membrane. The goal here was to determine the framework for control of an ultrafiltration (UF) and nanofiltration (NF) batch membranes-in-series process treatment for olive mill wastewater, relying on these boundary flux points, which will thereafter serve for the automatic control of the process by an advanced control system. In this work, boundary flux values equal to 10 L h m for the UF membrane module and 14.3 L h m for the NF one were estimated. Moreover, the membrane constant permeability loss, measured by integrating the sub-boundary fouling index, was estimated to be reduced in the order of 65.4% for the NF membrane after the applied pretreatment and UF. This strategy permitted attaining stable and constant productivity for both membranes. Moreover, it is shown that, relying on the boundary flux modelization, both types of control systems (feed control and pressure control) could be used reliably. The proposed approach could help safely narrow the overdesign of membrane processes due to fouling issues and thus would have an impact on the reduction of the costs for both membrane processes.
当存在膜污染时，要实现合理的膜过程设计是一项艰巨的任务，必须加以应对。工程师通常会考虑与生产率和选择性相关的项目变量，并遵循这些目标。然而，在存在膜污染的情况下，必须考虑额外的参数，这意味着要更好地了解膜污染现象。提高过程可靠性的一种可能解决方案是使用稳定的控制系统。本文报道了一种基于边界通量理论实现这一目标的合适方法。了解边界通量值有助于避免所选膜上出现高污染的运行条件。这里的目标是确定基于这些边界通量点的橄榄榨油厂废水超滤（UF）和纳滤（NF）串联分批膜处理过程的控制框架，此后将用于通过先进控制系统对该过程进行自动控制。在这项工作中，估计UF膜组件的边界通量值为10 L h m，NF膜的边界通量值为14.3 L h m。此外，通过积分亚边界污染指数测量的膜恒定渗透率损失，在经过预处理和UF后，估计NF膜的该损失降低了65.4%。该策略使两种膜都能实现稳定且恒定的生产率。此外，结果表明，基于边界通量建模，两种类型的控制系统（进料控制和压力控制）都可以可靠地使用。所提出的方法有助于安全地缩小由于膜污染问题导致的膜过程过度设计，从而对降低两种膜过程的成本产生影响。
