The SN8 online respirometer and the SICAIR algorithm aerate according to the real demand of the biomass, not a fixed oxygen setpoint.
Compliant, but at the limit
Martorell WWTP discharges into the Llobregat river, a sensitive area that requires carbon, nitrogen and phosphorus removal. The plant was compliant, but total nitrogen in the effluent was too close to the 15 mg/L discharge limit.
Aeration controlled by oxygen probes with a fixed setpoint ignored what really matters: how much oxygen the bacteria need at each moment.
Before
- Fixed oxygen setpoint
- Aeration with peaks and troughs
- Total N close to the limit
With SICAIR
- Air matched to real biomass demand
- Balanced, stable aeration
- Lower, more stable total N
Measure the biology and aerate accordingly
Measure
The SN8 respirometer analyses the sludge automatically 24/7: overall activity (OUR/SOUR) to detect rain events, overloads or toxicity, and nitrification rate (AUR) to know how much ammonium the biomass can remove.
Calculate
SICAIR turns that activity into the oxygen the process needs and the blower minutes for each cycle, adapting automatically to rain and overloads.
Control
The setpoint reaches the plant SCADA via Modbus, with two-way communication. If anything goes wrong, the plant automatically falls back to probe control: it is never left without control.
Total nitrogen in effluent (mg/L)
Annual averages from plant operating data. Since SN8 + SICAIR was implemented (2022–2023), effluent total nitrogen has fallen and stabilised, even though the influent nitrogen load rose by around 40 %.
- Effluent nitrate: from 5.3 to 2.4 mg/L on average (−56 %)
- Total nitrogen removal efficiency: from 77 % to 87 %
- More balanced aeration, without peaks and troughs, and more stable biomass
SICAIR 3.0: from reacting to anticipating
In 2026 Martorell added SICAIR 3.0: a proprietary machine learning model, trained on years of the plant’s own respirometry data, that anticipates the biological demand of the next cycle.
In partnership
Project developed by SENSARA with RUBATEC and the Catalan Water Agency (ACA), with integration by INCONEF.
What is happening in your reactor?
We install the SN8 respirometer at your plant as a trial with purchase option: if you are convinced, it stays; if not, we remove it.
Effluent quality data: annual averages from plant operating analyses, 2019–2024. Energy saving calculated against the period of dissolved-oxygen probe control.
