Page 47: of Maritime Reporter Magazine (February 2014)
Cruise Shipping Edition
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www.marinelink.com 47 improve treatment performance.
As shown in Figure 2, the global mar- ket for BWT systems is dominated by two treatment technologies - UV and electrochlorination. These are manu- factured by 26 equipment suppliers and compose 85% of the approximately 1,500 IMO type-approved BWT systems installed to date. The basic process trains are generally described below:
UV Disinfection: This is a two-stage treatment process with a pressure-rated fi lter unit (typically with micron-rated disks or membrane elements) to remove sediment and larger organisms, followed by a UV disinfection unit to inactivate smaller plankton, bacteria and viruses.
No chemicals are required to operate the system. During ballasting, water is typi- cally processed through both the fi lter and UV stages as water is pumped into the ballast tanks. Solids captured by the fi lters are discharged at the ballasting lo- cation. During de-ballasting, the fi lter is typically bypassed and water is treated by the UV unit only before discharging overboard.
Electrochlorination: This is a two- stage treatment process with a micron- rated pressure fi lter or strainer followed by an electrochlorination unit. The latter is essentially an on-demand chemical system, which uses electrolytic cells to generate a sodium hypochlorite (bleach) solution from seawater and electricity.
Some treatment systems pump the entire ballast water fl ow through the electro- lytic cells, whereas others use a small slipstream to generate a concentrated hypochlorite solution, which is then re- combined with the main fl ow. During ballasting, water is processed through both the fi lter and electrochlorination unit as water is pumped into the ballast tanks. A chlorine residual (or residual oxidant) is maintained in the tanks for a minimum contact time (typically a few days) to improve disinfection and eliminate regrowth of organisms during transit. During deballasting, a neutraliza- tion chemical (e.g., sodium bisulfi te) is added to the water to remove the oxidant residual as it is pumped overboard. Note that this type of system cannot be used in freshwater areas such as the Great Lakes because it requires salinity for hypochlo- rite production.
Complying with the New Regulations
The new BWM regulation will in- crease costs for shipowners/operators to evaluate, install, operate (including ad- ditional record-keeping) and maintain
BWT systems with regulatory compli- ance dates, starting now for new build vessels and at the next scheduled dry- dock for many existing vessels. They must therefore quickly become familiar with the new requirements, risks of non- compliance and necessary steps to bring individual ships or fl eets into regulatory compliance.
For owners/operators of seagoing com- mercial vessels, most important will be to select an appropriate type-approved
BWT system that is compatible with the ship’s existing ballast water system and can be operated to ensure compliance safely by the crew. Key design consid- erations for BWT system selection in- clude: • Ballast pump capacities and operat- ing pressures, • Ballast tankage volume (if required for disinfection contact time), • Available space for the BWT equip- ment, • Uptake and discharge piping ar- rangements, • Chemical storage location (if re- quired), • Discharge sample location (for
USCG inspection use), • Ship routes (and associated ballast water quality conditions), • Integration of the BWT system con- trols into the ship’s ballast control system, • Training requirements for crew members.
BWT system selection is made more complicated in that the USCG has not type approved or certifi ed any systems yet, although it plans to over the next year or two. In the meantime, AMS-ac- cepted systems must be used with only a fi ve-year regulatory compliance hori- zon, with no certainty that they will ul- timately be approved by the USCG for long-term compliance with the BWM regulation.
Given the complexity and uncertainties of the BWM regulatory requirements, tight implementation schedule, system installation challenges, and the myriad of BWT systems on the market, many ship owners are hiring a qualifi ed engi- neering fi rm to assist in selection of the most appropriate BWT system and work with the selected equipment supplier to design and install the BWT system on a particular ship or fl eet. The planning, engineering and installation of the BWT system needs to be carefully coordinated with the vessel drydock projects.
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The new BWM regulation will increase costs for ship owners/operators to evaluate, install, operate (including additional record-keeping) and maintain BWT systems with regulatory compliance dates, starting now for new build vessels and at the next scheduled dry-dock for many existing vessels.
The Authors
Christopher R. Schulz, P.E., is Senior Vice
President at CDM Smith. Chris Schulz has over 30 years of experience in the planning and design of water treat- ment facilities in the United States and throughout the world. He served on the expert review panel for the USCG’s Ship- board Technology and Evaluation Pro- gram (STEP), which evaluated prototype ballast water treatment systems in ship- board environments. Randy Kullmann is
Vice President at CDM Smith. Kullmann has over 27 years of experience in con- sulting, engineering, construction and operations. His experience spans all aspects of water treatment and he has been leading CDM Smith’s marine ser- vices, including compliance, information and safety management, as well as wa- ter treatment.
Excerpted from an article published in the Q4 edition of Maritime Professional
MR #2 (42-49).indd 47 2/4/2014 4:43:26 PM
