WO2017220659A1

WO2017220659A1 - Ballast water treatment system

Info

Publication number: WO2017220659A1
Application number: PCT/EP2017/065250
Authority: WO
Inventors: Per AARNÆS; David M. EVANGELISTI
Original assignee: Oceansaver As
Priority date: 2016-06-22
Filing date: 2017-06-21
Publication date: 2017-12-28

Abstract

The present invention provides a ballast water treatment system comprising a main ballast water line, a bypass line and a water treatment pipe section, wherein the main ballast water line comprises a first end, a second end, a ballast water pump and a bypass valve, the first end is fluidly connected to a sea chest and the second end is fluidly connected to a ballast tank system and the bypass valve is arranged downstream the ballast water pump; the bypass line comprises a filter unit and is fluidly connected upstream and downstream of the bypass valve; and the water treatment pipe section is arranged downstream the filter unit and comprises a first sampling port, a second sampling port, a first injection port for a disinfectant, a second injection port for a disinfectant neutralizer and a mixing element, the first sampling port is arranged upstream the mixing element, the second sampling port is arranged downstream the mixing element, and the first injection port and the second injection port are arranged such that a disinfectant or a disinfectant neutralizer entering the water treatment pipe section, during use, is mixed with ballast water by the mixing element.

Description

BALLAST WATER TREATMENT SYSTEM

Technical field The present invention relates to the technical field of ballast water treatment, and more particularly to a system for treatment of ballast water, a method for installing such a system and a mixing device for such a system.

Background

Ballast water is water transported by ships in the ballast water tanks or sometimes in other suitable spaces such as in cargo holds or in cargo tanks. It is pumped into the tanks at a water "donor" location to compensate for the changing of centre of gravity as cargo and/or fuel is discharged/consumed and hence to maintain stability. Correct ballasting is essential from a structural port of view and also used for performance reasons in order to ensure proper propeller and rudder immersion, proper bridge view as well as maintaining desired vessel movement and handling characteristics. The ballast water is transported to a water "recipient" location, generally at a port where the vessel is to be loaded with cargo, which is potentially outside the bio-geographic region of that of the ballast water origin. It may then be discharged as cargo is taken on-board. Ballast water may host a range of species including zooplankton, phytoplankton, bacteria and viruses. These may not have natural predators at the port of discharge and may establish and reproduce at the new location causing significant problems for the environment, industry and human health.

In the USA it is already a requirement for vessels to have a ballast water treatment system (BWTS) to treat water and particularly ballast water in order to kill or disable micro-organisms and to reduce or remove other pollutants. Further, the BWM (Ballast Water Management) Convention will shortly enter into force and the requirement of having a BWTS will be practically a global requirement.

The requirement of having a BWTS will affect all oceangoing vessels used in international transport. The vessels include existing vessels, wherein a BWTS must be retrofitted, and new vessels, wherein a BWTS may be installed during

construction.

Various ballast water treatment systems for killing or disabling micro-organisms and for reducing or removing other pollutants, are well known in the art.

A number of BWTS are disclosed in the prior art. Examples of such systems may be found in for instance WO 2008/047084 A2 and WO 2009/060813 Al . Installation of prior art systems is often made more complicated and expensive by requirements such as minimum pipe lengths to obtain the desired effect of the system and inherent space constraints in the vessel, especially when retrofitting a vessel.

The present invention provides a ballast treatment system which alleviates or avoids at least some of the disadvantages of the prior art systems. Further, the BWTS according to the invention is easy to install both in existing vessels, i.e. retrofitting, and in new builds.

Summary of the invention

The present invention is defined in the appended claims and in the following: In a first aspect, the present invention provides a ballast water treatment system comprising a main ballast water line, a bypass line and a water treatment pipe section, wherein

- the main ballast water line comprises a first end, a second end, a ballast water pump and a bypass valve, the first end is fluidly connected to a sea chest and the second end is fluidly connected to a ballast tank system, and the bypass valve is arranged downstream the ballast water pump;

- the bypass line comprises a filter unit and is fluidly connected upstream and downstream of the bypass valve, such that ballast water may be diverted from the main ballast water line and through the bypass line when the bypass valve is closed; and

- the water treatment pipe section is arranged downstream the filter unit and comprises a first sampling port, a second sampling port, a first injection port for a disinfectant, a second injection port for a disinfectant neutralizer and a mixing element;

- the first sampling port is arranged upstream the mixing element;

- the second sampling port is arranged downstream the mixing element;

- and the first injection port and the second injection port are arranged such that a disinfectant or a disinfectant neutralizer entering the water treatment pipe section, during use, is mixed with ballast water by the mixing element.

