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The F.B. Leopold Company, Inc.

W H I T E P A P E R

This article is the sole property of the F. B. Leopold Co., Inc. and is not to be reproduced or reprinted in whole or in part without the permission of the F. B. Leopold Co., Inc.

A Practical Guide to Sampling andTesting Filter Media

Thomas M. Getting, P.E., DEE, Filtration Product Manager Leonard Zukus, Operations Manager Christopher Ball, Application Engineers Manager F. B. Leopold Co., Inc.227 South Division StreetZelienople, Pennsylvania 16063

ABSTRACT

This paper presents a practical guide to obtaining a representative sample of filter media atthe point of manufacture and on the job site as well as providing insight into selecting a

media testing laboratory and the pitfalls of the various tests performed on those samples.The AWWA B100 Standard for Filtering Material provides a quantitative basis for samplingbut currently does not give procedural methods for obtaining representative samples. TheB100 Standard Committee is drafting methods for the next revision. Until then, this paper provides several methods for obtaining representative samples and details the practicesused to protect and identify them. The methods detailed are for sampling at the place of manufacture or at the project site. Sampling at the place of manufacture is recommended.

Once the samples have been obtained, they must be properly tested. Not all geologictesting laboratories are familiar with AWWA B100 media testing methods. This paper provides insight into selecting a testing facility that has the capability to test the samples inaccordance with the AWWA B100 testing methods that are sometimes nonstandard.Because some of the testing methods are nonstandard, the paper identifies those AWWA

mandated procedures that must be followed in order for the testing to conform to the AWWA B100 Standard. Some of these procedures can be identified in the test report as aquick check to ensure that the results are compliant.

The paper stresses the concept that a non-representative sample can provide erroneoustest results no matter how good the laboratory testing. Likewise, improper laboratorytesting technique can provide erroneous test results even with a good representativesample. To ensure accurate results, proper sampling and testing techniques must befollowed meticulously.

INTRODUCTION

The water filtration industry has generally accepted the American Water Works Association(AWWA) B100 Standard for Filtering Material as the law for describing filtration materialsused in municipal water filters. As the standard states “It is not a specification.” It does“…describe minimum requirements…” but does “…not contain all of the engineering andadministrative information normally contained in specifications. The AWWA standardsusually contain options that must be evaluated by the user of the standard… The use of

AWWA standards is entirely voluntary. AWWA standards are intended to represent aconsensus of the water supply industry that the product described will provide satisfactoryservice.” However, some specifications are written so that certain parameters or




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operations are to be performed in accordance with the AWWA B100 standard when thoseparameters or operations are not fully described in the standard. One such operation isthe sampling of semi-bulk containers on the jobsite. Furthermore, some operations areperformed in total disregard to the standard that can cause errors such as certain specialrequirements for testing filtering materials that are contained in the B100 Standard.

Section 5.3 states “If filter materials testing is not witnessed at the shipping point by thepurchaser, the material should be tested at the jobsite.” We recommend that filtering

materials be tested at the point of manufacture, as most manufacturers are equipped to dothe sampling and testing as a function of their quality control program. Furthermore, mostmanufacturers are thoroughly familiar with the B100 Standard requirements for samplingand testing. In fact some larger municipalities make periodic inspections of filter materialmanufacturers to qualify the manufacturer as an acceptable supplier. When filteringmaterial is produced, they then witness the sampling and identify the sampled materialusing tags or their distinctive mark. After testing acceptance, the material is shippeddirectly to the jobsite with no further testing required. This procedure decreases turnaround time for the project and eliminates all of the challenges associated with jobsitesampling and testing that we will now discuss.

This paper is being written to provide practical guidance in sampling filtering materials andto highlight the special provisions of the AWWA B100 standard that are in place of or

supersede the ASTM standards. This need has arisen from field experiences wherefiltering materials are specified to be sampled on site and tested by geologic testingfacilities that sometimes are not experienced in filtering material testing. In particular,Section 5: Verification in the B100 Standard states that sampling semi-bulk containers“across the cross section of the material being loaded” at the production site isrecommended. It also recommends that “If filter materials testing is not witnessed at theshipping point by the purchaser, the material should be tested at the jobsite. The materialshall be sampled in accordance with ASTM D 75….” However, ASTM D 75 StandardPractice for Sampling Aggregates does not provide a procedure for sampling semi-bulkcontainers on the jobsite which is being more frequently specified. ASTM D 75 providesfour methods of sampling which are Sampling from a Flowing Aggregate Stream (Bins or Belt Discharge), Sampling from the Conveyor Belt, Sampling from Stockpiles or Transportation Units, and Sampling from Roadway (Bases and Subbases) none of whichare suitable for sampling semi-bulk containers. In fact ASTM D 75 does state “Avoidsampling coarse aggregate or mixed coarse and fine aggregate from stockpiles or transportation units whenever possible, particularly when the sampling is done for determining aggregate properties that may be dependent upon the grading of the sample.”

