Adsorbents and filter media for water treatment are 11 solid materials in 7 classes, from silica sand and anthracite to activated carbon, manganese greensand and activated alumina, that remove particles, organics, arsenic, iron, manganese or acidity as water passes through a bed or, for powdered carbon, as the powder is dosed. Most are never dosed by the mg/L, so how does an operator choose, load and certify a bed?
The 7 classes are granular filter media, activated carbons, catalytic oxidation media, metal-oxide adsorptive media (activated alumina, also written aluminium oxide media, and GFH/GFO), neutralizing media, natural zeolite and precoat media, one of the 16 families of water treatment chemicals.
Media are sized by contact time, not dose (GAC10 in 40 CFR 141.2: 10 minutes), and all 11 are certified under NSF/ANSI/CAN 61.
Every value on this page is checked against primary sources (NSF listings, eCFR, AWWA, EPA, Health Canada, EUR-Lex); see our methodology and fact-checking process.
What Are Filter Media and Adsorbents in Water Treatment?#
Filter media and adsorbents in water treatment are granular or powdered solids, such as sand, anthracite, activated carbon, greensand and activated alumina, that hold back particles or bind dissolved contaminants on their surface while water flows through them. An adsorbent holds contaminants on its surface; an absorbent takes them into its volume.
What does filter media remove from water?#
Filter media remove 6 groups of contaminants: particles and turbidity, organic matter including disinfection byproduct precursors, synthetic organics and PFAS, oxyanions such as arsenate and fluoride, dissolved iron, manganese and sulfide, and ammonium or acidity.
How do media differ from dosed chemicals and ion exchange resins?#
Media sit in a bed and work until they are exhausted, while dosed chemicals are fed continuously in mg/L (ppm); powdered activated carbon (PAC) is the one medium dosed like a chemical.
Synthetic resins exchange ions on a polymer bead and form a separate family; their capacity and regeneration are compared on ion exchange resins for water treatment.
How Do Filter Media and Adsorbents Work?#
Water treatment media work in 4 ways: depth filtration, adsorption, catalytic oxidation, and ion exchange or dissolution.
Depth filtration in granular and precoat beds#
Depth filtration traps particles inside the grain bed by straining, sedimentation and attachment, and a backwash restores the bed; in dual media, larger and lighter anthracite grains sit above finer, denser sand.
Rapid, slow and multimedia filter types and backwash design are covered under filtration in water treatment.
Adsorption on activated carbon and metal oxides#
Adsorbents bind dissolved contaminants on their surface: activated carbon holds organics in its micropores, while activated alumina and iron oxyhydroxide media exchange oxyanions such as arsenate and fluoride on surface hydroxyl groups.
Catalytic oxidation on manganese oxide surfaces#
Catalytic media carry a manganese oxide surface that oxidizes and adsorbs dissolved iron, manganese and sulfide, and an oxidant such as chlorine or potassium permanganate renews that surface.
Chlorine, permanganate and the other oxidizing chemicals are compared under oxidants for water treatment.
Ion exchange and dissolution in mineral media#
Mineral media change water chemistry by exchange or dissolution: clinoptilolite zeolite exchanges ammonium for sodium, and calcite dissolves in CO2-rich water, turning CO2 into bicarbonate and adding calcium.
11 Types of Water Treatment Media in 7 Classes#
The 11 media used in water treatment fall into 7 classes: 2 granular filter media, 2 activated carbons, 2 catalytic oxidation media, 2 metal-oxide adsorptive media, 1 neutralizing medium, 1 natural zeolite and 1 precoat medium. Table 1 compares the classes.
| Class | Members on this site | Mechanism | Typical role |
|---|---|---|---|
| Granular filter media | silica sand and garnet, anthracite | depth filtration | turbidity and particle removal after coagulation |
| Activated carbon in water treatment | GAC, PAC | physical adsorption | organics, DBP precursors, PFAS, taste and odor |
| Catalytic oxidation media | greensand, manganese dioxide | catalytic oxidation plus adsorption | iron, manganese, hydrogen sulfide |
| Metal-oxide adsorptive media | activated alumina, GFH/GFO (titanium- and zirconium-based media are also named by US EPA) | ligand exchange, surface complexation | arsenic, fluoride, selenium, phosphate |
| Neutralizing media | calcite (magnesia as a section) | dissolution | pH, alkalinity, remineralization |
| Natural zeolite | clinoptilolite | cation exchange | ammonium |
| Precoat filter media | diatomaceous earth | cake filtration | precoat filtration |
1. Granular filter media (2)#
Granular filter media are dense mineral grains for depth filtration; this class has 2: silica sand with garnet, and anthracite.
