Zeolite for High-Concentration Ammonia Stripping & Recovery

Why high-concentration ammoniacal nitrogen requires a dedicated recovery process

Landfill leachate, anaerobic-digester digestate, and sludge-dewatering reject water (return flow) are representative high-concentration nitrogen wastewaters in which ammoniacal nitrogen (NH₄⁺-N) reaches several hundred to several thousand mg/L. Because the nitrogen load of these side-streams is very high relative to their flow, merging them directly into the mainstream bioreactor consumes excessive oxygen, carbon source, and reactor volume for nitrification and denitrification. This is why side-stream nitrogen management — separating and treating the high-concentration fraction ahead of the mainstream — has emerged as a key to reducing operating costs.

Two points distinguish this field from typical low-concentration ammonium removal (the general-wastewater application of the Environmental Remediation & Adsorption overview). First, the concentration is so high that single-use adsorption and replacement impose an excessive media-consumption and spent-media disposal burden; second, as awareness grows that nitrogen is a resource (fertilizer feedstock), the goal becomes recovery and resource reclamation rather than removal. In this field, therefore, cycle operation through capture → regeneration → concentration → recovery is the premise.

Why natural clinoptilolite — NH₄⁺ selective ion exchange and regeneration

Ammoniacal nitrogen exists in water mostly as the cation NH₄⁺. The natural clinoptilolite framework is negatively charged and attracts cations, and it is well known to have high selectivity for NH₄⁺ in particular. In stark contrast to anions such as nitrate (NO₃⁻) and phosphate, which are repelled by the natural framework and therefore presuppose separate metal or surfactant modification, ammonium works in its natural state without modification — a decisive advantage.

KMIZEOLITE's natural clinoptilolite, with 97% purity, a cation-exchange capacity (CEC) of 1.6–2.0 meq/g, a specific surface area of 40.0 m²/g, and a pore diameter of 4.0–7.0 Å, is well suited as an ion-exchange base material that preferentially captures NH₄⁺ even among co-existing cations such as K⁺, Na⁺, Ca²⁺, and Mg²⁺. A hardness of 4.0–5.0 Mohs and a stable pH range of 3.0–10.0 are advantageous for withstanding the mechanical and chemical loads of repeated adsorption/regeneration (backwash) cycles.

The heart of the recovery process is regeneration. Passing an NaCl brine (raising the pH with NaOH if needed) through the saturated media lets Na⁺ displace NH₄⁺, regenerating the media, while the released NH₄⁺ is concentrated into a small volume of regenerant. Ellersdorfer (2017, Water Science & Technology) presented an integrated operation that adsorbs and regenerates ammonium from sludge liquor with an ion-exchanger–loop-stripping process using NaCl-pretreated clinoptilolite, separating and recovering it by air stripping in the regeneration loop (Ellersdorfer, M., 2017, doi:10.2166/wst.2017.561).

Routes for converting recovered nitrogen into fertilizer have also been reported. Sancho et al. (2017, Science of the Total Environment) presented an integrated process combining natural zeolite with a hollow fibre membrane contactor to recover ammonia from domestic wastewater effluent as a liquid fertilizer (Sancho, I. et al., 2017, doi:10.1016/j.scitotenv.2017.01.123). As direct evidence for high-concentration wastewater, Cyrus et al. (2021, Molecules) removed ammonium from sludge water using natural clinoptilolite (Cyrus et al., 2021, doi:10.3390/molecules26010114), and for landfill leachate, ammonium removal using natural zeolite has been reported (Removal of ammonium from municipal landfill leachate using natural zeolites, Environmental Technology, 2015).