Alternatively, or additionally, the first injection port and/or the second injection port may be defined as being arranged upstream of, or at, the mixing element. Alternatively, the main ballast water line may be defined as being arranged to provide ballast water from a sea chest to a ballast tank system and comprises a ballast water pump and a bypass valve, the bypass valve is arranged downstream the ballast water pump.

In an embodiment of the ballast water treatment system, the water treatment pipe section is arranged in the main ballast water line (i.e. the water treatment pipe section constitutes a part or section of the main ballast water line. Preferably, the main ballast water line comprises a fail open flow control valve arranged

downstream the water treatment pipe section.

In an embodiment of the ballast water treatment system the first injection port and/or the second injection port is arranged upstream of, or at, the mixing element.

In an embodiment, the ballast water treatment system comprises a de-ballast line fluidly connected to the ballast tank system and to the main ballast water line at a point upstream the water treatment pipe section (i.e. such that the ballast water will pass through the water treatment pipe section for neutralization of remaining disinfectant before discharge overboard), preferably upstream the ballast water pump.

In an embodiment, the ballast water treatment system comprises a de-ballast bypass line fluidly connecting the de-ballast line to the main ballast water line downstream the ballast water pump, such that the ballast water may be discharged overboard by use of gravity.

In yet an embodiment of the ballast water treatment system, the first injection port is fluidly connected to a disinfectant source, preferably the disinfectant source is an electrolytic unit for providing an oxidant disinfectant.

Throughout the present specification and in the following, the term electrolytic unit is intended to encompass any unit for electrolytic production of an oxidant disinfectant, i.e. an electrodialysis or electrolysis unit. The main difference between an electrodialysis unit and an electrolysis unit is that the electrodialysis unit comprises an ion-exchange membrane separating the anode and cathode.

In yet an embodiment, the electrolytic unit is an electrodialysis unit. In yet an embodiment of the ballast water treatment system, the electrolytic unit is fluidly connected to a seawater storage tank, for instance an aft peak tank, such that sea water stored in the seawater storage tank may be used to generate the oxidant disinfectant. This is particularly advantageous when an oceangoing vessel is in waters having a low salinity.

In yet an embodiment of the ballast water treatment system, the electrolytic unit is fluidly connected upstream the first injection port, such that a part (commonly up to 3%) of the ballast water from the sea chest or a seawater storage tank (e.g. the aft peak tank) is provided to the electrolytic unit. Preferably, the water treatment pipe section comprises an outlet port for connection to the electrolytic unit, the outlet port arranged upstream the first injection port.

In yet an embodiment of the ballast water treatment system, the second injection port is fluidly connected to a disinfectant neutralizer source, preferably an oxidant neutralizer source. In yet an embodiment of the ballast water treatment system, the first sampling port and the second sampling port are connected to a monitoring system for measuring an amount/concentration of a disinfectant in a ballast water flow, preferably an amount/concentration of an oxidant disinfectant. Preferably, the first sampling port and the second sampling port are fluidly connected to the monitoring system, but the first sampling port and the second sampling port may alternatively comprise a sensor/probe for measuring the amount/concentration of the disinfectant.

In yet an embodiment of the ballast water treatment system, the monitoring system is fluidly connected to the second injection port for return of a fluid stream sampled from the first and/or the second sampling port.

In yet an embodiment of the ballast water treatment system, the water treatment pipe section is a single pipe element comprising a first end flange and a second end flange. Preferably, the single pipe element is made up of a single continuous pipe unit. Alternatively, the single pipe element comprises multiple assembled pipe subunits, each pipe subunit comprising at least one of the first sampling port, the second sampling port, the first injection port, the second injection port and the mixing element. In yet an embodiment, the ballast water treatment system comprises a ballast water discharge line fluidly connected to the main ballast water line downstream of the water treatment pipe section.