ASTM D 75 also states “Sampling is equally important as the testing, and the sampler shalluse every precaution to obtain samples that will show the nature and conditions of thematerials which they represent.” In other words, the sample must be representative of thematerial and in all cases should be drawn from the entire cross section of thetransportation unit as materials tend to segregate while in transit.

Since the B100 Standard is widely used as an arbiter of filtering material, it should benoted that the “foreword is for information purposes only and is not a part of AWWA B100.”The B100 is not a law and to our knowledge has not been accepted as a law. However agood understanding and knowledge of the specific requirements of the standard are

necessary prior to specifying or modifying the standard in contract documents and prior toimplementing the standard in the field.




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SAMPLING The key in developing sound sampling programs for filtration media is strict adherence tothe Standards of AWWA B100 and the referenced ASTM Procedures. Whether testing isrequired as part of an on-site quality assurance program, or the result of projectspecifications, the sampling program must satisfy several procedural requirements. Poor sampling practices yield unrepresentative test reports that can consume an enormousamount of time from project personnel. Valuable resources are often spent analyzing

results that became invalid the moment the sampling plan failed to meet the samplingrequirements of the B100 Standard. The solution isn’t to hire an independent testing lab toassume the responsibility of sampling and testing. There are many cases in whichlaboratory and project personnel didn’t fully understand the complications of adhering toproper procedures. The process of media sampling and testing, including analyzing theresults is time consuming, often involving people from several different companies.Inexperience leads to re-sampling and re-testing that inflates project costs. Hastily grab-sampling a bag or two of each media type doesn’t constitute a sound sampling program. If the sampling portion fails to satisfy the standards of AWWA B100 the testing also fails tosatisfy the standards and they become invalid.

To help gain an understanding into media sampling and testing, worksheet (FBL-B100-96)presented in Figure 1 was developed to ensure the sampling and testing plan addresses

basic AWWA requirements. The bottom section of the worksheet can be used as areference guide in determining the sampling and testing procedures referenced in the B100Standard (the worksheet and reference guide are only applicable to AWWA B100-96edition). Contractors, Engineers, Plant Owners, and Media Manufacturer must understandthese requirements, and demand that sampling and testing procedures are properlyaddressed before sampling begins. At the end of the process each participant must agreethe samples and test results are representative. Without a consensus media quality issuescannot be resolved. From a manufacturing mindset, if the media is produced per specification and in accordance with the B100 Standard, the media must be sampled andtested on-site using procedures that likewise fulfill the requirements of the B100 Standard.The concept is to create a level playing field where media quality is evaluated usingapproved standard practices. Once on-site sampling and testing has been complete, per the guidelines of AWWA and ASTM, the results are valid and final. Sometimes it takes

several attempts to get it right, with each attempt becoming a costly learning experience.Hopefully the attached worksheet will help reduce some of the re-sampling, re-testing, andre-analyzing that happens everyday.

ON-SITE SAMPLING AND TESTING WORKSHEET

The first task undertaken in developing any on-site sampling program is an inventory of allthe media that requires testing. It is best to include as many types and sizes as possibleduring each round of sampling, as this will reduce the amount of nonproductive time spentby project and laboratory personnel. It is more effective to cover as much sampling aspossible each round than it is to set-up and reassemble personnel for additional samplingat a later time. In addition, some test procedures may take several days from preparation

to completion, making sample turnover time an important factor. This is especially truewhen installation schedules require results on a quick turn basis.

Inventory data must be complete and accurate, indicating exactly how many bags of eachmedia type and size are present along with bag weights. When project specificationsrequire anthracite, sand, and gravel to be tested on-site, it will be necessary to number each bag of anthracite beginning at #1 until all the bags of anthracite of that specific size




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have been numbered. Likewise, each bag of sand and gravel of similar size will benumbered, (beginning at #1) until all the bags of sand and gravel of that size arenumbered. This not only makes it easier to confirm inventory numbers, but it will also aidin determining which bags will be randomly sampled. After inventory is complete thesampling program can begin to be developed. The following sections refer to theWorksheet FBL-B100-96 in Figure 1.

Section 1: Type of Media

Determine the types of filter media or filter gravel that require testing. AWWA B100-96covers five different types of materials, anthracite, silica sand, high-density sand (classifiedas filter media), silica gravel, and high-density gravel (classified as filter gravel). Theworksheet is limited to these types of materials only.

Section 2: Media Size

From the inventory list indicate the size of media and/or gravel to be tested. For filter media the size is usually the effective size range and uniformity coefficient, i.e., ES 0.95mm x 1.05 mm and UC < 1.30, while gravel is sized using upper and lower size limits, i.e.,

3” x 7”.

