Comments, Safurday, May 22, 1999

Mr. Earl B. White is a project engineer in the Wastewater Management Branch, Environmental Quality Department at the Naval Surface Warfare Centq Carderock Division. He is a member ofthe Liquid Waste Thermal Destruction Team that refurbished and upgraded the vortex incinerators on a SPRU- ANCE Class Destroyer He also supports the EDM Facility that is being used to develop and evaluate upgrades to the vortex incinerators. He earned a ms te r of science degree from Catholic University and a bachelor of science degree in mechanical engi- neering from Howard University.

Mark Pechulis began working for the Environmental Quality Department of the Naval Surface Warfare Centel: Carderock Division, in 1996. Since that time he has served as a project engineer p e r f i i n g research on U S . N a y sh$board liquid waste incanerators and on the development of a conceptual design of a U S . N a y shipboard plasma arc solid waste thermal destruction device. He received his BSME from Western New England College in 1992 and his MSME from Lehigh University in 1994. Richard W. Garman holds a bachelor of science degree in aerospace engineering and masters of engineering in environ- mental engineeringfrom the University of Maryland in College Park, MD. Mr Garman is current.$ employed as a senior mechanical engineer with Analysis and Technology (A&T) En@- neering Technologies, VECTOR Research Division, Machinery Systems Department in Annapolis, Maryland. Prior to joining VECTOR Research, Mr Garman workedfor the Naval Surface Warfare Center on the Waste Water Management Branch, Liquid Waste Thermal Destruction Team. A s a member of the Liquid Waste Thermal Destruction Team, Mr Garman worked on ship- board thermal destruction technobgaes relating to the Integrated Liquid Discharge System (ILDS). Mx Garman is a member of the American Geophysical Union (AGU).

Blackwater and Graywater on U.S. Navy Ships: Technical Challenges and Solutions John Benson, Ivan Caplan, and Rachel Jacobs Abstract In anticipation of more stringent environmental regula- tions, the increasing costs of waste disposal, and the need for naval combatants to operate unimpeded in littoral waters, the U.S. Navy has idenbfied the need to develop technologies which are appropriate for the control and treatment of blackwater and graywater. This paper will describe the status of development efforts by the Carder- ock Division, Naval Surface Warfare Center (CDNSWC) and its supporting contractors, under sponsorship of Naval Sea Systems Command (NAVSEA) and the Office of Naval Research. The challenge was to develop treatment sys- tems that meet Navy shipboard requirements for afforda- bility, compactness, low manning/maintenance, high relia- bility and safety, and EM, noise, vibration and shock. Membrane ultrafiltration based systems, incorporating aerobic biological pre-treatment and ultraviolet light post- treatment disinfection, have been developed to meet these requirements. Both external and in-tank membrane sys-

tems will be described in terms of performance, system operation, and space and weight advantages.

COMMENTS BY

Anthrmy Nickens I would k e to congratulate the authors and their team at the Naval Surface Warfare Center Carderock for the crea- tivity, technical skill, and perseverance they have brought to bear on trying to solve one of the Fleet’s most techni- cally challenging environmental problems. The tremendous volumes of blackwater and graywater that are generated on surface combatants must be addressed by holdmg, treatment, or some combination thereof in discharge-re- stricted waters. As we have seen, holdmg liquid wastes occupies valuable space, and to make matters worse, land- based wastewater treatment systems cannot be simply carried into a warship and bolted down. Experience shows that we need a Navy solution that meets Navy technical requirements at minimal life-cycle cost. The authors have demonstrated a comprehensive understanding of the de- sign, engineering, and operational issues faced by the Fleet in this area, and I believe they are well on the way to providing the Fleet with a shipboard wastewater treat- ment capability for the 21st century.

Blackwater is already regulated in the U.S. and the Navy has invested a considerable amount of money since the 1970s to equip surface ships with tankage to hold blackwater while within three nautical miles (nm) of shore. A proposed new Annex under the international MARPOL convention will also regulate blackwater, extending the no- discharge zone out to four nm and allowing only treated discharges between four and twelve nm. Navy ships do not have sufficient holdmg capacity or treatment systems to meet these new requirements. Although new-design ships (for example, the LPD 17 class) are being designed for longer holdmg durations, simply holding more and more blackwater is neither a space-efficient nor cost-effective long-term operational strategy for the Fleet.