In a second aspect, the present invention provides a ballast water treatment pipe element (i.e. a single pipe element made up of a single continuous pipe unit) comprising a first end flange, a second end flange, a first sampling port, a second sampling port, a first injection port for a disinfectant, a second injection port for a disinfectant neutralizer and a mixing element, wherein the first sampling port and the second sampling port is arranged on opposite sides of the mixing element, and the first injection port and the second injection port are arranged such that a disinfectant or a disinfectant neutralizer entering the ballast water treatment pipe element, during use, is mixed with ballast water by the mixing element.

Alternatively or additionally, the first injection port and/or the second injection port of the ballast water treatment pipe element may be defined as being arranged in the mixing element, or between the mixing element and the first or the second sampling point.

In one embodiment of the ballast water treatment pipe element, the first injection port is arranged between the first sampling port and the mixing element and the second injection port is arranged between the mixing element and the first sampling port or the second sampling port.

In one embodiment, the ballast water treatment pipe element comprises a pressure measurement device arranged between the mixing element and the second end flange, and preferably between the second sampling port and the second end flange. In addition, the ballast water treatment pipe element may also comprise a further pressure measurement device arranged between the first end flange and the mixing element, such that a differential pressure over the ballast water treatment pipe element may easily be calculated. In yet an embodiment, the ballast water treatment pipe element comprises an outlet port for connection to an inlet of an electrolytic unit, the outlet port arranged between the first end flange and the first injection port (i.e. such that a part of a ballast water flow entering the ballast water treatment pipe may be diverted to an electrolytic unit).

In embodiments of the first and the second aspect, the mixing element is a static mixing element comprising inclined vanes, plates or baffles arranged to impart multiple directional changes and divisions to a ballast water flow. The mixing element may in some embodiments comprise the first injection port and/or the second injection port, such that a disinfectant or a disinfectant neutralizer may be injected directly into the mixing element.

In a third aspect, the present invention provides a method of installing a ballast water treatment system according to the first aspect in a vessel having a main ballast water line, the method comprises the steps of:

replacing a section of the main ballast water line with a water treatment pipe element according to the second aspect; connecting the first sampling port and the second sampling port to a monitoring system for measuring the amount/concentration of a disinfectant;

fluidly connecting the first injection port to a source of disinfectant; and - fluidly connecting the second injection port to a source of disinfectant neutralizer.

In one embodiment, the method comprises a step of installing a bypass line on the main ballast water line, such that water may be diverted from the main ballast water line and through the bypass line, the bypass line is arranged upstream the ballast water treatment pipe element and comprises a filter unit, such that the ballast water is filtered before being returned to the main ballast water line upstream the ballast water treatment pipe element. Alternatively, the method according to the third aspect may be defined as a method of retrofitting a ballast water treatment system to a vessel having a main ballast water line.

Short description of the drawings

The present invention is described in detail by reference to the following drawings: Fig. 1 is a schematic drawing of a prior art ballast water treatment system (BWTS).

Fig. 2 is a schematic drawing of a first embodiment of a BWTS according to the invention. Fig. 3 is a schematic drawing of a second embodiment of a BWTS according to the invention.

Fig. 4 is a drawing of a water treatment pipe element according to the invention.

Detailed description of the invention

To better explain the many advantages of the present invention a prior art system is described by reference to fig. 1.

