Why are continuous nitrate sensors needed?
Nitrate in water can vary in three dimensions and in time due to many stressors
Sampling once per year, seasonally, or monthly does not provide adequate information about the variability of nitrate in the environment
NO3-N Measuring principle
HydroTech’s new low-cost nitrate meter by Trios
Based on the device platform concept of TriOS sensors like OPUS, LISA and VIPER, TriOS introduces NICO: a low-cost UV photometer for the determination of nitrate. The four detection channels enable a precise optical determination of nitrate by absorption, taking into account turbidity and organic substances that pose a problem for many products currently on the market.
An internal temperature correction additionally increases stability of the measured values.
Equipped with our G2, G2plus or G2 Air interfaces with web browser configuration and internal data logger NICO includes features that are much more advanced than those of comparable devices available on the market.
The unified platform of all TriOS photometers also facilitates a standardized spare parts and consumables system, which allows the use of a wide range of accessories for our devices. Furthermore the cutting-edge G2 interface enables quick integration into third-party systems
The science behind the NICO and OPUS
The NICO and OPUS operate on the principle that nitrate absorbs radiation in the ultra-violet (UV) region of the electromagnetic spectrum at a characteristic wavelength of about 220 nm.
Pulses of UV light are transmitted through a sample path of water (typically 20 mm), received and spectrally analysed. The amount of UV absorbed by the water sample is proportional to the concentration of nitrate in the water. The processor compares the intensities of the two received beams, derives the nitrate concentration and sends this to a recorder such as a web-enabled datalogger.
The sensor may be located in a stream, or alternatively, above water-level and have water pumped to it via a flow cell. The optical windows the UV passes through, are usually made from transparent quartz. This can resist abrasion by the hardest materials likely to be present in the water stream.
These windows can be automatically cleaned by compressed air, a built-in wiper or ultrasonic vibrator. Monthly site visits enable a physical verification sample and also provide an opportunity to inspect and clean the instrument manually.
Strengths and weaknesses of UV multispectral sensors
- Pros:
- Precise, accurate and stable
- Inexpensive to operate
- Minimal maintenance
- Measure over a wide range
- No chemicals needed
- Robust and durable
- Fast response
- Spectra may also detect e.g. turbidity
- Easy to deploy… ‘plug and measure’
- Factory pre-calibration (may need ‘local water’ calibration)
- Independent of water temperature
- Cons:
- Power use: Requires power onsite
- Other constituents (notably CDOM and turbidity) can interfere with optics
Benefits:
- Proven UV-absorption method
- Without sampling and preparation of test samples
- Real-time sensor
- Without reagents
- Optical window with nano coating
Applications:
- Sewage treatment plants
- Environmental monitoring
- Drinking water monitoring
Technical Specifications:
- Measurement technolog:
- light source : Xenon flash lamp
- detector: 4 photo diodes + filter
- Measurement principle: Attenuation
- Optical path: 0.3 mm, 1 mm, 2 mm, 5 mm, 10 mm, 50 mm
- Parameters: NO -N, NO NO -N, NO (calibrated with NO standard solution)
Range and accuracy:
The optical path on the NICO can be modified by the end user from 0.3 mm, to 1 mm, 2 mm, 5 mm or 10 mm. The optical path size determines the range and the accuracy of the sensor.
Optical Path Size (mm): Range (NO3-N) ; (NO3) / Accuracy (NO3-N) ; (NO3)
0.3mm: (0-200) ; (0-886) / ± (5% of the reading + 3.3) ; (5% of the reading + 14.5)
1mm: (0-60) ; (0-266) / ± (5% of the reading + 1) ; (5% of the reading + 4.4)
2mm: (0-30) ; (0-133 / ± (5% of the reading + 0.5) ; (5% of the reading + 2.2)
5mm: (0-12) ; (0-53) / ± (5% of the reading + 0.2) ; (5% of the reading + 0.88)
10mm: (0-6) ; (0-26.6) / ± (5% of the reading + 0.1) ; (5% of the reading + 0.44)
50 mm: (0-1.2) ; (0-5) / ± (5% of the reading + 0.02) ; (5% of the reading + 0.09)
For detailed ranges and accuracies for NICO® click here
Turbidity compensation: Yes
Data Logger: ~ 2 GB
Reaction time T100: 20S
Measurement interval: ≥ 10 s
Housing material: Stainless steel (1.4571/1.4404) or titanium (3.7035)
Dimensions (L x Ø): ~ 470 mm x 48 mm (10 mm path); ~ 18.5“ x 1.9“ (with10 mm path)
Weight:
- stainless steel: ~ 3 kg (~ 6.6 lbs)
- titanium: ~ 2 kg (~ 4.4 lbs)
Interface: digital: Ethernet (TCP/IP); RS-485 (Modbus RTU)
Power consumption: ≤ 7W
Power supply: 12...24 VDC (± 10 %)
Required supervision: Typically ≤ 0.5 h/month
Calibration/maintenance interval: 24 months
System compatibility: Modbus RTU
Warranty: 2 years
Max. pressure:
- with Subconn: ~ 435 psig
- with fixed cable: ~ 435 psig
- in flow unit: ~ 14.5 psig at 0.5 to 1.0 gpm
Protection type: IP68
Sample temperature: +36 °F to +104 °F
Storage temperature: 4 °F to +176 °F
Inflow velocity: 0.1...10 m/s (0.33 to 33 fps)
