6.2 BALLAST WATER TREATMENT TECHNOLOGIES REVIEWED

Technologies that have been assessed or are currently being investigated for application in the treatment of ballast water can be divided into three main categories: chemical, mechanical, and physical. The use of on-shore facilities such as oily ballast treatment facilities can be considered separately.

6.2.1 Chemical technologies

6.2.1.1 Peroxide

Hydrogen peroxide may be used as a biocide to destroy marine organisms. Ballast tanks are dosed with a concentration of peroxide sufficient to destroy cell integrity by attacking fatty acids within the membrane causing tissue damage³⁰⁷ The efficiency of peroxide as a biocide on algae and other related aquatic plant life has been successfully demonstrated³⁰⁸
The advantage of using a chemical treatment such as hydrogen peroxide is that it readily decomposes to hydrogen and water, thereby reducing the risk of pollution to the environment³⁰⁹

Doses required to achieve necessary organism mortality are, however, prohibitively expensive for large applications as would be the case for ballast water³¹⁰ In addition, the Committee notes that, due to the chemical's oxidising properties, the use of hydrogen peroxide for on-board treatment would require purpose built tanks and piping, which is also likely to prove prohibitively costly.

6.2.1.2 Hyper salination/Salinity adjustment

Hyper salination involves the addition of large quantities of sodium chloride (salt) to ballast water to create a super-saline environment. The sudden increase to extreme levels of salinity destroys cells through dehydration.

Although salt would be environmentally innocuous, possible corrosion of ballast tanks may occur due to the large quantities of salt needed. This means that hypersalination is unlikely to be a viable solution in the treatment of ballast water, particularly in the case of older vessels where tank coatings may not be intact³¹¹

Alternatively, the addition of freshwater to salt water dramatically reduces water salinity causing tissue destruction in some organisms through osmotic swelling. The Committee believes that this method is unlikely to be practical or economically viable due to the large quantities of freshwater required, and associated pumping and piping needs. In addition, the estuarine organisms commonly found in ballast tanks are tolerant to wide fluctuations in salinity thereby reducing the effectiveness of this treatment.

6.2.1.3 Chlorination

As a biocide, chlorine acts in a similar way to hydrogen peroxide, destroying cell membranes and resulting in irreversible tissue damage. Chlorine may be produced by dosing ballast tanks with soluble chlorine, chlorine gas or by passing an electrical current through the water, thereby producing chlorine through the reaction of chloride ions³¹²

Although commonly used in industry and domestic applications to reduce and inhibit microbial growth, the Committee finds that the large quantities of chlorine needed to treat resistant dinoflagellate cysts preclude its use in the treatment of ballast water. The quantities needed would be further increased where ballast tanks contain bottom sediment, because sediment readily absorbs chlorine³¹³ Finally, residual compounds resulting from the addition of chlorine to ballast water may constrain time and place of ballast water discharge due to the potential environmental effects within a localised environment such as a harbour³¹⁴

6.2.1.4 Chlorine dioxide

The application of chlorine dioxide is achieved by combining a fixed ratio of chlorine and sodium chlorite to disinfect water in the same way as chlorine. While its success as a biocide is greater than that of chlorine and lesser quantities are required, the cost factor is significantly higher than that of chlorine³¹⁵ The Committee notes that chlorine dioxide also produce residues which may prove harmful to the environment.

6.2.1.5 Sodium/Calcium hypochlorite

These compounds act to affect organisms in the same way as chlorine by damaging tissue and causing death.

Both sodium and calcium hypochlorite would be needed in large quantities to achieve ballast water disinfection. The Committee finds that economic factors are therefore likely to preclude the application of these compounds in the treatment of ships' ballast water. Additionally, as in the case of chlorine, residual compounds resulting from the application of these chemicals would be environmentally unacceptable and further treatment of ballast water would be required before discharge³¹⁶

6.2.1.6 Ozone

Ozone is a more effective biocide than chlorine and is being used increasingly in the place of chlorine in the treatment of domestic and industrial water supplies³¹⁷ Salt water ozone reactors are currently used for salt water aquaria and fish hatcheries.

