Pretreatment (oxidation, coagulation, ultrafiltration) of Red Sea water impacted by a Trichodesmium sp. algal bloom

Abstract : Prechlorination is used in seawater desalination processes to control biofouling in both thermal plants and membrane plants. Many disinfection byproducts (DBPs) are formed during seawater pretreatment processes using chlorination, including the regulated trihalomethanes (THMs) and haloacetic acids (HAAs). Nitrogenous DBPs (N-DBPs) generally form in much smaller amounts than regulated DBPs, but have been a growing concern because of their greater health risk. As an alternative disinfectant, monochloramine (NH2Cl) is often used in cooling systems to get a stable disinfectant residual. However, the use of NH2Cl can be a source of nitrogen and leads to the formation of N-DBPs. Moreover, the disinfection of seawater can produce important amounts of N-DBPs, especially during algal blooms, enriched in nitrogen-containing compounds (e.g., amino acids). Moreover, arid regions produce water by desalination of seawater or brackish water, characterized by elevated bromide and iodide ions contents. Brominated and iodinated DBPs are generally more toxic than their chlorinated analogues. Our previous work performed in the absence of algal bloom showed that DBPs produced during seawater prechlorination are found in significant quantity in the brines of desalination plants (RO and MSF plants) and in trace amounts in the drinking water. This study investigates the formation of disinfection by-products on seawater samples collected during a major bloom event (Trichodesmium sp.) that occurred on the west coast of Saudi Arabia (Yanbu). The removal of the Algal Organic Matter (AOM) during Fe-coagulation-flocculation and its UF fouling potential was also studied. The quality of the Red Sea water impacted by this severe algal bloom was characterized using global (i.e., TOC/DOC content, UV-Vis spectra) and specific parameters (Fluorescence excitation emission matrix, LC-OCD, Flow cytometry). The oxidant demand and the chlorination and chloramination formation potentials of chloro, bromo and iodo DBPs (THMs, HAAs, haloacetonitriles, haloacetamides) were determined at pH 8 for short (1 hour) and long contact time (72 hours). The monitored DBPs were quantified following EPA methods 551 and 552, which are based on liquid-liquid extractions followed by GC-ECD or GC-MS analyses. The efficiency of Fe-coagulation/flocculation to remove the DBP precursors was evaluated using Jar Test equipment under controlled experimental conditions (pH, dose). In addition ultrafiltration of the Trichlodesmium sp. algal bloom was performed with a home made UF hollow fiber module under conditions that mimic real seawater RO pretreatment operations. During our presentation the reactivity with oxidants and behavior during pretreatment of the Trichodesmium sp. AOM will be compared with the results obtained using the same experimental conditions with another seawater alga grown in our laboratory (i.e., Hymenomonas sp.).
Type de document :
Communication dans un congrès
International conference on Harmful Algal Blooms and desalination, Apr 2014, Muscat, Oman
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https://hal-enpc.archives-ouvertes.fr/hal-01211747
Contributeur : Julien Le Roux <>
Soumis le : lundi 5 octobre 2015 - 16:30:12
Dernière modification le : jeudi 18 janvier 2018 - 11:04:03

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  • HAL Id : hal-01211747, version 1

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Julien Le Roux, M. Nihemaiti, N. Nada, T. Khan, J-P. Croué. Pretreatment (oxidation, coagulation, ultrafiltration) of Red Sea water impacted by a Trichodesmium sp. algal bloom. International conference on Harmful Algal Blooms and desalination, Apr 2014, Muscat, Oman. 〈hal-01211747〉

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