Feature 3 | BALLAST WATER TREATMENT
Te flow of seawater through the system leads to the gradual build-up of biological residue inside the tubes of the UV unit. To counter this problem, Cathelco has developed an innovative ‘ball cleaning system’. “We looked for a solution which was
capable of cleaning the quartz sleeves and all of the surfaces within the UV chamber. It also had to be completely chemical free. Tis led us to the cleaning in place (CIP) system using foam balls which is proven technology and has been used for cleaning applications in power stations for many years”, Field tells Ship & Boat International. When the cleaning cycle is automatically
initiated, the UV chambers are isolated from the rest of the BWT system by valves. A separate pump is activated enabling specialised foam balls to be introduced into the reactor line from a reservoir. Tese gently polish away any residue that
may have accumulated on the surface of the quartz tubes that surround the UV lamps as well as cleaning the inside of the chamber. Te foam balls are automatically reclaimed
at the end of cleaning cycle and the cleaning system is isolated and the main system is made ready for the next ballast water operation. Tis means the system remains chemical
free and it removes the risk of damage to the quartz tubes from mechanical cleaning methods. Te Cathelco BWT system has a choice of
two filter types with the capacities to handle from 50m3
/h to 1,200m3 /h with a 40micron
screen mesh. The filters are self-cleaning; on the intake of ballast water, the system uses automatic back flushing, discharging the filtered material back into the original ballasting site. Tey can also continuously filter ballast water during the cleaning process.
Control options Functions such as ballasting, deballasting and by-pass modes are controlled and monitored through the BWT system’s control panel. Cathelco has designed the system so that it can be accessed in a number of different ways according to vessel size and customer preference. Te control panel is equipped with a touchscreen interface and the system can also be accessed via a remote control interface to allow the user to view and operate the system from a more convenient location. Te BWT system health is closely monitored through the control system, with the ability to
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check aspects such as filter and UV chamber performance and the initiation of cleaning cycles. Te system is fully integrated with the ship’s computer systems with mimic screens
The central control system controls and monitors the BWT system’s functions, including ballasting and re-ballasting and monitoring system health
using part of the vessel’s management system. In compliance with IMO requirements, all data from the BWT system is logged through the control system. SBI
IMO Final Approval status for Wärtsilä’s AQUARIUS EC
Final Approval status from the IMO’s Marine Environment Protection Committee (MEPC) has been awarded to Wärtsilä for its Aquarius EC ballast water management system. The approval was granted at the MEPC’s 65th session on 13 May 2013 as part of the Committee’s agenda covering “harmful aquatic organisms in ballast water”. Basic Approval had been granted in October 2012. Final Approval is required for systems using an active substance during the ballast water treatment process, and is based upon examination of full-scale prototype test data and all required supporting documentation on aspects such as risk and safety to the ship, crew, general public, and the environment. Aquarius EC is a modular ballast water management system in which ballast water treatment is achieved through a simple and efficient two-stage process. During the first stage, upon uptake sea water is first passed through a back washing filter and passed through a static mixer; here, in the second stage of the treatment process, the disinfectant generated from the side stream electrolysis unit is injected to ensure a maximum level of 10 parts per million (ppm) in the treated ballast water.
During discharge the filter is bypassed and any residual oxidant in treated ballast water is monitored before being discharged overboard. If required, treated ballast water is neutralised by injecting sodium bisulfite into the main ballast line during discharge. Neutralisation effectiveness is continuously monitored to ensure compliance with MARPOL discharge limits. A key element of the Final Approval submission was an investigation covering the impact of treated ballast water on coated and uncoated materials. A full Type Approval certificate for the Wärtsilä Aquarius EC system is expected by end of July this year. “Gaining IMO Final Approval status has involved an extremely stringent review and investigation process, and we are naturally very delighted that the Wärtsilä Aquarius EC ballast water management system has successfully met all the requirements of the process. This represents an essential and extremely significant milestone in offering the marine industry a safe, flexible, and efficient means of treating ballast water,” says Joe Thomas, director, Wärtsilä Ballast Water Management Systems.
Ship & Boat International May/June 2013
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