Ballast water treatment methods focusing on the GLD (gas lift diffusion)Iven BonniciSubmitted to the Malta College of Arts, Science and Technology (MCAST) Institute of Engineering and Transport in part fulfilment of the requirements for the Ballast water treatment methods focusing on the GLD (Gas lift diffusion).July 2018 Authorship StatementThis dissertation is based on the results of research carried out by myself, is my own composition, and has not been previously presented for any other certified or uncertified qualification.The research was carried out under the supervision of Ing Ted Darmanin.Sign : ______________________ Date : ______________________Copyright StatementIn submitting this dissertation to the MCAST Institute of Engineering and Transport, I understand that I am giving permission for it to be made available for use in accordance with the regulations of MCAST and the College Library. Sign : ______________________ Date : ______________________AcknowledgementsFirstly, I would like to acknowledge the assistance of my Tutor Ing Ted Darmanin for his suggestions and supervision throughout my thesis, as well as giving me reference to other lecturers specializing in particular fields that gave me the necessary information I needed to complete my thesis.
Secondly, I would like to thank Mr Raymond Caruana and Mr Melvin Magri from the Malta Aquaculture Research Centre for sharing their knowledge in the field of marine life. As well as for their stoic patience in the guidance and providing access to the use of the laboratory equipment.Thirdly I would like to acknowledge the useful knowledge given by Dr Juan Jose Bonello from the Institute of Applied Science for sharing his knowledge in the field of micro biology as well as useful guidance in the evaluation of results.Finally, I would like to express my gratitude to my parents who gave me constant support throughout the years in my studies in marine engineering. AbstractBallast water is taken by ships to stabilize the vessel and ensure structural integrity in cases of loading and unloading of cargo, and during changes in draft due to change in water densities. During this intake and discharge of the ballast water, aquatic species enter with the water. These species can be invasive to the native waters in the location were discharged, causing ecological and economical disasters.
This research is intended to investigate ways to minimize and cease this transportation of aquatic species such as plankton and bacteria. During this thesis a ballast water treatment was built and tested by using the venturi principle. The equipment built uses pressurized inert gas, which as it is ejected out of the nozzle of the venturi, creates low pressure in the venturi enabling the water to enter due to change in pressures.
At this stage the water is subjected to low static pressures causing the water to turn into vapour, as it passes through a sudden expansion, the static pressure increases causing the vapour bubbles to collapse. The sudden collapse creates the cavitation phenomena creating mini implosions, which kill the organisms in the water such as plankton and bacteria. In addition, the inert gas causes a reduction in the oxygen level and pH in the water which further decrease the living organisms. This research shows the result from the testing performed on such treatment system, on three types of plankton and bacteria.
ContentsAuthorship Statement 2Copyright Statement 3Acknowledgements 4Abstract 5Contents 6Table of Figures 8List of Tables 8Introduction 92.1 The need for ballast tanks 92.2 The necessities of treating ballast water 102.
3 What is ballast water treatment? 102.4 How can ballast water be treated 102.5 Cases of aquatic marine invasion 112.6 Risks associated with the Maltese waters 132.7 Conventions and regulations related to ballast water 152.
8.2 Shore Based Treatment of ballast water treatment 162.8.3 Onboard Treatment Methods 172.8.3.
1 Ballast Water Exchange Method 18.104.22.168 Mechanical filtration and separation 192.
8.3.3 Disinfection using UV radiation 192.8.3.
4 Disinfection using Thermal treatment 22.214.171.124 Disinfection using Pulsed and Plasma electric fields 126.96.36.199 Disinfection using Ozone 222.
8.3.7 Filtration using Biocides 222.8.3.
8 Gas Lift Diffusion (GLD) 233.0 Methodology 25Introduction….. 253.1 Theory behind the effectiveness 253.2 Testing method for Plankton 273.2 Testing method for Bacteria 313.
3 Precautions taken 344.0 Results and Discussion 354.1 Results for Plankton treatment 354.
2 Results for Bacteria treatment 385.0 Conclusion and Suggestions for further research 405.1 Conclusion 405.2 Suggestions for further research 415.2.1 Developing to a full scale in suppling large volumes of inert gas.
415.2.2 Reducing the cost per treatment 425.2.2 Testing on a wider range of species 425.2.
4 Treatment analyse 425.2.5 Other applications 426.0 Gantt Chart 437.0 References 448.0 Appendix 478.1 Venturi design 478.
2 Treatment data 48 Table of FiguresFigure 1 Ballast tank operation 10Figure 2 Cyanobacterial Blooms in the 1990’s 13Figure 3 Lion fish 14Figure 4 Oil Rig entering Grand Harbour 15Figure 5 Guinea angle fish 15Figure 6 Land-based treatment 17Figure 7 Flow through ballast water exchange 19Figure 8 Mechanical with UV treatment schematic diagram 21Figure 9 Gas Lift Diffusion 25Figure 10 Cavitation formation 27Figure 11 Venturi Design 28Figure 12 Copepod 29Figure 13 Rotifer 29Figure 14 Artemia salina 29Figure 15 Sample without magnification 30Figure 16 Sample under microscope 30Figure 17 Dissolved oxygen meter 31Figure 18 pH meter 31Figure 19 Refractometer (Salinity) 31Figure 20 Water samples 32Figure 21 Preparation of the bacteria samples inside the biological cabinet 33Figure 22 Preparation of the agar in a water bath 34Figure 23 Counting of bacterial colonies 34Figure 24 Plankton treatment results 38Figure 25 Bacteria treatment results 39Figure 26 Counts for results 40Figure 27 Petri dishes prepared for counting 40List of Table Table 1 Treatment test on Artemia 36Table 2 Treatment test on Rotifers 37Table 3 Treatment test on Copepods 37Table 4 Bacteria treatment results 392. Literature Review IntroductionThis chapter discusses ballast water treatment methods with special emphasis on the GLD (Gas lift Diffusion). During the years of the maritime transportation there were several incidents were the marine life was threatened due to the disposal of contaminated ballast water. Although their impact is not instantly seen as that of oil pollution, these still left a negative impact on the environment causing a ripple effect on the economy. Such incidents can occur from untreated water from ballast tanks which is transferred from one continent to another, carrying different kinds of bacteria and other aquatic species which are released when the vessel needs to drain its ballast tank. Regulations related to ballast water treatment are controlled by MAROL conventions. The need for ballast tanksBallast tanks are compartments which weigh the ship down and lowers the centre of gravity by sea water.
