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PUREFLOW BIO / ENGINEERING FIELD GUIDE

Nitrification ExplainedThe Bacteria Behind Every Biofilter

A plain-language look at nitrification: the two bacterial steps, what they need to work and what slows them down.

Explore the process ↗Open the workbench
6 MIN GUIDEUPDATED NOVEMBER 2026
Reference illustration for Nitrification Explained: The Bacteria Behind Every BiofilterEQUIPMENT REFERENCE
Equipment reference illustration. Confirm the supplied model configuration and installation arrangement from its approved documentation.
01Understand the mechanismInspect the relevant process stages.
02Review the operating dutyKeep assumptions and measured values visible.
03Prepare the next decisionUse the guide, tools and project checks.
INTERACTIVE PROCESS ATLAS

See the mechanism.
Understand the duty.

Select a route or a stage to inspect the process. The cutaway explains the equipment and water environment; it is a teaching illustration, not a project drawing.

Swipe horizontally to inspect the equipment. Stage buttons below also centre the selected component.
Aerated biological treatment and samplingPUREFLOW / INTERACTIVE PROCESS ATLASCONCEPT LAYOUT · NOT TO SCALETAN-NpH°CPRE-SCREENED SUPPLYBIOFILM ON MOVING CARRIERSMEASURE THE PROCESSAIR DISTRIBUTIONNH₄⁺ → NO₂⁻ → NO₃⁻Motion explains the process; it is not a measured flow rate or biological time model.
Pre-screened water reaches the biological stage and continues through the retained-media outlet.
Selected process stage

Feed the reactor

Define peak feed and the nitrogen load.

How it works

Pre-screened water enters the biological stage. Effective upstream solids removal helps protect the reactor.

What to establish
  • Define peak feed and the nitrogen load.
  • Check oxygen, pH, alkalinity and temperature.
  • Use supported media performance and the specified fill arrangement.

Continue this guide ↗

Motion explains direction and mechanism; it does not represent measured performance. Geometry, stage order, pipe routes and equipment configuration are conceptual. Use the approved project design, operating instructions and verified model data.

Key takeaways

  • Two steps: First group: ammonia to nitrite.
  • What they need: Oxygen, a surface to live on, a steady supply of ammonia, alkalinity, and a reasonable temperature.
  • What slows them: Low oxygen, low pH, low alkalinity, cold water, and chemicals such as chlorine and some medicines.
  • What this tells you: If ammonia or nitrite rises in a mature system, check oxygen, alkalinity and recent medication first.
Reference illustration for Nitrification Explained: The Bacteria Behind Every Biofilter
Equipment reference visual; not evidence of a completed installation.
THE SHORT ANSWER

Two steps

First group: ammonia to nitrite. Second group: nitrite to nitrate. Nitrite is toxic too, so the second step matters as much as the first.

Nitrification Explained - Pureflow Bio
Reference visual. Equipment configuration and project details must be confirmed separately.
BIOFILTERS

What they need

Oxygen, a surface to live on, a steady supply of ammonia, alkalinity, and a reasonable temperature. They do not like extremes.

PLANNING WORKBENCH

Work with your own numbers.

Use the tools below to explore the relevant arithmetic. Enter measured values or declared assumptions. An estimate does not establish equipment capacity, biological performance or a safe operating limit.

Biofilter media planning scenario

Relate a defined nitrogen load to an explicitly supplied media conversion rate and fill share.

Assumptions and limits

Use a conversion rate verified for the media, water chemistry, oxygen, temperature and load. Example numbers are arithmetic inputs, not approved biological capacities or fill recommendations.

—TAN-N load · g/day
—Media volume · m³
—Nominal reactor volume · m³
Enter your values, or load the labelled arithmetic example. No design values are pre-filled.
FormulaMedia m³ = feed × TAN-N yield ÷ conversion rate. Reactor m³ = media m³ ÷ fill fraction.
Convert units before you calculate
Choose units and enter a value.

Planning arithmetic · inputs remain visible for review · example values are not operating recommendations

BIOFILTERS

What slows them

Low oxygen, low pH, low alkalinity, cold water, and chemicals such as chlorine and some medicines. Salt changes can also slow them in some cases.

BIOFILTERS

What this tells you

If ammonia or nitrite rises in a mature system, check oxygen, alkalinity and recent medication first. See alkalinity and pH.

BIOFILTERS

Grow, do not shock

Increase feed and stocking in steps so the bacteria population can keep up.

Pureflow Bio equipment for this

MBBR biofilters →Moving bed biofilters.Standard drum filters (RDF) →Automatic solids removal.
PROJECT REVIEW

Check the biological assumptions

Use these questions to prepare a project brief or an operating review. Check an item only when the information has been recorded for your installation.

0 of 3 checked

This checklist is a working aid in the current page session, not a saved maintenance record.

QUESTIONS

Nitrification Explained FAQ

Do these bacteria die if the pump stops?

They can suffer fast without oxygen, within hours for a dense biofilter.

Is nitrite always a problem?

It is toxic to many fish, so aim for zero.

KEEP READING
Biological filters→Biofilter start-up→Water quality→Biofilter Media Types: Plastic Carriers, Sand, Ceramic and Brushes ↗How to Size a Biofilter: TAN Load, Media and Reactor Volume ↗

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