Characterizing shipboard bilgewater effluent before and after treatment

Area of Science:

• Marine environmental science
• Environmental engineering
• Pollution control technologies

Background:

• Operational discharges from oceangoing vessels, including bilgewater, introduce oil and pollutants into marine ecosystems.
• Bilgewater, a mixture of oily fluids and pollutants, requires treatment by oily water separators before discharge from larger vessels.
• Marine pollution from vessel operations poses risks to marine life, terrestrial ecosystems, and human health.

Purpose of the Study:

• To evaluate the effectiveness of bilgewater treatment systems in reducing oil pollution from oceangoing vessels.
• To compare shipboard performance of treatment systems with land-based type approval data.
• To assess the accuracy of shipboard oil content monitors and identify additional pollution reduction benefits.

Main Methods:

• Analysis of land-based type approval data for 20 bilgewater treatment systems.
• Collection and analysis of bilgewater influent and effluent samples from three operational vessels.
• Comparison of shipboard effluent concentrations with regulatory standards and land-based performance data.
• Evaluation of shipboard oil content monitor accuracy against laboratory analytical results.

Main Results:

• Based on type approval, 15 out of 20 treatment systems performed below the 5 ppm oil discharge limit.
• Shipboard performance data verified the effectiveness of the three sampled treatment systems, aligning with type approval.
• Shipboard oil content monitors exhibited variability, leading to inaccurate readings (false negatives/positives).
• Treatment systems generally reduced other pollutants, excluding some heavy metals.

Conclusions:

• Bilgewater treatment systems are effective in meeting oil discharge regulations.
• Variability in shipboard oil monitors necessitates improved monitoring accuracy.
• Treatment systems offer broader pollution reduction benefits beyond regulated oil content.