The present invention is described in detail by reference to the schematic drawings of embodiments of the invention shown in figs. 2-4. The same reference numbers are used throughout the description for corresponding features and devices. The prior art BWTS in fig. 1 comprises a main ballast water line 1, having a first end 4 and a second end 5, arranged to transfer seawater from the sea chest 8 to the ballast tank system 9. A bypass valve 7 and a ballast water pump 6 are arranged in the main ballast water line. A bypass line 2 is fluidly connected upstream and downstream of the bypass valve 7. During ballasting, the ballast water flow is passed through the bypass line 2. The bypass line 2 comprises, successively in a downstream direction, a filter unit 10, a flow meter 28, a first injection port 13, a second sampling port 12 and a flow control valve 30. An outlet of the

electrodialysis unit 18 is fluidly connected to the first injection port 13 for providing an oxidant disinfectant, such as hypochlorite, to the ballast water. In this particular example, the inlet (not shown) of the electrodialysis unit is connected to receive a minor part of the untreated ballast water for producing the required oxidant disinfectant, as described in for instance WO 2008/047084. The second sampling port 12 is connected to the monitoring unit 20 for detecting the total residual oxidant (TRO) in the ballast water. By controlling the amount of oxidant in the ballast water exiting the bypass line 2 and subsequently entering the ballast tank system 9, a sufficient disinfection of the ballast water is ensured. The pipe length between the first injection port and the second sampling port 12 is minimum 3 meters to ensure a homogenous mixing of ballast water and disinfectant. These pipe lengths contribute to an extensive bypass line having a significant space

requirement.

For de-ballasting, a de-ballast line 16 is fluidly connected to the ballast water tank system 9 and to the main ballast water line 1 upstream the ballast water pump 6. A gravity bypass line 17 is arranged between the de-ballast line and the main ballast water line downstream the water pump. During de-ballasting the valve 7 is open such that the ballast water will bypass the bypass line 2 to reach the ballast water discharge line 21. A second injection port 14 is arranged in the main ballast water line 1 upstream of the bypass line 2. The second injection port is fluidly connected to an oxidant neutralizer source 19. A second sampling port 1 1 is arranged in the main ballast water line and connected to the monitoring system for detecting TRO in the ballast water to be discharged overboard. Based on the measured TRO a calculated amount of oxidant neutralizer is injected to the ballast water. A third sampling port 29 is arranged in the ballast water discharge line 21 to monitor that the discharged ballast water is free of oxidant disinfectant. Due to inefficient mixing of ballast water and oxidant neutralizer, the required pipe length between the second injection port and the third sampling port must in this case be at least 10 meters, preferably 15 meters, to allow for a complete neutralization process to occur.

A crossover line 22 is arranged in the main ballast water line upstream the ballast water pump 6. The crossover line may be used for fluidly connecting a second section of the BWTS to the sea chest 8.

A first embodiment of a BWTS according to the invention is shown in fig. 2. The BWTS comprises a main ballast water line 1, having a first end 4 and a second end 5, arranged to transfer seawater from the sea chest 8 to the ballast tank system 9. A bypass valve 7 and a ballast water pump are arranged in the main ballast water line. A bypass line 2 having a filter unit 10 is fluidly connected upstream and

downstream of the bypass valve 7. A flow meter 28 and a pipe section 3 (i.e. a water treatment pipe section) are arranged in the main ballast water line

downstream the bypass line 2. The pipe section 3 comprises, successively in the downstream direction, a first sampling port 11 , a second injection port 14 for a disinfectant neutralizer, a first injection port 13 for a disinfectant, a mixing element 15, a second sampling port 12 and a pressure sensor 27 (i.e. a pressure measurement device, pressure transmitter). The first and the second sampling ports are fluidly connected to the monitoring unit 20 for detecting the total residual oxidant (TRO) in the ballast water. In this specific embodiment, the sampled fluid flow may be returned to the pipe section via the second injection port 14 by the sample discharge line 31. The first injection port 13 is fluidly connected to the electrodialysis unit 18 (i.e. a disinfectant source) arranged to provide an oxidant disinfectant, and the second injection port 14 is fluidly connected to the oxidant neutralizer source 19 (i.e. a disinfectant neutralizer source). The mixing element 15 may be any element suitable for effective mixing of ballast water with a fluid comprising a disinfectant or a disinfectant neutralizer over a short pipe length. Preferably, the mixing element is a static mixing element comprising inclined vanes, plates or baffles arranged to impart multiple directional changes and divisions to the fluid flow. Contrary to the prior art system in fig. 1 , wherein a flow control valve 30 is arranged in the bypass line 2, the system in fig. 2 requires a flow control valve 25 mounted in the main ballast line downstream the pipe section 3. The flow control valve 25 is required to control the flow through the pipe section 3. Since the main ballast water line 1 , in which the pipe section 3 and the flow control valve 25 are arranged, is part of an essential system function the flow control valve 25 is a fail open valve. Further, the flow control valve comprises a manual wheel actuation.

