NODE Biosensor principle and design
What is NODE?
NODE technology is a tool for monitoring aquatic, urban or industrial environments that provides real-time information on water quality. It comes in the form of a probe which can be installed directly in the environment to be monitored or as a bypass.
What is the principle of the NODE technology?
The biosensors generate an electrical signal that is a direct reflection of the activity of bacteria present on the surface of the electrodes.
What does the NODE biosensor measure?
The biosensor measures microbial activity in real time. This activity is converted into an electrical signal directly exploitable.
Why measuring microbial activity?
Bacteria are very sensitive to environmental condition variations and their activity evolves very quickly in the face of any changes in the quality of water. The measurement of their activity (microbial activity) is therefore an immediate indicator of the state of the environment (eg, increase or decrease in organic load, presence of toxic compounds…). In addition, many biological processes depend on microbial activity (eg, wastewater treatment plants) and their effectiveness linked to the activity rate of the microorganisms involved.
What kind of bacteria are used?
The bacteria used are the bacteria naturally present in the water to be monitored. Adapted to the environment and representative of the site, they are sensitive to any changes in the quality of the water they are exposed to. We do not use GMOs or laboratory-grown bacteria which often adapt poorly or do not survive when used in the environment or on an industrial site.
What is the response time of the biosensor?
Bacteria being very sensitive to environmental variations, the response time is immediate. Response time is basically defined by the time lag used for data acquisition. Usually, time interval is set up at 2 or 5 min and can be modified (shortened or lengthened) according to the requirements of each site.
Are there different models of NODE biosensors?
Depending on the objectives or constraints of the site, we can propose 2 types of biosensors. The universal model comes in the form of a snorkel that can be installed in situ (immersed directly in the water to be monitored) at any site. Its modular design makes it possible to adapt to the specific constraints of each situation. A second model of biosensor, installed in line (fed through a pump taking water from the site) is also available upon request.
What is the size of the NODE biosensor?
The biosensor is 40 mm in diameter. Its standard length is 800 mm and can be adjusted in increments of 500 mm. The standard length of the connection cable is 7 m. Connecting bends or flexible extensions can also be adapted to cope with site constraints (eg, shallow waters) and facilitate installation.
What are the main fields of applications?
NODE biosensors are used to monitor natural, urban and industrial aquatic environments:
- Urban and industrial wastewater (eg, sewage networks, treatment plants…)
- Discharges into the natural environment (eg, spillway, receiving environment…)
- Groundwater (eg, catchment fields, contaminated water tables…)
- Surface water (eg, lakes, rivers, coastal waters…)
NODE Biosensor Applications
What are the main applications of the NODE biosensor?
Due to their ability to detect the presence of toxic compounds or variations in organic load, NODE biosensors are particularly suited for the following applications:
- Monitor water quality in real time
- Identify fluctuations or qualities of influents and effluents
- Monitor and protect water resources
- Identify the source of pollution (eg, sectorization of sewage networks)
- Protect wastewater treatment plants from toxic events
- Evaluate and optimize the performance of treatment processes
- Reduce operational costs of wastewater treatment
Does the NODE biosensor detect contaminants or toxic compounds?
Yes, the biosensor can detect the presence of all chemical compounds that have an impact on the activity of bacteria (eg, detergents, biocides…)
Can the NODE biosensor quantify contaminants or toxic products?
Depending on the applications, NODE biosensors can be calibrated in order to assess organic loads in real time (eg, BOD5, COD…). While our biosensor has been designed to provide global information, it can, in some cases, quantify contaminants when they are predominantly present in the environment. (eg, hydrocarbons in groundwater).
Can the NODE biosensor identify contaminants or toxic compounds?
No, the biosensor is an overall indicator of microbial activity and does not allow the identification of the responsible compound(s). The biosensor can however be associated with either physicochemical probes (eg, pH, conductivity, ORP…) to qualify the type of pollution that has occurred or to an automatic sampler (targeted sampling).
Does the NODE biosensor detect metals?
Depending on the specificity of the sites, it is in some cases possible to detect the presence of metals in the water. However, bacteria colonizing the electrodes may develop a resistance to heavy metals or MTE.
Does the NODE biosensor detect micropollutants?
No, the levels of micropollutants in water are often too low to be detected by the current model of NODE biosensors.
Can the NODE biosensor help me reduce my operating costs?
Yes, the information provided by the biosensor can be used to ensure a permanent diagnosis and make self-monitoring more reliable. In particular, they can help in the management of crisis situations (eg, toxic compounds impairing bioprocesses, storm episodes…), in the prevention and control of non-conformities or in the optimization of treatment processes.