Section 3: # of Bags in Lot

From the inventory list indicate the total number of bags of each specific type and size of media requiring testing. This information is critically important in developing the samplingprogram, as it determines the MINIMUM number of bags of a specific type and size mediathat must be sampled. These individual samples will ultimately be combined to produce asingle composite sample.

Section 4: # of Bags to Sample Sampling programs usually fail the requirements of AWWA by not sampling the proper number of bags per lot size. Grab-sampling a few media bags is often the norm when itcomes to on-site sampling. Although it is much easier, many people fail to understand theimpact of taking this approach. Grab sampling works both ways, it not only gives invalidunrepresentative test results that may indicate the media fails to meet projectspecifications, but it can also yield invalid unrepresentative results that indicate the mediameets the specifications. The composite sample must be representative of the lot, whichcan only be accomplished by being comprised of a minimum number of sub-samples takenfrom the lot.

Valid sampling programs comply with AWWA B100-96, Section 5.2, TABLE 4, Sampling of bagged media, which determines the minimum number of bags required to be sampled per the lot of media specific to type and size. Table 4 is reproduced in Figure 2 of this paper.It is a minimum number, and occasionally will require additional bags to be included in thesampling scheme in order to achieve the minimum weight limit for composite samples,(discussed later). In using Table 4, if a truckload of anthracite, i.e., E.S. 0.95 mm x 1.05mm UC < 1.30, is comprised of 18 superbags @ 2500# each, a minimum of five (5)superbags would need to be randomly sampled and combined to produce one (1)

composite sample representing the entire truckload of material. If the same truck weredelivering a load of anthracite in cubic foot bags @ 50# each, the number of bags to besampled increases to eighty (80), (since the total number of bags on the truck is 900). Aword of advice about sampling and testing cubic foot bags, perform the sampling andtesting at the media manufacturers’ facility during production, it is much less messy and theintegrity of the bags is not compromised.




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Section 5: Individual Bag #s to Sample

Once the number of bags to sample has been determined it will be necessary to identifythe actual bag numbers to sample. During the process of taking inventory it wassuggested that each bag specific to a type and size be numbered starting at 1, thesenumbers will be used to ensure that superbag selection is truly random. Picking five (5)bag numbers arbitrarily doesn't make them random; some bias exists.

A method of determining random bag numbers for sampling can be found in ASTM D3665, Practice for Random Sampling of Construction Materials, referenced in ASTM D 75Standard Practice for Sampling Aggregates. Both of these ASTM procedures along with

ASTM C 702 Standard Practice for Reducing Samples of Aggregate to Testing Size arerequired reading for any personnel involved with sampling, testing, or review.

To determine which bags to sample refer to ASTM D 3665 and find TABLE 1, Table of Random Numbers reproduced in Figure 3 of this paper. Earlier it was determined that aminimum of five (5) superbags required sampling from the truckload of anthracitesuperbags. Laying both pages of TABLE 1 on a flat surface, randomly, with a pointer,place a mark in the body of the table. The number directly under the mark is read, for thisexample the number is 0.280 indicating that the first bag # will be determined by a number in row # 28. The same procedure is repeated, randomly placing another mark on the table

and record that number, for this example the number is 0.799, this indicates that the bag #we are looking for is in column #7. The number in column 7, row 28, of Table 1 of ASTM D3665 is 0.660. The process is repeated, row and column, until at least five (5) numbershave been determined, (sometimes it is better to pick a few additional numbers just in caseproblems of duplicate bag numbers arise later). The five random numbers are each thenmultiplied by the number of bags (n) on the truck, (or in the lot). Since the number of bagsare 18, we multiply 18 X 0.660 and the bag # we are after is 11.88 rounded to bag #12.Completing the process our bag #’s are 12, 15, 8, 10, and 4. Should the same bag # berepeated twice, disregard the number and use TABLE 1 to determine an additional number if you haven’t determined extras. Although the process may seem complicated, it is easier after reading the whole of ASTM D 3665; (the process of establishing bag numbers takesless than 5 minutes from start to finish).

The act of sampling begins after the bags have been identified and located. There are avariety of sampling methods used in recovering samples from bagged filter media whichwill be described later. Regardless of the method used, each bag must be sampled usingthe same method and procedures; all samples will be weighted equally. When samplingtubes are used it is important to recover the sample from a cross-section of each bag whena sample is recovered. Individual samples should be tagged and bagged until it isdetermined that the combined weight of the individual samples can produce a compositesample of sufficient size to fulfill the requirements of AWWA.

Section 6: Sample ID #

The composite sample must meet the minimum weight limits defined in AWWA B100-96Section 5.2, Table 3: Minimum size of composite sample as reproduced in Figure 4.Occasionally the weight of the samples removed from the superbags, when combined into

the composite sample will fail to meet the limit. If each sample removed from theanthracite superbags in the example weighted 1 pound, the composite sample wouldweigh 5 pounds. Although it may be of adequate size for testing purposes, it fails to meeta requirement of B100. In the example Table 3 indicates that the minimum size of thecomposite sample is 10 lbs. (4.5 kg) since the maximum size of particles in the sample aresmaller than 3/8”. The weight of the composite sample must be increased by an additional5 lbs., either by randomly determining additional bags to sample, or by doubling the size of




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the samples recovered from each of the original five bags. Again, care must be taken toensure that individual sample size is roughly the same; big differences can skew testresults.