During ballasting, the valve 7 is closed and the ballast water from the sea chest 8 is passed through the bypass line 2 and the filter unit 10. A flow meter 28 measures the flow of ballast water and is arranged in the main ballast water line downstream the bypass line. After passing the flow meter 28, the ballast water enters the pipe section 3. In the pipe section 3, a disinfectant is injected into the ballast water via the first injection port 13, the disinfectant and the ballast water is thoroughly mixed by the mixing element 15 and the TRO is analysed by sampling via the second sampling port. The mixing element 15 removes the requirements of having long pipe lines after the first injection port. The amount of disinfectant is regulated and/or controlled based on the continuous analysis performed by the monitoring system 20 to ensure that the ballast water comprises an excess of disinfectant. The pressure sensor 27 is arranged in the pipe section downstream the mixing element 15. By monitoring the pressure of the ballast water flow, initial clogging of the mixing element 15 may be detected at an early stage. The treated ballast water is then transferred to the ballast water tank system 9.

During de-ballasting, the ballast water to be discharged will flow through the de- ballast line 16 to the main ballast water line 1. The de-ballasting may be performed by use of gravity, via the de-ballast bypass line 17, or via the ballast water pump 6. The valves 32, 33 are closed and the bypass valve 7 is open such that the ballast water is directed through the main ballast water line without passing through the filter unit 10. In both situations, i.e. use of gravity or ballast water pump, the ballast water will pass through the pipe section 3 in the same direction as in the ballasting process. However, during de-ballasting the first sampling port 11 is used to measure the TRO in the ballast water to calculate the amount of oxidant to be neutralized and the second injection port 14 is used to inject an oxidant disinfectant neutralizer (for instance sodium thiosulfate STP). The ballast water and the oxidant disinfectant neutralizer is intimately mixed by the mixing element 15 and the second sampling port is used to measure whether the ballast water has TRO below a given threshold after neutralization. The measurement of the sample from the second sampling port is used to correct the amount of added oxidant disinfectant neutralizer such that the ballast water to be discharged is free of TRO when discharged overboard via the ballast water discharge line 21.

A further embodiment of a BWTS according to the invention is shown in fig. 3. The main difference between the systems in fig. 2 and 3 is the arrangement of the pipe section 3 (i.e. the water treatment pipe section). In the system of fig. 3, the flow meter 28, the pipe section 3 and the flow control valve 30 are arranged in the bypass line 2. Since the flow control valve 30 is not arranged in the main ballast water line 1, a fail open flow control valve 25 as shown in fig. 2 is not required. The pipe section 3 is identical to the pipe section described for fig. 2.

During ballasting, the system of fig. 3 follows the same basic sequence as described for the system of fig. 2. During de-ballasting, contrary to the system of fig. 2, the ballast water will pass through the bypass line 2. The filter unit 10 is bypassed via the filter bypass line 34 and the ballast water is led through the pipe section 3 for neutralization of TRO as described for fig. 2.

Advantageously, see fig. 4, and as shown in the embodiments of figs. 2 and 3, the pipe section 3 is a single pipe element comprising a first end flange 23 and a second end flange 24 for connecting the pipe section into the main ballast water line 1. By combining the first sampling port 1 1, the second injection port 14, the first injection port 13, the mixing element 15, the second sampling port 12 and the pressure sensor 27 in a single pipe element, the present system is easy to install and is particularly suitable for retrofitting a vessel with a BWTS. Due to the mixing element 15 and its use in both the ballasting and the de-ballasting process, the required pipe lengths and space requirements are significantly reduced. Further, the BWTS in figs. 2 and 3 do not require a third sampling point 29 in the ballast water discharge line 21, see fig. 1, due to the effect of the mixing element 15. The pipe section 3 in figs. 2 and 3 may also comprise an outlet port (not shown, see ref. 26 in fig. 4) for providing a part of the ballast water flow to the electrodialysis unit. The BWTS of fig. 2 may be considered particularly advantageous in that the arrangement of the pipe section 3 as part of the main ballast water line 1 ensures that bypass line 2 requires a minimum of space. Especially when retrofitting a vessel this arrangement will be highly time and cost efficient.

