Water. desalination + reuse

DWR NovDec 2015

Water. Desalination + reuse

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TECHNOLOGY _________ Eduard Cortada, Jordi Aumatell, Núria Adroer, Irene Marian Adiquimica. ___ Membrane fouling is a persistent thorn in the side of reverse osmosis desalination that erodes plant efficiency and economics. And the agents used in cleaning membranes to counter fouling can mar the environmental record of reverse osmosis facilities. The authors describe a detailed analysis of the performance of a proprietary cleaner developed by Adiquimica to tackle the challenges in membrane cleaning while doing so at concentrations that minimize its environmental impact. Membrane performance loss in reverse osmosis (RO) desalination of seawater or wastewater is due mainly to four types of fouling: • plugging of the membrane surface due to deposition of particulate matter and colloidal particles; • microbiological contamination due to microorganisms growth on membrane surface; • adsorption of organic matter; and • scaling and metal oxide fouling due to the precipitation of sparingly soluble salts and metal hydroxides and oxides in the rejected water. Colloidal fouling is an important limiting factor of RO system performance. In natural waters, colloidal foulants include clays, colloidal silica, hydrous metal oxides, bacteria and organic debris. Colloidal fouling is principally caused by deposition of colloids onto the membrane surface and it can be reduced by pre-treatment of the raw source water. However, pre-treatment processes do not remove all colloids from the feedwater. Colloids with particle diameters below 2 µm can pass through pre treatment systems and cause fouling of the RO membranes. Membrane fouling due to natural organic matter can also cause a significant decline in the performance of the membrane. And the presence of organic matter in natural waters provides a favorable environment for microbiological growth which can result in biofouling. Fouling by colloidal and organic matter is difficult to remove from the membrane with commodity cleaners such as acid or alkali solutions. Adiquimica has designed and developed a powdered cleaner, Adiclean S-152, to operate at low concentrations to remove colloidal fouling, organic foulants and biofouling. S-152 is a buffered alkaline cleaner containing agents that generate effervescence which increases its efficiency in removing organic and colloidal deposits. A clean sweep: analysis of a foulant remover Focus on fouling: there is a role for diagnostic software in the battle with fouling. November-December 2015 | Desalination & Water Reuse | 27 |

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