Graywater has not been traditionally considered a sig- nificant marine environmental issue and our ships are not designed to hold graywater at all. Over the past few years, however, a patchwork of inconsistent state restrictions on graywater discharge has arisen, makmg it difficult for the Navy to decide how to approach graywater management for our ships. In response to this situation, the Navy is working with EPA to create a new regulatory framework under the Uniform National Discharge Standards (UNDS) legislation that will provide consistent performance stan- dards for shipboard control of graywater (as well as for 24 other liquid effluents). This will be to the Navy’s advantage because it WIII apply a national standard to Navy vessels, thereby avoiding the uncertainty of state-specific water quality or discharge regulations. Hopefully, the Navy’s UNDS answer for graywater control will also satisfy emerging international interest in global graywater limits.

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Comments, Saturday, May 22, 1999

You have heard today about graywater and blackwater treatment based on ultrafiltration membranes. Some of you may be aware of the similar membrane ultrafiltration technology that we have developed to polish the effluent from OiVWater Separators on our ships, to ensure that we can consistently meet existing and future oily dis- charge restrictions. This technology is poised for Fleet introduction, initially through the DDG 51 class and is likely to prompt Fleet eagerness to quickly adopt the same basic technology to solve graywater and blackwater dis- charge problems. I do not detract from the hard work and engineering skill of another NSWC Carderock team that successfully developed the oily waste ultrafiltration system when I assure you that non-oily wastewater poses a greater technical challenge. Non-oily wastewater is a more complex waste stream that will require a combination of several processes (biological conditioning, filtration, and disinfection) to meet effluent standards for discharge. Biodegradation, in particular, is an inherently problematic process on a warship, although you should not confuse this aerated bioreactor with the biological treatment systems that have proven so troublesome on the LHA 1 class.

Addressing Navy-unique shipboard pollution problems is all the more challenging in today’s acquisition reform environment, where we must minimize the total ownership cost (TOC) of naval systems and platforms and employ commercial off-the-shelf (COTS) equipment wherever pos- sible. The development of wastewater ultrafiltration treat- ment systems could, in fact, serve as a case study in addressing TOC and COTS requirements. As the authors could only begin to describe, a myriad of performance, size, capacity, operating scenario, maintainability, logis- tics, and other trade-offs are being analyzed to define the optimal solution or solutions for a range of surface ships. This effort also illustrates the practical synergy between the Navy’s S&T and 6.4 demonstratiodvalidation invest- ments that can accelerate the development, qualification, and transition of new environmental systems to our Fleet customers. This synergy can be achieved only when ONR, CNO, and NAVSEA work closely together to coordinate and focus their respective technical objectives and exper- tise.

I will continue to follow the progress of this R&D effort. We have a way to go, but I have previously worked with the authors and am confident that we will inevitably see a family of answers to our emerging graywater problems. The authors offer very encouraging evidence that we can meet the non-oily wastewater challenge and provide the Fleet with wastewater processing systems that will hope- fully make their presence felt by being an integral and invisible part of the ship. Although the authors correctly focus on forward-fit scenarios, I am particularly excited about the prospect of in-tank membranes for a feasible, relatively low-volume, backfit option for existing ships. I know first-hand that our engineers and scientists at NSWCCD Carderock always keep their eyes on the ship

and its crew and on the Navy’s bottom line, as they develop and prove their technologies. It is important for the rest of the Navy and the shipbudding industry to recognize the operational and TOC benefits of environmental systems.

Finally, even while the authors’ time is occupied by remaining technical hurdles, I challenge them to also focus their attention on early transition planning. Given the DD 21 Program’s unique acquisition strategy, I ask the au- thors to address their plans to transition this technology to the DD 21 class platform. For example, what actions are they taking to farmliarize the DD 21 Blue and Gold Teams on their findings and the benefits of this technology? In addition, I ask the authors to also discuss their transi- tion plans for CVN(X), JCC(X), and other future ships.

COMMENTS BY

Rao Tadavarthy

I would like to congratulate the authors and their team members at the Naval Surface Warfare Center Carderock Division, its supporting contractors under sponsorship of Naval Sea Systems Command (NAVSEA) and the Office of Naval Research for their design, engineering, and opera- tional skills in meeting the challenges of one of the Fleet’s most technically vexing environmental problems.

Blackwater and graywater treatment is based on a com- bination of several processes to meet effluent standards for discharge. Graywater and blackwater treatment re- quires a combination of short-term aerobic biological pre- treatment, membrane ultrafiltration, and ultraviolet light post treatment disinfection to meet the technical and reg- ulatory effluent standards for discharge. Short-term aero- bic biological pre-treatment, in particular, is an inherently problematic process on Navy ships and in commercial pro- cesses. Continuous membrane ultrafiltration is an estab- lished and proven technology. The aim of development should be to reduce capital and most importantly, total ownership costs and simplify and scale-up the microfiltra- tion-bioreactor (MBR) process while meeting technical and regulatory requirements.

