CEI Anthracite

CEI Anthracite manufactures high quality, dry and low uniformity coefficient anthracite filter media.

CEI Anthracite’s <1.3 uniformity coefficient can provide many benefits in granular bed filters, including:

Increased plant capacity by the use of higher filtration rates
Lower backwash rates in dual- and tri-media filters
Better production efficiency due to longer filter cycles at higher filtration rates
State-of-the-art sizing plant to guarantee your specifications… ensuring complete production control and accurate processing.
Automated sieve analyzer… assures consistent product quality permitting precise control of both the raw material and finished product.
Automated high-speed bagging equipment… offering optional packaging in either one (1) cubic foot bags (or) one ton high-strength woven polypropylene fabric bags for fast and easy handling.

CEI Anthracite offers a customized comparative analysis between the uniformity coefficient of <1.3 and the traditional higher uniformity coefficients. The analysis summarizes the annual savings realized from reduced fresh water use.

CEI Anthracite can manufacture anthracite with a Uniformity Coefficient of <1.3.

Technical Info

ASTM C136 standard test method for sieve analysis of fine and coarse aggregates defines the sieve procedure to determine effective size and uniformity coefficient.

Generally sieves require machine shaking times of 10 min (+/-0.5 min) for sand or gravel and 5 min (+/-0.5 min) for anthracite. All standard sieves used for testing filter media should conform to the tolerances defined in ASTM E11.

Terms & Definitions

EFFECTIVE SIZE – The opening that will pass 10% (by dry wt.) of a representative sample of the filter material;

Example: distribution shows 12.2% passing #18 sieve (1.00 mm) therefore the sample has an effective size (d10) of 0.99 mm.

UNIFORMITY COEFFICIENT – A ratio calculated as the size opening that will just pass 60% (by dry wt.) of a representative sample of the filter material divided by the size opening that will just pass 10% (by dry wt.) of the same sample.

Example: distribution shows 49.8 passing #16 sieve (1.18 mm) divided by the size opening that will just pass 10%.
All Products Exceed AWWA Standards. NSF Approved.

Question & Answer

What benefits can we expect from converting our filters from single-sand to a dual-media (sand and anthracite) system?

Anthracite angularity results in a large void ratio and allows more solids holding capacity than rounded sands – yielding a consistently better filtrate quality throughout a filter run. The Dual-Media System more fully utilizes the entire bed for storage of filtered solids since water passing through a Dual-Media filter contacts the coarser anthracite offering ample void area to effect removal and storage of the suspended solids. The Dual-Media System also requires a lower backwash rate to achieve fluidization with filtration rate of 3-4 time higher than those of rapid sand filters.

What additional benefits can we expect from using a uniformity coefficient of <1.3 on our Filter Anthracite in the Dual-Media System?

The lower uniformity coefficient anthracite has less oversized and undersized particles resulting in a highly uniform bed. The low uniformity coefficient anthracite coal requires much lower backwash rates, which results in substantial savings to the owner due to annual wash water reductions.

How can we determine when we need to replace our media system?

Depending upon many factors including the operation and maintenance of related filter components, the media system typically requires replacement every 15-20 years. Media has a tendency to round-off from attrition and lose it effectiveness. The media also can increase in size due to the agglomeration of chemicals and polymers adhering to the media. CEI Anthracite can provide filter evaluations to determine solutions for your filter maintenance needs.

Backwash rates

Lower Backwash Rates with CEI Anthracite

DUAL-MEDIA

Dual-Media filters (anthracite on top of sand) must include a fluidizing backwash rate at some time before the end of the water backwash. This ensures that the two layers are restratified into their normal layers of anthracite on top and sand below.

The advantages of CEI Anthracite for dual-media filters is that the ratio of the coarser grain size of the anthracite to the effective size (e.g. d90/d10), is lower, and therefore the required backwash rate for fluidization is considerably lower than for other high uniformity coefficient anthracites. Consider the following example which assumes a typical log-normal size distribution.

*Approximate minimum fluidization velocity based on water at 10° C (50° F) with anthracite density = 1.65 g/cm3.

Furthermore, with CEI Anthracite, there is less stratification of the smaller sized grains on top of a layer and larger sized grains at the bottom. There is more tendency for the carious-sized grains to mix, rather than to stratify. This is particularly evident if the d90/d10 ration is 1.3 or less for the anthracite.

TRI-MEDIA

CEI Anthracite would provide similar advantages in lower backwash rates for tri-media beds using low uniformity coefficient CEI Anthracite. This is a particular advantage for those designers who prefer to minimize the extent of mixing between adjacent layers in tri-media filters.

MONO-MEDIA

CEI Anthracite also benefits mono-media filters with coarse grain size that are usually backwashed with air and water simultaneously below fluidization velocity. During this sub-fluidized backwash, the media migrates slowly from top to bottom and from bottom to top assisting in the release of solids from the bed. Such migration of media is encouraged by provision of low uniformity coefficient media.

All Products Exceed AWWA Standards. NSF Approved.

Media Selection

Media Selection (L/D Ratio)

No ideal media configuration applies to all water sources and pretreatment schemes.

There is a growing acceptance of some minimum summation of the ratio L/D [depth (L)/diameter (D)] as a guideline. A summation L/D ratio of 1200 (dimensionless L/D using ES for D) has been a common guide.

For conventional pretreatment with sedimentation, a common dual media uses 18 to 24 inches of anthracite of 0.90 mm effective size over 9 to 12 inches of sand of 0.45 mm effective size. The L/D (mm depth/mm ES) for the anthracite would range from 508 to 675 and for sand from 508 to 675. Thus, the summation L/D would range from 1016 to 1350.

A coarser top size is needed to accommodate higher solids load and algae blooms for direct filtration without sedimentation. For example, the new Los Angeles Department of Water and Power Plant uses 6 feet of 1.5 mm ES anthracite. The L/D ratio is 1219.

A tri-media for a conventional plant may use 16 inches of anthracite 1 mm ES, 9 inches of sand with 0.5 mm ES and 3 to 4.5 inches of garnet with 0.24 mm ES. This would provide an L/D ratio summation from 1180 to 1339.

So based on successful experience, the 1200 L/D seems supported. The important issue is to select the top size appropriate to the source water so that Unit Filter Run Volume production goals are achieved.

The choice of the grain size of the media at the top, where the water enters the filter bed, influences the depth of penetration of solids into the bed. The bigger the grain size, the better the solids penetration and thereby the better the bed utilization.

All Products Exceed AWWA Standards. NSF Approved.

Our filter media systems provide water and wastewater facilities cost savings to allow utilities to remain competitive by reducing costs. CEI Anthracite offers filter media systems designed to fit municipal systems need and budgets.

Why Buy and Ship Water?

CEI Anthracite		Competitor’s “Wet” Anthracite
1 Ton = 40 Cubic Feet		1 Ton = 38.46 to 35.71 Cubic Feet

Our dry anthracite filter media weighs only 50 pounds per cubic foot compared to 52 to 56 pounds per cubic foot for a “wet” product. This difference means you purchase less anthracite filter media to fit the same amount of space in the filter.

CEI Anthracite is an established, reliable on-time supplier of exact specifications. Our sophisticated anthracite filter media processing facility allows us to produce filter media in quantities and quality that will surpass most media sizing manufacturers.

Contact our sales office (link to contact email address) to discover how the wash water savings comparative analysis will benefit your specific application.

All Products Exceed AWWA Standards. NSF Approved.

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1-800-344-5770