Ballast tanks are found in every vessel as to increase safety by allowing the ship to resist damage. These are regulated by the SOLAS conventions (Safety of Life at Sea) for both passenger and cargo vessels. Crude oil tankers are more prone to transfer invasive aquatic species between destinations. Unlike other vessels, they sail in ballast condition for half of their life.
(IMO, 2017)Apart of stability, ballasting will contribute to propulsion efficiency and as an easy adjustment to decrease draft for the entry of shallow waters or rough seas. Ballast are adjusted when loading and unloading cargo to keep a constant draft. Depending on the vessel, ballast can be found in the double bottom extending across the breath of the ship, in wing and hopper tanks (upper corner) connected to pumps which pump the water in and out. (Bruno, 2017)2.
2 The necessities of treating ballast waterAs explained in the following paragraphs, apart from the sea water, other unwanted harmful species of bacteria including Cholera, plankton such as Zooplankton also travel along with the vessel, from port to port. As the vessel unloads the cargo, the ballast tanks are filled with sea water along with the bacteria and plankton, and as soon as the vessel reaches its destination and loads on the cargo, the ballast are emptied, contaminating the local waters with the foreign species. These invasive aquatic species that may have survived the journey could easily multiply and effecting the native environment, causing ecological problems, threat to human health and the local economy. (IMO, 2017)2.3 What is ballast water treatment?Water ballast treatments are methods to treat the sea water and clean it from any bacteria or plankton which was picked up by the ballast pumps. These treatments are subcategorized into two, a physical-liquid separation and disinfection.
These treatment methods are restricted to meet with the required effectiveness controlled by the IMO (International Maritime Organization) for ballast water management. The restriction made it mandatory for ships to install such treatment systems. The shipping company must choose one system over another based-on space available, safety of the crew, effectiveness of treatment, cost, duration and ease of installation, and environmental friendliness. (maritime-executive, 2017)2.
4 How can ballast water be treatedA vessel can treat the water either onboard in entry or during voyage or by shore-based plants. As are going to be discussed in detail in section 188.8.131.52 Cases of aquatic marine invasionAs around 10 billion tonnes of ballast water are carried from one continent to another each year, with it thousands of marine species are also carried.
This transferring of ballast has been going on for years and around 200 years ago soil was used as ballast instead of water. This contamination has been proven as soil of different kind was found around the Maltese grand harbour. This transferring of ballast carries with it live marine organisms which most are killed as their ability doesn’t allow them to survive in the new water.
However, those which survive would reproduce and become invasive, causing alterations to the local ecology contributing to threat to fisheries and therefore causing risk to human health by the contamination of seafood. The following are only a few cases of this phenomenal: In 1982 the Comb jelly fish native species in north America was transferred with the ballast water to the Black sea, which survived on eating zooplankton and eggs of some species fish. With contrary to the marine life in north America, the new habitat had no predators causing an invasion in the Black sea. The Comb jelly fish became so invasive that it totalled to 90% of the total biomass of the Black sea which invasion continued to spread through the Azov sea. This contributed in the collapse of the commercial fisheries business, which some study claims that this industry in the Black sea totalled to 1 billion dollars since the beginning of the invasion. Apart from these consequences, the population of dolphins which used to survive on these fish were noticed to have dropped significantly, as well as a reduction in the oxygen level in the water.
(WWF, n.d.) Since 1860 the beginning of the shipping industry in the Bahamas, which continued to increase in the 1950 by the development of the freeport in grand Bahamas, countless ships have passed and transferred the ballast water to the native waters.
The Bahamas waters are full of marine life as it is composed of 95% marine with topical shallow waters. An invasive species of fish known as the Lionfish has dramatically invaded the waters, this same species has invaded other waters including Gulf of Mexico, Caribbean seas and started to infiltrate the Mediterranean where the impact hasn’t yet been estimated. This species survives on eating anything that fits into its mouth such as young octopus, squid, sea horses among others. In this area business is mostly based on fisheries, tourism, the 2.1-billion-dollar diving business which contribute to effect hotels, restaurants, and the rest of the tourism business. (Harrell, n.d.
). Regarding human health, the ballast tanks also carry viruses and bacteria such as Cholera, which is transferred through the fish consumed by locals as food causing health problems which can lead to death. The Cholera virus had already infiltrated Peru in 1991. It was carried by ballast tanks from Bangladesh which caused 10000 deaths in 3 years.
(Thomas, 2016) Over the last 20 years the shipping industry in the Baltic seas have increased exponentially. This contributed to the delivery of over 120 NNS were 80 of which are self-reproductive and pose a potential threat. Most of these species came from Ponto-Caspian and North America. The local marine life has been altered were these NNS have outnumbered the native species.
According to the Helsinki Commission for of these species have high potential threat to the eco system. These being: Ponto-Caspian water flea, these species effect the local fish by clogging up their gills ending up killing them by suffocation. This was first noticed in 1990s were it caused harm in the marine life and its eco system and the economy due to the effect to the fishery industry. By 1998 it is believed that this species spread to Stockholm and Gotland. Dinoflagellate has formed blooms in Archipelago Sea.
Similar Blooms appeared in 2010 around the Israeli coast which spread over 500km by 10 km which was calculated of consuming 100 000 Tons of Plankton over the 100 days of summer. North American Comb jelly fish and its effects were discussed in detail in the previous paragraph, were these consume juvenile fish, and having no natural predators, it effects the entire food web becoming predominant over the native species and effecting negatively the local industry. In the 1990s a power station in Israel has been shut down due to a clogged coolant filter by Phyliohiza Puntata jelly fish causing 60000 dollars of damage, the same has happened in China in 2008 with more than 4000Tonnes of Aurelia Aurita jelly fish. (Turner, 2015)2.6 Risks associated with the Maltese waters The Lion fish as already mentioned in the previous paragraph can kill humans due to its 18 poisonous spines which can cause paralysis and necrosis.
