March 23, 2026 · Erik Rumbaugh
How fast do nitrifiers really grow?
If you’ve ever wondered why Nitrite spikes show up during startup—or why hot summers can throw your system off—you’re really asking about one thing: replication rates.
Nitrosomonas (AOB) and Nitrospira (NOB) are the most common wastewater chemolithoautotrophic nitrifiers, which is a fancy way of saying they grow much slower than typical heterotrophs. Their doubling times shift dramatically with temperature, and those shifts matter for process stability.
Here’s a quick look at how temperature shapes their growth:
Doubling Times: Nitrosomonas vs. Nitrospira
| Temperature | Nitrosomonas (AOB) | Nitrospira (NOB) | What It Means |
|---|---|---|---|
| 10°C | 50–70 hrs | 60–80 hrs | Extremely slow; nitrification drags. |
| 20°C | 18–24 hrs | 22–30 hrs | Typical growth; AOB usually stay ahead. |
| 30°C | 7–12 hrs | 12–18 hrs | Near‑optimal for most wastewater systems. |
| 35°C | 8–15 hrs | 15–24 hrs | AOB still strong; some NOB begin to stress. |
| 40°C+ | Sharp decline | Inhibition | Most strains stop replicating or die off. |
Why This Matters in the Plant
AOB are faster. Nitrosomonas almost always outpace Nitrospira. That’s why new systems often show a nitrite bump—the “second stage” oxidizers simply need more time to catch up.
NOB are more heat‑sensitive. Above ~35°C, Nitrospira can drop out first. When that happens, nitrite accumulates and toxicity risks rise.
Temperature accelerates metabolism. Up to their optimum, nitrifiers follow the Arrhenius rule: roughly doubling metabolic rate for every 10°C increase. Mathematically:
kT=k20⋅θ(T−20)
with θ≈1.072 for nitrifiers.
Another more detailed table of growth rates:
| Approximate Doubling Time (days) | Doubling Time (hours) | Context / Typical Organism & Conditions |
|---|---|---|
| 0.4–0.6 | 9.6–14.4 | Fastest reported for Nitrosomonas europaea (optimal ~28–35°C, high substrate, continuous culture) |
| 0.5–1.0 | 12–24 | Typical optimal range for Nitrosomonas spp. (e.g., 13–15 h minimal in some studies at ~30°C) |
| 1.0–1.5 | 24–36 | Common for many Nitrosomonas strains under good lab conditions (~25–30°C) |
| 1.3–1.5 | 31–36 | Nitrospira moscoviensis (optimal ~37°C) |
| 1.3–1.5 | 32–37 | Nitrospira defluvii and related strains (optimal ~28–32°C) |
| 1.5–2.0 | 36–48 | Slower Nitrospira or mixed conditions; some enriched cultures |
| 1.8–2.5 | 44–60 | Cold-adapted or limiting conditions (e.g., Ca. Nitrotoga ~44 h at low °C) |
| 3–7 | 72–168 | Low temperatures (e.g., 10–15°C) or substrate-limited wastewater/biofilm systems |
Key observations :
- Growth roughly doubles every ~10°C rise in the 10–30°C range for many nitrifiers (θ ≈ 1.08–1.13, or ~7–13% increase per °C).
- In wastewater/biofilm systems, temperature sensitivity is often lower (θ ≈ 1.02–1.03) due to mass transfer effects and acclimation, allowing better performance at low temperatures than pure culture data suggest.
- Nitrospira frequently outcompetes Nitrobacter at low nitrite and low temperatures in engineered systems.
- Exact values vary; for precise modeling, consult specific strain data (e.g., N. europaea optima ~28–35°C; many Nitrospira ~28–37°C).