Tired of Talking Green: Sizing Up Ballast Water Treatment System Offerings

By Wendy Laursen

Discussing maritime technology - without the marketing clichés

Greater transparency is needed from the manufacturers of ballast water treatment systems, says Tim Wilkins, Singapore based environmental manager for Intertanko. “There is still a lot of naivety out there. There are still a lot of people asking questions that manufacturers don’t seem to be answering.”

Selecting from a diverse range of technologies and installing and operating equipment that has had little shipboard experience for the industry to draw on is a challenge, and some shipowners are experiencing problems. “Some systems have gone through the type approval process and been approved but fall short when they’ve been installed on vessels.” The real power requirements of systems have been misjudged and problems have been encountered with filter operation.

There is limited experience with the installation of systems, particularly for larger tankers with ballast requirements of around 5,000m3/h, and it is often difficult to fully assess the accuracy of the quoted power consumption. “In some cases it is not clear whether or not manufacturers are including any additional machinery, pumps or control equipment above and beyond that of the main system.” The difficulties are exemplified by the range of power quoted for systems of around 5,000m3/h which range from under 100kW to over 1,000kW although requirements in the range of 300kW and 600kW are common.

Power consumption varies considerably with the type of treatment technology, although significant differences between two similar system types can also be found. Low salinity or low sea water temperature can significantly increase power consumption some electro-chemical treatment systems. Therefore, diesel generator capacity may need to be increased and classification requirements for a standby diesel generator during normal operation or sea load should be taken into consideration.

Some treatment systems may have issues when it comes to the minimum pumping capacity. For example, hydrocyclone systems may require a minimum amount of water flow to work effectively. Pressure drop is an important parameter that, in some cases may require the replacement of the ballast pumps. Most manufacturers are advertising a ‘low’ pressure drop. Figures below 1bar or as high as 3bar have been quoted. Filter backflushing can prolong the treatment process so the maximum treatment rates quoted by the manufacturer may have to be 10-15 per cent greater than actual rates required once the back flush is factored into the equation.

While it is necessary to avoid exceeding the treatment capability of the system during peak loads, there is the risk of over-sizing the system installation which will result in unnecessary capital and operational costs. Capital costs for a 5,000m3/h system are typically $1.5-2.5 million. The total costs after delivery, installation and commissioning are less well known as are the added costs for retrofits. Operational costs vary significantly but are rarely less than $20,000 a year and can often exceed $50,000 per year for a 5,000m3/h system.

Maintenance needs must be considered at the installation design stage to ensure there is adequate access space around the equipment. The footprint is of paramount importance for retrofits and can greatly affect the selection of the system to be installed. Based on currently available quotes and drawings, the size of most 5,000m3/h and above systems is 20-40m3 in total volume, although some are significantly larger. At present, very few systems are estimated to be less than 20m3. It is also estimated that most systems of 5,000m3/h and above weigh around 10,000kg, although this varies widely with a range of 2,000-5,000Kg often being quoted.

Having petitioned Intertanko members about their experiences, Wilkins has now published a guide – Guidance on Ballast Water Management Systems for Tankers. “The learning curve is almost vertical right now particularly as owners are taking delivery of tankers with new systems installed. The experience being gained from these new installations will be invaluable and we hope that the industry will continue to share that experience,” says Wilkins.

If you would like to propose viewpoints or topics for future articles, please contact Wendy Laursen: [email protected]