Although not yet found around the Maltese coastal waters, the species were spotted and invaded the eastern part of the Mediterranean causing devastation to the environment. After the release of these lionfish in Maltese waters, invasion is very likely as it can reproduce 50000 eggs every 3 days, causing a quick invasion of the coast. By comparison to the same problem in other seas such as Bahamas and near the Cyprus seas, it will lead to hard and potentially whipping out the native species contributing to losses to the fisheries around Malta. (Laursen, 2016) The latest alien species with a big connection to ballast water, is the Guinea angle fish as seen in figure where it was spotted near Senglea (port area). This Species is normally found near coastal waters of west Africa and the Atlantic Ocean were warmer seas are found. It was connected to ballast water as in the same period when this species was spotted, an Oil Rig was towed from West Africa, which was towed where the angel fish were spotted.
(Deidun, 2017)The cases mentioned are only few examples of many, as the problem associated with ballast water have impacted nearly every part of oceans and seas including rivers and fresh water lakes.2.7 Conventions and regulations related to ballast water TreatmentUnder the IMO (International Marine Organization) stands MARPOL (International convention for the prevention of marine pollution from ships) The MARPOL convention was started in 1973 which was later revised in 1978. The IMO holds regulations which manages the ballast water from ships.
In 1997 the IMO adopted guidelines for the control and management for ships ballast water, were later in 2004 a convention to manage ships ballast and sediment was adopted. Before the adoption of the international regulations, port states round the globe adopted their regulations related to ballast water from ships coming from terrestrial water. These evolved into the international ballast management plan which was to be used in international seas. Under the convention there are a total of 22 articles which are related to ballast water. The convention related to ballast management entered into forced recently on 8th September 2017.
In the convention , the following is stated for ships traveling in International waters: The discharge of ballast water is to be conducted through ballast water management plan. (section A) Ships are required to have a ballast water management plan; which plan is specified for each ship. (section B) The vessel is to have a record book, which is to record any circulated, treated and discharge of water, swell as in case of any accident (spill of ballast) is recorded as well.
As for ships performing ballast water exchange method, ships are to efficiently exchange 95% of volume, while for the flow through method exchange 3 times the volume (D-1) Ballast water performance standard which indicates the acceptable boundaries of the effectiveness of the treatment system. (D-2) IMO is to evaluate and verify that the performance is up to standard and up to criteria: To be environmentally friendly Economically feasible Biologically effective in killing harmful organisms (D-5) The Ballast water system is to be surveyed and up to the certification requirements. As for the initial launch of system, renewal and annual surveys which comply the record book as well for the ballast water tanks. (Section E) As by 2024 all vessels are to have a ballast water treatment system which is approved and within the D-2 standard boundaries. (IMO, n.d.
) Shore Based Treatment of ballast waterShore based plants could be either land based or onto a floating platform. Most shore-based plants are aimed for crude oil tankers and are installed at the receiving port were the offloaded water is treated. These plants are readily available as they have been used for waste water treatment and are proven to be cost effective and reliable. They are best used on predictable routes, such as between the West Coast of United States and Prince William Sound Alaska. (Wisconsin Department of Natural Resources, 2007)The main advantage is the readily availability of the system as it is already in use for years for the treatment of waste water. The system being focused on the treatment of ballast water needs to have dedicated personnel to monitor the process effectiveness and apply immediate changes to ensure proper treatment.
As compared to many scaled versions onboard every vessel, the system is more cost effective. The overall costs are lower than many scaled versions onboard each vessel. As for ship owners they don’t have to stop any voyages to install the ballast treatment system. They also eliminate the problem caused by the lack of space onboard ships since to accommodate such system filtration, piping, and generators to power the extra load extra space would be needed. Port patrol can oversee and ensure the proper disposal of the water. Shore based treatments, come with a major drawback being not to allow variations in trade routes. The plant requires a large area and decks to fit the piping from the vessels which are to be easily adjusted to accommodate various sizes of vessels types and height.
A discharge manifold is to be fitted to the vessels and docks, as well as large pipework system. The construction of such system may not be viable if not used to the full by large number of vessels. The port will have to offer the required space which may not be the case for every port that may lack space, apart that if this one system fails and goes out of service it will lead to delays in shipping.
(Stemming the Tide, 1996) Onboard Treatment Methods Ballast Water Exchange MethodBallast water exchange is a method that requires the changing of the ballast water picked up from ports and coastal water and exchanged with the open ocean water, as stated by the IMO (International convention for control and management of ships ballast water and sediments B-4) being at minimum 200 Nautical Miles from land and being at least 200m deep. The reason for this method is that coastal waters are much richer with marine life than open ocean water. As stated by the IMO the ballast should change 95% of the total volume in tanks to be effective, changing three times the volume of each ballast (D-1). This method is only permitted if the weather would not pose a hazard and put the life of the crew and vessel in danger of reducing stability, as well as in seasonal area of cyclones and typhoons which may add additional forces on vessel such as exceeding the minimum and maximum draughts.
The procedure must be performed in the appropriate sequence, and the entire water exchange should be monitored and controlled (wartsila, 2017). Ballast water exchange can be performed by either the Flow through method Dilution method Sequential methodFlow through method, uses pumps to propel sea water from the bottom of the tanks, and the tank is overflowed from the top of the tank. This method is to replace 95% of the water when conducted to replace 3 times the volume of the ballast. The Flow through does not cause effect on stability and hull girder stresses. When compared to the other 2 methods it does not exert shear force and bending moment on the vessel. Constant monitoring of over and under pressures are necessary for keeping the structure of the vessel in a safe manner. It is necessary to have the proper ventilation that will keep up with the inlet water flow.