Silica filter sand and garnet#
Silica filter sand (SiO2) is the base granular filter medium of rapid, pressure and slow sand filters, and high-density garnet forms the finest, heaviest bottom layer of mixed-media beds.
Anthracite#
Anthracite is the coal-based filter medium that forms the coarse upper layer of dual and multimedia filters.
2. Activated carbon adsorbents (2)#
Activated carbons are porous carbon adsorbents used as a bed (GAC) or a dosed powder (PAC).
Granular activated carbon (GAC)#
Granular activated carbon (GAC) is a bed adsorbent for organic contaminants that is replaced or thermally reactivated once exhausted, and it is the medium named in the GAC10 and GAC20 definitions of 40 CFR 141.2.
Powdered activated carbon (PAC)#
Powdered activated carbon (PAC) is the dosed form of activated carbon: fed as a slurry for seasonal taste and odor or pesticide events, then removed with clarifier sludge or by low-pressure membranes.
3. Catalytic oxidation media (2)#
Catalytic media are manganese oxide-coated or solid MnO2 grains; this class has 2: greensand and manganese dioxide.
Manganese greensand#
Manganese greensand is glauconite or silica sand coated with manganese oxide that oxidizes and adsorbs iron, manganese and hydrogen sulfide, regenerated by chlorine or potassium permanganate.
Manganese dioxide media (pyrolusite)#
Manganese dioxide media (MnO2) are solid pyrolusite grains of more than 80 % MnO2 that catalyze iron and manganese oxidation and also oxidize arsenic(III) to arsenic(V).
4. Metal-oxide adsorptive media (2)#
Metal-oxide adsorptive media are aluminum- or iron-based oxyanion sorbents; this class has 2: activated alumina and GFH/GFO.
Activated alumina#
Activated alumina (Al2O3) is a porous aluminum oxide adsorbent of about 350 m2/g that removes fluoride and arsenate best below its zero point of charge, about pH 8.2.
Granular ferric hydroxide and ferric oxide (GFH/GFO)#
Granular ferric hydroxide and ferric oxide media (GFH/GFO) are iron oxyhydroxide sorbents for arsenic(III) and arsenic(V) that need no pH adjustment unless the water is above pH 8.
5. Neutralizing and remineralizing media (1)#
Neutralizing media dissolve to raise pH and alkalinity; this class has 1 entity, calcite.
Calcite (calcium carbonate)#
Calcite (CaCO3) is a dissolving mineral medium of at least 95 % calcium carbonate that raises the pH, alkalinity and calcium of acidic or desalinated water.
6. Natural zeolite (1)#
Natural zeolite is a mineral cation exchanger; this class has 1 entity, clinoptilolite.
Zeolite (clinoptilolite)#
Zeolite (clinoptilolite) is a natural aluminosilicate cation exchanger selective for ammonium, used as filter media and regenerated with sodium chloride brine.
7. Precoat filter media (1)#
Precoat media form a thin, renewable filter cake; this class has 1 entity, diatomaceous earth.
Diatomaceous earth#
Diatomaceous earth (DE) is an amorphous silica precoat medium built from diatom shells; DE filtration is one of the filtration technologies named in the Surface Water Treatment Rule (40 CFR 141.73(c)).
Which Media for Which Contaminant? Selection by Application and Water Quality#
Media selection follows the target contaminant first, then the water's pH, oxidant demand and competing ions, confirmed by a pilot or column test, because no medium removes every contaminant.
Turbidity and particles after coagulation#
Turbidity is removed by sand, garnet and anthracite beds after coagulation, or by a diatomaceous earth precoat.
The coagulant chosen ahead of the filter is compared under coagulants for water treatment.
Organics, disinfection byproduct precursors and PFAS#
Activated carbon is the default medium for organics: GAC beds remove DBP precursors, PFAS and many volatile and synthetic organics, while PAC handles seasonal taste and odor events but is not as efficient or economical as GAC for PFAS (US EPA). PFBS and PFBA adsorb less well than long-chain PFAS.
