MARINE WATER TECHNOLOGY
Thalenhorststrasse 15 A
28307 Bremen, Germany
Phone: +49 421 53705 - 0
Fax: +49 421 53705 - 440
RWO - in cooperation with a leading European corrosion institute (SWEREA-KIMAB) and the classification society Germanischer Lloyd - has carried out thorough accelerated corrosion studies in treated full-salinity seawater with the CleanBallast ballast water treatment system. The tests simulated operation over an approximate entire lifetime of a ballast water tank/piping structure (approx. 40 years).
CleanBallast operates readily in waters with low and full salinity. The natural corrosiveness of those environments differs significantly, with, for example, full salinity (>32PSU) being a very corrosive media to common construction materials. It is also well known that larger quantity of active chlorine has further negative effect on corrosion, increasing the wear rate of non-passivated metals, etc.
The disinfection unit "EctoSys®" utilised by the CleanBallast system is based on electrochemistry, however operating very differently compared to, for instance, conventional chlorination or electrolysis systems using salt water (containing chloride), where a maximum production of active chlorine is desired. Instead, EctoSys® produces short-lived mixed oxidants, which together have a more striking and powerful effect compared to active chlorine. Thus, the EctoSys® is not dependent on chloride content (salinity), but produces oxidants directly from the water. The negative effects of active chlorine on corrosiveness can effectively be avoided.
Fig. 1: Natural decay of residual oxidants TRO produced by CleanBallast, T=22°C, pH=7.9, salinity 15PSU
In natural brackish and full-salinity seawater, besides the short-lived oxidants hydroxyl radicals the disinfection unit EctoSys® will produce only low levels (up to maximum 2mg/l) of more persistent oxidants, summarised as TRO (Total Residual Oxidants). Being oxidizing agents, such substances in higher concentrations are relevant for corrosive properties of water. TRO will decay via interactions with, for example, dissolved organic matter. Fig. 1 below illustrates a typical decay curve of TRO, showing that the natural blank level of 0.2 - 0.3mg/l of TRO is reached within approximately two hours.
RWO's cooperation with the leading European corrosion institute (SWEREA-KIMAB) and classification society Germanischer Lloyd (GL) included thorough corrosion studies in treated full-salinity seawater, simulating an approximate entire lifetime of a ballast water tank/piping structure (approx. 40 years). These studies were later recommended by the IMO technical group GESAMP-BWWG, as part of the guidance for other vendors developing ballast water treatment studies, to be included in their respective approval process (ref. MEPC 59/2/16, §4.5.1).
The tests included accelerated comparative studies (treated and untreated seawater) using both uncoated steel test specimens but more importantly test specimens with 2-coat paint systems according to NORSOK Coating 3B approved according to DNV Classification Note 33.1 class B1, common and approved for use in ballast water tanks, for instance, the Jotun system'Balloxy HB light'. The tests included parallel tests with both continuous exposure to the water and intermittent cyclic exposure of water and air. Intermittent exposure resembles better the real conditions in ballast water tanks and a worse corrosive case than continuous exposure. The tests were accelerated, that is, the exposure of the test panels was set to simulate an approximate entire lifetime of a ballast water tank/piping system, regarding initial maximum concentration of TRO and natural decay.
The evaluation of the exposed test panels was performed according to the following standards:
Based on the result of these tests, both SWEREA KIMAB and Germanischer Lloyd concluded that there are no additional corrosive properties of seawater treated with CleanBallast, compared to untreated seawater. Thus, the tests proved that the CleanBallast equipped with the EctoSys® disinfection unit does not increase corrosion in ballast water tanks. Furthermore, CleanBallast is certified and classified by the GL as compatible with epoxy-based ballast water tank coating systems.
RWO, Bremen, is a leading supplier of systems for water and wastewater treatment aboard ships and offshore rigs. The product programme encompasses the treatment of drinking and process water as well as bilge, ballast and wastewater. RWO is already the worldwide market leader in the treatment of bilge water. The company is part of Veolia Water Solutions & Technologies (VWS), subsidiary of Veolia Water, a leading design-and-build company and a specialized provider of technological solutions in water treatment. With over 9,500 employees in 57 countries, Veolia Water Solutions & Technologies recorded revenue of €2.5 billion in 2009.
Veolia Water, the water division of Veolia Environnement, is the world leader in water and wastewater services. Specialised in outsourcing services for municipal authorities, as well as industrial and service companies, Veolia Water provides water supply to 95 million people and wastewater disposal to 66 million. With 95,789 employees in 66 countries, its 2009 revenue amounted to €12.5 billion.
RWO GmbH - Marine Water Technology
Saskia Skovdal, Marketing & Communications
Thalenhorststrasse 15A, 28307 Bremen, Germany
phone : +49(0)421 53705-214, fax: +49(0)421 53705-442
Veolia Water Solutions & Technologies
Germany, Austria, Switzerland
Stefan Jakubik, Marketing & Communications
Lueckenweg 5, 29227 Celle, Germany
phone : +49(0)5141 803-174, fax: +49(0)5141 803-385