As some vessels have their vent outlet on their decks, when the ballast exchange takes place the excessive water will cause a hazard to the crew and will result in freezing in low climate conditions. As a result from the freezing, it will halt the completion of the water exchange. To overcome this problem a proper piping system having separate inlet and outlets is recommended. The piping network is endorsed to have interconnecting pipes from one ballast to another and avoid having overflow on the decks. (Ocean Engineering, 2014)Dilution method allows the ballast tanks to be at the same level during whole procedure.This way it will not jeopardize the stability of the vessel and also preventing additional stresses on the ship’s hull. If the system operates without any difficulties, it will also keep a constant pressure without excessive internal pressures that may turn up with the overflow method.
This method is effective and simple as well as economical to manufacture. The deck and crew are never in contact with the outlet water. The drawback of this method is a failure in one of the pumps as: Suction pump failure will risk over pressurizing the tanks Inlet pump failure will cause a decrease in the pressure and effects the stabilityTo overcome the mentioned risks, alarms are set to detect over and under filling. The system is preferred to have a permanent governor to ensure the appropriate water level.The final exchange method being the sequential method, is made by completely emptying the ballast tanks from the coastal water and are refilled with the open ocean water. This method is completed by performing one or more ballast tanks at a time.
This method compared to the previous two methods, ensure a higher percentage of effectiveness. However, it puts the vessel in the risk of structural stresses, longitudinal stresses, and a reduction in stability. Other concepts such as the free surface effect contribute to sloshing, reducing further the stability.
During the replacement of the water in the peek tanks would affect the trim. To minimize this risk the exchange is performed when the sea condition is its best. Proper planning of tanks being emptied are to be calculated carefully to ensure maximum safety. (SE, 2013) Mechanical filtration and separationThis method of filtration uses sedimentation and surface filters which when the water flows through them, any solid particles or organisms which entered along with the ballast water would be stuck in the filtration. These filtrations need regular maintenance and cleaning although some filtration units have a self-cleaning process which will clean and dispose the waste particles performing a reverse cycle wash. This is to minimize fouling and keep the system working effectively and efficiently.
The solid particles which are separated from the water are either thrown back into the water where it was taken or treated onboard. (Kalinbacak, 2015)An alternative method of mechanical filtration is the use of the hydro cyclone which by means of high velocities the solid particles are pulled on the outside by means of the centrifugal force produced inside. As the previous method of filtration, these are only capable of removing the heavy particles. As tighter regulations and restrictions are being imposed, this method alone is not enough. This method is used as the first stage and must be accompanied by stage two filtration by using physical or chemical treatment such as UV light or Biocides to kill the organism.
These are going to be described in further detail further on. (Lloyd’s, 2012) Disinfection using UV radiationUV radiation has been used for disinfection for many years as it was used and optimized in other sectors such as in waste water treatment. It has proven to be one of the best effective treatment for the disposal of invasive species. Current UV treatment uses waves of 254 Nano meters which makes the bacteria and pathogens inactive to reproduce as the UV destroys their DNA. (Heraeus, 2017) The main advantages of this system are: Low maintenance and running cost No discharge of hazardous chemicals Environmentally friendly Decreases corrosionIts main drawbacks are that it can only be used as a second stage filtration, as it requires clear water, as well as the lamp will decrease efficiency if covert by fouling.
Although this problem is considered minor as new technologies have adopted wipers to the ultraviolet lamp to remove the fouling. (Ranveig Ottoey Olsen, 2015) Disinfection using Thermal treatmentThermal treatment is another method of killing organisms. This process requires a temperature of 35oC to 45oC for a specified period. This treatment was tested in Australia and proven to be effective for large organisms but lacked effectiveness for microorganisms.
This treatment was tested onboard a modified ship were the larger organism were killed at a temperature that reached 40oC. (Corrina Chase) For this method to be efficient the heat treatment must be connected to the engine cooling system, as to eliminate the use of heaters. This installation would require the installation of heat exchangers and pipework’s which will need planning and installation time in dock. Another drawback of such system is that onboard larger vessels such as oil tankers, for the system to be effective would require additional boilers to keep up with the ballast water mass, and to treat the total amount of water in the required time. (Advisory, 2005) Disinfection using Pulsed and Plasma electric fieldsPulsed and Plasma electric fields is still in the developing stage and so the technology is still to be tested on a large scale for ballast treatment.
The research and tests done so far are promising in its effectiveness, in fact one research claims that it is 99% effective, so theoretically it should work on a bigger scale to destroy the non-indigenous species. This technology works by short burst of energy which is transferred through the water and organism and electrocute them. The electric pulse is conducted between 2 metal electrodes, with such energy burst at a high-power density.
As for the pulse plasma, a mechanism is inserted inside the water compartment, where with the same principle of high energy pulses extinguish the organisms.As promising as this system sounds, even at the development stage, it comes at a price. The system must be used as a second stage filtration after a mechanical filtration such as cyclone to maximize its performance.