Because ozone decomposes rapidly back to oxygen, it is unlikely to be environmentally damaging. Ozone gas, however, is toxic, and operational and maintenance costs of its use are likely to be high³¹⁸ The Committee considers that high capital costs of specialised equipment to produce ozone in large quantities and to retrofit vessels, may also preclude its use.

In addition, for ozone treatment to be effective, ballast water may require pre-treatment to remove sediment - a factor that would add to the overall cost³¹⁹

6.2.1.7 Other biocides

Apart from chemicals with biocidal properties such as those discussed above, there are several specific biocides available for use in the eradication of aquatic pest species. These agents act either to kill organisms outright or to inhibit growth and reproduction.

Concerns raised in using biocides as a means for disinfecting ballast water are similar to those of the chemicals discussed above:

· ballast water may require further treatment to remove residual compounds before discharge into the environment;

· concerns over the health and safety aspects of handling highly toxic chemicals; and

· the high cost of biocides³²⁰

The Committee concludes, therefore, that the use of specific biocides for ballast tank disinfection is unlikely to provide a solution to the ballast water problem.

6.2.1.8 Anti-fouling compounds

Anti-fouling compounds are composed of polymer or chemical binding agents containing toxic compounds which kill biota settling on treated surfaces. These coatings are usually applied to ships' hulls to prevent fouling (Chapter 3.6).

The Committee considers that the application of modern anti-fouling coatings to the inside of ballast tanks is unlikely to be feasible for ballast water treatment for the following reasons:

· water motion inside a ballast tank would be insufficient to activate the anti-fouling compound;

· the organisms susceptible to such a treatment would be limited to those benthic species which adhere to a surface as part of their life-cycle; and

· where chemicals such as Tri(n-butyl)tin (TBT) are used in anti-fouling coatings, residues discharged with the ballast water may not be environmentally acceptable.

6.2.1.9 pH adjustment

Many organisms are susceptible to sudden changes in pH, and the addition of an acidic or alkaline compound to increase or decrease the pH of ballast water has been considered as a method of disinfecting ballast water³²¹

Corrosion resulting from lowered pH would present problems in the maintenance and operation of ballast water treatment systems on-board commercial vessels. Treating ballast water with large doses of lime to achieve increases in pH may also result in corrosion³²²

In addition, it has been shown that some species of dinoflagellates are unaffected by changes in pH which would limit the range of species affected by the treatment³²³ The Committee therefore considers that this form of treatment is unlikely to be successful.

6.2.1.10 Summary

Although successful in the treatment of domestic and industrial water supplies, the chemical technologies discussed above are less likely to be viable for the treatment of ballast water. This is largely due to the expense of the chemicals themselves and the associated operating and material costs. The potential negative effects on the environment of residuals remaining after treatment also mean that such chemical treatments are unlikely to be viable. Further treatment of the water can be undertaken to neutralise these residual compounds, but this would add considerably to the costs of an already expensive treatment.

6.2.2 Mechanical technologies

6.2.2.1 Filtration

Filters are used extensively for waste water and in municipal and industrial water supplies. Filtration is achieved by fitting self-cleaning strainers composed of natural or synthetic fibre or beds of granular material known as a deep media filters³²⁴into pumping lines.

Filtration can also be achieved by reverse osmosis and ultra-filtration using semi-permeable membranes to separate small particles from the water³²⁵ The Committee observes that is method is unlikely to be suitable due to operational difficulties caused by flow rates, size of particles within ballast water causing clogging, and the increased expense compared with other forms of filtration.

Generally, filtration has not proved successful as an on-board treatment option due to:

· operational difficulties caused by flow rates;
· particles in the ballast water causing clogging;
· large size of the units required;
· problems associated with disposing of large quantities of residual material; and
· logistical factors concerned with the operation of the facility on-board.

