Monitoring Hydrocarbons in Bilge Water
Various processes onboard ships, such as machinery wash-down, maintenance, and leakage generate oily wastewater. This contaminated water flow collects in the bilge of the ship. Marine diesel, lubricating oils, grease, as well as garbage may be present in bilge water. The bilge water is discharged overboard, with oil and grease concentrations in the discharged water limited by national and international regulations.
In the United States territorial waters, the U.S. Coast Guard (USCG) limits the discharge of oil and grease in bilge water to 15 ppm, measured by the U.S. Environmental Protection Agency (EPA) oil and grease measurement method. The USCG further limits bilge water and oily discharges that cause a visible sheen on the water. In Canadian inland waters, the Canadian Coast Guard limits the discharge of oil and grease in bilge water to 5 ppm. Bilge water discharges in international waters are limited to 15 ppm by the International Maritime Organization (IMO). Ship operators who violate the discharge limits are subject to large fines by the jurisdictional authority. Recently, cruise ship lines have incurred record fines for discharge violations.
The maritime industry needs an effective and accurate analyzer to monitor the oil concentration in the bilge water before discharge. On-line analyzers manufactured by several companies have been employed for this application, yet to date, none of these analyzers have been effective or accurate.
Most analyzer’s monitor oil in water by using a contact flowcell through which the bilge water flows. The flowcell is regularly fouled by oil and other material. Even mechanical wipers cannot keep the flowcell free of fouling. Most analyzers require considerable maintenance for proper operation or measure the oil concentration indirectly by turbidity, which is subject to interference by solid material present in bilge water.
The TD-4100 On-line Oil in Water Monitor eliminates the problems associated with other bilge water monitors. The TD-4100 uses a non-fouling, non-contact flowcell to monitor the hydrocarbon concentration by fluorescence which is directly proportional to the oil concentration. The non-fouling, non-contact flowcell eliminates contact between the water and optical windows, thereby preventing fouling. The TD-4100 can be calibrated with a CheckPoint solid standard, which allows quick calibration checks and re-calibration of the analyzer without the need for preparing hydrocarbon solutions.
Bilge water monitors require certification. The TD-4100 and TD-4100XD are certified by the USCG as a Oil Content Meter ? 15 ppm bilge alarm according to Regulation 16(5) of Annex I to Marpol 73/78. The solid-state alarm relays of both instruments can activate control devices and/or alert operators. The TD-4100XD received approval by the American Bureau of Shipping (ABS) for use on ABS classed vessels. The USCG presently uses a Turner Designs Model 10-AU instrument for monitoring and tracking oil spills. The TD-4100 and TD-4100XD utilize the same fluorescence technology as the model 10-AU.
The TD-4100 is certified by the Canadian Coast Guard as a 5 ppm bilge water alarm and is currently being deployed onboard Canadian naval vessels. The TD-4100 is also certified to meet the Canadian Coast Guard?s inland waters requirement of 5 ppm bilge water alarm.