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EP-4737402-A2 - BALLAST WATER MANAGEMENT SYSTEM

EP4737402A2EP 4737402 A2EP4737402 A2EP 4737402A2EP-4737402-A2

Abstract

Techniques and systems for neutralizing discharge waters from ballast and/or cooling water biocidal treatment and disinfection systems are provided. The systems utilize, inter alia, oxidation reduction potential control to regulate the dechlorination of an electrocatalytically generated biocidal agent to allowable discharge levels in ship buoyancy systems and ship cooling water systems

Inventors

  • NUPNAU, LARS
  • ROGERS, PETER G.

Assignees

  • Evoqua Water Technologies Limited

Dates

Publication Date
20260506
Application Date
20171130

Claims (4)

  1. A ballast water management (BWM) system fluidly connectable to a ballast tank of a ship, comprising: a chlorination system comprising an electrolyzer configured to generate a chlorine-based biocide to be introduced into ballast water; a first controller configured to regulate operation of the electrolyzer; a dechlorination system fluidly connected downstream from the ballast tank, the dechlorination system comprising a source of neutralizing agent selected to reduce the chlorine-based biocide in ballast water to be discharged from the ship; an oxidation-reduction potential (ORP) sensor configured to determine an ORP value of the ballast water to be discharged; a second controller configured to regulate addition of the neutralizing agent to the ballast water to be discharged in at least one of a first dechlorination mode, and a second dechlorination mode, wherein the second controller regulates addition of the neutralizing agent in the first dechlorination mode if the ORP value of the ballast water to be discharged is less than a target ORP value, wherein the second controller regulates addition of the neutralizing agent in the second dechlorination mode if the ORP value of the ballast water to be discharged is greater than or equal to the target ORP value.
  2. The BWM system of claim 1, wherein the target ORP value is less than about 200 mV.
  3. The BWM system of claim 2, wherein the dechlorination system further comprises a second ORP sensor configured to determine an ORP value of the ballast water downstream from a point of introduction of the neutralizing agent into the ballast water to be discharged and wherein the second controller is further configured to regulate addition of the neutralizing agent to a high target dechlorination concentration of neutralizing agent in the ballast water to be discharged if the downstream ORP value measured by the second ORP sensor is greater than the target ORP value.
  4. The BWM system of claim 3, comprising an integrated control system including the first controller and the second controller.

Description

Cross-Reference to Related Application This disclosure claims the benefit of U.S. Patent Application No. 62/427873, titled VARIATION OF OPERATION FOR SEACURE BALLAST WATER TREATMENT SYSTEM, filed on November 30, 2016, which is incorporated herein by reference in its entirety for all purposes. Field This disclosure relates to ship buoyancy disinfection and biofouling treatment systems and techniques and, in particular, to utilizing oxidation reduction potential values and retention duration to inhibit biological activity and to regulate the neutralization of electrocatalytically generated chlorine-based oxidizing agents or biocides. Related Art Chlorine-based disinfection systems can utilize chlorine gas, bulk sodium hypochlorite, and in-situ generated chlorine or sodium hypochlorite electrolytic generators. The electrolysis of seawater to produce chlorine has been used for biofouling control of cooling systems, such as systems that utilize seawater as a coolant. Further, the development of self-cleaning tube-in-tube electrochemical cells has resulted in use of electrochlorination in shipboard applications, such as for biofouling control of engine cooling system, and air conditioning and other auxiliary systems. A typical system layout for a land-based electrochlorination system is schematically presented in FIG. 1. Chloride-containing water, such as seawater, is retrieved from a source 1 and pumped by a pump 2 through an electrolytic generator 3 whereat a chlorine-based biocidal agent or biocide can be generated. The outlet of the electrolytic generator 3 containing the biocidal agent is optionally delivered into a storage tank 5. A power supply 4 provides electrical current to the electrolytic generator 3 to effect generation of the chlorine-based biocidal agent. Storage tank 5 is typically equipped with one or more air blowers 6 that provide dilution or dispersion of a hydrogen gas by-product to a safe concentration. Hydrogen gas removal can be effected with hydrocyclones instead of or in addition to the air blowers and tanks. One or more dosing pumps 7 can be utilized to dose the biocidal agent to a point of use typically by way of a distribution device 8. The point of use is typically an intake basin which provides water to another process such as, but not limited to, a cooling loop 9. In some applications, dechlorination systems (not shown) may utilize a neutralizing agent for downstream treatment of the cooling water, prior to discharge thereof. Land-based systems can produce hypochlorite solutions at relatively high concentrations, e.g., in a range of about 500 ppm to 2,000 ppm chlorine. Ships use ballast water tanks to provide stability and maneuverability. Typically, ballast tanks are filled with water at one port after or during cargo unloading operations. The ballast water then may be discharged at another port during cargo loading operations. Effectively, ballast water could be transferred from the first port to the second port, with a potential for the introduction of aquatic nuisance species (ANS) at the second port, which can be a detrimental ecological issue. Shipboard ballast water management (BWM) systems may utilize electrochlorination systems, such the system exemplarily schematically illustrated in FIG. 2, to reduce or inhibit biological activity of ANS in the ballast water. Typically, BWM systems are configured for low chlorine output with direct injection of chlorinated water, e.g., containing a chlorine-based biocide. In shipboard systems, seawater is typically delivered from a source, such as a sea chest 1 using a booster pump 2 to an electrolytic generator 3 which is typically powered by a power supply 4 to generate the chlorine-based biocide. A product stream containing the biocide from electrolytic generator 3 is typically injected into sea chest 1 through a distribution device 8. Water can be discharged outboard D. Typically, a chlorine concentration analyzer (not shown) is utilized to monitor and maintain a concentration of residual chlorine. Such systems, however, do not consider variabilities in chlorine demand in different ports where ballasting operations may occur. For example, chlorine demand may be affected by the concentration of nitrogen compounds in seawater, which may vary significantly from port to port and from season to season. The fluctuations in chlorine demand can create a higher than desirable or acceptable oxidizer concentration, e.g., high free chlorine concentration, in the various shipboard systems which, in turn can accelerate or promote corrosion of the ship systems and ancillary unit operations, such as but not limited to ballast water pumps, piping, and tanks. Further the variabilities associated with chlorine analyser control schemes can promote undesirable formation of disinfection by-products (DBP). Summary One or more aspects of the disclosure can be directed to a ballast water management (BWM) system of a ship. The BWM system can be configured to