Recent developments in the use of micro-filtration in which hollow fibre membranes remove viruses and bacteria have meant that the viability of micro-filtration for ballast water is now being re-considered³²⁶ The Committee notes that micro-filtration has been used for contaminated water supplies and may, in the future, prove viable for use as a shore-based or emergency mobile treatment facility³²⁷

In the United States, filtration systems fitted within the ballast pumps of a vessel are currently under investigation aboard the m.v. Algonorth trading in the Great Lakes. Although trial results are unavailable at present, it is expected that filtration will need to be used in conjunction with other measures such as ultraviolet or heat treatment³²⁸

6.2.2.2 Cyclonic separation

This method of water treatment uses the circular motion of a centrifugal pump to remove solids to a collection chamber, resulting in an outflow of decontaminated water. Although this method is simple and effective, the Committee observes that it is unlikely to remove very small marine organisms due to their specific gravity being close to that of the surrounding water³²⁹

6.2.2.3 Continuous deflective separation

The continuous deflective separation unit is a liquid/solid separation technology recently developed in Australia³³⁰ The unit operates to separate water and pollutants via the vortex created when water is pumped into a separation chamber containing a filter. The vortex action in the chamber also assists in preventing the filter from becoming blocked. Solids are then collected in a catchment chamber.

The unit is of a size suitable for use on-board an existing vessel. It can easily handle flow rates associated with pumping ballast water, however the effective filtration size at these flow rates are approximately 50-100 microns. Additional technology would therefore need to be used in conjunction with the unit to deal with very small organisms. Further research is being undertaken to increase the filtration capability of the unit, allowing the separation of particles smaller than 50 microns³³¹ The Committee notes that this technology may, in the future, prove valuable in the treatment of ballast water.

6.2.2.4 Sedimentation/Flotation

Sedimentation is achieved by the used of a coagulant which acts to cohere heavier particles which then settle and can be removed by localised pumping.

Flotation relies on encouraging particles to form by use of a chemical coagulant. Due to the nature of the coagulant, particles then rise to the surface after attaching to air bubbles which are injected into the water column. Floated residue is then scraped from the top of the tank.

In the application of ballast water treatment, sedimentation and flotation are unsuitable for on-board use as these processes rely on a steady free surface. These treatments could be considered for onshore treatment as they both result in approximately 1% residue. The Committee observes that the cost is considerably less than for other treatments³³²

6.2.2.5 High pressure pumping

Destruction of organisms can often be achieved by the use of high velocity and impact pumps.

While high pressure pumping may destroy larger marine animals, the Committee notes that smaller organisms with insufficient body mass (particularly cysts) are not affected³³³

6.2.2.6 Dedicated or on-shore ballast water treatment facilities

A number of the technologies discussed so far may be suitable for inclusion within an on-shore ballast water treatment facility. Vessels could discharge their ballast to shore while loading cargo, or part load to their maximum allowable draft and move to a designated berth to de-ballast before returning to complete loading. An investigation of the cost of constructing such facilities was undertaken by AQIS in 1993³³⁴ The study found that a system using chemicals, ultraviolet treatment and filtration would cost between $9-19 million. This cost did not include acquisition of the land or costs of constructing a pipeline around the perimeter of the port to transfer ballast from each berth.

Capital costs and operational costs would be port specific. The Committee considers that the large scale construction of such facilities in Victoria is likely to be cost prohibitive, however, smaller installations may provide viable options for discharge to shore of ballast from vessels suspected of carrying organism-contaminated ballast. This treatment option is discussed further in Chapter 9.

6.2.2.7 Treatment ship

The concept of a treatment ship was suggested in an investigation into treatment options undertaken by AQIS in 1993³³⁵ The study found that a treatment ship which used filtration, ultraviolet rays and chemicals to treat the ballast water would cost approximately $21 million with an annual operating cost of approx. 3 mil (at 70% utilisation).

While a treatment ship would provide a solution to the problem of transferring ballast from the site of discharge to the site of treatment, the Committee notes that capital and operating costs are far greater than the other treatments costed so far. In addition, for most river ports in Australia where shipping berths lie parallel to the main channel, a treatment vessel moored alongside a vessel for the duration of de-ballasting may cause congestion of shipping traffic within the port. Second, ports with multiple cargo facilities may have several vessels discharging ballast at the same time. This would require more than one treatment ship or facilities at each berth in which to store ballast awaiting treatment. For practical and economic reasons, the Committee concludes that this treatment option is unlikely to be suitable for treating ballast water in Victorian ports.

