Documents found
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2533.More information
AbstractThis review deals with advanced oxidation processes (AOP) for water and wastewater treatment. Most AOPs combine two or three chemical oxidants in order to produce hydroxyl radicals. These free radicals are species capable of oxidizing numerous complex organic, non-chemically oxidizable or difficulty oxidizable compounds. They efficiently react with carbon-carbon double bonds and attack the aromatic nucleus, which are prevalent features of refractory organic compounds. The AOPs can be divided into four groups: homogenous chemical oxidation processes (H2O2/Fe2+ and H2O2/O3), homogenous/heterogeneous photocatalytic processes (H2O2/UV, O3/UV and Fe2+/H2O2/UV; TiO2/UV), sonification oxidation processes (ultrasound oxidation) and electrochemical oxidation processes. The H2O2/Fe2+ system represents the most common and simplest AOP, which is often employed for the treatment of industrial effluents. However for drinking water treatment, the H2O2/O3 system is commonly used for pesticide removal. Electrochemical, photo-catalytic and sonification oxidation processes require fewer chemicals and are more easily automated than other AOPs. These technologies are effective in improving the treatment of industrial wastes, wastewater and drinking water, for example after their integration into a treatment plant or after their replacement of conventional processes that are found to less effectively eliminate specific organic and inorganic pollutants. The goal of this paper is to review published literature on the use of AOPs for water and wastewater treatment and the removal of refractory pollutants. Specifically, the objectives are: (i) to understand the theory and mechanisms of pollutant removal in AOPs, (ii) to provide a database for AOP applications, and (iii) to suggest new research directions for the development of AOPs.
Keywords: Procédé d'oxydation avancée, radicaux hydroxyles, composé organique réfractaire, eau potable, effluent industriel, Advanced oxidation process, hydroxyl radical, refractory organic compounds, drinking water, industrial wastewater
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2534.More information
Effluents from urban and industrial wastewater treatment plants contain organic (e.g., COD, BOD, total suspended solids, endocrine disrupting compounds), inorganic (e.g., phosphorus, ammonia nitrogen, nitrites and nitrates, metals) and microbial pollutants (e.g., bacteria, viruses, parasites), which are either directly discharged into the environment or reused for agricultural purposes. These wastewaters are often responsible for pollution of surface and groundwater (increasing the COD, colour and eutrophication of water, for example). In the context of finding solutions for water shortages, wastewaters are more and more frequently subjected to tertiary treatment for water reuse. The treatment of wastewater for reuse must yield water that meets specific quality criteria and is adapted to be reused as washing water, cooling water, process water, irrigation water or sprinkling water, among other uses. Conventional processes can be inappropriate, notably because of their inability to provide a consistently good quality of treated-water and because of the associated risk of microbial contamination. An alternate method can be the application of membrane bioreactors (MBR) for wastewater treatment and reuse. MBR are characterized by ease of operation, ease of automation, negligible equipment requirements for adding chemicals and their capacity to remove simultaneously organic, inorganic and microbial pollutants in the same reactor. This technology offers the possibility to simultaneously clarify and disinfect wastewaters without any risk of forming organochlorinated compounds. In this paper, MBR are first compared to conventional biological treatments, followed by a particular emphasis on the present state of knowledge about MBR, criteria of application and operating conditions that greatly influence the performance of these technologies. Recent developments in the modelling of the operating process and membrane fouling are also presented. Finally, industrial applications and operating and implementation costs are briefly discussed.
Keywords: Bioréacteur à membrane, biotraitement, membrane immergée, colmatage, polluant organique réfractaire, désinfection, polluant inorganique, eaux usées, Membrane bioreactor, biotreatment, immersed membrane, fouling, refractory organic pollutant, disinfection, inorganic pollutant, wastewater
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