The system may produce carbon dioxide from the decomposition product. The estimated price for such systems are approximated to be $150k for plasma and $350k for the pulsed electric field. The system has also a high running cost which are estimated to be $150 per hour of operation and $360 per 25000m3 of water. This price along with the requirement of specialized personnel will make other systems more viable, although further research on this system could reduce its price to become more economically feasible. (Advisory, Electric Field Technology) Disinfection using OzoneThis method of sterilization uses the ambient air and takes away the nitrogen, this results in a high level of oxidization property, which destroys any bacteria, inactivating any microorganisms, and plankton as the zooplankton and phytoplankton. In addition, for the effectiveness of the systems, the ozone has to react with chemicals found naturally in sea water, the resulting in an acid known as Hypobromous which acts naturally as a disinfectant. (NK, 2017)This method does not produce any by-products. To produce the ozone, electric current is passed through the air between 2 electrodes, where 85% of the energy is wasted into heat. As compared to other methods such as chlorination this method is considered much more expensive due to the specialized equipment. (Ozonetech, n.d.) Filtration using BiocidesThis method of treatment has been used for years for the treatment of potable water on land-based applications. As for the treatment of ballast water it is relatively new, the doses of chemicals include Ozone, Bromine, Hydrogen peroxide, Glutaraldehyde, Chlorine dioxides among other organic acids, which are to be mixed with the ballast water for maximum effectiveness.These chemicals are required to be: Effectively killing a wide range of non-indigenous species (NIS) Having a fast decay rate Degrade into non-toxic compound prior dischargeAs to this date only ozone has been proven feasible for large scale ballast treatment. This is mostly due to the corrosive properties which can cause damage to the ship and harmful to its crew. Other chemicals as already mentioned are still being tested but has not yet been verified as safe to use. Chemical treatment solutions are the most effective for treating the water and has been proven to kill microbial organism and are quick and easy to apply. Even though it does not require any specialized equipment to operate, it still requires a safe storage area. The large quantities of highly corrosive properties are potential danger to the ship’s crew. Some treatments use 1-5 parts per million, but for some waters treatment ratios can go up to 10000 PPM which involves storage of large amount of chemicals. One reports states that for large tankers the treatment can cost up to $500K per application. (Corrina Chase) Gas Lift Diffusion (GLD)Gas Lift Diffusion as stated by its name uses inert gas given out by the inert gas generators (refer to 5.2.1), and by means of specifically installed pipework. The gas is compressed via normal marine compressors to the bottom of the tanks, were it is passes through the diffuser and is mixed with the ballast water where the treatment is induced. This method of treatment was originally planned for LNG/ LPG and bulk carriers. The system ensures proper mixing with the ballast to ensure that 100% of ballast water is treated by using natural fluid dynamics built inside the diffuser to stir the water and diffuse the inert gas throughout the water. As this occurs the oxygen is drawn out of the H2o , increasing the CO2 level which simultaneously reduces the pH of the water contributing to killing the organism and bacteria such as E coli as a result of Hypoxia and Hypercapnia. In addition, Cold Harbour Marine holders of the patent for this system induced micro bubbles which creates ultra-sonic shockwaves which disrupts the cells of such organisms. (Marshall, n.d.)So, what makes the GLD system stand out from other treatment methods? The treatment is conducted in tanks instead of in line, which eliminates delays due to low flow rates limited by treatment Delays occurring from down time of ballast pumps is eliminated No filters are needed or back flush needed which can cause to pressure drops No added power is required No moving parts ensuring 100% reliability (claimed by CHM) Reduces corrosion by 65% contributing to maintenance down time and cost in dry docks. A report from 2013 stated that the GLD is not affected by solid particles or increased salinity levels and temperature differences. The GLD has been an approved method of treatment under Flag state by the UK maritime, coast guard agency and Lloyds register. (Maritime, 2013)The gas lift diffusion is effective due to the effects of hypoxia and hypercapnia on the species in the ballast tank. The reduction in the Ph level in the water also have an impact on the living organisms. As a definition the hypoxia is the word given when any organisms such as plankton are affected by the lack of oxygen present in the water, while hypercapnia is the word given for the elevated levels of carbon dioxide in the water which also impacts the living marine organisms found in the ballast tanks. One of the main advantages this system offers over alternative treatment methods is that it can treat the water during the transportation rather than during charging or discharging of the ballast tanks which will as a consequence decrease the time of the operation, which will reduce the costs for ship owners.The Gas lift diffusion as stated by Cold Harbour Marine states that the risk of corrosion in the tank can be minimized by 65% under normal operating conditions. This will affect in reduction of cost and time as well in the long run when the ship will need repair in shipyards. Methodology IntroductionThis chapter discusses the equipment used and the procedures followed to demonstrate the GLD treatment system. It also holds the approach taken in verifying if the system was effective or not. The first section will focus on plankton while the second part will focus on the bacteria.3.1 Theory behind the effectiveness The venturi treatment system was set up as seen in Figure 10. The flowrate was optimized by adjusting the Co2 pressure, and fine tuning the distance between the throat and the nozzle denoted by (i) in Figure 11, while the pressure was monitored and regulated by a pressure regulator. A carbon dioxide gas was used as the driving fluid in the venturi, which causes a drop in static pressure in the suction nozzle, which causes the outside atmospheric pressure to drive the water to flow through the venture device. This can be seen visible in figure 11. The gas used also drops the oxygen level in the tank. The carbon dioxide also drops the pH level, by changing the water properties, as a consequence the living plankton, bacteria etc, would struggle to stay alive. The venturi was designed and built in a manner which causes cavitation. Normally cavitation is avoided, however the imploding bubbles caused by cavitation will disrupt the cells of the plankton and other organisms in the ballast water. The theory of cell disruption caused by cavitation is explained in detail in the book ‘Enzyme Technology’. (Martin Chaplin, 1990) Combined with drop of saturated oxygen and pH maximises the effect on extermination and preventing the spreading of alien species. As shown in Figure 10 from point Pv to Pc the static pressure drops, creating a difference in pressure compared to P1. This pressure