Safe Water From Every Tap Improving Water Service to Small Communities (1997) / Chapter Skim
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4: Evaluating Technologies for Small Systems
4: Evaluating Technologies for Small Systems
Pages 132-152
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From page 132... ...
Before making decisions about treatment processes to employ and the extent of pilot testing that will be necessary, water system engineers will need to obtain information on raw water quality and desired treated water quality. Safe Drinking Water Act (SDWA)
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From page 133... ...
In other situations, however, available information on source water quality may provide convincing evidence that pilot testing for a particular treatment process is needed before a full-scale plant is installed. Thus, while current requirements for pilot testing of water treatment technologies lead to some duplication of effort and can be reduced, for certain combinations of treatment technologies and source waters, some degree of site-specific pilot testing always will be necessary to ensure that the equipment will perform adequately.
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From page 134... ...
An analogous situation would be if modifications were permitted in a standard EPA method for testing water quality, resulting in each state using a slightly different analytical approach for measuring water quality parameters such as turbidity and free chlorine concentration. ESTABLISHING A THIRD-PARTY CERTIFICATION PROGRAM State regulators would likely reduce requirements for extensive piloting of package technologies on a case-by-case basis if equipment manufacturers could receive credible third-party certification of their products.
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From page 135... ...
In late 1995, the EPA launched a program, the Environmental Technology Verification Program, to test a wide range of environmental technologies, including package water treatment plants. The EPA has provided funding for NSF International to develop equipment performance verification protocols and test plans for evaluation of water treatment package plants.
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From page 136... ...
Protocols for technology testing need to be sufficiently comprehensive to ensure that the total needs of small water systems are considered when testing is carried out. The obvious requirement for water treatment processes is to produce a water quality that meets SDWA requirements and customer preferences.
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From page 137... ...
Thus, the common language of testing protocols must be the language of the drinking water regulations. TECHNOLOGY-SPECIFIC TESTING REQUIREMENTS The degree to which test results from one location can be applied elsewhere, and therefore the extent to which third-party certification can reduce piloting requirements, depends on the technology and source water.
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From page 138... ...
Site-specific testing can range from bench-scale evaluations to operation of a pilot plant for a given time period. The extent of site-specific testing required depends on the amount of data available for the same or similar source waters.
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From page 139... ...
Pilot testing requirements for membranes used in surface water treatment are already being reduced in some states. For example, based on testing by the Metropolitan Water District of Southern California at one site on the Colorado River Aqueduct (Kostelecky et al., 1995)
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From page 140... ...
Therefore, site-specific testing requirements are less extensive for package plants employing conventional treatment trains than for those using newer technologies. When a package plant employs newer methods, such as upflow or downflow granular media beds to flocculate and remove particles before filtration, site-specific pilot testing is likely to be needed unless the range of raw water quality characteristics is well within the values for which the equipment has been demonstrated to the satisfaction of consultants and regulatory engineers.
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From page 141... ...
Consultants and regulatory engineers would benefit from the availability of more performance data that delineates the ability of this process to handle raw water turbidity. Effect of Raw Water Quality on Testing Requirements Regardless of the type of coagulation/filtration technology, some level of site-specific testing will always be required, at a minimum to determine appropriate coagulant doses, unless the identical system is treating water from the same source at another facility.
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From page 142... ...
Testing for Removal of Turbidity. Bench-scale jar testing is sufficient for determining the performance of package plants employing coagulation and conventional filtration if the quality of water to be treated falls within the range of water quality for which the package plants have already proven effective.
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From page 143... ...
TABLE 4-1 Water Quality Sampling and Analysis for Testing of a Conventional Coagulation/Filtration System Sampling Constituent Locations Frequency and Condition of Sampling Temperature R, F Once per day Alkalinity R, F Once per week and each time coagulation pH or alum dose is changed Aluminum R, F Once per week when alum is used as coagulant Iron and manganese R, F Once per week before reservoir turnover; after turnover, 2 or 3 times per day True color R, F Once per week when true color is 5 or less; once per day when true color is greater than 5 Algae R, F Once per week in raw water only for monitoring; twice per day during periods of elevated algae concentration Total organic carbon R, F Every week, coordinated with simulated distribution system testing for trihalomethanes and haloacetic acids Simulated distribution system EVALUATING TECHNOLOGIES FOR SMALL SYSTEMS trihalomethanes R, F Once per month Simulated distribution system haloacetic acids R, F Once per month pH R, C, F Once per 8 hours Turbidity R, F Measured continuously by flow-through turbidimeters; measure manually once per day to check each flow-through turbidimeter NOTE: Sampling locations: R, raw; C, coagulated water; F, filtered water. This plan was for a 9-month study at an actual site and included a reservoir turnover period.
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From page 144... ...
However, because DE filtration is commonly used without a clarification step ahead of filtration, source water quality limitations are somewhat stringent. Various grades of diatomaceous earth are available, ranging from coarse grades with low rates of head loss build-up to fine grades with substantial rates of head loss build-up.
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From page 145... ...
Construction of a slow sand filter without pilot plant testing and without prior slow sand filter operating experience on the water source in question could result in a small water system having a new filtration plant incapable of meeting one or more drinking water standards. The nature of slow sand filtration is such that after the design parameters of plant filtration rate, bed depth, and sand size have been set, there is little a plant operator can do to improve performance of a slow sand filter that does not produce water of a satisfactory quality.
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From page 146... ...
If lime softening of a surface water were undertaken by a small system, the requirements of the SWTR would have to be met. For a source water having stable quality, data from other lime softening plants treating source waters of the same or poorer quality, plus jar test data on the source in question, might suffice.
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From page 147... ...
Under this rule, small systems were to begin monitoring tap water for corrosion-related problems in July 1993; systems requiring corrosion control are to have treatment installed by January 1998. One alternative to performing a corrosion control study for a small system is to have a state drinking water regulator or other knowledgeable authority review the quality of the water involved and recommend pH or alkalinity adjustments, use of a corrosion-inhibiting chemical, or a combination of these strategies.
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From page 148... ...
CENTRALIZING DATA COLLECTION Currently, there is no one centralized data base or clearinghouse for information on the performance of drinking water treatment technologies. Several organizations have data bases or other sources of information on treatment technologies for small systems (see Box 4-2)
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From page 149... ...
• Surface water treatment technologies for which performance is linked to source water quality generally have more complex testing requirements than technologies whose performance is largely independent of water qual
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From page 150... ...
Among other services, the hotline provides information about water treatment and technology options, access to all AWWA resources, information on local resources, and an opportunity to network with others involved in small water systems. • National Drinking Water Clearinghouse (NDWC)
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From page 151... ...
applica tion of certain technologies on waters similar to a given source water. • The EPA should establish a standardized national data base for water treatment technology information by expanding the existing RESULTS data base at the National Drinking Water Clearinghouse.
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From page 152... ...
• The language of certification and testing should be standardized and should be the language of the Safe Drinking Water Act regulations. Data on raw and finished water quality should be collected in common units corresponding to the requirements of the SDWA.
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