Arsenic and fluoride#
Arsenate and fluoride are removed by metal-oxide adsorptive media: activated alumina works best at an influent pH of 5.5 to 6.0 for fluoride and about 5.5 for arsenic, while iron media treat arsenic without pH adjustment up to pH 8. Arsenic(III) is oxidized first by chlorine, permanganate, ozone or MnO2 media; aeration does not work (US EPA).
Iron, manganese and hydrogen sulfide#
Iron, manganese and hydrogen sulfide are removed by catalytic greensand or manganese dioxide media, run at a filter pH of 6.0 or higher with 0.5 to 1.0 mg/L (ppm) of free chlorine through the filter (Health Canada, 2019). For permanganate-regenerated beds, KMnO4 demand (mg/L) = 1 x Fe + 2 x Mn estimates run length. Health Canada sets a manganese MAC of 0.12 mg/L.
Low pH, aggressive and desalinated water#
Acidic and aggressive water is corrected by calcite media, which dissolve until the water nears equilibrium, raising pH, calcium and alkalinity; in desalinated water a calcite contactor with CO2 dosing targets an alkalinity above 60 mg/L as CaCO3 (Duranceau, 2009).
Caustic soda, lime and soda ash, the dosed alternatives, are compared under pH adjustment chemicals.
By application: drinking water, wastewater and industrial systems#
Each application has a default medium, as Table 2 shows: granular and carbon beds in drinking water, catalytic media for iron and manganese, metal oxides for arsenic and fluoride, zeolite for ammonium and GAC for wastewater polishing.
| Application | Default media | Why | Key number |
|---|---|---|---|
| Drinking water treatment chemicals | sand, anthracite, GAC, DE | turbidity and organics | 0.3 NTU in 95 % of monthly measurements, never above 1 NTU |
| Disinfection byproducts | GAC | precursor (TOC) removal | GAC10: EBCT 10 min, reactivation every 180 days; TTHM 0.080 mg/L, HAA5 0.060 mg/L as LRAA |
| PFAS removal in drinking water treatment | GAC (anion exchange resin, RO and NF as alternatives) | long-chain PFAS adsorb well | PFOA and PFOS 4.0 ng/L each, compliance 2029-04-26 |
| Taste and odor control | PAC, GAC | geosmin, MIB | PAC below the product's NSF/ANSI/CAN 61 maximum use level |
| Arsenic removal from drinking water | activated alumina, GFH/GFO, MnO2 (As(III) oxidation) | oxyanion adsorption | MCL 0.010 mg/L |
| Fluoride in drinking water | activated alumina | ligand exchange | MCL 4.0 mg/L; influent pH 5.5 to 6.0 |
| Iron and manganese removal | greensand, MnO2 | catalytic oxidation | pH 6.0 or higher; 0.5 to 1.0 mg/L free chlorine |
| Remineralization of desalinated and soft water | calcite | CaCO3 dissolution | 2.27 mg/L CaCO3 per mg/L CO2 consumed |
| RO pretreatment chemistry | sand, anthracite, garnet (multimedia), GAC | particles; dechlorination by carbon | pilot test on the feed water |
| Wastewater treatment chemicals | zeolite | ammonium exchange | up to 2.7 mg NH4-N/g in column tests |
| Industrial wastewater treatment chemicals | GAC | tertiary polishing of organics | up to 99.9 % removal for many VOCs (US EPA) |
Loading, Contact Time and Dose by Media#
Media are sized by loading and contact time, not by dose: GAC is defined by an empty-bed contact time of 10 or 20 minutes, activated alumina needs at least 5 minutes, and iron media run at 5 to 20 m/h (2.0 to 8.2 gpm/ft2). Table 3 lists each medium, metric first.
