Identifying Future Drinking Water Contaminants (1999) / Chapter Skim
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11 New and Emerging Drinking Water Treatment Technologies
11 New and Emerging Drinking Water Treatment Technologies
Pages 220-243
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From page 220... ...
For the first 75 years of this century, chemical clarification, granular media filtration, and chlorination were virtually the only treatment processes used in municipal water treatment. However, the past 20 years have seen a dramatic change in the water industry's approach to water treatment in which water utilities have started to seriously consider alternative treatment technologies to the traditional fiItration/chiorination treatment approach.
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From page 221... ...
TECHNOLOGIES EVALUATED A wide range of water treatment technologies have been developed or are currently in development. This paper focuses on technologies that can be applied in municipal water treatment plants.
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From page 222... ...
As a surface water treatment technology, low-pressure membrane filtration has several advantages over conventional filtration and chlorination. These include smaller waste stream, lower chemical usage, smaller footprint, greater pathogen reduction, no disinfection byproduct formation, and more automation.
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From page 223... ...
_ ~ 1 ~, , C LAYS S I LT AS lESTOS FIE iERS 1 . SAN n F S E PA RATIO N PROCESSES 1 | REVERSE | | OSMOSIS | NAN O- _ FILTRATION |ULTRAFILTRATION | l l CONVENTIONAL FILTRATION I PRQCESSES FIGURE ~ 1-1 Pore size ranges of various membranes.
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From page 224... ...
Today, membrane filtration is rapidly becoming accepted as a reliable water treatment technology. The California Department of Health Services has certified one MF membrane system for water treatment in the state, and has granted it 3-Iog Giardia removal credit and 0.5-Iog virus removal credit.
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From page 225... ...
, they are also capable of removing greater than 90 percent of natural New and Emerging Drinking Water Treatment Technologies 225
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From page 226... ...
Nevertheless, the Information Collection Rule includes data gathering on the applicability of NF membrane filtration for TOC removal from surface water sources. The majority of the data will be from bench-scale testing, which does not include information on long-term operational design and reliability, but some data will be obtained from pilot-testing programs.
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From page 227... ...
Several studies have been conducted to evaluate two-stage membrane systems for surface water treatment (Wiesner et al., 1994; Chellam et al., 1997; Kruithof et al., 1997; Vickers et al., 1997~. The results of these studies have clearly shown that ME or UP membranes are excellent pretreatment processes to NF or RO membranes and that the combined particulate removal and organic removal capabilities of this treatment scheme produce excellent water quality that complies with existing and forthcoming regulatory requirements.
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From page 228... ...
is now replacing conventional filtration for surface water treatment at several locations in the United States. High-pressure membrane filtration (both NF and RO)
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From page 229... ...
EPA has recently developed and published a guidance document for the application of W technology for surface water treatment (EPA, 1997a)
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From page 230... ...
However, it was not introduced to the municipal wastewater market until 1994. Currently, more than 270 MP-HI W systems are in operation, with 70 of them operating at municipal wastewater treatment plants.
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In fact, specific LP-LT W doses are listed in the Surface Water Treatment Rule (SWTR) Guidance Manual (EPA, 1991)
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No Significant Oxidation Capability One of the added benefits of disinfection with ozone, chlorine, or chlorine dioxide is the ability of each to also act as an oxidant for color, taste, and odor control. Unfortunately, disinfection with W irradiation does not provide this added benefit because W light, even with hydrogen peroxide addition, is not a strong oxidant.
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From page 233... ...
In this paper the application of each of the above processes in municipal water treatment is briefly discussed, and some of the challenges facing each process are presented. New and Emerging Drinking Water Treatment Technologies 233
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From page 234... ...
For the past 10 years, ozone disinfection systems have been designed to achieve low levels of Giardia inactivation. This required ozone contactors with "conventional" design criteria, including an average hydraulic retention time of ~ to 12 minutes and ozone doses ranging from 0.5 to 2 mg/L for an average water quality.
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From page 235... ...
Therefore, in an ozone-H2O2 process the goal is to increase the concentration of hydroxyl radicals, which is a stronger oxidizer than molecular ozone, and consequently rapidly reduce the concentration of molecular ozone. Therefore, hydrogen peroxide is added to an ozone process if it is used as an oxidation process but not as a disinfection process, which relies on the prevalence of a high concentration of molecular ozone.
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From page 236... ...
. ~ ~ ~ ~ ~ ~ ~7 Therefore, for this process to be used in drinking water treatment, either the process should be modified to utilize less hydrogen peroxide or a treatment process should be installed downstream to quench the hydrogen peroxide residual to acceptable levels (<0.5 mg/L)
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From page 237... ...
. For example, the capital cost of ~X ~ ~ ~, New and Emerging Drinking Water Treatment Technologies 237
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From page 238... ...
In addition, the waste stream contains a high concentration of the contaminant removed from the water (e.g., NO3-, HAsO4-, Pb2+, etch. The disposal of a waste stream containing these components is the primary obstacle to widespread implementation of {X technology at large-scale water treatment plants.
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From page 239... ...
New and Emerging Drinking Water Treatment Technologies 239
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From page 240... ...
Some of these technologies are membrane filtration, W irradiation, advanced oxidation, ion exchange, and biological filtration. These are certainly not the only technologies being considered by the water treatment industry.
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From page 241... ...
1991. Guidance Manual for Compliance with the Filtration and Disinfection Requirements for Public Water Systems Using Surface Water Sources.
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From page 242... ...
1987. The chemistry of water treatment processes involving ozone, hydrogen peroxide, and ultraviolet radiation.
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From page 243... ...
Journal of the American Water Works Association 87~3~:38. New and Emerging Drinking Water Treatment Technologies 243
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