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NWSCCD Tests New Procedure, Helps USS George H.W. Bush

Navy News Service

Story Number: NNS140516-09
Release Date: 5/16/2014 9:47:00 AM

From Naval Sea Systems Command

WEST BETHESDA, Maryland (NNS) -- A team of engineers and scientists at Naval Surface Warfare Center, Carderock Division (NSWCCD) have developed a new cost-saving procedure to remove oily waste foulants from ceramic membranes on ships, decreasing the number of times the membranes need to be replaced.

The procedure was tested and found successful in April on aboard the aircraft carrier USS George H. W. Bush (CVN 77), during broader efforts to repair and recertify the oil pollution abatement system prior to and during the ship's FY 2014 deployment.

The 50-GPM oily waste membrane system (OWMS) uses ceramic membranes to clean and separate water (permeate) from oily wastewater. The membranes have small molecular openings in their walls (pores), which allow particles less than five nanometers (such as water molecules) to pass through. The molecules of foulants (such as oil molecules) in the oily wastewater are typically larger than these pores and are prevented from passing. These foulants can clog the pores over time and restrict membrane throughput, a condition known as fouling.

The system's membranes require maintenance or replacement once its flow rate has decreased by 50 percent from its original rate or when its hydraulic parameter declines. The oily waste membrane system aboard the carrier had 15 ceramic membranes that were believed to have been fouled and required replacement.

The Environmental Quality Division (EDP) procedure chemically recovers the membranes' hydraulic performance through the use of an alkaline chemical cleaner that removes foulants from the membranes' pores. Regeneration has the potential to save significant costs for the Navy during a ship's life cycle by decreasing the number of times the membranes need to be replaced.

'The Environmental Quality Division at Carderock has chemically restored the hydraulic performance of the oily waste membrane system's 15 ceramic membranes to levels experienced by new, clean membranes, enabling them to postpone the requirement for membrane replacement,' NSWCCD Lead Engineer Syed Shamim said.
Subsequent operational tests were performed on the oily waste membrane system aboard the ship after regeneration. These tests indicated the hydraulic performance was restored. Among the OWMS's hydraulic parameters, the permeate flow rate was also restored to the OWMS's maximum rated flow.

'We are pleased that we could have a positive impact on CVN 77's ability to process wastewater during their deployment while also helping to protect the environment,' said NSWCCD Wastewater Management Branch Head Stephan Verosto. 'The Environmental Quality Division will continue to work on improvements not only on the treatment systems themselves, but also on the maintenance procedures that are used on our wastewater systems, including the novel regeneration procedure used aboard CVN 77.'