| Media | System | Loading or dose | Basis | Operating condition |
|---|---|---|---|---|
| Silica sand, garnet, anthracite | rapid and pressure filters | per the state design standard | m/h (gpm/ft2) of bed area | effluent turbidity rule |
| GAC | drinking water, DBP precursors | EBCT 10 min (GAC10) or 20 min (GAC20) | average daily flow | reactivation every 180 days (120 days as Stage 2 BAT) or 240 days |
| PAC | drinking water, taste and odor, SOCs | product MUL 100, 250, 590 or 750 mg/L (ppm) | as product | fed apart from chlorine and other oxidants |
| Manganese greensand | groundwater Fe, Mn | typical 9.5 m/h (4 gpm/ft2) for manganese-coated media (Recommended Standards for Water Works, 2022 edition, 4.8.3 d) | bed area | pH 6.0 or higher; 0.5 to 1.0 mg/L free chlorine through the filter |
| Manganese dioxide | groundwater Mn | 24 to 63 m/h (9.8 to 25.8 gpm/ft2), contact 1 min or less (fluidized-bed study) | bed area | oxidant ahead of the filter; pH 6.2 to 7.8 in the study |
| Activated alumina | fluoride, arsenic | EBCT at least 5 min | bed volume | influent pH 5.5 to 6.0 (fluoride), about 5.5 (arsenic); effluent pH 8.5 or lower |
| GFH/GFO | arsenic | 5 to 20 m/h (2.0 to 8.2 gpm/ft2); contact 4 to 6 min; bed 0.6 to 1.6 m (manufacturer data) | bed area | no pH adjustment unless pH above 8 (US EPA) |
| Calcite | acidic water; RO permeate | 7.3 to 14.7 m/h (3 to 6 gpm/ft2) (manufacturer data) | bed area | influent pH 5.0 to 7.0; 2.27 mg/L CaCO3 dissolves per mg/L CO2 |
| Zeolite | municipal wastewater ammonium | design loading set by pilot test | n/a | column capacity up to 2.7 mg NH4-N/g (study) |
| Diatomaceous earth | DE filtration | precoat plus body feed | n/a | 1 NTU in 95 %, never above 5 NTU |
How is a PAC dose different from a media bed?#
A PAC dose is a chemical feed in mg/L (ppm) as product, capped by the product's NSF/ANSI/CAN 61 maximum use level of 100, 250, 590 or 750 mg/L (NSF listings checked 2026-10-20), while a bed medium has no dose at all.
The chemical dosage calculator converts a PAC dose in mg/L into kg/d and lb/day.
Worked example: how much alkalinity does a calcite contactor add?#
Worked example: permeate carrying 20 mg/L (ppm) of dissolved CO2 that is fully consumed in a calcite contactor dissolves about 45 mg/L of CaCO3 (20 x 2.27 = 45.4), adding about 45 mg/L of hardness and 45 mg/L of alkalinity, both as CaCO3. Inputs: 20 mg/L CO2 consumed (assumed); 2.27 mg/L CaCO3 per mg/L CO2 (stoichiometric).
How Are Media Performance and Exhaustion Monitored?#
Media performance is monitored in 3 layers: effluent quality against the treatment rule, breakthrough tracked by bed volumes or sampling ports, and a regeneration, reactivation or replacement trigger.
Effluent targets: filtered-water turbidity#
Granular filters in conventional and direct filtration must produce at most 0.3 NTU in 95 % of monthly measurements and never exceed 1 NTU (40 CFR 141.173), while slow sand and DE filters must stay at or below 1 NTU in 95 % and never exceed 5 NTU (40 CFR 141.73).
NTU and FNU are explained under turbidity in water.
Breakthrough and bed-volume counting#
Adsorbent beds are exhausted when the contaminant breaks through, so operators count bed volumes on activated alumina and iron media, track TOC or UV254 after GAC, and sample between lead and lag vessels for PFAS.
Regeneration, reactivation and replacement#
Each medium has its own end-of-run step; the 5 steps are listed below.
- Activated alumina: 1 % NaOH, about 5 % capacity loss after five regenerations (EPA/600/R-14/236).
- Greensand: chlorine or potassium permanganate.
- Zeolite: sodium chloride brine.
- GAC: thermal reactivation (ANSI/AWWA B605-18).
- Iron media: replacement.
Which Standards and Regulations Apply to Filter Media?#
Filter media for drinking water are governed in 3 layers: NSF/ANSI/CAN 61 process-media certification, AWWA B-standards for the materials, and treatment rules that name media as best available technology.