Based on my background in chemical engineering and several years with the filtration industry, I add the following operating factors for consideration in the development of the MBR process, particularly the membrane filtration process.

Fluxes percent of Continuous Micro Filtration (CMF) Flux refers to flow rate of liquid through a membrane in gallons per minute (gpm) per square meter (m2) per mem- brane. Each module in filtration technology is referred to as an individual membrane. Normal flux for each module refers to Z 5 gpm/m’/membrane (module). Flux percent of CMF refers to the volume of liquid flowing through all the modules based on the total flow rate of all the modules at the time of installation. Initially flux percent of CMF will

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Comments, Saturday, May 22, 1999

be high and start decreasing as the membranes (modules) get plugged. During research, this can be used to deter- mine the replacement or backwash intervals for the mem- branes. In service, this may be instrumental, so the user can gauge the condition and efficiency for maintenance.

Backwash efficiency and backwash intervals of CMF Backwash requirements of modules are determined by pressure difference or time intervals. Normal practice in filtration technology is to set backwash cycles on the pres- sure difference. If the total suspended solids (TSS) in the liquid exiting from the bioreactor is of normal range, the backwash interval of a membrane can be calculated on the time interval. Once again, test and evaluation of the sys- tem during development will help establish performance and maintenance requirements and instrumentation will serve the user.

Cleaning efficiency and intervals Even if membranes are backwashed with air, that wdl not achieve the original performance for the membranes. With increase in the number of backwash cycles based either on the pressure difference or time intervals, the mem- branes may become partially obstructed and flow rates start decreasing. Therefore, membranes need to be cleaned chemically either with caustic or acid solution(s) to remove all the suspended solids not removed during air backwash cycles. The cleaning intervals have to be deter- mined based on the TSS and the number of backwash cycles.

Membrane integrity testing The membrane integrity testing gives automatic feedback of membrane conditions. Membrane integrity testing is required to ensure consistent filtrate quahty Integrity test requires the filtrate side of the sub-module be pressurized with air to 15 psi. At this pressure, air cannot overcome the membrane’s bubble point, except for a small amount of air that flows through diffusion. The rate of pressure decay is measured over a interval time. If this rate is 10% the cell integrity is intact. If it is over a threshold value, it indicates that membrane integrity is suspect. Damaged fibers can be repaired through pinning.

Navy-unique shipboard pollution problems are more challenging than ever and the technical development of treatment technology for combined shipboard graywater and blackwater must be a high technical priority To mini- mize the total ownership costs (TOC) of naval systems and platforms, commercial off-the-shelf (COTS) equipment and minimum maintenance requirements are crucial.

AUTHOR‘S RESPONSE

Response to A. Nickens: We appreciate your comments and recommendations

as well as your insight to what must be done to ensure that the project succeeds: we accept your challenge to focus on early transition planning amidst the many tech- nical hurdles we face. The Carderock Division, Naval Sur- face Warfare Center and our sponsors have met with rep- resentatives of both DD 21 Teams to discuss these treatment technologies and the benefits and current de- velopmental status. CDNSWC has also participated in a CVN 77 Integrated Product Team that addressed how CVN 77 should be configured to minimize waste genera- tion and achieve compliance.

As the treatment processes mature, NSWC and our sponsors will continue to meet with these Program offices to keep them informed of our R&D efforts and the benefits (operational and TOC) of the these systems. It is our expectation that these systems will be inserted on these platforms, if not the first hulls. Response to Mr. Tadvarthy:

You have touched on some of the key process param- eters that we are evaluating at this time and appreciate having received your insight and recommendations. I agree that the parameters such as backwash efficiency and intervals must be determined empirically by the R&D process and may be Merent for each shipboard treatment system. This is due to the large variances in shipboard wastewater characteristics and system operating cycles. Fortunately, the control system wdl be able to make the necessary adjustments to these process cycles to keep each treatment system operating at peak capacity

The membrane integrity testing mentioned is one we will be investigating in the near future. The integrity test must be appropriate for the membrane geometry and pore size ultimately chosen for the shipboard treatment system. It also must be readily setup and conducted by the many Intermediate Maintenance Activities that could be respon- sible for the upkeep of these treatment systems. Mr. Tad- varthy’s comments on this topic are important in that they highlight the fact that the process of checkmg membrane integrity does not occur just during installation but throughout the useful life of the membrane.

Regardmg Mr. Tadvarthy’s comments on fluxes percent of CME we have taken a similar but different approach. We also consider the applied pressure in the calculation of flux. This results in a term known as resistance. The optimum membrane flux for a treatment system is one that minimizes the rate at which the membrane resistance increases. If resistance increases at a high rate, then the membrane-cleaning interval will be unacceptably short.

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