BWMS – Selection Criteria

Type  Approval

To  install a  Ballast Water  Treatment System  on  board  ship,  it  must  be  ‘type  approved’ by  the flag  administration  or  a Recognised Organisation in  accordance  with the  relevant IMO  Guidelines. If the system uses an  active  substance,  this  will  need  to  have  received   a final  approval from  the  IMO before  type  approval  can  be  granted.


All Ballast  Water  Treatment  Systems  have  a  ‘total capacity rate’  (TCR).  This  indicates  how many  cubic  meters  of  ballast water the system  can process  each  hour.  A  system  with  a  ‘total capacity rate’  (TCR)  high enough  to  handle  ship’s  ballast  capacity  &  operational pumping  rate is  to  be  selected.

Space Requirements

System  footprints  range  from  approximately  0.25  m2  to  145  m2, depending  on  their  TCR. Some  are  single  units while  others  can  be  installed  as  the separate  components. Ballast  Water  treatment systems having  separate  components  may  be  useful  if  a single  space  on  board  ship  is  not  big  enough or  if the access  for bringing  a single system  on board is  difficult.

Capital and  operating costs

Ballast Water Treatment System  installation  is  a big  investment  &  could cost as much as $2,000,000  depending  on  the  manufacturer. As  for operating costs,  it  depends  on the  type  of system and  starts from  as  little  as  a  few  dollars  per  1,000  m3  of treated  water.  Many  system  suppliers  quote the operating  costs  below  $20 per  1,000 m3.

Power  Requirements

  • Some  systems  have  very  high  power  requirements  – as much  as  220  kW  per  1,000 m3  of treated water.  Hence  it  is  to  be  checked  whether there will be  a  need  to  run  another  generator  when the  system is in operation  or  even  install  an  additional generator  set.
  • Another  consideration is  whether  a spare  breaker  is  available  in  the  electrical distribution board  to  provide power  to  the  Ballast  Water  Treatment System.  If  not, an  alternative solution  has  to  be arranged.

Integration with  existing  Ballast  Water  System

It  is  advantageous  to  integrate  the  alarms  and controls  for  the  treatment  system  with  those  for the ballast  pumping  system,  so  that  both  can  be  operated  from  all  control panels.

Type of  Process  Technology  employed

Overview  of  Treatment Technologies

IMO  defines  ballast  water treatment  equipment  as: “…the  equipment which mechanically, physically,  chemically  or  biologically  processes  either singularly  or  in  combination to  remove, render  harmless or  avoid  the  uptake  or  discharge  of  harmful  organisms or  pathogens. Ballast water treatment equipment may  operate  at  the  uptake  or  discharge  of  the ballast water, during the  voyage, or at a  combination  of  these  events.”

Technical Challenges  &  System Combinations

  • The  treatment  technologies  differ  in  method  and  rate  of  application,  scalability,  holding  time (required for kill  rates  and safe  discharge),  power  requirements,  effects  on  other ship  systems or  structure  (corrosion),  inherent  safety and  costs  of  operation.  In  many cases  their  efficacy varies  with  the conditions  of  ballast  water, flow  rates,  volume  of water  treated  &  holding time.  There  are also  issues  of  whether treatment  is done  at intake, while  being  held on  board, at  the discharge,  or  a  combination of the  three.  For  instance,  filtration,  separation &  UV radiation  are  done  during  ballast.  UV  radiation  is  also  used  during the de-ballasting.  These systems  are  sized  for the  maximum flow  rate  in  the  ballast  system.  Conversely  chemical biocides  and  de-oxygenation are  usually  applied  to  attain  a  certain  concentration in  the  water in  the  ballast  tanks. .
  • The  efficacies  of  these  systems  do  not  depend  so  much  on  the  flow  rate  of  the  pumps  as the time  the  ballast  is  allowed  to  remain  in  the  tanks  to  achieve  the  desired  kill rate. Short voyages  can be  a problem  for these  technologies. .
  • Matching  the  treatment  technology  to  the  ship  type,  or  more  accurately  the  ballast  system type,  and  vessel service  is  the key  to  designing  a successful ballast water  treatment  system. .
  • To  overcome  the limitations  of a particular technology  many proposed treatment  systems are based  on  a  combination of  two  or  more  technologies.  Although  there  are  approved chemical  disinfection only  treatments,  these  are  often combined  with  some form  of the pre- treatment to make  them more  effective for  certain vessel or  ballast  conditions.

Availability of consumables,  spares  and  service support

It  is important  to  be  able  to  keep  Ballast  Water Treatment  System  operational  at  all times.  If  it stops  working,  there  would  be  contravention  of  the  Convention and ship could  face  fines  or  detention. Availability  of  spares, consumables  and  servicing  support is to  be  ensured  in  all the  areas where ship is trading.

Effect  on  Ballast  Water  Tank  structure  &  Coatings

Corrosion and coating degeneration  are  two  potential effects that  system  substances  and processes  may have  on  tanks.  Hence assurance is  required  from  the  system  manufacturer  that tanks will not  be adversely  affected.

Time required for treatment  to be effective

This is an  important  consideration  depending  on  length of  voyage  and ballasting/ de- ballasting rate.  For  some Ballast  Water  Treatment plants,  24  hours  of  storing  of  ballast  water  in  the ballast  tanks  after  treatment  can  ensure  effective  disinfection  to  the Regulation  D-2  and  no  re-growth of organisms  were found in the treated  water  after  10 days.  Extent  of  reduction  in the vessel’s  ballasting rate  following  installation  of the treatment  system also  needs  to  be considered  i.e.  detail  of  the pressure  drop.

Health and Safety  aspects  for  Crew

A  number  of  different  chemicals  or  chemical processes  are employed  in  the  ballast water treatment  systems  available, which  are  as  follows:

  • chlorination
  • electrochlorination
  • ozonation
  • chlorine  dioxide
  • peracetic  acid
  • hydrogen  peroxide
  • menadine/vitamin  K
  • perchloric  acid.

Some systems generate  chemicals  during the  treatment process;  for  others,  chemicals  are required  to  be  stored  on  board.

If  chemicals are  stored  on  board,  the crew  will  require  training  on  their  use  and  handling. Suitable  storage  space  for the chemicals  & proper  ventilation  are  of  paramount importance.  The  Safety Data  Sheets  for  chemicals  to  be  stored  on  board  need  to  be  consulted  &  where  necessary the appropriate  fire  protection  &  extinction  arrangements  will  need  to  be  installed.

In  the case  of  systems  that  generate  chemicals  during  the  treatment process,  the  crew  will require  training  on  the hazards  associated  with  them.  Advice  on  the storage  and handling of chemicals  is  contained in  the  IMO Circular: BWM.2/Circ.20.

Ease  of maintenance, calibration and  water sampling

It  needs  to  be  ensured from  suppliers  that  maintenance  of Ballast  Water  Treatment  plant, calibration  of  monitoring and measurement  equipment and sampling  of  ballast  water is  easy.

Provision of  Emergency  bypass  operation

To  assure  the  ballast  water  management system (BWMS) remains  operational in  the  event of the treatment system failing,  suitable  by-passes  or  overrides  are  to  be  installed  to  protect  the  safety of  the  ship  and personnel.

The by-pass  is  to  activate an  alarm,  and  the  by-pass event should be recorded by  the  control  equipment.

Gas Safe

If  ship is  a  tanker  or  gas  carrier,  and  the  system is  going to  be  installed  in  a ‘gas  dangerous area’  (i.e.,  in  the  cargo area),  then  system must  be  certified ‘gas  safe’.