6.2.2.8 Ballast exchange

One method of removing marine organisms entrained within ships' ballast water during the up-take of ballast water in ports, is the mid-ocean exchange of ballast water while the vessel travels en route to its next port of destination. During ballast water exchange, any organisms entrained in tanks are flushed out and the tanks are then re-filled with deep ocean oceanic water which is relatively free of planktonic organisms. The influx of oceanic water with different characteristics to that of estuarine water (most notably salinity) may create an environment which is hostile to those coastal organisms that remain in the tank after the exchange³³⁶ In addition, any organisms collected from deep ocean water during ballast exchange are unlikely to survive in coastal water environments.

Trials carried out in Australia on the m.v. Whyalla showed that the exchange of ballast water within ship's ballast tanks could be achieved by either of two methods (Figure 3):

· emptying ballast tanks sequentially and then refilling them with clean oceanic water (re-ballasting); or

· removing ballast tank inspection hatches on the deck and running ballast pumps for a period equivalent to allowing three times the volume of the tank to flow through the hatch and out over the ship's side (flow-through ocean exchange)³³⁷

The flow-through ocean exchange method of replacing ballast water was developed for vessels unable to completely empty and refill ballast tanks due to ship design or to the stresses imposed on the vessel.

FIGURE 3
Ballast water exchange methods

Source: Rigby, G. (1994), Possible solutions to the ballast water problem, AQIS Ballast Water Symposium Proceedings 11-13 May 1994, Canberra. AGPS, Canberra.

The study on-board the m.v. Whyalla showed that re-ballasting removed 99% of the original ballast water taken on-board at the discharge port. Flow-through exchange of ballast removed 95% of the original ballast³³⁸ For this reason, ballast exchange using either method has become an accepted practice via international voluntary guidelines for vessels travelling between ports.

The Committee recognises that there remain some aspects of ballast exchange which lessen its desirability as a long term solution. These include:

· a small number of vessels with double bottom ballast tanks may be unable to exchange ballast by removing inspection hatches if these hatches are located at the bottom of the hold;

· occasionally, vessels trading short distances in inclement weather may have insufficient time in which to carry out a full ballast exchange (i.e., three times the volume of the tank). The Committee discusses this further in Chapter 9;

· ballast exchange is not completely effective, as sediments and unpumpable ballast are not removed.

Although ballast exchange has offered the safest, most biologically and cost effective solution so far, the Committee notes that it is not an ideal measure. In the absence of a better solution, however, research into more effective ballast water exchange should be encouraged.

6.2.2.9 Summary

Mechanical treatment of water offers several possible solutions to the problem of ballast water disinfection. Improved technology in the application of filtration for the treatment of various water pollution situations has resulted in systems such as micro-filtration and continuous deflective separation which offer viable options which could be considered seriously in the application of ballast water treatment.

Other mechanical water treatments such as cyclonic separation, sedimentation/flotation, and high pressure pumping are limited in the range of organisms they will eliminate.

Large scale dedicated ballast water treatment facilities either on-shore or on-board a dedicated treatment ship are likely to be prohibitively expensive. Smaller installations may, however, provide viable options for discharge to shore of ballast from vessels suspected of carrying organism-contaminated ballast.

Ballast exchange is the method currently recommended for use by industry to minimise the risk of organism translocation. The Committee believes that it should not, however, be viewed as a long term solution to the ballast water problem.

6.2.3 Physical treatments

6.2.3.1 Electrolytically generated copper and silver ions

This system operates by using an electrical current to disperse concentrations of copper and silver ions into the water column. At certain levels, these metals are toxic to many marine organisms. While they may not be lethal, they can inhibit reproduction and prevent colonisation.

