How to select the TOC BOD COD NO3-H, DOC water quality detector?
Release time:2025.11.27
How to select the TOC BOD COD NO3-H, DOC water quality detector?
The following is the comparison of the technical advantages of UV spectroscopy and electrochemical method (including ion selection method) in water quality detection, combined with specific indicators (TOC, BOD, COD, NO ₃ -N, DOC):
1. Advantages of UV-visible spectroscopy
1. Core principles
Based on the absorption characteristics of matter for a specific wavelength of light (such as UV 254 nm, visible area), quantitative analysis by the Lambert-Beer law.
2. Applicable indicators and advantages
Metric | Superiority | Typical application scenarios |
TOC | High-temperature catalytic oxidation + non-dispersed infrared detection (NDIR), no chemical reagent, fast detection speed (<10 minutes) | Surface water, drinking water, industrial pure water |
COD | Potassium dichromate digestion + visible light spectrophotometry (e. g., HJ 828-2017, standard), mature and stable | Municipal sewage, industrial wastewater |
DOC | Ultraviolet absorption method (UV 254 nm) direct measurement, low cost, suitable for long-term online monitoring | Drinking water, and groundwater |
NO₃⁻-N | UV 210 nm direct absorption method, without reagent, suitable for cleaning water (such as drinking water, surface water) | Environmental protection monitoring, agricultural irrigation water |
2. Sub-index comparison and selection suggestions
1. TOC
- Ultraviolet method: suitable for clean water body (such as drinking water), low cost, low maintenance.
- Electrochemical method: suitable for high salt or complex matrix (such as industrial wastewater), strong anti-interference ability.
2. BOD
- Electrochemical method (microbial sensor): the only direct measurement of BOD, suitable for process optimization (e. g. sewage treatment plant).
- Alternative: UV method cannot directly measure BOD and should be estimated indirectly through TOC / COD.
3. COD
- UV spectrophotometry: meet the standard method (such as HJ 828).
- Electrochemical method: fast response, suitable for online control (such as industrial circulating water).
4. NO₃⁻-N
- Ulv method: preferred for cleaning water, no reagent required.
- Ion selection electrode method: anti-interference scheme for complex water samples (such as wastewater).
5. DOC
- Ultraviolet method: reagent-free, long-term stability, suitable for drinking water monitoring.
- Electrochemical method: no application advantage, usually using ultraviolet method.
3. Summary: Key factors of method selection
Water sample type:
- Clean water body UV method (TOC, DOC, NO ₃ -N)
- Complex wastewater electrochemical method (BOD, COD, NO ₃ -N)
Testing requirements:
- Fast real-time control electrochemical method (e. g., BOD sensor)
- Compliance test UV spectrophotometry (e. g. COD standard method)
Cost and maintenance:
- Low maintenance requirement UV method (no reagent)
- High-precision demand electrochemical method (e. g., ion-selective electrode)
Example scenarios:
- Aeration tank monitoring of sewage treatment plant: electrochemical BOD, sensor + UV COD instrument
- Early warning of drinking water source area: joint monitoring of UV NO ₃ -N + UV DOC
- Treatment of industrial wastewater: electrochemical COD + ion-selective electrode NO ₃ -N
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