Investigating the potential of remote ultraviolet sensing for real-time produced water monitoring: a lab-scale study

Traditional produced water discharge monitoring techniques involve ‘end of pipe’ sample collection and analysis, offering a snapshot of discharged fluid composition and predicting the marine environmental risk through dispersion models. This study presents a proof-of-concept analysis of using ultraviolet remote sensing for real-time produced water monitoring, enabling data capture directly within the marine environment. Ultraviolet imaging was used to quantify the sheen intensity of artificially prepared produced water standards and to evaluate the relationship between image signal intensity and total petroleum hydrocarbon concentration over time. A statistically significant relationship was observed between signal intensity and total petroleum hydrocarbon concentrations, with TPH quantification down to 1.95 mg/L within 20 min. This indicates the potential for ultraviolet remote sensing in real-time operational monitoring. Furthermore, the study found that in batch systems, ultraviolet sensors are most effective for detecting total petroleum hydrocarbon within the first 5 min after the mixture reaches the surface of the water. This does not preclude the technique from being useful for its intended purpose at offshore facilities even though there may be ongoing discharge and surfacing of wastewater plumes. Proposed deployment methods involve using sensors mounted on unmanned autonomous vehicles (drones) to monitor for plumes within a discharge zone out to a compliance point and inform any necessary management actions to appropriately mitigate environmental risks. Future research should explore the impacts of physical factors such as waves, currents, and ambient light on ultraviolet sensor performance in real-world conditions to further evaluate its operational suitability.