The use of NODE biosensors for monitoring control sanitation systems or treatment processes ultimately leads to a reduction in environmental impacts and penalties related to discharges into the environment as well as a reduction operating costs (eg, energy costs, sludge management, quantity of additives…).
Can the NODE biosensor measure BOD5 and COD?
Yes, the biosensor can be calibrated to provide an assessment of BOD5 or COD on line and in real time. In 2018, the technology received ETV (Environmental Technology Verification) certification issued by the LNE (National Metrology and Testing Laboratory) regarding the assessment of BOD5 in real time.
Does the use of biosensor replace regulatory self-monitoring data?
No, although NODE biosensors provide a permanent diagnosis and make self-monitoring more reliable, the information provided does not replace regulatory self-monitoring data.
NODE Biosensor installation & maintenance
Can the NODE biosensor be installed anywhere?
Yes, NODE biosensors can be installed in all types of natural, urban or industrial aquatic environments. On one hand, because the modular design of the biosensor makes it possible to cope with the specific constraints of each site (eg, depth of a water table, tidal range, low water depth, limited space, isolated geographical area, no power source available…) and, on the other hand, because the biosensor (and the associated acquisition unit or additional probes) are completely autonomous energetically.
What are the main constraints when using the NODE biosensor?
There are no particular constraints associated with the use of NODE biosensors. The main constraint being that the probe must be kept in water so as not to artificially alter the activity or survival of bacteria present on the surface of the electrodes.
Does the NODE biosensor require significant maintenance?
Compared to most probes, NODE biosensors require little or no maintenance since they exploit microbial growth that is often the source of malfunction and main maintenance of most online metrology systems (biofoufing). The frequency of maintenance is site-specific and typically ranges from once or twice per month (eg, sewage networks) to once per year (eg, groundwater).
Does the NODE biosensor require calibration?
The NODE biosensor can be used in most situations without calibration (eg, detection of toxic compounds, variations in organic load). For certain applications, and if the objective is to quantify or correlate certain parameters with the biosensor signal, a calibration can be carried out (eg, BOD5, COD, concentration of toxic compounds…). The calibration can be carried out before deployment or directly on site.
How is the data generated by the NODE biosensor recovered?
The NODE biosensor is associated with an acquisition unit (DTU2) which records and transmits the data generated (GPRS / 3G) to a dedicated server. The transmitted data can be consulted and retrieved (personal secured access) through a web interface or our dedicated software for data management, WinFluid NG.
Thresholds (high and low) can also be defined in order to send alerts in the event of anomalies being detected (SMS) or trigger actions (eg, targeted sampling). The acquisition unit also allows the association of other probes in parallel (eg, pH, ORP, dissolved O2, conductivity, temperature, turbidity, flow rates…) and all data sets can be transmitted raw or processed.
What types of data does the NODE biosensor provide?
By default, the signal provided by the NODE biosensor is expressed in mV. If the objective is to quantify or correlate certain parameters with the biosensor signal, a calibration can be carried out (eg, BOD5, COD, concentrations of toxic compounds…) and integrated into the acquisition unit in order to directly express the desired unit (eg, concentration in mg/l, relative change in %).
In case of an anomaly, does the biosensor send an alarm?
Yes, the acquisition unit associated with the biosensor allows our customers to be informed in real time. In the event of an anomaly, or according to any other defined criteria (eg, high and/or low threshold, signal variations…), alarm sending via SMS can be programmed.
Can the NODE biosensor be coupled to an automatic sampler to take a water sample if an anomaly is detected?
Yes, the NODE biosensor can be associated with an automatic sampler (energetically autonomous) and as for alarms, trigger directed sampling according to defined criteria. The triggering of sampling can be established from the biosensor signal or from the integration of several signals from different probes connected to the acquisition unit (eg, pH, conductivity, turbidity…).
Can the NODE biosensor be coupled to other probes?
Yes, the acquisition unit associated with the NODE biosensor makes it possible to connect other probes in parallel (up to 256 in theory) and to process all the measurements provided either independently or in an integrated manner. A non-exhaustive list of additional probes that can be coupled to the NODE biosensor includes pH, ORP, dissolved O2, conductivity, temperature, turbidity or flow rates.
Is the NODE biosensor a 4-20mA sensor?
No, the protocol used by default is Modbus® which has a higher resolution. This protocol also allows, depending on the application, to associate other probes in parallel on the same acquisition unit. However, if required, the use of a 4-20 mA converter can be included.
Can the data be sent to conventional telemetry systems (SCADA, PLC…) and supervision systems?
Yes, most systems are compatible. Depending on the supervision system, Data can either be uploaded directly or using dedicated adapters.