Ask De Nora

No one has all the answers but at De Nora we strive to have the answers you are looking for. Check our frequently asked questions below and if you do not find the answer you need, submit it to us and we will get you an answer!

What are the limitation of the Hyde GUARDIAN treatment system? Specifically, what are the known limitations to water quality for the system to be able to properly treat ballast water (i.e. salinity, temperature, UV-T)? It is well known that UV systems have limitations when operating in water with low UV transmittance.

The Hyde GUARDIAN control system constantly measures the UV light intensity at a fixed point in the reactor. The measured intensity at this point is then used to determine the amount of UV energy applied in the chamber (UV dose) relative to the UV dose that was applied during our type approval testing. The UV intensity sensor reacts to variations in lamp output, sleeve fouling, and water quality parameters. If the applied UV dose drops below the approved, minimum value, a lamp sleeve cleaning cycle is initiated to restore requisite treatment. If the UV dose still remains below the tested value, the lamp output is increased. If neither of these steps increases the UV dose sufficiently, the system automatically slows the flow through the chamber to increase the delivered dose. Once the valve closes to a minimum flow level and if the minimum dose cannot be achieved, a Low UV Intensity alarm sounds alerting the operator that the applied UV dose in the chamber is below the minimum dose allowed. There is no specific water quality standard for the performance of the Hyde GUARDIAN as many different factors (post-filtration turbidity and UVT, sleeve fouling, lamp age, power parameters, etc) contribute to determine the delivery of UV dose. Fortunately, the measurement of the UV intensity accounts for all of these factors dynamically. For medium pressure UV lamps, due to their high operating temperature, there is no change in performance due to water temperature. Finally, since UV treatment is predicated strictly on dose delivery, there is no change in performance due to salinity levels.

It seems that UV systems that are testing now or recently are providing greater detail regarding parameters like ultraviolet transmission and are also reporting biological results based on multiple test methods when compared to systems tested 3 - 6 years ago. Have the G8 requirements changed?

No, the G8 test requirements have not changed. What has changed in the last five to seven years is that test facilities are doing a better job reporting critical variables encountered during testing and manufacturers are doing more detailed boundary testing of their systems. Boundary testing is designed to determine the outer limits of system performance in order to deal with difficult water treatment conditions. Hyde Marine has extensive experience with onboard systems and we have found that our very conservative approach to treatment is the best for reliable operation onboard vessels. Specifying a range of raw water UVT does not contribute to operational reliability for multiple reasons. First, vessel operators do not have a reliable way to measure the water UVT and it is the post-filtration UVT that matters anyway. Second, UVT is only one factor of many that affects UV dose delivery. Using an intensity sensor to verify irradiance at a known point in the reactors allows Hyde Marine to comprehend all of the factors of UV dose delivery in the ballast water stream. Finally, our five-year research study into water quality at ports around the world, and the Guardian’s performance in it has shown us that the Hyde Guardian is right sized for the job in a preponderance of cases.

What is Hyde Marine’s current status for U.S. Coast Guard Type Approval testing?

We are proud to announce that as of April 24, the Hyde GUARDIAN Universal Service has achieved U.S. Coast Guard Type Approval! See our current certificate under the “Hyde Marine Approvals” section of the Hyde Marine Academy or download it via the Coast Guard’s website.

What is Hyde Marine’s understanding of the VIDA regulation and the current state of the U.S. Coast Guard’s efforts to allow the use of the MPN assessment methods during Type Approval testing?

Hyde Marine continues to work with the U.S. Coast Guard to provide them with the peer-reviewed data that they need to accept the MPN assessment method during Type Approval testing. Owing to the extended regulatory cycle and the need under VIDA for the U.S. Coast Guard and the U.S. EPA to develop a new regulatory regime in the waters of the United States, we do not expect the MPN issue to impact type approval testing of systems in the near term.

Is Hyde Marine concerned that UV systems will not be acceptable in the United States because the U.S. Coast Guard requires organisms to be “dead” rather than “inactivated” under the Coast Guard Final Rule?

No. Hyde Marine has completed their testing using the stain methodology identified in the U.S. Coast Guard’s Final Rule. While this methodology has resulted in a significant increase in UV power requirements and has impacted the water quality where UV systems operate, UV remains a viable method for treatment for many vessels in U.S. waters.

What does the U.S. Coast Guard type approval mean for my existing Hyde GUARDIAN approved using MPN?

