Investigation of severe UF membrane fouling induced by three marine algal species.

Reducing membrane fouling caused by seawater algal bloom is a challenge for regions of the world where most of their freshwater is produced by seawater desalination. This study aims to compare ultrafiltration (UF) fouling potential of three ubiquitous marine algal species cultures (i.e., Skeletonema costatum-SKC, Tetraselmis sp.-TET, and Hymenomonas sp.-HYM) sampled at different phases of growth. Results showed that flux reduction and irreversible fouling were more severe during the decline phase as compared to the exponential phase, for all species. SKC and TET were responsible for substantial irreversible fouling but their impact was significantly lower than HYM. The development of a transparent gel layer surrounding the cell during the HYM growth and accumulating in water is certainly responsible for the more severe observed fouling. Chemical backwash with a standard chlorine solution did not recover any membrane permeability. For TET and HYM, the Hydraulically Irreversible Fouling Index (HIFI) was correlated to their biopolymer content but this correlation is specific for each species. Solution pre-filtration through a 1.2 µm membrane proved that cells and particulate algal organic matter (p-AOM) considerably contribute to fouling, especially for HYM for which the HIFI was reduced by a factor of 82.3.

Problems of operation and main reasons for failure of membranes in tertiary treatment systems.

This paper presents the results of the long-term operation and monitoring of membrane fouling at several full-scale MF/RO water recycling facilities operated by Agbar in Spain. It was demonstrated that membranes give very reliable treatment enabling the production of high-grade recycled water, well disinfected and with the removal of all priority substances. The high organic and salt concentrations of raw wastewater combined to extremely high variations justified the implementation of sand filtration to protect MF/RO membranes. Membrane autopsy was used to better understand the predominant fouling mechanisms and optimise down-stream operation and membrane cleaning strategy. The main membrane pathologies are described with recommendation of an adequate cleaning strategy.

Wet peroxide oxidation of chlorophenols.

This study evaluates the application of Wet Peroxide Oxidation (WPO) for the treatment of solutions containing 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP). These compounds are of special interest due to their high toxicity and low biodegradability. WPO is included in the Advanced Oxidation Processes, which are technologies based on an initial formation of hydroxyl radicals that further oxidize the organic matter. The influence of some operating conditions such as temperature, dosage of hydrogen peroxide and initial concentration of the chlorophenols was studied in absence of a catalyst. The results of this study prove that 4-CP and 2,4-DCP can be completely removed from wastewaters by means of WPO. Total Organic Carbon (TOC) and 4-CP removals of 72.3% and 100%, respectively, were achieved working at 100 degrees C with 2.5 mL of H(2)O(2) and an initial concentration of 500 ppm of 4-CP after 90 min of reaction. Under the same conditions but with an initial concentration of 500 ppm of 2,4-DCP a TOC removal of 59% and a complete removal of the target compound were achieved.