Once the individual samples have been combined to form the composite sample, and thecomposite meets the weight requirements of AWWA B100-96 TABLE 3, the sample can bereduced. Although sampling anthracite and sand generally produces composite samplesof manageable size, quite often and especially with gravels, the composite sample will

need to be reduced for handling purposes. When reduction is needed it is accomplishedby one of the methods recognized in ASTM C 702, Standard Practice for ReducingSamples of Aggregate to Testing Size. The characteristic determining how the compositesample will be reduced is the moisture condition of the sample. If the sample has visiblemoisture on the surface it is reduced using the cone and quartering method of reduction, if the composite is dry, it is reduced using a mechanical splitter or riffle so as not to crushindividual grains. When reducing samples by the cone and quartering method make surethe sample is handled in a manner that will not cause the sample to crush during therepeated quartering process. A good practice when reducing composite samples to testingsize is to create splits of the sample that can be archived for later use if problems occur during testing.

When the composite sample has been reduced to a manageable size it should be placed

in a clean, airtight container and sealed to prevent contamination. The container must beaffixed with a sample ID number, initial weight, and the signature of the person(s)responsible for verifying the sampling program. Include as much information in the sampleID number as possible and make sure that the sampling information is forwarded to thetesting laboratory along with the sample.

SAMPLING METHODS

Some materials and transportation containers are not easily sampled. For instance, cubicfoot bags can be opened, sampled and resealed. One method is to insert a small grainthief into the bag and reseal the bag using tape. However, this does compromise theintegrity of the bag and subsequent handling may affect the sealing method. Also, the

grain thief is not suitable for gravel material in cubic foot sacks. These samples may bereduced using a mechanical splitter also known as a riffler or the cone and quarter method;both referenced in ASTM C 702. The cone and quarter method involves placing thematerial on a hard clean surface, mixing the material by forming cones at least three times,flattening the material, dividing the material into quarters, bagging two opposite quarters,and repeating until the appropriate sample size has been obtained. All of the precedingmethods are logistically difficult at the jobsite due to the number of bags involved.

Dry anthracite and granular activated carbon have been successfully sampled from semi-bulk containers using a brass seed sampler. The brass seed sampler actually consists of two nested tubes, which contain slotted openings. One end of each tube is pointed andthe other end is open. The inside tube is rotated so that the slots are not aligned and thesampler is inserted into the semi-bulk container to refusal but not through the bottom or sides of the container. The inside tube is rotated so that the slots align and both tubeopenings align to allow the sample to flow into the sampler. The inside tube is againrotated so that the slots are not aligned and the sampler is removed from the container.The sample is poured from the open end of the sampler into the sample storage container.Care must be exercised to not force the sampler into the container being sampledespecially with a hammer nor to force rotating the tubes as this may cause attrition of the




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material being sampled. Figure 5 presents a semi-bulk container of anthracite beingsampled using a brass seed sampler along with samplers in the open and closed positions.

The brass sampler has not been found to be suitable for sampling silica gravel, silica sand,high-density gravel and high-density sand in semi-bulk containers. Generally it is notpossible to insert the brass sampler into these materials without applying substantial forceand the tubes tend to bind both on opening and closing as these materials jam the tubes.

Also, some of the larger gravel will not flow through the slotted openings. Alternative

methods for sampling these materials in semi-bulk containers must be devised as the B100and the ASTM standards do not describe any sampling techniques. Four methods havebeen used and have met with varying success. They are, in decreasing order of accuracy:

1. Crosscut sampling from a flowing stream out of a hopper.2. Emptying the bags and cone and quartering per ASTM C 702 as described above.3. Removing a portion of the material and obtaining a sample of the center of the bag.4. Surface sampling off the top of the bag will not yield a representative sample and is

not recommended.

Figure 6 presents the apparatus and equipment necessary to obtain a flowing stream froma semi-bulk container of material. It consists of a support structure, a hopper large enoughto contain one semi-bulk container, a flow control valve such as this slide gate, a method tosupport the semi-bulk container to be filled such as a fork lift, and sampling devices such

as pans or buckets. The container to be sampled is deposited into the hopper and thesame container is positioned below the slide gate. On cue the slide gate is opened andsamples are taken through the flowing stream. The samples are deposited into another container for compositing and reduction per ASTM C 702. This method of sampling isrecommended only for those projects that have a large number of containers to sampleand production sampling was not performed. The time required to perform this procedureand expense tend to be prohibitive. It is recommended that the third method describedabove be employed where a portion of the material is removed from the container and asample is obtained. The least desirable method is to sample the top of the container, asthis usually does not provide a representative sample.