At this time, the U.S. Coast Guard does not allow type approval testing that used the MPN protocol as part of their approval process. While this is a regrettable decision we are continuing to work to satisfy their questions about MPN.

In the mean time, it is very important to consider whether or not your vessel plans to discharge ballast in U.S. waters before considering this as an issue. The vessel in question is a container ship and as such, likely does not deballast in U.S. waters. Provided the vessel only uptakes ballast water in the United States, the U.S. Coast Guard Type Approval is not necessary. Under the U.S. rules, only vessels that discharge ballast into U.S. waters require a U.S. Coast Guard type-approved system.

In the unlikely event that your vessel must discharge ballast within the territorial waters of the United States, your vessel may use your existing Hyde GUARDIAN system under the AMS approval we have already obtained. Nothing in the Coast Guard’s decision has changed our AMS approvals. Once you are ready, or as your AMS approval period ends, you can upgradeable your current generation Hyde GUARDIAN to the current, U.S. Coast Guard type-approved Hyde GUARDIAN Universal Service. Hyde Marine can provide details on the specific upgrade path necessary based on your current equipment. If you have questions about when your AMS period ends, please contact our compliance experts at and we will get you the information you need.

Why do we need a system bypass valve (V5)? Can you monitor all of the other valves that can be used to bypass the system?

The reason we specify a System Bypass valve is to make sure that we have a single valve that bypasses our system that we monitor and alarm when there is an issue. We monitor all of the valves critical to the treatment process (V1, V2, V4 and V5) and log and alarm when V5 is open during ballasting or deballasting. This requirement is also important to consider when you also remember the requirement to automatically bypass the treatment system during an emergency so we have to make sure that we know exactly which valves to open and close to make sure that the system is bypassed and is not interfering with emergency ballasting.
The regulations require two things that are somewhat contradictory: 1) allow automatically bypass during an emergency; and 2) make sure that the system is never bypassed when not in an emergency, and alarm when it is bypassed. Using a single dedicated System Bypass valve allows this to be done. The rest of the valves should be addressed by the crew in their Ballast Water Management Plan.

What is the default mode for the system bypass valve (V5)? When the system is in alarm, does the treatment system bypass itself or shut down?

Hyde Marine recognizes the critical importance of this question. Ultimately, it is up to the Owner to establish the protocol for how the system operates in their Ballast Water Management Plan. During initial start-up Hyde Marine offers the ability to customize bypass operation based on what the Owner requests. The default condition for the Hyde GUARDIAN is to have V5 closed when the system is in standby or in the event of a shutdown. If the Owner would like the system to remain open to allow for continued ballast flow during a shutdown or an alarm condition, the system can be configured to do this. Regardless of programmed function, in an emergency shutdown, V5 will fail open to ensure that the system does not block critical flow in an emergency. It is our opinion that the rules and Convention were specifically written to protect vessel stability and it is our position that vessel stability should be the most important consideration. However, the more critical concern for normal operation is to prevent untreated or partially treated water from bypassing the system. Because of this, we have set our system up to block that flow unless the valve is manually opened, or power us cut to the unit.

Can I use my system in higher flow during deballast / gravity?

No. Each model of Hyde GUARDIAN has a specific TRC (Treatment Rated Capacity) that is listed on our Type Approval certificate. Any violation of the TRC of a system may result in improperly treated water being put into the ballast tanks or overboard.
Additionally, it is important to remember that each treatment system is a system, not a collection of components each rated on a component by component basis. Systems are certified to work in all operating modes and they do not have separate certifications for Ballast or Deballast or Gravity or any other modes. The TRC of your BWMS is the TRC of the system regardless of what mode the system is in. If an Owner wants a Deballast only system or a system that is sized for higher flow rates in deballast mode rather than ballast mode (ie: filter is not sized for deballast flow rates) then this needs to be specifically approved by the vessel’s Flag Administration. Hyde Marine cannot guarantee acceptance of a system like this.

How can you demonstrate that the GUARDIAN will work satisfactorily in a river environment (high levels of silt/mud in suspension) without causing shut downs on high differential pressure.

Hyde Marine arranged to do our comparative filter testing in fresh water at a lake with both extremely high organism counts and with our uptake very close to the silt bottom of the lake to bring in as much silt and mud as possible. The resultant uptake of organisms and TSS greatly exceeded the IMO boundaries for testing and presented a challenge that more than one filter was unable to meet. When we selected the filters for inclusion with our Hyde GUARDIAN Gold and product line, we specifically chose filters that were capable of holding up under these extreme conditions to insure that we would not experience high differential pressure shutdowns and manual cleaning of the filters. After 200 installations, we continue to know we made the right decision.

