The purpose of this project was to perform a careful evaluation of the technical and economic feasibility of advanced oxidation processes (AOPs) for methyl tertiary butyl ether (MTBE) removal. Specifically, the first objective of this project was to identify and fill data gaps related to the implementation and operation of AOPs with respect to MTBE removal. The second objective was to select and optimize the design of the most promising AOP(s) as a function of water quality parameters. The third objective was to determine conceptual-level engineering costs for these selected AOPs. The AOP technologies that were evaluated as part of this study included ozone/peroxide, continuous wave UV/peroxide, pulsed UV/peroxide, and E beam. The AOP technologies were compared with treatment costs, qualitative factors (e.g., technology reliability, flexibility), and influent and treated water quality considerations. Based on the comparative analysis, it was concluded that all the AOP technologies that were evaluated in this study are capable of removing MTBE at 95% or higher efficiencies. Ozone/peroxide and continuous UV/peroxide appear to be the most feasible technologies for AOP treatment of MTBE in drinking water sources. Originally published by AwwaRF for its subscribers in 2003
Low-pressure (LP) membrane use has increased dramatically over the last decade in response to more stringent pathogen-related drinking water regulations, water reclamation and the need for more effective reverse osmosis pretreatment, and from dramatically reduced membrane costs. More cost-effective and reliable operation of LP membrane systems is constrained, however, by fouling, in particular fouling by NOM. NOM fouling is poorly understood because of both the complexity and types of NOM that exists in natural sources and wastewater effluent and NOM-membrane interactions. This report is available as a Pay-Per-View item only. NOM exists in three primary forms (allochthonous, autochthonous, and effluent-derived), with a variety of components having differing fouling tendencies. LP membranes comprise hollow fibers of differing polymeric materials, with a range of properties that likewise influence fouling propensity. Fouling management strategies (backwash, air scrub, chemical cleaning) employed with LP membrane systems differ from supplier to supplier. This, combined with a number of the methods used to reduce NOM levels prior to membrane treatment (e.g., coagulation, clarification), further complicate the understanding of NOM fouling. The overall goal of this project was to investigate the specific contributions of the different types of natural organic matter (NOM) to microfiltration/ultrafiltration (MF/UF) fouling. The intent was to develop a surrogate test or index that could be used to predict NOM fouling at low cost through a combination of source water characterization and rapid bench-scale testing. The research incorporated bench-, pilot- and full-scale investigations. Testing was conducted with four source waters, selected to capture the fouling characteristics of the three primary types of NOM. Bench testing use a stirred, cell apparatus and three flat sheet membrane types, representing commercially dominant MF and UF hollow fiber membranes of the same polymer types. Hollow fiber bench testing used two PVDF and two PES membranes operated in both sequential and alternating filtration/backwash mode. Pilot testing included PVDF MF and UF and PES UF systems operated on three of the four source waters and incorporated a host of fouling management strategies. Full-scale investigations captured operating data from several plants having differing levels and types of NOM.
In the past, relatively minor attention has been focused on DON despite observations that both low and high molecular weight molecules containing organic nitrogen (e.g., simple amino acids, peptides, algal-derived humic substances) have been implicated as precursors of DBPs such as trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), nitromethanes, and nitrosamines like nitrosodimethylamine (NDMA). Nitrogenous organic matter has also been implicated as membrane foulant material. Dissolved organic carbon (DOC) is usually used as the surrogate for natural organic matter (NOM); NOM contains various ratios of carbon, oxygen, hydrogen, nitrogen, sulfur, and trace metals. While information exists on NOM removal through DOC measurements, it is unclear if DON is distributed equally among different molecular weight fractions. The project involved three phases. First, several pretreatment processes were evaluated to selectively remove inorganic nitrogen from samples, thus allowing more accurate and a potentially direct quantification of DON. Second, a survey of 28 water treatment plants was conducted during two different seasons to assess DON and related organic matter occurrence. Additional sampling of reclaimed wastewater systems was also conducted. Third, laboratory experiments were conducted with alum and cationic polymer coagulants, activated carbon, or disinfectants (free chlorine or monochloramine) to assess the ability to remove DON and understand its reactions with disinfectants.
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