difference allows for the ballast water to enter at Pv, as the atmospheric pressure is greater than at Pv, the pressure at P1 pushes the water in. By the end of the contraction section Pc, vaporisation starts as the pressure drops below the water vapor pressure. As the pressure starts to incline again and goes above the vapour pressure, the water droplets begin to collapse, creating mini implosions known as cavitation. The theory states that these mini implosions will disrupts the cells in the bacteria and other organisms.The following graph represents the change in static pressure relative to the position in the venturi device. Were P1 represents the pressure of fluid at entry of the pipeline. Pv represents the pressure of the fluid at the entry of the venturi (contraction part), Pc represents the pressure at the end of the contraction were cavitation is most likely to occur and P2 represents the static pressure of the fluid as it leaves the device.3.2 Testing method for PlanktonA venturi was built as seen in Appendix 8.1 was placed in a 16-litre tank which was to hold the water with the species. A plankton samples was chosen on basis of accessibility and previous case studies regarding marine invasions, these being Copepods, Rotifers and Artemia Salina The Rotifers and Artemia Salina were cultivated by the aqua culture centre, while the copepods were bought from a local retailer. Regarding to the salinity of the water contained in the plankton environment, the water in the testing tank was matched with the same salinity. This was achieved by filling the tank by either brackish water (lower salinity) or direct from the sea. The temperature was also matched so as not to give a thermal shock and disrupt the results of the tests. The sample was then released in the water, and a sample was taken as a control along with the pH, salinity, and oxygen content in the water.The following figures shows a magnified plankton of each plankton specie tested. Figure 12 CopepodThe treatment was then initiated, and a sample of water was collected at 5-minute time intervals along with the pH, oxygen level and salinity and noted in a table. Each specie underwent treatment a total of 3 times to test for repeatability. The samples were then placed on a Petri dish and analysed under a digital microscope from which the following equation deduced a percentage. ((Total plankton alive) x 100%)/((Total plankton) )To work out a fair percentage, a 20 ml sample was extracted from the testing tank, were a 5ml was taken from the 20ml, and put on to a petri dish with a counting grid. Making a count per square cm, for every 5ml, and taking an average. The counting was difficult to make with the naked eye, as the plankton swim in a rapid motion, and would result in a systematic error. To make up for this error a digital microscope was used, enabling for an accurate counting. The projected view from the microscope would be shown as seen below. The screen shot shows the copepods under a microscope.Readings of pH, oxygen content and salinity were taken by dedicated instruments, each following a procedure to ensure accurate data. Starting from the oxygen meter, were it read the amount of dissolved oxygen in the water, as a saturated percentage. The probe was stirred gently until the stable reading could be read. While the pH probe was held steady until the reading settled. As for the salinity, using a pipet a drop of the sample was placed on the reading end, and after directing the probe to light, the reading was carefully read. The Following three measuring equipment was used to gather the data from the testing.3.2 Testing method for BacteriaThe procedure for the testing of bacteria were slightly different than that of plankton. The tank was filled with brackish water as it was made for the plankton. However as to ensure that the water contained bacteria, a sponge from the filtration section of the fish tanks was placed in the testing tank. After it was left for a few minutes in the tank while stirred, the initial temperature, salinity pH and oxygen content were taken. As to prevent contaminating the results the pH, Oxygen and salinity were not taken during this treatment test. By using sterilized pipets and sterilized sample bottles, a sample was taken as a control. Which were immediately placed in a cool environment until all testing was conducted. The treatment was initiated, and samples were taken every 20 minutes. After the treatment was finished, the samples were taking to the Institute of Applied Science, were in the micro-biology lab. All the samples were prepared for evaluation inside a biological safety cabinet, as seen in the photo below. This will reduce the possibility of contaminating the samples. The pour plate technique was used to evaluate the number bacteria in the water samples: By using a sterile pipette as shown in figure 23 an exact amount of the samples containing 1ml was placed in the petri dish. The tip of the pipette was replaced for every sample as to minimize the risk of contamination. An approximate 500 ml amount of Agar was prepared in a hot water bath to change its state to liquid form, as seen in figure 16. The petri dishes were filled with approximately one third the volume with agar followed by tilting and swirled gently the petri dish to mix evenly. It was then left to cool for about 10 minutes, were it was solidified and cooled. The lid was closed back, and the petri dishes were placed inside an incubator for 24 and consecutively for another 24 hours at a temperature of 37 oC. All the labelling was made at the bottom part of the petri dish and placed bottom side up inside the incubator. After the first 24 hours the samples were taken out of the incubator, placed in front of a dark back ground and counted. The dark background helped to make counting easier. The bottom plate was marked as seen in figure 23, to ease counting. The counting was made for each sample and recorded in a table. After a further 24 hours the same procedure was conducted on the same samples. The numerical data was inputted in the following formula to determine the bacterial count per 100ml CFU x dilution factor x 1/aliquot = CFU/mLWhere the CFU is the count of bacteria (dots), the dilution factor being the sample mixed with distilled water to ease counting, and aliquot is the portion of the total sample were in this case was taken per 1ml. However, this was not necessary as the sample was not diluted with distilled water because the sample could be counted easily. If the bacteria colonies were too much to count, a new test would have to be made which involves mixing 1ml of the sample with 10ml, 100ml an 1000ml of distilled water. This is to make counting easier and then placing the values in the above formula to get counts of colonies per 1ml.3.3 Precautions taken The measuring equipment was calibrated before use, as well as cleaned between tests. The pH meter was rinsed in deionized water, the electrode was then placed in a buffer with known pH value, where the calibration took place. (A buffer is a mixture of light acids were its pH changes are minor and is used to calibrate the equipment) The salinity meter was calibrated by dripping an amount of the calibrated solution, were the meter was adjusted to the known source, were it was rinsed again with distilled water. The dissolved oxygen meter was first given a visual inspection, to ensure the membrane is in good condition. It was left in stable environment with no wind currents, were calibration took place. As