Ballast Water Management Technologies A Brief Review

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Leonard Lucas
6 years ago
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1 Ballast Water Management Technologies A Brief Review The following information is a brief overview of some of the potential ship board ballast water treatment methods which have been brought to the attention of the Coast Guard. The list of treatment processes represented here is not exhaustive; there are numerous efforts underway within the private sector for which little or no information is available in the public sector. This summary attempts to present a consensus of sometimes differing opinions on treatment methods found in available literature. The opinions stated regarding costs, safety, benefits, etc were gathered from various sources of unknown reliability and do not represent the views of the USCG. The treatment of ballast water on vessels is an extremely complicated process with many variables. To date, no treatment system has been installed on a single vessel, much less a range of vessel types, and demonstrated to be consistently effective in preventing AIS introductions under actual vessel operating regimes over a range of temporal and geographic conditions. Further, issues of cost are sure to depend on market forces that develop under the eventual domestic and international regulatory arenas. To date all cost estimates of which we are aware have been based on numerous, and sometimes poorly substantiated, assumptions.

2 The energy costs to run Safe for environment and the ballast pumps (plus crew. Ship stability could increased maintenance). be a concern, especially Empty/refill costs less in heavy weather - flow than flow through. through a bit safer Ballast water exchange both empty/refill and flow through practices Density gradient assisted (Navion concept) ballast exchange: System exploits density differences between tank and seawater to enhance efficiency of ballast exchange. Filtration: Pumping ballast water through a series of filters to strain out organisms Very expensive, $3-5 million for medium sized ship retrofit. Rough estimate for retrofitting a ship with a filtration system is $1M Safe for the environment, ship & crew. Tanks remain full at all times. Exchange occurs over a longer period of time and at a much slower rate eliminating many ship stability concerns. Safe for the environment, ship & crew. Still could introduce AIS. Efficiency of exchange largely dependent on tank configuration and previous ballast management practices. Many believe flow through is more effective than empty/refill Reportedly more efficient than normal ballast water exchange as little mixing occurs between differing densities of water making exchange more complete. Problem of remaining sediments may be worse because of decreased circulation of water in tanks. Filters have shown to remove up to 90% of particulate material onboard will remove the majority of plankton and any larger organisms. Not as effective removing smaller organisms (bacteria & viruses) (actual data is very limited, and studies have not been conducted over time or in challenging conditions). Currently considered an interim solution since ballast sediments are a likely vector for AIS. Efficiency could improve in the future if ship ballasting systems were specifically designed for optimum AIS prevention. Lab bench studies appear promising presently being evaluated onboard Navion Dania Most promising for vessels with lower ballast carriage rates (passenger vessels). Filters could possibly improve AIS reduction if combined with UV treatment.

3 High capital expenditure Safe for the environment, for hardware and ship ship & crew. installation. Hydrocyclone : Vortexes organisms & sediment from water UV Irradiation: passing ballast water through UV light to kill organisms Heat Treatment: use of very high temperatures (near boiling) for short durations (@ 60 seconds) within a heating chamber installed within the ballast water piping system or through counter-current heat exchangers in a flowthrough configuration. Considerable need many units to treat ballast, also UV units require maintenance to work properly High operational costs and installation costs. System not run off engine waste heat requires additional fuel supply. (Some concepts use waste heat from operating product pumps) Environmental effects are yet to be known. Potential risk to crew from leakages of superheated water throughout piping system. Latest concepts use heat exchangers. Entire ballast system is not heated. Ship s crews already deal with steam lines this shouldn t be any more dangerous. Latest research (U of M) has shown on-board effectiveness to be 30% for neutrally buoyant material (can include many phytoplankton & bacteria). Effective for particles larger 40 microns. Must be coupled with an additional treatment to kill the smaller bacterial and viral component (UV used in test aboard the passenger vessel Regal Princess with good results). Poor results with water containing a lot of suspended solids which limits attenuation of UV. Poor removal of larger organisms, very good results killing microorganisms Very effective scaled tests have shown up to 100% effectiveness for all sizes and classes of AIS Low flow rates may make this technology effective for vessels that carry low amounts of ballast. Excellent potential as a secondary treatment approach. Could be very effective AIS sterilizing agent but at high risk and cost. A great deal of engineering needs to be done to scale this technology to a ship in a safe and cost effective manner.

