Reverse Osmosis (RO) membrane fouling is one of the main challenges that membrane manufactures, the scientific community and industry professionals have to deal with. The consequences of this inevitable phenomenon have a negative effect on the performance of the desalination system. Predicting fouling in RO systems is key to evaluating the long-term operating conditions and costs. Much research has been done on fouling indices, methods, techniques and prediction models to estimate the influence of fouling on the performance of RO systems. This paper offers a short review evaluating the state of industry knowledge in the development of fouling indices and models in membrane systems for desalination in terms of use and applicability. Despite major efforts in this field, there are gaps in terms of effective methods and models for the estimation of fouling in full-scale RO desalination plants. In existing models applied to full-scale RO desalination plants, neither the spacer geometry of membranes, nor the efficiency and frequency of chemical cleanings are considered.

Reverse osmosis is a widely used and rapidly growing desalination technology. Despite the many benefits the technology has to offer, still challenging to all desalination plants is the environmentally sensitive effects attributed to the discharge into the sea of the rejected brine, which can very often severely damage the receiving environment, and air pollutant emissions attributed to the energy demand of the process. The list of potential impacts can be extended; however, the available information on the marine discharges alone indicates the need for environmental mitigation measures. In order to safeguard a sustainable use of the desalination technology, there is a need to develop, in the short term, new management proposals to achieve a minimization of the impact and valorization of brine. These alternatives should be both economically viable and effective, not only for new setting up plants, but also for those already installed. An adequate treatment sequence has been proposed and developed for reusing and valorizing this saline waste from seawater reverse osmosis desalination plants (SWRO), in the well-known chlor-alkali industry by NaCl electrolysis in membrane cells. This alternative has been described from a technological, economical, and environmental point of view towards sustainability of SWRO desalination plants of Gran Canaria (Canary Islands, Spain). The conclusions drawn out of this work refer to knowledge and control improvements concerning to the sustainability of desalination processes, to reduce the impact generated by brine disposal, and to reassess this saline residue as raw material in the chlor-alkali manufacturing industry.