for the readings of the test the probe was stirred gently to achieve a good reading. The tank was cleaned and rinsed with fresh water between samples. The samples were always compared to a control, as samples may not contain 100% live organism. The working area was cleaned with alcohol to eliminate any foreign bacteria which could contaminate the samples.4.0 Results and Discussion4.1 Results for Plankton treatmentThe Following tables contains the mean calculated readings from the tests conducted on Artemia, Rotifers and Copepods. The actual readings can be found in the appendix 8.2. The readings regarding dissolved oxygen, pH, temperature, and salinity were read from the measuring instruments, while the count of species was deduced from the total of living plankton per total plankton in the sample worked as a percentage.Table 1 Treatment test on ArtemiaSpecies: Artemia Time(minutes) Dissolved oxygen (%) pH TemperatureoC Salinity (%) Count of species (%)Control 82 6.02 19.3 40 705 6 5.44 19.0 40 10 4 5.40 18.8 40 6015 3 5.38 18.3 40 20 3 5.40 18.0 40 5025 3 5.25 17.5 40 30 3 5.26 17.4 40 2535 3 5.24 17.1 40 40 3 5.18 16.9 40 5Table 2 Treatment test on RotifersSpecies: Rotifers Time(minutes) Dissolved oxygen (%) pH TemperatureoC Salinity (%) Count of species (%)Control 91 6.57 18 24 805 6 5.28 17.8 25 10 4 5.21 17.6 25 7015 4 5.20 17.6 25 20 3 5.17 17.3 25 5025 4 5.19 17.2 25 30 3 5.19 17.2 25 2035 3 5.16 17.1 25 40 3 5.16 16.6 25 0Table 3 Treatment test on CopepodsSpecies: CopepodsTime(minutes) Dissolved oxygen (%) pH TemperatureoC Salinity (%) Count of species (%)Control 82 6.41 18.3 40 1005 5 5.25 17.8 40 10 4 5.21 17.7 40 10015 3 5.20 17.8 40 20 5 5.19 17.5 40 7025 4 5.19 17.2 40 30 3 5.16 17.3 40 3035 3 5.16 17.3 40 40 3 5.17 16.5 40 5The graph above shows clearly that the treatment was well effective on plankton species which is one of the species that are pronoun to cause harm on native species. However, the data also shows that an approximate 5% of Copepods and Artemia were able to resist the treatment test, indicating that the duration of the treatment was not enough. It can also be concluded that not all plankton species are affected in the same manner, therefore other species which were not tested may be more resistive and would have been able to survive the treatment. Having said that the overall conclusion for treating of ballast water using a venture device on plankton was successful upon these 3 species.4.2 Results for Bacteria treatmentThe following data holds the results from the bacterial analyses from the treatment. The 24 and 48 hours in incubation table refer to the total count visible on the petri dish at the specified period. While the CFU represent the count, the bacteria present per specified amount, which in this case being the total Colony Forming Units of bacteria present in 1ml.Table 4 Bacteria treatment resultsDuration of treatment (minutes) 24 hours in incubation CFU / 100ml(24 hours) 48 hours in incubation CFU / 100ml(48 hours)Control 125 12500 161 1610020 110 11000 143 1430040 132 13200 138 1380060 90 9000 124 1240080 113 11300 143 14300Each dot on the petri dish as the one marked with a red circle represents a colony of bacteria, which is the total of dots that add up to the total of colonies after incubation.The results conclude that the decrease of bacteria after the treatment have decreased by a minor percentage this shows that bacteria can resist more than other species tested and may require higher pressures of carbon dioxide, as it will enhance further the caveating effect described earlier as well as reducing the oxygen content and pH of the water. As the treatment results shows a reduction over time, this may indicate that the treatment needs to be run for longer periods of time. The test was conducted on one treatment test, in the presence of time, future testing of this treatment method should have test replicates this is to ensure a more solid and reliable result. As well as repeating the test at least 2 times.5.0 Conclusion and Suggestions for further research5.1 ConclusionBased on the three species of plankton samples tested, the treatment solution performed very well. However, for specific species such as the rotifers the duration of the treatment would ideally be extended over a longer period. The combination of reduction in pH, Oxygen and the cavitating effect causing mini implosion makes it effective on such organisms.As for the treatment on microbial level, the treatment result was not as promising, there was a minor reduction but not very significant. The main concern about the set up was that the pressure at the end of the venturi device did not go below the vaporisation pressure. This lead to preventing cavitation from forming and creating the necessary implosion that will disrupt the cells of the bacteria. In my personal view I strongly believe that if the system is refined to create lower static pressure, cavitation is enhanced, and the treatment would be effective on these micro-organisms. Taking into consideration that this treatment method has no moving parts, enables the whole system to be very reliable. It is also cheap to produce and can be run by the inert gases generated by the main engines which were going to be wasted anyway. From these benefits it can be concluded that the system has a potential in the market for ballast treatment. Having said that there is room for improvement. In addition, taking in consideration the repercussions that other substitute systems may impose on the environment and safety, concerning primarily the stability of the ship and health hazard that the crew may face, makes the use of inert gas system more beneficial. Regarding the possible side effects on the environment that other systems may have on the environment, the inert gas system does not use any chemicals, so as soon as the ballast water is released back in the sea it is going to be mixed without any harmful chemicals that can disturb the native habitat. When going under treatment the carbon dioxide and nitrogen will affect the oxygen content and pH in the water, but after treatment is done and by the time the ballast water is to be released back in the sea, it will neutralize the pH and as it is released the water will be re oxygenated. As regarding stability and safety of the ship and its crew, the treatment does not require any exchanging of ballasts, so it will not have any consequence on the stability and risking the ship to capsize like the traditional method of ballast water exchange, which cannot be operated during storms and heavy weathers, and have possible risks even in calm seas. This makes the venture method stand out in flexibility, as it can be used in any ballast condition, and will conduct the treatment without any harm to the native environment. Suggestions for further research Developing to a full scale in supplying large volumes of inert gas.As mentioned before, the testing was done using readily available on the shelf Carbone dioxide, which can be purchased from specialized retailers. The testing was made to a 16-litre water sample, however the ballast tank of a large tanker has a capacity of approximately 200 000 m3, so it clearly wouldn’t be feasible using such readily available carbon dioxide. Now the engines onboard a ship with large capacities generate tonnes of CO2 and Nitrogen, which is inert gas that can be used for such application to treat ballast water which in many cases was going as waste to the atmosphere. This is because when fossil fuels such