4 Expensive. Early ship Some risk to crew due to A very effective killer but tests used a very the numerous untested so far in a ship expensive distribution requirements needed to environment. system. Now looking at ensure ozone is produced in-line dosing, which properly. Ozone is also should be much cheaper. toxic. Additionally ozone produces same residuals Chemical Treatment: ozone generation (an oxidizing biocide) Chemical Treatment: chlorine. Can be accomplished in two ways - on-board chlorine generation and addition of commercial sodium chloride. May also be added as hypochlorite (bleach) or electolytically generated) Chemical Treatment: misc. Glutaraldehyde, juglone, hydrogen peroxide, periacetic acid, etc. There are other chemicals but these are the chemicals most often discussed on the Lakes. Expensive to deliver an effective dose for bulk freighters carrying between 3-4 M gallons of ballast. Piping, pumps, control boards & storage tanks would need to be added. Onboard generation increases shipping and addition of Numerous chemicals are being suggested to treat ballast, most are very expensive, especially to treat full ballast tanks. Chemicals show most promise for use on NOBOB s. as chlorine in salt water. Chlorine is highly corrosive at concentrations >10 ppm. It impacts ballast tank coatings & could pose a risk to the crew. Safety concerns can be alleviated by on-board generation of sodium hypochlorite. Prior to discharge ballast would need to be treated with a dechlorination compound. Safety threats include crew handling & storage issues & the potential risk to the environment. Effectiveness may only be possible at concentrations greater than 20ppm for resting stages. Chlorine does poorly in sediment & in water with a lot of suspended solids. Varies greatly and frankly much remains to be learned. U of Michigan is conducting studies on glutaraldehyde. All chemical treatments are probably greatly impaired in the presence of sediments and high suspended solid loads. Currently being tested on several ships engaged in the Pacific trade. Michigan DEQ & FEDNAV will perform a shipboard test this spring. Further testing needs to occur in a ship environment. Much controversy surrounds the use of chemicals to treat ballast. The primary issue is the concern many have about discharging chemicals into the marine environment. If a chemical could be developed that effectively eliminates AIS, is safe to the vessel & crew, and no threat once discharged, it may be a very useful tool to address the AIS threat from NOBOB vessels.

5 Lower end of cost Safe to the ship (except Copper found ineffective spectrum for chemical Al components) &crew against resting stages and treatment but discharge of copper high sediment loads. methodologies. at operating Elevating to effective Estimated increase of concentrations is harmful concentrations produces 0.53% of shipping cost to aquatic environment. significant toxic problems increase for No available methods for exceeds effluent chloride treatment. eliminating copper in concentration standards. Copper Ionic Release: operates by using an electrical current to disperse concentrations of copper ions into the water column Gas Supersaturation (hypoxia): this method involves removing dissolved oxygen by pumping inert gas (nitrogen) into ballast tanks, thereby killing organisms. Shore Based Treatment: Pumping ballast ashore for treatment Unknown, however, for a retrofit, additional pumps and piping as well as holding tanks would need to be installed. Very expensive; would need the land to build the facility & all ships would need to modify their ballast pumping systems to pump ashore. Could also anticipate significant operational delays. effluent. Safe for the environment, ship & crew. Risk does exist for leakage of inert gas into ship spaces. (anoxic organisms could also produce significant amounts of H2S, depending on organic content of ballast water. This gas would be a health risk for crew, and would be a problem for discharge in most U.S. ports. Safe for the ship & crew. Environmental safety is a concern since many ships start discharging ballast water prior to entry into port, for both loading and navigation purposes. Neither shore facilities nor lighters could effectively treat this water.) AIS such as bacteria, cysts & spores can survive in an oxygen free environment. Effective, however, ballast tank sediment residues could still provide a vector for AIS. Copper ion release provides a low-cost and ship/crew safe biocide option. However, at truly effective concentrations, poses a significant problem as the treated water exceeds discharge standards. No solution to this problem is readily apparent at this time. This approach has received a lot of press lately but a lot more needs to be analyzed before any conclusions are made. Testing thus far has only occurred at bench scale. Cost issues & who pays need to be resolved as well as locating suitable areas for treatment facilities.

6 Additional technologies in preliminary development: Ultrasound: In-pipe treatment of ballast water with high frequency sound waves which break down cell walls and cell membranes of target AIS species. Electro-ionization: Passing electrical currents through killing chambers that are plumbed into the ballast water piping system.

Environmental Engineering-I By Prof S S JAHAGIRDAR

L- 28 Disinfection Part- I Environmental Engineering-I By Prof S S JAHAGIRDAR Contents Disinfection techniques- Ozonation, u/v radiation. Chemistry of chlorination, chlorine demand curve. Types of chlorination,