NSF/ANSI/CAN 61 process media certification#
Water treatment media are certified under NSF/ANSI/CAN 61 as process media, not under NSF/ANSI/CAN 60, which covers dosed chemicals; calcium carbonate and magnesium oxide are the two NSF/ANSI/CAN 60 exceptions. Table 4 gives the route and maximum use level per medium.
| Media | Standard | Maximum use level (as product) | Note |
|---|---|---|---|
| Silica sand, garnet, anthracite | NSF/ANSI/CAN 61 process media | n/a (bed media) | filtration media listings |
| GAC | NSF/ANSI/CAN 61 | n/a | process media |
| PAC | NSF/ANSI/CAN 61 | 100, 250, 590 or 750 mg/L, product-specific (NSF listings checked 2026-10-20) | certified as process media |
| Greensand, manganese dioxide | NSF/ANSI/CAN 61 | n/a | MnO2 media listings |
| Activated alumina, GFH/GFO | NSF/ANSI/CAN 61 | n/a | off-site regenerated iron media must meet NSF requirements to keep the certification |
| Calcite (calcium carbonate) | NSF/ANSI/CAN 60 chemical category (graded media also under 61) | most common 650 mg/L; range 150 to 650 mg/L (NSF listings, 2026-10-21) | product-specific |
| Magnesia (section of calcite) | NSF/ANSI/CAN 60 (dosed magnesium oxide) | 100 mg/L in every listing (NSF listings, 2026-10-21) | dosed MgO belongs to magnesium hydroxide |
| Zeolite, DE | NSF/ANSI/CAN 61 | n/a | filtration media listings |
How NSF/ANSI/CAN 60 and its companion standard 61 are applied is explained on NSF/ANSI/CAN 60 certification.
AWWA B-standards for filter media and carbon#
Seven AWWA B-standards cover water treatment media: ANSI/AWWA B100-25 for granular filter media, B101-22 for precoat media, B102-26 for manganese greensand, B103-25 for manganese oxide media, B600-24 for PAC, B604-18 for GAC and B605-18 for GAC reactivation. Activated alumina, iron-based media, calcite and zeolite have none (AWWA standards list, checked 2026-10-20).
| Standard | Title | Media |
|---|---|---|
| ANSI/AWWA B100-25 | Granular Filter Media | silica sand, garnet, anthracite |
| ANSI/AWWA B101-22 | Precoat Filter Media | diatomaceous earth (and perlite) |
| ANSI/AWWA B102-26 | Manganese Greensand for Filters | greensand |
| ANSI/AWWA B103-25 | Manganese Oxide Filter Media | manganese dioxide |
| ANSI/AWWA B600-24 | Powdered Activated Carbon | PAC |
| ANSI/AWWA B604-18 | Granular Activated Carbon | GAC |
| ANSI/AWWA B605-18 | Reactivation of Granular Activated Carbon | reactivated GAC |
Every edition is listed under AWWA B-series standards.
EU Drinking Water Directive Article 12#
In the EU, Article 12 of Directive (EU) 2020/2184 requires that treatment chemicals and filter media do not compromise health, do not adversely affect color, odor or taste and do not unintentionally enhance microbial growth, with purity assessed using European standards.
Article 12 obligations are set out under EU Drinking Water Directive 2020/2184.
Treatment rules that name media as best available technology#
US drinking-water rules name media directly: GAC10 and GAC20 are regulatory definitions in 40 CFR 141.2 and best available technology for TTHM and HAA5, GAC is one of 4 BATs for the regulated PFAS, and activated alumina is BAT for arsenic(V), beryllium, selenium and thallium (40 CFR 141.62). The 2026-05-20 PFAS proposals (91 FR 29425, 91 FR 29413) are pending, not final, as of 2026-10-20.
All treatment rules under the Safe Drinking Water Act are summarized on its own page.