as low sulphur diesel, LNG or flea gases are burned, their generated exhaust contain less than 5% of oxygen and large amounts of carbon dioxide and nitrogen. However, some also produce Sulphur Oxide (Sox), Carbon Monoxide (CO) and Carbon as a particulate matter. So, a cleaning method is incorporated to remove the gases and particulate matter which is harmful, this is done by using a scrubber which is then pumped down to the ballast tank. The scrubber work on the following principle : the exhaust gas enters the scrubber from the bottom. As the gas pass through the scrubber, sea water is sprayed on the gas, this will remove any particulate matter, as well as remove the sulphur oxides. This happens as the sulphur is acidic and the sea water is slightly alkaline, so they will neutralize. The unwanted sludge is separated and then the water can be thrown back to the sea. The running cost of such systems are very low especially when the gas generated by the main engines are used.In cases where this would not be possible such as cases were the volume of inert gas is used for other purposes, an additional inert gas generator can be installed these devices can work on various fuels and are very compact as they house scrubbers incorporated in their design, which are designed to work and leave a minimum footprint on the environment such as those designed and manufactured by Cold Harbour Marine. These inert gas generators are very well controlled to ensure a complete combustion this is to be both efficient and environmentally friendly.5.2.2 Reducing the cost per treatmentThe tests were run at a constant pressure (3bar). If time is in favour, the test would be conducted at lower pressures as to determine the minimum threshold pressure at which the execution of these alien species would have been accomplished. In addition, higher pressure test would be conducted as to induce further the cavitating effect and may result in achieving the same result in very little time. These tests would establish the minimum inert gas required for a complete effective test. The actual treatment system would work on the inert gas generated in the exhaust of the vessel main engine, which was primarily going to waste. The exhaust would then go through a scrubber which cleans of any solid particles. In some cases, inert gas generators would be installed to produce the gas required. In this case it is vital to determine the minimum threshold inert gas required to reduce the operating cost.5.2.2 Testing on a wider range of speciesAs described in the methodology the test was limited to 3 plankton species and bacteria living in salt and brackish water. The world of aquatic organism is spread over thousands of species, each having their own characteristics and strength which enables them to live in harsh environment and may prove difficult to execute. However, it is vital that the treatment is tested on wide range of organisms including but not limited on Jelly fish (e.g. North American Comb), Lion fish and viruses and bacteria (e.g. E. coli). It is also appropriate to consider fresh water species as vessels travel and carry ballast water from canals and rivers which contain treacherous species.5.2.4 Treatment analyseThe treatment samples are to be tested with replicates, as well as achieving the resultant data by other methods such as coliform test, or other methods which will verify the effective reduction in the bacteria or viruses but as well as knowing the kind of species was affected. Although the test conducted gave out the count in the reduction of bacteria it was not specific on the type of bacteria.5.2.5 Other applications The need of treatment of water is found in countless areas and fields. One of these would be the treatment of sewage. It could be treated through the same method, the sewage plant could be built close to power plants, were 24 hours a day all year round would throw to atmosphere tons of these inert gas which could be used for the treatment of sewage. Which simultaneously will reduce the power running cost of sewage treatment. 6.0 Gantt Chart7.0 ReferencesBooks and ArticlesAtilla Incecik., 2014. Ocean EngineeringMedeline Baer, 1996. Stemming the TideMartin Chaplin, C. B., 1990. Enzyme TechnologyPrince William Sound Regional Citizens’ Advisory Council 2005. BALLAST WATER TREATMENT METHODS. Prince William Sound Regional Citizens’ Advisory Council. 2005. Electric Field Technology. BALLAST WATER TREATMENT METHODS.Turner, R., 2015. Coastal Zones Ecosystem Services: From Science to Values and Decision MakingWisconsin Department of Natural Resources, 2007. BALLAST WATER TREATMENT ON-SHOREOnline websitesAnon., 2017. NK. Online viewed November 2017Available at: http://www.nkcf.com/business/environment/ballast-water-treatment-system/bwts/?ckattempt=1 Anon., 2017. wartsila. Online viewed January 2018Available at: https://www.wartsila.com/encyclopedia/term/ballast-water-exchange-at-seaBruno, P., 2017. ThoughtCo. Online viewed November 2017Available at: https://www.thoughtco.com/what-is-ballast-water-2293103Corrina Chase, a., n.d. MARINE BIOINVASIONSCorrina Chase, C. R. a., n.d. BALLAST WATER TREATMENT OPTIONS. Deidun, Alan, 2017. New alien fish species found in Maltese and Mediterranean waters. Heraeus, 2017. Heraeus Noblelight. Online viewed December 2017Available at: https://www.heraeus.com/en/hng/industries_and_applications/uv_technology/uv_ballast_water_treatment.aspxKalinbacak, E., 2015. Treating ships’ ballast water: filtration preferable to disinfection. Phys.org 2003 – 2017, Science X network.Lloyd’s, 2012. Ballast water treatment technologies. Lloyd’s Register’s.Laursen, W., 2016. Maritime, I., 2013. Online Available at: http://www.filtersafe.net/Filtersafe/userdata/SendFile.asp?DBID=1;LNGID=1;GID=539Marshall, A., n.d. cold harbour marine. Online viewed Deceamber 2017Available at: https://www.coldharbourmarine.com/bwt-challenges-story Marex., 2017. maritime-executive. Online viewed November 2017Available at: https://www.maritime-executive.com/article/ballast-water-convention-to-enter-into-force-in-2017SE, G. L., 2013. Online viewed February 2018Available at: http://rules.dnvgl.com/docs/pdf/gl/maritimerules2016July/gl_vi-11-10_e.pdfRanveig Ottoey Olsen, a., 2015. Ultraviolet radiation as a ballast water treatment strategy: Inactivation of phytoplankton measured with flow cytometry. Marine Pollution Bulletin.Thomas, A., 2016. Online viewed December 2017Available at: http://archive.iwlearn.net/globallast.imo.org/globallast.imo.org/wp-content/uploads/2015/03/Bahamas-National-BWM-Strategy-2016.pdfWWF, n.d. Online viewed January 2018Available at: http://wwf.panda.org/about_our_earth/blue_planet/problems/shipping/alien_invaders/ Photos and DiagramsFigure 1 http://engineeringatsea.skf.com/ultrasound-is-ultra-clean/ Figure 2 http://www.bsh.de/en/Marine_data/Observations/MURSYS_reporting_system/mursys501.jspFigure 3 https://www.pbs.org/newshour/features/lionfish/Figure 4 http://www.tugmalta.com/gallery/gallery-detail/oil-rigs Figure 5 https://www.tvm.com.mt/en/news/tinstab-huta-new-alinew-alien-fish-species-found- e in-maltese-and-mediterranean-watersen-fish-species-found-in-maltese-and- e mediterranean-seas-gdida-fl-ibhra-maltin-u-l-mediterran/Figure 6 http://www.hyfluxmembranes.com/products-and-systems/floating-desalination- 3 production-vessel-fdpv Figure 7 https://invasions.si.edu/nbic/managementpract.html7Figure 8 http://www.nepia.com/insights/ballast-water-management/the-challenges/Figure 9 https://www.coldharbourmarine.com/ballast-water-treatment