In any event, as the ASTM D 75 states, it is the responsibility of the sampler to obtain arepresentative sample of the material to be tested. No matter how precise the tests are

performed on the sample obtained, if the sample is not representative, the test results willbe in error. Conversely, even though the sample is representative, if the tests are notperformed correctly the results can still be in error.

SAMPLE TESTING

To ensure reliable, repeatable results the B100 Standard bases most of the filteringmaterial tests on existing ASTM standard tests. However, in some cases the B100Standard makes significant modifications that can effect the results if the technicianperforming the testing is unaware. Prior to procuring the services of a testing laboratory,the testing technician should be asked whether they are experienced in AWWA B100filtering material testing. If not, they should be cautioned that not all of the tests follow the

ASTM standards exactly. If the testing facility does not have a copy of the B100 standard,they should be instructed to obtain a copy and review it before the samples arrive. In somecases, additional testing equipment may need to be procured. Usually they will have toobtain sieves in order to complete a proper B100 sieve stack. The following is a discussionof each of the major Test Procedures described in Section 5.3 of the B100 Standard:




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5.3.1 Acid Solubility

The acid solubility test is unique to the B100 Standard and the test in its entirety isdescribed in the standard. Prior editions of the B100 Standard required the hydrochloricacid concentration to be 20% and the sample had to stand for 24 hours, but the mostrecent edition uses a 1:1 ratio and a time limit of 30 minutes after effervescence ceases.This has decreased the time necessary to perform the test.

5.3.2 Gravel Shape

Again the gravel shape test is unique to the B100 standard and is described in its entiretyin the standard. Of all the B100 tests, this is one of the most subjective. It requires theobserver to estimate and identify various characteristics. The first is fractured faces whichare “defined as a surface surrounded by sharp edges, such as those produced bycrushing, that occupy more than approximately 10 percent of the total surface area of theparticle. This is intended to exclude a surface with small nicks and chips from classificationas a fractured face.” Section 4.1.2.1.3 allows no more than 25% by dry weight to havemore than one fractured face. This definition not only requires the observer to estimatewhat constitutes 10% of the total area, but also whether the face is surrounded by sharpedges. Some flat surfaces that do not have sharp edges have been erroneously identifiedas fractured faces.

The other gravel shape test is shape determination. The shape is defined as “the ratio of the longest axis to the shortest axis of the circumscribing rectangular prism for a piece of gravel shall be determined using a caliper or a proportional divider.” Less subjective, theobserver has the use of a mechanical device and only has to determine the circumscribingprism.

5.3.3 Specific Gravity

The B100 utilizes both the ASTM C 127 Standard Test Method for Specific Gravity and Adsorption of Coarse Aggregate and the ASTM C 128 Standard Test Method for SpecificGravity and Absorption of Fine Aggregate. It also allows the use of the Noble Large

Aggregate Test for silica gravel, but the test is unique to the standard and requires specialequipment which most laboratories may not have. However, it is less complicated andfaster to perform than the ASTM C 127. Currently, the B100 Committee is considering asimilar alternative test to be performed on anthracite if it can be shown to be as accurateand repeatable as the Noble Large Aggregate Test was shown for gravel.

The ASTM C 127 specific gravity test for silica gravel is reported as a saturated surface dryspecific gravity. Inherent with this test and the ASTM C 128 is the determination as towhen the material has been dried, usually using towels to remove the excess moisture, toa saturated surface dry condition. With experience most technicians are able to providerepeatable results. Another aspect of the ASTM C 127 test is that it is intended for materialretained on a No. 4 (4.75 mm) sieve. Since many gravel gradations include a barrier layer that is 1/8” x No.12 (3.175 mm x 1.70 mm) and a support layer of ¼” x 1/8” (6.35 mm x3.175 mm) these tests need to be handled differently. The 1/8” x No. 12 should be testedin accordance with ASTM C 128 and the ¼” x 1/8” should be split between ASTM C 127 for

the larger fraction and ASTM C 128 for the smaller fraction.

All other materials including silica sand are tested using the ASTM C 128 and reported asapparent specific gravity. The procedure empirically determines the specific gravity of anaggregate or media on a bulk saturated surface dry basis, and the absorption value in thebulk saturated surface dry state. These two values are then used to mathematicallydetermine the specific gravity of the media in both an apparent and bulk basis. The ASTMC 128 states that apparent specific gravity “pertains to the relative density of the solid




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materials making up the constituent particles not including the pore space within theparticle that is accessible to water.” It represents the specific gravity of the solid denseanthracite, less the pore space. The pore space within anthracite, determined byabsorption, is as much as eight times higher than that of silica or garnet materials. Thesehigher absorption values widen the difference in specific gravity between the apparent andbulk saturated surface dry basis. In the case of anthracite a more accurate or true value of specific gravity may be bulk (saturated surface dry), since it represents the specific gravityof the media particles when the pore spaces are saturated with water, as they are when in

a filter.