Complete List of Water Treatment Media: All 11 in One Table#
The complete list below gives all 11 water treatment media with CAS number, class, function, systems, certification route and AWWA standard.
| # | Media | CAS | Class | Function | Systems | Certification | AWWA |
|---|---|---|---|---|---|---|---|
| 1 | silica filter sand and garnet | 14808-60-7 (quartz); 12178-41-5 (garnet group; almandine 1302-62-1) | granular filter | depth filtration | drinking water; RO pretreatment; cooling side-stream | NSF/ANSI/CAN 61 | B100-25 |
| 2 | anthracite filter media | 8029-10-5 | granular filter | depth filtration (upper layer) | drinking water; RO pretreatment | NSF/ANSI/CAN 61 | B100-25 |
| 3 | granular activated carbon (GAC) | 64365-11-3 | activated carbon | adsorption | drinking water (DBP precursors, PFAS, taste and odor); wastewater polishing | NSF/ANSI/CAN 61 | B604-18; B605-18 |
| 4 | powdered activated carbon (PAC) | 64365-11-3 | activated carbon | adsorption (dosed) | drinking water (taste and odor, SOCs) | NSF/ANSI/CAN 61, MUL 100 to 750 mg/L | B600-24 |
| 5 | manganese greensand | none (coated mineral) | catalytic oxidation | Fe, Mn, H2S oxidation and adsorption | groundwater drinking water | NSF/ANSI/CAN 61 | B102-26 |
| 6 | manganese dioxide filter media | 1313-13-9 | catalytic oxidation | Fe, Mn, H2S; As(III) oxidation | groundwater drinking water | NSF/ANSI/CAN 61 | B103-25 |
| 7 | activated alumina | 1344-28-1 | metal-oxide adsorptive | fluoride, arsenate, selenite adsorption | drinking water | NSF/ANSI/CAN 61 | none |
| 8 | granular ferric hydroxide (GFH/GFO) | 1309-33-7 (iron(III) hydroxide); 20344-49-4 (FeO(OH)) | metal-oxide adsorptive | arsenic, phosphate, antimony adsorption | drinking water (wellhead) | NSF/ANSI/CAN 61 | none |
| 9 | calcite (calcium carbonate) media | 471-34-1 (calcium carbonate); 13397-26-7 (calcite) | neutralizing | pH, alkalinity, remineralization | drinking water; desalination post-treatment | NSF/ANSI/CAN 60 (most common 650 mg/L); graded media NSF/ANSI/CAN 61 | none |
| 10 | zeolite (clinoptilolite) | 12173-10-3 (clinoptilolite); 1318-02-1 (zeolites, general) | natural zeolite | ammonium exchange; filtration | municipal wastewater; drinking water | NSF/ANSI/CAN 61 | none identified |
| 11 | diatomaceous earth (precoat filter media) | 61790-53-2 | precoat | cake filtration | drinking water (DE filtration) | NSF/ANSI/CAN 61 | B101-22 |
Every other chemical is filterable by CAS, function and NSF status in the water treatment chemical database.
Who Supplies Filter Media and Media Filtration Programs?#
Filter media are bought either as material, delivered to an NSF/ANSI/CAN 61 and AWWA specification, or as part of a treatment program in which a provider selects, loads, monitors and replaces the bed. US EPA added an activated carbon supply chain profile in June 2026. Distributors by region are listed under water treatment chemical suppliers.
Texas TCEQ rules, cited in a municipal bid, require drinking-water treatment chemicals and media to conform to NSF/ANSI/CAN 60 and 61.
How to compare program providers is covered under water treatment companies.
Are Filter Media Safe to Handle and to Use in Drinking Water?#
Certified media meet the NSF/ANSI/CAN 61 health-effects requirements for drinking water; at the plant, wet activated-carbon vessels can deplete oxygen, and manganese dioxide carries the harmonised CLP Annex VI classification H302, H332 (index 025-001-00-3). For the other media, see the supplier SDS.
What is the best filter media for drinking water?#
No single filter medium is best for drinking water: the best one is certified and removes the target contaminant at the water's pH, confirmed by a pilot test.
How often should filter media be changed?#
Media change on exhaustion, not on a calendar: GAC10 beds are reactivated every 180 days by definition, iron media are replaced at arsenic breakthrough, and greensand and activated alumina are regenerated in place.
What are the three types of filter media?#
Filter media do 3 jobs, listed below.
- Filtering media, such as sand, anthracite and DE, hold particles.
- Adsorbents, such as carbon and alumina, bind dissolved contaminants.
- Reactive media, such as greensand and calcite, change water chemistry.
What happens to spent PFAS-laden carbon?#
Spent PFAS-laden GAC is managed under EPA's 2026 Interim Guidance on the Destruction and Disposal of PFAS and Materials Containing PFAS, released on 2026-04-23 as its third edition. With PAC, the PFAS ends up in the sludge (US EPA).