What does other UV company’s minimum UVI restriction (e.g. >600 W/m2) mean to a ship operator?

This UVI restriction is a restriction based on the measured intensity of light at a certain point inside the UV chamber rather than looking at the UV Transmittance (UV-T) of the water. This UVI is a proxy for UV-T in that as UV-T decreases the measured light at the sensor also reduces, but it is not a direct measurement of the transmittance. All UV systems work by applying a minimum dose. This dose is calculated by multiplying a reactor constant (calculated by computer modeling and verified by testing) times the intensity of UV in the chamber over the flow of water through the chamber. In this calculation, dose can be increased by either increasing intensity or decreasing flow. By using the intensity as the minimum set point and specifying this minimum set point at maximum flow rate, a system has not chosen to allow for reducing flow during low UVT events in the water. With a set Dose as a minimum parameter, they could have theoretically maintained a their dose at lower intensity by varying flow below the maximum allowed on the TA. Without knowing the UVT they tested at to set this minimum intensity, it’s hard for a ship owner to know how much risk this creates, but it does create risk. There is no way to treat lower UVT water with this approval than a level that allows the minimum measured intensity required, which was done at the full rated flow of their chamber.  See our charts in the “Maximum Flow” section of the Hyde Marine Academy for more information on this.

Will my UV system pass a compliance check since the U.S. Coast Guard doesn’t accept viability methods?

Yes. The U.S. Coast Guard Type Approval testing mandates a CMFDA/FDA dual-stain method that does not assess the viability of organisms. This is NOT the same type of test that the USCG will likely use for onboard rapid compliance tests. These rapid compliance tests all utilize various methods of assessing the vitality of any organism that is found in the ballast discharge. Through extensive testing with these companies, Hyde Marine has confirmed that these tests are able to assess the viability of the organisms and are able to provide an accurate assessment of the performance of the installed BWTS.

How should stripping be handled? Can we use local water as the motive water for the eductor as is current practice?

Stripping operations are challenging and should be carefully detailed in the Ballast Water Management Plan. The most common method of stripping is to pull motive water from the sea chest in order to drive an eductor. The issue with this method is that the drive water is local, untreated and is combined with the partially treated ballast water before moving through the system for final treatment prior to discharge overboard. In order to strictly adhere to the BWM Convention and USCG BW Regulations, all ballast water must meet the discharge standard which, if operating in this manner, would be unlikely due to the added untreated drive water. In order to be fully compliant Hyde Marine recommends dedicating a tank, filled via the BWTS, to act as the source of drive water for the eductor. This would ensure that all ballast discharged overboard is fully treated. However, it is expected Port State Control will not be sampling during stripping operations with the understanding that this volume is a very small portion of the total ballast which has been fully treated. If the stripping operations are detailed in the Ballast Water Management Plan which is approved by Class then the vessel should be able to perform stripping operations as historically has been done with local water used to drive the eductor.

Why is should I purchase multiple BWTS, each rated for the capacity of each of my ballast pumps rather than one single system sized for the combined flow rate?

Hyde Marine strongly recommends a single treatment system for each ballast pump for a number of technical reasons:

Redundancy – In the event of failure of the single BWTS, the operator no longer can ballast while remaining in compliance until that unit is fixed.

Piping – The ballast system will necessarily be sized for the flow of two ballast pumps. Should only a single pump be in operation, the piping is now oversized and there is the distinct possibility of air pockets, pressure drops and areas of stagnant flow. These issues are of great concern to a system largely based on full flow through the UV chamber.

Power Consumption – Similar to above, the system will be designed for full flow of two pumps so should only the one be run the unit will be outputting roughly double the necessary power to treat the ballast water.

The chemical injection and electro chlorination systems that have Type Approval don’t have hold time restrictions - does that mean I can ballast and deballast at any time?

No. The systems that are currently Type Approved using either chemical injection or electrochlorination utilize a minimum treatment time rather than a holding time. Since the minimum treatment time is specified by those manufacturers in their system operating manuals, the U.S. Coast Guard did not include this time as a specific system limitation. You will need to consult with these manufacturers directly about the amount of required treatment time prior to discharging and neutralizing your ballast water.