This SERDP and ESTCP webinar highlights results on improving waste reduction and treatment in Armed Forces vessels. Specifically, investigators will present results on new efforts to better understand emulsions in shipboard bilgewater. Two SERDP investigators present different approaches to better characterizing these emulsions so that waste reduction and treatment can be improved on Armed Forces ships.
“Characterizing Shipboard Bilgewater Emulsions Using Macro- and Micro-Scale Flows”
Dr. Cari Dutcher, associate professor of mechanical engineering, chemical engineering, and materials science at the University of Minnesota, Twin Cities.
Bilgewater is oily emulsified wastewater found the in the lower chambers of ships. Prior to discharge overboard into open waters, the oil content in these chemically stabilized oil-in-water emulsions must be reduced to below 15 parts per million. To aid in meeting this standard, our work in this SERDP effort seeks to improve fundamental understanding of the shipboard emulsion stabilization and destabilization processes, with emphasis on emulsion dynamics at length and time scales relevant to bilgewater systems. On the microscale, droplets with varied chemical compositions are generated in a microfluidic device and subjected to flow fields that enable measurements of key properties influencing emulsion stability and destabilization. On the macroscale, we use both rotational rheometry and Taylor-Couette flow to study shearing and mixing conditions on simulated bilgewater emulsion stability. This presentation will highlight results to date; the results enable improved on-board treatment strategies to increase the volume of water that can be discharged overboard.
“Emulsion Characterization Study for Improved Bilgewater Treatment and Management”
Ms. Danielle Paynter, chemical engineer in the Naval Surface Warfare Center, Carderock Division’s (NSWCCD) EnvironmentalEngineering, Science, and Technology Branch in Bethesda, Maryland.
Bilgewater generated aboard Armed Forces’ vessels is typically comprised of oil, water, and surfactants, which can form oil-in-water emulsions.To date, bilgewater treatment methods have followed an Edisonian approach in which an oil-water separator is tested against a set of treatment performance criteria rather than investigating the genesis of emulsion formation in relation to the solution’s composition. The primary objective of this SERDP effort is to understand the physical, chemical, and thermodynamic properties of the emulsions generated in Armed Forces vessels. In this presentation, we will discuss results from the project, including identification and characterization of commercial-off-the-shelf (COTS) detergents from the U.S. Navy procurement data which was used to develop a model emulsion similar to what may be found on a Navy vessel. Using this model emulsion, we explored emulsion stability as a function of surfactant concentration, homogenization speed, pH, temperature, salinity, and suspended solids. A multitude of methods have been employed to describe the stability of prepared emulsions including oil-layer height, bulk-phase oil, and droplet size distribution. The structure-property relationship of the COTS detergents will be presented alongside the characterization of extracted bilgewater samples.