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Frequently Asked Questions (FAQ)

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1) What is a simple analogy for the zeolite-anammox process?

Fish = Ammonia

Fishermen = Anammox

Net = Zeolite


1.The net (zeolite) catches fish (ammonia) and fishermen (anammox) eat them.

2.The anammox (fishermen) keep removing ammonia (fish) from the zeolite (net) and eating them.

3.The cycle continues and continues.

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2) What are the key issues in nitrogen removal technologies?

There are many factors to consider, but the most important ones are cost, effiency, operation and maintenance, robustness, and ease of use. 

3) What are some challenges which reduce the efficiency of the zeolite-anammox system?


Some potential problems for the zeolite-anammox include the slow growth rate of the anammox bacteria, TSS clogging, and biofilm clogging. However, because anammox bacteria produce very little sludge, if the influent has undergone adequate primary settlement, then clogging can be minimized substantially. Appropriate design can also be used to mitigate the growth of nitrifying bacteria which would increase the amount of sludge produced. The key factors to pay attention to are influent ammonia, influent BOD, and media pore size.

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4) Does the zeolite-anammox system emit less greenhouse gases compared to traditional nitrogen removal technologies?

Yes, because the anammox bacteria are believed to be autotrophic, unlike traditional denitrification using nitrosomonas and nitrobacter, there is no need to input a source of reduced carbon for use as an electron source. Dissolve inorganic carbon is believed to be the source of carbon used for biomass production. Additionally, because the anammox process only requires approximately one-half of the influent ammonium to be aerated and oxidized to nitrite as opposed to traditional denitrification which requires all of it to be oxidized, energy is saved. In summary, because anammox does not require a reduced carbon source, and because it only requires half of the aeration that's needed in traditional denitrification, the zeolite-anammox process has a much smaller carbon footprint.

Furthermore, production of nitrous oxide N2O is unavoidable during nitrification, and it is estimated that approximately 1% of the influent nitrogen is converted to N2O by nitrifiers. This percentage is significant because the severity of N2O as a greenhouse gas over 20 years is 289 times greater than CO2. Through the zeolite-anammox system, N2O emissions are cut by 50%. 

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5) How difficult is the zeolite-anammox system to operate and maintain?


The non-aerated variant is completely self-regulating and very simple to run. Once it is established it does not need any adjustment.

The aerated variant is largely self-regulating but the flows and aeration need to be balanced. A current side-stream treatment system operating in the Bay Area has required two adjustments in 12 months.

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6) Will the zeolites dissolve or disintegrate into slush?


Not if the appropriate zeolite is selected. There are 90 different types of zeolite and some of the key parameters can vary significantly: durability, CEC, NH4 adsorptivity, particle size, and permeability. The durability question is one of the most common – however the City of Naples in Italy has mediaeval masonry buildings constructed of local zeolite rock. The zeolite-anammox process uses zeolite that is classed a soft rock, with a Mohs hardness of about 4. 

7) What is the typical detention (treatment) time?

Typically a pilot plant data using ¾” single size zeolite will initially start with a one day detention time. The detention time can be adjusted as required to balance the conflicts of cost and time. One zeolite plant that functioned successfully for 28 years used sand-sized zeolite and a 30 minute detention time for adsorbing the ammonium.

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8) What are the maximum flows?

Theoretically there is no maximum flow, but the surface area method would require too much acreage for extremely large flows to be practical. The aerated method is more efficient but a higher efficiency (i.e. small footprint) reduces the cost advantages. 

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9) What are the major variables affecting the process?

Some of the critical variables include:

  • Temperature and climate

  • Flow rate (detention time)

  • Influent concentration and treatment standard (effluent concentration)

  • Clients’ specific requirements, and available area

  • Zeolite costs including transportation

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10) Why are construction costs lower?

Constructions costs are lower because zeolite-anammox is a one stage system (nitri/deni is a two-stage process). Also the surface area method does not require expensive infrastructure.

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11) Why are operating and maintenance costs lower?

Surface area method:

  • Operating costs for the surface area method are lower because the system does not require aeration, operates at ambient temperature, is gravity flow, and does not need  ancillary food (e.g. methanol) needed for denitrification.

  • Maintenance costs for the surface area method are lower because the system is fixed film - basically self-sufficient and self-regulating, and low tech with few moving parts.

Volume aeration method:

  • Operating costs for the aeration method are lower because the system only requires partial aeration.

  • Maintenance costs for the aeration area method are lower because the system is fixed film, and designed to be self-sufficient and self-regulating.

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12) How can I set up my own zeolite-anammox system, is there a patent on it?

To find out more about whether the zeolite-anammox system is right for you, please contact us and describe the circumstances of your problem. A patent is currently pending.

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