5.3.4 Sieve Analysis

The most specified and possibly the most controversial test is the sieve analysis alsoknown as gradation analysis. This test is performed in accordance with the ASTM C 136Standard Test Method for Sieve Analysis of Fine and Coarse Aggregates with significantmodifications stipulated by the B100. The most significant modifications are the samplesize, machine-shaking times, sieve calibration, and sieve stack. The purpose of the sieveanalysis for fine filtering material such silica sand, garnet sand, and anthracite is toproduce a plot of the results on semi-log paper to obtain the effective size and uniformitycoefficient of the tested material. For a further explanation of these criteria, refer to theB100 Standard. The purpose of the sieve analysis for gravel is to obtain the percent over

and under size of the tested material. For instance the percent greater than ¾” and thepercent less than ½” for a ¾” x½” gravel. The minimum sample size is listed in Table 6 (Minimum sample size for sieve analysis) of the B100 Standard and reproduced as Figure 7 in this paper. However, for anthracitesieve analysis we find that using much more than the minimum sample size causes toomuch anthracite to accumulate on individual sieves and can cause blinding of the sieve. If the sieve blinds it may not allow all of the smaller particles to pass leading to erroneousresults. The reason for this is the difference in bulk density between silica / high-densitymaterial and anthracite. The bulk density of anthracite is 50 pounds /cubic foot versus 100pounds / cubic foot for silica materials and up to 300 pounds /cubic foot for high-densitymaterial. That means that the same weight sample of anthracite has twice the volume of the same weight of a silica material. We recommend that the anthracite sample size for sieving be no more than 150 grams. This anthracite sample size limit is also beingconsidered in the next update of the B100 Standard.

A significant modification of the ASTM C 136 is the required machine shaking times. The

B100 Standard states “Generally, sieves require machine shaking times of 10 min. ± 0.5

min. for sand and gravel and 5 min. ± 0.5 min. for anthracite.” This is in contrast to the ASTM C 136 requirement of “Continue sieving for a sufficient period and in such manner that, after completion 1 mass % of the residue on any individual sieve will pass that sieveduring 1 min. of continuous hand sieving…” Most testing laboratories are unaware of thisB100 Standard requirement and excessive sieving can reduce the particle sizes. TheB100 Standard states that “Care shall be taken to avoid breaking anthracite particles whensieving.”

Calibration of the sieves used can be critical in obtaining accurate results. The B100

requires that “All standard sieves used for testing filter materials shall conform to thetolerances required in ASTM E 11 Standard Specification for Wire Cloth and Sieves for Testing Purposes. If compliance to specifications arise when nominal sieve openings areused, standard reference materials (glass spheres) certified by the National Bureau of Standards shall be used in accordance with their calibration procedure to accuratelydetermine the effective opening size of each sieve.” In fact when sieving anthracite, silicasand and high density sand, most laboratories use glass sphere calibrated sieves because




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the effective size tolerances of these filter materials are 0.001 mm or 0.00004 inches. Thatis the difference between a filtering material being accepted or rejected. If glass spherecalibration is not available, the B100 allows replotting the data “using both the maximumand minimum permissible variation of average opening from the standard sievedesignation as shown in Table 1, column 4 of ASTM E 11” also reproduced in Appendix Bof the B100 Standard.

Most testing laboratories will list the effective sieve size as derived from the nominal sieve

size opening. The effective sieve size is the average sieve opening determined by glasssphere calibration. The nominal size opening is the nominal dimension listed in ASTM E11, Table 1. If the reported sieve opening varies from the nominal sieve opening, thesieves usually have been glass sphere calibrated. If the nominal sieve size is listed, it isusually assumed that the sieves are not glass sphere calibrated, but still comply with the

ASTM E 11 tolerances. Sieves that do not meet the ASTM E 11 tolerances must not beused. Laboratories and manufacturers experienced in B100 filtering material testing willusually maintain a separate set of glass sphere calibrated sieves that are used exclusivelyfor testing filtering material and maintain other sieves for their other work. If in doubt askthe testing laboratory if their sieves are glass sphere calibrated. If they are not glasssphere calibrated, questions of calibration are relegated to replotting the results using themaximum and minimum permissible variation of average opening from the ASTM E 11,Table 1 standard sieve designation.

