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:
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).