Clean discharge, cleaner seas

IMO-approved solution helps transformer station save time and costs when discharging sewage water

Wind parks are connected via an offshore transformer station, which transports the power through a land-based cable. Storms and heavy rain make it difficult to avoid accumulations of sewage water on the platform. To meet the IMO standards and ensure that contaminated water is not discharged, we have helped several of our customers with an IMO-approved solution from Brannstrom.

An expensive affair

At the transformer station, rain, drain, and sewage water are separated from oil and often collected in a tank. When the tank is full, the water is pumped on board a ship that sails and pumps the water ashore, where it is cleaned and discharged or delivered to a wastewater plant.

Even though this process often is coordinated so the ship has other tasks while picking up the water tank, it is an expensive affair since it involves around 10-20 cubic meters of sewage water. In addition, periods with powerful storms and large amounts of rain result in a quickly filled tank, and in the worst case an undocumented amount of sewage water will be discharged over the edge of the transformer station, which is associated with huge fines and costs for calculations of the extent of the overflow.

IMO-approved solution from Brannstrom

Therefore, we have helped several of our customers with an IMO-MEPC.107(49) approved solution from Brannstrom, called GreenMon. GreenMon ensures accurate monitoring of oil content in muddy/dirty water with high turbidity and no need for frequent re-calibration. The Oil Content Monitor illuminates the water with a UV ray, logs the readings for future documentation, and displays the data in real-time, numerically, or as a graph.

If the values are below the permitted 15 ppm, the instrument sends a signal to a valve that opens and discharges the water directly to the sea. If the values are above the permitted limit, the valve close, and another valve, which ensures that the water is led back to the tank, opens. The last-mentioned scenario is extremely rare and is usually a sign of problems with the instrument’s separator since it has not been able to clean the water sufficiently.

Free-falling principle makes the solution maintenance free

The GreenMon Oil Content Monitor is based on Raman scattering and fluorescence spectroscopy of a free-falling
sample water jet. The free-falling-water-jet measuring principle is unique, as it means that the water flows in a fixed water jet inside the tube. Therefore, there is no sensor glass fouling, no risk of the measuring cell being filled up with water (which can be problematic in freezing weather), or scaling demanding frequent cleaning, which makes GreenMon maintenance-free and ideal for demanding 24/7 applications.

Thereby, the customer achieves:

Less time spend on coordination – since the customer does not have to spend time coordinating ships that must pick up and dispose of the contaminated sewage water.
Valid documentation – since the discharged quantity is logged and documented in accordance with IMO legislation.
A maintenance-free solution – since the water is not in contact with the measuring tube.
Reduced costs – since the cost to ships picking up contaminated water and potential fines for discharging undocumented overflows are eliminated.

Final commissioning

Most recently, our Service and Commissioning Engineer has carried out a final commissioning of the above-mentioned solution on a large wind power transformer station located in English Waters. The commissioning job included a review of the mechanical installation and test of signals.

During his visit, he discovered a missing marking on a valve, which in the worst case could have led to a measuring cell full of water, if the valve had been closed. However, he was able to point out the error and the valve is now sufficiently marked.