In fig. 2, the sampled fluid flow (i.e. a fluid sample which has been analysed in the monitoring unit) is returned to the pipe section via the second injection port 14 by the sample discharge line 31. In other embodiments, the sampled fluid flow may be disposed of in any suitable manner, such as being discharged to the bilge or returned to any position in the system being upstream the first and second injection port.

In all embodiments, the injection ports may comprise at least one injection device, such as a lance or quill, for providing an optimized injection. Preferably, the injection device may comprise multiple nozzles or outlets for obtaining a fluid injection distributed over the transverse cross-section of the pipe section.

The BWTS comprises a number of valves, in addition to the described valves 7, 25, 30, 32 and 33, for controlling the various ballasting and de-ballasting processes. The function and use of all valves are not described as they are considered obvious to the skilled person based on the common general knowledge and the present description. In the embodiments disclosed in figs. 2 and 3, the oxidant disinfectant is an oxidant obtained by electrodialysis of seawater, such as hypochlorite. However, the present invention is equally suitable for use with other types of oxidants such as ozone, chlorine dioxide and chlorine. Instead of an electrodialysis unit, the inventive BWTS may use any suitable source of oxidant disinfectant, such as an ozone generator or a storage tank with a preformed oxidant disinfectant. Examples of suitable electrodialysis units are disclosed in for instance WO 2012/098059. When the BWTS according to the invention comprises an electrodialysis unit, the water treatment pipe section 3 may comprise an outlet port 26, see fig. 4, for connection to the inlet of the electrodialysis unit, the outlet port is arranged upstream the second injection port and is suitable for diverting a fraction (usually up to 3%) of the ballast water to the electrodialysis unit for the production of an oxidant disinfectant. Alternatively, a fraction of the ballast water may be diverted to the electrodialysis unit from any point upstream of the first injection port 13.

The mixing element may be any type of element suitable for distributing a disinfectant or a disinfectant neutralizing agent in the water phase entering the water treatment pipe section. Examples of suitable mixing elements are disclosed in for instance WO 2009/000642 Al , US 2005/0047274 Al, US 4461579 B, WO 2012/095623 Al and US 2012/0134232 Al . Depending on the type of mixing element, the first injection port and/or the second injection port may be arranged upstream of the mixing element, as shown in figs. 2-4, or they may be arranged at the mixing element. In the latter case the first injection port and/or the second injection port are arranged to provide a disinfectant or a disinfectant neutralizing agent directly into the mixing element, not upstream of the mixing element.

In some embodiments (not shown) it is envisioned that the mixing element is equally effective independent of the direction of a fluid flow through the pipe section 3. Consequently, in some embodiments of the system, the second injection port 14 may be arranged on the opposite side of the first injection port 13 relative to the mixing element. In this manner the de-ballasting process may entail passing the ballast water to be discharged through the pipe section in a direction opposite the direction of the ballast water during ballasting.

Claims

A ballast water treatment system comprising a main ballast water line (1), a bypass line (2) and a water treatment pipe section (3), wherein

- the main ballast water line (1) comprises a first end (4), a second end (5), a ballast water pump (6) and a bypass valve (7), the first end is fluidly connected to a sea chest (8) and the second end is fluidly connected to a ballast tank system (9) and the bypass valve is arranged downstream the ballast water pump;

- the bypass line (2) comprises a filter unit (10) and is fluidly connected upstream and downstream of the bypass valve (7); and

- the water treatment pipe section (3) is arranged downstream the filter unit and comprises a first sampling port (11), a second sampling port (12), a first injection port (13) for a disinfectant, a second injection port (14) for a disinfectant neutralizer and a mixing element (15), the first sampling port is arranged upstream the mixing element, the second sampling port is arranged downstream the mixing element, and the first injection port and the second injection port are arranged such that a disinfectant or a disinfectant neutralizer entering the water treatment pipe section (3), during use, is mixed with ballast water by the mixing element (15).