Quantitatively, Mažeikiene et al. (2008, Journal of Environmental Engineering and Landscape Management) reported, via column experiments on 0.315–0.63 mm clinoptilolite packed filtration, an NH₄⁺ removal efficiency of about 81% and a media adsorption capacity of about 0.5 mg/g under low-concentration influent (about 5 mg/L) conditions (Mažeikiene, A. et al., 2008, doi:10.3846/1648-6897.2008.16.38-44). Because adsorption capacity is greatly affected by influent concentration, contact time, and regeneration conditions, design values for high-concentration side-streams must always be confirmed through isotherm and breakthrough tests on the actual matrix.

KMIZEOLITE key properties

Item	Value
Clinoptilolite purity	97%
Cation-exchange capacity (CEC)	1.6–2.0 meq/g
Specific surface area	40.0 m²/g
Pore diameter	4.0–7.0 Å
Stable pH range	3.0–10.0
Hardness	4.0–5.0 Mohs
Thermal stability	700°C
Specific gravity	1.89
Bulk density	45–54 lbs/ft³
Certifications	OMRI KMI-10365, FDA GRAS, TSCA, EN-71-3

Ammonia stripping & recovery application examples

In this field, the key use is not as a "single-use adsorbent" but as a cycle medium that repeats adsorption, regeneration, and recovery. Representative scenarios are as follows.

• Landfill leachate side-stream recovery: passing high-concentration NH₄⁺-N leachate through an ion-exchange column to capture it, as a pretreatment that lowers the nitrogen load on mainstream biological treatment (based on a CEC 1.6–2.0 meq/g base material)
• Anaerobic-digestion digestate / reject water treatment: selectively capturing ammoniacal nitrogen from digestate and dewatering reject water in a side-stream to reduce the internal nitrogen-recycle load of the treatment plant
• Ion-exchanger–loop stripping: combining pH elevation and air stripping in the NaCl regenerant loop to separate NH₄⁺ into the gas phase and recover it as ammonium sulfate, etc.
• Liquid / crystalline fertilizer reclamation: treating the concentrated regenerant with a membrane contactor or acid absorption to convert nitrogen into liquid fertilizer or crystalline form
• Test / pilot application: pre-verifying NH₄⁺ isotherm and breakthrough, capacity decline per regeneration cycle, and competing-cation effects with a small sample

Recommended particle size and product specifications

For packed ion-exchange columns, balancing adsorption/regeneration rate against pressure drop is important, so a Fine Granule (30×50 mesh, 0.3–0.6mm) or Medium Granule (14×40 mesh) is common. For high backwash frequency or high-flow side-stream columns, consider Medium to Coarse Granule to reduce fines generation. In recovery processes with repeated regeneration, particle-size uniformity directly affects the reproducibility of breakthrough and pressure drop, so a single mesh grade is recommended.

Product family	Mesh	Particle size	Typical use
Powder	100 mesh or finer	<150μm	Pozzolan, feed, powder adsorption
Fine Granule	30×50 mesh	0.3–0.6mm	Water treatment, filtration, soil
Medium Granule	14×40 mesh	0.4–1.4mm	Filter media, bedding, litter
Coarse Granule	8×14 mesh	1.4–2.4mm	Swimming pools, de-icing, large-scale filtration
Extra Coarse	4×8 mesh	2.4–4.8mm	Packed beds, air scrubbers

→ View products by mesh size · Product selection guide by application

Pilot test and field review points

The design variables of a high-concentration recovery process differ greatly from simple adsorption. Be sure to check the following items together.

1. Influent concentration and matrix: leachate and digestate are high not only in NH₄⁺-N concentration but also in organics (COD), SS, and hardness, which cause media clogging and competitive exchange, so test with the actual wastewater.
2. Competing cations: K⁺, Ca²⁺, Mg²⁺, and Na⁺ compete for NH₄⁺ exchange sites, so check their ratios and reflect them in selectivity and breakthrough behavior.
3. Contact time and linear velocity: in column operation, the EBCT (empty-bed contact time) and linear velocity govern the breakthrough point and recovery efficiency.
4. Regeneration design: design together the NaCl concentration, whether NaOH co-dosing is needed, and the decrease in exchange capacity and regenerant-treatment load as a function of regeneration flow and frequency.
5. Recovery / reclamation route: decide which route — air stripping, membrane contactor, or acid absorption — will convert the concentrated regenerant into nitrogen, and verify the by-product specifications.
6. Field-specific notes: zeolite ion exchange is not a cure-all that replaces mainstream biological denitrification; it is generally considered as an auxiliary process that separates the high-concentration side-stream for recovery and pretreatment.