The B100 Standard requires that “To avoid excessive interpolation when determining theeffective size… and the D60… the sieves used on a particular sieve analysis shall haveopenings such that the ratio between adjacent sizes is the fourth root of 2, or 1.1892.” Inother words, the sieves should be in consecutive order as listed in the B100 Appendix, i.e.No. 10, No. 8, No. 6, No. 5, etc. Skipping one sieve size can drastically effect the effectivesize and uniformity coefficient that will provide erroneous results especially with thetolerances described above. It is always prudent to check with the testing laboratory prior to delivering the samples to determine if they have on site calibrated, consecutive sievesizes in the range of the material being tested and to prevent delay of receiving accurateresults. The other stipulation by the B100 is that “The sieves shall be chosen so that thenominal opening of only one sieve is smaller than the smallest effective size so that thegreatest range of particle size distribution can be measured in one standard nest of sixsieves.” This is to ensure that the sieve stack is limited to the opening sizes of mostimportance to the gradation plot.

5.3.4.6 Mohs’ scale of hardness.

The B100 states that “No standard test method has been found; however, all commerciallaboratories follow the same procedure.” This statement is very ambiguous and makes thisa very subjective test. The B100 Committee will be reviewing a test method to make itmore objective. Most testers use various types of known hardness geologic, flat facedrocks, to determine the hardness of filtering materials. Usually samples of the filteringmaterial are mounted on sticks. The mounted samples are used to scratch the rocksamples of increasing hardness, using a firm, consistent pressure, until the filteringmaterial can not longer scratch the rock samples. The last scratched geologic rock of say75% of the sample filtering material is then used as the final Moh number. For instance if a

majority of the filtering material last scratches a 3.0 Moh hardness calcite, the material issaid to have a Moh hardness greater than 3.0. The experience of the tester is important inselecting the samples, determining the edge of the sample to be used, maintaining aconsistent pressure and knowing when the sample is scratching the geologic rock or whenthe sample is crushing under pressure. Moh’s hardness is truly a subjective test with nopresent standard for guidance.




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CONCLUSION

The AWWA B100 Standard for Filtering Material is the standard recognized throughout thewater industry and the world as the document that best describes quality filtering material.More often than not the B100 is specified in water engineering documents as the minimumrequirements for supplying filtering material. Furthermore, some engineering documentswhile specifying the minimum B100 standards modify these either by making them morestringent or by adding additional requirements. It is recommended that when modifying the

B100 requirements, one should be intimately familiar with the basis of the standard as wellas the effect the modification will have on the filtering material and the ability of amanufacturer to supply that material.

We recommend that if at all possible sampling and testing of filtering material should bewitnessed at the point of manufacture. Most manufacturers have the facilities to sampleand test the materials on site and are experienced in the AWWA B100 requirements. If it isnot possible to witness the sampling and testing at the point of manufacture, themanufacturer’s sampling and testing is not adequate, or the filtering materials must besampled and tested on site, a detailed sampling and testing program must be organized.The program must adhere to the B100 requirements as outlined before.

Sampling a filtering material is a critical process that could effect the overall results of a

testing program. Care must be exercised that the sample is representative of the materialbeing sampled. Some materials such as anthracite and GAC are readily sampled using abrass sampler, but most silica and high density material is difficult to sample and adequatemethods are not described in the standards. Prior to specifying or implementing asampling program, the actual logistics must be adequately planned to obtain representativesamples or the samples produced could be inaccurate.

Prior to obtaining the samples, testing laboratories should be interviewed before one isretained. During the interview it should be determined if the laboratory is experienced in

AWWA B100 testing. If a laboratory that is experienced in AWWA B100 testing can not befound, the selected laboratory should procure the appropriate standards and thoroughlyfamiliarize themselves with the modifications contained in the B100 Standard. After receiving a test report on filtering materials the result should be checked to determine if the

proper B100 procedures were followed. If not, the samples should be re-tested using B100methods. If there is any doubt about the results received, both the sampling and testingshould be investigated to ensure that a representative sample of the filtering material wasobtained and that AWWA B100 methods were used. If after an investigation of themethods used confirms that all procedures were in compliance with all standards, includingthe AWWA B100 and the appropriate ASTM standards, only then can the material beconsidered either compliant or not compliant with the AWWA B100 Standard for FilteringMaterial.

REFERENCES

“ASTM C 127 Standard Test Method for Specific Gravity and Adsorption of Coarse

Aggregate,” American Society for Testing and Materials“ASTM C 128 Standard Test Method for Specific Gravity and Adsorption of Fine Aggregate,” American Society for Testing and Materials“ASTM C 136 Standard Test Method for Sieve Analysis of Fine and Coarse Aggregate,”

American Society for Testing and Materials“ASTM C 702 Standard Practice for Reducing Samples of Aggregate to Testing Size,”

American Society for Testing and Materials




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“ASTM D 75 Standard Practice for Sampling Aggregate,” American Society for Testing and Materials“ASTM D 3665 Practice for Random Sampling of Construction Materials,” AmericanSociety for Testing and Materials“ASTM E 11 Standard Specification for Wire Cloth and Sieves for Testing Purposes,”

American Society for Testing and Materials“Standard for Filtering Material, B100-96,” American Water Works Association

ACKNOWLEDGMENTS

W. Kirk Corliss, Jr., Gannett Fleming, Inc.Raymond Yem, ATAL Engineering LTDSamuel Ricci, Sr., Ricci Brothers Sand Co., Inc.