Research into this type of water treatment has found it to be ineffective against bacteria and phytoplankton³³⁹ Since many organisms are transported in the larval phase of their life cycle, the Committee considers that this method of water treatment would be unsuitable for ballast water applications.

6.2.3.2 Ultraviolet radiation

Ultraviolet (U.V.) radiation occurs following the application of ultraviolet light in varying wavelengths causing a photochemical reaction of the biological constituents within animal or plant tissue³⁴⁰ This method of water treatment is commonly used to sterilise domestic water supplies and is effective against a wide range of organisms, notably viruses and bacteria.
One of the advantages of a U.V. system is the absence of toxic residues produced by the process. Disadvantages of U.V. are:

· water must be clear for effective penetration of the light waves;

· studies have shown that U.V. radiation is not successful against many species of algae and organisms which may present as spores or cysts³⁴¹ and

· due to the high content of sediment associated with ballast water, a pre-treatment such as filtration would be necessary to ensure the maximum effectiveness of U.V. treatment.

The Committee notes that although U.V. treatment is limited as a sole option, the combination of U.V. treatment with microfiltration may offer a potential solution for the treatment of ballast water³⁴²

6.2.3.3 De-oxygenation

De-oxygenation is achieved by reducing dissolved oxygen content within the ballast water resulting in the mortality of organisms present. Air vents to the tank are sealed and an oxygen scavenging agent such as sodium metabisulphate is added, removing the oxygen from the water³⁴³

The disadvantage in applying this method in the case of ballast water is the ability of many marine animals to survive in anoxic conditions, particularly bacteria and other microbes in cyst or spore stages. De-oxygenation will rapidly produce residual hydrogen sulphide in the absence of oxygen. In addition to corroding ballast tanks, sulphur released into aquatic systems is unlikely to be environmentally acceptable.

The Committee therefore believes that this method of water disinfection treatment will not provide a solution to the ballast water problem.

6.2.3.4 Heat treatment

Waste heat from the main engine of ships is used to heat ballast water up to 35-45⁰C. It is suggested that temperatures within this range are sufficient to destroy organisms such as dinoflagellate cysts³⁴⁴and zebra mussels³⁴⁵

The advantages of this system are that existing ship systems can be utilised and there is an absence of toxic residuals. Heat treatment may, however, have a limited application as many microbes such as cholera bacteria produce spores which will survive temperatures exceeding pasteurisation (approx. 60⁰C). The International Maritime Organisation (IMO) believes heat treatment is potentially viable for small ships, however, the high energy costs associated with heating large quantities of water may preclude its use by larger vessels³⁴⁶ In addition, vessels on short voyages may not have sufficient time to heat large quantities of ballast to the required temperatures³⁴⁷

The Committee notes, that despite the disadvantages of heat treatment discussed above, this option is currently under investigation as an on-board treatment option, and is widely considered to have potential as a successful method of treating ballast water.

6.2.3.5 Electric pulse and pulse plasma techniques

An electric pulse system operates by passing an electric pulse between two electrodes within the water column. These electric pulses are lethal to several marine species such as shrimp and some bacteria.

Pulse plasma technology operates to produce chemical reactions in water by the application of short high energy pulses forming an arc across an electrode gap. U.V. radiation produced by energised plasma resulting from the chemical reaction causes the destruction of biota present. Additional mortality results from intense cavitation caused by the shock waves produced within close range of the arc³⁴⁸

It is estimated that the installation cost of such equipment on-board a commercial vessel is likely to be high. In addition, the power requirements needed to operate this system in the application of ballast water treatment would be significant owing to the large quantities of water involved³⁴⁹ For these reasons, the Committee finds that neither of these options is likely to be successful in the treatment of ballast water.

6.2.3.6 Acoustic systems

Ultrasonic technology uses low frequency sound waves to produce a cavitation effect within the water column. This causes a mechanical stress on the body structure of the animal usually resulting in death. The range of organisms affected by this technique is variable.

Although acoustic technology has been shown to cause mortality in juvenile zebra mussels and several major groups of micro-organisms³⁵⁰ the Committee concludes that the overall effectiveness of this type of treatment, particularly on more complex and larger animals, does not warrant its further investigation as a means of treating ballast water.

