Chinese
Spanish
Wastewater Petroleum Determination Method: Principles of UV Fluorescence and Online Monitoring Practice
Petroleum pollutants are among the most destructive chemical contaminants in aquatic environments. Globally, hundreds to thousands of tons of petroleum enter water bodies annually through ship spills, industrial discharge, port operations, and pipeline leaks, making petroleum the second-largest water pollutant after heavy metals, with especially severe impacts in marine environments.
Petroleum in water exists in various forms, including floating oil, dispersed oil, emulsified oil, dissolved oil, and oil-solid complexes adsorbed on suspended particles. These different forms affect water bodies in multiple ways: floating oil films block oxygen exchange between air and water; dispersed and emulsified oil consume dissolved oxygen during microbial oxidation, causing hypoxia and black-odor water; oil coating fish gills causes suffocation and high deformity rates in juvenile fish; long-term pollution impairs water self-purification, threatening the entire aquatic ecosystem.
Accurate determination of petroleum content in water is therefore a core task of environmental monitoring. However, due to the complex composition of petroleum (alkanes, aromatics, cycloalkanes, etc.), varying wastewater sources and industrial effluents, and the lack of uniform standard substances, traditional methods often face low extraction efficiency, high interference, and complex operations.
In recent years, the UV fluorescence method has emerged as an effective solution for online monitoring due to its high sensitivity, no complex pretreatment, and rapid response.
Forms of Petroleum in Water and Environmental Hazards
Floating oil: forms a film on the water surface, thickness from micrometers to millimeters, severely hindering oxygen diffusion.
Dispersed oil: tiny oil droplets suspended in water, easily degraded by microbes but consume large amounts of oxygen.
Emulsified oil: stable oil-water emulsion, difficult to separate naturally, persists for long periods.
Dissolved oil: small amounts of aromatic hydrocarbons dissolved in water, highly toxic.
Oil-solid complexes: oil adsorbed on suspended particles, settling or migrating with particles.
These forms collectively reduce water transparency, inhibit photosynthesis, and decrease biodiversity. In sensitive coastal or estuarine areas, spills can cause massive short-term fish, shrimp, and shellfish deaths, and long-term bioaccumulation toxicity.
Core Principle of UV Fluorescence Petroleum Determination
The UV fluorescence method relies on the fluorescent properties of polycyclic aromatic hydrocarbons (PAHs) and other aromatic compounds in petroleum.
When oil molecules in water are irradiated with UV light of specific wavelengths (usually 220–400 nm), electrons in the molecules transition from the ground state to an excited state. Excited electrons then return to the ground state, emitting longer-wavelength fluorescence (Stokes shift). Fluorescence intensity is proportional to the aromatic hydrocarbon concentration.
In practice:
UV light source emits a collimated beam, filtered to a precise excitation wavelength, illuminating the flow cell or sensor probe.
Aromatic hydrocarbons in water absorb energy and emit fluorescence.
Fluorescence passes through an emission filter (e.g., 300–400 nm) and is detected by a high-sensitivity photomultiplier or photodiode.
The system eliminates interference from Rayleigh and Raman scattering, ensuring a linear relationship between fluorescence signal and oil concentration.
This method is extremely sensitive to aromatic components in mineral oil, achieving ppb (μg/L) detection limits.
Advantages of UV Fluorescence Compared to Traditional Methods
No extraction pretreatment required: traditional methods use carbon tetrachloride or n-hexane, time-consuming, high solvent use, risk of secondary pollution; fluorescence measures raw water directly.
Low interference from turbidity or water treatment chemicals: precise optical filters suppress scattering; most flocculants or defoamers produce negligible background fluorescence.
Fast response: signal output in seconds, suitable for continuous online monitoring.
High sensitivity: ppb-level detection suitable for clean seawater, nearshore waters, and early spill warning.
Eco-friendly and reagent-free: low operating cost, no chemical waste.
These features make UV fluorescence ideal for industrial discharge outlets, refineries, ports, ballast water, and offshore platforms.
Nexisense Y517-A Oil-in-Water (PAHs) Sensor: Reliable Online Solution
Wide measurement range with good linearity, suitable from clean seawater to industrial wastewater.
Short response time with real-time data output.
Probe made of highly corrosion-resistant material, IP68 rated for long-term immersion.
RS485 digital interface with MODBUS protocol, compatible with PLC, SCADA, or cloud platforms for remote monitoring and alerts.
No chemical reagents required, zero secondary pollution during operation.
Long maintenance interval and simple calibration, reducing operational burden.
Y517-A can be deployed at wastewater treatment plant outlets, industrial cooling systems, port intake waters, and marine monitoring buoys for timely spill warning and reliable environmental compliance data.
Frequently Asked Questions (FAQ)
Do UV fluorescence results match national IR methods?
They target different petroleum components (UV fluorescence responds to aromatics, IR responds to C-H bonds); correlation is good in mineral oil-dominated wastewater and they can be used complementarily.
Does high turbidity affect measurement accuracy?
Y517-A uses precise optical filters to suppress scattering; maintains high accuracy in moderate turbidity (<200 NTU); pre-filtration recommended for very high turbidity.
Are water treatment chemicals a concern?
Most common chemicals (e.g., PAM, PAC) produce negligible fluorescence; site-specific validation recommended for unusual chemicals.
Detection limit?
Typical mineral oils detectable at ppb-level (1–10 μg/L), depending on aromatic content.
How to perform field calibration?
Two-point calibration using standard oil solutions or zero water; simple operation, typically monthly.
Conclusion: Accurate Monitoring to Protect Water from Petroleum Contamination
Petroleum pollution is persistent and hidden; early detection and fast response are critical. UV fluorescence provides high sensitivity, no pretreatment, and real-time online monitoring.
The Nexisense Y517-A Oil-in-Water sensor transforms advanced fluorescence technology into a reliable product, enabling continuous tracking and precise management of petroleum pollutants for enterprises, monitoring agencies, and environmental authorities. In today’s strict water protection environment, using scientific and eco-friendly monitoring tools is not only a compliance requirement but also a responsibility. Together, accurate data helps maintain clean and healthy water.
