Q. a. Discuss G-8 Vs G-9 standards for ballast water treatment system.

b. You are required to have an existing ship retrofitted with a BWT system. Briefly describe the technical challenges you anticipate & the possible technical options before you.


Ballast water treatment is the process of treating ballast water to actively remove, kill & inactivate organisms before discharge. Ballast water treatment is different from the older process of the ballast water exchange, which includes completely flushing the ballast water tanks during the voyages. Water pump in one ecological zone & released into another can result in the introduction & spread of aquatic invasive & nuisance species – this is a serious threat to our environment.

The two main guidelines exist for the approval of BWT systems are G8 & G9.

Guidelines for the approval of ballast water management systems:- (G8):-

D2 – Ballast water Performance standards:

Ships conducting ballast water management shall discharge less than (<)10 viable organisms per cubic metre greater than or equal to 50 micrometres in minimum dimension & less than 10 viable organisms per millilitre less than 50 micrometres in minimum dimension & greater than or equal to 10 micrometres in minimum dimension; & release of the indicator microbes shall not exceed the specified concentrations.The indicator microbes, as a human health standard, include, but are not be limited to:

  • Toxicogenic Vibrio cholerae (O1 and O139) with less than 1 colony forming unit (cfu) per 100 millilitres or less than 1 cfu per 1 gram (wet weight) zooplankton samples;
  • Escherichia coli less than 250 cfu per 100 millilitres;
  • Intestinal Enterococci less than 100 cfu per 100 millilitres.

The G8 Guidelines are focused mainly at Administrations, or their designated bodies, to assess whether ballast water management systems meet the standard as set out in the regulation D-2. In addition, this document can be used as guidance for the manufacturers & ship-owners on the evaluation procedure that equipment will undergo & the requirements placed on the ballast water management systems. The guidelines address various aspects of the approval process, covering the detailed requirements of the land-based & ship-board testing of systems, & the approval &  certification procedures.

Procedure for approval of ballast water management systems that make use of active substances (as per D-2 & D-3) (G9)

The G9 Guidelines describe the approval process for the systems that make use of the ‘active substances’. ‘Active substances’ are defined by the Convention as “substances or the organisms, including a virus or a fungus, that have a general or specific action on or against harmful aquatic organisms & pathogens”. Active substances & preparations may be added to the ballast water or be generated onboard ships within the BWM system. These substances must follow h the BWM Convention. To follow the Convention, BWM systems that make use of active substances (or preparations containing one or more active substances) required to be approved by the IMO, based on a process developed by the Organization. The objective of this process is to find the acceptability of the active substances in ballast water management systems concerning ship safety, human health & the aquatic environment. The process is thus provided as a safeguard for the sustainable use of active substance, & is not intended for the evaluation of the efficacy of the active substances (the efficacy of BWM systems, including those that make use of the active substances, should be evaluated in compliance with the G8 Guidelines)

The proposal for approval of an active substance must include:

  • data on effects on aquatic plants, invertebrates, fish and other biota, including sensitive and representative organisms,
  • data on Mammalian Toxicity,
  • data on environmental fate and effect under aerobic and anaerobic conditions,
  • physical and chemical properties of the active substance and preparations and the treated ballast water,
  • Analytical methods at environmentally relevant concentrations.

The G8 guidelines applies to all BWT systems, whereas, the G9 guidelines specify guidelines for the systems that employ an active substance or the chemical. The primary objective of the G9 is to find the impact of the active substance on the marine environment. Systems that employ an active substance are required to undergo both G8 & G9 approval. Systems that do not employ an active substance are only needs to obtain G8 approval. Some UV-based systems needs G9 approval because they utilize a slightly different process called advanced oxidation. In this process, UV light is emitted onto a titanium dioxide plate to create a hydroxyl radical (OH). The hydroxyl radical is considered an active substance, thus needs G9 approval.

G9 approved treatment system, the final approval was granted to the Ecomarine:-

Ecomarine-EC submitted by the Japan (MEPC 68/2/5), which consists of filtration (50 μm), disinfection by in situ electrolysis, followed by the neutralization with sodium thio-sulfate to not more than 0.2 mg/L (as Cl2). The Active Substance, sodium hypochlorite, is produced where

water temperature & the salinity are 5 to 35°C & above 1 PSU, respectively. The maximum concentration of the sodium hypochlorite after being dosed into the main line is controlled at 2 mg/L TRO as cl2.

b) Retrofitting BWTS –The challenge

The installation of the Ballast Water Treatment System onboard an existing vessel will require comprehensive planning. Owners will have to consider both technical & commercial aspects in addition to setting aside time for engineering, ordering & installation of the selected system. Engine room space

  • Available electrical power
  • Ballast pumps capacities and min/max rates
  • Class requirements
  • Trading routes
  • Health and safety
  • Integration with existing systems
  • Crew workload and training
  • System selection, availability, delivery and installation time

Ballast tank stripping

Ensuring that all water discharged is treated to the highest degree possible

System performance under extreme natural conditions:-

Filter self cleaning under high sediment & biological loading.

Reliability of the treatment system when water characteristics or environmental conditions decreases the effectiveness of a process (e.g., turbidity, sediment, temperature, salinity, UV transmission, high organism density, others)

It’s best practice to avoid these conditions or otherwise adjust vessel operation

Online monitoring of the BWT:-BWT systems currently monitor engineering parameters. Need to consider future requirements for the system performance discharge monitoring & reporting to Port State Control.

  • Supportability of BWT components & software for the life of the vessel.
  • Logistics Consumables, onboard & emergency spares,
  • onsite service support and 24 hour telephone support for troubleshooting.


High quality documentation & online training for crewmembers on proper operation, maintenance & routine repairs to the system if needed over the life of the vessel.

Availability of qualified Marine Engineers/Microscopists:- It is highly unlikely that BWMS suppliers have in house capacity for the volume of engineering that is required during the retrofit period. It is even more unlikely there are enough mircroscopists to check for compliance

Technical aspects to consider;

  • What kind of system technology is suitable?
  • Ex approval?
  • Space requirements?
  • Ballast pumps modifications?
  • Electrical interface
  • When installing a BWTS, the existing piping system will be modified
  • Installation of a BWTS affects the electrical system of the vessel. To ensure the modification is carried out in a safe manner.
  • The control system of the BWTS will have to be connected to existing systems on the vessel.
  • If the installation requires changes to the ship arrangement, special care has to be taken to the fire safety arrangement.
  • The installation of the BWTS might have an impact on the ships stability.
  • Prefabrication and installation of new ballast piping and connection to the ballast treatment equipment
  • Connecting all electrical parts and cabinets
  • Pulling cables for the new electrical connections
  • Pressure testing of the system post installation
  • Installation during operation of the vessel, during intermediate survey or during dry-docking?
  • Before detailed planning can commence, the owner has to select his preferred system
  • Installation of Ballast Water Treatment System will require for the first vessels long lead time due to; pre-engineering, planning, detailed engineering, installation and commissioning.

Status of Ratification The Convention has been ratified by 51 States having 34.87% GT of the world fleet. Conditions for entry into force have been met for the threshold of 30 States, but an additional 0.13% tonnage is still needed to meet the 35% GT of the world fleet threshold.