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F.B. Leopold Co., Inc. Engi neered Filter Media® Division

Media Site Sampling WorksheetForm:FBL-B100-96

Job Name: Location: Contract # Date:

Engineer: Contact: Phone:

Contractor: Contact: Phone:

City: Contact: Phone:

FILTERING MATERIALS SAMPLING AND TESTING FIELD SUMMARY

Sampling Testing

Section

1

Type of

Media

Section

2

Media

Size

Section:

3

# of Bags

in Lot

Section:

4

# of Bags to

Sample¹

Section:

5

Individual Bag

#’s to Sample ²

Section

6

Sample

ID #

Section:

7

SizingES/UC

% over %under

Section:

8

Specific

Gravity

Section:

9

Acid Sol.

Section:

10

Moh

Hardness

Section:

11

Flat &

Elongated

Section:

12

Fractured

Faces

Sectio13

Othe

Anthracite (A), Sand (S), Support Gravel (SG), High Density Sand (HD-S), High Density Gravel (HD-G)

¹ AWWA B-100-96, TABLE C, pg. 24 ² ASTM D 3665 Random SamplingTESTING PROCEDURES REFERENCE TABLE

Anthracite Silica Sand HD – Sand Silica Gravel HD Gravel

AWWA ASTM AWWA ASTM AWWA ASTM AWWA ASTM AWWA ASTM

Practice for Sampling D 75 D 75 D 75 D 75 D 75Reducing Field Samples C 702 C 702 C 702 C 702 C 702

Random Sampling D 3665 D 3665 D 3665 D 3665 D 3665

Sieve Analysis (Sizing)Effective Size / UC

Sec. 5.3.4Sec 5.3.4.3

C 136E 11

Sec. 5.3.4Sec. 5.3.4.3

C 136E 11

Sec. 5.3.4Sec. 5.3.4.3

C 136E 11

Sec. 5.3.4 C 136E 11

Sec. 5.3.4 C 136E 11

Specific Gravity Sec. 5.3.3 C 128 Sec. 5.3.3 C 128 Sec. 5.3.3 C 128Sec. 5.3.3Sec. 5.3.3.1 C 127 Sec. 5.3.3 C 128

Acid Solubility Sec. 5.3.1 Sec. 5.3.1 Sec. 5.3.1 Sec. 5.3.1 Sec. 5.3.1

Moh Hardness Sec. 5.3.4.6 N/A Sec. 5.3.4.6 Sec. 5.3.4.6 N/A

Shape / Flat & Elongated N/A N/A N/A Sec 5.3.2.2 Sec 5.3.2.2

Fractured faces N/A N/A N/A Sec. 5.3.2.1 Sec. 5.3.2.1

Clay, Dust, Micaceous and OrganicMatter

C 117C 40

C 117C 40

C 177C 40

Figure 1




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Table 4+ Sampling of bagged media*

Lot Size Minimum Sample Sizes(number of bags shipped) (number of bags)

2-8 29-15 316-25 526-50 8

51-90 1391-150 20151-280 32281-500 50501-1,200 801,201-3,200 1253,201-10,000 20010,001-35,000 31535,001-150,000 500

*Refer to military Standard MIL-STD-105D (1963)

+(Table 4 is reproduced from the AWWA B100-96 Standard for Filtering Material)

Figure 2




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Figure 3




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Figure 3 continued: Reproduced from ASTM C3655 Practice for Random Sampling of Construction Materials.

Table 3+ Minimum size of composite sample

Maximum Size of MinimumParticle in Sample Sample SizeMm (in.) kg (lb)63.0 (2 ½) 45.0 (100)37.5 (1 ½) 32.0 (70)25.4 (1) 23.0 (50)

19.0 (3/4) 14.0 (30)12.5 (1/2) 9.0 (20)9.5 (3/8) and smaller 4.5 (10)

+(Reproduced from AWWA B100-96 Standard for filtering material)

Figure 4




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Figure 5: Sampling an anthracite semi-bulk container with a brass sampler tube. Brass sampling tube.

Figure 6: Apparatus for sampling a semi-bulk container




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Table 6+ Minimum sample size for sieve analysis

Maximum Size of MinimumParticle in Sample Sample WeightMm (in.) kg (lb)63.0 (2 ½) 23.0 (50)37.5 (1 ½) 16.0 (35)25.4 (1) 11.0 (25)

19.0 (3/4) 6.8 (15)12.5 (1/2) 4.5 (10)9.5 (3/8) 2.3 (5)

No. 4 (4.75) 500.0 gNo. 8 (2.36) 100.0 g

+ (Reproduced from AWWA B100-96 Standard for Filtering Material)

Figure 7

arena. muestreo y pruebas. leopold. pgstfmpdf

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