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Challenges in the Installation and Operation of Ballast Water Treatment Systems
Dr. John Kokarakis
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The process
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Questions to reply
► Enough capacity? Limitations
► Enough power?
► Safety? Gas Dangerous Zones
► Hydrogen removal?
► Monitoring-Alarms
► Ventilation?
► Low Salinity-Low Temperature (full flow)
► Training
► Risk assessment/HAZID
► The after peak problem-Harmonization
► Holding time, Dosage, Discharge limits
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Installation questions: WHERE, HOW, WHAT
► Find a suitable location (minimize pipe and electrical runs)
► Integrate electrically into vessel system
► Engineer system for Class approval
► Integrate with existing pumps & eductors
► Isometric piping drawings (prefab)
► Usually available only 2D-Data
► Organization & logistics to minimize off-hire
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Critical factors to installation
► Classification of the ship
► Type of vessel (tankers: additional safety issues)
► Standards (DIN, DIN EN ISO, JIS, ...) differ in dimensions of joints, pipes etc.
► Small ships have less space in engine rooms
► Operating areas have to remain free (Gangway min. 600x2000 mm)
► Room height has to be considered
► Entrance to existing equipment for operation and maintenance,
► Stairways, emergency exits, man holes have to be kept free
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Critical factors to installation
► Operating space for screws, bolts, nuts, handles, ...
► No connections of fluid pipes above electrical devices
► Additional space for insulation
► Systems to be avoided (thermal oil)
► No welding close to / on tanks because of tank coating
► Standard pipe elbows with bending radius of 1xdiameter or 1,5xdiameter (1D, 1.5D)
► Angles of pipes always multiple of 15°
► Minimum distances between pipe bends due to fabrication
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Documents for Class Approval
► P&ID of the ballast system including any connections to other
systems (bilge, fire etc.)
► Arrangement of all units and auxiliary systems with critical
importance for the functioning of the treatment system.
► Main Switchboard modification
► Updated electric load tables for all conditions
► Evaluation if new short circuit calculations are necessary.
VFD will not for instance affect the short circuit currents.
► Control system block diagram and power supply arrangement
► List of controlled and monitored points/sensors
► Risk assessment
► Stability calculations .Total weight added must be reported.
► Reinforcements needed due to the added elements.
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The limitations
► Treatment process is limited by water temperature and salinity to achieve optimum performance. A heat exchanger might be used to raise the water temperature.
►
►
► Ballast can become contaminated by the
residue/sediment in the tank. This may
necessitate the treatment during de-ballasting.
► Management of dangerous gases is an important parameter to consider when installing BWTS.
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Hydraulic constraints
► An orifice might be utilized to limit
flow through the BWT system.
► In case of pump upgrade, assess
the suitability of existing
piping/flanges to the higher
pressure in the system.
► Systems which treat ballast water
during intake only, can utilize
gravity discharge with provision
for neutralization.
►
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Installation Pointers
► Installation surveys to ensure that the BWTS is installed in accordance with the approved drawings and BV requirements. On-going surveys ensure correct maintenance and operation and record-keeping on board.
► Makers must provide information on whether system can generate hydrogen or other hazardous gases affecting ballast water tank coatings.
► Plastic pipes are to meet the fire endurance requirements of the BV Rules and Regulations and IMO Resolution A.753(18).
► Transfer of ballast water from non-hazardous to hazardous area may be accepted but not vice versa.
► Ballast from the APT is to be discharged to a hazardous area, piping is to be provided with two non-return valves in series and be at main deck level.
► Penetrations of engine/pump room bulkheads are in general not permitted.
► Spool pieces are removed after ballast transfer and the open pipe flanges be covered by blanking plates adequate for the service pressure.
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Problems with filters
► Clogging
► Mechanical failure
► Corrosion
► Water hammer
► Damage due to foreign particles
► Lack of spares-moving parts
► Filters are very heavy !!
► Need robust supports
► Difficult to move
► About 10 m head loss (v2)
► Fresh water washing
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Filter impact on BWTS
► We believe that filters are the most challenging part of BWTS and also “sine qua non”. Filters remove/withhold the largest percentage of zoo- and phyto- planktons. 97% and 50% respectively.
► Many of the existing filters have inadequate self-cleaning abilities, resulting in serious clogging problems. If the filter clogs, the ship stops!
► Filter protection – multilayer screens of varying mesh sizes – pre-filtering. Multiscreen solutions.
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Filter dimensions - weight
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Installation in Oil & Chemical Tankers
► If possible install in a hazardous area (pump room). Such systems must be explosion proof
► Moving parts that can cause static electricity are not installed in hazardous areas.
► Ballast tanks are hazardous areas.
► Systems might be installed in the engine room. Treated water can go to the ballast tanks through the main deck.
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How to penetrate BHD separating safe/unsafe
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Challenge: Sampling
► Maximize the representativeness of
the water sample (especially for
larger mobile zooplankton).
► Candidate locations in the
discharge of the ballast pump
(where turbulence is very high).
► Isokinetic sample from a pipe
located at the center of the main
ballast pipe is preferable than from
a small pipe attached to the wall of
the pipe.
► Inside diameter of the sampling
pipe should be approximately 10%
of the diameter of the ballast pipe or
1.5-2 times the computed isokinetic
diameter.
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Sampling purpose and sampling points
► For BWT standards, samples serve to confirm compliance (qualitative analysis)
► Preferred sampling point for BWT is at discharge of ballast water
► Sampling for BWE standards is usually from the ballast water tanks, taken trough man-ways, air or sounding pipes
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Sampling
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EPA VGP
► A) BW system functionality monitoring
– BW monitoring equipment calibration (sensors – annually)
– Critical sensors more frequent (pH probes, TRO sensors, turbidity sensors, etc.)
B) Effluent biological organism monitoring
– Biological indicators – bacteria only (heterotrophic bacteria, E.coli, Enterococci)
– 2 times per year (1 time second year), records to be kept 3 years
► C) Effluent limitations for BWTS using Active Substances
– Discharge of biocides or residuals may not exceed instantaneous max limits (e.g. Chlorine 100 mg/l)
– Sampling 3 times in 180 days, then 2 times per year
Calibration Schedule • Electrolyzer Level Switch (1)
• Drain Tank Level Switch (1)
• Pressure Indication & Transmitter for Gas Separator (1)
• Gas Detector (3)
• Seawater Salinity Sensor (2)
• Main Flow Transmitter (3)
• Level Indication & Transmitter for N.A Tank (1)
• TRO Sensor (3)
• Turbidity, color, or suspended solids can introduce positive interference
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Ballast water monitoring-Biomarkers
► Indicative analysis: means a compliance test that is a relatively quick indirect or direct measurement of a representative sample of the ballast water volume of interest.
► Detailed analysis: means a compliance test that is likely to be more complex than indicative analysis and is a direct measurement of a representative sample used to determine the viable organism concentration of a ballast water volume of interest.
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PSC inspection
► Sampling inspection by PSC
► Position of sampling point(s)
► Alarm on any bypass line
► Ballast Water Management Plan approved by Administration
► Spare parts (e.g. chemical, UV lamp)
► Crew’s familiarization for BWMS operation
► IBWM Certificate
► Ballast Water Record Book
► D-1 Sampling / Salinity
► D-2 Analyses / Indicative
► D-2 Analyses / Detailed