6.2.3.7 Magnetic fields

The creation of a magnetic field within water has been shown to be effective against zebra mussels and other calcareous shell-producing organisms. The Committee observes that this method is yet to be trialed in salt water and at this stage does not represent a viable option for the treatment of ballast water for the scale of operation required³⁵¹

6.2.3.8 Summary

Physical treatment of water alters the physical properties of water to render it hostile to biological inhabitants. The main problem associated with such treatments is one of scale - the majority of physical treatments discussed above cannot deal with the large quantities of water associated with ships' ballast. Further, many of these treatments are still at the experimental stage or are very expensive owing to their recent technological development.

Of the treatment methods discussed above, the Committee concludes that heat treatment and U.V. radiation are the two mechanical treatments which are, in the future, most likely to be considered viable on-board treatment options for ballast water.

6.2.4 Existing onshore water treatment facilities

6.2.4.1 Sewage treatment facilities

It has been suggested that ballast water could be discharged ashore to sewage plants for treatment³⁵² For most sewage treatment facilities this would not be a practical option, as the trend towards re-use of treated water for irrigation etc., would preclude the inclusion of salt water in a re-cycling system. The salinity content of ballast water may also affect the biological processes that form part of the treatment process³⁵³

In addition, the discharge of ballast water from ships' ballast tanks to a sewage treatment facility would require that either the sewage plant be located within the port precinct, or that many kilometres of pipeline be installed to allow delivery of the ballast water. The Committee considers that option is therefore unlikely to be economically viable.

6.2.4.2 Oily ballast water reception facilities

To ensure that petroleum tankers comply with the MARPOL Convention, oil refineries exporting petroleum products provide reception facilities for those ships without dedicated ballast tanks. These ships carry both oil and ballast water in the same tanks. When empty of oil cargo, ballast is carried in the cargo tanks. Consequently, before cargo is loaded, vessels must empty cargo tanks of ballast water, and the oily ballast is pumped ashore for treatment at the refinery.

Such ballast water reception facilities are provided only for vessels loading at refineries (tankers), and the capacity of reception facilities for receiving oil contaminated ballast is calculated accordingly. This facility would not, therefore, be available to all vessels using Victorian ports. The Committee believes, however, that in isolated cases where vessels suspected of carrying small quantities of contaminated ballast need to discharge ballast to shore, it may be possible to for tankers and other vessels fitted with discharge manifolds to discharge ballast to on-shore oily ballast water facilities.

6.2.4.3 Evaporation ponds

This option has been considered for areas where climatic conditions are favourable for evaporation and where abundant land is available. It has been suggested that such an approach may be viable in the north west of Australia in locations such as Dampier, where salt production is undertaken by the use of evaporation ponds³⁵⁴

The Committee notes that salt produced from the evaporation of ship's ballast water is not likely to be suitable for use due to the presence of sediment and other impurities. In Dampier, much of the land available within the vicinity of the port area for the construction of evaporation ponds, is also presently used by the existing salt producer, Dampier Salt. That company also has concerns that cross contamination of the current salt producing ponds by ballast water treatment ponds could result in significant financial loss for the existing company³⁵⁵

For most ports in Australia, coastal land is commonly being converted to residential use due to its increasing value. The amount of land required for the construction of evaporation ponds of sufficient capacity would be prohibitively expensive for many south-eastern Australian ports which are located within or close to metropolitan areas. Additionally, implementing this method of ballast water treatment would require construction of kilometres of pipeline to allow delivery of the ballast to the treatment area.

In addition, the Committee questions if the use of land in this way would be acceptable on environmental grounds. For example, the discharge of large quantities of sea water to evaporation ponds may increase local soil salinity.

6.2.4.4 Summary

With the exception of the possible discharge of small quantities of organism contaminated ballast to on-shore oily ballast facilities, the Committee finds that the application of existing onshore treatment facilities in the treatment of ballast water is not viable. This is due to the considerable expense and operational disruption that would be caused by the incorporation of contaminated ballast water into these systems.