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PUREFLOW BIO / ENGINEERING FIELD GUIDE

Turnover Rate and Biofilter Contact TimeFaster Is Not Always Better

How flow rate affects biofilter contact time, why pushing more water through can lower treatment, and how to balance flow.

Explore the process ↗Open the workbench
6 MIN GUIDEUPDATED NOVEMBER 2026
Reference illustration for Turnover Rate and Biofilter Contact Time: Faster Is Not Always BetterEQUIPMENT 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.
Pump and pipework hydraulic dutyPUREFLOW / INTERACTIVE PROCESS ATLASCONCEPT LAYOUT · NOT TO SCALESUCTION CONDITIONSIMPELLER / VOLUTEMEASURE THE DUTYTREATMENT RESISTANCEACTUAL FLOW COMES FROM THE PUMP AND SYSTEM CURVESMotion explains the process; it is not a measured flow rate or biological time model.
The pump transfers hydraulic energy to the water. Its headline flow is not the same as the delivered system flow.
Selected process stage

Supply the pump

Check the complete pump and system duty.

How it works

Maintain the approved suction arrangement and avoid dry running or air ingress.

What to establish
  • Check the complete pump and system duty.
  • Use internal pipe dimensions and measured operating flow.
  • Review supply conditions, protection and service isolation.

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

  • Contact time: Water needs to spend enough time in contact with the biofilm for ammonia to be taken up.
  • What limits it: Each media type has a hydraulic loading it handles well.
  • How to balance: Set tank turnover for oxygen and waste removal, then check the biofilter loading.
  • Sizing next: Combine this with biofilter sizing for the load.
Reference illustration for Turnover Rate and Biofilter Contact Time: Faster Is Not Always Better
Equipment reference visual; not evidence of a completed installation.
THE SHORT ANSWER

Contact time

Water needs to spend enough time in contact with the biofilm for ammonia to be taken up. Faster flow shortens it.

Turnover Rate and Biofilter Contact Time - Pureflow Bio
Reference visual. Equipment configuration and project details must be confirmed separately.
TURNOVER RATE

What limits it

Each media type has a hydraulic loading it handles well. Beyond it, performance can fall and solids can scour the biofilm.

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

TURNOVER RATE

How to balance

Set tank turnover for oxygen and waste removal, then check the biofilter loading. If it is too high, use more biofilters in parallel or a larger reactor. See turnover rate.

TURNOVER RATE

Sizing next

Combine this with biofilter sizing for the load.

Pureflow Bio equipment for this

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

Keep circulation and treatment separate

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

Turnover Rate and Biofilter Contact Time FAQ

Does a faster turnover clean water better?

Not necessarily. It can cut biofilter performance.

How do I check loading?

Divide flow by media volume or area and compare with the media maker’s limits.

KEEP READING
Turnover rate→Biofilter sizing→MBBR biofilters→Turnover Rate by System Type: Ponds, Aquariums, RAS and Natural Pools ↗

Discuss your system with Pureflow.

Share your application, operating volume, actual flow, loading and the question you are trying to resolve.

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