The ballast water treatment system according to claim 1 , wherein the water treatment pipe section (3) is arranged in the main ballast water line (1).

The ballast water treatment system according to claim 2, wherein the main ballast water line comprises a fail open flow control valve (25) arranged downstream the water treatment pipe section (3).

The ballast water treatment system according to any of the claims 1 to 3, wherein the first injection port (13) and/or the second injection port (14) is arranged upstream, or at, the mixing element.

The ballast water treatment system according to any of the preceding claims, comprising a de-ballast line (16) fluidly connected to the ballast tank system (9) and to the main ballast water line upstream the water treatment pipe section (3), preferably upstream the ballast water pump (6).

6. The ballast water treatment system according to claim 5, comprising a de- ballast bypass line (17) fluidly connecting the de-ballast line to the main ballast water line downstream the ballast water pump (6).

7. The ballast water treatment system according to any of the preceding claims, wherein the first injection port (13) is fmidly connected to a disinfectant source (18), preferably the disinfectant source is an electrolytic unit for providing an oxidant disinfectant.

8. The ballast water treatment system according to claim 7, wherein the

electrolytic unit is fmidly connected upstream the first injection port (13), such that a part of the ballast water from the sea chest (8) is provided to the electrolytic unit.

9. The ballast water treatment system according to any of the preceding claims, wherein the second injection port (14) is fmidly connected to a disinfectant neutralizer source (19), preferably an oxidant neutralizer source.

10. The ballast water treatment system according to any of the preceding claims, wherein the first sampling port (11) and the second sampling port (12) are connected to a monitoring system (20) for measuring the concentration of a disinfectant in a ballast water flow, preferably the concentration of an oxidant disinfectant.

11. The ballast water treatment system according to claim 10, wherein the

monitoring system (20) is fmidly connected to the second injection port (14) for return of a fluid stream sampled from the first and/or the second sampling port.

12. The ballast water treatment system according to any of the preceding claims, wherein the water treatment pipe section (3) is a single pipe element comprising a first end flange (23) and a second end flange (24).

13. The ballast water treatment system according to any of the preceding claims comprising a ballast water discharge line (21) fluidly connected to the main ballast water line downstream of the water treatment pipe section (3).

14. A ballast water treatment pipe element (3) comprising a first end flange (23), a second end flange (24), a first sampling port (11), a second sampling port (12), a first injection port (13) for a disinfectant, a second injection port (14) for a disinfectant neutralizer and a mixing element (15), wherein the first sampling port and the second sampling port is arranged on opposite sides of the mixing element, and the first injection port and the second injection port are arranged such that a disinfectant or a disinfectant neutralizer entering the ballast water treatment pipe element (3), during use, is mixed with ballast water by the mixing element (15).

15. The ballast water treatment pipe element according to claim 14, wherein the first injection port is arranged between the first sampling port and the mixing element and the second injection port is arranged between the mixing element and the first sampling port or the second sampling port.

16. A ballast water treatment pipe element according to claim 14 or 15,

comprising a pressure measurement device (27) arranged between the mixing element (15) and the second end flange (24), and preferably between the second sampling port and the second end flange.

17. A ballast water treatment pipe element according to any of the claims 14- 16, comprising an outlet port (26) for connection to an electrolytic unit, the outlet port arranged between the first end flange (23) and the first injection port (13).

18. A method of installing a ballast water treatment system according to any of the claims 1- 13 in a vessel having a main ballast water line (1), the method comprises the steps of:

replacing a section of the main ballast water line with a ballast water treatment pipe element (3) according to any of claims 14 to 17;

connecting the first sampling port and the second sampling port to a monitoring system for measuring the amount/concentration of a disinfectant;

fluidly connecting the first injection port (13) to a source of disinfectant; and

fluidly connecting the second injection port (14) to a source of disinfectant neutralizer.

19. The method according to claim 18, comprising a step of installing a bypass line (2) on the main ballast water line (1), such that water may be diverted from the main ballast water line and through the bypass line, the bypass line is arranged upstream the water treatment pipe element and comprises a filter unit (10).