→ View TDS (Technical Data Sheet) · View MSDS (Material Safety Data Sheet)

Ammonia stripping & recovery FAQ

Why is natural clinoptilolite suitable for high-concentration ammonia recovery?

Ammoniacal nitrogen exists in water as the cation NH₄⁺, and the natural clinoptilolite framework is negatively charged, giving it a strong selective ion-exchange capacity for NH₄⁺. With a cation-exchange capacity in the CEC 1.6–2.0 meq/g range, it preferentially captures NH₄⁺ even among co-existing cations such as K⁺, Na⁺, and Ca²⁺. The key point is that, unlike anions such as nitrate (NO₃⁻), it works in its natural state without any separate modification.

How does adsorption differ from stripping/recovery?

Simple adsorption traps NH₄⁺ in the media and, once saturated, the media is replaced and disposed of. The stripping/recovery cycle backwashes (regenerates) the saturated media with an NaCl brine to concentrate NH₄⁺ into a high-concentration regenerant, which is then separated by pH elevation and air stripping or turned into a resource such as ammonium sulfate or liquid fertilizer. Ellersdorfer (2017, Water Science & Technology) recovered ammonium from sludge liquor using an ion-exchanger–loop-stripping process with NaCl-pretreated clinoptilolite.

Can it be used for high-concentration wastewater such as landfill leachate or digestate?

Yes. The primary targets of this process are exactly such high-concentration wastewaters — landfill leachate, anaerobic-digestion digestate, and dewatering reject water — where ammoniacal nitrogen reaches several hundred to several thousand mg/L. Numerous studies on ammonium removal from leachate using natural zeolite have been reported, and it is considered as a pretreatment that lowers the nitrogen load on mainstream biological denitrification, or as a side-stream recovery process. However, pretreatment is needed when organics, hardness, or SS are high.

How is regeneration performed and how many times is it possible?

Saturated media is mainly regenerated by passing an NaCl brine through it (raising the pH with NaOH if needed) so that Na⁺ displaces NH₄⁺. The regenerant becomes concentrated in NH₄⁺ and serves as feedstock for stripping, crystallization, or liquid-fertilizer production. The decrease in exchange capacity with the number of regenerations, fines generation, and the regenerant-treatment load must all be designed together, and the actual recovery rate and number of regenerations are best confirmed through a pilot.

Which particle size (mesh) is suitable?

For packed ion-exchange columns, a Fine Granule (30×50 mesh, 0.3–0.6mm) to Medium Granule (14×40 mesh) is common, balancing adsorption/regeneration rate against pressure drop. For high-flow side-stream columns or where backwash frequency is high, consider Medium to Coarse Granule. Please refer to the product selection guide by application.

Can I receive a sample for testing?

Yes, KMIZEOLITE supports the provision of samples for real-world application review. On the sample request page, please leave your application purpose (ion-exchange recovery/regeneration column, etc.), desired particle size, and influent NH₄⁺ concentration.

Inquiries and sample requests

If you are considering applying zeolite in the high-concentration ammonia stripping & recovery field, please contact us through the channels below.

• Sample request
• Technical inquiry
• Bulk quote request

Notice

Applicability may vary depending on site conditions, regulations, and test results. Before actual application, a test review tailored to site conditions must always be carried out first. Zeolite should be understood not as a cure-all for this field but as a material that supports existing processes.

Related pages

• Environmental Remediation & Adsorption overview
• Zeolite for nitrate management
• Mesh size chart
• Sample request